Bullets unseating in AR10 when chambering

Subwrx300

Mastery: its difficult for a reason....
Jan 15, 2014
291
82
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Cedar Springs, MI
#1
Need some suggestions: my 6.5CM AR10 rounds are unseating when the round is chambered. Using starline brass, Hornady seating die, and both a Hornady and Lee full length resizing die.

Without crimp, bullets seated to 2.790 jump forward to 2.835-2.840 (into the lands) when chambering with bolt latch or cycling by hand.

With a Lee taper crimp, they do the same thing even when I crimp excessively (obvious crimp ring and bullet deformed).

At a loss for how to resolve this. I'm looking for another die that has mich tighter neck tension BUT I can't imagine that more neck tension will solve this given that a super hard crimp still has bullets unseating.

Suggestions?

Also could someone else with 6.5CM measure bullet oal, chamber round with mag latch (or forceful rack) and measure afterwards? Curious if this could be resolved by heavier buffer or lighter spring.

Thanks!
 

mgrs

New Hide Member
Feb 18, 2018
18
1
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#2
How much neck tension are your dies putting on the case? Can you mic it and the bullets you're using?

I would hesitate to start switching springs and buffers around and put reliability at risk to turn your rifle into less of an expensive kinetic bullet puller.
 

Subwrx300

Mastery: its difficult for a reason....
Jan 15, 2014
291
82
28
Cedar Springs, MI
#5
Measure your neck tension...measure a sized case neck then a loaded case neck.

I've never crimped a round in my life and dont have this issue. I use Forster FL sizing dies with .002 neck tension.
I've never needed to crimp either but I've never had a rifle unseat bullets when chambering like this one is. I'll put a mic on my brass and bullets shortly. One die is setup with .003 and the other is .004 I believe, both have mandrels so it could be that the starline has thicker neck wall and is expanding more when pulling out of die.

I tested the effects of this on accuracy today and it is VERY noticable. 6 rounds single fed by pressing all the way into chamber and then releasing bolt shot .7moa. 6 rounds may feed shot at 2moa. Another set of single feeds shot .8moa.

I've never had to go more than 3-4 thousandths with other semi autos so it makes me think it's something to do with the lighter bcg and heavy spring.
 

Subwrx300

Mastery: its difficult for a reason....
Jan 15, 2014
291
82
28
Cedar Springs, MI
#6
Just measured bullets and sized brass with Hornady die:
Bullet - .264 dia 123 SMK
Starline LR brass - .289 outside diameter, .2615 inside
Seated bullet- outside neck diameter .291-.2915

My math says about .002-.0025 neck tension.

Lee die is .288 after sizing and .2905 with bullet. About .003-.0035 tension.

Go to .004 or .005 by reducing mandrel or maybe even bushing die? I've never had to go this far to keep bullets seated when chambering in Semi-auto.
 

supercorndogs

Professor Dickweed
Feb 17, 2014
1,988
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#8
Is it possible you have a short throat and bullets are seating into the lands, and getting pulled out a little when you extract them?
 

Subwrx300

Mastery: its difficult for a reason....
Jan 15, 2014
291
82
28
Cedar Springs, MI
#9
I load 5.56, 243, 6.5 grendel, 300blk, 308, 300wsm, and 458 socom for ar's and have never crimped any of them. Never had an issue with bullets moving. Are you maybe getting case lube in the neck?
Only lube was light Hornady one shot. I use same process on several other rifles and have not had any issues with like causing separation or skipping bullets.

Is it possible you have a short throat and bullets are seating into the lands, and getting pulled out a little when you extract them?
I thought that too but I put a round in chamber manually (pressed all the way into chamber with my finger) then dropped bolt with spring and extracted. No rifling marks; only scratches from the star chamber as it gets extracted. And OAL is unchanged with that method. Single feeding by hand completely eliminates the issues, so it's definitely something to do with forceful chambering and sudden stop.
 

Subwrx300

Mastery: its difficult for a reason....
Jan 15, 2014
291
82
28
Cedar Springs, MI
#10
Update: I increased neck tension to .005" and still had issue. Then I seated bullet from 2.790 to 2.720. First round moved .002" and second moved .008". This is much better than before but I have to seat bullets WAAAAYY into case.

