A Question for the Garand Experts

graydog

graydog

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Hi

A good friend of mine had his Garand rebarreled to 308 or 7.62 Nato is you prefer. The job as far as I can see is extremely well done. The front sight is at a perfect 12.00 oclock position. It has been chambered extremely well.

The problem is that it will not cycle properly. It extracts the fired case and ejects it very well but the bolt does not go far enough back to pick up the next shell.

There are no signs of pressure and no rough marks in the cylinder and also no burs show on the fired cases.

The ammo used was factory IVI military.

The gun worked fine with 30-06 before he had it rebarreled. My thoughts on this matter is that it can only be three things

A gas cylinder that is worn to much, a Op Rod that is worn to much or to heavy a spring in the op rod or all of the above.

Can someone out there tell me if making the hole in the end of the barrel that channels the gas into the gas cylinder can be made bigger to fix this problem.

Also any other ides would be appreciated.

Thanks Graydog
 
It could be ammo related
I would (before you do any work to the rifle)
try one of the proven loads that work in the m1a/ norinco m305

it could be the powder ivi uses is not best for your rifle

I have seen loads that are marginal that by adding 0.1 grain of powder work the action in a semi
 
What make of barrel?
.308 barrels should have a larger gas port. I recall seeing the dimension posted here on CGN, but now not sure where it was, likely in one of the multi page building a garand threads.
 
The gas port for a .308 Garand barrel is larger than for a .30-06. I'm out of country and away from my books for a couple more days and can advise the correct port dimension when I return. Short stroking is normally a feature of insufficient gas availability. This can be due to any of a worn piston, internal wear in the gas cyl, fouled or too small gas port, improperly located gas cyl(too far back or fwd) which cuts off gas delivery from the gas port, loose gas plug, cracked internal face on gas plug or gas plug valve fouled so that it doesn't fully close.

IVI ball ammo will generate sufficient gas to cycle the action, but verify that headspace is adequate for a round to chamber fully by op rod spring pressure alone. There is a difference in specs for .308 and 7.62 ball ammo. A minimum headspace .308 Win chamber may not allow the bolt to close
freely on a 7.62 ball round which is a hazardous condition. You can check this by stripping the rifle and the bolt and trial fitting 7.62 ammo to ensure that the stripped bolt (no firing pin or op rod spring) will close on a chambered round by closing the bolt with finger pressure only.
 
Gas hole supposed to be close to 1/10"(.087" to .095". No-Go gauge for a 30-06 gas-port is a #45 drill, #47 is the go gauge.
.) for .308. .1065" was used by the USN. Some commercial barrels haven't been modified correctly.
However, your buddy isn't having extraction issues.
"...operating parts which fail to move fully to the rear (short recoil) are caused by:
1.Valve leak in gas cylinder lock screw. (Valve not fully seated.)
2.Defective operating rod spring.
3.Undersized piston. (Caused by the use of abrasives when cleaning the piston.)
Go here. FM-9-25. Add the W's. Note the need for the provided UN & PW. .biggerhammer.net/manuals/
 
I'm grappling with the exact same issue with my .308 Garand with a new Criterion barrel. I've been stepping up the powder charge and am up to 43.0 grains of H4895 behind a 150gr Hornady FMJBT bullet and it's still not cycling approximately 75pct of the time. However, I tried some rounds that were charged with Varget that I use in my bolt gun and it cycles just fine.

My suggestion - if you are handloading, perhaps try stepping up the powder charge, though I would expect that IVI ammo would cycle.

I was also careful to confirm proper gas port alignment between the barrel port and the gas cylinder. A misalignment here would cost you some gas pressure. Also check gas plug is tight and cycle the built in valve to confirm it's seated.

Hopefully more of the real Garand experts will chime in here soon as well.

Regards,
Peter
 
buster said:
Gas port sizing maybe.
Click to expand...

My thoughts, Have heard of this happening with short AR barrels. I have a .308 Garand project close to completion and am wondering if I will have a similar problem. :confused: Guess firing military ammo might be a fair test, since it should give an acceptable pressure curve.

Grizz
 
We don't know what make or length this .308 barrel is. Gas port specs for a .308/7.62 Garand barrel are .089 to .099. I would only enlarge the gas port after ruling out everything else. There is also a possibility that the exterior barrel OD could be too small which would allow for excessive gas escape. An overly long or kinked op rod spring could also be a factor. Min/max specs on op rod springs for a standard length .30-06 or .308 Garand are 193/4" to 201/4". Avoid the so-called "extra strength" commercial op rod springs.

I've found my 7.62 Garands function very well with IVI or RG military ball ammo. They also work great with handloads using 150-168gr bullets and any of IMR3031, IMR4064, IMR4895, W748, BLC2 or H4895 with charges kept below max per a reputable reloading manual.
 
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