Effects on accuracy of weighing cast bullets

[MUSTANG]

I have read numerous postings on Cast Boolits and other on line sites spanning several years where questions, postulations, fact, and fantasy have all been represented concerning the issue of individually weighing rifle bullets, and if it is worth the time to do so. I found many pearls of wisdom, some cast before swine so to speak; but no single succinct graphic demonstration concerning the issue. I thought it might be worthwhile to create exactly that demonstration; focused on what the "Average Cast Shooter" might expect and have available, not based on the "Master" Shooter/Caster/Machinist attempting to wring out the last fraction of an inch of accuracy.

To accomplish this I moved forward using the following control factors:

1. Select an "Everyman Rifle" for the test:

In this effort I pulled my first deer rifle from the back of the safe. I received it as a Christmas gift from my Dad back in 1972. It is a Western Field Model 870 in .308 caliber (This rifle is actually a Mossberg 800A, sold under license by Montgomery Ward as a "Western Field").

This rifle is topped off by a Bushnell "Scope Chief" 3X rifle scope.

2. Select an "Everyman Cast Bullet" for the test:

In this case I decided upon the Lee Precision C309-170-F Mold. This is a nominal 170 grain .309 mold. In my application with wheel weights it drops bullets at about 177 grains plus or minus depending on the batch of wheel weights.

Bullets for this test were derived from a casting session where about 250 bullets were cast. All were Water Quenched Wheel Weight Alloy.

3. Use an economical but accurate Scale:

I utilized a 1970's vintage RCBS 5-10 Balance Beam Scale. It has course measurements of 10 grains, with a fine adjustment threaded counter weight supporting measurement in 1/10th of a grain increments.

I have a small Frankford Arsenal digital scale; which I specifically decided Not To Use in this effort. It has a tendency to wander 3/10th to 5/10th a grain for up to 10 seconds when weighing bullets. Additionally, it has the same variation depending on where the bullet is placed o the scale. There is no apparent means of correcting the first variable condition; but I have drawn a set of "Cross Hairs" on the scale to identify the exact center to address the second condition. These variables were why I decided not to use a digital scale.

Bullets for the test were segregated into three groups. The first group was 177 grain (+) or (-) 0.2 grains. A second group of Heavy bullets were selected weighing about 178 grains (+) or (-) 0.3 grains. A third group of light bullets were selected weighing about 176 grains (+) or (-) 0.3 grains.

4. Use a common powder dispenser:

I utilized an RCBS Uniflow Powder Measure I purchased in the mid 1970s. The throw charge was adjusted to 13.7 grains of Unique powder as weighed by the RCBS 5-10 Balance scale. All loads were charged from the RCBS Powder dispenser. I made no further attempt to validate powder charges weights (e.g. I did NOT weigh each charge, but simply thre them through the Powder Dispenser).

5. Use a common set of Reloading Dies:

For this test I selected Lee's RGB (Really Great Buy) .308 dies.

6. Trim all Brass to same length:

For this test I used my Dillion RT1200 Trimmer. I would have preferred to keep with the "Everyman" theme by using my Lee .308 case trimmer, but my rechargeable drill died a few weeks ago and I have not replaced it. Years ago I would use the Lee Case Trimmer in a hand held mode for trimming; but due to hand fatigue and a touch of arthritis, I no longer do so.

7. Use a common Sizing/Lubrication method:

I utilized a Lyman 450 Lubrisizer with .311 sizing dies. For Lube, I selected Carnuba Red.

[pdawg_shooter]

I allow 1% + or - weight variation. No better than I can shoot, I cant find any difference on the target from a bullet weighing 396 or 404gr @ 100 yds.

[MUSTANG]

Below are my shot records from the Baseline Shot Grouping. The form contains the variety of reloading data used. This baseline is using the 177 Grain individually weighed bullets. This grouping represented the largest portion of the bullets from the 250 cast in one session. A smaller number were of greater and lower weight.




A larger Image of the Target is provided to see the shot group fired with the 177Grain weighed bullets. Individual shots are identified on the target in the order they were fired.

[Harter66]

Just an opion not weighing every charge and not match lotting cases can and will make as much maybe more than projectile weight. I own 2 such rifles. Both will shoot whole separate groups w/a case weight varing by as little as 5gn . The other will open groups up from 5 covered w/a nickle to 3" in just a half gr powder.

Your 308 maybe different . I half 1 such wonder rifle also I've not found much it won't shoot well.

Let me be more clear so I don't look crittical w/o base . Consider putting a -.3 boolit in a plus 5 case w/ a plus.3 charge and getting it in the group w/ the +.3 boolit,-5 case and the -2 charge, viola 100 fps and possibly a shot landing over there 3".