Also tried this with Hornady brass... When seated at 2.803, it jumped out to 2.809" which is much less than the Starline but not ideal.

At this point, I'm unsure how else to solve this other than a heavier buffer. This should slow down the BCG on the forward stroke (more mass with same force equals lower speed) and this might solve issue. But I'm very surprised that even .005-006" neck tension isn't keeping bullets in place.

I do think the Starline brass is a bit softer which could be leading to less grip but only have anecdotal evidence of this.

Any further suggestions to try?
 

Subwrx300

Mastery: its difficult for a reason....
Jan 15, 2014
291
82
28
Cedar Springs, MI
#11
PS also tried crimping with increased tension and still had same issue. Even Hornady brass is doing it. Have a set of tungsten weights on order to try increased buffer weight.
 
Mar 27, 2014
46
10
8
Mpls, MN
#12
Disclaimer: I don't reload for semi-autos, just bolt guns. I shoot factory 223/5.56 in AR-15s; no experience shooting large-frame ARs, but know about all the incompatibility issues between manufactures.

What rifle components are you using? Could the mag, or upper/lower fit be causing the rounds too feed in a way that messes up the neck tension? What do the case necks look like after the bullets become unseated?
 

Subwrx300

Mastery: its difficult for a reason....
Jan 15, 2014
291
82
28
Cedar Springs, MI
#13
Disclaimer: I don't reload for semi-autos, just bolt guns. I shoot factory 223/5.56 in AR-15s; no experience shooting large-frame ARs, but know about all the incompatibility issues between manufactures.

What rifle components are you using? Could the mag, or upper/lower fit be causing the rounds too feed in a way that messes up the neck tension? What do the case necks look like after the bullets become unseated?
Savage MSR 10 Hunter, and three different barrels: factory, Dracos 22" and Aeroprecision 20" all chambered in 6.5 Creed. All three barrels do this so it's not specific to the barrel. I'm starting to lean towards a combination of super heavy buffer spring, BCG too light and buffer too light. Basically, it allows the BCG to move at lighting speed and when case stops, bullet keeps going.

Case necks look fine (as much as can be after being scraped against the star chamber/lugs). Upper/lower lockup is tight.
 

Subwrx300

Mastery: its difficult for a reason....
Jan 15, 2014
291
82
28
Cedar Springs, MI
#14
As far as cleaning goes, shit can accumulate under the extractor and cause problems. If you can, remove the extractor and look for brass/steel shavings and other buildup that may be preventing the extractor from popping over the new case rim.

Also:

Measure your buffer spring to make sure it is within tollerance. Then check the installation of the botl catch to see if it is binding or not.

Then I would check for burrs in the chamber. Do you have a forward assist? Are you hitting it with your palm to get the bullet seated? If you do, can you extract the unfired round? If yes, then are there any gouges on the case or bullet itself? With the upper and lower seperated, how much force would it take to close the bolt and bolt carrier fully on a round?
Im not having cycling/extracting issues. It functions fine except that bullets driven into the chamber by the BCG (either using bolt catch, manual cycling or by firing round/auto chambering) start at normal OAL and end up .015-.035" longer.

BCG and bolt will lockup on round very pretty minimal/normal force. I can split the upper lower and chamber round with a solid push of the BCG.

If anyone here has an AR chambered in 6.5 can the same test I'd appreciate it. Especially if you have an MSR10. I think they went too light on the BCG with WAAYYY too much spring. It's a serious brute of a spring. Maybe this was their (Savage) way of ensuring cycling/feeding without much tuning.

Next call will be to tubbs or other custom flatwire spring. If the tungsten weights help this issue, then i think it points to too much BCG velocity. Most BCGs for large frames are about 1"-1.5" longer than the one in my rifle. It uses a standard 3oz carbine buffer. Basically it's an AR15 BCG and buffer with a heavy ass spring and bigger bolt face.
 

KZP

For Sale Access
Mar 11, 2017
88
21
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Raleigh, NC
#15
Saw this and it has me curious what my gun does. I have a 308 AR10 and I just tested a 178gr bullet in a starline case with .002 neck tension. It jumps out of the case .002 every time I chamber by letting the bolt fly.

