Do Slight Variations In 9mm Weight Effect Accuracy?

[peeplwtchr]

Hi-

I am posting this here, because relaoders are likely the best people to answer this. So I was bored last night, and started weighing different brands of 9mm rounds. I noticed that most had variations with between 1-10 hundredths of a gram. The Remington "Military Grade" had the least. If I were shooting a round with a 8 or 10 hundredth deviation at 75 yards from an 8 inch barrel PCC, would I notice an accuracy difference compared to rounds with much less weight deviation? Not sure what causes the deviation i.e. casing, powder, bullet.

Thanks

 

[RetiredUSNChief]

Considering one gram is 15.432 grains, I'd have to say even 10 hundredths of a gram variation would be insignificant and have no noticeable effect on accuracy on a typical 115 grain or 147 grain bullet.

EDIT:

Just noticed you were apparently taking about the weight of the entire cartridge.

Still... no.

 

[peeplwtchr]

Considering one gram is 15.432 grains, I'd have to say even 10 hundredths of a gram variation would be insignificant and have no noticeable effect on accuracy on a typical 115 grain or 147 grain bullet.

Correct, entire cartridge, thanks!

EDIT:

Just noticed you were apparently taking about the weight of the entire cartridge.

Still... no.

 

[Skeptic13]

If you weigh bullets all from the same box there are variances. If you weigh cases from the same manufacturer there are variances in case weight. Some bullets and cases are more consistent but I have yet to find ones that are the exactly same weight. So when you put all the components together that don't weight the same you end up with completed rounds that have weight variances. I stopped worrying about it.

 

[NATO Reloading]

The answer is "no" they don't. Variations in 50-100 FPS do not matter much at all at pistol ranges, using same bullet. Using different bullets, same everything else, the Point of impact can move dramatically.

 

[nettlle]

Bullet type/style/brand/quality will have a bigger contribution to accuracy than small variations in bullet weights. Bullets are the best secret when reloading.

 

[LaneP]

Minor variations in the weights of components is unavoidable. In good production examples, these variations are held to acceptable tolerances and will have less influence on accuracy than other factors such as bullet hardness, length and diameter as it relates to bore diameter, rifling depth and pitch, charge weight and burn rate, etc. In a perfect world all our components would weigh identically but that is not a realistically achievable goal for most of us.

I used to weigh out my cast lead bullets and would cull bullets above or below a certain weight threshold but found I was wasting valuable time. I suppose if you're a match shooter that wants to squeeze out every last thousands of an inch in group size it's worth the effort, but I just toss lead at paper targets so for me it's not, and in that regard the affect on accuracy is minimal.

 

[higgite]

Hi-
If I were shooting a round with a 8 or 10 hundredth deviation at 75 yards from an 8 inch barrel PCC, would I notice an accuracy difference compared to rounds with much less weight deviation? Not sure what causes the deviation i.e. casing, powder, bullet.

Thanks

It depends on whether the weight difference is charge weight, bullet weight or brass weight. Most likely a little bit of all 3. In any case, if you can tell the difference in POI with that little cartridge weight variance at 75 yds out of an 8” barrel, I tip my hat to you. The practical short answer is no for us mere mortals.

 

[FROGO207]

Well to prove it if you get boored weigh them out and try batches of identical ammo and get back to us.
I find it low on the point of diminishing returns of time spent on actual effort spent on reloading. Heck a difference of a grain of propellant would probably not be detectable the way my handgun targets look.

 

[LiveLife]

Not sure what causes the deviation i.e. casing, powder, bullet.

Many jacketed bullet weight can vary by 1 grain.

Some plated bullet weight can vary by few grains.

I have seen lead bullet weight vary up to 4-7 grains depending on caliber/brand.

Powder charges can vary by 0.1 grain.

Many brass casing weight can vary by few grains or more depending on caliber/headstamp.

Do Slight Variations In 9mm Weight Effect Accuracy?

10 hundredths of a gram ... If I were shooting a round with a 8 or 10 hundredth deviation at 75 yards from an 8 inch barrel PCC, would I notice an accuracy difference compared to rounds with much less weight deviation?

10 hundredth of a gram is 1.5 grains.

When I was taught to reload by a bullseye match shooting mentor, he had me sort bullets by exact weight but for my USPSA "action pistol" shooting accuracy, I considered bullet weight variance of 1.0 grain good enough for match shooting. ELEY recently selected RMR as their choice of bullets for new line of centerfire match ammunition and Guns America Digest review found RMR bullet sample of 20 showed weight variance of 0.3 gr -
https://www.thehighroad.org/index.p...ine-of-match-ammunition.854750/#post-11201936

I have found RMR in-house manufactured jacketed bullets to often vary by less than 0.5 gr when other brand jacketed bullets can vary up to around 1.0 gr.

Will this smaller weight variance show at 75 yards shot from an 8 inch barrel?

Likely no as there are other factors like OAL/internal case volume, neck tension/bullet setback, powder charge variance, etc. which can overshadow slight difference in bullet weight.

And there's another factor of shooting variance from 8 inch barrel out to 75 yards. When I tested 9mm loads out of my 16" PCC at 50/75/100 yards, I started to notice effects of bullet drop even at 50 yards (Bullet drop will show on target as vertical elongation of group). At 75 yards, muzzle velocity variance could have contributed to as much as 1-2 inch elongation and at 100 yards, 4-6 inches.

Due to bullet drop factor, I started testing lighter bullet weights for PCC load and obtained smaller vertical elongation.

Here's my 50 yard 9mm groups using lighter 100 gr bullet over 115/124 gr bullets. While I believe slight variation in bullet weight can affect accuracy at 75 yards, I think there are too many other variables/factors to be able to tell on target.

Promo load produced less muzzle velocity variance than HP-38 load and smaller 100 yard group. (1478-1475-1480-1471-1467 fps)