How much leakage is too much leakage ?

[Uprange41]

My BCM with a chopped A2 leaks enough to darken the bottom area of the light that sits directly above it, I imagine because of the space between the gas block and the shoulder that the handguard cap used to fill... It's been reliable in 1.5k since the chop, though, so I'm not sweating it.

[lysander]

Comparison of a Theoretical and Experimental Study of the Gas System in the M16A1 Rifle

Page 30 through 33, Figures 13 and 14

E. Effect of Varying Leakage Area

Leakage in the gas system takes place, for the most part, around the gas tube in the carrier key and around the rear of the bolt in the carrier. The combined leakage area of the instrumented gun used in this study was 0.00108 in^2, except for this particular test. A tube was chosen that provided a leakage area of 0.00099 in^2 and, by reducing
the outside diameter, provided 0.00150 in^2 and 000284 in^2. The areas used for the calculations ranged from zero to 0.002845 in.

The theoretical and measured pressure curves are plotted in Figure 13. Larger leakage areas result in lower cavity pressures. Ratios of measured and calculated quantities are plotted versus the ratio of varied leakage area to the nominal leakage area in Figure 14. The curves indicate that variations in leakage area within the range investigated have little effect on weapon functioning.

They tripled the leakage area and nothing went wrong.

The leakage has to be quite large in order to start effecting functioning.

[Colt guy]

Comparison of a Theoretical and Experimental Study of the Gas System in the M16A1 Rifle

Page 30 through 33, Figures 13 and 14





They tripled the leakage area and nothing went wrong.

The leakage has to be quite large in order to start effecting functioning.

Very interesting thanks for posting

[BufordTJustice]

OP, Lysander hit the nail on the head. However, if it bothers you, AND if you have a hydraulic press to get the gas block off later if you need to, you can disassemble and apply green loctite 620 sleeve retaining compound between the circumference of the gas block journal and the gas block.

A) you likely won't even need a pin or set screws (but still use them) and B) you will have ZERO gas leakage.

I can't emphasize enough that this should be basically considered permanent. It's an absolute bitch to remove.

But my barrel is so pretty now...

[Clint]

Leakage rate is related to fit and clearances between the gas block, barrel and gas tube.

The pictures show more gas leakage than I like to see.

It's not concerning, but personally I would correct any gas block found to be leaking that much.

[BufordTJustice]

Leakage rate is related to fit and clearances between the gas block, barrel and gas tube.

The pictures show more gas leakage than I like to see.

It's not concerning, but personally I would correct any gas block found to be leaking that much.

Clint, I've used one and installed several of your BRT blocks for friends and they all fit very tight with precious little leakage. Barely visible, in fact.

Fit is, indeed, everything.

[LRRPF52]

I personally like a sealed gas block and tube, especially on a .308 build.

I've seen gas leakage cause short stroke malf's, but the main culprit was an aluminum gas block.

I've also seen new guns not carbon filled yet short stroke. On my builds, it never happens, and I attribute that partially to a sealed system up front. I use Red on the block after test fitting, and Blue on the gas tube in the block.









If anyone ever sees these types of gas blocks, remove them from the gun, chuck them, scrap them, whatever it takes to get them as far from the gun as possible. They are garbage, 6061 at best, super soft aluminum that really isn't worthy of consideration for a firearms part, but they sure cut machine time down because they cut like soap.