300 blackout problem? what happened???

J

jimmyg75

New member
A buddy of mine brought his 300 BLK out pistol upper over to our range today to shoot it for the first and sight in the scope. At 50 yards every 4th or 5th round would be on bull the others would be all over most the time missing the 2'x2' Target Then after about 15th round the gun jammed so tight I had to take it home take it apart and unjam it. When I finally got the live round out of the chamber it had just the neck of the previous rounds casing wedged perfectly around it. What the heck caused this?? Was using factory fiochi ammo. oh ya the upper is a 9" pistol upper. Any suggestions before we try this again? something with the gun or just junk ammo. Thanks
 
That will happen when you pin a pistol upper to a rifle lower......

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Why is that? could you elaborate a little more please. Thanks
If you are refering to the legalities the lower receiver came from dealer registered as a pistol says it right on it. He did use buffer and spring he had from a rifle
 
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It is late and I was just trying to be funny.
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Originally Posted By: jimmyg75Why is that? could you elaborate a little more please. Thanks
If you are refering to the legalities the lower receiver came from dealer registered as a pistol says it right on it. He did use buffer and spring he had from a rifle
 
Originally Posted By: jimmyg75 When I finally got the live round out of the chamber it had just the neck of the previous rounds casing wedged perfectly around it. What the heck caused this?? Was using factory fiochi ammo. oh ya the upper is a 9" pistol upper. Any suggestions before we try this again? something with the gun or just junk ammo. Thanks

I had a very similar issue with a 9mm Carbine... I handload everything, and "had" about 4000 9mm brass that was purchased on gunbroker to work with. Gun shoots well, fairly accurate 1-2 MOA @ 75yds with open sights. Out of the ordinary I was shooting some steel @ 50yds when... POP, you could noticeably tell something went wrong, running suppressed as always, there was no need for hearing pro, but this one made my left ear ring... Of course she jammed up, wouldn't feed another round, I pulled the upper off, and noticed inside the chamber the whole case body was still present... When I shot, the case head separated from the body, causing the loud pop, and leaving the 147 projo 6" down the pipe... I took a brass chisel and removed the brass body that was stuck in the chamber, and an old coated Dewey rod with about 5 hard reps with the hand and the bullet came right back out, much to my surprise...
Trouble shooting, I though the headspace was all f-ed up, but the more I looked at it, my brass was crap, who knows how many times fired, etc. etc. Gonna toss all my brass, and start new... Just thought our issues had a "similar" outcome...
 
The upper and bolt came assembled he got them from PSA. He got some new ammo and everything is fine now, shot 40 rounds with out a problem and the groups weren't too bad for 9" pistol upper was getting about 3" groups at 100. So the box of fiochi ammo we had is junk and dangerous in my opinion.The new ammo we tried was Remington.
 
There have been a number of issues with the Fiocchi factory ammo. Was it their 150gr FMJ ammo? It doesn't take much to throw off a .300blk round I found this out the hard way after loading 200 rounds. Basically I didn't seat the die in the press properly and the shoulders weren't formed properly. I had to put the seating die so far in the press that when I over cam it pushes on the shell plate. Haven't had an issue since making this change. Might want to look at a case gauge if you want to make sure every load is properly sized.
 
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Originally Posted By: jimmyg75The upper and bolt came assembled he got them from PSA. He got some new ammo and everything is fine now, shot 40 rounds with out a problem and the groups weren't too bad for 9" pistol upper was getting about 3" groups at 100. So the box of fiochi ammo we had is junk and dangerous in my opinion.The new ammo we tried was Remington.

I have seen first hand cases from spent Fiocchi factory ammo and they are loaded super hot to the point of blowing primers, and leaving serious ejector marks on the brass. Definitely stay away from that crap.
 
Originally Posted By: JoshuaNThere have been a number of issues with the Fiocchi factory ammo. Was it their 150gr FMJ ammo? It doesn't take much to throw off a .300blk round I found this out the hard way after loading 200 rounds. Basically I didn't seat the die in the press properly and the shoulders weren't formed properly. I had to put the seating die so far in the press that when I over cam it pushes on the shell plate. Haven't had an issue since making this change. Might want to look at a case gauge if you want to make sure every load is properly sized.

I had the same issue on the 458 socom, i think it has to do with a blend of die quality and the fact that its a rather small steep shoudler compared to most rifle catridges.
 
iT SOUNDS TO ME THAT FIOCCHI LOADED THE ROUNDS WITH CASES THAT WERE OVERSIZED, what I mean is they created excessive headspace this way with new brass. You should contact them right away and send them samples of the new and fired cartridges as they may have to have a recall for manufacturing defect. When ever a die for resizing is set up it has to be measured(the final case size) after it comes out of your die or theirs to make sure it meets the correct headspace or bad things can happen.
 
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