I've got the JP LMOS BCG and Standard SCS. I might try a softer spring since I also have an adjustable gas block I can tune.
 
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mgrs

New Hide Member
Feb 18, 2018
18
1
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#17
I am thinking about building a 6.5 upper so am interest in what you find.

You’ve had much better luck with one shot in rifle ammunition than I have. I had a tough time getting cases slick enough with it, resulting in some FL sizing inconsistency as the harder to size cases seemed to stretch on their way back out of the die.
 
Oct 8, 2014
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Shreveport, Louisiana
#18
I'm starting to think this is an MSR 10 problem in design. I'm going to reach out to other MSR owners and have them try this.

Thankf for posting!
This is what I was thinking while reading through the thread. Sounds like your bolt is slamming your round to hard in the chamber. Try a different buffer, and if you have access to one, a different bolt.
 

Greg Langelius *

Resident Elder Fart
Aug 10, 2001
4,998
404
83
Arizona, good place for me...
#19
If this problem is widespread, it should make some sense to bring it to Savage's attention; since, as you suspect, this could be a design problem

At very least, it would be a courtesy to them to give them a shot at resolving this. It might get you more than a simple "Thanks for the heads up".

Greg
 

Subwrx300

Mastery: its difficult for a reason....
Jan 15, 2014
291
82
28
Cedar Springs, MI
#20
If this problem is widespread, it should make some sense to bring it to Savage's attention; since, as you suspect, this could be a design problem

At very least, it would be a courtesy to them to give them a shot at resolving this. It might get you more than a simple "Thanks for the heads up".

Greg
I've posted another thread asking some of the other MSR owners to test above and so far both had small amounts of movement BUT they have less than 400-500 rounds through rifle. I'm over 2500 now and system didn't start to "loosen up" (bolt, BCG, charging handle etc) until after 1000 rounds.

After testing the new spring and Buffer combo, should have a better idea of cause. And I will definitely be letting Savage know that this is an issue but my past experience with their CS team tells me they will say "Thank you. You send it the rifle and we can check it out; you get it back in 3-4 months" OR "since you've modified the rifle, we don't care."

In either case I'll bring to their attention and be done. I think this is a solvable problem and buffer/spring combo will fix. It's just physics after all.
 

Subwrx300

Mastery: its difficult for a reason....
Jan 15, 2014
291
82
28
Cedar Springs, MI
#21
Update: Tubbs spring and heavy buffer arrived. Immediately swapped with stock and check if bullets still unseating and they are though not as bad. Bullets seated at 2.760 grow to 2.770-775 which is .010 less than before. Checked factory Hornady 140 and it grows .003-.005 on chambering, which is also better than before.

May try tuning slightly deeper yet and go to a 5.5 oz buffer (have that also). Crimp did not help. Very unusual but accuracy does seem to be improving now that bullets aren't unseating as much.

Frustrating.
 
Feb 13, 2017
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#22
What kind/brand of bullets ? The thinner the copper jacket, the more likely the lead core will become deformed (shrink around the crimp area). Copper (jackets) are harder than lead (cores), so if the jacket is thicker, the crimp has something that doesn't yield as easily. I've been running into a similar problem with my 9mm handgun reloads.
 

Ledzep

Chancellor
Jun 9, 2009
1,288
135
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Black Hills
#25
Just some thoughts on the subject....

The hoop stress in the neck of the case is what holds the bullet. It is elastic. Elastic deformation does NOT permanently deform materials. PLASTIC deformation permanently changes the shape of the object/material... Here's a good test you can perform with a bushing die, calipers, and bullet puller.

1. Size several necks with varying diameters in .001" increments from .001 thru .006" 'neck tension'. Measure and note the ID of each case
2. Seat the same diameter bullets in each of the cases.
3. Use a bullet puller to pull the bullets from the cases
4. Measure and note the ID of each of the cases.

You might find that the ID of the necks does not step up at .001" increments anymore (at least it didn't for me, happy to see someone else's results). It's because you plastically deformed the neck, and have reached a threshold where the elastic hoop stress is more or less the same no matter how much smaller than the bullet OD the neck ID was before you seated the bullet.

