Time to pull a bunch of bullets [Archive] - Glock Talk

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Carphunter
07-03-2012, 06:36
So, I'd made up a 100 or more 11.2 BD under 180 XTP rounds for my Glock 6" factory barrel.

Testing in the past said this was safe in this barrel.

I'd checked to see that my 550 wouldn't throw any exceptionally high loads that I'd have to worry about op.

Well... trip to the range. Fired some rounds over the chrony and was seeing inconsistent speeds... lowest I think was 1290.

What made me take notice, though, was when i saw 1600 in the bunch.

i stopped firing and started looking for brass (range hasn't enforced pickup for a while... so scrubbing through 40 and 45 cases in the natty undergrowth and grass was a pain.

Found some of my cases... including 1 with a blown smiley, and 2 more with obvious smileys. Something in all my hot load development I'd never seen before with this barrel.

This is all multi-reload brass, so I'm sure I just asked too much of it.

Gonna pull them all, and reload with around 10.5 grain BD.

Fun stuff.

Oh... also learned I was getting damn near the same fps from my 4" with this stuff as the 6"...and it has a looser chamber than the 6"

_The_Shadow
07-03-2012, 09:06
Carphunter, you may have seen an issue of powder particlues or gases causing the CHRONY to register a high reading. If you shoot fairly close to the chrony you can get weird reads.

Still in all 11.2 grains is stout...

Carphunter
07-03-2012, 09:08
possible... i had the chrony at 10'... and i often put it at 15' to avoid this.

i may fire some more rounds to see if the other pressure signs are common or not... or just old brass.

_The_Shadow
07-03-2012, 09:14
Some powders can be worst than others, and battery strength and lighting play into this also. Good luck!

nickE10mm
07-03-2012, 10:49
Carphunter, you may have seen an issue of powder particlues or gases causing the CHRONY to register a high reading. If you shoot fairly close to the chrony you can get weird reads.

Still in all 11.2 grains is stout...

Thats what I thought, but with finding a blown case and smilies (or frownies, as I call them).... you are prudent to back off and re-do that load-up.

dm1906
07-03-2012, 12:45
What specific components did you use: Case head stamp? primer? Brass, nickel? Trim length? What was the C.O.L.? Pictures would be helpful.

11.2 gr. BD under 180 XTP's are near full power, but certainly shouldn't be excessive. Your inconsistency is an indication of an inconsistent load, and the spread between a blowout and modest velocity confirms it. Also, the chrono shouldn't be affected at even closer range with supersonic rounds, and 10' is more than sufficient distance. Powder residue or other debris should register as a second projectile, or an error. Lighting and other factors can affect chrono accuracy, but the FPS and blown case suggests it's at least close. A more distant chrono is necessary with subsonic and transonic rounds (less than ~1150 FPS) to prevent the muzzle blast wave from registering before the bullet arrives, which causes erroneous reads and errors.

1290 FPS would be low for that charge (I get a consistent 1280-1340, depending on season with 11.0 gr), so if that's your lowest, it seems you were throwing overcharges. 1600+ FPS is 14.2 gr.+ BD (compressed), all else being correct. I test with a LWD 5.2" barrel. When loading at or near full power loads, every charge thrown should be weighed and verified. It's a PITA, but you aren't loading bulk target ammo with these.

Measure your cartridges before disassembly, ensuring you don't have a recoil set-back issue. Check the bullet friction in the case (light tap with a mallet), since you are pulling them anyway. Also measure the case head, web and OAL for expansion on the cases that didn't KB. If the load was consistent, the measurements should be, as well. This type of failure is not caused by excessive load count brass.

Chamber a fired case in the barrel to get a picture of the time of blowout. If it seats completely (bulge will nest into the ramp and case head will be flush with breach), it's overpressure. If it doesn't, you may have a timing issue (battery unlock during pressure increase). If this is the case, chamber support is irrelevant. If it was a battery unlock issue, it doesn't explain the excessive velocities, as they usually drop, not increase, with a rupture or excessive bulge.

Also note:

Although many insist on it, I don't (normally) use new/unloaded brass for carry or hunting rounds. I use once or twice fired brass, loaded with a moderate pressure charge. I've had a BAD experience with brand new brass, of (previously) known good quality: This thread, starting at post #105 (http://www.glocktalk.com/forums/showthread.php?t=1332131). If they don't KB! at one or two moderate loads, they won't at the 2nd or 3rd full power. All cases are measured for pressure indications, of course (Waters method).

When you have a failure such as this, your reloading, at least for that caliber and equipment used, should come to a complete halt, until the cause has been determined. Continuing is begging for a repeat, or worse. Every commercial range I am familiar with will ban any shooter who repeatedly shows up with overpressure/dangerous rounds, within the policy agreement. That would be a best-case scenario.