Gas system for 30-06 Tanker with BM59 op-rod

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08-25-2020, 11:21 PM
s11033

Gas system for 30-06 Tanker with BM59 op-rod

Hey guys,

I'm building a tanker-style Garand in 30-06 with a straight BM59 op-rod. I want it to be able to fire Garand-spec loads as well as modern/heavy/commercial/hunting ammo. Ideally I'd like to be able to switch ammunition without having to fiddle with my gas system. I will have to size my gas port for the lower-port pressure ammo to ensure reliability.

Will the higher-port pressure loads require the use of an adjustable gas plug? My thinking is that since the BM59 op-rod is straight, it is unlikely to bend because it doesn't have the failure points that the M1 op-rod does. Being shorter probably helps as well.

It would help me if I knew where M1 op-rods tend to bend when they get damaged from firing heavy commercial ammo. If it's at the rear where it hits the receiver, or the bar where it extends rearward to the bolt, I'm probably SOL. If it's along the tubular shaft, then I expect that it won't be an issue with the straight op-rod.

If you guys think the higher port pressure will be an issue, then I might try milling some vent ports in the gas cylinder like the AK's gas tube has. The idea would be to bleed off some of the excess pressure instead of having to change the settings on an adjustable plug.

I could also try a high-volume gas plug, but I have to learn more about how those work to decide whether they'd prevent issues.

Thanks in advance!
09-09-2021, 11:39 PM
gman366

If you used the straight op rod. (It is shorter than the tanker op rod, I don know how you do it. High pressure ammo will drive the op rod rearward at the same rate, regardless of the length of the op rod. If you are going to use higher pressure ammo, an adjustable gas plug is a must. Drilling holes in the gas cylinder will work for higher pressure ammo, but will not work with 150 grain bullet ammo.
I would strongly recommend the adjustable gas plug. A high pressure round could cause the op rod to come out & come at your face like a piece of shrapnel.
Several years ago, a guy named Glen who worked at Sarco fired an Enfield with a high pressure round, I the barrel/receiver blew up, causing severs injury his head. Unfortunately, he bled to death before the ambulance arrived.
09-24-2021, 05:04 AM
musketjon

You can't use a straight op rod. The rod needs the bends to fit the contours of the barrel. The gas cylinder in the M1 does not as low as the M14 does. The BM59's rod is not straight.
Jon
09-27-2021, 12:41 PM
blfuller

If you use the straight BM59 op rod you will need to use the BM59 gas cylinder as well. Your barrel would need to be modified to accept the BM59 gas cylinder.
11-14-2021, 11:54 AM
gman366

BM59 op rod

Quote:

Originally Posted by s11033

Hey guys,

I'm building a tanker-style Garand in 30-06 with a straight BM59 op-rod. I want it to be able to fire Garand-spec loads as well as modern/heavy/commercial/hunting ammo. Ideally I'd like to be able to switch ammunition without having to fiddle with my gas system. I will have to size my gas port for the lower-port pressure ammo to ensure reliability.

Will the higher-port pressure loads require the use of an adjustable gas plug? My thinking is that since the BM59 op-rod is straight, it is unlikely to bend because it doesn't have the failure points that the M1 op-rod does. Being shorter probably helps as well.

It would help me if I knew where M1 op-rods tend to bend when they get damaged from firing heavy commercial ammo. If it's at the rear where it hits the receiver, or the bar where it extends rearward to the bolt, I'm probably SOL. If it's along the tubular shaft, then I expect that it won't be an issue with the straight op-rod.

If you guys think the higher port pressure will be an issue, then I might try milling some vent ports in the gas cylinder like the AK's gas tube has. The idea would be to bleed off some of the excess pressure instead of having to change the settings on an adjustable plug.

I could also try a high-volume gas plug, but I have to learn more about how those work to decide whether they'd prevent issues.

Thanks in advance!

There is some confusion concerning BM59's. The BM59E Model, (as sold by Sarco) was modified from standard Garands by cutting the barrel, op rod (bent),spring, & rear handguard down 1/2 inch. (If they had just made new barrels in 7.62 NATO, they could have saved a lot of work converting the parts, & as a result they mucked up the whole supply system with 2 different size parts.
The later model, the ALPINE , (Kit sold by Numrich) (Which the sellers of this type failed to mention,)Paratrooper, & Nigeria types was built from scratch, & had different components, such as a bipod & tricompensator. It had a drop-down gas cylinder & the op rod is 17 inches & straight. The stock is the same size as the Garand. The tanker op rod is 18 inches. The Alpine op rod will not fit unless you get Shuff to cut the tanker model down to the correct size. It would be nice, but is it worth it?