View Full Version : Garand 170 Grs. Federal

redwing 40
November 10, 2008, 10:25 PM
Will firing the 170 Grs. Federal Sporting Ammo harm the OP rods on my M1? I have fired the Ammo in the past with out problems. A fellow shooter told me that firing any thing other than the 150 Grs. service Ammo would harm the OP rods.:confused:

November 10, 2008, 10:52 PM
Your friend is wrong. I have been shooting 180 SMKs and now 175 SMKs in my M1, in matches for 25 years and never hurt my op rod.

I shot tons of 173s (M72 30 cal Match) when I was shooting for the NG. When I first started running sniper schools for the guard we had M1C/Ds and all we shot was the M72s (173 gr Match). Our Air Guard teams were issued M1 NM rifles, I furnish them with the M72s, also zero problems.

To give you an example, the M72 30 cal NM, was loaded with the 173 bullet, 50 grns of IMR 4895, at a chamber pressure of 50,000 psi

The M2 30 cal ball is loaded with 150 gn bullet, same 50 grns of IMR 4895 at 50,000 PSI.

The Armor Piercing M2 for the M1 was loaded at 54,000 psi.

Per TM 43-0001-27.

I wouldnt shoot anything over the 180s in the M1 though.

November 10, 2008, 10:56 PM
From what I understand, that damage can either be a gradual thing from extended battering- or a pretty much all of a sudden kinda thing. That's why they sell those adjustable gas plugs for $35 to $40. I've always heard the same thing as you, but, I still have some 173gr match ammo my ex-pap-in-law kept from his Air Forse shooting team days. I know they even put some science and a fair degree of thought into load development back in the 50's and 60's, but I'm certain the change in powders, pressure, and velocities of today's commercial ammo is what makes it a no-no in Garands.

redwing 40
November 10, 2008, 10:58 PM
Thanks for your very complete answer. I all so live in Wyoming Sw part.

November 10, 2008, 11:05 PM
Thanks for your very complete answer. I all so live in Wyoming Sw part

Good deal, now far for Lander. They have some great HP matches there for you to shoot your garand. Great range, with gongs out to 1400 yards. Perfect place to test you loads for your garand.

Hope to see you at one of their matches next summer.

November 11, 2008, 10:14 AM
Will firing the 170 Grs. Federal Sporting Ammo harm the OP rods on my M1? I have fired the Ammo in the past with out problems.

It all depends on the gas port pressure that the ammunition produces. You have to call Federal to find out.

GI ammunition had to meet velocity, breech pressure, and gas port pressures. (And other criteria)

Mind you, your rifle was put into service in 1936 with ammunition that is considered mild by today's standards.

Your Garand gas system is not self compensating. You put ammunition in it that is too high of a port pressure the mechanism will open faster/sooner than for what it was designed. Rapid acceleration will bend the operating rod. Rapid acceleration of the mechanism will slam/bang things around, cause misfeeds, op rod dismounts, all sorts of fun. And beat up your mechanism.

The heaviest bullet weight used by the military was 174 FMJBT. Pressures were NTE 50,000 cup, velocity was 2650 fps at 78 fps. Port pressure, I forget. So pressures were in the 40 Kpsia. Most modern ammunition is exceeds this and will produce higher port pressure.

The NRA had an article, decades ago, where a guy developed heavy bullet loads in the Garand. The weights were at least up to 190 grains. And the loads were slow. To keep port pressures down.

Hornaday makes 30-06 compatible ammunition. http://www.hornady.com/story.php?s=775 That is the only commerical ammunition that I am aware won't beat up your rifle.

I load my own. My load is a 168 SMK/Hornady match/Nosler Match 47.0 grs IMR 4895 LC CCI #34 OAL NTE 3.30" I have shot 150 SMK 47.5 grs IMR 4895 LC CCI#34. Cutting either load to 46 grs won't hurt a thing.

redwing 40
November 11, 2008, 03:34 PM
Yes, on Lander shot there back in the 1970s. I reload for my Garands have 2 one Splfd and a Korean issue H&R. A friend of mine closed his gun shop and he gave me a case of Federal ammo. I can always shoot it in my 03A3.:)

November 11, 2008, 03:53 PM
And, of course, there is always the adjustable gas nut as an option. These are made by McCann and Schuster.

Here's a link to McCann Industries -


The idea is, you start with the nut adjusted wide open (Schuster) or with the largest orifice installed (McCann), then adjust smaller until the rifle's action cycles reliably. This is usually done with a single round, and a check to see if the action locked open correctly. If it will do this, and nothing else is wrong, it will probably feed properly from the clip.

You have to do this every time you change loads, but it will permit using other than military spec ammo in the Garand. (Within reason...)

I'm using 46 gr of Varget with 150gr FMJ bullets. Some have told me this is just fine without messing with an adjustable gas nut, but it isn't H4895 so I'm not taking any chances. :)

The important thing to realize, IMO, is that it isn't as simple as bullet weight. It's a pressure curve you have to worry about, so powder burn rate is also part of the problem. The adjustable gas nut is a mechanical solution that permits safe operation without actually knowing what the pressure curve is.

November 11, 2008, 03:54 PM
The issue isn't with bullet weight, but rather with port pressure; the pressure of the burned powder gases in the barrel when the bullet passes the gas port. Some heavy factory loads are loaded using slow-burning powders which result in significantly higher pressure at the time the bullet reaches the gas port than the "medium" burn rate powders used in milspec ammko and most 150-165gr factory loads. Having higher pressure gas bled into the gas system than it was designed for can unnecessarily batter the action and bend the oprod.

You can use any weight bullet you want in a Garand if you're handloading using powders compatible with the gas system, but many heavy factory loads or handloads with slow-burning powders will damage the rifle.