Home Forums Hunting & Shooting AR and Tactical Rifles Issue with 300 blk chambering

I took my new PSA 300 Blackout to the range for a trial run. It shoots Hornady Black factory loads smooth, runs great. 1.5 group @ 100 out of a 10.5" barrel with the 110 gr factory loads. I tried some Fiochi 147 gr fmj range ammo, and it wouldn't seat. Jammed the bolt, stuck in the chamber. Then I tried some reloads that I got from a guy, and same deal. There are some scratches on the brass, so it may be a rough chamber. A few questions.
1) Is there anything I can do to smooth that chamber out, or does it need to go back to PSA?
2) Can I run the loaded ammo through a sizing die after I take out the decapper rod, Or will it be to tight with the loaded bullet? I've never tried it before. thought maybe they weren't full resized.

if its a nitrided barrel maybe the surface is rough. I would try and polish it with some butches bore shine and a short cleaning rod, bronze brush with a patch wrapped around the brush.

I would try chucking an appropriate sized bore brush into a drill and giving the chamber a good heeve-ho.

Negative to the resizing question.

First thing is to clean the chamber real good.

Then might measure the ammo in question and compare them to the ones that chamber.

CLP and a brass brush with some scotchbrite or steel wool in the chamber won't hurt it.

Then if it still won't chamber send it back.

OK, I will try polishing the chamber. It is a brand new upper, so chamber shouldn't have been dirty when I started.
I started out firing 20 rds of the Hornady Black 110 gr factory Ammo, ran perfect. Then the first round out of the magazine of the Fiocchi jammed up. Tried the reloads, jammed up. Went back and fired another box of 20 Hornady Black 110's and it ran perfect.
Anybody ever have an issue with Fiocchi ammo being out of spec? The reloads don't surprise me, but new factory ammo should fit without issue.
Thanks for the Reply's; John

I doubt that polishing is going to fix that problem.

Check the headspace & the case diameter just ahead of the groove on the brass that chambers & the brass that doesn't & see what you get.

Likely a snug chamber in either HS or diameter.

MM

110's chamber and 147's don't.

Sounds like it might have a short throat.

Did you see rifling marks on the 147gr bullets after you got it out of the chamber?

It could be as simple as the throat being just a tad short.

But it never hurts to scrub out the chamber.

I will check the bullets tonight and see if they do have rifling marks on them. I think the reloads were 110's too, but they may not have been FL resized. I'll check them both. maybe put some sharpie on them and drop them in the chamber.

I did not want to not give him any hope, but this is probably more likely than anything else. The right answer is probably new barrel.

This.

I had a barrel with a very tight chamber. I ran some ammo through a Redding small base body die. After a few hundred rounds the chamber opened up enough to run normally sized and factory ammo.

Considering that Blackout bullets are offered in weights all the way up to 220 grains to be fired subsonic in suppressed guns, it seems to me like it should be the last gun that would choke on a SAAMI spec 147 round. I would contact PSA.

this x3
my 300 wont take bullets with a forward ogive. i cast 220g's and size to 308, THEN i have to swap dies and size the front of the bullet ahead of the driving bands to 306
needless to say i dont shoot them to much. most jacketed seated to fit the mag will cycle, but have run into a few that wouldn't due to a far forward ogive

I scrubbed out the chamber with a bronze brush and CPL last night. Then wrapped 1000 grit sandpaper around a small dowel until it slid snugly into the chamber, then spun it by hand for about 10 minutes.
All tye factory ammo, including Hornady Black 220 gr cycled flawlessly. The reloads that I bought won't allow the bolt to close. I can see a ring on the brass about an eighth to a quarter inch up from the bottom of the base. Gonna get a small base sizing die and run them through and see if that cures it.

I did contact PSA yesterday. We'll see if I hear back from them, but I think I have it cured for now, tight and rough chamber apparently.
Thanks for all the replies and advice, much appreciated

I wouldn't risk messing around with it when you can just send it back to be corrected/replaced by PSA......

they may say "its fine".....after a few months.
its a bad time as well, things are harder to find these days due to our "excess freedom"...