installing regulated gas tube

[redneckdan]

I want to install a regulated gas tube on my del-ton upper. How do I go about doing this? I have machine tool skills.

[RWBlue]

I assume it is as easy as buying a jprifles.com adjustable gas block.
Remove the old gas block
Install new gas block
Fiddle with it until you adjust it for your rounds

I am building my AR from parts. I have not adjusted my gas setting, yet.
My barrel is setup for set screws. Is a del-ton a pinned upper?

[pug]

Well there are regulated gas tubes that you use with a standard gas block and there are regulated gas blocks that you use with a standard gas tube. If you are indeed talking about a gas tube then you must drive out the gas tube roll pin, remove the original gas tube by sliding it backwards then out, install the new regulated gas tube and then drive the gas tube pin back in. It is easier if the gas block has set screws and you can take it off to do the replacement. If you are talking about an adjustable gas block and your del-ton upper uses an OA barrel then you may have to turn the barrel down to .750" in order for the block to fit because oly barrels are .010" larger at the gas block.

[redneckdan]

i installed a regulated gas tube. I wasn't sure whether or not the front sight needed to be removed. I found out on another site that you can remove the tube and not the sight but I removed the front sight anyway to check the gas port size. I was having problems getting a load that would cycle, started with blue dot but my rifle has a carbine position gas port. I'm guessing that the blue dot just burned too fast for adequte port pressure. I switched to H4227 and got 90% last shot hold open at 14grs and 100% last shot hold open at 15grs. This is with a Lee 160gr cast bullet designed for the 7.62x39 I think when I go to heavier boolits at subsonic velocities I'm going to have to go to an even slower powder, I'm guessing in the neighborhood of H335.

[WhisperFan]

Originally Posted by redneckdan

I removed the front sight anyway to check the gas port size.

So what was it?

Originally Posted by redneckdan

I was having problems getting a load that would cycle, started with blue dot but my rifle has a carbine position gas port. I'm guessing that the blue dot just burned too fast for adequte port pressure.

With my rifle, the upper came as a 16" carbine, I cut down the bbl to 10.5" and that caused my problem.

How long is the portion of the barrel between the muzzle and the gas port. What I found was that after I cut down my barrel, the bullet exited the muzzle so soon after passing the gas port that pressure in the gas tube didn't get a chance to cycle the action.

[redneckdan]

the gas port is .120" the barrel is an Oly 16.5" on a del-ton upper.

[WhisperFan]

Originally Posted by redneckdan

the gas port is .120" the barrel is an Oly 16.5" on a del-ton upper.

I was surprised to see that my Model 1 Sales 300/221 upper had a .120" gas port with the 16" bbl as well.

I have gotten good results with my .110" port and pistol length system - of course - I only shoot subsonic 220 gr SMK's too. So - I cannot say that it would work well with supersonics.

[snowhack]

Originally Posted by WhisperFan

So what was it?

With my rifle, the upper came as a 16" carbine, I cut down the bbl to 10.5" and that caused my problem.

How long is the portion of the barrel between the muzzle and the gas port. What I found was that after I cut down my barrel, the bullet exited the muzzle so soon after passing the gas port that pressure in the gas tube didn't get a chance to cycle the action.

Its all about dwell time. (How long the bullet is in the barrel past the gas port) Yours doesn't have enough. You'll need to put the gas block at the pistol location. You probobly knew that though..........