300 PRC update

navy1942

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Greg at SPR spun up a 28in Bartlein 9 twist on a Defiance Deviant. I am very impressed with the inherent accuracy. Took it to the Talladega CMP yesterday to get the scoped sighted and a catch a few FPS numbers on the LabRadar for the ballistics calculator.
(Side NOTE: even on position 1 and the other shooters 15 positions away, it was rough getting readings. I think there was a sale on AR15's somewhere).

Having accomplished my early goal, I moved to the 600 yard range. to check my calculator and see what a 600 yard group would look like.

I can only say I love this rifle and Thanks to Greg Young @SPR !!! Some pics of the rifle and the target are attached.
 

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wspe1

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Greg at SPR spun up a 28in Bartlein 9 twist on a Defiance Deviant. I am very impressed with the inherent accuracy. Took it to the Talladega CMP yesterday to get the scoped sighted and a catch a few FPS numbers on the LabRadar for the ballistics calculator.
(Side NOTE: even on position 1 and the other shooters 15 positions away, it was rough getting readings. I think there was a sale on AR15's somewhere).

Having accomplished my early goal, I moved to the 600 yard range. to check my calculator and see what a 600 yard group would look like.

I can only say I love this rifle and Thanks to Greg Young @SPR !!! Some pics of the rifle and the target are attached.
Nice shooting. Also nice rifle. What are the specs on the rifle?
 

Harleydog

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Well, local gunsmith was solid enough to just refund my money and take the barreled action back and work on it himself. I have Alamo Precision Rifles making me a new one with defiance tactical action and Bartlein. Should be around 3 wk turnaround! That’s awesome I think and heard great reviews about them.
 

b2lee

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Mine should be in from Greg soon. A little tired of eating Ramen and off brand peanut butter...but I still got to pay for the JAE Chassis so a few more weeks on the old poverty diet and I should be back into store brand hot dogs and maybe even name brand cola.

Priorities man...priorities....it's not like I couldn't afford to lose a few lbs....right?
 

4KDOA

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Picked mine up from Alamo Precision last Thursday. Built on their action with Muller barrel 1-10 twist at 26", Hellfire break and Diamond trigger. Shoots as a custom rifle should. Great! Will be switching to a chassis though. Pretty sure the AG Composite stock is hollow, or close to it. Just want to add about five pounds.

Kendal
 

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navy1942

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Nice shooting. Also nice rifle. What are the specs on the rifle?
300 PRC
1:9 twist 28" Bartlein MTU contour
Defiance Deviant Long Action
Trigger Tech Diamond with straight shoe
AAC Titan brake
AI AX CIP chassis
Vortex Gen2 Razor 27x
Desert Tech 34mm rings with 30MOA slope
Elite Iron Bipod
 

car16smg

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Thought I’d try some PRC KoolAid and see how I like it; so I ordered a new magnum RPR. The brass prep for my MK13 is laborious to say the least, but I wasn’t gonna rebarrel a good shooting 300WM just yet. Hoping to significantly cut down reloading time with this new rifle. I’d love to shave some weight off that 15lb Ruger. Proof is making the barrels, but I can’t find anyone making aftermarket handguards. Was hoping someone could weigh in that has tracked down a company making them. I’m not above installing the 24” Proof and cutting down the factory handguard but will save that option till last 😂
 

jwknutson17

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Report on the Hornady brass..

Consensus is... it's terrible. I'm using a lot of 100 that was factory ammo once fired to start. After 2 loadings, and on a third, I have already thrown out 25 pieces of brass from loose primer pockets. A few of those were from my ladder test finding pressure before I backed down. I will most likely see over half of the brass has too loose of primer pockets to use after this loading. (4 times fired). Most of the loadings were 79.0-79.25 gr of H1k. I see zero pressure with these loads with the 215 berger in this rifle. Also, Neck thickness is not consistent at all. I first noticed this when sizing and my .305 mandrill would be tight on some and just barley scoot by on the inside on others. Using a 335 Redding bushing in a Redding type S custom die. I'm disappointed once again in Hornady brass. I may be just shooting other rifles in the meantime til some other brass comes along. I could drop it down another 75 FPS to 2900 and see if that helps with brass life. But at that point I'll just spin back on the 300 win mag barrel and get 2900 fps with the 215 Berger no problem with H1k and have all the quality brass I need. Lot of time spent and having this brass give way before/at the 4th firing is pretty terrible.

