NDM-86

.308 Winchester

Gas Tube Mod

The .308 NDM gas tube is not vented, like it's 54R counterpart.
Have read on the internet that it makes a big difference on recoil and how far the brass is ejected.
My results were not very dramatic. With the following mod, the only difference was where the brass landed.
Instead of brass landing at 5 oclock from the rifle, it was 4 oclock. Maybe a slight decrease in recoil.
This is for information only. I am not responsible for any use or misuse of this information.

This is the Number 2/closed position. The gas tube has a detent for this position.

Note the gas tube locking tab is blocked by the gas tube sleeve.

This is the Number 1/open position, there is not a detent for it.

Gas tube removed, in the Number 1 position. Mark the gas tube, this is where the notch
for the detent will be filed. The number 2 position notch is visible at about 7 oclock.

Started the notch with the sharp edge of a triangular file, then finished with a round file.

New notch at 11 oclock.

Sleeve installed, and rotated to the new Number 1 position. The new holes will be drilled inline

with the other vent holes and 0.45 inch from the squared edge of the gas tube.

Tried center punching the gas tube with only one layer of tape. Ended up sliding off the

gas tube sleeve, scratching it. Put 6 layers of tape on the tube and it was enough to

prevent sliding off. The proper size drill bit for the hole through the gas tube is 1mm.

Could not find one locally, so, went with a #60 bit. They are very close in size.

The #60 went through the outer sleeve, but would not go through the gas tubes hard chrome surface.

Ordered a good quality 1mm bit. It went through the gastube with ease.

Right side vent.

Left side vent.

The gas tube sleeve was removed and the 1mm holes were enlarged with a 5/32 bit.

Note the marks on the gas tube where the #60 bits broke while trying to drill.

Other side. Thats better.

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