As part of my 2017 reviews, I'm going to discuss the KynSHOT hydraulic recoil buffer RB5000. I was especially interested in this buffer for a few reasons. Most AR15 operators who build their rifles or purchase an off the shelf completed rifle don't pay much attention to this component. It is hidden in the buffer tube and not much thought is given into it since the standard buffer is a simple looking component, which typically is not tampered or modified. If you have a standard Carbine buffer you may wonder why you have that "spring twang" sound. It is directly related to the carbine buffer and spring in the buffer tube. If you are looking for a way to reduce “felt recoil” and want faster follow up shots, keep reading.

Let us discuss the standard AR15 Carbine buffer for this particular review. The standard off the shelf carbine buffer is an aluminum turned 3.25" tube with a plastic tip filled with three steel weights roughly about 3oz. There are heavier Carbine buffers H, H2 and H3, which climb up in weight with a combination of tungsten and steel weights. A buffer is a critical component to a functioning AR15. As the AR15 cycles once the trigger is pulled, the buffer is pushed back by the bolt carrier group as gas in a direct impingement system is applied to the BCG. The buffer and BCG is carrying that “energy”(momentum) towards the shooter which is the “felt recoil” the operator feels and hears. Once the spring has fully compressed it naturally decompresses (recoils) and pushes the buffer and BGC forward towards the muzzle loading the next round and closing the bolt for another shot. There are different components in an AR15 platform which can be tuned to allow for a smooth operating firearm like an adjustable gas block, gas port size, tube length and so on. Similarly different springs and buffers are used to make sure an AR15 can cycle properly and reliably using different types of ammo loads, so naturally AR15 are normally aggressively over-gassed.
There is some Physics involved which is critical to understanding how a Hydraulic buffer works. Let’s explore Momentum and Kinetic Energy. Momentum is equal to mass times velocity (p=mv). Kinetic energy is what the operator perceives as "felt recoil", it is calculated as (K = 1/2 mv^2). Momentum is a vector quantity which has direction in space. Kinetic Energy is a scalar quantity and has no particular direction. If you inspect the formulas, momentum is directly proportional to mass or velocity changes while Kinetic Energy is proportional to the square of the velocity. If you double the velocity you quadruple the kinetic energy. Add to all this is conservation of momentum and conservation of energy laws. What does all this is mean in relation to the hydraulic buffer already?

First we will examine the word "Recoil", which is used very loosely with different implications relative to firearms. You might hear an operator refer to the recoil as energy. This is actually not correct, since recoil is a vector which has direction like momentum, and energy is not a vector, using the terms synonymously can be confusing and incorrect. What operators perceive as recoil in true definition is actually Momentum. It is directly related to the mass of the firearm times the reverse velocity of the ammo leaving the barrel. The heavier the mass of the firearm, the less acceleration will manifest itself as "felt recoil". Simply put, if you shoot a 5.56 round of tank designed with an AR15 barrel, you will not feel any "recoil". This can be observed by looking at Newtons second law of conservation of momentum (F= dp/dt).

The momentum on an AR15 is from the bullet and gasses leaving the barrel. The mechanisms moving inside the AR15 such as the BCG, spring and standard buffer do no change the nature of momentum regardless of the weight changes of these components. Using a heavier buffer or lighter buffer does not change the momentum based on the laws of Physics. So changing to a heavier buffer like H2 or H3 does not change the perceived recoil in theory. What it does change though is the time interval in which the momentum is transferred to the operator. Given the mass of the buffer is changed, and we know (Force = mass x acceleration), we can deduce how perceived recoil does not change total momentum the operator absorbs, but how it is absorbed is important and what the operator refers to as “recoil”. If you just understood the last statement, you will understand what I'm going to explain next. Since the duration of felt recoil has changed in relation to time, the heavier buffer will take longer for the operator to feel a 'softer recoil' because of the reduced acceleration over time, vs a lighter buffer which will have a more ‘stinging recoil' affect over a shorter time delta. Again the momentum and Kinetic energy is not changed, but manipulated in a manner where the timing and acting forces are perceived by the operator to be different. Finally, this is where the hydraulic buffer comes into play.