I'm going to shoot these 75 rounds and then most likely stick to factory ammo for the time being or spin back on my 300 win mag barrels and use quality brass for the time being.

I know there is great potential here in the 300 PRC. But the whole brass thing seems like I'm wasting my time right now for not really much gain.

ADG, Peterson, Lapua, if your listening, I need some brass. Please!
 

b6graham

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Report on the Hornady brass..

Consensus is... it's terrible. I'm using a lot of 100 that was factory ammo once fired to start. After 2 loadings, and on a third, I have already thrown out 25 pieces of brass from loose primer pockets. A few of those were from my ladder test finding pressure before I backed down. I will most likely see over half of the brass has too loose of primer pockets to use after this loading. (4 times fired). Most of the loadings were 79.0-79.25 gr of H1k. I see zero pressure with these loads with the 215 berger in this rifle. Also, Neck thickness is not consistent at all. I first noticed this when sizing and my .305 mandrill would be tight on some and just barley scoot by on the inside on others. Using a 335 Redding bushing in a Redding type S custom die. I'm disappointed once again in Hornady brass. I may be just shooting other rifles in the meantime til some other brass comes along. I could drop it down another 75 FPS to 2900 and see if that helps with brass life. But at that point I'll just spin back on the 300 win mag barrel and get 2900 fps with the 215 Berger no problem with H1k and have all the quality brass I need. Lot of time spent and having this brass give way before/at the 4th firing is pretty terrible.

I'm going to shoot these 75 rounds and then most likely stick to factory ammo for the time being or spin back on my 300 win mag barrels and use quality brass for the time being.

I know there is great potential here in the 300 PRC. But the whole brass thing seems like I'm wasting my time right now for not really much gain.

ADG, Peterson, Lapua, if your listening, I need some brass. Please!
curious how many people are waiting for better brass. ADG and peterson already make big stuff that seems to last
 
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jwknutson17

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curious how many people are waiting for better brass. ADG and peterson already make big stuff that seems to last
I figured I would have gotten more honestly.

I have 14 loadings now on ADG brass with a hot 300 win mag load. 7 on another lot for a different gun and still going strong.
 
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gnochi

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I’ve talked to Peterson and ADG, and 300 PRC isn’t on either of their roadmaps for this year. As such I’m planning on buying a bunch of RWS 8x68S brass and resizing.
 
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Ledzep

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I believe you're running around 79-80gr of H1000 under a 215 Jwknutson?

FWIW, max published load data is 78ish gr with the 212 ELDX, and the published load data in my experience follows pretty closely to SAAMI max pressures. I guess what I'm getting at is you can hit 65,000psi and not see any "pressure signs" on your cases, but you are at the upper end of what Hornady/Winchester/Remington etc.. brass will handle.

Lapua and some others have figured out processes that leave the head harder and more resilient to stretching primer pockets, but you're still probably running anywhere from 65,000-75,000psi before you start seeing flat primers, FP hole flow, ejector slot swipes, etc. And to pierce or blow primers you're probably north of 75-80ksi.

Anyway, it's all fair game. I would imagine most guys here that load are exceeding SAAMI pressures, or if they're wildcatting are probably in the 65,000-70,000psi range trying to get as much speed as they can. But all brass will last longer if you back down under 65ksi. Hornady cases will last 10-20+ firings (6.5 SAUM and 6.5 Creedmoor so far, have only got 3 firings on 300 PRC brass yet, but still holding up), Lapua will go 20-40 (.260, .308 that I've done) depending on sizing/annealing cycle etc... Just depends on what 75-100fps is worth to you. That's kind of why I went with a 31" barrel, let the length get the speed so I can run lazy loads and have the stuff last longer. YMMV etc...
 

jwknutson17

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I believe you're running around 79-80gr of H1000 under a 215 Jwknutson?

