Hello.
I am new to 9mm Ar15 rifles. I am building an 9mm using a Hahn bottom load block, and an 16" barrel for now and maybe a shorty barrel for a pistol build later down the road. using a standard CAR buffer tube and spring.
My question is on the buffer, what weight do I need? does it depend on the weight of my bolt, barrel length, and ect?
I have built close to 50 - 75 rifles in my life but never an 9mm.

Thanks for any help. I am sure I will have more questions as time goes on. I have used the search function but it sucks now after the upgrade to the web site.

At a minimum - you need a 5.4 ounce 9mm buffer.  For YEARS 9mm 16" carbines used nothing more than a standard 5.4 ounce 9mm buffer and carbine action spring.

Standard 9mm buffer - $24
KAK 9mm for $12.50

Other popular options (sorted by price):

8 oz. - KAK extended buffer - $32
7.5 oz. - Kaw Valley KVP - $35
5.9 oz. - YHM 9mm extended buffer - $40
8 oz. - Spikes ST-9X buffer - $45
10.0 oz. - KAK extended heavy buffer - $50
8.5 oz. - Slash buffer - $75
5.5 oz. - Blitzkrieg AKTIVE buffer - $75
6.0 oz. - Blitzkrieg Hydraulic buffer - $120
JP Silent Spring 9mm Gen2 - $150

I have the JP and it is smooth, much smoother and softer recoil than a standard 9mm buffer.  It includes the spring so take that into consideration when comparing prices.

9mm blowbacks have a surprising amount of recoil.

I shot a bud's Hydraulic yesterday, and it was smoother than my JP.  He had a standard buffer in his before and it was brutal when suppressed.

It comes down to how soft you are trying to get the recoil, and how big is your budget.


Value?  The $35 Kaw Valley 7.5 ounce hands down.

Lowest recoil?  Hydraulic.  The downside to hydraulic is some people have had them fail.  My buddy has run them hard in a ton of weapons and never had an issue.  10 year warranty makes that pretty easy.

don't forget to figure the total weight of bolt + buffer... bolts differ by manufacturer... something around 22oz total will probably get you in the ball park...my 21.9 oz unit works well with a 148 power factor hand load...

Nice, informative post.

Thanks.

Picked up a KVP buffer as a result!

A lot of people also appear to have had luck using an a5 buffer in a standard carbine tube.  Eliminates need for a spacer.

I use a Blitzkreig hydraulic and it kicks ass.  Very soft recoil impulse and I have had zero malfunctions in my QC10.

We went through 330 rounds each yesterday, fighting each other on a dueling tree as fast as we could reload 10 mags.  

I was the only one with a malfunction, caught a stovepipe which mine does about every 250 rounds or so I'd guess.  His with a Blitzkrieg hydraulic was suppressed and ran like a top.

This, except I have a DDLES lower.

I have a very early DDLES Glock 9mm lower. Before that I had a 9mm with a mag block.

All of my experience has been with short barrelled 9mm ARs. That being said, I ran different variations of the same heavy buffer for years. Sometimes with a spacer, sometimes with quarters, sometimes with rubber washers added, etc.

I finally said screw it and ordered a Blitzkrieg Hydraulic buffer and spring set. I am so glad that I did. It totally changed the recoil impulse of the gun and made it so much softer shooting. I have another build I'm doing and I'll definitely be getting the hydraulic buffer for that one as well.

I just got the Blitzkreig buffer and got to smoke test it tonight. I also bought the JP spring they recommended for it. Very noticeable difference right away. No doubt recoil is dampened and the gun stayed flatter. I ran through a plate rack a few times with a standard buffer and the hydraulic buffer and am sold on it.

The best value is the Spikes 9mm buffer.
I have always had good luck using the Wolff extra power spring on 9mm guns.
Slashes buffers are nice but are over priced.

So I see the Blitzkreig mentioned here and googled it. I usually run 5.5 in barrels and thought I might try the hydraulic buffer but one thing I read was that the hydraulic buffer was optimized in a 14.5 or 16" barrel. I was just wondering if it has been used successfully in a 5.5" barrel.

Yes.  They sell two combo kits, one with a JP AR10 rifle spring for carbines, and one with a JP AR10 carbine spring for pistol/SBR length barrels.

http://www.ar15.com/forums/t_3_15/697832_Blitzkrieg_Components_9mm_hydraulic_buffer_review.html