Why are my velocity spreads so big???

7magsavage

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So I am able to load ammo for my 7mmRM and my 6.5X47L with pretty decent extreme spreads (in the teens), but for the life of me I can't get my 308 to less than about 40fps extreme spread. I have no idea why. I load them just like everything else i load for. I anneal every firing or every other at the most, i size my cases bumping the shoulder with no expander ball, use an expander mandrel to get the necks right, load everything with my Chargemaster, and seat with a Forster bench rest seater. The 308 gets BR2 primers and shoots amazing groups at 100 yards. I can consistently get sub 1/2 Moa groups at 100 and was busting water bottles (20 oz) at 445yards just the other day. But I know that at greater distance the velocity spread is going to kill me. I measured the velocity with my V3. Any suggestions would be greatly appreciated.
Steve
 

AIAW

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A) Using consistent headstamp brass? - Case capacity.

B) Which powder? How much?

C) What is the average velocity?

D) Which bullet are you testing?

E) Check to see if your seater is seating off of the bullet tip/meplat versus the ogive? You want to seat off of the ogive - Seating depth inconsistencies?
 
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Matches Malone

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So I am able to load ammo for my 7mmRM and my 6.5X47L with pretty decent extreme spreads (in the teens), but for the life of me I can't get my 308 to less than about 40fps extreme spread. I have no idea why. I load them just like everything else i load for. I anneal every firing or every other at the most, i size my cases bumping the shoulder with no expander ball, use an expander mandrel to get the necks right, load everything with my Chargemaster, and seat with a Forster bench rest seater. The 308 gets BR2 primers and shoots amazing groups at 100 yards. I can consistently get sub 1/2 Moa groups at 100 and was busting water bottles (20 oz) at 445yards just the other day. But I know that at greater distance the velocity spread is going to kill me. I measured the velocity with my V3. Any suggestions would be greatly appreciated.
Steve
In addition to the other information requested above, im curious on your SD as well, if you have that on hand.
 

427Cobra

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its the shoulder angle, the 47L is designed from ground up to be accurate and easy to load for, 308 is really not that hard to get in to single digits spreads, but it is more work than the 47L, and may require tuning as the barrel wears out, ultra consistent powder charges, seating depths, and neck tension are very important, figure out where pressure is, and just below that is going to be the sweet spot on powder charge, seat by olive length, and .0015-.002 neck tension
 

straightshooter1

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So I am able to load ammo for my 7mmRM and my 6.5X47L with pretty decent extreme spreads (in the teens), but for the life of me I can't get my 308 to less than about 40fps extreme spread. I have no idea why. I load them just like everything else i load for. I anneal every firing or every other at the most, i size my cases bumping the shoulder with no expander ball, use an expander mandrel to get the necks right, load everything with my Chargemaster, and seat with a Forster bench rest seater. The 308 gets BR2 primers and shoots amazing groups at 100 yards. I can consistently get sub 1/2 Moa groups at 100 and was busting water bottles (20 oz) at 445yards just the other day. But I know that at greater distance the velocity spread is going to kill me. I measured the velocity with my V3. Any suggestions would be greatly appreciated.
Steve
First, understand that 7mm and 6.5's are much easier to get loads that produce single digit SD's or ES's than a .308. So, just be sure to understand this so that your expectation are not our of line with reality. Now, I do get single digit SD's with my .308 loading and my ES's are very often in the teens but I'd say they kinda hover around 20 fps. I haven't seen anyone that's done much better with the .308 cartridge, though I'm not saying it absolutely can not be done. Early in my attempt for precision loading, I was getting the same kine of ES's as you and struggled to get it down to where I am now.

I do everything you've listed here as well as pretty much the same equipment, including the same chrono, and just a little more, and I'll go over that, but first thing is . . . I'd look very close at your Chargemaster and verify that you're getting as consistent powder loads as you think. I had to do some tuning of my CM to get it to not over throw to where that over throw isn't so much at either end of the +/- .1 gr causing those kinds of ES. When I don't get an ES in the teens, I'm certain it's this issue and sometimes I'll get just one load that's so far out from the others, it's obvious that this is what's happened.

