several rounds locked in chamber

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several rounds locked in chamber

Postby jgilesg » Mon Jul 17, 2017 4:28 pm

Hey all
I had an issue this weekend with my 450, its a Colt lower and a Bartz upper.
I had several rounds FTF and the round was stuck in the chamber, I had to use a lot of force (rubber mallet on one) to get the BCG back to get the round out. I'm pretty sure it was "pilot error" but thought I would ask to hopefully confirm. I crimped them with my LCD into a cannelure in 200 grain barnes, I also did a taper crimp on them. When I got home and checked the remaining rounds the taper was at about .473-.474. My assumption is the taper was a bit much on a few and they didn't headspace properly, hench the FTF. One of them even had a very light strike on the primer.
I remember seeing someone had a head space gauge on here, I think it might be wise to grab one, if you recall who sells em.
I can give all specs on the round if necessary when I get home if needed.

Thanks guys
JG
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Re: several rounds locked in chamber

Postby Jim in Houston » Mon Jul 17, 2017 7:39 pm

Somewhere on the forum is a thread where Hoot did some experimenting with crimp diameter. As I recall, he went down to .46 something and the round still headspaced correctly.

I've had failures to eject on an AR with a really tight chamber, which is why I no longer shoot steel cased ammo in that particular rifle. The expansion of the casing when fired basically caused it to weld itself to the inside of the chamber. That shouldn't happen with brass, but you may want to check the dimensions of your chamber to see if it a tight fit.
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Re: several rounds locked in chamber

Postby Al in Mi » Tue Jul 18, 2017 6:04 am

can you post a pic of those sticking rounds?
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Re: several rounds locked in chamber

Postby jgilesg » Tue Jul 18, 2017 9:13 am

I did what I should have done before posting my issue, that is do some searching on the forum for similar issues and found several, as well as, the chamber gauge Hoot mentioned.
I have put in the neighborhood of 500 rounds through my 450 upper with zero issues, so I am pretty confident it isn't the chamber or BCG causing the problem. I pulled all the rounds in the lot that I had the problem with so sadly I don't have the ability to send pics. I had 2 different lots with me when shooting and the other lot functioned fine. They were both 200 Gr Barnes, just different powder charges. Hopefully, by eliminating the one lot, the problem is solved.
I just called Tronix and ordered a chamber gauge so I can test future reloads.

Thanks guys
JG
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Re: several rounds locked in chamber

Postby Hoot » Tue Jul 18, 2017 11:06 am

Sounds like either you forgot to full length resize a few, or the case head has grown beyond spec. Using an accurate micrometer, the diameter just above the web should not be over .5015. I have a peanut butter jar of cases I can no longer reliably use. In the case of my particular Bartz chamber, they start binding at .5017, so to be safe, I draw the line at .5015. My old 20" Bushmaster would take them up to .5022. With hot loads, the case head grows out of spec around the 4th or 5th reload. Hardly any growth with tame loads. I have used some really odd crimps overs the years and never had the crimp cause a case to bind.

Hoot
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Re: several rounds locked in chamber

Postby jgilesg » Tue Jul 18, 2017 12:30 pm

Thanks for the information Hoot.
One, maybe dumb, question. What is the web?

"the diameter just above the web should not be over .5015."

JG
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Re: several rounds locked in chamber

Postby jgilesg » Tue Jul 18, 2017 12:33 pm

Jumped the gun. Quick web search and I know what web is
JG
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Re: several rounds locked in chamber

Postby Hoot » Tue Jul 18, 2017 1:07 pm

jgilesg wrote:Thanks for the information Hoot.
One, maybe dumb, question. What is the web?

"the diameter just above the web should not be over .5015."

JG


If you look down in an empty case. The area where you see the flash hole is the front of the web. Generally speaking, its the area that is solid brass which surrounds the primer. Case head growth is usually most obvious where the case wall meets to the web. It is the "weak link" in the chain. It is also where case head separation occurs in the event of a failure.

SAAMI Spec for that portion of the case which just so happens to be the widest point is .5000 and the chamber is spec'd to .5010 in a perfect world. If you set your micrometer (not caliper) to .5015 and let the case drop through, if it passes through, it passes. You can also order a gauge from Tony. No two chambers are cut the same due to wear on the reamer. Find what your chamber likes by running through your cleaned, resized empties. If they're getting long in the tooth, you will find a few that won't drop into the chamber without a little help. mic those and you will see what diameter to cull your cases at. Write it down in your cookbook for future reference. I check my cases each time I resize them. It is really inconvenient to have to pry your action open on the firing line. I've had to tap with a brass rod down the barrel (not safe) with one hand, while prying the action with the other hand. Awkward! Now, I just cull them in advance.

The peanut butter jar is also the recipient of cases that have grown shorter than 1.685 (OK to use a caliper here). Think about it. The taper crimp relies upon the case length to impart the same degree of retention from one reload to the next. A lot of the velocity SD observed in this caliber with lighter bullets is due to not sorting your cases by length. I usually group them within a few thousandths of each other, when I'm loading my tray full of re-primed cases, ready to go. IE 1.685-1.687, 1.688-1.690, 1.691-1.693, etc. Not important for blammo-ammo though. ;)

Sorry for turning this into a chapter from "War and Peace".

Hoot

EDIT:I am work and it took me a while to type this. Longer than your search. :lol:
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Re: several rounds locked in chamber

Postby jgilesg » Thu Jul 20, 2017 9:23 am

Well Hoot, as usual, you were right.
I checked the sizing die and I wasn't sizing the entire case. I use the Hornady lock and load adapters, so in theory, you set it and forget it. I must has set it up without the adapter so the die was short of sizing the entire case. I resized the cases and the "Thunk" test went as it should.
Thanks again all
JG
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