We discussed above the different carbine buffer weights available. If you change from a lighter buffer to a heavier buffer, you are simply changing the time interval over which momentum is transferred to the end of the stock. With a hydraulic buffer, what happens is the Kinetic energy is actually being transferred to a different type of energy in the form of thermal energy. It is important to understand the principles of energy conservation and energy changing forms. When you rub your hands together, Kinetic energy is transferred to heat as a result of friction between your hands and the energy is lost in the form of heat. The same concept works for a hydraulic buffer. The ‘recoil’ and momentum is actually reduced by the transfer of energy to thermal loss. Similar to a how a shock operates on a car or motorcycle there is a piston, orifice holes, seals, chamber and fluid more or less in the KynSHOT buffer. While I don't have the design details for good reasons because the KynSHOT is patented and the details of the design are proprietary, it is a safe bet to assume it operates similar to a regular shock. I contacted John who is a Director at KYNTEC, he provided me with some specific information and details about the operation of this buffer. This buffer is a single acting device working on the compression stroke only, unlike a car or motorcycle shock.  
"As the recoil event begins, the bolt carrier group moves rearward and compresses the piston rod as the spent casing is ejected.  As this happens, hydraulic fluid is orificed and at this interface kinetic energy (energy of mass in motion) is converted to thermal energy and dissipated through the cylinder of the buffer.  This is exactly the advantage of the hydraulic buffer as it is compared to so many spring and tuned mass dampers on the market today.  Hydraulics is the only way to take energy away from the system.  Springs and tuned mass dampers just move energy around, store it in springs, and are not efficient.  Once the buffer and bcg hit the back end of the buffer tube, the buffer spring takes over and pushes everything forward, causing the bcg to pick up the next round from the magazine and chamber it.  This forward motion is also felt by the shooter.  The energy of the buffer in motion is dampened when the buffer comes to a stop at the front retainer detent and the piston rod strokes again, dissipating more energy."

As you can see, John has confirmed the Physics behind what this type of buffer offers compared to a standard buffer. Full circle back to the reasons I was interested in this buffer is the KynSHOT buffer reduces felt recoil which is very appealing. It reduces muzzle raise which is critical for 3-Gun shooters and range shooters practicing quick target acquisition and rapid successive follow up shots. The buffer also eliminate  the spring "twang" noise which is unpleasant, and significantly reduce wear and tear saving your AR15 as the moving parts are slowed down by the transfer of energy. The fact you can use this buffer to reduce ‘felt recoil” to a minimum, makes it an ideal product for introducing newcomers to the sport who might otherwise be concerned about recoil. I personally find anything which reduces the recoil or makes the firearm friendlier and easier to shoot as a welcome option in my toolbox. My wife who has shot my other AR15 rifles found this one to be her favorite and it does not surprise me.

The KynSHOT is made of high quality 17-4 stainless steel and the finish is really beautiful with a high gloss polish. The steel is designed to withstand corrosion and punishment of the elements. The hydraulic fluid used is proprietary, but John confirmed it is aircraft grade oil with good temperature stability and made to last. It is likely used within the Aerospace industry and variant of a Mil-Spec fluid. I inquired if there was any service needed to maintain the oil or seals. I was assured the buffer carries a 1 million cycle or 10 year guarantee. In addition, the buffer is not serviceable and requires zero maintenance. The buffer is not the lightest out there at 4.2oz, but the benefits of this buffer far outweigh the additional weight in this low weigh build. The buffer is manufactured right here in the USA. KynSHOT has a machine shop at their headquarters in Buffalo, NY where they produce most of the components, what they don't produce is produced by another manufacture close to their headquarters.

Installation of this buffer takes less than a few minutes, there is not much to it, take out the old buffer and just slide this in without any modification. First day at the range I went through about 500 rounds and I could tell after the first round after switching between the H2 buffer and this buffer recoil was reduced. All the rounds cycled perfectly, no malfunctions of any kind. I felt more in control standing and shooting, on target recovery was quick and I felt less fatigued. This buffer has been tested and proven by professional competitive shooters, military and law enforcement. With the guarantee offered and benefits this buffer provides there is no reason why every AR should not come with this device. I don't consider this a draw back because you get what you pay for, but the only deterrent for some people might be the price. Yes this is a premium product, but after hopefully understanding the physics and what benefits this buffer offers, it will be an easy choice for you to make. After my experience with this buffer, any future builds, I will be purchasing this buffer.

