dok7mm
Well-Known Member
I finally got around to trying the 156 Berger in my .235" free bore 6.5 Sherman LA with Retumbo. This is my 2nd barrel (276 rds) on a SwitchLug build by Clayton @ West Texas Ordnance. Stiller Tac 300, Bartlein 3B, 5R 1: 8, 26" in Manners EH-1, and March F1, 3-24x52. Current barrel is about 50 fps faster than first barrel and shoots 140s @ 3175 with no pressure.
Using once fired 280 Norma brass, I expected there would be some variance in velocities, so I loaded 3 rounds of each charge weight to even things out and get my cases fully formed. Cases are annealed each firing. 156s have been sorted by BTO prior to coating with HBN and barrel was treated with HBN slurry. All rounds shot @ 100 yds with no wind hold, as the velocity and ES were my primary objective.
I started with lower charges than needed, just to get a second firing on 50 cases. I shot charge weights from 56.5 gr. (2,728 ) up to 62.5 (3,038 fps) cooling to ambient temperature between shots. I had zero pressure signs at my max load, so I'll see how far up I can go. I deprime on a separate press, so I'll check for loose primer pockets.
I just picked .010" jump for pressure testing for now. CBTO is
2.904" and COAL is 3.596" on my Sherman #2 reamer, .235 FB. Conditions varied thru the day, temperature ranged 81* to 94*, wind was 5-12 mph back and forth from 3:00 to 4:30. Til noon there was cloud cover, afternoon the sun was out w/heavy mirage. It is indicated in the verticle on the last 4 targets.
This was a fast barrel with HBN, so work up safely for your barrel.
Targets are below. Hope this helps if you can use the data. I'll post my
final results when I'm finished.
Sorry they are out of order.
Using once fired 280 Norma brass, I expected there would be some variance in velocities, so I loaded 3 rounds of each charge weight to even things out and get my cases fully formed. Cases are annealed each firing. 156s have been sorted by BTO prior to coating with HBN and barrel was treated with HBN slurry. All rounds shot @ 100 yds with no wind hold, as the velocity and ES were my primary objective.
I started with lower charges than needed, just to get a second firing on 50 cases. I shot charge weights from 56.5 gr. (2,728 ) up to 62.5 (3,038 fps) cooling to ambient temperature between shots. I had zero pressure signs at my max load, so I'll see how far up I can go. I deprime on a separate press, so I'll check for loose primer pockets.
I just picked .010" jump for pressure testing for now. CBTO is
2.904" and COAL is 3.596" on my Sherman #2 reamer, .235 FB. Conditions varied thru the day, temperature ranged 81* to 94*, wind was 5-12 mph back and forth from 3:00 to 4:30. Til noon there was cloud cover, afternoon the sun was out w/heavy mirage. It is indicated in the verticle on the last 4 targets.
This was a fast barrel with HBN, so work up safely for your barrel.
Targets are below. Hope this helps if you can use the data. I'll post my
final results when I'm finished.
Sorry they are out of order.
