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11/26/2004 6:15:37 PM EDT
Are barrels generally chrome-lined after the gas ports are drilled, thus chroming the gas port as well as the bore?  I ask because I am interested in cutting a 20" barrel down to 16.5" and opening the gas port up to .110" for optimal reliability.  If the gas ports are chromed with the barrels, and I then open my gas port up (removing the chrome lining) will my gas port suffer any detrimental effects (my primary concern would be faster port erosion)?
11/26/2004 6:48:45 PM EDT
[#1]
VERY good question...

once and a while it happens

sadly i don't know... i would guess not.... but it is a guess...

CALLING ALL TWEAKS AND TROYS
11/26/2004 6:49:20 PM EDT
[#2]
whats the gun look like that your doing it to?  Why are you doing it?

11/26/2004 6:56:08 PM EDT
[#3]

Quoted:
whats the gun look like that your doing it to?  Why are you doing it?




I was thinking of picking up one of the widely available M-16A1 uppers, cutting it to 16" and throwing it on a Cav MkII lower for a simple, lightweight truck gun.
11/26/2004 7:28:51 PM EDT
[#4]
Never did it, but the OD on the barrel might be a bit small for a FSB when you cut a 20"A1 barrel down to 16".

Like I said - I never tried it . . .but just something to check


EDITED TO ADD:  IIRC most barrels a ported after they are chrome lined

11/26/2004 7:53:43 PM EDT
[#5]

Quoted:
Never did it, but the OD on the barrel might be a bit small for a FSB when you cut a 20"A1 barrel down to 16".

Like I said - I never tried it . . .but just something to check


EDITED TO ADD:  IIRC most barrels a ported after they are chrome lined




I would be using the factory FSB, ala Dissipator.
11/26/2004 8:27:29 PM EDT
[#6]
Last time I looked, the chroming process takes place before the port is drilled; at least at the Colt factory.  Even if someone does chrome after drilling, it shouldn't effect your plan to open the hole one bit.
11/27/2004 11:23:32 AM EDT
[#7]

Quoted:

Quoted:
whats the gun look like that your doing it to?  Why are you doing it?




I was thinking of picking up one of the widely available M-16A1 uppers, cutting it to 16" and throwing it on a Cav MkII lower for a simple, lightweight truck gun.



great build... i thought about this a lot myself...  let me know how it turns out!
11/27/2004 6:59:14 PM EDT
[#8]
The port is drilled after chrome lining. A cobalt drill is used to drill the gas port. If you feed very slowly, you won't chip the chrome or flake it away.
Use a NEW cobalt drill bit. I don't know if I would go straight to .110" Start a bit smaller and see if it locks your bolt to the rear after firing one shot through the mag.
11/27/2004 7:09:04 PM EDT
[#9]

Quoted:
The port is drilled after chrome lining. A cobalt drill is used to drill the gas port. If you feed very slowly, you won't chip the chrome or flake it away.
Use a NEW cobalt drill bit. I don't know if I would go straight to .110" Start a bit smaller and see if it locks your bolt to the rear after firing one shot through the mag.



The problem is I don't have the tooling to do it myself, so I'll likely be farming it out to ADCO.  Maybe they will test it for reliability and drill as needed.

For those of you using 20" barrels cut to 16", what do you find to be a reliable gas port diameter?
11/27/2004 9:33:56 PM EDT
[#10]
I didnt know that the gas ports had to opened up for a 16 inch barrel.  Are they opened up on all factory carbine rifles?
11/27/2004 9:49:03 PM EDT
[#11]

Quoted:
I didnt know that the gas ports had to opened up for a 16 inch barrel.  Are they opened up on all factory carbine rifles?



This would be a 16" barrel with a rifle length gas system.  The dwell time would be significantly reduced, requiring more gas to reliably operate the weapon.

11/28/2004 12:51:24 PM EDT
[#12]
troy has his...  seems to be quite reliable from what he said...
11/28/2004 1:13:28 PM EDT
[#13]

Quoted:
troy has his...  seems to be quite reliable from what he said...



Yeah, I was kind of hoping he would weigh in here.
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