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9/22/2017 12:11:25 AM
Posted: 3/25/2006 5:08:41 PM EDT
Hey all,
Here's the deal. I have a 20" Colt (RO901) upper on my A4-gery. I have two other 20" rifles (an A2 and a DCM type rifle) and I was thinking of having it cut down (and having the gas port opened up). BUT, I've heard that there may be reliability issues with that kind of set up.

So to all of you builders and "pros", would you trust a 20" that has been cut down (by ADCO/KKF/etc) and had the gas port opened up for HD, "SHTF", classes and such?

I really want a cabine length with the longer gas system but with a permanent A2 FSB (in the "Dissy" position). I'm not aware of anyone who makes a middy with the 1:7, 5.56, Chrome, with the A2 in dissy position. I just don't care for detachable or flip up front BUIS's.

Or would I just be better off selling the Colt upper as is and getting something that won't compromise reliability?

Thanks, this has been buggin' me for some time.
Link Posted: 3/25/2006 6:16:20 PM EDT
I had some SP1 barrels cut down by KKF, and they all have run well. One was a little quirky with a low pressure specialty load, but otherwise fine. I was confident in their reliability one it was proven with chosen ammo.

Link Posted: 3/25/2006 7:24:31 PM EDT
[Last Edit: 3/25/2006 7:25:14 PM EDT by rebby]
I'd probably sell it and buy another. If I really wanted it cut down, I'd have JP Rifles do it.
Link Posted: 3/25/2006 8:24:04 PM EDT

Originally Posted By Trumpet:
I really want a cabine length with the longer gas system but with a permanent A2 FSB (in the "Dissy" position). I'm not aware of anyone who makes a middy with the 1:7, 5.56, Chrome, with the A2 in dissy position. I just don't care for detachable or flip up front BUIS's.



I think CMMG does Midlength-gas Dissy-style barrels...check out their "M10M w/Mid-Length Gas System" barrels.

And no, I do not trust my chopped 20 for serious work. I am going to keep it as a tinker rifle, and maybe someday I'll get it running 100%, but for now it's just too finicky about ammo and cleanliness.

--Josh
Link Posted: 3/29/2006 6:19:51 PM EDT
I have a KKF chopped 20 that will run standard 55gr .223 and 5.56 just fine. It will not at all cycle the Winchester 40gr jhp and is 50/50 with Wolf. Mine may not be the best example of Kurt's work because it was chopped so far back that the A3 Tac brake is directly in front of the A2 FSB. (Who knows why the original owner asked for it that way). To answer your question, I would not trust the gun for SHTF where I may have to scrounge ammo, but for situations where the ammo is known quantity I could live with it. The 50/50 thing with wolf is handy for practicing malfunction clearance drills
Link Posted: 3/30/2006 11:06:29 PM EDT
Link Posted: 3/31/2006 5:22:12 AM EDT
[Last Edit: 3/31/2006 5:24:07 AM EDT by Onslaught]

Originally Posted By AR15barrels:
I don't recommend going shorter than 17" barrel length on the rifle length gas system.
More info here:how it works


With that kind of backing, I'd trust a 20" cut to 17" 100%, especially if Randall was the cutter. Plus, since "classes and such" should come before "HD, SHTF" etc. then you will know for sure how it handles after a class or two. (I'd try to take a spare just in case).

If you wanted a lightweight, then this is a good option. Those CMMG barrels are medium contour. They're nice, but they'll be heavier than a chopped 20".

Zak_Smith also has a 17" carbine with rifle length gas system, and it seems to run just fine.

One of these days, I will probably replace my "wife and kids" 16" superlight with a chopped 20" gub-ment profile for the softer recoil, longer sight radius, and less "barrel to burn ya" area.
Link Posted: 3/31/2006 6:18:53 AM EDT
The reliability of a "cut-down" barrel would all depend on your gunsmith. If he is good, then he will be able to make your carbine run without any reliability issues.

I have a 10.5" cut down from a 20". I have ran more that a thousand rounds through it without any reliability issues.

IMO.
Link Posted: 3/31/2006 6:40:40 AM EDT
Link Posted: 3/31/2006 9:11:41 AM EDT
[Last Edit: 3/31/2006 9:12:42 AM EDT by Homeinvader]
I agree with the above, a quality smith could cut the barrel for you reliably. But I would take the other advice posted of getting a new one instead.

You'd be pumping a lot of money into a used barrel by having it cut, crowned and re threaded. For stuff like this, it's always smarter to keep or sell what you have, then buy a new one in the length and contour you want. New barrels are just too comparatively inexpensive to be putting money into a used one. The money it will cost to have the used one cut plus shipping both ways will be most if not all of the cost of a new barrel. Cutting down an existing AR barrel to a COMMON desired length is a bit of an anachronism IMHO, goes back to the 80s when you didn't have a great variety or availability of non-custom sub -20" barrels. Nowadays you can get cheap factory barrels in almost any length you'd want ready to go.
Link Posted: 3/31/2006 9:19:10 AM EDT

Originally Posted By LOKNLOD:


I think CMMG does Midlength-gas Dissy-style barrels...check out their "M10M w/Mid-Length Gas System" barrels.


--Josh



I've been waiting for one for two months and have another month wait at least. If someone is interested they should call and get on the list.

Link Posted: 3/31/2006 2:14:13 PM EDT
[Last Edit: 3/31/2006 2:16:35 PM EDT by Forest]
For Home Defense? Sure - I've done it (well I had Randall do the work - I just had him cut the barrel to 16.5" and open the gas port to 0.110). It ran well on everything from Wolf 55gr to 75gr Black hills.

For a Class? Yeah I'd think so, especially if you remembered to clean it every night.

For SHTF? depends on your definition and expected duration. Personally for that i'd prefer a standard Carbine or Rifle for maximum reliability.
Link Posted: 3/31/2006 7:42:47 PM EDT

Originally Posted By eye_spy:
The reliability of a "cut-down" barrel would all depend on your gunsmith. If he is good, then he will be able to make your carbine run without any reliability issues.




Originally Posted By Homeinvader:
I agree with the above, a quality smith could cut the barrel for you reliably.



Maybe you missed the part where a quality smith who SPECIALIZES in AR15 barrels said that, in his experience, 16" barrels weren't always reliable.

Now Forest said he has a 16.5" done by that same smith that runs just fine... But then that's .5" longer than 16", and .5" away from being 17", so maybe that makes a difference.

Even KKF's "Kurtsgewer" is a 16.something" rather than just 16".

That 1" from 16" to 17" would barely be noticeable at all, and why not have that extra little bit of confidence in the reliability?
Link Posted: 3/31/2006 9:36:23 PM EDT
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