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Posted: 9/15/2004 6:33:25 PM EDT
[Last Edit: 9/15/2004 6:34:47 PM EDT by scintillus]
Hi, folks,

I finished up my Non-Ban conversion of my Bushy M4-type yesterday and took it out to shoot today for barrel conditioning and sighting in.

I fired 12 shots, 7 of them had the case rim ripped off by the extractor, leaving the case in the chamber. At first I thought this was due to a tight chamber/brand new barrel, since after round #3, it stopped doing it for about 2 rounds. All shots were fired as the only round in the magazine, so I had no "double feeds." I was doing the "fire 1 shot, clean the barrel, repeat" method of barrel conditioning recommended by DS Arms.

At first the stuck cases required a sharp rap with a cleaning rod to remove, but later, it took much less force to get them out.

Anyway, I used a 16" Model 1 Sales M4-type barrel and the Model 1 sales CAR-type telestock.

Possible thoughts:

Tight chamber?

Recoil buffer too light, causing very fast recoil? If so, this would probably be the easiest to fix, just get heavier buffer?

Too high pressure/case tight fit? (probably not as these were reloads which were full-length sized, and unfired rounds drop right out of the chamber when manually inserted. Cases were true once-fired cases, so I don't think the rims were weak.)

.223 chamber? I specifically ordered a 5.56 chamber, but the barrel isn't marked one way or the other...I thought 5.56 was all Model 1 had in M4 barrels.

Well, if anyone has any thoughts I'd certainly appreciate any help!

Thanks in advance!
Link Posted: 9/15/2004 9:53:15 PM EDT
Need to know ammo type, and if the barrel is chrome lined.

As, would help to confirm that the barrel is chambered 5.56 if your shooting 5.56 ammo threw it.

As for the rim getting torn up, it's the chamber that is the problem.
My guess is either its rough, incorrect head spaced, or a 223 chmaber that your trying to feed Nato spec ammo threw.
Link Posted: 9/16/2004 5:13:05 AM EDT
Thanks for the reply!

As I mentioned, the ammunition was reloaded (by me). Reloaded to .223 spec. 55gr. Winchester BT bullet in front of ~24 gr H335.

Barrel is definitely (per my order receipt) a 5.56. I haven't measured the chamber myself.

The bore and chamber are chrome-lined; what would be a good wy to smooth the chamber out?
Link Posted: 9/16/2004 11:21:34 PM EDT
Link Posted: 9/18/2004 10:43:16 PM EDT
1. Even with new parts, you should verify the headspace is correct. I've run across several uppers that had too little headspace and would not close all the way on a "go" gage causing high presssure.

2. Check chamber for any rough spots. It's not easy to smooth out a chrome lined chamber as
that should have been done before it was chromed.... best to return it for exchange if this is the case.

3. Verify that the gas hole in the barrel is correct size, this will require removal of the front sight/gas block. It should be around .069 if I remember correctly. Some of the no-name barrels are incorrectly drilled oversized and cause the rifle to try and extract before the chamber pressure is low enough.

When the problem is so bad that the case rim is getting ripped off, then it is almost always related to either the barrel is out of spec or the ammo is at fault. Recoild buffers and springs won't play that big a role.

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