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Posted: 12/14/2014 4:26:51 AM EST
Does a .308 M1 need an adjustable gas port?

I've read that for the 30/06 version, you should have one, as commerical 30/06 is hotter than military ammo, and you need to be able to bleed off some of the gas to keep from damaging the op rod.

Now, with .308 ammo being less powerful than even military 30/06, is there any reason you need an adjustable gas port in a .308 version? I'd think not.

I know they can help tune in accuracy, just wondering if there are needed to prevent damage when firing modern commerical ammo.

Thanks.
Link Posted: 12/14/2014 12:28:40 PM EST
The .308 M1 that I have has shot GI 7.62 just fine as is. That includes M852 (168 gr Sierra), M80 Ball (150 gr), M118 Match (173 gr), M118SB (173 gr), M118LR (175 gr), and all my .308 handholds (168 gr, 175 gr, and 180 gr). Never had a gas or oprod problem AND it is very accurate. What it does not have is the useless magazine well spacer. If you screw up and load a .30-06, the bolt stops 0.40" from closing and you have to retract the bolt and load the correct ammo.
Link Posted: 12/15/2014 7:20:41 PM EST
My .308 Garand runs great without one.
Link Posted: 12/16/2014 7:01:22 AM EST
Link Posted: 12/18/2014 4:19:16 AM EST
Interesting. Didn't know the 762 and 30/06 military rounds were the same.

What are the specs of that load, bullet weight and velocity?

Thanks,
Link Posted: 12/18/2014 7:03:50 AM EST
Link Posted: 12/19/2014 12:45:08 PM EST
Just to be clear .............. the powders used between M80 and M2 ball were different.

Link Posted: 12/19/2014 3:40:24 PM EST
[Last Edit: 12/19/2014 3:41:27 PM EST by Sailormilan2]
The powders are different, and since there is less powder in the .308/7.62, there less pressure down stream from the chamber. Enough of a pressure difference, that the gas port size is larger on the .308/7.62, to allow proper functioning, than on a 30-06.
Link Posted: 12/19/2014 7:42:48 PM EST
Shoot it first before buying an adjustable gas nut. I have owned four M1 Garands in .308 in my lifetime. One ejected the empty cases like an AK-47. It could have used an adjustable gas system, the others not so much.

This all depends on the gas port size, powder type and charge weight, bullet, gas system fit, brass being used, and if the rifle has already been broken in well.
Link Posted: 1/17/2015 7:25:41 PM EST
For a toy or serious work? Toy no... trying to get serious then yes
Link Posted: 1/18/2015 9:10:10 AM EST
[Last Edit: 1/18/2015 9:23:29 AM EST by Sailormilan2]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Chuck:
7.72mm NATO and .30.06 both shoot a 30 caliber 147gr bullet (plus or minus) at 2750fps (plus or minus). Literally identical performance.

In original loading there were insignificant differences in the actual projectile and different powders were used. M80 and M59 Ball are seated deeper their cases than M2 Ball (.30-06). Cannelure in a different location. No one is producing M2 Ball that I'm aware of and commercial loadings may actually use identical bullets or ANY bullet since there's no standard.

As if the above isn't enough trivia [:] : .30-06 is technically a misnomer as it hasn't been produced since WW1. Real .30-06 (Cartridge, Ball, Caliber 30, Model of 1906) was replaced in the early 1930s with M1 Ball to correct problems encountered during WW1 when the cartridge failed to shoot to the ranges calculated. This was the era of indirect machine gun fire and we were not getting the advertised range. M1 Ball was significantly more powerful but proved too powerful for shooting, mainly on National Guard ranges where the bullets shot beyond the safety range fans, and was replaced with M2 Ball which reflected the ballistics of the original cartridge.

-- Chuck
View Quote


While most of this is correct, let me add a couple of things. M1 Ball was not "too powerful". But, with the change from the lighter, flat based Cal, 30 1906 round to the longer, heavier, bolt tailed M1 Ball round came increased range due to better ballistics(streamlining) of the bullet.
To fix that, the Military replaced the heavy M1 Ball bullet with a lighter bullet similar to the original 1906 bullet. However, to make the down range ballistics similar to the M2 AP round, they had to increase the powder charge. So, what they got was a lighter, faster bullet with less range. During WW2, most of the ammo used in Europe by US troops was M2 AP.
The M1 Garand was designed around the M1 "Ball" round.

30-06 1906.........................................150 gr...............2700 fps/muzzle..................2640 fps/78 feet
M1........................................................174.5 gr............2647 fps/muzzle..................2600 fps/78 feet
M2 Ball.................................................152 gr................2895 fps/muzzle.................2740 fps/78 fps
M2 AP...................................................168.5 gr............2775 fps/muzzle.................2715 fps/78 feet

The Author, Jim Thompson, has claimed that the .308Win/7.62NATO case is too small be be able to put enough slow burning powders in to hurt a Garand's op rod. I really can't say if that is correct or not, just passing on info.
Link Posted: 1/18/2015 10:26:28 AM EST
[Last Edit: 1/18/2015 10:27:44 AM EST by dalle0001]
If you use standard loads you should be fine. Probably no more than 168gr should and ought to be alright.

An adjustable gas plug couldn't hurt though. I believe one of the advertisement is that it can extend the life of your rifle because there's less stress on the piston. Remember a garand isn't like a m1a. The gas push the oprod directly rather than through a secondary piston. So if there's nothing controlling that gas escaping, it could in fact bend the oprod. Chances are it wouldn't happen but anything that can reduce that to just the bare minimum is a good thing.

On a tanker garand, it's a must since the oprod is already bent and getting a new one can be a "custom job" so protecting that oprod is a must.
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