I built a 7mm 338 Papua imp. I fireformed brass over 2 yrs hunting with 104 gns of wc872 175 gameking in lands. They shot great. Killing several deer. Now I'm loading up my first loads with formed brass and getting lots of pressure very sticky bolt. Can't hardly open. People that I read about was going up to 110 gn I started at 104 what I formed with even went down and still have pressure. So I backed off lands .025 and down 1gn n still pressure. Having to trash alot of brass cause the case won't go in shell holder. Please help.
stick bolt 7mm 338 lapua imp
- Thread starter joe30007
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Lefty7mmstw
Well-Known Member
You were probably able to hot rod it a bunch because of the bigger springback before the brass was formed. A grain isn't going to change your pressures diddly when you are at 100+ grains. I've been down this road with the 7rum ( 100 grains or so I 5010 with a 175)(also shooting 140's at 3500 fps) and it ended with a shot out barrel in short order. If you are over pressure, cut your charge 10% or 11 grains in this case, and that will net a 20% drop in pressure. Ball powders like wc 872 can be weird at full power loads in smaller bores and are often very erratic at full throttle.
I'd personally go with a 50bmg stick powder like rl50 or I 5010. They are a lot more stable when pushed a bit in smaller bores. I tried wc872 in my 7stw with 171 barnes, and it had a 150 fps x and I wasn't even at the top yet. Rl 50 and rl25 were dang near perfect with good accuracy. I couldn't try I 5010 because mine went bad a couple of years back. I'm thinking of getting more. I never had wc872 when I had the 7ultra, but aa 8700 wasn't good in it with heavy bullets.
Wc 872 does work in the 300 ultra with heavy bullets though( a bit more load on the powder).
Lefty7mmstw
Well-Known Member
Another thing you can do is get your bullet off the lands at least .1". You need some run at the rifling with something this overbore to quash pressure issues (pressure spiking) upon bullet engraving. With a 175 you aren't going to notice even .2" to.4" of travel if your barrel likes the bullet. I had .5" free bore with my 7mm ultra and it was a cloverleaf shooter at 100 yards. My longest kill with that one was 700 yards using a 140 sierra at 3500 fps.
