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Old 05-05-2007, 06:21 PM
scootertrash scootertrash is offline
Senior Member
Join Date: Nov 2006
Location: Lake George, Colorado
Posts: 257
Default Sticky reinforcement

I have read two different posts about the "magical" 3800 fps out of 20 VT's in the past two days, and even talk of room to spare.

I'd like to remind the newer members to read the sticky about rifle to rifle differences. Try as I might, I cannot safely reach that speed with my Cooper. Early on I tried H4198 and made it to around 18.5 gr before I got heavy bolt lift. 18.6 blew the primer out of the case.

I've since switched to N120 and have decreased that load twice because I was still getting bolt "click". I'm now using 17.2 gr and the speed is right at 3700. My H2O capacity is 22.6 grains, and using 18.7 grains of H4198 as an example, QL shows a pressure of 50K, and the parent Fireball cartridge is listed at 46K+. The velocity even at the 50K is still only calculated at 3716.

This isn't even considering the burn rate of the powders. The N120 I'm using now has a burn rate 9% faster than the original lot I had.

The spring and summer shooting seasons are upon us, and that means higher temps as well. Use a chrono, and watch for those pressure signs. They appear quickly in these small calibers.


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