Shot some imi 77 razor. Rumor that imi iz hot and ease of slr block adjustment led me to start 2 clicks short and open to lock back. Rifle function required same 5 click setting as for blammo, but I got ejector swipes and even extractor mark on base (but not inside rim). Wudda thought if that high pressure, rifle wudda functioned with gb closed off some. Comments?
Oh, yeah: 16in middie w blue sprang and h2 buff
IMI Razor core 77 grain is loaded hot, it’s their version of Mk262. IMI loaded Independence M193 is even hotter, with swipes and popped primers being common.
Don’t know what to tell you about the gas block setting.
Yeah, was on sale $135/240 delivered in a metal can. Grouped ok, maybe min and a quarter for 15 rds @ 100yds. Again, my simple mind is having trouble coming to grips with the fact it shoots so hard, but still needs same gas setting of calmer ammo. Guess those detents on gb aren’t so miniscule in their adjustment…
Try a heavier weight buffer ( re-adjust GB ) and maybe a stiffer spring… the bolt needs to stay locked closed , slightly longer (by a few milliseconds )
Just long enough to allow chamber pressures to be lower prior to extraction.
I saw the same thing in my .308 AR… heavier buffer and stiffer recoil spring solved it.
Even a .308 Tubbs Flatwire would work… heavier closed weight, normal bolt back weight.
Here are some spring weight measurements from David Tubbs… just food for thought.
A2 (old) - 7.6lb closed, 14.5lb open
A2 (new) - 9.1lb closed, 16.7lb open
Tubb Flatwire - 10.5lb closed, 16.3lb open
Tubb .308 Flatwire - 13lb closed, 16.7lb open
SpringCo White ? (standard) - 8.3lb closed, 16.3lb open
SpringCo Red (extra) - 10.5lb closed, 18.4lb open
SpringCo Orange (increased) - 13.9lb closed, 24.8lb open
IMHO, an extra power spring isn’t needed , nor wanted.
I tried both the “Red” and “Orange” … both caused needless muzzle dip, and were slamming the BCG really hard into the breach face
High peak pressures do not necessarily correspond to high port pressures.
Running a faster powder can produce this.
I do have an h3 from previous wanderings, but doubt I 'll worry for just a couple hundred rounds. Just thought it odd.
Dadgummit Clint. You’ve reopened my can of worms! Been wonderin bout slo powders (cfe223, varg, etc) and it burning in tube and action. Now I gotta worry bout faster powders (322) too?
Gonna have to just get off the pot and try something for my 62 horn hpbt and 69 smks. God help me when I have money for 77’s. Oh, maybe I should just quit overthinking it and jerk the trigger?..