No schitt. Loading 2grs less of Benchmark, Under 60 degrees all is good, about 3650. Excellent accuracy (.21 for 5 shots @ 100). After that started getting erratic velocitys, and pressure spikes. At 75 degrees was getting 4026 average, stiff bolt, and flattening primers. Had ES of 162 fps.
So yep, I thinks yours is a bit HOT.
BYE BYE barrell. Been there done that.
Swifty
Dunno.
This load is a book max charge from the Lyman manual. Barrel life may be compromised. I, obviously, can't say how much. I will tell you that velocity dwarfs your Benchmark number, primers are slightly flattened but not cratered and pockets stay nice and tight. Velocity spreads are well within acceptable parameters (ES in the 40's) and accuracy is superb to freakish for a box-stock factory gun.
I guess if I wanted to run .22-.250 numbers I'd have bought a .22-.250
Don't know what else to say.
Better buy a new book, 50 to 52 gr IMR 3031 35 to 36 grs By Sierras Newest book, Speer # 14 52 gr, 36 grs IMR 3031, IMR Manual 2010 50 to 52gr 36.5 grs. IMR 2007 Manual Max 36.5 IMR 3031 velocity with a 50 is between 3800 and 3900. Had to go back to a 20 year old hodgdon manual to find 37.5 grains IMR 3031, but the max velocity was only 3750, Wonder if they are making better powders these days?
43.5 grs H380 Which is max, and adding a magnum primer gave me 4075 average with a 52 gr, which did burn out a barrell. Took 800 rds at this velocity to toast 2 inches of barrell total number down the tube was 1450. Mines a box stock Cooper Model 22 MV.
If I want freakish velocity, I can load up 46.5 grs AA 2700 CCI BR primer and 40 gr SBK for 4450 fps and awesome accuracy, If I wanna go higher I can max out that load by adding 1gr and probably break 4500 fps. But all of these loads are within published book in the last 5 years.
An aside to this, Benchmark is #80 on the burn rate chart, IMR 3031 is 78 they are so close it really doesnt matter.
Going back 20 years and still not coming up with 38 grs, its an overload by todays standard, and as I said before BYE BYE barrell, I have been there and done that.
Swifty