Here is some load data for Rim Rock 220 grain hardcast bullets shot out of a KKM 6" barrel. Hopefully it will give folks a ballpark idea for loading this bullet, since there isn't any published data on it. Please consider all data as a reference point to consider, not a recipe to follow.
The usual disclaimer: none of these loads blew up my gun, but that doesn't mean they won't blow up your gun. In no way do I state or imply that these are safe loads. In each powder I tested, the higher end loads showed pressure signs such as flattened or melted primers, and occasional gas cutting around the primer. I'm a careful reloader, but nobody was double-checking the loads, and I make no guarantee that errors did not occur in the loading or recording of data.
Also, a minimum amount of the scientific method was used in recording the chronograph numbers. I didn't measure how far the chronograph was from the muzzle, and where I list two sets of numbers for Blue Dot powder, it's the same batch of ammo shot on a different day, with surprisingly different results. My guess is the chronograph is closer to the muzzle on the second batch, though it couldn't be more than five feet difference. Temperatures on the second day were considerably COOLER than on the first day...maybe twenty degrees.
I used a variety of brass, and I don't know if the instances of gas cutting is due to overpressure, or worn out brass, or both.
All loads were individually weighed, so any variance in powder charge is limited to the error inherent in a digital scale.
So with that...
220 grain Rim Rock hardcast load data.
All loads with WLP primers, chronograph app 13 feet from muzzle. 4,700 feet MSL
1.26" COL, assorted recycled brass, minimal taper crimp.
Glock 20 Gen 4 with 6" KKM barrel.
HS-6 POWDER:
7 Grains HS-6 Powder:
1043, 1018, 1032, 1048, 1034 fps
7.2 Grains HS-6 Powder:
1066, 1070, 1031, 1054, 1060
All HS-6 loads showed signs of overpressure, including some powder cutting around primer, and the rest of the loads were pulled. Fired brass was discarded.
LONGSHOT POWDER:
4 Grains Longshot Powder:
737, 727, 709, 741, 700 = average 722
4.5 Grains Longshot Powder:
790, 796, 771, 797 = average 788
5 Grains Longshot Powder:
842, 881, 876, 880, 869, 900, 915, 866, 847 = average 875
All loads of 5 grains and below required the factory Glock gen 4 spring and would not function reliably with the 22b LW spring. While the 4.5 grain load was a real pansy compared to normal 10mm loads, it surpasses the base of the Major Power Factor by a comfortable margin. The 5 grain load was a real pleasure to shoot at a recent Steel Challenge, and recovery was much faster than with loads making over 1000 fps.
5.4 Grains Longshot:
927, 937, 922, 937, 934
5.6 Grans Longshot:
931, 942, 951, 948, 940
6 Grains Longshot:
1010, 998, 955, 983, 998
6.4 Grains Longshot:
1022, 1066, 1071, 1069, 1024
7.2 Grains Longshot:
1081, 1082, 1077, 1081, 1082
BLUE DOT POWDER:
7 Grains BlueDot:
995, 989, 987, 986, 974
2nd time: 1001, 976, 1018, 1012, 1004
7.2 Grains BlueDot:
981, 982, 1011, 978, 992
2nd time: 1037, 1024, 1031
7.4 Grains BlueDot:
1017, 989, 1022, 999, 992
2nd time: 1060, 1050, 1039, 1038, 1045
7.6 grains BlueDot:
1004, 1015, 1011, 1050, 1022
2nd time: 1031, 1038, 1021, 1049, 1034
8 Grains BlueDot
1037, 1052, 1054, 1054, 1017, 1042
2nd time: 1080, 1064, 1071, 1071
8.5 Grains BlueDot:
1098, 1092, 1083, 1077, 1102
Too hot...flat primers and gas cutting on 1 load.
800X POWDER:
7.6 Grains 800X:
1128, 1142, 1137, 1152, 1157 = average 1143
7.8 Grains 800X:
1167, 1177, 1148, 1158, 1185 = average 1167
Primers starting to flatten out.
