Max pressure for a Garand?

[heypete]

What is the maximum gas pressure that a Garand can safely handle?

My friend gave me some old 1940's issue .30-06 M2 Armor Piercing rounds that he didn't trust -- the brass was corroded, the primer corrosive, and the state of the powder was unknown. I pulled the bullets, and plan to put them in some of the Korean mil-surp Poon Sang .30-06 casings we shot at the last range session. The brass is being tumbled now.

My Lee manual states that a maximum charge of 47.5 grains of IMR 4064 pushing the 165-grain bullet will generate 57,000psi, while the original M2 AP specs call for 54,000psi. Will this harm anything?

Oddly enough, IMR's website says that the STARTING load for that bullet weight would be 49 grains of 4064, which would generate 50,400psi. This is odd, as their minimum load is higher than Lee's maximum and the pressure differences are great. IMRs maximum load would generate 58,900psi with 52.5gr of 4064.

As this is AP ammo, kinetic energy is important. I'd like to load it as closely to mil-spec as possible in terms of pressure, velocity, etc. but this is a large discrepancy that I cannot account for. Thus, I'm doing a "sanity check" by asking here.
Any information or assistance would be most welcome. For reference, the .30-06 AP is a 165gr flat-base bullet that is significantly longer than the standard ball ammo due to the lighter steel core. See
this site for more information.

Cheers!

 

[Art Eatman]

eclancy willhave the exact numbers...

For general purposes, however, my understanding is that the working pressure for the Garand is 47,000 psi, using 4895 with the M2 Ball bullet (roughly, 153 grains). The pressure curve of this load gives the proper pressure at the gas port and you don't bend the operating rod. (Just one "hot shot" shouldn't hurt, but repetition causes problems.)

In general, the slower burning powders such as 4064 and heavier bullets need a good bit of thought as to both pressure and the curve of pressure vs. time.

Hope this helps,

Art

 

[ClarkEMyers]

Wrong question for my money

What is the maximum gas pressure that a Garand can safely handle?

Wrong question for my money.

For instance I've had bolt gun loads with 200 grain Noslers over maximum amounts of H205 - a discontinued powder once popular to magnumize the .30-'06 - that were well within limits for peak pressure but stressed gas guns and especially cases when primary extraction was rushed with high residual pressures.

I strongly suggest medium powders and medium bullets - there are lots of tested loads in the manuals for gas guns - find a load that references gas guns.

I'd be quite curious to know the intended use for armor piercing loads that can't be met with medium loads of medium powders. In my experience .30-'06 AP is adequate for any of the amusing purposes and most of the serious ones.

 

[Sam]

Most certainly the wrong question.
What will matter for you the most is the residual pressure at the gas port.
This can be taken care of simply. Go to Fulton Armory and get an adjustable gas plug. Properly adjusted this will allow you to fire any 30-06 load in your M1.

I use one lets me shoot heavy bullets with lots of slow powder and no bent OP rod.

Sam

 

[heypete]

No, you misunderstand: I'm not looking for the maximum pressure so I can load rounds right up to the max.

On the contrary, I'm looking to get a medium pressure round -- nothing too low, as that defeats the purpose of AP, but not too high as it would damage the rifle.

According to the data I referenced in my original post, the operating pressure of standard M2 Armor Piercing ammunition was 54,000psi. As I'm sure the government thoroughly tested M2 AP to function normally with Garands and other .30-06 rifles, I'd like to keep loads approximately at that pressure.

However, the disparity between the Lee manual and the IMR website is quite large. I do not wish to cause damage to the rifle, hence my asking the question. I would like to get as close to 54,000psi out of a Greek Service Grade Garand using CCI 200 Long Rifle Primers, IMR 4064 powder, and Poon Sang brass made to M2 Ball spec (I don't know if the brass would be different between Ball and AP...). Are there any resources online (including posters here) that would have a verified load for this?

 

[cracked butt]

My Lee manual states that a maximum charge of 47.5 grains of IMR 4064 pushing the 165-grain bullet will generate 57,000psi, while the original M2 AP specs call for 54,000psi. Will this harm anything?

Nope. That is the load I shoot in matches. If you take a look at the newest edition of Hornady's reloading manual, it gives you maximum safe loads for the M1, and this load is just about at the top end of the range.

The chamber pressure isn't important, as the M1's receiver and bolt are stronger than many bolt actions, but the amount of pressure reaching the gas port is. There is a big difference as you can load a slower burning powder such as IMR 4350 and stay within chamber pressures specified for M2 ball ammo, but there will still be too much pressure at the muzzle end of the barrel which can damage your oprod.

One way you can tell if everything is functioning right- the timing is on, all the parts of the rifle are in spec, and your loads are about right, is that the brass will eject forward at roughly 1 to 2 O'Clock with a clip locked into the rifle.

 

[cracked butt]

To clarify my last post, the load mentioned is close to a maximum load, so work your way up to it and don't use it as a starting point.

 

[heypete]

Hmm. Unfortunately, I only have 40 of the AP bullets, so spending a lot of time working up to the "perfect" load would be somewhat of a pain, not to mention totally nullifying the reason for having these bullets (punching through metal, not paper).

Would it make sense to simply use the minimum load in the Lee manual?

 

[30Cal]

Use load data for 168gr match bullets. If you use IMR4064 and get 2500-2650fps, then you're fine. I get good results with 46.0grs IMR 4064, 168gr HPBT, WLR primer, LC brass, 3.325" OAL.

Did the IMR published load data state what type of brass?? Surplus brass needs 1 or 2 grains less than commercial brass.

 

[Vern Humphrey]

According to the data I referenced in my original post, the operating pressure of standard M2 Armor Piercing ammunition was 54,000psi.

No. They had no way of measuring pressure in PSI when the M2 cartridge was developed. They used a crusher barrel, and estimated pressure by measuring the crushed length of a copper slug -- the proper term would be "CUP" (Copper Units of Pressure), not PSI. There is no formula that allows us to translate CUP into PSI.

For what it's worth, the Hodgdon #26 Manual lists a maximum load of IMR 4895 (47.0 grains) behind a 165-168 grain bullet as developing 50,200 CUP, and a max charge of IMR 4064 (49.0 grains) at 49,100 CUP.

The recommended starting loads in both these powders are the best M1 loads -- 44.0 grains of IMR 4895 (for 37,900 CUP) and 46.0 grains of IMR 4064 (for 41,000 CUP.) The first is my favorite load for the M1 with bullets of this weight.