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9/22/2017 12:11:25 AM
Posted: 1/6/2010 7:21:17 AM EDT
Last week, I assembled one of the recent Colt M16A1 kits currently for sale from Century.

The parts are almost new and the barrel is an aftermarket 1/9 barrel. The barrel has no manufacturer's mark, but the word on the street is that they're from Green Mountain.

When I went to check the headspace, I found that the bolt won't close on a Clymer "No-Go" gauge (from Bushmaster), but also won't close on the "Go" or an unfired M193 cartridge case (bullet pulled). The gauges are marked 5.56/.223 REM and I tested with the extractor and ejector removed from the bolt. I ordered another barrel of the same make from Apex Gun Parts, and had the same result.

Is it correct that there's no fix that I can do? Has anyone had the same experience with the barrel extensions on these new barrels being set too tight? The bolt in the kit is new; is there any use in trying a used bolt?

Here are some photos to illustrate my results.

Link Posted: 1/6/2010 9:01:07 AM EDT
I only see two options. Try to return the barrel, or see if a gunsmith will check the chamber and maybe ream.
Link Posted: 1/6/2010 9:12:22 AM EDT
[Last Edit: 1/6/2010 9:15:37 AM EDT by Richard-ar15]
Yeah, I see what you mean.

Hate to try to mess with returns. I've already drilled and pinned the FSB on the first barrel that came with my kit and coated it with baking lacquer. Lesson learned on that one: I'll test HS before doing any work on a barrel in the future. The second barrel from Apex would be easier to return, I suppose.

The chambers and bores of these barrels aren't chrome lined, so perhaps reaming as you suggested would be better. I would really prefer to keep the 1/9 twist.

If anyone is in a position to check one of their builds, I'd love to know if all these barrels have the same problem.

Link Posted: 1/6/2010 9:16:44 AM EDT

Go here. Rent the reamer and correct the short head space.
Link Posted: 1/6/2010 9:18:47 AM EDT
[Last Edit: 1/6/2010 9:25:42 AM EDT by Richard-ar15]
Great link- Thanks

I can handle the reaming, as long as the barrel extension remains in place. Is that how it works?
Link Posted: 1/6/2010 9:38:14 AM EDT
[Last Edit: 1/6/2010 9:38:26 AM EDT by Hebrew_Battle_Rifle]
Originally Posted By Richard-ar15:
Great link- Thanks

I can handle the reaming, as long as the barrel extension remains in place. Is that how it works?


BTW, I have done business with those folks several times and the reamers could not have been sharper, nor could it have been any easier to do business with them. They really are outstanding.
Link Posted: 1/6/2010 6:04:24 PM EDT
I too bought one of the kits with the same problem. I was told years ago that for interchangability, the barrel and bolt were built to a spec size , plus or minus a smidge and when piecing parts together you could get a big bolt and a small chamber and you could have such a problem or a small bolt and a big chamber and have too much head space. I tried the bolt from each of the other 5 ar 15s I have and the bolt of each would close on a field gauge in the new barrel and strange enough the new bolt woked in 4 of the other ar 15s. I didn't trade it though, I bought a stripped bolt from model 1 sales and it works fine. Haven't fired it yet, upper and lower are out for refinishing to match colors. Hope that helps.
Leo G
Link Posted: 1/7/2010 9:01:04 AM EDT
[Last Edit: 1/7/2010 10:25:47 AM EDT by Richard-ar15]
Glad to hear that there are some bolts out there that will work with these barrels. I received an email off the board from another member who also had short headspace with one of the kits, so it seems to be a common problem.

I've seen that Century is building these kits and barrels up into rifles and selling them as the "C15A1". I wonder if their assemblers have noticed this issue.

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