[MUSTANG]

The following Shot Record and Larger Graphic of the Shot Target shows my Real World results from an "Extreme Weight Spread" on cast rifle bullets. Note that the "Light Bullets" (shots 1 through 5) produced a wide spread group between the Target Bull down towards the bottom right of the Target. The Heavy Bullets (Shots 6 through 10) grouped tighter, and more in the Bulls Eye area; just as the 177 Grain Baseline Bullets did. In reality, the Heavier Bullets are probably from one cavity; where the 177 Grain bullets were from the other cavity. I have not to date sorted by cavities in this mold, but will do so in the future just to see the spreads between the two cavities.


I believe this produces a pretty graphical representation that sorting bullets by weight is highly important for those shooters seeking accuracy in cast rifle bullets.

It is readily apparent if a shooter sorts cast bullets into light, medium and heavy categories, that light bullets contribute to inaccuracy far more than heavy bullets do. This is most probably due to small voids, and entrained contaminants destabilizing the bullets balance. In this test there was no apparent Key Holing or Commas on the bullet target impacts, but they would more than likely start showing up in the 100yd to 200yd range if the test were repeated at longer distance (except some round would probably miss the target at the longer ranges.

[trixter]

In this case I decided upon the Lee Precision C309-170-F Mold. This is a nominal 170 grain .309 mold. In my application with wheel weights it drops bullets at about 177 grains plus or minus depending on the batch of wheel weights.


I utilized a Lyman 450 Lubrisizer with .311 sizing dies. For Lube, I selected Carnuba Red.

I am a little confused. You are using a .309 mold and sizing with a .311, have you learned something new in casting, or does your mold throw somewhat bigger than advertised? Not trying to be a smarta$$, just curious. My .309 Lee mold throws .3104-5.

[MUSTANG]

Harter 66:

Concur with your thoughts on sorting cases by mfg/date as well as weighing individual powder charges having significant impact on getting the best accuracy. When reloading for shooting HighPower Matches it is part of my regimen to do exactly that.

This particular thesis/test was envisioned to address the specific question of many less experienced cast boolit reloaders as to whether it is worth the time and effort to weigh and separate cast bullets before reloading. I believe that my post at 2:39 graphically demonstrates that weighing and segregating/rejecting each specific bullet can potentially have dramatic impact for the average cast boolit shooter; so it is well worth the time and effort for them to do so.

Perhaps a similar evaluation concerning case sorting, and individual powder charge weighing will be of value in order to graphically demonstrate in those areas the specific improvements to be realized. Specific Graphical demonstration may help those who have limited experience in shooting cast rifle boolits, as compared to simply telling them.

[MUSTANG]

PDAWG:

I believe that you are experiencing less negative impact on similar % variance given that you boolits are 2 and 1/4 times as heavy as my 177Grain projectiles. This coupled with your having a much greater diameter boolit is potentially the reason that the 1% difference in weight does not result in the same increased group sizes I experienced in my test.

[runfiverun]

that gives you a good baseline.
that is a nice uniform group.
can it be improved upon?
maybe, with a bit more judicous load development,case sorting,blah-blah.
you will get to a point where the ammo outclasses the gun.
simple weight sorting a bunch of boolits for that outing/loading session is easy and quick and produces [probably the best] results, followed by powder selecton.
try not weight sorting for a target grade 22 rifle at higher velocities.
your groups will go from sub half inch to whatever.

[pdawg_shooter]

PDAWG:

I believe that you are experiencing less negative impact on similar % variance given that you boolits are 2 and 1/4 times as heavy as my 177Grain projectiles. This coupled with your having a much greater diameter boolit is potentially the reason that the 1% difference in weight does not result in the same increased group sizes I experienced in my test.

I use the same 1% rule on all my cast bullets, 30cal included. A 150gr gets allowed + or - 1.5 grains. I am NOT a bench rester. The only time I use a bench is for sighting in and load testing. Once I have "approved" a load and checked that the velocity is where I want it to be I do all my shooting from field positions.I consider my cast bullet load a good one when it matches or exceeds the accuracy and velocity of a given firearm with jacketed loads. I load mainly to hunt so that is how I practice. Never could figure how to carry my bench when hunting.

[280Ackley]

I have been doing some experimenting doing the same thing. Are you weighing your boolits naked or after they have been lubed and checked? I find that if I sort them naked and then sort them again I end up more uniform results. It appears that the checks and lube are not all that uniform. I find this type of post to be very informative. Thanks for starting it. I have several batches of bullets for different rifles sorted and loaded. I'm waiting for less windy weather to go shoot.

[runfiverun]

gas checks do vary by weight also.
for the target guns they go through the luber twice to insure the groove is completely full.
this also gives me a chance to look them over again.
then they get weight sorted.
for the 223 they go into tenth grain weight variation groups.
for the 30-30 they just get shot if they look good.

[sisiphunter]

Excellent thread goin here..... Just soakin it up...thanks mustang for doin this test and all the others for input.

[pdawg_shooter]

I do not use gas checks, I paper patch and since the patch comes off when the bullet leaves the muzzle it has no effect on bullet weight.