Youtube Video Link:
https://youtu.be/frPx3D-wMVI

I like using these but the weak point has always been blowing the seal out, puking the oil.
they are common in industry and are called "cushions"

you described the body but how well have they done the seal?
on my home made ones I use adjustable cushions.

I understand that concern, I can only go by what I was told. The seals are Aerospace grade so they should last what they advertise. They have a 1 million cycle or 10 year guarantee which says a lot about the quality of their seals which have been tested and proven.

Will it still function even if the seals blow and the fluid leaks?

I would suffice to say yes, only because the overall length of the buffer when compressed is almost equal to a standard buffer, but I would certainly not trust this to faith and would caution against using this if you run into any issues. The good part is they offer a 10 year 1million cycle warranty so i would hope as you replace your buffer spring as part of regular maintenance you check the buffer.

Cheers

Didn't someone already make this?

After reading your review and evaluating all other reviews & YouTube vids on this, I bought one. Came today. I've got one of my dream builds dialed in to run flawless with an ST-T2 buffer (4.0oz,) JP SS Melonite LMOS carrier, and an SLR gas block set @ 3 (12 is wide open.) This is running PMC Bronze 55gr 223 FMJ-BT. That's all I shoot these days.

It shoots like a dream to say the least.. but if I can make it better, then so be it.

I'll head back to the range again this week to give the Kynshot a whirl. I'll be sure and post up my results as well.

BTW - My RB5000 weighed in @ 4.18oz. And it IS a very well crafted little piece of engineering too! WooHoo!!

Rock on!
Jim

Well, I'm happy to report that I was able to keep my SLR gas block @ 3 clicks out from fully closed. Remember, 12 clicks out is wide open! I thought I might need to take it to 4 with the added weight & hydraulic resistance with the Kynshot (as apposed to the 4.0oz Spikes ST-T2 buffer.) But no, 3 it is! This gun runs clean as can be with 22WMR type impulse.

Ran 80 rounds of PMC Bronze 55gr down range today with the Kynshot. Flawless. Impulse is better (less) than it was before. Since I got this for $90 shipped from Botach I feel it was a justified purchase. Even though at that price it's expensive, it's built really well with top tier components. If it works malfunction free for as long as they say it will, done deal.

I'll need to give it more trigger time to really appreciate it, but today's venture immediately let me know this was going to be a good session. No mag dumps, but 3 shot groups @ 25 yards offhand were some of the best I've done yet. Using a 3 MOA Vortex Venom RD. Perfect!

I'll return to give further impressions as additional trigger time accumulates. But for now, I'm pleased as punch. Good job Kyntec! I'm impressed.

Happy shooting,
Jim

And just for the record, here's the build on this gun:

Upper Aero FDE
Rail Faxon 15" CF
Barrel Faxon 4150 16" Pencil
Barrel Nut V7 Ti
GB SLR .625 Clamp Adj Melonite
GT BAD SS Nitride Mid
Muzzle Comp 2A Ti
Blast Fwd ICD
Magpul MLOK AFG
Magpul MLOK MVG
Carrier JP LMOS SS Nitride
Bolt AXTS 9310 MP, Melonite
Cam Pin Hydra-Fire Roller
Firing Pin Ti
Dust Cover SI Poly
Charge Geissele Super
RD Vortex Venom 3 MOA
RD Riser UTG .75"
3 Slot Pic UTG

Lower Aero FDE
TG BCM FDE Mod 0
Trigger LaRue MBT-2S
Trigger Pins KNS Precision
Tube PWS Mod 2
Buffer Kynshot RB5000
Buffer Spring Tubb 300 Blackout Flatwire
Buffer Retain V7 Ti
EP/Castle V7 Ti
TD/Pivot V7 Ti
Selector V7 Hybrid Ambi
Mag Catch V7 Ti
Stock MFT BMS
Grip Mag K2
Bolt Catch SI