Question on Drilling Gas Port/Chopping bbl...

[Razorhunter]

Has anyone here ever taken a CHROME LINED rifle length, or midlength gas system bbl, and cut it down to say, an 11.5" SBR length, and then re-drilled the gas port?
I'm trying to determine if this is safe to do, and also if I should attempt it? I mean, does the gas port have to be finish reamed to exact dimension? I would assume so, but just checking.
Also, I think I have read quite a few posts stating that it's perfectly fine to chop a CL'd bbl down, without any fear of harming the CL'ing.
Just want to confirm all of this?

Where do I find gas port sizes?

Finally, if I decide against doing this, who can best handle this job in a timely manner, and get the gas port right the FIRST time? Adco? Who else?
Thanks guys.

[markm]

Also, I think I have read quite a few posts stating that it's perfectly fine to chop a CL'd bbl down, without any fear of harming the CL'ing.
Just want to confirm all of this?

The one opinion that I've read that contradicted this sentiment was a pretty important one. A guy from Noveske said they DO NOT recommend chopping on CL barrels.

Aside from that, you're trying to make the project even more insane by relocating the port.

The advice you'll probably get is to SELL the barrel and buy what you want.

[Col_Crocs]

There are corresponding gas port sizes for different barrel lengths. Id have it done professionally though.
As for the chrome lining, not sure but I think youre GTG. Lets wait for members who know better to be safe. :D

Found this chart somewhere. Cant confirm whether or not the measurements listed are correct though.
http://farm4.static.flickr.com/3312/3639283889_ee25f9d8d7_o.jpg

[Razorhunter]

I don't currently have a bbl that I'm wanting to do the work to.
IF I could find the bbl I want, then I'd buy it, and not even consider this project.
HOWEVER, even if I had the bbl I want, I'd still be interested in finding out IF this can be done, HOW it should be one, and WHO can do it PROPERLY???

For everone's info, the bbl I want is as follows:

1. 11.5" CHF'd, CL'd, - anything LW profile or similar (no heavy bbls of any kind)
OR MAYBE, but less desireable:

2. same as above, but I'd have to do without the CHFing.

As was stated, I'm really wanting a CHF'd bbl, and 11.5" is a necessity. 10.5"/etc will not do.

Unless you know something I don't, I don't even think I've ever seen a 11.5" CHF'd bbl available, and I really don't even know where to find a quality 11.5" CL'd bbl right now, that IS NOT CHF'd... ???
REALLY want the CHF'd though, hence the whole reason for wanting to know the above info...

[DRich]

Has anyone here ever taken a CHROME LINED rifle length, or midlength gas system bbl, and cut it down to say, an 11.5" SBR length, and then re-drilled the gas port?


Yes. I cut down a 20" SP1 barrel to 11.5" and had the gas port re-drilled. Worked like a charm. I've had at least a dozen chrome-lined barrels cut down over the years with no ill effects.

The hard chrome used in rifle bores isn't like the chrome plating on a car bumper. It's not likely to chip or peel unless there was a flaw in the plating process...in which case it would fail whether your cut it or not.

[Razorhunter]

Well, one other thing I've always wanted to confirm.
I am just assuming here, that the FACTORY gas port holes in our CL'd bbls, are drilled BEFORE the CL'ing process, and thus every gas port hole is CHROME LINED, to help fight corrosion, right? (or wrong?) I would really/highly assume this is all correct, but can someone confirm?
Secondly, I'm wondering what ill effects, MIGHT possibly ever arise (depending on how long the bbl's life is, which depends on how often I shoot), due to "gas port erosion"???
I mean, IF I were to drill a NEW gas port hole, in the carbine length location, then the new hole is obviously NOT CL'd.
Does this take away from the bbls (ie - the gas ports) life expectancy???
Thanks for any insight/info...

[spamsammich]

Am I missing something here? Won't BCM 11.5" uppers work for you? I know of at least 2 for sale on this forum.

[Razorhunter]

Yeah, well as mentioned I'm REALLY looking for a CHF'd bbl, and despite that important fact, I will go ahead and mention I'm looking for the BBL ONLY. IOW's, I do not want a FSB installed, where I've got to remove a FSB and have two unnecessary taper pin holes.
I need a BBL only, and it really needs to be a CHF'd bbl only.
I do not wish to have to deal with "covering up" a scuffed up or previously taper pinned area on the GB seat.
I am looking for a nice, FRESH, NEW bbl without any FSB install or taper pin holes...
I suppose I'll go ahead and say I'd really like a CHF'd bbl only too...
I know DD is coming out with a 10.3"ish CHF'd bbl, but I need an 11.5"...
I guess I just assumed you would know the BCM 11.5" uppers were certainly not what I'm after....

[RD62]

Maybe email Centurion Arms (http://centurionarms.com/index.html) and ask if they can do one in house for you??

-RD62

[DRich]

Well, one other thing I've always wanted to confirm.
I am just assuming here, that the FACTORY gas port holes in our CL'd bbls, are drilled BEFORE the CL'ing process, and thus every gas port hole is CHROME LINED, to help fight corrosion, right? (or wrong?) I would really/highly assume this is all correct, but can someone confirm?


I don't believe this is true. I've always been told that drilling the gas port was the last step in manufacturing an AR barrel, so the gas port isn't chrome lined.

I don't see how it could affect barrel life since throat erosion (even on a CHF/chrome-lined barrel) will wear out a barrel long before you'll have to worry about excess wear at the gas port. Just think about the thickness of the barrel at the gas block and how much wear it would take to enlarge the port all the way through. It's a non-issue.

[spamsammich]

the reason I mentioned the BCM uppers is you said that perhaps you could make do without the hammer forging if you could just find a barrel that met your length requirement. Perhaps you could make a special request with Paul at BCM for a barrel minus FSB, if you could settle for something non-hammer forged? And since there are relatively few barrels out there that will meet your criteria, check in with guys like Monty who are offering them. If you can wait a while, maybe see what DD serves up once they get their hammer forge up and running. Your list is so specific, that I doubt this will be an off the shelf part anywhere. It couldn't hurt to ask the sources though. Got any friends at FN?