Reloading tolerances?

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pilot_dc

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Hello all,

Perhaps this should be in the reloading threads, but I want to ask precision shooters specifically.

I'm in the process of working up BR loads for a new 308. I'm relatively new to precision shooting but I've been reloading for a while.

Lets assume that all my scales etc are 100% accurate and that the extra time it takes to load is only a minor factor. In other words I'm gonna load X number of rounds whether it takes 1 hour or 4. Also assume I'm using the best quality components I can get my hands on (which I generally do).

What sort of quality control do you apply when trying for top accuracy. In other words if you're aiming for 43.2 gr powder charges, would you allow +/- 0.1 gr? Is there a point where it doesn't really make a difference anymore?

Also, when I'm sorting bullets I generally group bullets that are within 0.1 gr of each other, is that a reasonable tolerance or should it be tighter?

Thanks all,

DC
 
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With respect to grouping bullets or cases by weight, it depends how many you are sorting. For example I usually have more than 500 match bullets ready to load, so if I am trying to keep the smallest group size, I have enough bullets on hand to make sure that the bullets of each group are exactly the same weight. When I am finished loading, the ammo in my ammo box is divided into 5 shot groups. Group to group weights may differ slightly, but round to round weights within a group are very tight.

I may only have a hundred suitable cases for accuracy work available for loading at any one time. And with cases, when we weigh them we are actually talking about volume. I am inclined to keep the cases separated by weight in lots of 5, and again I strive for identical weight within that group, but I am not anal about it. In fact I doubt if it really matters all that much if there is a grain separating the weight of the cases. The reason I say that is because I do not believe that weighing powder to the nearest 1/10th of a grain matters. When I work up loads I don't worry about powder weights smaller than a half a grain, and I doubt, with cases the size of the .308, that one gets better accuracy with powder weights rounded off to a quarter of a grain rather than a half. Maybe I've just been lucky, but I sure don't see the benefit of trying to figure if the load is more accurate with 45.3 grs or 45.7 rather than 45.5. When it comes right down to it, I'm not so sure most powder scales are accurate enough to reliably tell the difference either - never mind once operator error is added to the mix.

So, be precise as possible with your bullets, but don't worry so much about the weight of your cases. I think that attention to detail during your case prep, with concerns for uniform primer pockets, deburred and uniformed flash holes, true necks, and proper bullet pull weight are all far more important than the infinitesimal difference in volume from one case to the next based on the weight of less than a grain. If you doubt this, consider that powder in a case is measured in fractions of a cubic inch. Upon firing, the gas volume produced inside that case could be measured in cubic feet. Suddenly a half grain variance in weight between two cases doesn't seem so critical does it?
 
The case capacity of the 308 is larger than most BR cartridges and therefore you have a slightly greater amount of latitude in terms of powder weights. The farther away you are shooting the more careful you will want to be. Having said that, I always strive for the fewest variables I can and always load to the tolerance of my scales.

As for brass, I use Lapua and I keep brass for each chamber (rifle) separate. I trim to exactly the same length and weigh to cull the high and low. I use them, but not for a match. I chamfer the case mouths and unify the flash holes.

I use Lapua bullets and their weights are close enough that for ISSF matches, I am happy.

Work up a load with a proper seating depth and a powder charge that works and stick with it.

If you are picky all the time, it leaves fewer variable to chase down when things go wrong. Barrel life is best used for shootin', not fixin'.
 
Boomer said:
Excellent point! I wish I'd said that. Another reason I don't try to tweak accuracy to 1/10th of a grain.
Click to expand...
I use lapua brass and check my bullets out on a QC basis ( not every one, about every tenth in a 600 round lot), and check my powder charge regularly to make sure they are being thrown correctly.
The biggest variable in shooting with slings and irons is normally the shooter, not the ammo ( as long as it is consistant and matched to the rifle) , so I do not weigh every charge.
However, if I am shooting in a a different type of match, I will weigh every one.
Lapua brass is so consistant that I don't need tocheck it.

Barrel life was never a big issue with me, barrels tend to wear out if you shoot them a lot, which I do in my competition rifles.

Cat
 
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When I make match ammo, my best friend is my Sinclair runout guage. I test each step to ensure that the ammo is concentric. I will allow up to 3 thou in the finished rd. For plinking, up to 5 thou and it still hits clays at extended ranges.

For powder, I will weigh every charge and hold to the closest tenth so 44.5gr and allow the error in the scale for variance. Tuning the powder charge is critical to maximizing accuracy (as important as matching bullet to barrel). I have varied loads as small as 1 tenth and always 2 tenths. However, I don't shoot group after group to prove a load. 3 rds fired will either group or not (I test at 200yds whenever I can). If it shows promise, I will retest a few more times. Otherwise, I move on. I can usually tune a barrel in 20rds for a bullet. A few more groups to confirm at longer distances then I am enjoying my rifle.

Pay close attention to pressures and group shape. You do not want stringing and flyers.

I would rather take a consistent cluster then a really tight group with a few way out. Both may have the same overal group size but the 'smaller' one is not reliable. I would take the consistent group and tweak that.

I always work with fireformed brass or FL sized as I would normally shoot. Primers are match.

I use US commercial brass like Win and Rem. Never found any benefit in the more expensive Euro/custom stuff. I will neck turn and basic prep so essentially I have match brass anyways for a lot less money.

I do check case volume NOT case weight (I will also sort during shooting). Trimming and deburring the necks is a good idea however, I have shot some amazing groups with necks that were not perfectly square or trimmed to length so the jury is out on how much effort to spend there. Flash hole deburring is important to me too.

I DO NOT SORT or TRIM a Match bullet. For me, a bullet can only be called match if it comes out of the box accurate. There are some major brands that definitely need to be worked over.

For me, I shoot lapua Scenars in my 6.5, Hornady Amax everywhere I can, Bergers in my 7 mystic, and will work through my final batch of MK's for my 300RUM. The Hornady Vmax is an excellent bullet and has proven extremely accurate way out there too.

Once we have made the ammo as consistently as we can, the limiting factors are elsewhere. The accuracy is determined by our barrel and how well it is set up in that stock. The trigger, stock shape, optics and how consistent we are during firing matters more then ALL the BR prep we do.

What handloading allows us is to extract the max accuracy that is inherent in that rifle.

Jerry
 
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