Too much variation?

J

jonnefudge

New member
Hi
I am fairly new to shooting and reloading, I reload my 308 for maximum accuracy. I might eventually change barrel and start competing in prs. When I reload I obviously strive for the same amount of powder and C.O.L. However I settle for +\- 0.1 of a grain and +\- 0.15 mm of C.O.L what is your opinion on my "tolerances". Do they effect my accuracy? I am trying to eliminate all variables except my own shooting skills but I am also a busy man with family work etc. meaning that I don't want to spend too much time on every cartridge I reload. Your opinion is greatly appreciated!


Jonne
 
+/-.1gr (.2gr)is probably ok but it's more tolerance than I personally accept. I keep my loads within .1 so essentially 1/2 what you are. For 308 you are likely in the low 40gr per charge or higher and I don't think .2 gr will matter. How did you work up your load? If you use dan newBerry's ocw approach it really shouldn't matter. I've used loads where 1/2 a grain didn't make a difference but it really depends on the load/rifle. If you are loading for maximum accuracy you should be looking at all tolerances, runout, case volume, etc. Runout will likely have more effect than your powder variation if you are exceeding .003.

What is your load?
What other techniques do you use to sort cases, bullets etc.
what are you group sizes ?

If you are really loading for max accuracy you want to make minimize all variation. Variation will stack up, a little variation in charge weight, a little variation in coal, a little variation in runout, case volume etc. not good.

Group size matters in that if you are shooting 1/4" groups you probably have less tolerance than if you are shooting 2" groups.
 
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The load is 308, vv n140 44grains, cci 200, scenar 155, c.o.l 71mm, lapua cases.

I also measure for 0.1 grains maximum variation but my franford arsenal also looses zero 0.1 sometimes.

I do not sort bullets but examines and measure cases.

I got a custom built pierce that shoots very well. Even though I am far from skilled I regularly shoot 1/2 moa.
 
Probably ok but the only way to know for sure is to load with intentional variation and try. If your load is 44gr. I would load 5 rds each of 43.9,44 and 44.1 and shoot 5, 5 shot groups where each group has a mix of all 3 loads. Mark the rds, and note where the impact is. Sounds like you are shooting at 100M, my guess you won't see any difference. Make sure you call your shots.
 
Just my opinion here. +/- .1 grain of powder you will never know which cartridge was over or under the .1 of a grain of powder. At times when we are doing something new we tend to over think things.Even if you used a chronograph you would not see a +/- .1 difference in powder charge. Tolerance is there for a reason. Load calls for 40 grains starting and a maximum of 44 grains 39.9 or 44.1 is not going to be catastrophic.
 
Also keep in mind that very small variations in anything MAY not show up at 100 yards, but if you are shooting at longer range, they might. I have proven to myself that it is definitely possible to have a load that shoots great at 100 yards or in some cases 50 yards and when you take it out to longer ranges, things fall apart.

Obviously the goal of having very consistent powder weights (or volume) is to keep your velocities as uniform as possible (low standard of deviation and minimal extreme spread). It stands to reason that if every bullet is going down range at the same velocity, this should translate to tighter groups.

Whether or not a given variation in powder charge matters can only be determined by a chronograph and your groups fired at a range as far as you are ever going to shoot as well as what YOU think matters.
 
Unless you are using a REALY high end scale nobody loads better then +/- .1gr . I weigh each charge to exactly zero on my scale . How ever like most reloading scales it guaranties +/- .1gr . So even though I weigh everything exactly the same . I'm still at best +/- .1gr . That said I do use check weights so I may be doing a little better then that .
 
You need to get to 3/10 powder before you can see any variation.

1/10 +/- is more than good enough.

No idea what .15mm is, but the best way to do COAL is an OGIVE setup and bullets vary .003 so you can call it .005 and it gets no better.

Shooter makes far more difference.

Good neck tension and minimum shoulder bump back helps more.
 
Metal god said:
Unless you are using a REALY high end scale nobody loads better then +/- .1gr . I weigh each charge to exactly zero on my scale . How ever like most reloading scales it guaranties +/- .1gr . So even though I weigh everything exactly the same . I'm still at best +/- .1gr . That said I do use check weights so I may be doing a little better then that .
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Thanks good and nice to know!
 
I don't mess with neck dies so off the range on that one.

I do minimum shoulder bump, you need a good Micrometer (I use a digital just because its fast and easy) and the Hornady Should set. set which is low cost.

I don't know who makes decent micrometer these days, mine are a bit on the older side (Sterrit) but last sterrets are made in Japan on the digitals anyway. Probably fine (my digital replacement is one of those). I have an old Fowler at work I got in a pawnshop that works fine (it had the mm to inch feature that is a help in this day and age of mixed metric and US)

If you do it, start with a .003 bump back to get tuned in (there will be case to case variant) and then you can go .002 or .00015 if you want, I don't but that's just me. I shoot for .002.

Always check some random mix of the cases in the chamber of the gun it will be shot in or all the guns it might be shot in.

Chambers from gun to gun even form same mfg are not the same and you can get a mis- fit.

I slight tight closure on the bolt is ok, hard one - no.
 
Ok I am going too do some reading on neck tension and shoulder bump.
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First find a gage that measures tensions, seater presses are being made that read hydraulic pressure, I am the only reloader across all of the forums that noticed the gage reads in pounds with no tension conversion. I have tension gages, all of my tension gages read in pounds, I can measure interference fit and crush fit, I have stuck one piece inside of another knowing the interference fit and measured the crush fit in pounds, thousands of pounds but reloaders have an infraction with tensions.

I have noticed a few are sneaking over the line and adding bullet hold to their description, I can measure bullet hold in pounds I can measure bullet pull in pounds. When it comes to bullet hold I want all the hold I can get.

And then there is shoulder bump, reloaders assume they can bump the shoulder back, many of them can describe things and events in lofty terms, but when I ask them to explain how is it possible to bump the shoulder back with a die that has case body support they get all snarky on me.

Up-front, I say I find it impossible to bump the shoulder of the die back with a sizing die. SO? if they are bumping the shoulder back I will assume they are purchasing their dies from the same place Jack got his magic beans.

F. Guffey
 
"...change barrel..." Means you'll have a new rifle and will have to work up the load again.
1/10th of a grain is enough to go from an inch group to one hole.
.15mm is .0059" and is totally insignificant and it's highly unlikely you can adjust your seating plug that little.
In any case, there's no reason you cannot set up your seater die to give 2.800" OAL and forget about it.
You can forget neck tension and shoulder bump too. Neck tension can't be adjusted and you can't measure 2 thou of case shoulder change without special tools.
"....00015..." That's 15/10,000". It's less than the diameter of a human hair. No regular measuring tools go that small.
 
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