7 Feb 14
Sage comments on the 7.62×35 (300 Blk) from friends in a position to know:
From Alex Robinson, of Robinson Armament, makers of the famous XCR Rifle Series:
“We have been working on the 300 Blk for some time. We could have begun shipping copies months ago. However, our goal was to make one conversion kit, which would reliably function with this caliber, in both supersonic and subsonic versions, subsonic even without a suppressor! The 300 BLK has such little pressure (at least in the subsonic version) that it’s more like a pistol cartridge than a rifle cartridge. This makes it difficult to handle for piston-driven systems. However, we’ve done it, but we had to push the gas-block way back into the upper receiver in order to make it close enough to the chamber to have enough pressure to cycle with subsonic ammunition, even with no ‘can’ (suppressor). This meant a completely new gas block design that is buried in the receiver, but still adjustable from the outside. Availability is still several months out.”
From a friend and writer:
“There are still some issues with the 7.62×35. Feed-profile of the bullet and the barrel-ramp angles have yet to be perfected. Some rifles have demonstrated feeding problems. We may eventually discover that standard AR magazines need a different follower for reliable operation. My conclusion was that the 300 Blk is still a ‘work-in-progress.’”
“Copper/tungsten bullets don’t perform well (fragment after impact) when the core is compressed tungsten. Compressed tungsten-core bullets are thus not recommended for general use”
“Problem with the 6.8SPC was that brass was designed for the low-pressure 30 Rem. They had to come out with SAAMI Spec #2 for the chamber, and build a case with a stronger head, in order to get the caliber to work reliably. Even so, high-usage guns break bolts, extractors, and lugs.
How well 7.62×35 ARs hold up under heavy use is currently an open question. However, unlike the 5.56×45 and 6.8SPC, it is hard to ‘over-gas’ the 7.62×35!”
Warning from another writer:
“The 7.62×35 round can be made to “chamber’ in a 5.56×45 rifle. The 308 diameter bullet sometimes can get pushed back far enough into the case to permit ‘chambering.’
Result? Blown-up gun, and likely personal injury!!
The two calibers are easy to get mixed-up, even mixed-in, with each other. They must be kept separate, or disaster awaits!”