bstomper
Well-Known Member
Long story short, this fall I did load development for my 7rm found a good accurate load of 68.4gns h1000, 175gn ABLR, federal 215m primers and Federal brass with speeds of 2891 fps at -7 Celsius out of my win m70 stainless. Went out today to get some colder temp speeds for my ballistics app. Put the gun and the bullets outside for several hours to acclimatize to the -26 Celsius temps before shooting and got average speeds of 2923. No pressure signs. Not what I was expecting. Why would my velocity go up in the colder temps.
took the 6.5 creedmoor out as well to once fire the rest of my new hornady brass before I start load development and to finish breaking in the barrel. They were all 41 gns of h4350. Last time I was out at -12 Celsius i dhot 40 rounds at 38 gns and loaded the rest in .2 grain increments all the way up to 43 grains with out any pressure signs. So that's why I had the ones today, -26 Celsius, at 41 for once firing the rest of the new brass. Should be safe since I had seen no pressure signs at 43 gns in warmer weather. Got 15 shot in and the last couple I thought I felt sticky bolt. Shot one more and had definite sign of pressure with sticky bolt and ejector mark. Again, not what I was expecting.
Seems the cold is giving me more pressure. Doesn't make sense to me. Why is this.
took the 6.5 creedmoor out as well to once fire the rest of my new hornady brass before I start load development and to finish breaking in the barrel. They were all 41 gns of h4350. Last time I was out at -12 Celsius i dhot 40 rounds at 38 gns and loaded the rest in .2 grain increments all the way up to 43 grains with out any pressure signs. So that's why I had the ones today, -26 Celsius, at 41 for once firing the rest of the new brass. Should be safe since I had seen no pressure signs at 43 gns in warmer weather. Got 15 shot in and the last couple I thought I felt sticky bolt. Shot one more and had definite sign of pressure with sticky bolt and ejector mark. Again, not what I was expecting.
Seems the cold is giving me more pressure. Doesn't make sense to me. Why is this.