Boolit weight tolerance

[Pahaska]

I'm starting to cast 500gr .510" dia, hollow points for my model 71 Winchester, 50 Alaskan for hunting elk size on up animals. What weight consistencies should I (do you) settle on or strive for concerning consistent accuracy results?

[fredj338]

The larger the bullet the greater the weight variation. I can keep 45/500 withing +/- 2gr but its pretty diff. Shrinkage on cooling is the issue, that & consistent technique in filling the mold. At typical hunting distances with iron sights, say 150y, you are not likely to see accuracy issues +/- 5gr, imo. So with my heavy hunting bullets, I try to keep them with that +/- 2gr range.

[Pahaska]

Thanks. That's about what I'm getting. Anything greater than 1 grain I've been putting back in the pot. I haven't put through the chrono yet to see velocity variances though. My next plan is to powder coat the more consistent ones.

[mehavey]

See https://castboolits.gunloads.com/showthread.php?410814-Do-you-weigh&p=5014895&viewfull=1#post5014895

[fredj338]

Thanks. That's about what I'm getting. Anything greater than 1 grain I've been putting back in the pot. I haven't put through the chrono yet to see velocity variances though. My next plan is to powder coat the more consistent ones.

There will be no vel variations with a bullet even at 5gr diff in weight. Bearing surface is the same & that matters more to vel variation than a few grains in wt.

[Winger Ed.]

There was a article years ago where a guy cast up about 150 boolits from a single hole mold and weighed 'em out.
He had about 10 columns of them lined up from heaviest to lightest in .5gr increments.

It looked like a graph with about 80% of them in the middle four columns.
Except for including the few on the extreme edges, the difference in accuracy/group size was barely enough to measure.

[HWooldridge]

I use +/- 2.0 grains on 200 grain 44-40 bullets and cannot see any difference in accuracy from groups tested at zero deviation. It might be detectable on a benchrest with the right rifle but not under most circumstances.

[Land Owner]

I've poured many thousands of 50 grain* 223 boolits from both a 2-cav. aluminum "55-grain" Lee "Bator" and a 2-cav. steel "55-grain" RCBS Spitzer mold. Weight variations run from 2-grains (-) low to 2-grains (+) high with 80% centered around 50.0-grains, either mold.

Two (2) grains on each side of the average (4-grain spread) is A LOT of deviation (8%) in a 50-grain boolit, which molds are published as 55-grains for some alloy (not mine obviously). I can remelt any of them. If they were not defective in appearance and returned to the pot, I set them aside in marked 0.10 grain increments, for further testing.

Causes of minute weight variation are imperceptible irregular fill out, internal voids, differences in pot resupply alloys, spru cut voids, minute mold half misalignment, "wings" (on some), etc. There are probably others...

At 500-grains (your boolits) a 2-grain delta on each side of the average is not significant (0.80%) and it is doubtful that you will see any variation in accuracy.

* Average weight

[Harter66]

The thumb rule ,as I understand it , is 1-2% for hunting grade bullets . The smaller the dia the more it matters , 1% is tiny but a half gr on a 50 gr 22 is a big deal if it's missing via a piped HP . 2% is barely an unlubed or extra groove lubed when you're looking at something close to 1-1/4 oz . Seriously is 3 pellets of #6 shot a big deal in an 12 ga game load , probably not . Of course there's the argument that if it's all on one side or the base collapses into a void .......

I've been at this for most of 20 yr now and I have a routine that generally yields enough accuracy that a visual cull of 350+ gr 45 cal bullets from 1,2,&3 cavity moulds , aluminum by Mtn Molds and NOE and iron by Lyman , RCBS , and whoever made that batch of Herters moulds , I run them within 2 gr . That 2 gr is from the 3 cav NOE version of the 458132 at 535 gr . I can't find a discernable difference in the 2 cavities of the 453-350 Mtn Molds over a 10# run at about 1.5 gr . The 45-500 FP gives me 530.4 to 531.2 with the bulk at 530.6-8 . The Lyman 458193 delivers 415+- .2 . I only run about 5# at a time in the big singles mostly because 100 bullets is a lot in a rifle I only shoot 100 or so a yr in a 530+ gr plinker is about as much fun as a root canal in a 7# platform .

Think of the casting process as pouring heat and set a steady pace even if you need an analog clock or metronome at first . It makes a big difference . Mould quality doesn't hurt anything either .

[Pahaska]

Thanks everyone. Apparently I'm guilty of being too picky about bullet weight variance. For a lever action hunting weapon, a receiver sight, shooting under 200yds with big boolits, I'll get lots more "practice" shooting instead of grieving over minor weight differences.

[robg]

i work on 1-2% variation ,good bases are much more important.

[farmbif]

dont know of this relates to elk hunting with a 50 alaskan but I did a bit of a non scientific expierment with 45 colt using mp 4 cavity mold with each cavity having a different hollow point pin in it and one cavity as a solid. I started out with 16 grains 4227 and worked top to 21 grains. at that 21 grains impact was right about the same place no matter if the bullet had large hp pin at about 260 grains or solid at 275 grains. but I was only shooting maybe 75 yards and at trees and boards and stuff no paper targets with a ruler and was standing up shooting with no gun rest. until this time I had always varied my loads according to bullet weight.

[charlie b]

Dropped out of the mold my rifle bullets (.30cal) are usually +/- 0.5gn except for the ones with obvious problems. I sort them into 0.1gn or 0.3gn batches for target shooting.

For reference I weighed some jacketed bullets. Sierra 168gn were +/- 0.1gn. Hornady 167AMax were +/-1.0gn. Yes, that is pretty poor and was why I weighed these. I was getting a lot of fliers with the AMax bullets. When I weighed some 155gn Bergers they are also within 0.1gn.

Do I notice a difference with the cast stuff on target? Yes. If I don't weight sort I get a bit better than 2MOA. The closer I keep the weight the closer I am to 1MOA.

Pistol bullets I don't weigh at all. Just load and shoot.