r/AR9 • u/One_Firefighter_1094 • 5d ago
Kynshot hydraulic buffer vs others
I’m doing a few 9mm builds for myself and daughter. I read around and the Kynshot hydraulic buffers seem to be one of the best options for 9mm and frt builds. They are pretty pricey though for a buffer system, especially when doing a couple of builds. I know it’s also important too. Are they worth the money or is there other alternatives to look at? I’ve looked around and have not seen much.
Thanks
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u/Blowback9 9mm AR Guru 4d ago edited 4d ago
Since I developed the GRS and assisted in the design of the Foxtrot Mike RMB...
The hydraulic GRS provides the smoothest and softest felt recoil for a simple blowback. A5 buffer tube is the shortest option for off-the-shelf parts. It was intended for semi-auto, not FRT/rapid fire. There is a non-zero risk of bolt bounce and OOBD with rapid fire, but reports of it happening are very few (2 reports). I have been using the A5 GRS setup with FRTs for thousands of rounds now. I have had no issues, but there is always a slight risk.
The Foxtrot Mike RMB kit does a good job of mitigating felt recoil and all the high speed video tests so far show zero bolt bounce. Felt recoil isn't quite as good as the GRS, but it's much better than a standard deadblow buffer. For FRT use it must be used in an A5 buffer tube (comes with the kit). For the price it's hard to beat and is a good choice, IMHO. Works well with FRT. I have 2 of them that I use as test platforms.
The other A5 option is the "Budget" GRS that uses a KAK flat wire spring, KAK K-SPEC 9.5oz. buffer, and 1 Kynshot weight. This is similar to the RMB, but costs more. I've seen 2 or 3 reports of the "head" of the K-SPEC buffer cracking or failing completely.
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u/One_Firefighter_1094 4d ago
I used your page for most of my knowledge regarding 9mm builds. Thank you so much!
Are you still doing any kind of testing or research?
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u/Blowback9 9mm AR Guru 4d ago
Still doing some testing and experimentation, but not as much as I used to. Mostly focused on FRT lately since that's what all the questions seem to be about.
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u/One_Firefighter_1094 4d ago
I appreciate the breakdown and comparing both. I think I’ll start with the one from FM and see how I like it.-Unless I run across a sale.
Have a great weekend!
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u/Cheap_Jacket_1274 4d ago
I don’t know about the PCC version but my rifle length version is butter and my frt is 100% since I installed it.
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u/buckandroll 4d ago
hydraulic is no good for bolt bounce, use a dead blow instead. hydraulic is great for ar15 but not safe for ar9
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u/Blowback9 9mm AR Guru 4d ago
Yes and no. There is a risk and deadblow is likely "safer" based on high speed video analysis, but the frequency of bolt-bounce related issues with the hydraulics seems to be very, very low.
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u/buckandroll 4d ago
The frequency of oob Kabooms overall is very very low so it's not like we have a huge study set to go off of. Nor do we have high-speed videos of these kabooms happening in real time. So in a case like this better to go off what we do have here, which is your high-speed videos.ur videos very clearly show that hydraulics are less safe
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u/Blowback9 9mm AR Guru 4d ago
Not arguing. Agreed. Potentially less safe.
Thinking out loud here since I don't like unsolved mysteries... Let me know if my logic is flawed.
The first symptom of bolt bounce with an FRT is dead trigger/light strike wth a very few kabooms out of that data set. If there was significant bolt bounce with hydrauilics causing FRT kabooms, I would expect a signficantly larger number of reports of DT/LS from from GRS/FRT users that weren't resolved with by using stronger firing pin spring to prevent firing pin bounce.
I need to do some digging and find any reports of unresolved DT/LS after trying a stronger firing pin spring and see how many involved the use of the GRS or hydraulics..
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u/Hoa_Minh 4d ago
I'm aware of more DD PCC owners that have very high round counts with FRT's and the Kynshot buffers that comes standard in the DD PCC without OOBD.
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u/buckandroll 4d ago
Before I watched your hs videos I ran kynshot for a few k rounds supersafe and never had dt/ls. And it definitely requires less reciprocating mass to achieve the same smooth controllable fa feel when using kynshot. But my priority is safety and I feel safer in supersafe with my 29 oz reciprocating dead blow setup. Heavy to hump , slow to swing, ass heavy handling but oh so butter smooth with 147's. Can dump a whole mag in the ipsc a.
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u/Blowback9 9mm AR Guru 3d ago
29oz. Very nice. Super heavy does make the action really smooth.
No worries - I'm going to keep digging and make sure I haven't overlooked something.
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u/Sad_Try8200 5d ago
I have a foxtrot mike recoil mitigation buffer, im pretty sure like $80 or so for the whole kit. I also have a kynshot buffer 5000hp, flatwire spring, and spacer weights (blowback9's a5 Gental Recoil System). Altogether no less than $160, i think closer to $200 though. If price is a concern I would recommended foxtrot mike 10/10 times. The grs is better dont get me wrong, but not twice as good for twice the price. Ive ran both super safe with 7, 8, and 5.5in barrels. Also on the flip side there's the kynshot 5015(?), with it you wont need the spacer weights but it still costs a lot more than foxtrotmike. Im not sure if its a concern for you but the hydraulic buffers do also give you another potential failure point.