First post here. I've been lurking for quite some time and learned a great deal from everything I've read. So thank you!
I recently started casting for a MGM 16.25 inch barreled Encore in 357 Magnum. It shoots jacketed amazingly well and the LEE 358-158-RF into very pleasing groups.
Well I decided I wanted to try something heavy, slow, and quiet so I ordered a NOE 360-225 SWC. Here's where the problem starts...
I literally miss a 18 inch target at 50 yards with most shots. I've tried the bullet with 3 different powders, many different speeds, and 2 different alloys. Haven't remotely begun load development because I can't hit the target. The shots that do hit are rarely clean SWC holes. No keyholing but perhaps a slight oblongness maybe. Not oblong enough that I'd have even noticed though unless I was looking for a problem.
I have other NOE molds and their push through sizer. Sizing the 158 and the 225 to .359.
Barrel is 16 twist. The actual rifling of the barrel is only approx. 15 inches long obviously because of the chamber so best I can figure with a tight cleaning rod is it's AROUND a legitimate 16 twist barrel. Bullet is plain based and right at 0.95 inches long.
I've tried many different subsonic loads and 1 super. Sub was with Clays, Trailboss, and middle of the road H110 loads. Super was with a higher H110 load. All shot exactly the same just with varying levels of noise. I only tried supersonic after all the other subsonic loads failed to reliably hit the target. I could try other powders obviously but I don't want to keep wasting components if I can't even hit the paper.
I'm at a loss here! My first instinct was twist rate but I'm getting close enough to the advertised 16 twist that it doesn't add up. If my math is right this bullet should have ample stability in anything in the neighborhood of 20 or less.
I did slug the barrel but what an absolute pain that was to measure. 5 groove rifling. I don't remember what I got but I know I didn't trust my measurements. Neighborhood of .356 I THINK using an aluminum can shim wrapped around the bullet and then subtracted out.
I've also captured numerous bullets in putty. No sign of gas cut bases or widening rifling marks. Bases all end up slightly concave with sharp trailing edges. Gas seal looks good to me. I even seated bullets and then pulled them to see if my brass was overly sizing them. Difference was only 0.0005-0.001 and as I said no gas seems to be leaking by and there doesn't seem to be any skidding.
Alloys used have been straight Lyman #2 and 50/50 Lyman/pure. Pan lubing with mix of floor wax, Vaseline, paraffin, and a little synthetic motor oil. No leading to speak of.
Anyone got any ideas?? Like I said I'm at a loss at this point.