help me get my extreme spread down on my .308

Captain Moroni

Captain Moroni

Well armed easily annoyed
Full Member
Minuteman
Jan 20, 2007
1,324
4
45
Pocatello ID
www.highdeserttactical.us
#1
OK to start off I will give you my reloading routine. When get new brass I debure the flash holes and use the primer pocket uniformer tool I'm not sure that the first two make and difference but I bought the tools so I use them. then I use a sinclair neck turner and cut the necks down to 14 thousants then I trim them down to SAAMI spec leanth. I size the brass with a Redding FL bushing sizer with .338 bushing that gives me .002 grip on the bullet. I weigh each powder charge and seat the bullets with a Redding comp. seater die touching the lands. So last time I shot over my shooting chrony (I cant remember the model but its the blue one that tell you the ES and SD for a 10 shot string) my extreme spread was 101 fps. what am I doing wrong it has never been that high before usualy is around 30 fps or so that I can live with. oh its a savage action with a Mcgowen bbl. anybody got any ideas?
Thanks Tucker
 
#2
Re: help me get my extreme spread down on my .308

So long as you are not using mismatched brass, I would want to know how you are measuring charges. Also, try going up to .003" or more on the neck tension and see what that does, after that try going up to a longer jump to the lands....say .030 or so.

Lastly, what powder and charge weight are you using and what bullet?
 
#3
Re: help me get my extreme spread down on my .308

Rafael, I am using Remington brass its not my first choice but it was available and a good price. I use a dillon electronic scale and trickle up to the correct weight. my load is 175gr SMK 42.5 Rl 15 and 210m primers. I'll order a new bushing and see if that helps
Thanks Tucker
 
#4
Re: help me get my extreme spread down on my .308

Are you checking that the scale goes back to zero between charges? This can be an issue.

I have had good results going up in neck tension, and run at least .003" now.
Also, you might try different primers or powder to see if it helps. Best guess without knowing seating length and case volume, QL says you are around 98.5% burn efficiency, which does not sound bad. What's your barrel length and measured velocities?

Pressure seems pretty low based on QL numbers, were it me I would work my way up in charge as well.

I find that virgin Lapua is the cheapest brass around if you place a dollar value on your labor. I don't do a thing to Lapua cases and they do fine.
 
#6
Re: help me get my extreme spread down on my .308

check out your primers. That much vel spread, and you're all messed up. Go for CCI 200's or FED 210's. If you're using other primers, I'd recommend looking into the above. Next, roll your loaded rounds over some glass. See if you're seeing a bit of run-out on the noses of the bullets.

No need to weigh the charges. If you've got even a lyman 55, it'll dump decently if you set it up right. Ball powder will dump better than extruded.

Could also be varying anneals on the same flavor of brass. How many reloads at the extreme, would you say were on the brass? You can always run them over a torch to soften them up to a consistent level.

What kind of bullets you using? Are you sure they're all the same weight?
 
#7
Re: help me get my extreme spread down on my .308

First off, have you changed any of your load components lately? If you have, then whatever you changed to is probably the culprit.

If you've changed nothing, then I suggest running a few more strings of that same load over the chrony again. Could be that you may have just had one bad round. No biggie, it happens to all of us once in a while.

If nothing has changed compnent wise and you still get large ES then I'd suggest checking your case volume by water weight. Put fired primers into the case and weigh it. Next, fill it to the base of the neck with water. Then weigh again and take the difference, that is your case capacity.

This method works really well in diagnosing case volume issues. Not to mention you can get some extremely low ES with this method.
 
#8
Re: help me get my extreme spread down on my .308

Thanks for all the advice I will check and re-check and see what I come up with. Unless Seirra is in the habbit of mixing 190's in with 175's Im sure that they are all the same weight. they are new brass so I may need to aneal them.
thanks agian Tucker
 
#9
Re: help me get my extreme spread down on my .308

I would try checking your bullet run out first, Sinclair makes a slick run out set up or you can make one up. A field expedient method is like what 1SJ said above, I've done that to sort issued ammo at various rifle matches. If you are getting a lot of run out, or if your bullets are moving back into the case under recoil, you aren't getting enough neck tension to retain the bullets. Try without turning the necks AND either let your expander ball stem stay loose in the lock nut so it "floats" with the case neck, or better yet, use a smaller caliber decapper/expander so you aren't touching the inside of the case neck at all after resizing.
I would keep a detailed reloading log and try changing just one thing at a time, making up small batches of 10 or 20 rounds for testing, and make cetain that you write down all lot numbers of each componment as you go so you can weed out anything bad you run accross.
Last of all, I had 2 friends that have had issues with the Dillon electronic scale and I know that a while back, Dillon had a recall on them. I would use either a regular powder measure and a scale or a powder scoop to measure loads, and double check the electronic scale to verify accuracy.
 
