300 Blackout help

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getgone

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OK so I am new here and new to reloading and I am having some issues.
I am using:
Lightning ammo brand brass (according to them once fired and covered 223 cases)
Barnes Tac-Tx 110gr black tip bullets-
Federal 205 primers
Winchester 296 powder

The rifle is:
1/8 twist 8.5 inch Rainer Arms barrel-
Rubber city armory bolt carrier
Adjustable gas

I made 3 test loads and had some strange results. I used 18.5 grains of w296 to start. Then also made a 19.0 and a 19.5 load. All of the 18.5 shot fine but had small ring toward the bottom of the case. Looks just like incipient case failure.

Started shooting a few of the 19.0s and had on break in half. No damage to the gun, round left the barrel no strange sounds. Back half of the case ejected, the front stayed in the chamber. A few taps on my hand and it fell right out.

Moved up to the 19.5s and had another piece of brass come out with the same ring as the 18.5 just more profound.

I am trying to figure out either what is wrong or what I am doing wrong. Any feedback would be appreciated.

I should also mention that I have shot 100 rounds of fiocchi 150 grain factory ammo with 0 issues.
 
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Some more experienced folks running hot loads will need to jump in here. But on the bottom of case, is that a deep marking left from the breech face?
if
The round on the left is, as you bought the brass, it looks like it already has case failure on the brink right where the other cracked. Can you cut one round in half, cut away style, so we can see what the insides of these cases look like? Maybe a bad annealing job?
 
WOW....lots of pressure signs there. The circular spots on the bottom of the case is from the ejector. You dont get marks like that until pressure is up there.

Acordding to the Nosler manual 19.5gns is right at max. Other data may vary.

Im curious why, after seeing "imminent" case seperation, you went ahead and shot the increased powder charged loads?

You need to CAREFULLY inspect the brass you have. Maybe cut a cpl of pieces in half, lengthwise. Once fired and converted brass should not separate like that with a safe load. With internet obtained brass...?????


If the brass shows ANY sign of stretching inside...toss the lot. If it looks good then start at the low end of the load data and SLOWLY work up. I go up in 0.2 grain increments when developing a load for a new gun

Some guns develop unsafe pressures at below max listed loads. Work up carefully
 
The brass I got from a local outfitter. Hoestly I didn't know if this was a pressure sign or a junk brass sign. I didn't notice all the other marks until after I was done shooting. The Barnes info I found on their website states 18.2 minimum max 20.2. I don't really have great access to a range so I made the 3 loads 4 each and took them all to test. Started with the lowest and no issues that I originally seen. What confuses me is I made 4 at each level and the 3 pictured are the only ones that had problems.
 
Where was the brass being ejected? If short and towards 1 or 2 o'clock you are most likely overgassed. Bolt is unlocked too high in the pressure curve causing the symptoms you see.
Just food for thought.
 
I guess my next stupid newbie question is what do I do now? Try new brass? Start of again with even lower loads?
 
Shouldn't be an issue with military brass. You can run a paper clip on the inside to see if you feel a hump where separation may be beginning. From the pressure signs on your brass, I would start over, double check my scales and start at a lower load.

If you could show a pic of the brass as you bought it, and cut one in half vertically, we can see if there is an issue with the brass itself

When the bottom of your brass takes on shapes from your bolt, you are way over pressure. What's causing it could be several things, seating too deep or bullet setback during chambering, miscallibrated scale or misused scale, accidently grabbed wrong powder or an actual issue with the gun itself. Either way, your most likely too hot. You can rule pit the brass though by careful inspection, but its very unlikely you would have several pieces of brass fail at the exact same time.
 
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You are very lucky! I would back that load down to around 16gr and slowly work it up. I'm running 17gr of 296 pushing a Sierra 125gr Prohunter and have never had a overpressure issue. Barnes may say one thing but what does the powder manf say? I would trust a powder manf load data over a bullet manf.
 
Gas is turned to the lowest setting that I still bolt hold open on an empty mag. Hodgdon load data says 18.8 starting and 20.0 max for a 110 grain Hornady bullet.

Heads pace as in on the rifle or with the brass? I Bought a brass heads pace checker and the brass fits I'm just fine and doesn't protrude past the end.
 
#1 I do think from the look of those primers those loads are too hot for your gun. I recommend toning them down a bit.


#2 for the cracked case. Thats not case head separation and it is not were a case stretches when the head space is out.
I may be wrong about that, but the 1st thing I noticed is the lines are pretty equal between the cases.
I bet they were caused by the tool that was used to cut the brass to size.
They look like a score mark to me.
Might be causing weakness in the brass similar to cutting glass.

Was the brass annealed? If it was maybe they annealed them too far down along the side of the case. You want to anneal just the neck.
Maybe could get results like that if the top 1/2 of the case is allot softer than the bottom.

I guess it could be a gas issue too. if the bolt goes back before the pressure drops in the case. Something is going to get tugged.

Just some ideas.
 
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Thanks for the reply. None of those marks were on the brass before I shot it I think I'm going to tone down the charge first and see where that puts me. I'm more worried about head space issues.

When I shot factory loaded fiocchi 150 grain I had no markings no breaks no issues at all. Wouldn't I have problems with those too if I had headspace problems?
 
When I shot factory loaded fiocchi 150 grain I had no markings no breaks no issues at all. Wouldn't I have problems with those too if I had headspace problems?
Click to expand...

I would think so. Pretty rare to have head space issues with an AR. Does happen, but its a pretty idiot proof design.
Tolerance stacking maybe between the extension and the bolt. Could try a different bolt.

Reload some of the fiocci brass and see what you get.
 
The more I am thinking on it. the more I agree its a over gas issue.
Esp with a short barrel/ Short gas tube.

Think about it. When the round goes off. There is extreme pressure pushing the brass against the sides of the chamber.
You dont want the bolt pulling back on the case until the pressure has eased to allow easy extraction.

Pretty common issue with the sort barrel AR's.
 
So I adjusted the gas to function with the fiocchi ammo. If I adjust the gas down further, you think that could help? I just noticed a little bit of back by the gas port coming from under the gas block.

Also I don't have any of the fiocchi brass as I wasn't loading back when I finished the rifle lol. Wish I would have kept it now.
 
The brass that I am loading into is LC09 and LC12. The neck wall thickness is around 0.013 and 0.014. Isn't that no good?
 
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