OAL of the projectile, not cartrige.

I just checked a new batch and have +/- .009. Seems to me a .018 variance in seating depth would not be conducive to accuracy. Last batch from another mfr was .004. Was I just lucky?

I would think variations in bullet weight would have more effect than bullet length.

Cast bullets are not perfect. A multi-cavity mold will have variation in bullet length. Perfection is expensive, that's why cast bullets are cheaper than jacketed. Your target will never know the difference.

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S&WHF 366

I've never done a controlled study, but I'm pretty sure you'll find less variation in the overall length of a batch of cast bullets than you will find in a batch of jacketed bullets. If not, something is certainly wrong.

I only measure a bullet to compare to previous/known loads with similar bullets. I never noticed this much variation (with lead or jacketed).

I need to quit analyzing and just load and shoot!

Some day when I'm retired, I can measure, graph, record this type of stuff! lol

Bullet "fit is king"
As a wise reloader on this forum would say

But matching diameter of bullet to the cylinder throat and or barrel diameters is the "fit" referenced

Are you asking with regard to revolver? Semi-auto pistol?
Rifle?

It's not about the compared variance in a batch of bullets

It's about the variance from the correctly sized bullets for each individual firearm

You can gage the correct diameter from group size on the target and whether there is leading in the barrel

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I'd like to agree with you BUT

For pistol cast bullets I would not give .009 a second thought. As previously (well) noted, fit is king. Measure some of the commercial handgun bullets you buy in bulk sometime and you will see variation. At 50 yards it is really not going to make a difference.

.018 variation in "bullet" length would be excessive in my book, and probably is the result of not having a clean sprue cut-off. If so, it shouldn't have a direct effect on "seating depth" though.

Affect accuracy?? Maybe or maybe not. We'd need to know a lot more about the bulet and cartridge involved to even venture a guess on that point.

Sorry for the lack of details!

158 grain SWC for revolvers.

The "extra material" is at the base of the bullet, so I'd have .018 (likely more due to a bit a variation in the process anyway) variation in case capacity as they would be seated to the same cartridge OAL. Seemed like a lot, but I don't really have anything to go by but past lots.

Are you shooting competition out to 50 yards? If so, get a Ransom Rest and check your groups. If not, just shoot the bullets because the tiny variances really won't make much of a difference, especially from 25 yards and less. You must be an engineer!

In 38 special or .357 there will be no difference. The only concern I'd have is if you are at very max loads in .357 using powders that take up the whole case.

In 9MM that variation might be an issue, but again only with max loads .

If you are casting, check the base for the sprue cut. Is it flat, clean cut or ragged torn cut? I haven't measured the length of the cast bullets I use and as long as the weight doesn't vary more than 3 or 4 grains I'll use them...

I wouldn't worry about .009" at all. You do realize you are taking about nine one-thousands of an inch???

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Freedom is never free!!
SWCA #3437

Well, .018" if an inch.

Not an engineer, just occasionally OCD. I also like to error on the safe side, and seating bullets ~.020 deeper (the extra length takes away case capacity) was the 1st thing that came to mind as almost all my loads seem to end up near max anyway.

Oh, and I like little groups, even if I can't shoot them offhand!

Weighing the cast bullets before lubing for consistency and only accepting bullets with a good looking bases makes more difference in the group size. Having once been a bullseye competitor (for decades) I can tell you that I've never heard of anyone measuring the OAL of the bullet to get better accuracy and many bullseye shooters are really annal about their slow fire (50 yards) reloads.

Like previously said,if the base is square,it'll shoot straight.I sell some to competitors and friends and if a bullet has a slight imperfection on the nose,I keep for myself.But if the base has the slightest defect,it is tossed in the melting pot.The base is what steers the bullet.Qc

I agree about the base of the bullet but I sort of like the driving bands fully filled out and NOT frosted.

If the variance in length is due to nasty, uneven sprue cuts, try letting the molds cool just a couple of seconds longer. If that is a no-go, try a new sprue plate. Yours may be dull, warped, have lead build-up on the underside or a mix of the above.

Bruce

If you really want perfect cast lead bullets, buy a single cavity mold and try casting 500 identical bullets. Get back to me in two weeks with your findings on "perfection" -- good luck!