#10
Re: help me get my extreme spread down on my .308

Its the Remington brass, ang flash hole size inconsistancy, I am willing to bet. I jusy experianced similiar results with my .243 and remmy brass,

Get a numbered drill bit set, and start finding the biggest bit that will fit in the largest flash hole out off all your brass. Then chuck it and get all your flash holes consistent. That has a huge impact on shot to shot ignition and consistency, if that sounds like too much work, buy Lapua brass.
 
#11
Re: help me get my extreme spread down on my .308

I would listen to those who suggested verifing the chrono first, and looking at SD rather than ES since one or two oddball cases or thrown charges can make it look a lot worse than it is.

Lots of things to check, as listed above, if those are ruled out.
 
#12
Re: help me get my extreme spread down on my .308

Get some known good ammo..... FGMM168 or 175... and try... maybe it is not your loads...

Post your MV/ES/SD for your FGMM, many of us have data to compare against yours... then we can figure out if it is your testing setup or if it is indeed your loads.

My RL15/175SMK/FED210M has ES like between <20, and single digit SD.
 
#13
Re: help me get my extreme spread down on my .308

First of all, how is it that you're turning your necks to .014" and then using a .338" bushing with any 308 brass? 308 brass, even Lapua brand is not that thick to begin with and certainly, a .338" bushing is way too much, as .014" + .014" = .028" + .308" = .336". Your bullets shouldn't be gripped at all if you're using a .338" bushing, unless I'm missing something?

I'd start there, personally.

Chris
 
#15
Re: help me get my extreme spread down on my .308

A couple of things:
A) you did not indicate the kind of brass, the primer, the powder, the target charge weight and actual OAL.
B) with 338 bushing and 14 thou neck thickness, a bullet (0.308) should drop right through the neck (0.338 - 2*0.014 = 0.310) Thus, you appear to have -0.002 in neck tension
C) have you verified the accuracy of the scale used to measure the powder? Have you cleaned the fulcrums lately?
 
#17
Re: help me get my extreme spread down on my .308

Chris,


Good call on the math. I should have got that one. The other question: OK, the Extreme spread was more than 100 fps. So what? What was the standard deviation, and, and, and, was the low or high shot from the first round????? What did the population look like? Only one round down low or high, and the rest in a tight group? Let's keep this in perspective: Here's a baseline for you: 60 fps extreme spread will yield 1 MOA at 600 yards with a 175 grain SMK, or thereabouts in a 308. Don't sweat the small stuff.....
 
#20
Re: help me get my extreme spread down on my .308

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Captain Moroni</div><div class="ubbcode-body">So last time I shot over my shooting chrony (I cant remember the model but its the blue one that tell you the ES and SD for a 10 shot string) my extreme spread was 101 fps. what am I doing wrong it has never been that high before usualy is around 30 fps or so that I can live with. oh its a savage action with a Mcgowen bbl. anybody got any ideas?
</div></div>

Yo Tucker, you leave out the one variable that matters the most. How well do these loads shoot?

You can chase variables all you want. But will this make your loads more accurate?
 
#21
Re: help me get my extreme spread down on my .308

Lots of dough and time in reloading components and tools, and you trust a shooting chrony?
I have one, but just to get velocity averages to work with, and it tells me some crazy stuff sometimes.

I'm with Nate, if the load shoots well on target, it don't matter what the shooting chrony is telling you. I had mine tell me once that I had an ES in triple digits on a load that shot sub moa in 3 different 308's.

Same load a couple months later came in with a 12 SD (FGMM was 13 at the same sitting). The Sshooting chrony's are sensitive to light variations and muzzle blast in my limited experience.
 
#23
Re: help me get my extreme spread down on my .308

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Mr. Humble</div><div class="ubbcode-body">spread and sd are tools NOT answers. put it on paper PERIOD</div></div>

100fps deveation at 1000 yards is a huge miss, it matters.

For the 100 yard plinkers, I suppose have at it.
 
#25
Re: help me get my extreme spread down on my .308

Don't use a flash hole deburrer! Many guys in benchrest began using this tool a few years ago and their spreads opened up. You cannot make a concentric flash hole with the tools they make. It is a great idea but has not been perfected yet! What you are actually doing is making your ignition more inconsistent. Once guys quit using these tools they began shooting well again.
 
#26
Re: help me get my extreme spread down on my .308

Ian,

Whoa... ok really? I heard some guys saying this at the 1K national in CO but sort of dismissed it.

So, that step in brass prep isn't necessary? Can you enlighten me with any examples of post and prior data when doing or not doing this step.

 
#27
Re: help me get my extreme spread down on my .308

Try weighing your brass and sort into weight batches.

Use Lapua/Norma brass (no need to deburr flash holes with these brass) or at the very least Winchester - stay away from Federal it's too soft.

Your load is good to go.

Play with seating depths but also try 2.80" OAL, that's all I use now.

Try another brand of chrono.
 
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