Case volume is another key factor and consistent seating depth is key to consistent ES's. To get consistent seating depths, I sort my bullets by measuring base to ogive in +/- .001 groups. Then when I seat each group I know my seating depth is very consistent. Some lost of bullets and have a wide range of BTO measurement and I've had as much as .033 with 168 SMK's. The other thing for case volume that I do is to weigh and sort the cartridges as there is a little correlation between weight and volume. But when it comes to this, I'm only looking for those cases in the bunch I'm loading that is an outlier and usually it's only a 3-5 cases out of 100 . . . depending on who's brass your using. The better quality brass has a lot few variations than the cheaper brass.

The only other thing I think that I do that you do not, is that I turn the necks. I do it not so much for concentricity, but also to get an the neck tension even around the full circumference of the neck.

Hope this helps. :cool:
 

j-dubya

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Did you do an OCW test and are you loading in the middle of the node? Using a Chargemaster can have varying consistency each throw, and those throws can be further exacerbated with the speed settings and aperture of the dispenser combined with the type of powder kernel size you’re throwing. When I’m loading 4064 for my 308, my chargemaster will still throw some wild charges +/- .2 from the desired number. And that’s even with tuned speed settings and using the drinking straw mod to even out the dispensing. I finalize my charge weights with trickling onto a lab scale, so it’s a non-issue for me. But it is something to be aware of in case you’re relying solely on your chargemaster.

ETA- for clarification, my chargemaster will say the charge is at the desired weight. The lab scale is how I noted the .4gr operating window.
 

7magsavage

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Ok guys Ill try and answer a few questions. Like I believe I mentioned, I measured my velocity with a Magnetospeed V3. Been loading for precision for a decade and have loaded tens of thousands of rounds.
From my five shots that I measured, which I know is not statistically significant, my average velocity was 2592fps. Min was 2568 and Max was 2611 with an SD of 17.3. I KNOW this is a small sample size, but the fact is, it can only get worse, not better if i fired 10, 20, 50, or 100 rounds across the V3.
I use Lapua brass, and have been loading the 178gr Hornady ELD-Ms. I have never turned a neck, or weight sorted my brass or bullets because frankly I have never had the need to .
The five shots that I fired that I mentioned above measured just over .4" at 100 yards. One ragged hole. The rife shot well at 445yards the same day. But if one can believe the numbers, then I am going to have a major issue at longer distances. Granted, I don't usually shoot beyond 500 yards with the 308, which makes this whole think a wash, I know. But i would still like to produce the quality ammo with the 308 that I routinely do with my other calibers. Thanks for all of the advise guys.
Steve
 

7magsavage

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Almost forgot. I have checked the CM against an RCBS 1010 beam scale and it has been dead nuts on.
I have also been using the Scott Satterlee method for finding a flat spot in the velocity. This WAS the flat spot when i did load development for this rifle several hundred rounds ago, but I decided to strap on the V3 just to verify and was really disappointed with the numbers when I did.
 

straightshooter1

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I use Lapua brass, and have been loading the 178gr Hornady ELD-Ms. I have never turned a neck, or weight sorted my brass or bullets because frankly I have never had the need to .
Frankly, I don't think weight sorting brass OR bullets is necessary, particularly when using quality products. But . . . I HAVE found sorting bullets by BTO can and does when there's significant differences within the box/lot. Sometimes I get a box where I only find a .002 - 003 variance and when I see that, after 20 or 30 measured, I'll stop there and conclude that box of bullets is uniform enough. But often, there's more variance than that and so I'll sort into groups having no more than .002 difference and that's helped, definitively, is bringing my ES's down. For example, my ES's are most often in the teens and sometimes it'll jump into the low 20's, which invariably is a result of a single shot where I feel sure it's because of the way my Chargmaster weighs the powder (single digit SD's either way) .



If you haven't tried sorting bullets by BTO before, give it a shot using 20-30 rounds and see when you get. :giggle:
 

Culpeper

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Maybe you just have a 308 that doesn't like Varget and BR2. Or maybe it likes Varget but not BR2 or vice versa. Maybe something slower like the 4350s or N150 range.
 

918v

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Don’t anneal. You’re prolly overdoing it and the neck is too soft and affects powder ignition. Rework the load in .2gr increments looking for a velocity flat spot, then adjust the oal. You need to find a charge weight range of .6grs yielding similar velocity. Otherwise you’ll be dicking around with various component combinations until your barrel is fried.
 