FWIW, max published load data is 78ish gr with the 212 ELDX, and the published load data in my experience follows pretty closely to SAAMI max pressures. I guess what I'm getting at is you can hit 65,000psi and not see any "pressure signs" on your cases, but you are at the upper end of what Hornady/Winchester/Remington etc.. brass will handle.

Lapua and some others have figured out processes that leave the head harder and more resilient to stretching primer pockets, but you're still probably running anywhere from 65,000-75,000psi before you start seeing flat primers, FP hole flow, ejector slot swipes, etc. And to pierce or blow primers you're probably north of 75-80ksi.

Anyway, it's all fair game. I would imagine most guys here that load are exceeding SAAMI pressures, or if they're wildcatting are probably in the 65,000-70,000psi range trying to get as much speed as they can. But all brass will last longer if you back down under 65ksi. Hornady cases will last 10-20+ firings (6.5 SAUM and 6.5 Creedmoor so far, have only got 3 firings on 300 PRC brass yet, but still holding up), Lapua will go 20-40 (.260, .308 that I've done) depending on sizing/annealing cycle etc... Just depends on what 75-100fps is worth to you. That's kind of why I went with a 31" barrel, let the length get the speed so I can run lazy loads and have the stuff last longer. YMMV etc...
Yea I hear ya. If I'm actually only one grain over their max then I wouldn't think it's "that" hot from my experience. I'm going to give RL26 a go and see if I can get more velocity with longer brass life. I have 24lb on order if it ever comes in stock.

I've loaded stuff hot before, and this isn't there yet at 79.0 and 79.25 in this rifle I don't think. I may just rebarrel it longer if I'm going to be stuck at win mag velocities without sacrificing the brass ever 4 or so loadings. I don't have any extractor or ejector marks. No sticky bolt. And primers look perfect. Figured with all that i would be good to go.
 
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Ledzep

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Yeah, and I suppose I shouldn't rule out the brass. I'll have to report back once I get 5+ firings on mine, how the pockets hold up.
 

nick338

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Report on the Hornady brass..

Consensus is... it's terrible. I'm using a lot of 100 that was factory ammo once fired to start. After 2 loadings, and on a third, I have already thrown out 25 pieces of brass from loose primer pockets. A few of those were from my ladder test finding pressure before I backed down. I will most likely see over half of the brass has too loose of primer pockets to use after this loading. (4 times fired). Most of the loadings were 79.0-79.25 gr of H1k. I see zero pressure with these loads with the 215 berger in this rifle. Also, Neck thickness is not consistent at all. I first noticed this when sizing and my .305 mandrill would be tight on some and just barley scoot by on the inside on others. Using a 335 Redding bushing in a Redding type S custom die. I'm disappointed once again in Hornady brass. I may be just shooting other rifles in the meantime til some other brass comes along. I could drop it down another 75 FPS to 2900 and see if that helps with brass life. But at that point I'll just spin back on the 300 win mag barrel and get 2900 fps with the 215 Berger no problem with H1k and have all the quality brass I need. Lot of time spent and having this brass give way before/at the 4th firing is pretty terrible.

I'm going to shoot these 75 rounds and then most likely stick to factory ammo for the time being or spin back on my 300 win mag barrels and use quality brass for the time being.

I know there is great potential here in the 300 PRC. But the whole brass thing seems like I'm wasting my time right now for not really much gain.

ADG, Peterson, Lapua, if your listening, I need some brass. Please!
Should have said, "Hornady if you're listening get your shit together". Great bullets, great cartridges and the worst brass in the industry. Time to raise the standards to 2019. There are far too many other companies making quality brass for an industry giant to be lagging so far behind.
 

Rocketmandb

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I’ve talked to Peterson and ADG, and 300 PRC isn’t on either of their roadmaps for this year. As such I’m planning on buying a bunch of RWS 8x68S brass and resizing.
Last weekend I ran my first fire formed 8x68S back through the barrel as 300 PRC. The only issue I had was that the pressure was higher (likely due to smaller volume - 75.2 gr of RL26 ran about the same as 75.6+ in Hornady cases. Otherwise, they were sweet, and they cleaned up nicely. I'm going to have to do another round of load development with these.

