AR frustration

[xacex]

I've never had an AR that didn't just work out of the box.

Rare, but it happens. With so many manufacturers pumping out parts tolerance stacking, and burs are the most common problem. Reamers wear, shaving get left in bolts or barrel extensions, burs are left in gas ports ect, ect. This is why I like building my own. I get to inspect all of the parts, and make sure the parts are good as well as clean and oiled. The only AR I had that did not run the first time I took it out was a 9mm build. It took a little more fitting with that one. I just did a 6.8 SBR build with a friend and we found a few slight issues that we had to work through. Shot just fine the first time, and every time but if it were a factory build they would have not caught the problems just slapping it together.

[molar]

Sounds like a chamber problem. If the Oracle won't take factory ammo, send it back. You'd want both chambers spec so you don't have to keep track of different ammo. I assume you have a case gauge for 223? You could change the Oracle barrel to 40WT or BO and have a lot of fun.

There are lots of reports of 5.56 and 308 DPMS guns having chambers so tight they have to be reamed.

[runfiverun]

must be buying their reamers from Lyman.

[JonB_in_Glencoe]

I finally got time to mess with the Oracle.

The short story is, looks like the Oracle's chamber is within spec, although seemingly on the tight side.

The complete story:
First I looked in the chamber with a good snake light.
I could see one large granule or Burr or something at about the halfway point of the chamber. It looked like the size of one granule of FFFF BP. Maybe a loose metal chip from machining?

I flushed the chamber with WD40, then blew it out with compressed air.
Then I put some CLP in there and then scrubbed it with a AR chamber brush and then ran a CLP soaked patch down the barrel with a brass jag. Then a few dry patches, then a big piece of flannel to dry the chamber. That speck was gone, chamber looked good, for what can be seen with naked eye and the snake light.

The results:
Mil Surp ammo cycled fine now.

The brass I used to make and re-make the dummy rounds(that I talked about in the OP), were now too long (.001 to .005 over 1.760). I'm not sure where they started out at? cuz when making the dummy rounds, after I FL sized them, I didn't check length, but should have. So today, I FL sized them again and then trimmed (and deburred)them to various lengths...and attempted to cycle the brass cases only (no bullet), from the magazine.

1.750 chambered fine.
1.755 chambered fine.
1.758 (what my Lee case length guage setup trims them too), chambered fine.
1.760 stuck in the chamber, just a tiny bit.
1.762 stuck ...and stuck good in the chamber.

I never took the time to set the shoulder back during FL sizing, since I had success with trimming to various sizes.

I didn't take the time to try any boolit ammo, since I will be using the other AR with a seemingly more roomy chamber, for that.

Thanks to everyone who offered helpful advice.
Jon

[sparky45]

JonB; a case gauge is your friend. I suspect most of your problem is that your cases are a bit over size for the chamber. I went through the same process with a tight chambered 300 blackout. Once I got the case gauge, the problem was quite noticeable. I also invested in a small base FL 223 die.

[JonB_in_Glencoe]

Sparky,
Case gauge: no doubt.

But I got 'er solved now ....and as long as it works fine with mil surp ammo, I'm fine. I'll just use the other rifle for CB loads.

Next up is range testing of both, to confirm.

[W.R.Buchanan]

John: you said you didn't set the shoulder back when You F/L Resized? You kind of need to. Run the die down until it touches the shell holder just before the press cams over center at the bottom of the stroke.

Next if your cases are longer than 1.76 after F/L sizing they will run into the front edge of the chamber. With a bullet in place it will pinch the bullet and cause a pressure spike. NO NO.

OAL on these is more about feeding from the magazine. Cartridges longer than 2.250 will probably run into the front of the mag and cause problems. Anything shorter should feed just fine.

You could get by not bumping the shoulder back if you were shooting a Bolt Gun with some mechanical advantage as it goes into battery. Not the case with a Semi Auto as it only relies on the spring to close the bolt.

It sounds like your root problem is not F/L sizing completely.

I see trying to get Cast boolits to work in these guns to be an exercise in futility. The feed ramps are nothing more than little grooves cut at 4 and 8 O'clock in the back of the barrel and they wouldn't be very lead friendly in any event.

Randy

[JonB_in_Glencoe]

Randy,
what I meant was setting the shoulder back farther than Spec.
Besides my standard FL die, I have one that was modified by the previous user(removed about 1/4" of the bottom of the die, so it can be adjusted lower).

Thanks for the hints...much apreciated.
Jon

[popper]

If you don't like slam fires, get a case gauge and check them all. A cast 308 will make a 1/2" deep crater in concrete.
Edit:Set you die to FL size the smaller/factory chamber. GKs both have Weatherby 243 and have different chambers. Got to size to smaller or they will switch ammo and get jam.
Oh, get a chamber brush if you don't have one.