glock21 & j-bullets

[siamese4570]

I just got a batch of Rainer 230 gr 45 j bullets. Checking a 2008 Speer Manual for 45 acp 230 fmj loading data showed a max load for Bullseye at 5.7. Loaded 5.2 and 5.4. The 5.2 grs chronographed at 825 and 774 fps. The 5.4 chrono'd at 894 and 853 fps. That seems a little warm, but it shot the best groups that my glock 21 ever shot. Don't see any pressure signs like flattened primers or ejection of the cases across the range, but don't want to strain anything. My older manuals stopped at 5.0-5.1 grs. There are a couple of factors that may be contributing to the higher velocities.
1) The rainer bullets have a longer (more pointy) nose than the remington bulk bullets that I was using. The Remington has a blunter nose. This long nose would result in less contact between the side of the bullet and the barrel.
2) Does the funky polygonal rifling in the Glocks result in higher velocities?

I'd be interested in hearing anybody elses experiences with glocks and chronographs.

Siamese4570

[MakeMineA10mm]

Another thing to consider is that plated bullets are kind-of half-way between cast and jacketed. They definitely give less resistance than traditional fully jacketed, and that factor will also contribute to higher velocities, although I don't disagree with your thoughts about bearing surface either...

My standard load for 45ACP in my Glocks (and all other 45s, including a Thompson, many 1911s, and an HK45) is 5.6grs of W231 w/ 230gr LRN. I shoot it through my polygonal barrel, even though I'm not supposed to. (I'm a factory-certified armorer - my dept. sends me every 2 years - and I check for leading and clean often.)

Your loads definitely sound warm, but, again, plated give less resistance than traditional jacketed, so that may be helping you. Another thing I've noticed about Bullseye is that although it's generally faster-burning, it gives lower pressures and decent velocities to many (very slightly) slower powders, like W231, Red Dot, and 700X... It's one of the well-known characteristics of Bullseye.

I don't think the velocities are "too high" regardless. 825-870 with a 230gr FMJ is pretty much identical to military ball. I'd call that load "just right." :-D

[MakeMineA10mm]

Oh, and as far as Glocks go, I believe the OCTAGONAL rifling in the 45s make them PARTICULARLY accurate compared to all other Glocks, which have hexagonal rifling. A general consensus is that this is attributable to less bullet distortion, but I like to narrow it down to the idea that it's easier for the bullet to form-fit to the 8-sided barrel than a 6-sided. Still less distortion, but more specific as to what is working to our advantage.

So, yes, polygonal rifling seals better than traditional-style rifling, which in turn, generates higher velocities, GENERALLY. (There's always exceptions when comparing particular examples, but compare 1000 Glocks to 1000 conventionally-rifled guns of a particular caliber, and the Glocks overall velocity will come out slightly ahead.)

[siamese4570]

MMA10: Thanks for your replys. Think that I figured it out last night. Looked at the invoice from Midway and the Ranier bullets are .451" dia. Typically 45 auto bullets are .452", at least that's the dia of the bulk remington bullets that I was using before.

Siamese4570