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Posted: 3/5/2011 10:11:18 AM EDT
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I'm wondering how much variance in OAL is acceptable. Here's why I ask...
Loading a batch of 40 S&W on a RCBS single stage press. I'm going for an OAL of 1.125 and I've set my die up on one "example" that is exactly 1.125. However, in a batch of 50, I'm seeing what I consider to be pretty large variances off that number. I'm considering 22 of them out of spec for my comfort (anything less that 1.124 and anything 1.127 and above). I'm using an RCBS die that seats and crimps in one step. I've got one of those 22 that measured at 1.120; most are above (1.127 to 1.130). The one that was 1.120, I gently "pulled" (without dumping the powder) and reseated it. This time it measured at 1.1205 - seems to point to something specific with that brass / primer / bullet. I've verified that I don't have any high primers and I'm triple checking each measurement with my calipers. The die is locked down and the seating plug is locked down. 
The follow-up question is what's causing the variance... The brass is mixed.... and I don't trim them. But, unless I'm not thinking through this right, brass length should have nothing to do with OAL. I've tested the theory that length of the brass is the issue, but it doesn't seem to bear out. I've loaded a bunch of 40 S&W in the past and have never seen variances this large. It is a new box of plated Xtreme bullets that I'm working from - but they're the same weight and profile as the last group of Xtreme that I bought, using the same die / seating plug / etc. |
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Some sort of variation in your plated bullets vs how they meet the seating plug. You could try less crimp, but I wouldn't even bother raising an eyebrow at 0.010" variance. Since your brass isn't trimmed, if you're also crimping with the die, you're getting variable crimp. |
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Set your seater and just make "spot checks." They fit the gauge.......GTG.
Just for grins let me show you something............ so, I measured a variety of different 45ACP rounds. I got these for FREE w/o the boxes.
NEW WW silver colored HP 1.213" 1.212" 1.206" 1.211" 1.215" NEW WW black colored HP 1.208" 1.209" 1.209" 1.209" 1.209" *NEW WW SWC Jacketed looks like the Match 185 gr. 1.185" 1.184" 1.184" 1.183" 1.184" NEW FED SWC Jacketed looks like the Match 185 gr. 1.265" 1.263" 1.264" 1.265" 1.265" NEW FED FMJ 230 gr. 1.265" 1.265" 1.266" 1.267" 1.268" CCI Blazer FMJ 230 gr. 1.260" RE-Loads 200 gr. LSWC 1.236" 1.246" 1.248" 1.243" 1.250" FYI.......and the ONLY cartridge lot that DIDN'T PASS my M1911 barrel hood test is noted *in red. The case head stood a little higher than the barrel hood extension. YES, even though the OAL is shorter……it actually was too long and sat higher than the barrel hood extension (the actual bullet shape made the difference). Aloha, Mark |
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