Culpeper

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I don't like annealing but he is using the same method with his other cartridges with no problems. He is also indicated he is finding the flats okay but that is based on very few shots. His ES is too high to find a wide flat he can depend on. So yeah, stop annealing 308 for one thing as well.
 

Doom

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OP, you didn't mention barrel length. The velocity you are showing is in line with a middle node for a 20-22" barrel, typically with around 41.7 gr of Varget based on my experience, but not with an ELD bullet. If you are shooting a 24 or 26" barrel you may be too low and need to bring the charge weight up to improve case fill.

I think you are annealing to often, unless you have a chamber that is really working the necks (oversized).
 

7magsavage

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Hey guys thanks for all of the input. The rifle is a bolt gun with a 20 inch barrel.
I have to say that Im surprised to hear you guys say "don't anneal". Im not saying you are wrong at all. And I will certainly give that a try. But it seems i read more of "annealing is the bees knees" so to say, and that everyone should do it.
Just can't figure out why the 308 seems to have all jacked up numbers but the other two precision rifles I load for are dead nuts where they should be. keep the suggestions coming.
 

Nimothy

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For what it’s worth I think 178eld’s are to long for a precision minded mag fed rifle. And could never get them to shoot even close to 168’s in whatever rifle I was loading for I think it’s because They eat up to much case. I’d stick with 168’s of whatever brand you like in 308. I bet when you gain your capacity back slightly under 45gr of varget will probably put you close, I’d run 43.5-45 in .3gr increment. I bet you find a nice performing load that has good numbers to boot
 
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straightshooter1

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Hey guys thanks for all of the input. The rifle is a bolt gun with a 20 inch barrel.
I have to say that Im surprised to hear you guys say "don't anneal". Im not saying you are wrong at all. And I will certainly give that a try. But it seems i read more of "annealing is the bees knees" so to say, and that everyone should do it.
Just can't figure out why the 308 seems to have all jacked up numbers but the other two precision rifles I load for are dead nuts where they should be. keep the suggestions coming.
Here's a good article on annealing:


Even with the Pro's, they all do not anneal. But it seems that has a lot to do with the custom chambers that don't work the brass so hard. If you haven't seen this article before, check it out (the pic is from that article):


Picture1.png
 

_Raining

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My SD's went from low teens with Varget to single digit with N150. Just because a powder is widely used and performs well in most rifles does not guarantee it will work in your rifle.
 
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straightshooter1

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My SD's went from low teens with Varget to single digit with N150. Just because a powder is widely used and performs well in most rifles does not guarantee it will work in your rifle.
The same thing happened when I went from Varget to AR-Comp.
 

918v

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Could it be that when you switched powders you accidentally landed in a velocity flat spot for that particular combo?
 

_Raining

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Could it be that when you switched powders you accidentally landed in a velocity flat spot for that particular combo?
Was that directed at me? If so, no. I worked up load for both powders and shot 5 and 10 shot groups. Varget was weighed with an Entris 64 1s and the N150 was thrown sloppily on the chargemaster. Varget had SD's around 12-15. N150 had SD's around 4-12. Note the Entris was giving great results with my RL16/6.5 Creedmoor gun (3-8 SD's). I did also switch to H4350 and the SD's were high single digit low teens up until the 42-43 range then it dropped down to mid single digits.

I assume that changing case or bullet can also have this sort of effect. Sometimes the norm doesn't work out and you gotta try some stuff till you find what it likes (SD's aside the groups at 100 were similar for Varget and N150 as well as RL16 and H4350).
 

Steel head

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Hey guys thanks for all of the input. The rifle is a bolt gun with a 20 inch barrel.
I have to say that Im surprised to hear you guys say "don't anneal". Im not saying you are wrong at all. And I will certainly give that a try. But it seems i read more of "annealing is the bees knees" so to say, and that everyone should do it.
Just can't figure out why the 308 seems to have all jacked up numbers but the other two precision rifles I load for are dead nuts where they should be. keep the suggestions coming.
Annealing is awesome when it’s needed.
It’s a waste of time when it’s not.