Can I use the standard carbine buffer & spring for my 9mm build?  Also, are there any problems other than gas in the face for suppressed fire if I use a regular port door?

I've heard that you can stack a couple of quarters at the bottom of the buffer tube to provide more compression for the spring and buffer.

I experimented with buffer weights and spring power.  In my AR9 franken build, it only changed the ejection pattern.  I currently use a 5.4oz with the wolf spring.  Also I use the quaters method as well either 1.75 or 2.50 in change.

I have carbine springs and H2 buffers in both my 9MM guns.

The reason for the spacer isn't to alter the spring compression rate/force - it's to limit rearward bolt travel.  If you don't have something limit rearward bolt travel the bolt goes too far back (not an issue till you get to that last round in the magazine) and the extra distance allows the spring to give extra speed/force to the bolt as it moves forward and it beats the snot out of the bolt stop.  Sometimes people end up with broken bolt stops/bolt catch (what ever you want to call it).  Limiting the rearward travel reduces that forward speed/force of the bolt and helps your bolt stop "live".

I have some washers in the back of one and a hard polymer bumper/washer in the back of the other.

Thanks for clarifying that.  I learn something new each time I ask a question here.  I am definitely going to put a buffer of quarters or better yet a collection of hard rubber washers to limit the bolt travel.  I am not excited about having to remove the bolt catch to install the mag block and don't want to replace it on a regular basis.
Thank You

My PSA lower came with a carbine spring and their heavy 9mm buffer.

It worked fine but I swapped the buffer for a long one from Mas Defense to protect my bolt stop lever as mentioned above.

A lot of guys run a regular buffer with no spacers and nothing breaks but I’m just paranoid.

I don't remember what kind of mag. well insert I bought (I really should document my builds better) but I can remove/install the block without removing the bolt catch/stop.   I don't have any intention of buying/building a .223 upper for that lower (two switch back and forth) but the lower has all standard AR parts in it - except for the mag. well insert and the rubber bumper under the spring in the buffer tube.

I am running a Blitzkrieg Hyd Buffer & JP AR-10 Spring.  Works great and reduces the hit when the bolt bottoms out on the backstroke.  It also reduces the bolt travel.

Anyone try VLTOR's A5 Buffer?

https://forums.brianenos.com/topic/236779-vltor-a5-h4-heavy-buffer-for-ar159-pcc/

In my 20 years experience with AR9 I've gone from 5.5 oz buffer, to 5.5 oz + quarters, to Spike's ST-9x  7.7 oz , to currently Vltor A5 h4.

I hear the moving weights in the Vltor gives the added benefits of a dead blow effect, but I can't tell much of a difference between the Vltor and the Spike. But I've only been to the range twice with the Vltor.

Vltor unintentionally created the perfect 9mm buffer.

What I can say is the heavier extended buffer feels much smoother then the 5.5oz buffer.

Would someone please post a picture of the rubber washers they have behind the buffer tube spring?

Is there a reason you ditched the Spikes 7.7oz?

I’m running an A5 length buffer tube, A5H4 buffer, standard rifle spring and a tube spacer in my DDLES lower.
Runs well,.....seems smoother

I’ve run heavier buffers but, to me, they seemed to slam the bolt forward, dipping the muzzle. The 6.08oz buffer, along with the extended travel just works, for me.

Everyone has their opinions and perceives recoil impulses differently.

I believe the 'standard' bolt/buffer weight is around 21 ounces.  Some like to run more and some less.  I think the lowest I've seen is around 16 ounces (16 ounce bolt minus weight and carbine buffer) and the most is close to double that (17 ounce bolt and 12 ounce buffer).  From what I've seen, for suppressed, you may want to go with ~25 ounces (16 ounce bolt and 9 ounce buffer).  Standard carbine spring is more than adequate.  If you can get away with a reduced power spring, that should help lessen sight movement on bolt closure.  If you opt for a heavier/.308 spring, you may find more sight movement on bolt closure.  Simple physics.

Some say it helps, but then again, some call it a case deflector and some call it a gas deflector?  In the Colt 9mm SMG operators manual it is called out and described as "Deflector (6a): Deflects cartridges clear of left handed shooters" pg 6/7 https://s3.us-east-2.amazonaws.com/media.connecteddatasolutions.com/downloads/m16a2+carbine%2C++commando%2C+9mm+smg+%26+m4+carbine.pdf

I believe some here have referred to the quarter spacer as "ghetto".  It's cheap and easily adjustable though, so if you go with it, just don't tell anybody.  Otherwise, there are other options that do the same thing for more money or you can make something on your own.

I've got a new, H6 and spring I'll trade to you for your experimental needs.  IM if interested.

The H6 weighs 5.15 ounces; -- same as a standard rifle buffer. H3 is 5.40 ounces, H2 is 4.60 ounces.

For several years now...I may have been the first one on the forum to discuss it and there are a few posts/full threads you can dig up from me if you search.

It works well.

You’re the reason I tried it......works DAMN well.

+1 on the 9mm Blitzkrieg/Kynshot buffer.  
That buffer is the same length compressed as an A5 buffer.

I'm using a 556 Tubb flat wire spring + A5 tube w/ the CMMG Guard radially delayed system.

Also in full auto.  I have tested a myriad of buffers/springs including the A5.

I am also using a spring loaded tungsten weight in the carrier instead of static weight.  Something I came up with pictured below.
This further delays the blowback and being that it isn't pinned to the carrier, has less effect on the rearward stroke so less tendency to influence the carrier on that rearward stroke (I also believe that the little mass of the tungsten buffer may also be absorbed by the hydraulic buffer as well)
...basically I only want to weight to do something on the initial recoil impulse and to help drive the carrier into battery.  I find that going with too much weight makes the gun too bouncy.



Details of this are all here: http://c3junkie.com/?page_id=538
Thread on all this testing here: https://www.ar15.com/forums/Armory/Full-Auto-CMMG-Guard-Tuning/23-494385/

This configuration is also a dream to shoot on my 556 uppers as well so I just do a straight upper swap when going to 556 w/ no changes in my lower.  No magblock to deal with either since using the new Endomags (pictured above as well).

I'm running a Kaw Valley Precision 7.7 oz extended buffer and standard carbine recoil spring.
I started off with standard buffer assembly and quarters and it worked fine,
but I didn't like the idea of extra spring compression from the use of a "spacer".
The Kaw Valley Precision buffer assembly seems to run a bit smoother
than the spacer set up, could be the fact that it is heavier.

I have a ST2 Buffer with Carbine spring, dot movement is less than with a solid 9mm buffer I don't recall the weight of. Used a thread adapter I had laying around as a spacer. The pile of quarters seemed like a lot of weight to be adding, like my carbines light

No reason at all. I just happened to come across a Vltor A5 h4 one day on the EE for cheap and decided to give it a try. I haven't had enough time on it to conclude if its any better than the Spike. They kind of feel the same to me.

Been tempted to try the Blitzkrieg hydraulic buffer.

Nice, people like me appreciate guys like you with the "I wonder how that works" attitude.  Thank you for the data.

I tried a Blitzkrieg, didn’t feel much different than a Colt 9mm buffer.
Sold it and I’m currently running a BCM A5 tube, A5H4 buffer, Sprinco green & a poly buffer tube spacer