Can mixing different bullet lots effect accuracy?

[VaniB]

When trying to shoot tight benchrest groups, everything matters, including weighing each bullet in the box of 100 bullets, and sorting the bullets accordingly into the same weight groups. My question is whether I can group bullets this way from two different boxes which were produced months apart. (?) Should I be concerened that bullets from different production runs can look and weigh the same, but may have a different jacket thickness or hardness, or something else that I'm not taking into consideration?

Often, I get to the end of a box of bullets, and I'm left with three bullets that each weight say 140.2 grains (for example)......but I want to be able to shoot a 5 round group, not a 3 round group. So then I have to open a fresh box of bullets and find a couple of more 140.2 grain bullets until I have 5.

 

[Bob Sebold]

Short answer is yes, it can affect accuracy. Depending on how far apart the runs are they can and do get thicker as the dies wear out. I don't know how much this affects short range, but I know it will mess with you in long range shooting. If you have a good micrometer and know how to read it, measure them. If they are very close, say 1 or 2 ten thousandths they would be okay. I have seen different lots up to 6 ten thousandths off. They will give elevation changes at long range.

 

[Shynloco]

When trying to shoot tight benchrest groups, everything matters, including weighing each bullet in the box of 100 bullets, and sorting the bullets accordingly into the same weight groups. My question is whether I can group bullets this way from two different boxes which were produced months apart. (?) Should I be concerened that bullets from different production runs can look and weigh the same, but may have a different jacket thickness or hardness, or something else that I'm not taking into consideration?

Often, I get to the end of a box of bullets, and I'm left with three bullets that each weight say 140.2 grains (for example)......but I want to be able to shoot a 5 round group, not a 3 round group. So then I have to open a fresh box of bullets and find a couple of more 140.2 grain bullets until I have 5.

VaniB,
I've experienced exactly what you are asking about and did just today while reloading for my newer 30BR. Accuracy is my thing, although I do not compete, except with myself and my last best target. Sometimes, its impossible to guage if you'll have enough bullets, but then I've also tried to keep my loads within the same lots, for powder, bullets, casings (weight wise) and even primers. But I've also separated them on purpose for downrange results for comparison. I simply haven't seen that much difference in the results of the mixes, yet that might well be simply because of the rifle I'm shooting. I will add that though I shoot precision bullets (Barts) in my 6mmbr, I have noted no differences when mixing Bergers or Sierras which I predominantly use in various caliber Benchrest rifle having "decent" but not great actions. So I guess the bottom line may be if your have an accurate shooting rifle, though not a "Precision" and "High Quality" actions, your rifle will tell you if it doesn't like the mix of lots. Hopefully some of the guys with high precision rifles (the $6000+ variety) will chime in and offer their opinion. Just my thoughts and observations. BTW, I do shoot 5-shot groups for every target I shoot that I believe better confirms a load and it's accuracy.

Alex

P.S. Bob S just chimed in so let me clarify that I shoot strictly 100 yds. He, in my opinion, is correct that those differences asked about will affect long distance more than short distances which I shoot. Thx Bob!

Alex

 

[ShootDots]

Don't expect any component change out to act the same.
Not bullets, powder, brass, primers...... take nothing for granted.
As well as seating depths for bullet Lot change outs.

+1 Donovan is exactly right..

 

[ridgeway]

With a certain manufacturer, expect huge diameter differences between lots! And a big yes, don't expect them to shoot the same. Almost have to match a reamer to a lot of bullets!

 

[Joe Maisto]

With a certain manufacturer, expect huge diameter differences between lots! And a big yes, don't expect them to shoot the same. Almost have to match a reamer to a lot of bullets!

For sure Ridgeway...

and for that reason, my bullets are made by one man . Most of us in the NBRSA or IBS short range BR business buy from a one man operation . We can specify...

 

[artbosco]

Can mixing different bullet lots effect accuracy?

Yep, sometimes big time!

 

[XTR]

I don't shoot BR but in 1000 yard F class if I save the odd man out leftovers when I change lots for sighters and foulers for the first match of the day and always take a sighter with the batch that I am going to shoot for record. Just me, not sure it matters that much but I do it for my peace of mind.

 

[Joe Maisto]

Its not so much the weight variation on differents lots as base to o-give difference. I have three different lots of 30 cal Bergers 115's and they are all different O-give to base length. The same lot of bullets are the same, Just the different lots measure .328, .315, .335. base to O-give. Randy

Rewinder;
I agree that base to ogive is perhaps more important as bullet weight. I went through 800 bullets a few years ago made by a bullet maker/shooter whom some of us have indeed shot a match with. I began checking base to ogive on everyone of them and found a huge differance in 354 of them, so they have been seperated. He must have used two differant dies for the amount of differance there was. I won't trust them in a match so will sell them off. This is where a Mitotoya digital caliper shines when used with a comparator.

Joe

 

[XTR]

Its not so much the weight variation on differents lots as base to o-give difference. I have three different lots of 30 cal Bergers 115's and they are all different O-give to base length. The same lot of bullets are the same, Just the different lots measure .328, .315, .335. base to O-give. Randy

I have checked different lots of Berger 185 Juggs and found as much as .010 base to ogive variation; however, it made zero difference in the base to ogive measurements on the loaded bullets.