Long stroke SureFire Carrier

[BufordTJustice]

I have publicly commented that this type of design mod would be beneficial....and here it is:


http://soldiersystems.net/2016/05/25/sofic-suppressed-optimized-bolt-carrier-group-long-stroke-from-surefire/

Longer stroke via shaving the rear gas key screw and a shortened buffer. THIS is an improvement. I'm excited to see what research SF reveals about their product development.

[Leaveammoforme]

I like the idea but, the first thing that jumped out at me is the one gas key screw.

I'm sure one screw that is of proper material and is installed correctly will be more than enough to secure the key. I also understand that the key will need shortened to gain the desired longer stroke.

All that but I'm still like "One screw key?!"

[cynical]

I'm not sure it's a single screw. From the pics it looks like the rear of the key (and the screw) is recessed into the carrier, not cut off completely.

[BufordTJustice]

I'm not sure it's a single screw. From the pics it looks like the rear of the key (and the screw) is recessed into the carrier, not cut off completely.

That's what I'm seeing. Either that or it's in a keyed-slot and installed from the rear (much like a front-to-rear sight dovetail).

[Leaveammoforme]

I'm not sure it's a single screw. From the pics it looks like the rear of the key (and the screw) is recessed into the carrier, not cut off completely.

That's what I'm seeing. Either that or it's in a keyed-slot and installed from the rear (much like a front-to-rear sight dovetail).

This sounds more right than what I thought I was looking at.

[the_1iviper]

spring loaded counterweight in the end of the carrier , interesting.

i wonder what they've done with the porting in the carrier

[bruin]

Functionally, what's the difference between a weighted carrier vs. a heavier buffer? Also, what is the purpose of the springs in the carrier? I'm definitely interested in this if Sullivan is behind it.

[tom12.7]

In terms of bounce, there is a big difference between a solid weight or mass than one that impacts at different times. A solid mass carrier with the total mass rebounding off the BE at one time is much different than a spaced in time mass impulse off the BE.
If we are restrained by a certain total mass, we can look at 3 easy scenarios. We could look at the total mass in a solid carrier. We could look into some of that mass placed into a delay via the action buffer. That buffer mass can be satisfactory, but sometimes it is not. A portion of that total mass may be placed inside the carrier with an offset in timing to reduce bounce further.
When the carrier hits home, a solid system tends to bounce. Using a portion of that mass in a buffer that is spaced to add a time delay can reduce that, but that impacts in its own time. An offset impact in time addition to the buffer that further disrupts the original bounce harmonic can dampen down those effects further.
The choices in possible masses are not random, neither is the timing of those.

[bruin]

Thanks for your reply; I'm still trying to wrap my head around it. Dealing with bolt bounce, different ways to skin a cat I guess. I seem to recall Sullivan not being satisfied with the carbine buffer construction to address the issue. Since suppressors increase the cyclic rate, bolt bounce would be more of an issue in full auto. Curious what's inside that shorter buffer and the total mass of the reciprocating elements.

Sent from my SM-T810 using Tapatalk

[P2000]

Interesting.
The way I see it, as the BCG in an AR moves rearward, there are 4 significant milestones. #1 the point where ejection occurs, #2 the point where failure to feed would happen if rearward movement stopped, #3 the point where failure to lock back would happen, and #4 the point where the reciprocating mass (BCG and buffer) hit the RE and stop, contributing to recoil.
This system gives more distance between #3 and #4, ensuring reliability while giving more time for the spring to slow down the reciprocating mass prior to #4. This should mean less recoil, I would guess. It probably shoots like a gun with the adjustable gas block turned down to the ragged edge while still being reliable.
I'm sure there is more to it but that seems pretty cool. It kind of reminds me of the ultimax 100 LMG, which is designed with a "constant recoil" where the reciprocating mass never hits the rear, it is always under spring power.