More Homemade 10mm Fun!

So I rolled some more 10mm last week when I was off, and today I took it out to see how it'd do -- same load I took out last week. For the record:

155-gr. Hornady XTP
14.3 gr. Accurate Arms No. 9
1.250" OAL

I did, however, have a better setup for the chrony this week, namely a little tripod from Walmart to mount it on further out from where I was shooting.
I got out there, got the chronograph set up initially about 8 ft. from the muzzle, loaded the mags and started blasting away at the 7-yard mark -- one ragged hole, with a couple of stray shots here and there. Muzzle velocities from 8 feet, in feet per second:

1352
1338
1362
1345
1339
1328
1338
1353
1356
1328

Average:1,343.9 fps
ES: 34 fps

I was a little suspicious still, though, considering Accurate rates my load at 1244 fps. So, I moved the Shooting Chrony back a couple of feet, diffusers in place, and reeled off some more.

Velocities @ 10 ft:
1374
1366
1331
1343
1353
1335
1345
1350
1359
1347
1394
1393
1343
1345
1311
1366
1295
1359

Average: 1350.5 fps
ES: 63 fps

Velocities @ 20 feet:
1288
1345
1345
1310
1356
1374
1343
1343
1355

Average: 1339.8 fps
ES: 86 fps


I don't know how the extreme spread got wider as I moved the Chrony back; it might have something to do with premature unlocking on some shots, maybe a stiffer recoil spring might help, I don't know. In any event, though, I found the XTPs quite manageable even at those velocities -- if indeed they were accurate. Perhaps a stiffer spring might help with diagnosis. In any event, it was yet another successful outing. I think I'm getting the hang of this handloading thing. ;-)