I didn't take any pictures or videos or make any scientific measurements.  My review is purely subjective.  I've owned and shot M16s of all shapes and sizes since 1999.  I am not former military or law enforcement.

Shrike:
Previously, I had tried the ARES supplied carbine length spring with an old AAC rate reducing buffer, and H2 and H3 buffers.  The AAC unit was the smoothest and most controllable of the three, but still, recoil could be considered 'violent' while at the same time occasionally failing to strip a fresh round from the link.  With the 12" barrel and the gas adjusted to the middle setting, I could get 2 round bursts, but it was impossible to keep 2 rounds on a steel B27 target at 200 yards with this combination.  I ran the gun this way for a couple of years and was never really all that happy.  I used my tried-and-true generic 5.56 ball ammo, which consists of LC brass, pulled and resized M193 projectiles, CCI #41, W844 26.0gr, LFCD in the cannelure.  I've run this generic load with a variety of machine guns and semi-auto rifles for nearly 20 years with great success.  It's not quite as hot as M193, but nearly so and it's always run every gun I've ever tried it in.  With an ACOG and accurate rifle, I can shoot about 6" groups at 200 yards.  So it's OK for accuracy but not near match accurate.  It's just ball ammo with pulled and resized bullets.

I swapped the carbine buffer tube to a rifle length tube and installed an Ace ARFX skeleton stock, with a cut-down MG34 spring and the Kynshot rifle hydraulic buffer.  What a difference the rifle length system makes with the Shrike.  Recoil is very manageable and pleasant.  ROF is noticeably slower, but still, I can only get 2 shot bursts at the minimum - no onesies.  BUT - several times I was able to keep both rounds of a 2 round burst on the steel B27 at 200 yards.  It was pretty easy really.  And again, it was so smooth and controllable.  Additionally, I had zero failures to strip the round from a link in 200 rounds.  So it seems to be a reliability enhancement also.

Notes:  My buddy has run an MG34 spring with a Colt LMG hydraulic buffer on his Shrike for many years.  The goal is to cut down the spring until you can reliably get the LRBHO to activate on a magazine.  He settled on about 29.5 coils on his spring.  I cut mine down to like 31 or 32 and tried it out and it worked fine so I left it.  Don't just cut your spring - try it out first and work your way down.

Conclusion:  If you don't like the way your Shrike shoots, go with a rifle length tube, cut down MG34 spring, and a hydraulic buffer.  You'll love it and think that you should have done it this way the whole time.  My bud with the Colt LMG hydraulic buffer thinks the Kynshot works about as well and it's much easier to get and cheaper too.



9mm blowback:
Years ago, I ran and MGI rate reducer and standard carbine spring with a 9mm blowback setup and the MGI made it pretty controllable.  I could get onesies out of my 5.5" barrel, which I thought was pretty good.  

A couple of years ago, I went with a shorter barrel (4.5" I believe), with a Glock-mag lower, and a UCIW stock, spring, and buffer.  At first, I didn't imagine that the UCIW buffer would work with 9mm, so I installed a Slash 308 carbine XH buffer, as it's pretty heavy, and shorter than a standard carbine buffer, so the stroke was fine in the short UCIW tube.  This setup was OK, but a bit violent compared with the full-length carbine tube and MGI buffer that I had used before.  Another buddy of mine was using the UCIW with its stock buffer and spring in his 9mm, not knowing that this was probably not a good idea.  But I shot his setup and it worked fine, so I went to that and sold the Slash 308XH.  This was before Slash offered his UCIW 9mm buffer.  So I ran with the UCIW stock, tube, buffer, and spring for a couple of years.  It wasn't spectacularly controllable, but was a lot of fun, and REALLY compact.  

In the meantime, my other buddy got the Slash 9mm buffer for the UCIW.  Our setups at this point were identical (upper, lower, and UCIW buffer tube) with the exception of buffer and spring.  We compared his and mine and his was more controllable, but not $150 better in both of our opinions.  

Fast forward to yesterday:  we ran my setup with full-length carbine buffer tube, regular carbine spring, and Kynshot 9mm buffer against his UCIW length tube with Slash 9mm UCIW buffer (and honestly I can't remember what spring he used - maybe one from Slash).  Normally, he can get twosies.  But yesterday was hot, and his ammo had been out in the car, and the best he could do was triples.  I got doubles no problem and mine seemed more controllable than his.  It wasn't like night and day difference, but incrementally better.  Then we installed the Springco blue spring that nokick recommended with my short barrel, and it was an incremental step better than the regular carbine spring.  We could easily get twosies (no onesies though) and could easily keep on target at 10-15 yards.  We're both going to sell our UCIW setups and he's going to get the Kynshot and blue spring.

Conclusion:  It's worth the investment.  Both guns are more controllable and softer shooting than before.  Reliability is enhanced on the Shrike.  I've never really had reliability problems from the 9mm.  Kynshot claims a life of 1M on their hydraulic buffers.  I'll be happy if I get 100k out of mine...

I will compare them side by side soon and report back.

The slash heavy buffer and spring made a big difference on my M16 especially on 11.5 uppers. I have no experience with a Shrike but I would recommend a slash to anybody who has an M16. Gun is a lot smoother and it slowed it down some but not enough where it is choppy.

My gun sped up when I added a surefire suppressor. The slash also helped keep the gun controllable with the suppressor on which is now 100% of the time.

The Slash heavy buffer is not particularly different from various other heavy and rate reducing buffers, like the old-style AAC or MGI.  Slash makes a great product, and offers so many variations that he fills every niche.  But his buffers are nothing more (or less) than heavy buffers.

I should be getting my upper back to test (soon).  I currently have a Spikes Buffer with a red Sprinco.  I bought the KynShot 9mm buffer and I had a blue Sprinco in the parts drawer.  

I repeat.  I haven't had a chance to test.  I wonder if I got a Chinese knock off.  I bought it from NoKick and I wrote to KynShot to be sure.   The quality certainly looks and feels good.  However they misspelled patented ("patened").   I'm not a grammar or spelling stickler.   It's just one of those clues that it may be a knock off.   That's all.  

If it's real (I suspect it is) I'm looking forward to trying it out.   The main issue for me with be timing of a LL, not necessarily the buffer.

As promised, I finally compared the 9mm Kyn-shot buffer with blue spring to the MGI rate reducer with blue spring.  Both had very similar rates of fire.  I got a single once in each mag with each buffer, but doubles were the norm.  Both the Kyn-shot and MGI have plungers, and at the end of the recoil stroke you can feel the plunger depress - it's mushy at the very end of travel.  Both seemed equally controllable.  The only difference that I perceived, and it was minor, was that the MGI seemed like there was more reciprocating mass.  

The MGI weighs 7.1 oz and the Kyn-shot weighs 6 oz.  You can feel the difference when shooting.

I make no judgement as to which is superior.  Truly they are very similar in feel and individual shooters might find a preference for one over the other or might have no preference at all.  

The MGI is priced considerably higher.

The Kyn-shot is supposed to be warranted for 1M strokes, which seems pretty good as I've had several old-school hydraulic buffers leak after limited use.