KAC SR-16 Pressure Reduction System

[PatrioticDisorder]

I had my SR-15 14.5 & 11.5 uppers out today for the first time with VLTOR A5 H3 buffer and Sprinco green buffer spring, shot both suppressed and unsuppressed (SOCOM RC on the 11.5 & SOCOM mini on 14.5, both wearing Surefire muzzle brake mounts). Both the 14.5 & 11.5 ran like sewing machines with federal 5.56 & .223 pressure 55gr suppressed, unsuppressed both ran 5.56 pressure federal no issues (bolt locked back after last round), however with .223 pressure the 14.5 would fully extract but not chamber a new round on every shot fired & the 11.5 would cycle the .223 fully but would not lock the bolt back after the last round fired (I loaded a mag with 3 rounds several times to test these combos, along with several fully loaded mags).

Considering I plan to shoot these two set ups suppressed 99% of the time, I'm very happy with this spring/buffer combo on these uppers. Recoil impulse on both rifles was very smooth & mild. I also did not run an LMT enuanced carrier (I asked about this earlier in the thread), I ran the standard KAC carrier, seemed like a total waste of money on this particular set up.

[tom12.7]

I had my SR-15 14.5 & 11.5 uppers out today for the first time with VLTOR A5 H3 buffer and Sprinco green buffer spring, shot both suppressed and unsuppressed (SOCOM RC on the 11.5 & SOCOM mini on 14.5, both wearing Surefire muzzle brake mounts). Both the 14.5 & 11.5 ran like sewing machines with federal 5.56 & .223 pressure 55gr suppressed, unsuppressed both ran 5.56 pressure federal no issues (bolt locked back after last round), however with .223 pressure the 14.5 would fully extract but not chamber a new round on every shot fired & the 11.5 would cycle the .223 fully but would not lock the bolt back after the last round fired (I loaded a mag with 3 rounds several times to test these combos, along with several fully loaded mags).

Considering I plan to shoot these two set ups suppressed 99% of the time, I'm very happy with this spring/buffer combo on these uppers. Recoil impulse on both rifles was very smooth & mild. I also did not run an LMT enuanced carrier (I asked about this earlier in the thread), I ran the standard KAC carrier, seemed like a total waste of money on this particular set up.

I'm curious as to why the LMT enhanced carrier was deemed "a total waste of money" when it wasn't even tested in your application?
The addition the enhanced carrier can widen the degree of function/operation with a properly weighted and sprung A5 in KAC SR-15's, 14.5" and 11.5" included.
The issues that normally come up with the A5/LMT enhanced carriers combo's are the ones that are gassed heavier, that you exceed the A5H4 in weight in testing, SR-15's are not those.

[PatrioticDisorder]

I'm curious as to why the LMT enhanced carrier was deemed "a total waste of money" when it wasn't even tested in your application?
The addition the enhanced carrier can widen the degree of function/operation with a properly weighted and sprung A5 in KAC SR-15's, 14.5" and 11.5" included.
The issues that normally come up with the A5/LMT enhanced carriers combo's are the ones that are gassed heavier, that you exceed the A5H4 in weight in testing, SR-15's are not those.

Pardon me Tom, I didn't mean the enhanced carrier is crap, way too many high volume shooters who appreciate it for me to completely right it off. What I mean't was I thought it woulda been too much to jump right to the enhanced carrier without even running it with the A5 buffer system. I still may buy a couple carriers and try it out, eventually.

[PatrioticDisorder]

Something else I didn't mention, I really wanted to run the Sprinco green spring, for durability/longevity if nothing else. I know you recommend the H2 & Colt rifle spring with the E-carrier. One of my goals in setting my rifkes up was to make them as maintenance free as possible.

[tom12.7]

There's nothing really wrong with the 17-7 Colt rifle spring, it would have the same change out interval as the chrome-silicon spring for the application (sometimes more), but could have some minor different attributes that do not effect the cyclic life as a general as a whole. I do run that spring in some setups, but to that point that is for finer tuning for preference in something specific. There is little to be gained in this regard without a longer spring with more active coils in a longer action system that has a reduction of the difference of L1 to L2 values specific to this.

[og556]

Wouldn't the enhanced carrier be better suited for a carbine with more dwell time ? The intermediate gas system of the SR15 16" and 14.5" may not play nice with the LMT enhanced carrier. I imagine with the right buffer and spring it could run though.

[tom12.7]

Wouldn't the enhanced carrier be better suited for a carbine with more dwell time ? The intermediate gas system of the SR15 16" and 14.5" may not play nice with the LMT enhanced carrier. I imagine with the right buffer and spring it could run though.

As far as proper operation, a carbine gassed, A5, LMT enhanced carrier combination would show improvements given a proper port size and the action is weighted and sprung accordingly. Same goes for most any 5.56 AR's, to reduce the differences between the 2 carriers would take some of the following, extended barrel AND gas system lengths, reduced case capacity, larger bore volume, etc. Basically to approach the point that the residual chamber pressures are close in the unlocking sequence of the bolt for both.

[PatrioticDisorder]

Tom, do you think switching to the enhanced carrier, Colt spring and H2 buffer would yield less port noise (SOCOM RC on 11.5 & SOCOM mini on 14.5) vs. The Sprinco green spring and H3 buffer (and standard carrier)? I'm pretty happy with the current DB level I'm just curious what your take is?

[BufordTJustice]

Tom, do you think switching to the enhanced carrier, Colt spring and H2 buffer would yield less port noise (SOCOM RC on 11.5 & SOCOM mini on 14.5) vs. The Sprinco green spring and H3 buffer (and standard carrier)? I'm pretty happy with the current DB level I'm just curious what your take is?

Going with a std colt spring and the H3 or H4 will give you less port noise, with the e-carrier. The heavier buffer plays a much bigger part in retarding extraction and unlocking than spring strength.

[tom12.7]

Tom, do you think switching to the enhanced carrier, Colt spring and H2 buffer would yield less port noise (SOCOM RC on 11.5 & SOCOM mini on 14.5) vs. The Sprinco green spring and H3 buffer (and standard carrier)? I'm pretty happy with the current DB level I'm just curious what your take is?

Using the A5H3 with the standard carrier for both barrel lengths can be beyond my limit for reliability without a can with full power 5.56 ammo. I will admit that I run that combo sometimes in warm weather in cleaned and lubed guns only because it's easy for me to do. There is no way I'd advise to do this with a serious use gun, stick with the A5H2 for that.
Adding the A5H3 with the enhanced carrier seems to work well together with no can, the added buffer weight is needed to keep the action speed in check. The delay in unlocking of the enhanced carrier/ A5H3 combo reduces the work required to fully cycle the action as the residual chamber pressure has been reduced over the standard carrier. If higher port pressure 5.56 ammo is used, the "green" spring can be used there.
When a can is used 100% of the time, a better solution for both lengths is to reduce the gas porting to use either the A5H2 or A5H3 with the enhanced carrier. The standard porting can use the A5H4, enhanced carrier, and "green" spring with most cans without issues, but the better solution is to reduce the porting.
I have not directly measured the differences in sound pressure at the port. I would tend to lean towards less sound pressure though, as fouling in the upper can be reduced quite a bit from the carbine action/ standard carrier combo to the A5/ enhanced carrier combo. If its delaying unlocking, and reducing fouling, that it's not unreasonable to be able to get a reduction in sound pressure at the port.