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Old 10-08-2011, 11:30 PM
MMA10mm MMA10mm is offline
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I was in a group buy for a custom mould that duplicated the Lyman 358156 bullet, but without the gas check, and with the lube groove moved to center it between the new plain base and the first crimp groove. This bullet has dual crimp groove design, so part of my curiosity/interest was trying this boolit in all of its loading possibilities.

To that end, I grabbed a box of 1x-fired 38 brass which I had previously fired as factory loads in the same revolver about 15 years ago. They're nickle-plated Federal 38s. Sized, primed (WSPs all from same box), and flared the brass, and decided I'd add some Winchester brass in 357 (all from their own same lot) for a full-length loading option and prepped them the same way as the 38s. All the boolits were sized .358" and lubed with 50/50 alox/beeswax only in the lube groove. Alloy was WW +2% tin air-cooled.

I chose 2 loads, both with W231 (all loads loaded out of the same can of powder); 4.4grs & 5.6grs. I loaded both charges in the 38 cases at both the upper crimp groove (loaded short) and the lower crimp groove (loaded long). I also loaded the 5.6gr load at the upper crimp groove (loaded short). Here's how the COALs worked out:
38 Spl (loaded short): 1.442"
38 Spl (loaded long): 1.527"
357 Mag (loaded short): 1.5865"

The test gun is my S&W 686-3 "Midnight Black" (blued stainless) 4"-barreled former duty sidearm. This gun has shot perfect scores with issue factory reloads, so I have confidence in its accuracy abilities. I recently gave this revolver a thorough cleaning in the cylinder to get rid of carbon ring build-up.

The results were interesting. I tried to do accuracy testing simultaneously, but a problem with targets came up (I forgot them...), so only chrono data for now.

38 Spl (loaded short) w/ 4.4grs gave the following velocities (FPS): 875, 900, 895, 882, 877, 890. The average was 887 fps with an ES of 25.

38 Spl (loaded long) w/ 4.4grs gave the following velocities (FPS): error, error, error, 818, 849, 831. The average was 833 fps with an ES of 31. (The errors came from a swarm of tiny insects I didn't notice hanging around the stop screen until the third shot...)

38 Spl (loaded short) w/ 5.6grs gave the following velocities (FPS): 1069, 1095, 1062, 1085, 1079, 1075. *The average was 1078 fps with an ES of 33. (This is NOT a safe 38 load - it's only for use in 357 Magnums!)

38 Spl (loaded long) w/ 5.6grs gave the following velocities (FPS): 1036, 1027, 1026, 1035, 1035, 1018. *The average was 1030 fps with an ES of 18.

357 Mag (loaded short) w/ 5.6grs gave the following velocities (FPS): 1020, 1067, 1046, 1055, 1049, 1053. The average was 1043 fps with an ES of 47.

Note that this is all very consistent with conventional wisdom, with the exception of the 357 with a longer OAL giving higher velocities. My only thoughts are that the Winchester Magnum brass has less capacity, even with a minimally longer COAL.

Although I didn't have targets, I did notice the 5.6gr loads were noticably less accurate than the 4.4 loads. Didn't matter whether it was long- or short-loaded or loaded in the 357 case. I personally believe this has more to do with the powder than anything else. W231 doesn't "like" higher-pressure loads. It can certainly be safely loaded hotter, but accuracy tends to suffer. I've seen this same characteristic in 44 Mag and 10mm Auto loads too (but curiously, not so much in 9mm, where 231 works fine at ~30k psi).

I've used a couple hundred pounds of W231 and have noticed that ocassionally, the burn rate varies wildly in particular lots. Sometimes slower, sometimes faster. I recommend strongly that you use a chronograph, and load to about 800-850 fps, and call it good in the 38 with a 158gr bullet.
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