I also ran 8 more new rounds through to get more fire formed. I took down my Labradar before these rounds (I figured, why use it?), aimed at steel at 850, guess at the bullet drop. With 225 gr @ 2650 fps with 76.2 gr H1000, it was 15.5 MOA. These were 200gr ELDX and 68gr H1000, so I figured I'd try 18. Six o'clock low. Raised to 21 MOA... gong! Next 6 shots landed within an MOA at 850. Again, this was 8x68S, non-fire formed. I literally laughed at every hit.

Here is my process for prepping the brass:

- Size the brass in my 300 PRC die with a .339 bushing (I just ordered a .440 and .441 and will play with those next).
- At this point, all that brass from pushing down/in the shoulder is on the inside of the neck.
- Using my Lyman trimmer and power shank, I use a drill to trim the brass down to my 300 length and chamfer a bit to clean up the outside rim of the neck.
- Using my Forster trimmer and their .308 reamer, I ream out the neck (using my hand to turn, not a drill). If you don't do this, or alternately use an expander to push the neck back out and neck turn, you might have issues chambering the round - and you have to get rid of the extra brass at some point - I FAR prefer the reamer to neck turning, and it gets me very consistent neck thickness.
- I then do final chamfer and deburr and resize the neck using a .335 bushing - this gets me roughly 1 thousandth neck tension. .336 gives none. This is a similar drop when I do this to Hornady brass - initial size is .335, ream, final size is .331 for 1 thousandth NT.
- Finally, I load with 68 gr H1000, 200 gr bullet, and seat the bullet so it's touching the lands.

I'm very happy this is working out. I had to toss 10 Hornady cases during loading for this trip due to loose primer pockets. I've only got about 5 firings on them. I've never used Hornady brass to failure before, so I don't know if that's par for the course, but it's way short of what I'm used to with Norma. There was something oddly satisfying about priming the RWS cases - that extra little umph it takes to press the primer in, and no anxiety about whether it would stay.

EDIT: I might do a video of this.
 

Scrav223

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Oct 24, 2018
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Range report:
Savage 110 rebarreled by Cresent Customs 26" barlien 1:8.5 M40
Manner T-4A
Load testing: 225ELDM
H-1000 77.2 Hornady Brass
Testing primers
10 loads each with GM215M and WLRM

Fired two (3) shot groups each and the GM215 had highest velocity at 2875/Ave and best groups but both primers shot well. Got first round hits at 553yards with 9.75moa Going to do some neck turning and will update.IMG_6805.JPGIMG_6704.JPG
 

b2lee

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Tracking numbers show my barreled action heading to my local FFL...says Monday....but I think it may get delivered today. I may have to swing by after work and pick it up :)
 

TEUFEL820

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Picked mine up from Alamo Precision last Thursday. Built on their action with Muller barrel 1-10 twist at 26", Hellfire break and Diamond trigger. Shoots as a custom rifle should. Great! Will be switching to a chassis though. Pretty sure the AG Composite stock is hollow, or close to it. Just want to add about five pounds.

Kendal
Are you using the Alamo APR Gen 2 action? I've been skeptical compared to an action like Defiance.
 

Ledzep

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The last couple weekends I've been able to get out at range with the 300. Within 800yd it's more or less hitting the "easy" button. There are a few IPSC plates (I think 66% or 75%) with hostage flappers and a center 4" flapper at 707 and 802yd at the local range. With my reloads I can bust the flappers more often than not. I don't shoot it closer than 600 other than to check zero. Pretty consistent results on 12-16" plates at 1000.

I grabbed a few boxes of factory match 225gr and within 1200 it seems to be consistent enough to hit most any of the plate arrays that are on the range.

I tried the factory stuff at 1630 and had some elevation spread that I didn't have with my handloads. Not a ton, but one or two would slide high or low. It took me 3 rounds to get the wind right with my reloads then tagged the 1630 torso 4 times in a row. Later on in the day today (was swapping back and forth between 6.5, .308 and .300) I was also able to get a couple hits on the 24x24" 1850yd square. Wind picked up and was more gusty later on. I think I was 2 for 7 at 1850.

