I know the match chambering is tighter. But what are the pros and cons of each? I have an M4 upper with 5.56 Match chambering. Thanks.

A tight chamber is going to be more sensitive to ammo it likes. It might not like surplus military ammo at all.

Is match more accurate?

Generally, yes.

So, is Q3131A considered hot military ammo? That'w what I've been shooting. I shot about 100 rds mix of gunshow reloads and South African, no problems.

I fired a rifle yesterday that would not even chamber Q3131A half the time but match Black Hills ran 100%.

Devl:

That your SPR? Whose barrel and did you have a tight chamber cut? Just curious. After all your pics you sparked some interest. Ive got some biases - trying to confirm or disprove them.

Pretty much been covered here. One issue is reliability. You see this often with 10/22s with match chambers. The chamber is much (relatively) shorter then a factory cut chamber. Since these things (10/22 with bull barrels) have become exceptionally popular, you have folks that arent used to match tight chambers wondering why their guns wont run. They dont get cleaned enough.

Troy touched on this with military loads, but its not just a product of sizing. Even using consistent match ammo it will be more sensitive to fouling. Good news is match stuff is normally cleaner. Since your not having issues with Q3131 and SA I wouldnt worry about it - as Troy pointed out you may not have an exceptionally tight match cut. If you begin too, clean it more often, see if that helps.

Luck
Alac



 

Actually, let me clarify.

I fired about 100 rds of a mix of gunshow reloads and South African battlepack ammo, then left it over two days w/o cleaning. Then I tried to shoot Q3131A, and the gun WOULD NOT fire. It was so dirty and gummed up inside I had to do a field cleaning of the bolt and chamber.

At first I thought it was because of the ammo, but now it may be a combination of both.

It fired several hundred rounds of the Q3131A w/o a problem after that cleaning.

sort of as an aside, I found this out earlier this year when doing some research.

This is a listing (not comprehensive) of chambers from tightest to loosest:

.223 REM
5.56 Match
.223 Wylde
5.56 NATO

At least that is what I remember.

Reloads are usually dirty. Sounds like that is at least part of the issue. I'd stay away from the reloads. Doesnt apply to the Black Hills stuff - they are exceptional.

Since your having malfs, you need to determine exactly what the issue is. Its hard to isolate all the variables, but reduce them -  one brand of ammo for starters. Start with a clean gun. If you are certain its a match chamber, avoid military loadings. Still having issues?  You'll have to make further determinations. Get it to a smith or the mfg. if you need.

Who's barrel is it? Markings?  Tighter chambers may not be able to function with some loads. You may need to clean it more often. There may be some lots of the same load that wont run. If you need an alternative to miltary loadings, try the BH blue box 55gr .223, its reasonable. If this bothers you can have the chamber reamed, as long as its not chrome lined. Cant see chrome and match chamber together. Hey maybe someone does it.

Luck
Alac

My match chambered upper is not chrome-lined, so I am thinking about having it reamed by a good local gunsmith, Ed Vanden Burg.

Well thats a good option. If it aint too much and you want to use the cheaper stuff with better reliability, that might be it. I'd get some rounds through it first. Doesnt sound like you've fired it much. You may find the more you shoot the more reliable it is. Not sure I'd recut a chamber on the basis of one outing. But thats your call.

Just a thought, how rough is the chamber. May have him look at that first, maybe you can get by with bit of finishing.

Luck
Alac

Thanks for the info!

May I ask why you would buy a carbine with a match chamber?  That's like lowering a Jeep to get better corning performance on a track.

This one was my first AR. I bought it as part of a SteyrAUG group buy, so I got caught up in the excitement of getting one. It was billed as having a 5.56 chamber instead of a .223 chamber. I didn't realize there were distinctions even in the 5.56 chambering.

You can point to the reason as not knowing any better. [:)]

So it was advertised as having the M16 chamber but it really has a .223 match chamber?

I'd be talking with the manufacturer on that one.  At the least if the barrel is not chrome lined you can open up the match chamber to M16 specifications.  I know Kurt Wala of Kurt's Custom offers this service (see the Industry section) - your local gunsmith might be able to do it too (if they have the M16 reamer).

Acutally, I [i]think[/i] it was advertised as having a 5.56 Match chamber, but I did not know what that meant then. I was just trying to avoid the .223.

Nothing wrong with 5.56Match on a carbine, terms normally used on a SAAMI chamber with a longer throat. You have to accept the trade offs - potentially better accuracy vs potentially more stoppages. Now if it turns out to be a .223 Remington SAAMI chamber, then thats an issue. If that is your concern get it to your smith.

But before the baby goes out with the bath water let me point this out - When it was clean and it had good ammo there was no trouble. Thinking you're not going to have any further issue if you keep it clean and stick with decently priced XM193, Q3131A, IMI M193, Black Hills or SA. These are cleaner than the similarly priced Malaysian, Guatamalan etc that arent bad but may be a bit too dirty. But if the rounds wont chamber get it to your smith.

Let us know how it turns out. Bet you'll be happy with your choice.

Luck
Alac