Gas tube for pistol position???

[mstarling]

Guys,

I have a barrel on order from tp555. Is a 16+" with his three position gas block in stainless steel. Will be threaded 5/8x24 as well.

Have made 300 pcs of brass from LC 97 5.56 cases. They measure 1.365" after necking and the neck size turned out to be 0.330 when a bullet was seated. I think that stands a chance of working.

Flat top upper receiver has been acquired and the door and forward assist have been installed. Upper has M4 feed ramp cuts. Will use a carbine length free floating handguard that measures 1.750 ID. Is supposed to work.

Have a BCG that is know to headspace properly for .223.

Only problem left is the gas tube. I have acquired a carbine length tube. Understand that it has to be shortened. How is this done? (Have reasonable tools including a lathe and mill with a DRO.)

Very much looking forward to playing with this cartridge!

Thanks!



Only remaining issue

[LouBoyd]

Only problem left is the gas tube. I have acquired a carbine length tube. Understand that it has to be shortened. How is this done? (Have reasonable tools including a lathe and mill with a DRO.)

I haven't cut a gas tube. I've bought my pistol length tubes from Model 1 Sales (M1S) and had them make my barrels too. If i needed to cut a gas tube I'd cut off the end which goes to the gas block. Since you have a mill with DRO it shouldn't be difficult to drill the gas port and cross pin hole the right size and in the right place. At least less difficult than trying to re-flare the other end to match the bolt carrier key.

You could buy a pistol gas tube from Model 1 sales. They're only $12. Midwayusa sells the DPMS pistol gas tube for $12.49.
http://www.midwayusa.com/viewproduct/?productnumber=288594
The only question then is if tp555 used the same pistol gas port location as M1S and/or DPMS. It's not necessarily an industry standard. Have you asked for a recommendation for the gas tube from tp555?

[tp555]

Don't have to drill anything if you cut a gas tube for my block.What matters is where the tube is bent.The pistol gas tube is 6.7" stock.The tube is bend closer to the receiver end than on a carbine gas tube.If you can do the bends any gas tube will work.If you have a lathe than you can cut the taper end that goes into the bolt carrier.Just position the bend forward of the gas block.Gas tubes aren't bent perfectly either.They usually require some tweaking.

[LouBoyd]

I didn't understand tp555's explanation so I gave him a call. His company is Paladin Machine Service. Among other things he makes custom AR-15 and AR-10 barrels as well as adjustable gas blocks. His gas block has a brief advertisement with pictures on the Gun Digest website:

http://secure.adpay.com/clicknbuy.aspx?p=2079&itemid=2541516&networkview=False&catid=5500&pcatid=500MS

Because of the square extension the Paladin gas block uses a shorter than normal gas tube which can be easily made just by cutting off the gas block end end of any equal or longer gas tube to get the needed final length. His gas block uses two set screws to hold the gas tube so no re-drilling of the gas tube or a pin or side port is required. I hadn't seen this gas block before so ignore my previous post.

As to how to cut it, just cut it slightly long with a fine tooth hacksaw then file the end to the final length.

[mstarling]

OK ... two potential problems ...

1) bends in the gas tube may not be correct. Actually will have a pistol length and a carbine length tube available. Have a tubing bender for small diameter tubing ... so we can probably work that one out.

and

2) the tube will have to be cut at the gas block end. How about I measure the exposure of the gas tube inside another upper, to a test install of the tube most likely to fit and measure the exposure ... then cut the to be be installed to yield the same exposure.

Sounds like a perfect end on the tube in the block is not necessary.

How perfect does the length of the tube inside the upper have to be? + 0.000 & - 0.010? +0.000 & -0.025"?

Thanks for the help Guys!

Hope to have the stuff all in one place so that the upper can be completed on the day it arrives, and it can be shot the next day. (Can do that from my porch :smile: )

Still need to find some 125 gr NBTs for deer hunting. All of the JSPs I have are probably too hard to hunt with (165 gr CoreLokts and 150, 165, and 180 gr Partitions). Have lots of .308 Ball bullets and a bunch of cast slugs from a Lyman 311291 mold.

(Bow season starts here on Saturday. Have seen a brute of an 8 point around.)

[tp555]

Gas tubes have clearance against the bolt carrier key.I'd go at least 0.1".I made 50AE barrels for Tromix years ago.Tony Rumore wanted the gas block area moved back 3/16" from stock which I did.They worked.So there is some room for slack.

[mstarling]

Ah ... a part with approximate tolerances! That is VERY hopeful.

Last little task I set myself was to build custom scope mounts for 6 Mauser rifles. Had to hold inset Leupold QRW rings so they had recoil shoulders pushing on the front of each ring. Wanted the distances between the rings on each rifle to be the same so that scopes could be swapped between rifles. (Am scope poor and wanted to be able to "borrow" spares for trips.) Came out fine ... look good and work beautifully, but wasn't easy.

This job sounds like it should not be too difficult.

Thanks Guys! I am very appreciative of the help!

[HotLead]

I got my 300/221 bbl from Paladin maschine also. Nobody had pistol length gas tubes for sale at the time so I bought a rifle length tube and formed my own. It is not too difficult but does require some tweaking.