One thing I did notice, because I've tried 1700+ with a 6.5 SAUM, is that you almost always see splash, even way out there. Hits produce a nice big white/grey puff and misses kick up dirt. It rained last night so the ground was wet and I was still seeing all but 1 of my misses.
 

gnochi

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Any sources for headspace gauges? I'm going to swap out my steel barrel for a Proof CF that is arriving next week.
Call up Dave Manson Precision Reamers. Note that 375 Ruger go/nogo are not compatible - that will give you ~.050in extra headspace, which is dangerous.
 
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jwknutson17

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Going to get a chance to stretch the PRC legs on Saturday. Will give the mile and then the 1.5 a go. The 1.5 is outside of the useful range for this gun with the 215s. But we'll see how she does anyway.
 
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nick338

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Going to get a chance to stretch the PRC legs on Saturday. Will give the mile and then the 1.5 a go. The 1.5 is outside of the useful range for this gun with the 215s. But we'll see how she does anyway.
Load up some 250 A-tips when they are released and see it how it does. My rifle is ready to go. I'll be playing with the factory 225 ELD until I can get some 250's loaded up.
 

jwknutson17

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Load up some 250 A-tips when they are released and see it how it does. My rifle is ready to go. I'll be playing with the factory 225 ELD until I can get some 250's loaded up.
I will rebarrel it longer before I get into the 230/250s. Just can't get the 225s fast enough with H1k right at the moment to justify shooting even heavier.

I did just get my 24 lbs of RL26 tracking sent to me today. So there is hope in my future!
 
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camotoe

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I think reloader33 in a 30 or 32inch barrel would be pretty good for this round
 

nick338

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I will rebarrel it longer before I get into the 230/250s. Just can't get the 225s fast enough with H1k right at the moment to justify shooting even heavier.

I did just get my 24 lbs of RL26 tracking sent to me today. So there is hope in my future!
Hornady load tested all their .30 A-Tip bullets with the 300 PRC. Source that I spoke with stated they saw 2700 with the 250 gr so 2750-2800 should be doable depending on barrel length. That equals what a 338 Lapua would see with a 300 gr and the A-Tip has a much better bc. I'm at least going to give it a shot.
 

jwknutson17

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Hornady load tested all their .30 A-Tip bullets with the 300 PRC. Source that I spoke with stated they saw 2700 with the 250 gr so 2750-2800 should be doable depending on barrel length. That equals what a 338 Lapua would see with a 300 gr and the A-Tip has a much better bc. I'm at least going to give it a shot.
Well that sounds promising. I was planning on doing a 28-30" instead of 26 on this one gun. With my 338 ultra TB can and load the A-Tips with that. Keeping my other one a 26 and no plans to change it for now. I think that 250 would be awesome in the Norma mag and would be good to see what others get out of the PRC with it.

Think I'll give the 230s a go eventually in the PRC.
 

SRPowah

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Ok guys... I am giving serious thought to having my 300WM barrel rechambered. It would end up being a 25.5" with a 1/10 twist. I understand the 1/10 will work ok but that leads to my question: when do you NEED to move to a faster barrel with this round?

I will be stuck shooting factory ammo for another year minimum, and preferably the 225 unless the 212 performs that much better out of my rifle.
 

jwknutson17

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Ok guys... I am giving serious thought to having my 300WM barrel rechambered. It would end up being a 25.5" with a 1/10 twist. I understand the 1/10 will work ok but that leads to my question: when do you NEED to move to a faster barrel with this round?

I will be stuck shooting factory ammo for another year minimum, and preferably the 225 unless the 212 performs that much better out of my rifle.
Ok guys... I am giving serious thought to having my 300WM barrel rechambered. It would end up being a 25.5" with a 1/10 twist. I understand the 1/10 will work ok but that leads to my question: when do you NEED to move to a faster barrel with this round?

I will be stuck shooting factory ammo for another year minimum, and preferably the 225 unless the 212 performs that much better out of my rifle.
Your fine with a 10. Plug your info in the Berger calculator to check it out. I just built another 300 PRC hunting gun with a 10 twist. At the altitude I'm hunting I wouldn't want a faster twist for the 212/215 and my 26 inch barrel. I have to get into coastal AK with freezing temps to really even give up anything.
 