Likewise you can measure base to ogive lengths before and after chambering with various neck diameter bushings and see if your numbers vary significantly. This is a little less controlled (variable bolt speed, etc...).

There's a reason military ammunition has the bullet tarred and crimped.

Crimping is another thing I've dabbled with, and I've had best luck with the LEE collet "factory" crimp dies and a light crimp that barely deforms the bullet. Going full retard with the crimp on bullets that don't have a cannelure degrades accuracy.
 
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Subwrx300

Mastery: its difficult for a reason....
Jan 15, 2014
291
82
28
Cedar Springs, MI
#26
Just some thoughts on the subject....

The hoop stress in the neck of the case is what holds the bullet. It is elastic. Elastic deformation does NOT permanently deform materials. PLASTIC deformation permanently changes the shape of the object/material... Here's a good test you can perform with a bushing die, calipers, and bullet puller.

1. Size several necks with varying diameters in .001" increments from .001 thru .006" 'neck tension'. Measure and note the ID of each case
2. Seat the same diameter bullets in each of the cases.
3. Use a bullet puller to pull the bullets from the cases
4. Measure and note the ID of each of the cases.

You might find that the ID of the necks does not step up at .001" increments anymore (at least it didn't for me, happy to see someone else's results). It's because you plastically deformed the neck, and have reached a threshold where the elastic hoop stress is more or less the same no matter how much smaller than the bullet OD the neck ID was before you seated the bullet.

Likewise you can measure base to ogive lengths before and after chambering with various neck diameter bushings and see if your numbers vary significantly. This is a little less controlled (variable bolt speed, etc...).

There's a reason military ammunition has the bullet tarred and crimped.

Crimping is another thing I've dabbled with, and I've had best luck with the LEE collet "factory" crimp dies and a light crimp that barely deforms the bullet. Going full retard with the crimp on bullets that don't have a cannelure degrades accuracy.
I feel like I've already gone dull retard on all possible steps for better neck tension. I will try the suggestion of measurement before and after bullet seating for neck od. I've measured about every other possible variation.

However, that will still leave me with the issue unresolved. I will try a super light crimp to see if seating deeper (more surface area) and light crimp help but I'm nearly to the point of waiving white flag. Reduced charge to 42.2 GR h4350 under the 123smk when seating at 2.750" and it is still throwing some random flyers at distance but bulk of shots seem reasonable. 4 of 5 shots magazine fed landed in .49 MOA at 300yds but one shot at 12ocklock opened group up to .99moa. Other loads with less neck tension produced 1.5-2moa when magazine fed.
 
Feb 16, 2017
7
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California
#27
Subwrx300, I called Tubbs and found that they only offer one spring so that is easy. What buffer/weight did you use. They recommended a T2 and I just wanted to check with you before I made the purchase. I'm trying to not end up with a box of buffers and springs to fix this issue with my JP rifle.
 

Subwrx300

Mastery: its difficult for a reason....
Jan 15, 2014
291
82
28
Cedar Springs, MI
#28
Subwrx300, I called Tubbs and found that they only offer one spring so that is easy. What buffer/weight did you use. They recommended a T2 and I just wanted to check with you before I made the purchase. I'm trying to not end up with a box of buffers and springs to fix this issue with my JP rifle.
I purchased a Spikes T2 and also some additional tungsten weights to try with other buffers. While the Tubbs spring and heavy buffer seemed to help a bit, it's not completely gone. Still moving about .005-.010 which is much better than before. Going to try a bit heavier (even though Tubbs says not to) and see if that helps a bit more.

Groups did tighten up a bit though which is encouraging. Last resort is to try finding much deeper seating depth and lower charge that stays accurate. I think the added seating depth will give more grip and keep bullets at same depth.
 
Nov 8, 2004
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Western Kentucky
#29
I know I'm a little late to this party but one thing I noticed is that I didn't see any mention of cleaning the inside of case neck after sizing. It there is any lube inside the neck then your bullets will dislodge easier no matter the neck tension.

I'm not saying that this will totally eliminate your problem but it could help.
 

