Problem with 300blkout

[Lurch]

I loaded up a few rounds of 300 blkout and they will not fully chamber. It appears the bolt isn't going into full lock and when I go to eject the shell it is very hard to eject. Some of the rounds will fire most take a second try to get them to fire. I tried a factory load and it chambers and ejects like butter. I have tried just cases and it's still a no go so it's not a bullet or oal issue. It appears that the shoulder is a tad higher then on the factory load but it's impossible to measure. Could I possible have a bad die?

[XC700116]

I'm assuming the hand loads are not actual 300 BLK brass to beigin with and are 223/5.56 cases cut down and formed into 300 blk. Either way though, measure the diameter of your loaded ammo at the neck and compare to the factory ammo. I've had this problem with a couple of different cases (made from 223/5.56 cases) Some of them are too thick.

To check the die definitively I'd fire some factory ammo and then load those same cases and see if they chamber without problems.

[DFBrews]

Check oal of the brass too I had some that was .010 to long would not chamber

[Lurch]

All measurements seem to be the same. Granted my micrometer isn't the greatest so it maybe time to get a new one. I have a couple of pieces of brass where the neck is visible shorter and they chamber fine. I'm going to cut one a bit shorter and see if that is the problem.

[Danimal]

I have had this exact same issue and I can narrow it down to one or a combination of the following three issues if you are using re-formed 5.56:

1) The brass it too thick on the neck of the case so when the throat expander pulls out of the case it stretches the throat outside diameter to a diameter larger than the chamber.
2) The brass is not completely formed so when the throat expander pulls out of the brass it elongates the shoulder increasing the OAL and creates a high shoulder that hits before full battery.
3) The brass at the neck has been work hardened slightly too much prior to being formed and springs back out of shape slightly once it leaves the die.

All of the above have happened to me. There is a thread with some pictures on it of the brass that I was working with and exactly what type I found to be too thick to work with. I will look for a link after I post this. The one thing that I found that really helped was to anneal the blackout cases. It is not high case pressures that you are worried about, it is the fact that some of the brass used to make it came from 5.56 that was a high pressure round and has been work hardened prior to being cut down. This makes it harder to form with the dies and will lead to cases with shoulders that are elongated just slightly. Also I was feeling like I was going to tear my press off of the bench at times trying to re-size the brass. Annealing did not totally fix the problem for me, but I would say that I get one or two that FTF per trip but they are easy to clear and that is a hell of a lot better than the 25% chance that I would have to put the gun in the truck with a round 80% in battery jammed in there so bad that I could not get it out.

It frusterated the hell out of me, but as of now I have them all annealed and I am working my way through my stockpile getting them all once fired as blackout and after that they are all 100% working and they look identical to the factory brass. I still do a round drop test for every completed round prior to going to the range and anything that does not drop right in gets measured and usually taken apart. If it does not drop in, it will hang when the bolt is driving it forward and it will be hell to get out. Also the forward assist is a bad idea that makes a shit sandwich even worse.

[paddywagon]

I loaded up a few rounds of 300 blkout and they will not fully chamber. It appears the bolt isn't going into full lock and when I go to eject the shell it is very hard to eject. Some of the rounds will fire most take a second try to get them to fire. I tried a factory load and it chambers and ejects like butter. I have tried just cases and it's still a no go so it's not a bullet or oal issue. It appears that the shoulder is a tad higher then on the factory load but it's impossible to measure. Could I possible have a bad die?

i am sure you've done it but just to check, is the sizing die all the way on to the shell holder? I have had a couple calibers that I have had to over cam it just a tad.

[Lurch]

Well it seems all my brass was a tad over length. Trimmed another .010 off as suggested by DFBrews and all seems gtg now.

[20X11]

Well it seems all my brass was a tad over length. Trimmed another .010 off as suggested by DFBrews and all seems gtg now.

What was your original case length?

[Lurch]

What was your original case length?

1.355 and I actually only took of .005 making it 1.35. Picked up a better micrometer.

[DFBrews]

Well it seems all my brass was a tad over length. Trimmed another .010 off as suggested by DFBrews and all seems gtg now.