I'd love a proper length 300BLK. Sadly, SIG doesn't make one. They offer an 8.9" 5.56 and a 12" 300BLK; optimal lengths are reversed.

I agree on the .300BLK barrel length being silly, on the 553. However, they utilize some sort of reflex silencer on it, which may provide an optimal setup; albeit one unavailable to us. I intend to make a shorty .300BLK on a US 556 receiver, eventually; I have had the chambered barrel blank and host receiver for a while, but have yet to get the ball really rolling with the gunsmith. I know some folks out there have cut down their SAN .300BLK 553 barrels, which is likely what I'd do, if I had one of those guns; I'm just not interested in that caliber enough to invest in that particular gun for it.

Yep. I think there might be a reason for the longer barrel as far as reliability goes. I'd be interested to know if those who've cut down to 8-9" find them to run as they should. Certainly would need a 4-pos regulator to fine-tune operation.

what SIG AG told me regarding the 300blk 553 was that they couldn't get it to run reliably with a barrel shorter than the 12" iirc.

Surely it's more a matter of dwell time, than barrel length. With a barrel that long, they could have gone with the 551 operating system, but didn't; no doubt due to the longer dwell time of the 553LB configuration. It's odd though, considering the efficiency of the 55X, that they'd have to do that. AR15s run into problems, when the muzzle gets too close to the gas port; the 553 and 551 are evidence that the Sigs aren't hindered to the same extent.

quote:

Originally posted by KSGM:
Surely it's more a matter of dwell time, than barrel length. With a barrel that long, they could have gone with the 551 operating system, but didn't; no doubt due to the longer dwell time of the 553LB configuration. It's odd though, considering the efficiency of the 55X, that they'd have to do that. AR15s run into problems, when the muzzle gets too close to the gas port; the 553 and 551 are evidence that the Sigs aren't hindered to the same extent.

yeah, if the 553 blk or 553r were shorter I'd prob opt for those. The krink/mp5 length on the 553SB is really convenient for me though. Diopters always look cooler too. I'll probably go for that when i can.

Vickers Guide just posted this pic. Seems a shorter barrel has been offered in 300BLK?

I believe that to be the reflex silencer I mentioned. The unfluted portion of the silencer body is likely where the muzzle threads are.

Also, I wish he'd hurry up and release that book.

August ship date I think