Cases: Milsup vs Commercial

D.B. Cooper · Feb 15, 2020

Okay. SO I screwed up. About half the brass I have amassed for my Garand is Korean milsurp (PS 82 head stamp-I got the ammo cheap), and about half is commercial (mostly PPU with some mixed range pick-ups.)

I didn't realize the significance of this until this week when I started prepping cases and had to go buy a a primer pocket reamer for the PS 82 brass.

So here are my concerns:

Case volume. It's pretty well known that Lake City Arsenal brass is thicker, resulting in less internal volume than commercial brass, which results in higher pressure. Master Po's website suggest dropping starting charges by 2 grains to compensate. No problem there. However...

1.) Does anyone know if PS 82 is even subject to this rule. (The stuff was made in Pusan at the same factory as the commercial PMC branded ammo.) How can I verify? (Should I even bother?)

2.) It looks as though I'll have to either a.)work up two completely different loads for the two types of brass, or b.) stash the commercial brass and use only mil-surp brass until it's all used up and gone. What would be the effects on group size and point of aim/point impact if I used the same powder charge and bullet in both cases? (Significant enough to worry about or no?)

Charlie98 · Feb 15, 2020

Case volume is measured by cc's of water... if you have the ability to measure that. You could also weigh a sample lot (say 5 each) of cases against each other... it wouldn't be precise, but it would give you an idea.

Case volume variances are a bit less than something like .308/7.62mm, where the case volume is reduced, already, compared to the .30-06. Further, unless you are running your loads near max, I doubt there is a significant difference between commercial and surplus .30-06 brass... but that's my opinion, I don't have any milsurp .30-06 brass to see. I do know it is not an issue in .223/5.56mm brass, and I find it unlikely in .30-06... but I may be wrong.

AJC1 · Feb 15, 2020

I think if you're running competitively that you should shoot only one headstamp if possible. Anything you can do to reduce variability will help. I know nothing about the headstamp you referenced or how consistent they are. Your shooting skill and level of competition matters a lot. If your always in second place at national level events I would just buy a big lot of starline and bench the rest for practice. If your back of the pack and newer to the sport on a shoe string budget, sort caces into lots by weight and headstamp. Mark your competition batch with a dot on the head for identification.

Vkt · Feb 15, 2020

Prvi brass is thicker for commercial brass it might not vary to much.

PWC · Feb 15, 2020

Weigh samples of each (comm'l and mil)

No need for special measuring set up or math conversions. Unless you live in CA, where plastic straws are outlawed, get a clear plastic straw and plug one end with wax or hot glue or...... Fill each case, of one type, to the case mouth and dump into the straw; mark it. Then do the same with the other case type; the result should answer your question.

Who cares how many grains, grams, or furlongs-per-fortnight.

Shimitup · Feb 15, 2020

Just set your measure to charge the Lake City right to the top then charge other cases at that setting for comparison. That will tell you exactly what you want to know with stuff you already have. True what PWC said, and a skinny straw will amplify variation.

Laphroaig · Feb 16, 2020

I always segregate my brass by headstamp, just because. If you are concerned about the difference in your brass, you can answer your question by measuring the internal volume. I'd just weigh a case dry, fill it with water, and subtract. Just speaking from memory. an -06 case holds about 65 grains of water. If they are within a grain or two, I wouldn't worry too much. More than that, maybe you'd want to investigate.

A Garand is a Garand, not a bench rest rifle. I've heard other people say that different brass results in a different zero, but I've never noticed a big difference. Adjusting a click or two during sight in is pretty common for me, and might be other factors beyond my ammo.

rdnktrkr · Feb 16, 2020

I have 4 cans of the Korean ammo and 2 cans from 60s, I've not seen any difference when shooting the Garand out to 200yrds at 4" steel, I like reloading 125gr bullets for a light shooting 100yrds round.

Dudedog · Feb 18, 2020

Weigh one empty case of each flavor. If you have a digital set it to grams, if you have a beam you will have to do a little math to convert grains to grams
Fill cases with water, reweigh.
1cc of water in general is assumed to weigh 1 gram.
ta da, case volume in cc.

1 grain = .0647989 grams or 1 gram = 15.4324 grains
Since a decent reloading scale should be accurate to at least .1 grains or better you should be able to get a pretty good number on case volume.

entropy · Feb 18, 2020

D.B. Cooper said:
1.) Does anyone know if PS 82 is even subject to this rule. (The stuff was made in Pusan at the same factory as the commercial PMC branded ammo.) How can I verify? (Should I even bother?)

It was made for both rifles and machine guns (M1917 & M1919), so it will be thicker than even PPU, but if you drop your loads down as planned, shouldn't be a problem. Load competition loads in your military brass, and 'plinkers' in the commercial.

cfullgraf · Feb 18, 2020

When I was shooting competition for the Garand, I settled on one headstamp cases for my competition ammunition. It just minimized one factor.

For general plinking ammunition, I do not worry about the headstamp. I figure my reloads are as consistent as military surplus ammunition.

So, I guess it comes down to0 what your plans are for the ammunition and how it will be shot.

Cases: Milsup vs Commercial

D.B. Cooper

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Charlie98

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AJC1

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Vkt

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PWC

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Shimitup

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Laphroaig

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rdnktrkr

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Dudedog

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entropy

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cfullgraf

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