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SRPowah

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Your fine with a 10. Plug your info in the Berger calculator to check it out. I just built another 300 PRC hunting gun with a 10 twist. At the altitude I'm hunting I wouldn't want a faster twist for the 212/215 and my 26 inch barrel. I have to get into coastal AK with freezing temps to really even give up anything.
So I knew the 10 would work, but you indirectly answered my question perfectly by suggesting the calculator. I've always been able to jump straight into well known calibers with the ideal twist rate that I never bothered to learn what variables lead to wanting a faster or slower twist. Now being forced to work with my current barrel has forced me to learn.

If my future plans work out, a Proof 28" 1/9 stick will be my firearm purchase next year.
 
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Dippy

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My 300 PRC, built on a new predator action from Dave Tooley, modified to accept CIP length mags, along with my 30” Bartlein 9 twist, chambered and installed on said action, by Mr Dave Tooley, should be here with in a week or so. Dave said it was done!

Super excited!

Now should I put it in a manners with a mini chassis and CIP mags, or a AI AX chassis... decisions decisions
 

jwknutson17

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My 300 PRC, built on a new predator action from Dave Tooley, modified to accept CIP length mags, along with my 30” Bartlein 9 twist, chambered and installed on said action, by Mr Dave Tooley, should be here with in a week or so. Dave said it was done!

Super excited!

Now should I put it in a manners with a mini chassis and CIP mags, or a AI AX chassis... decisions decisions
Nice! My DT spun up barrel on my Cadex rifle hammers.

I would look at a Cadex chassis also. I prefer it over the AIs. Manners is a good choice too! Can't go wrong this day in age really.
 
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Dippy

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Nice! My DT spun up barrel on my Cadex rifle hammers.

I would look at a Cadex chassis also. I prefer it over the AIs. Manners is a good choice too! Can't go wrong this day in age really.
I sure will.

Next is having my M700 spun up by Dave in 300 PRC. Same barrel, that’s going to be my long range deer rifle!
 

jwknutson17

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My 300 PRC, built on a new predator action from Dave Tooley, modified to accept CIP length mags, along with my 30” Bartlein 9 twist, chambered and installed on said action, by Mr Dave Tooley, should be here with in a week or so. Dave said it was done!

Super excited!

Now should I put it in a manners with a mini chassis and CIP mags, or a AI AX chassis... decisions decisions
I'm interested in what velocity you see with a 30 tube.

I was going to send DT my Cadex action again to rebarrel to a heavy varmnit 29 or 30 inch and run 230 A-Tips as fast as I can with my 338 can on it for a mile + gun.
 
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Ledzep

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With RL-26, 2894 (74.3gr) to 2953 (75.9gr) with 230's is what I'm getting in a 31" barrel. Touch lands at 3.845 +/- a few thou (SAAMI spec reamer). Loaded to max mag length around 3.748" jumping almost .100, doesn't seem to care. SD of 5fps, Shot this group:
7104937

Take that one top right shot out and the other 9 are .457" or so.

On the 5th loading of my brass so far and primer pockets are still tight.
 

jwknutson17

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With RL-26, 2894 (74.3gr) to 2953 (75.9gr) with 230's is what I'm getting in a 31" barrel. Touch lands at 3.845 +/- a few thou (SAAMI spec reamer). Loaded to max mag length around 3.748" jumping almost .100, doesn't seem to care. SD of 5fps, Shot this group:
View attachment 7104937

Take that one top right shot out and the other 9 are .457" or so.

On the 5th loading of my brass so far and primer pockets are still tight.
Excellent! I didn't think that it would be "that" long with the SAAMI reamer. What are you seeing as far as COAL with different pills at the lands? Seated deeper are you seeing any difference in velocity or pressure. Just curious if you used the custom reamer DT has if you would see any difference in pressure with the different seating depths varying that much.

2953 is really good. Did you ever load it to pressure? If so when did you start to see it?

I think this is the way I'm going with the 230s in one of mine. 250s are to heavy for the PRC in my opinion.
 