8.0 Grains 800X:
1141, 1151, 1137, 1158, 1162, 1145, 1186, 1178, 1151, 1152 = average 1154
Yes...I got lower velocity with 8 grains of 800X than with 7.8 grains, shot on the same day. Perhaps I juxtaposed the loads, but I don't believe I did. I shot ten of the 8.0 grain loads because I was confused by the numbers I was getting.
None of these loads really get close to what Underwood is getting from the 220 grain bullet (1225 from my KKM barrel), and the loads that come the closest all show signs of overpressure, and as a result the brass is discarded. I've come to the conclusion that reloading makes great sense for mild to medium loads (1100 fps as a high end, and then only with select powders), and if I want to go Hiroshima on something, I'll pay $20 for a box of Underwood ammo.
If anyone has load date for AA9 and 220 grain bullets I'd love to see it.
I think that a 220 grain bullet going about 1,000 fps is a very good practice load. Close enough to the 1225 fps Underwood load to mimic the recoil, but not so hot as to wear out the gun or brass, or shooter.
220 grain bullets going at about 800 fps are great competition loads, easily making major power factor, and nocking over pepper poppers and other reactive targets with ease.
Thanks for your great report Muskrat!
In my test of the UW 220 HC WFN with IMR800X 8.4 grains showed Velocity: 1209 fps from my S&W1006 5" with Case expansion measurement's: Diameter 0.4285" primer moderately flat.
UW 220 HC WFN with LongShot 8.4 grains was 1237 fps. They are up there and firearms need to be up for that task...
Nice job Muskrat, have been wanting to work up some 220"s myself, this will help a lot, thank you!
Worked up a few more loads for the 220 grain Rim Rock bullet. Again, this is from a 6" KKM barrel. See the disclaimer in the first post...I'm not responsible if your gun blows up!
6.0 Grains Blue Dot:
881, 907, 910, 865,858, 884, 908, 885, 880, 882 = average 887
Good accuracy
6.5 Grains Blue Dot:
986,. 962, 972, 950, 942, 987 = 962
Good accuracy, less recoil than 7 grain loads by a significant factor, though similar velocity.
AA9 POWDER
8.0 Grains AA9:
874, 851, 860, 878, 878, 886 = 871 average
Good accuracy; needs factory spring as FTE with a LW 22lb spring.
8.5 Grains AA9:
912, 918, 899, 919, 903, 910 = 910 average
good accuracy
8.8 Grains AA9
972, 954, 951, 962, 953 = 958 average
good accuracy
AA9 produces less smoke and muzzle blast than Blue Dot with similar velocity. Seems to be more consistent in the lower HP loadings as well. I'll run up some 9 and 9.5 grain loads and see where I end up.
Again, I'm not interested in pushing this load to the limit...not even close. A 1000~1100 fps load in 220 grain is all I want to shoot with any regularity, and the sub-1000fps loads are a LOT more fun to shoot at competitions.
I did a 800x workup with 220gr Ackerman powder coated slugs with results similar to yours. In a 6.6" alphawolf barrel with a large compensator. Starline brass, CCI 350s, 1.270" COL
8.0gr 800x 5 shot avg: 1168fps/666lbs, .425 case head
8.5gr 800x 5 shot avg: 1226fps/734lbs, .425 case head
9.0gr 800x 5 shot avg: 1299fps/824lbs, .426 case head
9.5gr 800x 5 shot avg: 1351fps/891lbs, .427 case head
The compensator made a world of difference at the higher levels. The 9.0gr load was the sweet spot for power vs case heads and would be this guns happy maximum.
800-X does seem to be the powder for 220's. Pity it's so miserable to work with. I've got an electronic powder trickler that's really designed for rifle loads, but I'll try it and see how it does with 800-X. I can't even pull the handle on my powder measure with 800-X, so I end up hand-weighing every load. Fine for max loads, but I don't want to do that for practice loads.
Have some 230 hard cast gas checked I need to start with 7.5 of 800x and work up. Going to use for deer in IN this fall