Blackout chamber out of spec?

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gvanzeggelaar

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I just bought an NEA 300blk barrel with the intention of shooting cast through it.

I cut down and sized 223 brass. It was all well within sammi spec. The neck was +- .326. The brass also dropped into the chamber freely.

Now when I loaded a .311 projectile it bumped the neck up to about 0.330 - 0.333. The ones that measured at 0.330 will chamber freely. Basically anything above that will jam in the chamber and take excessive force to remove. It is not the bullet jamming, but the case neck. There are no marks on the lead and they were seated in far enough. The saami spec for the chamber at the neck is a min of 0.335

Is this normal, and if not is there a way to open the chamber up a bit.
 
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That's normal for the NEA 300BLK barrels as I found out. They're reamed pretty tightly. I thought my rounds were jamming into the lands but it was just a very snug leade.
 
I think before you start saying things like is the MFG made the part out of spec you should try factory ammo in it first.
or at least factory brass,
what dies are you using to re size the 223 brass, ive had a few issues with die sets, and now using Hornady.
bbb
 
Do you have a lee factory crimp die? Had the same problem with a match barrel lee fcd fixed all my problems.
 
Generally it's normal to shoot slightly larger diameter cast pills, around 0.001" to 0.002" larger. 0.003" seems a bit big but I've read folks shooting 0.311" out of the M1 just fine. Take that with a grain of salt 'cause it is the internet. Keep in mind, those NEA barrels are TIGHT, might want to reconsider using those 0.311 pills. :p
 
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Paladin308 said:
You are correct. I'm not sure why the OP is using .311 projectiles :confused:
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also some brass is thicker and might or might not be a problem using cast boolit of .310-.311 diameter

a cast bullet of .311 is normal in a .308 ---->.308 plus .002 =.310 = no leading (using a GC in rifle loads)

try some different brass or .310 diam
your nose also might be to big
what bullet are you trying to use ?
 
gvanzeggelaar said:
I just bought an NEA 300blk barrel with the intention of shooting cast through it.

I cut down and sized 223 brass. It was all well within sammi spec. The neck was +- .326. The brass also dropped into the chamber freely.

Now when I loaded a .311 projectile it bumped the neck up to about 0.330 - 0.333. The ones that measured at 0.330 will chamber freely. Basically anything above that will jam in the chamber and take excessive force to remove. It is not the bullet jamming, but the case neck. There are now marks on the lead and they were seated in far enough. The saami spec for the chamber at the neck is a min of 0.335

Is this normal, and if not is there a way to open the chamber up a bit.
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1. The use of the .311" bullet is what is causing the issue. Go to a .308 bullet and you won't have any problems.

2. If there are rifling marks on the bullet then by definition you have not seated the bullet in far enough. As you are hand loading there is no issue with seating the bullet a bit deeper.
 
Trinimon said:
Generally it's normal to shoot slightly larger diameter cast pills, around 0.001" to 0.002" larger. 0.003" seems a bit big but I've read folks shooting 0.311" out of the M1 just fine. Take that with a grain of salt 'cause it is the internet. Keep in mind, those NEA barrels are TIGHT, might want to reconsider using those 0.311 pills. :p
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There is no issue with using the larger bullet in a .308 bore but the 300 BLK has always been a bit finicky with respect to neck dimension when using cut down 223 brass. I was out with CR5 the other day and some of his reloads wouldn't chamber in my rifle. I have never had any issues with any of my cut down Fed cases and I do not neck turn so AFAIK my chamber is good ... yet none of his rounds would chamber in my rifle.

The suggestion I'd make to the OP is to settle down, switch to a .308 bullet, seat the bullets deep enough to clear the rifling and "chive on." :D There is zero point in buggering around with trying to open up an existing chamber unless there is an actual issue with factory rounds. Even if the chamber has an issue with factory rounds, as long as he is exclusively reloading then it makes no difference as he can tailor rounds to his chamber.

Keep in mind that barrel manufacturers are constrained by the chamber reamers they use. Those reamers are made to comply with the SAAMI spec to ensure they work with factory ammo. Barrel manufacturers generally have no ability to adjust chamber dimensions beyond the headspace.
 
To answer a few of the questions;

I am using a Hornady die set.
Winchester brass - Thinnest neck of the brass I have
Bullet is a NOE 311299

I built this rifle with the sole intention of shooting cast in it. I measured all the rounds before I even ordered the barrel to make sure this wasn't going to be an issue. Again, the min spec from saami is .335 at the neck, not .332,
 
Suputin said:
There is no issue with using the larger bullet in a .308 bore but the 300 BLK has always been a bit finicky with respect to neck dimension when using cut down 223 brass. I was out with CR5 the other day and some of his reloads wouldn't chamber in my rifle. I have never had any issues with any of my cut down Fed cases and I do not neck turn so AFAIK my chamber is good ... yet none of his rounds would chamber in my rifle.

The suggestion I'd make to the OP is to settle down, switch to a .308 bullet, seat the bullets deep enough to clear the rifling and "chive on." :D There is zero point in buggering around with trying to open up an existing chamber unless there is an actual issue with factory rounds. Even if the chamber has an issue with factory rounds, as long as he is exclusively reloading then it makes no difference as he can tailor rounds to his chamber.

Keep in mind that barrel manufacturers are constrained by the chamber reamers they use. Those reamers are made to comply with the SAAMI spec to ensure they work with factory ammo. Barrel manufacturers generally have no ability to adjust chamber dimensions beyond the headspace.
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First thing I did when I got home was test my handloads in the new 300BLK barrel for my ACR and they drop right in :D
I measured every dimension of the loaded cartridges and compared them to the factory loads I have and they were the same. Not sure what happened that day but I can't find any reason they wouldn't chamber in your rifle.

OP, I would try 308 projectiles before any other troubleshooting. If there is still a problem it may be seating depth. If you still have problems after that try a different bullet, I've had great results with 110gr V-max, and 150-165gr Hornady SST's.

Good luck
 
I hope that you continue to share your experiences and reloading methodology and loads. I'm looking at a 30 cal AR down the road and deciding between the blackout and 308. There's a lot to be said for the blackout.

I'll be shooting cast bullets as well.

It couldn't hurt to try sizing to .310 or .309 and see what sort of accuracy you get. For years, before the Internet, my father always sized to .308 for our 30 cal stuff and I don't recall it ever being poor. I've been sizing to .311 only because the Internet told me to lol
 
Thanks for the help guys.

I'm going to do one or more of the following:

Size to 309
Neck turn cases
Buy some factory ammo/brass
As a last resort try to lap the neck area of the chamber a couple thou.
 
One Lung Wonder said:
I thought it was a no-no to shoot cast bullets in self shuckers.
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you can shoot cast in almost anything
anything gas operated has to have a gas check= stop leading (or 99.9% in most cases)
I have heard of people using lead GC bullets with no problems in
223 AR
300 Black AR
308 M1A
30-06 m1 Garand
you just have to load differently and know your limitations
bullet fit is the key
 
Trinimon said:
According to SFRC, the NEA 300AAC Blackout barrels uses polygonal rifling. Just got to keep an eye on the leading if you're shooting cast.
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Good point, just like a Glock or HK barrel, if you let the lead build up you can end up with high pressures from a load that was good a few hundred rounds earlier.
I've switched away from shooting non jacketed bullets in all my guns, I don't cast my own and decent hard cast retails for the same price as jacketed.
 
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