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Ledzep

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Sorry in advance for the novel...

A year or two ago I got the chance to conduct some pressure and velocity testing with a legit pressure test barrel and it kind of opened my eyes as far as "seeing pressure". At the point you see pressure signs in a well-made custom action, you're probably in the 68,000-75,000psi range. SAAMI max for this cartridge is 65,000. So somewhere in between when you see a flat primer, or an ejector swipe or whatever it is, and the actual SAAMI max is 3,000-10,000psi unaccounted for. Max published loads tend to follow that SAAMI max avg. pressure pretty closely (this is where SAAMI chambers, the same brass, bullet, etc... plays a part-- deviation from what was tested causes deviation in pressures).

Anyway, there are a couple reasons I don't typically exceed those loads. The first is that things work better. I almost never get a stuck case, sticky bolt, etc.. Cases briskly extract and eject without issue. Cases last 10-30 firings-- in my last 6.5 barrel I averaged 22 firings on Hornady cases. Once you stretch the case out from too much juice, the primer pockets don't "heal" over time, they're toast. So my price per shot for brass goes to almost nothing. And finally there's the barrel. If you run the stress/strain equations for a thick-wall pressure vessel with a typical barrel contour for the first 4-5" of bore @ 60,000psi internal pressure you'll see that it's on the edge of yielding (plastic deformation) in the ID of the bore. Granted, a firing event isn't the same as static internal pressure loading, but the moral of the story is that the hotter you load, the higher the pressure, the more work is done to the bore. The wider the bore expands each shot before contracting back to original dimensions, the more work is done to the material, the sooner it will work harden and develop cracks (the last sentence purely theory on my part, but it does seem intuitive and appears to hold true if you look at guys loads vs. round count to burnout).

Long story short you get more case life, more barrel life, easier running, safer system, at the expense of 50-100fps. Run the numbers out to 2500yd and see how much 100fps at the muzzle helps you in wind variability. If I want that speed back (in this case I do), I get it through barrel length. If you read a few pages back here you'll see at least one poster that smoked primer pockets in 3-4 firings without seeing pressure. You see the same thing in 6.5 SAUM and 6.5 PRC cases-- Hornady makes their stuff to handle SAAMI pressure and not much more. You can get away with more with some other brands but it doesn't necessarily mean you're "safe" or that you're doing your equipment any favors. YMMV, to each his own, etc...

So with that said, I think shortening up the throat would increase pressure-- as a general rule that's what happens. I don't know if it would increase velocity, but it might, slightly.

I was around 3.715-3.720" COAL for 225's to touch the lands. Ran them at 3.700" COAL. They go 2940 fps with 74.6gr of RL26. Doing a linear interpolation for bullet weight vs. velocity, the 5gr of difference in bullet weight would make up about half of the ~35 fps change from 225 to 230 both with 74.6gr of powder (2905 vs. 2940)... So yeah, jumping an extra .080" probably has something to do with it, about 15-20 fps worth maybe.

This is really subject to individual barrels, but I did not find a satisfactory grouping load over 75.0gr. 75.0 was similar to the above picture, but SD was around 8 or 9 IIRC. Figure your ES is usually about 3x your SD so 1.5 up and 1.5 down-- past 1500 MV spreads start producing really significant POI changes.
 

jwknutson17

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Apr 29, 2017
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Sorry in advance for the novel...

A year or two ago I got the chance to conduct some pressure and velocity testing with a legit pressure test barrel and it kind of opened my eyes as far as "seeing pressure". At the point you see pressure signs in a well-made custom action, you're probably in the 68,000-75,000psi range. SAAMI max for this cartridge is 65,000. So somewhere in between when you see a flat primer, or an ejector swipe or whatever it is, and the actual SAAMI max is 3,000-10,000psi unaccounted for. Max published loads tend to follow that SAAMI max avg. pressure pretty closely (this is where SAAMI chambers, the same brass, bullet, etc... plays a part-- deviation from what was tested causes deviation in pressures).

