300 Blackout reloaded ammo issue

[marek313]

I have 300 Blackout PSA upper that I've using for about a year now. I've shot over 1,000 rounds of cast without any issues so I loaded larger bath of about 750 rounds last month or so. Rounds chambered fine when I first tested (passed my Hornady gauge test) but when I went to the range yesterday most of those didnt chamber all the way. I only shot handfull of rounds and I had to stop. Rounds wouldnt chamber all the way and I had couple stuck where I had to clear it by carefully hitting the butt stock on the ground while holding charging handle. No signs of leading so I switched to couple FMJs that I had loaded and those ran great with no issues (same cut down .223 PMC, GFL, LC mixed brass). When I got home I started looking at the ammo in question and all my necks were too large regardless of brass headstamp. Rounds wouldnt fit in the Hornady ammo gauge. Either lead projectiles grew in size or brass necks sprung back with time. Either way I wasnt going to pull 750 rounds without a fight so I took the decapping pin off the sizing die and ran couple through. Took some force to basically size it back down so I'm guessing my projectiles grew in size. Mind you I didnt load these rounds right after casting. I always let them sit for at least a week before I load just so they harden and grow. After that I manually cycled couple and they fit fine. I was running out of time but I know someone is going to recommend to pull one of the bullets. I'll have do that when I get home today.

I noticed before that lead grows little bit as its aging but never to the point where rounds wouldnt chamber.
Has anyone else noticed that behavior? What do you do to deal with it?

[Omega]

I have 300 Blackout PSA upper that I've using for about a year now. I've shot over 1,000 rounds of cast without any issues so I loaded larger bath of about 750 rounds last month or so. Rounds chambered fine when I first tested (passed my Hornady gauge test) but when I went to the range yesterday most of those didnt chamber all the way. I only shot handfull of rounds and I had to stop. Rounds wouldnt chamber all the way and I had couple stuck where I had to clear it by carefully hitting the butt stock on the ground while holding charging handle. No signs of leading so I switched to couple FMJs that I had loaded and those ran great with no issues (same cut down .223 PMC, GFL, LC mixed brass). When I got home I started looking at the ammo in question and all my necks were too large regardless of brass headstamp. Rounds wouldnt fit in the Hornady ammo gauge. Either lead projectiles grew in size or brass necks sprung back with time. Either way I wasnt going to pull 750 rounds without a fight so I took the decapping pin off the sizing die and ran couple through. Took some force to basically size it back down so I'm guessing my projectiles grew in size. Mind you I didnt load these rounds right after casting. I always let them sit for at least a week before I load just so they harden and grow. After that I manually cycled couple and they fit fine. I was running out of time but I know someone is going to recommend to pull one of the bullets. I'll have do that when I get home today.

I noticed before that lead grows little bit as its aging but never to the point where rounds wouldn't chamber.
Has anyone else noticed that behavior? What do you do to deal with it?
A little more info is needed but here is an educated guess; While the gauge is a good indicator, best to do a plunk test. If using Lee dies, you will have to do a couple things, first trim down the shell holder a bit, start with about 1 or 2 thousands. Make sure you have set your sizing die correctly, with the ram raised touch the shell holder, then 1/4 to a 1/2 turn more. Also, check your COAL to make sure the bullet you are using isn't hitting the lands and grooves. When converting once fired 5.56/.223, give a 1/4 turn and size again waiting a second or two before lowering the ram between steps. With RCBS or Hornady, be sure to set your sizing die correctly, the size/turn step and the shell holder mod can be omitted. When setting your seating die, if it has a crimp function be sure that it is not hitting your case flaring the mouth a bit (light crimp). I would crimp as a separate step, preferable with a Lee FCD.

[Texas by God]

All of the above is great advice. You haven't told us which boolit you are loading- did you follow the .250" rule? I've never heard of boolits expanding a neck after being loaded. Did they fit/function after the re- resizing?

[dimaprok]

A little more info is needed but here is an educated guess; While the gauge is a good indicator, best to do a plunk test. If using Lee dies, you will have to do a couple things, first trim down the shell holder a bit, start with about 1 or 2 thousands. Make sure you have set your sizing die correctly, with the ram raised touch the shell holder, then 1/4 to a 1/2 turn more. Also, check your COAL to make sure the bullet you are using isn't hitting the lands and grooves. When converting once fired 5.56/.223, give a 1/4 turn and size again waiting a second or two before lowering the ram between steps. With RCBS or Hornady, be sure to set your sizing die correctly, the size/turn step and the shell holder mod can be omitted. When setting your seating die, if it has a crimp function be sure that it is not hitting your case flaring the mouth a bit (light crimp). I would crimp as a separate step, preferable with a Lee FCD.Crimp is flaring case mouth? what??? that doesn't make sense. Also "trimming" shell plate one or two thousands of an inch won't make any difference whatsoever. I would say start with 10 thousands. Plunk test for 300 blk? My understanding plunk test applies to pistol rounds dropped in the barrel. How are you supposed to take the rifle barrel off and drop a round in to it?

Sent from my SM-G950U1 using Tapatalk

[jimb16]

Sounds to me like you aren't getting a good crimp. I had a batch that did the same thing. Took them home and recrimped them and they all fed perfectly after that.

[lksmith]

... Either way I wasnt going to pull 750 rounds without a fight so I took the decapping pin off the sizing die and ran couple through. Took some force to basically size it back down so I'm guessing my projectiles grew in size. ...

