M1a/m1 pressure question ..

1stmar · February 3, 2014, 08:43 PM

So I know I am not supposed to shoot max loads for it may damage the op rod. But how much below max do I need to stay?
Probably going to get the adjustable gas plug, but until then....
FYI
Load is 42 gr 4064 w lc brass and 168smk (308) - I believe this load is ok
Load is 50 gr 4064 w win brass and 168smk (06)- I believe this load is not

But without a pressure gauge or the adjustable plug how do I know when developing other loads.

dmazur · February 3, 2014, 08:59 PM

You need to find "Garand-safe loads", not just step down some % below a max load.

It is all about a pressure curve (specifically, the tail end of that curve and not the peak.)

Powders safe for Garand / M1A type actions have a pressure at the gas port of around 8000 psi, I believe. If you pick the wrong powder, the pressure at the port can generate more force than the operating rod can handle and it is damaged.

You probably won't damage the chamber of a Garand in good condition with any .30-06 load from a reloading manual. But the operating rod may not survive the experiment.

Here's an older discussion about this -

http://thefiringline.com/forums/showthread.php?t=411389

And here's the "old reliable" M1 Garand load info -

http://masterpostemple.bravepages.com/M1load.htm

(Note the typo in the second group...IMR 4094 should be IMR 4064

)

1stmar · February 3, 2014, 09:18 PM

Thinking master po has a typo

IMR 4895 - 47.0 grains
IMR 4094 - 48.0 grains
AA2520 - 47.5 grains
AA2495 - 47.0 grains
H4895 - 47.5 grains
BLC-2 - 49.0 grains
H335 - 47.0 grains
RL-12 - 44.5 grains

Never heard of 4094.;-). Thanks for the link. Looking for a new manual anyway

Jimro · February 3, 2014, 11:39 PM

308 load is ok.

30-06 load is too hot.

Jimro

February 3, 2014, 08:43 PM	#1
1stmar Senior Member Join Date: March 21, 2012 Location: Connecticut Posts: 2,378	M1a/m1 pressure question .. So I know I am not supposed to shoot max loads for it may damage the op rod. But how much below max do I need to stay? Probably going to get the adjustable gas plug, but until then.... FYI Load is 42 gr 4064 w lc brass and 168smk (308) - I believe this load is ok Load is 50 gr 4064 w win brass and 168smk (06)- I believe this load is not But without a pressure gauge or the adjustable plug how do I know when developing other loads.

February 3, 2014, 08:59 PM	#2
dmazur Senior Member Join Date: July 5, 2007 Location: Pacific NW Posts: 1,310	You need to find "Garand-safe loads", not just step down some % below a max load. It is all about a pressure curve (specifically, the tail end of that curve and not the peak.) Powders safe for Garand / M1A type actions have a pressure at the gas port of around 8000 psi, I believe. If you pick the wrong powder, the pressure at the port can generate more force than the operating rod can handle and it is damaged. You probably won't damage the chamber of a Garand in good condition with any .30-06 load from a reloading manual. But the operating rod may not survive the experiment. Here's an older discussion about this - http://thefiringline.com/forums/showthread.php?t=411389 And here's the "old reliable" M1 Garand load info - http://masterpostemple.bravepages.com/M1load.htm (Note the typo in the second group...IMR 4094 should be IMR 4064 ) __________________ .30-06 Springfield: 100 yrs + and still going strong Last edited by dmazur; February 3, 2014 at 09:09 PM. Reason: Added Master Po's data

February 3, 2014, 11:39 PM	#4
Jimro Senior Member Join Date: October 18, 2006 Posts: 7,097	308 load is ok. 30-06 load is too hot. Jimro __________________ Machine guns are awesome until you have to carry one.

February 3, 2014, 09:18 PM	#3
1stmar Senior Member Join Date: March 21, 2012 Location: Connecticut Posts: 2,378	Thinking master po has a typo IMR 4895 - 47.0 grains IMR 4094 - 48.0 grains AA2520 - 47.5 grains AA2495 - 47.0 grains H4895 - 47.5 grains BLC-2 - 49.0 grains H335 - 47.0 grains RL-12 - 44.5 grains Never heard of 4094.;-). Thanks for the link. Looking for a new manual anyway