What to do with this OCW workup (.308, 180 gr SST bullets, IMR 4064)?

gasdoc09

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Aug 14, 2010
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Some time ago, Midway had blemished 180 gr .308 ballistic tip bullets on clearance, so I bought a bunch. I'm reasonably confident they're Hornady SST bullets.

Finally got around to using them, so I loaded some up in once-fired Federal M1A brass (same as FGMM brass as far as I can tell). Rem 9 1/2 primers, 4064 powder. This is what I got:

41.4 - 0.87"
41.8 - 1.19"
42.2 - 1.07"
42.6 - 1.23"
43.0 - 1.21"
43.4 - 0.71"
43.8 - 0.39"
44.2 - 0.85"

43.8 looks encouraging, but the case is really full. I had originally planned to try up to 45.0 but there was so much crunching and compressing at 44.2 that I didn't go any higher. (IMR's load data goes to 45.2 gr as a compressed charge in Winchester cases, 24" barrel, presumably a bolt gun.)

fed-180sst_zps5796605a.jpg


(For the bottom 3 groups, my POA was the bottom row of diamonds. There wasn't a 2" drop in POI going from 43.0 to 43.4.)

This bullet was really uninspiring until 43.4 ... here's the issue though. I know primer reading in semi-autos is voodoo but 44.2 looked a little flat. Any advice as to whether it's a good idea to work up a load that's probably kind of hot for my gun? I sure wouldn't expect to get many loads out of Federal brass up there.

I didn't take the chrono to the range (left it in the other car :() so I don't have velocity data for these loads.

Thanks.
 
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The point of OCW is to find a range of charge weights that have the same POI and tune the accuracy by tweaking the seating depth. This way you get a load that is insensitive to small variations in charge weight. 43.4 - 44.2 all look like they have the same POI. The group sizes themselves look like there is some potential there already. Personally, I would load a 5 round set of 43.4, 43.6, 43.8x2, and 44 and then a 5 round set of all 43.8. If the first 5 group under MOA, and the second 5 group at whatever you consider acceptable, I would call 43.8 your charge weight. Otherwise try adjusting the seating depth to get the accuracy you want.

Edit - Are you seeing heavy extractor or ejector marks on the rifle? Any other signs of excess pressure?