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S&WHF 366

If two bullets are the same diameter, but different lengths, the should have different weights! If the do, not a big deal out to 2 to 4 grains (for handgun ammo) If they do weigh the same, then you have a problem! there are voids (holes) inside the bullet that can cause them to become erratic in flight.

As to casting near perfect bullets. It won't be fast but: 1) use a alloy that is the same every time! [no scrap!] 2) use a single cavity mold. 3) use a pouring ladle, not a pour through pot. 4) cast 10-15 bullets to warm every thing up and melt the bullets down. 5) use a pot that stays at the same heat or a casting thermometer and adjust to the same temp.

Depending on pot size and bullet size, you will get close to the same number of bullets per session. Stop at that point! If you want more bullets start from scratch. 10 pounds of alloy gives about 400 bullets, so that would be a batch size. If you follow these steps, all your bullets in that batch will be within .1 to .2 grains! and the same length! and the same diameter!

I did a group of small batches (spare time at work) that totaled almost 500 bullets. These were 330 grain RH flat base for 38-55 in a Black Powder Cartridge Rifle, I used 20:1 lead/tin alloy. Because of the several mixed batches, I weighed all the bullets. 1 bullet weighed a grain off, I placed the all the other bullets in groupings of .3 grains (+/- .15 grains). To give the percentages, 1 grain equals >.33% and .3 grain equals >.1%! I really didn't need to weigh them at all! These are for shooting to 600 yards. When I miss, I cannot blame the bullet!

Ivan

I also like it better when it looks perfect(just like with girls....but don't you tell my wife!)What I meant is even if the side or nose has a hairline,it won't show on a 20 or 35yds target.I know,by handgunners standard is a medium-good distance but as per rifle standards,that's a very short distance.And the bullet doesn't know if it has been propelled from a rifle or handgun;only that it responds to the same laws of physics.
If the base is uneven,check for any lead buildup under the sprueplate and if there's any,stop casting right away.Use a sharp rasor blade and clean it up while it is hot(can also do it when cold but lead is of course harder to remove)Of course,use gloves..You'll also at this point have to clean the top of the mould.
Qc

What is the weight variation of the long and short bullets? If it is under 1% as I am fairly sure it should be shoot and forget about it. The minimal length difference in bearing surface will not change pressures enough to impact a 25 yard target. if you are shooting @ 100 yards cut your variance down to 25% of what you no have.

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Front sight and squeeze

When reloading .38/357 I check the Cartridge OAL measurement. It will only vary + or - .002" normally and maybe up to .003" if the Dies need a cleaning but that's it. So I guess an extreme spread from the smallest to the largest scenario would be about .005 to .006".

As far as cast bullet variances themselves, I have very little. I buy from Dardas Cast Bullets and they are really super consistent. If they vary .001 - .002" that's about it. His QC is excellent! I do not cast my own lead bullets - that's where I draw the line

You know , in 50 years of casting and reloading I never thought to measure the length of cast bullets....I keep measuring the diameter.

I don't think I'm going to be concerned about the projectiles overall length, I would bet money jacketed bullets vary also....maybe more than cast !

Gary

I typically have a 3-4 gr difference in bullet weight from a 4 cavity mold. I've never been concerned with difference in bullet length. OAL is pretty consistent so I don't worry about it. Back in the day when I was shooting Bullseye we cherry picked molds to get the most consistent weight. I'm not sure it made any difference, but did give us something to argue about.

You made me curious.
Missouri Bullet 40 Cal 180g TCFP, IDP #5-GL HiTek Coated
After a sample of 20
.622 - .626 or +/-.002 OAL
179.8 - 182.3 g or +/-1.2g

Pacific Delta 40 180 FMJ
Sample of 20
.587 - .589 or +/-.001 OAL
179.6 - 180.7 +/- .55g

Obviously a larger sample should reveal larger numbers but I consider both VERY good. The Pacific Delta's FMJ are awesomely consistent.

0.004" is hardly significant, even 0.009", no issue. Flashing on the nose, sprue cut, shrinkage, all affect bullet oal. I doubt 5% of shooters could decern any accuracy diff between bullets with greater length or weight deviation. If you want near perfect bullets, use a single cav mold.

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