Careful doing that. I did that with some rounds that didn't chamber all the way (I probably missed them when sizing) and not only did it shrink the neck it swaged the bullets and they all keyholed. Annoying without a suppressor, disastrous to the pocketbook with one.

When I have that issue on necks (usually 223/5.56) I run them through a body die even though MFG doesn't recommend doing that with loaded ammo since you are essentially chambering a round with a lot of force. Redding is the only brand I've seen that has them

[marek313]

OK so projectiles are fine. They are from Lee 312-155-2R PCed at around 16bhn sized to .308 and since I just remembered that I had some left from that batch I measured those and they are still at .308. I know i need to open up my sizing die to .309 but they didnt grow at all so there goes that theory :oops:


Its definitely something with that brass. In the past I always used cut down Lake City 5.56 nato brass. This time I used mixed .223s (PMC, GFL, RP) which from what I read shouldnt have thick necks and should work for 300AAC but maybe not. Either necks are springing back or I didnt form those cases correctly or some of these necks need turning. Maybe my sizing die was lose or I might have to trim my shell plate. I'm using Lee 300AAC die set and I know these necks spring back so when I form those for the first time I do it 4 times per piece of brass. Maybe after a while i was slacking and didnt go all the way down.

Good news is that rechecked my ammo and only about 200 rounds didnt go flush with my Hornady cartridge gauge so its not a total loss. About 400 are still good but i want to manually cycle some through my AR as i find that to be the best test. If they dont chamber all the way or stick on extraction something is not right. It was late last night and I didnt want to play with loaded AR even if its in my basement aiming at my wall I'm still scared of slam fires. Only had one but i didnt want to chance another in the middle of the night. I'll play with it later on today.

I'm going to trim my shell holder which I think is a good idea and cant really hurt. That should bring my sizing die down little bit which is where i think the issue is.

By the way loaded rounds that I ran through sizing die w/o decap pin are no go. I pulled one of those and they were swaged down to .288 so way to small. I think lksmith your right I'm not going to even shoot those. I would expect same results as yours.

[Omega]

Crimp is flaring case mouth? what??? that doesn't make sense. Also "trimming" shell plate one or two thousands of an inch won't make any difference whatsoever. I would say start with 10 thousands. Plunk test for 300 blk? My understanding plunk test applies to pistol rounds dropped in the barrel. How are you supposed to take the rifle barrel off and drop a round in to it?

Sent from my SM-G950U1 using TapatalkYes, if you lower the die before you set the seater the crimper will actually flare the case, not so much at the mouth but just below it.

[Texas by God]

Yes, if you lower the die before you set the seater the crimper will actually flare the case, not so much at the mouth but just below it.
Yes, if the body of the seating die is too low it will try to crimp the neck- resulting in a bulge on the neck or shoulder. Never let your seating die touch your shell holder. If you want to crimp, a Lee FCD is called for.

[marek313]

Yes, if the body of the seating die is too low it will try to crimp the neck- resulting in a bulge on the neck or shoulder. Never let your seating die touch your shell holder. If you want to crimp, a Lee FCD is called for.

I agree with you guys I dont crimp with my seating die i use FCD for that.

[DrewSeeg]

For cycling your round in the house, I'd just take out the firing pin. You could still get a slam fire if your primers are not fully seated but highly unlikely.

[Grmps]

Some of the 223/556 brass walls are to think fo convert to 300 AAC BO without turning/drilling out the neck.

Good
ADI PERFECTA
Aguila PMC
A USA PS
FC PSD
GFL RA
HB RP
Hornady SSA
Hornady (nickel TAA
IK03 Tula
IMI TW
IVI TZZ
LC WCC
M193 Winchester
Norinco WIN NT
NOSLER WMA 15



Thick neck wall, bad without neck turning:

AB 556 L2A2
ATI MKE13
CBC MPA
CJ6 Norma
CJ 8 NPA
DNL PMC
FNM PMP
FRONTIER PPU
GECO RAM
Hot Shot RORG
HRTRS RWS
ICC S&B
IK03 SADU
IMI TAA
IVI SADU
KFA Wolf Brass

[marek313]

For cycling your round in the house, I'd just take out the firing pin. You could still get a slam fire if your primers are not fully seated but highly unlikely.

Thats a great idea. I'll have to do that from now on when I manually cycle rounds like that.

[marek313]

Some of the 223/556 brass walls are to think fo convert to 300 AAC BO without turning/drilling out the neck.

Good
ADI PERFECTA
Aguila PMC
A USA PS
FC PSD
GFL RA
HB RP
Hornady SSA
Hornady (nickel TAA
IK03 Tula
IMI TW
IVI TZZ
LC WCC
M193 Winchester
Norinco WIN NT
NOSLER WMA 15



Thick neck wall, bad without neck turning:

AB 556 L2A2
ATI MKE13
CBC MPA
CJ6 Norma
CJ 8 NPA
DNL PMC
FNM PMP
FRONTIER PPU
GECO RAM
Hot Shot RORG
HRTRS RWS
ICC S&B
IK03 SADU
IMI TAA
IVI SADU
KFA Wolf Brass

I saw that list thats why I only selected PMC, GFL and RP brass. I have rounds that chamber and dont chamber with all headstamps so it doesnt appear to be head stamp specific. I think this is more of an issue with my brass forming but thank you for info.

[Motor]

I was about to say STOP !! when I read that you ran your loaded ammo back into the size die but saw that you found out how bad of an idea that is. It totally destroys all of the neck tension because of the swedging of the bullet.

Hope you get figured out.

Motor