Confirm Action

Are you sure you wish to do this?

Confirm Cancel
Member Login

Site Notices
2/21/2020 11:35:28 PM
Posted: 10/27/2004 10:25:49 AM EST
I recently installed a RRA 16" 1/8 twist SS barrel on a Bushmaster upper, w/ a new Colt bolt. After firing approx. 100 rds. of Win Q3131A, attempted to clear the weapon. The charging handle required a LOT of effort to extract the live round from the chamber. Chambered a few more rounds, each was difficult to clear. Experienced no malfs during firing: all spent cases extracted/ejected fine. Spent case rims looked fine (no extractor gouging).

Switched to Black Hills 75gr. heavy match (blue box), had no difficulty clearing these rounds.

I thought these barrels had Wylde chambers, which should eat 5.56 NATO w/o problems. Is this a break-in issue, or should I have the chamber/throat reamed? Or just stick to .223 ammo?

Any suggestions would be much appreciated.

Thanks in advance,

Other info:
Bolt closes on a Forster GO gauge (1.464")
Link Posted: 10/27/2004 11:05:08 AM EST
Not a shoulder head space problem, But a ammo selection problem. Your chamber may be a tight 5.56 nato or a loose 223 that is allowing you to shoot the nato ammo (end of chamber cut and the throat lead distance). Also, the BH ammo has a longer ogive on the 75 (bullet has to be shoved father into the chamber before it engages the rifling) with the q3131a engaging the rifling at loading.

Q3131a is 5.56 nato spec, and the black hills is 223. The ogives of the two bullets are different and the 75 grain would need to be loaded longer than the 55 to touch the rifling. Since this is a match type barrel, the shorter throat would be much more desirable for reloading. On the 55's you just shorten the load to kiss the rifling, and stand a better chance on being able to longer load the 75's (still fit into the mag) and too kiss, the rifling.
Link Posted: 10/27/2004 12:06:24 PM EST
Thanks. Is it feasible to lengthen and/or widen the throat to accommodate NATO spec ammo? This is a SS barrel.
Link Posted: 10/27/2004 6:35:56 PM EST
Why in God's name would you buy a NM barrel, and then screw up the barrel by over-sizing/elongating the throat/chamber? If you want to shoot Nato ammo, then get another rifle that has a 5.56 Nato chamber.

At best, your going to get around a 2" group with the Q3131a or XM193, so why screw up a barrel that will out shoot this ammo, just so you can run it threw it.

Hell, If you just wanted to swap barrels, I'm sure that someone would trade you straight across without a second thought.
Link Posted: 10/28/2004 4:30:06 AM EST

Originally Posted By Dano523:
Why in God's name would you buy a NM barrel, and then screw up the barrel by over-sizing/elongating the throat/chamber?

I thought the barrel had a Wylde chamber, which I understood to handle both .223 and 5.56 NATO. I wanted a mid-length barrel that would shoot both NATO-spec ammo and 75-77gr bullets; this barrel, with its 1/8 twist, seemed to be the only option short of a custom barrel (I've since become aware of Giffmann's group buy on mid-length, 1/7 twist barrels).

As for "screwing up" the barrel, I'm willing to sacrifice some accuracy for NATO-spec ammo compatibility. I just don't know if such a thing is worth doing. So I ask again: Is it feasible to lengthen and/or widen the throat to accommodate NATO spec ammo?

Link Posted: 10/28/2004 12:53:21 PM EST
Yes, you can just re-ream the chamber without lengthening the headspace. The end of chamber cut and throat is what you will be lenghtening.

This re-reaming will be at a cost of accuracy when you do use match type ammo.

Link Posted: 10/28/2004 3:01:48 PM EST
Dano, thanks for your help.
Link Posted: 10/28/2004 9:57:21 PM EST
Link Posted: 10/29/2004 8:43:27 AM EST
Speaking of throat reamers,

Any idea where I can rent a 40 S&W with a 10mm throat lead??

The only option I can find right now is just a throat reamer. But since this is a factory Para barrel, really not sure is the chamber is cut true to the outside of the barrel (barrel lathed true with the outer surface and reamer straight plunged which might cause the throat to be off sided in the bore). With the combo reamer, I can just uses the existing chamber to stay in line (bore line), then hand turn the reamer to deepen the throat (I can true off the inside of the chamber walls on the working side of the lathe, but lathe head is to long to spider the barrel/muzzle out the back end and true off the spider as well-two point truing).

P.S. If anyone is asking why would I do such a thing, 1911-Para frames will allow a 10MM lengths to fit in the mag. By long hand loading the 40 to 10 OAL’s, this gives me 10mm Volume in the 40 cases. The reason behind going this way is the you can buy 40 once fired cases dirt cheap, verses having to buy new 10mm cases to push light rounds to the 175 major power factor safely.
Link Posted: 10/29/2004 11:19:36 PM EST
Link Posted: 10/29/2004 11:35:50 PM EST
I take it your shop is not building race pistols.

I would try the pistol forum, but the place is a ghost town.

Only other solution may be to find someone how has a Mini-lathe with a short head stock/end spider that has had the bore drilled out to take a barrel. I know Royce has one, but he is in NY.
Plus, It's really scary trying to square up the mini's (day long project in it's self), then pray the it holds true once you turn it thing on and make the plunge/cut.

Not the end of the world, just need to find a new way to either skin the cat, or just see what bullet design I can find to be able to long long and not engage the rifling.
Top Top