.223 Chambered Oly Arms

[Iraqgunz]

Can we resize this pic it's killing this page.

[jmart]

We still had an occasional popped primer as well as a cases that would stick in the chamber. Basically Bushmasters are crap and they cut corners and sell a product that they claim is a good as the next guys and they clearly are not.

Bottom line is I should not have to ream a chamber to make it fire ammunition that has worked in other 5.56 MILSPEC uppers, as well as the Bulgarian 5.56 AK's that we have.

I also agree with Grant in that I also put the reamer in the other MISLPEC guns to see what would happen and basically took crumbs out (almost nothing at all). WhenI put it into a new carbine that I had I got a lot of resistance for the first 4-6 revolutions.

Am not doubting at all that you didn't experience this, but I'd love to know how many thousandths of material was reamed away and from where in the chamber. We all can look at pics of reamers with metal shavings on them, but we still don't know how much material we're dealing with from a dimensional standpoint. At best we're making comparative assessments between manufacturers (e.g., Colts yield nothing/minute shavings, Brand X yields more). That's why I like the idea of chamber casts, you know what you're dealing with in an absolute sense when measuring a cast.

The only other thing I'd like to toss out for discussion, does overgassing exacerbate any tendency to pop primers? I only bring this up because conventional wisdom seems to be that BM drills their gas ports larger than Colt/LMT spec (.063" IIRC). At first thought I would think overgassing wouldn't contribute to primer popping, because I would assume that peak pressure is experienced well before the bullet passes the gas port. But then I recalled seeing an ad for David Tubbs' Carrier Weight System, and just like a heavier buffer, the advertised benefit is ensuring bolt lockup lasts just a tad longer and allows pressures to subside prior to initiating bolt unlocking and extraction.

One of the additional benefits advertised though is less wear and tear on caseheads and primer pockets. He includes photos of gas leakage around a primer using a hot load in a case where the CWS was not utilized, and another photo of the same load, but w/the CWS, and there's no gas leakage. Maybe as long as the casehead is firmly seated against the bolt face, everything is well supported, but once extraction starts, the support is lost and pockets can then expand? I'm wondering if by using a heavier buffer (H2, 9mm) in a carbine that may be overgassed, could you achieve the same benefit?

Do you know what buffers you were running in your BM's, the ones that you reamed and still had popped primers? Also, have either of you gauged BM gas ports to know what size they use?

I'm a bit stumped in that you still experienced primer popping after reaming out your chambers. Something still has to be causing this, and I'm simply curious what the added issue is? I highly doubt it's the chamber body being out of spec since there's really no deltas between SAAMI and NATO spec for the body dimensions, headspace is the same, there's only only 1.5 thousandths delta in base dimensions, etc.

[Iraqgunz]

We are using standard BM "H" buffers in our carbines. I have not removed the gas blocks and am unsure if the any of the gas ports are eroded. Whenever we shoot true M855 ammo we do not have these issues. Only when shooting the PP and Bulgy SS109 ammo.

[C4IGrant]

This is pulled straight from Ned's website, and it shows the deltas between sectioned SAAMI chambers, NATO chambers and a chamber reamed with his throating reamer. As you can see, the pic of his chamber shows additional material removed compared to the previous NATO chamber.



Link to a larger picture showing greater detail


Also, from the text on his website:



I'm wondering if some manufacturers have figured out along the way that the way to go is with a "plus-dimensioned" NATO chamber from the start. Maybe Colt and LMT are producing NATO chambers on "the high side" straight from the factory, and that's why you're not getting any material removal.

I know EXACTLY what it says. Remember that I have been using Ned's 556 reamer since DAY ONE and have reamed tons of barrels. What I am saying to you is that MY reamer is NOT over sized as I do NOT get material back from companies that follow the TDP.

IF my reamer was on the large side of the 556 NATO spec, I would get just some light dusting from reaming a Mil-Spec chamber. The material you see in the pic above is a metric truck load and is NOT what you are going to get if the chamber is a true 556 NATO.

C4

[PhotomanM4]

Any experience regarding this issue and Stag uppers?

[C4IGrant]

Any experience regarding this issue and Stag uppers?

Yes. Have reamed their barrels and gotten material back, but nothing like the above pick.


C4

[M4tographer]

Yes. Have reamed their barrels and gotten material back, but nothing like the above pick.


C4

Hate to beat this into the ground, but any experience with CMMG? Have a flattop M4, 1:9 twist, 5.56 NATO, WASP finish going into a build currently.

[C4IGrant]

Hate to beat this into the ground, but any experience with CMMG? Have a flattop M4, 1:9 twist, 5.56 NATO, WASP finish going into a build currently.

I do not believe that I have reamed one of their barrels yet. I did have a lot of other issues though (soft FSB pins, alignment of FSB, threads off center).

The general rule of thumb that I follow is that if it has a 1/9 twist, the chamber is most likely NOT a true 556 NATO chamber. So far this theory has held true.


C4

[RogerinTPA]

After reading this thread, it's hard to believe that there are so many firearms manufacturers out there falsely stamping there barrels, knowing the chambers are not 5.56. There ought to be a law (Truth in Advertising) and buyers should be able to sue them for fraud. This should serve as a wake up call for anyone not in the know.

[C4IGrant]

After reading this thread, it's hard to believe that there are so many firearms manufacturers out there falsely stamping there barrels, knowing the chambers are not 5.56. There ought to be a law (Truth in Advertising) and buyers should be able to sue them for fraud. This should serve as a wake up call for anyone not in the know.

Actually it is easy to believe (at least for me). A lot of these companies are no better than used car salesman.

To play devils advocate for a second, I believe that one of the reasons why companies use 223 chambers is because they do not want the customer coming back saying that the gun only shoot 3-4MOA. These companies are also making the assumption that the majority of the people that buy their weapons aren't actually to shoot them and so a tight chamber matters not.



C4