180gr lead handload and Underwood JHP Surprising Chronograph Results

[aOWENc]

Hey guys,

After gaining some advice from some guys on the forum (thanks again!) I loaded my first 10mm ammo and had some surprising results. I loaded 25 rounds using a ladder test and fired them from my Glock 20 with a KKM barrel in the stock length. Chronograph was 10 feet from the muzzle, 53 degrees outside.

These are handloads for my gun, work up in your gun to ensure your safety.

Powder: Longshot
Bullets: 180 gr FP Coated Lead from Hoosier Bullets
Primer: CCI Large Standard
Brass: Mixed (mostly S&B)
OAL: 1.260"
Crimp: .421"

8.8 Grains: 1268, 1272, 1266, 1264, 1254 AVG: 1262
9.0 Grains: 1313, 1319, 1281, 1304, 1293 AVG: 1302
9.2 Grains: 1288, 1310, 1325, 1324, 1354 AVG: 1320

I loaded up to 9.6 grains, but didn't shoot the 9.4 or 9.6 loads because I exceeded what I was hoping to get to when just using 9.2 grains of Longshot. This was very surprising to me as I didn't expect to get over 1250 FPS with anything but the 9.6 load. Brass on the 9.2 loads didnt show any obvious over pressure signs, but there were slight dents in the case mouth and a weird scuff on the side of the brass that I will try to photograph later.

The recoil was also significant and much more than the Underwood JHP I shot. I'm not sure why these were so much hotter than I was expecting. I plan to measure the dimensions on the bullets I was using later to see if anything is weird. All the of the loads shot very well with the 9.2 being the best.

The Underwood 180 gr Nosler JHP that quotes 1250 FPS produced the below results:
1182, 1212, 1196, 1171, 1192. I was really hoping these would hit 1250 but they shot great so I'm not worried about it.

[The_Shadow]

Thanks for your range report aOWENc.

[Graybeard]

Good stuff aOWENc. Looks like those coated bullets really sealed the bore well in that KKM barrel. A little quick math shows the lowest extreme spread in velocity with the 8.8gr load @ 18fps. The 9.0gr load @ 38fps and the 9.2gr load @ 66fps aren't bad, especially when considering the velocities they're achieving.

[sparkyv]

It shouldn't have been a surprise as sqlbullet mentioned this obturation phenomenon in a different thread.