Subwrx300

Mastery: its difficult for a reason....
Jan 15, 2014
291
82
28
Cedar Springs, MI
#30
I
I know I'm a little late to this party but one thing I noticed is that I didn't see any mention of cleaning the inside of case neck after sizing. It there is any lube inside the neck then your bullets will dislodge easier no matter the neck tension.

I'm not saying that this will totally eliminate your problem but it could help.
I've considered this and will run a quick test with a bronze brush to clean inside neck. The fact that factory ammo also did this though makes me think it will have minimal effect but definitely worth a shot.
 
Feb 16, 2017
7
0
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California
#31
I


I've considered this and will run a quick test with a bronze brush to clean inside neck. The fact that factory ammo also did this though makes me think it will have minimal effect but definitely worth a shot.
I did this, tested dry and with graphite and noticed little difference. I also called the Hornady and asked them how they get their neck tension seeing that I saw less movement with factory rounds. I was told the procedure was not able to be reproduced by the reloader.
 
Nov 8, 2004
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Western Kentucky
#32
I


I've considered this and will run a quick test with a bronze brush to clean inside neck. The fact that factory ammo also did this though makes me think it will have minimal effect but definitely worth a shot.
A brush will not remove all the lube, you need to use something like alcohol and swabs to remove all of it.
 
Jul 6, 2014
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#33
My .308 AR was doing this too. I got it down to under .010" jump by having a custom expander made, using the Lee FCD, and cleaning the necks. Now they average about .005" or so and FGMM grows .002-.003". The custom expander was from PMA tool, made to .0035" under so it's about .3045". Standard expanders and neck turners are only .001 or .002 under. For cleaning necks I took a .308 brush and wrapped it with steel wool and chucked it in a drill... replace the steel wool as needed.. Lee FCD was set for a little over 1/2 turn, about 200-210 degrees.
 
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Subwrx300

Mastery: its difficult for a reason....
Jan 15, 2014
291
82
28
Cedar Springs, MI
#34
My .308 AR was doing this too. I got it down to under .010" jump by having a custom expander made, using the Lee FCD, and cleaning the necks. Now they average about .005" or so and FGMM grows .002-.003". The custom expander was from PMA tool, made to .0035" under so it's about .3045". Standard expanders and neck turners are only .001 or .002 under. For cleaning necks I took a .308 brush and wrapped it with steel wool and chucked it in a drill... replace the steel wool as needed.. Lee FCD was set for a little over 1/2 turn, about 200-210 degrees.
Huge thanks for this info! This mirrors what I've done so far but definitely may try the steel wool trick to get necks squeaky clean for the most static grip. I think this will substantially help SD and precision at extended range (big issues with vertical in present load I think due to this issue specifically).
 

supercorndogs

Professor Dickweed
Feb 17, 2014
1,988
226
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#35
Huge thanks for this info! This mirrors what I've done so far but definitely may try the steel wool trick to get necks squeaky clean for the most static grip. I think this will substantially help SD and precision at extended range (big issues with vertical in present load I think due to this issue specifically).
A lot of people use dry lube in their necks after SS tumbling because they find that squeaky clean necks are bad for ES.
 
Jul 6, 2014
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#36
I don't get to do much long range.. so can't say how they performed at distance, but I was getting .6 MOA or better groups to 185 yds.. and had loads with single digit SDs and teens ES using this method, though these were not necessarily more accurate than the loads I usually shot (but not a big deal for me at shorter ranges).
 

Subwrx300

Mastery: its difficult for a reason....
Jan 15, 2014
291
82
28
Cedar Springs, MI
#37
A lot of people use dry lube in their necks after SS tumbling because they find that squeaky clean necks are bad for ES.
I've used dry lube too but the issue with bullets unseating .020+ from original combo as bad or worse than anything I've experienced with squeaky clean necks. I'd rather know that bullets have poor SD but are consistent in orientation into the lands than some bullets engraving and some not. I'd take an SD of 10-15 as long as accuracy stays sub .75 MOA.
 

N8Hammer

New Hide Member
Mar 24, 2018
1
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#38
First post...so what do I know.

