300 Blackout Chambering Problem

[altheating]

Ok, why can't I gat the 247 cast NOE boolit to feed through my AR? I have tried everything. Loaded short, long, even the Lee cast boolit hangs up. I have loaded Sierra 165's and 110's and they all feed flawlessly. Dropping them in one at a time works, but that's not much fun. I can get the rounds from the right side of the mag to feed but not from the left side. I have tried a total of 5 brands of magazines including two old pre ban mags, all the same! Any ideas?

[runfiverun]

look where it's banging off that tiny feed ramp.
yes the ar's have one.

[Moonie]

Does your upper receiver have the M4 cuts? I have issues with some magazines with the 245/247 grain boolits, they catch on the front.

[altheating]

Not sure about the cuts. What mags are you using that work properly?

[thehouseproduct]

What does the bore riding section mic at? I had some problems with the nose being 301 and the bore being 300.

[rockrat]

Don't think the bore section is going to make any difference, he indicated that he can drop them in the chamber and shoot one at a time, but it won't feed into the chamber.

Look to see where it hits on the barrel extention, you might have to do a bit of modification there

[popper]

2 mag to barrel extension feed ramps that should also be in the barrel. Are they aligned properly. Check height of rounds in the mag and mag lips. Case MUST be in proper position relative to bolt to feed properly. Try opening the lips at the front more than the back(slight upward tilt of the nose). If you mod a mag, MARK it - it may not work with other loads. That one has a different profile.

[thehouseproduct]

Don't think the bore section is going to make any difference, he indicated that he can drop them in the chamber and shoot one at a time, but it won't feed into the chamber.

Look to see where it hits on the barrel extention, you might have to do a bit of modification there
It did for me. Fed straight in they were ok, but not out of a mag. The only differences I could find was the bore rider. I traced the problem to lead between mold halves making the nose oversized.

[rockrat]

Thats because you have the greater momentum of the bolt closing when fed straight in, but using the mag, you have drag caused by trying to feed a round out of the mag, so the bolt speed is lessened, therefore not enough force to totally chamber the round.

Altheating , I believe has a problem with feeding, not chambering. His mag will feed from the right side, but not the left. The tweeking of the lips on the mag is a good suggestion as is checking out the feed ramps.

[Moonie]

Not sure about the cuts. What mags are you using that work properly?

I've only been able to get my 245/247 gr boolits to feed well by loading them deep so the case is up to the end of the full groove diameter section, this is with USGI mags and my PMAGs.

[rockrat]

Mine feeds from 15 rnd mags and mine are seated so about .050" of the front driving band is out of the case