Modern Sporter - Build Discussions

[Munkey1973]

Since both of you have TNA gas tube... I wonder if the tube seals gas enough at the gas key interface.

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[Ryang5177]

Seems like an undergas issue forsure for both cases

[twinge6805]

Since both of you have TNA gas tube... I wonder if the tube seals gas enough at the gas key interface.

This is something I never thought of. As a test I took everything (firing pin, cam pin and bolt) off the BCG. When I slide it forward into the upper receiver and onto the gas tube there is no extra resistance when the gas tube begins to slide into the gas key. Is this normal?
Also though maybe checking the length the tube protrudes into the receiver might be a good idea so I took this picture:

Does the length look correct?

EDIT: I also note that there is a lot of carbon on the gas tube closest to the front of the receiver, but very little where it would be inside the gas key. Is this normal?

[ColinD]

I had the same issue with the bolt carrier being caught on the bolt catch. I replaced the buffer tube with an enhanced one so that I could unthread it a couple turns while still being able to retain the detent. Before I changed the buffer tube, when I pulled the bolt back with the charging handle there was only about a 1/8” gap between the catch and bolt face. With the new tube threaded out a bit, I’m getting about 1/4”+. I think that made all the difference.

Like others suggested, try a better quality GB and make sure it is perfectly aligned.

I think the wear on the top of the lower receiver caused from the charging handle is normal for a MS. All of mine have it as well, I’m using radian and Geissele handles.

[PinaKaleada]

Anyone have a Geissele handguard wrench I can borrow in the GTA? Would even rent it! PM me!

[DILLIGAF]

CH wear is normal. PWS Buffer tubes are the sh!t for the MS.

[G.Mitchell]

CH wear is normal. PWS Buffer tubes are the sh!t for the MS.

That is what I am going with on my build!

[Munkey1973]

Seems like an undergas issue forsure for both cases

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[UR2X3M4ME]

Gas system and buffer tube length have nothing in common. Don't get caught up on carbine and rifle.

A carbine buffer tube is the length of the buffer tube and usually uses and adjustable stock of some kind. Rifle length buffer tubes dont use adjustable stocks and are smooth. The stock bolts to the tube at the back of it and is used for stocks like the a2 or fixed stocks.

Rifle length gas system is a term for how far away the gas port is from the upper. Same as carbine, mid length and pistol length. And to really screw with things someone invented an intermediate lenght and a rifle plus 1 or 2 or 3" system.

Rifle length gas systems are usually found on barrels longer than 16 inches. Carbine length is for barrels shorter than that. Midlength even shorter and pistol is the shortest.

A longer gas system increases the time the case spends in the chamber after the bullet leaves the muzzle. Shorter systems decrease this and if the system is to short the rifle will try to extract the case before the brass has contracted enough to allow it to extract.

Buffer weights can be switched out to "time" the rifle without using and adjustablegas block. If your rifle is over gassed with a carbine weight you go up to h1 weight. Timing is the ejection pattern of the cases. 3-4 o'clock is properly gassed.

I should add that carbine and rifle length buffers are differnt too. The rifle length tube needs a longer buffer to stop the BCG from hitting the buffer tube. You can't use a rifle length buffer in a carbine tube and you can't use a carbine length buffer in a rifle length tube. These are the only rifle and carbine things that need to match.

If you have a rifle length buffer and buffer tube use it on your MS with the proper buffer and put that 18.6" barrel on the with the rifle length gas system and shoot away. Same goes for a carbine buffer tube and buffer.

The gas system has NO correlation to your buffer tube

Thanks Greg O.
Got that loud and clear. I truly appreciate you taking the time to explain. Will fit carbine tube, spring and buffer assemblies already on hand "as is". Only if the ejection pattern hints toward timing issues, then I will consider buffer weight adjustment.
Now just waiting on ATRS to deliver the magic bits. With luck it will be under the tree for Xmas.

[ColinD]

CH wear is normal. PWS Buffer tubes are the sh!t for the MS.

I can never see the pictures you post. Not sure why that is, but every time I feel like I’m missing out.