Lots of critiques of reloading procedures here. Seems like a logical place to start, but it seems almost like we’ve hit the end of the road there as far as “deficiencies” in the reloading process. I’m sure there are a host of things that could be tried as far as the load itself: different bullets, brass, coal, etc. but it seems to me that those things should not have to be changed in order to prevent premature bullet exfil from the case.

I would experiment with a lighter recoil spring along with the heavier buffer you already have. I’ve never shortened a recoil spring so I can’t recommend that. Perhaps someone else can speak to that possibility.

I would guess that you have an adjustable gas block? With that I’d be pretty sure that you can maintain reliability of cycling, unless your rounds are very hard to strip from the magazine or the brass is not sized properly (hard to chamber).

Since it doesn’t seem like increased neck tension is a possibility....Ultimately, you need need to reduce the forward momentum/return to battery of the bolt/carrier. A heavier buffer and a lighter recoil spring should accomplish this.
 

flyer

Sergeant of the Hide
Apr 25, 2018
277
95
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#39
At 2,500 rounds, how are your gas rings doing?

I think they slow down the bolt a little before it shuts so if they are completely worn in, they may not slow it at all.

There was a buffer test somewhere out there and I remember the Spikes T2 didn't do great. I was surprised because it's a tungsten powder buffer, I own one and was expecting good things. It wasn't bad, but I think an ordinary H2 buffer beat it.

I don't think the Savage bolt carrier is a light one so I don't think a heavy buffer is necessarily the direction to go in.
 

Subwrx300

Mastery: its difficult for a reason....
Jan 15, 2014
291
82
28
Cedar Springs, MI
#40
At 2,500 rounds, how are your gas rings doing?

I think they slow down the bolt a little before it shuts so if they are completely worn in, they may not slow it at all.

There was a buffer test somewhere out there and I remember the Spikes T2 didn't do great. I was surprised because it's a tungsten powder buffer, I own one and was expecting good things. It wasn't bad, but I think an ordinary H2 buffer beat it.

I don't think the Savage bolt carrier is a light one so I don't think a heavy buffer is necessarily the direction to go in.
Actually you may be on to something with the gas rings. The biggest change over the last 1500-2000 rounds is the ease with which the bolt moves from locked to unlocked in BCG. It's SUPER easy to flick forward into battery position. I may try getting new rings just as a quick check.

But regarding the MSR BCG, it's actually very light compared to standard bcg. As in a few ounces lighter/shorter. I think that's why they used a standard buffer with heavy spring.

I've exhausted every reloading technique change that *should have* fixed the issue so that simply leaves checking worn in parts. I may simply go to a different bolt (JP or similar) to see if tighter bolt helps as last resort.
 

flyer

Sergeant of the Hide
Apr 25, 2018
277
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#41
If a different bolt is tighter, that sounds like a compatibility issue. Large frame AR bolts are far less compatible than AR15 bolts.

AR bolts also seem to break off lugs more than wear out so if your lugs are intact, I don't think your old bolt should be loose in any way beside gas rings that need replacing.
 

Rhed

New Hide Member
Apr 12, 2018
18
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#42
For me all my ar’s does this. It will lunge the bullet forward by 4-6 thousandths. I’ve done many testing with dummy rounds. What I did to eliminate most of the creep is with .002-3 neck tension. And another .002 taper crimp.
 

ezekeial

New Hide Member
May 17, 2018
2
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#43
Thanks to this thread, checked the pull out on recently purchased MSR 6.5 cm hunter. Hdy factory 120 eld went from 2.710 to 2.715. Hdy factory 140 eld went from 2.814 to 2.828. What scared me was size of dimple on Fed primer with a handloaded round. Haven't shot any handloads through this rifle yet, now planning on using harder primer.

For other semi's in 308 am using Redding s dies with differing bushing dia's for differing brass, and not using neck expander unless needing to trim. Use a Redding match seater to keep bullets straight. Tried this fpr dummy rounds in MSR 6.5, and limited 120 eld pull out to .0025. Hdy 140 eld pull out was non existent. Yes there is a limit to how much increasing the case neck tension may help, but use the same procedure for bolts in 308, 6.5 cm and 223.
 
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