Anyway, there are a couple reasons I don't typically exceed those loads. The first is that things work better. I almost never get a stuck case, sticky bolt, etc.. Cases briskly extract and eject without issue. Cases last 10-30 firings-- in my last 6.5 barrel I averaged 22 firings on Hornady cases. Once you stretch the case out from too much juice, the primer pockets don't "heal" over time, they're toast. So my price per shot for brass goes to almost nothing. And finally there's the barrel. If you run the stress/strain equations for a thick-wall pressure vessel with a typical barrel contour for the first 4-5" of bore @ 60,000psi internal pressure you'll see that it's on the edge of yielding (plastic deformation) in the ID of the bore. Granted, a firing event isn't the same as static internal pressure loading, but the moral of the story is that the hotter you load, the higher the pressure, the more work is done to the bore. The wider the bore expands each shot before contracting back to original dimensions, the more work is done to the material, the sooner it will work harden and develop cracks (the last sentence purely theory on my part, but it does seem intuitive and appears to hold true if you look at guys loads vs. round count to burnout).

Long story short you get more case life, more barrel life, easier running, safer system, at the expense of 50-100fps. Run the numbers out to 2500yd and see how much 100fps at the muzzle helps you in wind variability. If I want that speed back (in this case I do), I get it through barrel length. If you read a few pages back here you'll see at least one poster that smoked primer pockets in 3-4 firings without seeing pressure. You see the same thing in 6.5 SAUM and 6.5 PRC cases-- Hornady makes their stuff to handle SAAMI pressure and not much more. You can get away with more with some other brands but it doesn't necessarily mean you're "safe" or that you're doing your equipment any favors. YMMV, to each his own, etc...

So with that said, I think shortening up the throat would increase pressure-- as a general rule that's what happens. I don't know if it would increase velocity, but it might, slightly.

I was around 3.715-3.720" COAL for 225's to touch the lands. Ran them at 3.700" COAL. They go 2940 fps with 74.6gr of RL26. Doing a linear interpolation for bullet weight vs. velocity, the 5gr of difference in bullet weight would make up about half of the ~35 fps change from 225 to 230 both with 74.6gr of powder (2905 vs. 2940)... So yeah, jumping an extra .080" probably has something to do with it, about 15-20 fps worth maybe.

This is really subject to individual barrels, but I did not find a satisfactory grouping load over 75.0gr. 75.0 was similar to the above picture, but SD was around 8 or 9 IIRC. Figure your ES is usually about 3x your SD so 1.5 up and 1.5 down-- past 1500 MV spreads start producing really significant POI changes.
Good points. With the Hornady load data they show 2850 with a max load of RL26 in a 24 inch barrel. I am curious at what point the length is not doing much more. I was thinking you weren't close to max yet with a 31 inch barrel based on MV until I looked again.

I was the one getting 3-4 loadings on some brass. Some of it goes longer. Some was done after a short time. Not worried about it. Rather take the extra FPS performance and deal with the brass for now. If I get 1500 rounds out of a barrel, that's fine, spin up another. I am actually only one gr of H1k over max and that seems to not be as hard on the brass. I didn't see swipe and primers flatten til 2gr over max but then backed down a grain. No ill effects the other day shooting in 100 degree weather either.

For my SAAMI reamer chamber I am at the lands at 3.662 with the 212s. 3.700 with the 225s. The 215 Berger's are at 3.727. Sounds like yours is about 20 thou longer then mine.

With a suppressor and a 29-30 barrel I was hoping RL26 would get me close to 3k. Curious what others are getting?

Thanks for the info! Good points and data. That 10 round group is excellent. Great shooting.
 

Ledzep

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Thanks. Load-for-load I've been pretty consistently 100-120fps over the book listed velocities with the extra 7" of barrel. I would have expected a little more, like 150fps, but it's not a complete dog. I'm also curious to see what others get in 30" barrels.
 
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JMattJ

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Dec 10, 2018
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I just received my Proof Research small-shank pre-fit in 300 PRC and the Hornady Match and Hunter factory loads both feel like they're jamming into the lands when I slide them in the chamber by hand. I could send it back to Proof, take it to a gunsmith and have the throat lengthened, or just leave it. Any other thoughts or suggestions?