I'm buying the sbm4 brace and buffer tube but don't know what buffer and spring to buy. The last ar pistol I had sported the shockwave and it came with everything needed in one kit.

Thanks!

Probably doesn't matter unless the stock requires something special.

Have a KAK buffer tube on a 10.3" with a Ballistic Advantage barrel and it has run the standard KAK carbine buffer, standard H2, and a Spikes ST-T2 without issue on a KAK and mil spec spring.

Also had a Geissele Super 42 in it for a while too, flawless.

Got ya. Reason I asked was because the ar pistol I had would constantly have ftf/fte and I didn't know if it was ammo or a buffer and spring issue.

Thanks for the reply.

Also wouldn't run a pistol without one of these, cheap upgrade.

https://www.bravocompanyusa.com/BCM-Extractor-Spring-Uprade-Kit-p/bcm-exspring-1.htm

Spikes t2 and a taran tactical spring is what i use in my sbr

Thanks man, I'll go ahead and order one of those.

That really depends on your gas port size. What 10.3" barrel do you have or plan to use? If it's a .070 gas port, I would suggest an H buffer and standard carbine spring for most ammo. That's what I use in my .070 CQBR, and it runs flawlessly with everything from Wolf to M193. Although, if you're primarily going to use full power 5.56, or it's going to be run suppressed, you will probably want to go with an H2.

If you have something like an older Daniel Defense 10.3" with a .082 GP, you'll likely need an H3.

Also, depending on who made your BCG, there is a good chance you already have an o-ring. They are pretty common. Personally, I use a Colt "copper" extractor spring with a Crane o-ring in my Toolcraft BCG. That being said, the stock Toolcraft o-ring and spring worked perfectly fine. I just like overkill ;p. Never had an extraction issue with the Colt/o-ring combo and I keep the TC spring as a spare. If you have a quality BCG that already includes an o-ring, I wouldn't worry about upgrading unless you're actually having extractor related malfunctions.

If your BCG doesn't have an o-ring, it's probably worth the upgrade just for peace of mind with a short barrel. Adding an o-ring is a standard reliability upgrade done by NSWC/Crane on the 10.3" Mk18/CQBR. If you want to purchase the o-rings by themselves, you're looking for Viton Heat Resistant O-ring size #006. Otherwise, as already suggested, BCM offers an upgrade kit and Sprinco does as well.

Holy information batman! I appreciate the response.

I will be buying this stripped upper receiver.

http://www.brownells.com/rifle-parts/receiver-parts/receivers/upper-receivers/mk18-stripped-socom-upper-receiver-w-handguard-only-prod81194.aspx

Haven't picked out a bcg yet honestly. Any suggestions?

I also plan on running it suppressed, not 100% of the time though.

I actually have the same upper. It's .070 and works great with an H buffer and standard carbine spring. You missed those being on sale just a week ago :\. Just FYI, joining Active Junky gives you an extra 4% off at Brownells plus $10 for signing up if you're invited by an existing member. I can shoot you an invite if you want.

As far as a BCG, I would highly recommend Toolcraft. They are excellent quality and very reasonably priced. They also come with an o-ring already installed, so don't need to worry about that. They currently have a contract to supply replacement BCGs to the military and they come with a lifetime no questions asked warranty - so they are definitely good to go.

You can get a TC nitride BCG w/ C158 bolt for $75 on sale right now:

http://skidtactical.com/store/toolcraft/5-56-bolt-carrier-group/

ETA: When running suppressed you'll probably want to go with an H2. If you already have a buffer, I'd suggest just buying some tungsten weights from KAK and then you can swap between H, H2 and H3 for a lot cheaper than buying individual buffers. One carbine buffer and 3 tungsten weights gives you the ability to make all 3.

I just ordered the upper 5 minutes ago. I appreciate the offer for the invite though.

I used their $20 off code + free shipping so I'm happy. I did see how I missed it for like $679 though, oh well.

Earlier I also ordered the Geissele Super 42 spring and it comes with an H1 buffer. We'll see if it's too heavy with 5.56. If so, I can always buy a lighter buffer.

Never heard of those bcg's, I will look into them. My normal go to is the BCM. I've had a cheap psa bcg and had minor fitment issues with it. I'm a fairly firm believer in "you get what you pay for."

Look into Toolcraft - I don't think I've ever heard a negative thing about them. They are definitely not a budget BCG, despite the price. Completely equal in quality to BCM, Colt, DD and so on in my opinion. Otherwise, that's mostly true that you get what you pay for. But, there are exceptions.

You could actually get one for $639 if you squeezed out every last discount ;p. I almost talked myself into buying another one, lol.

Meh, what's another $100+... And I will check them out.

Thanks for all the help, I really appreciate it.

It won't be too heavy with 5.56, usually buffer weight only becomes an issue when running cheap 223.

My gas port is a .76 and it runs cheap wolf with an H2. .70 and an H1 should run the cheap stuff too.

Toolcraft bcgs are fine and come with a spring and oring, I still upgrade them to the BCM.  BCM come with the upgrade pre-installed.

H2 as a starting point with a 10.3".

BCM's bcg's come with the upgraded spring and the o-ring? I didn't know that, thanks.

I have 5.56 and .223 but it's all "good stuff."

I'm wondering with a suppressor if the H1 will work.

Kind of a bump.

What does everyone think about the Gemtech suppressed bcg? Where all you have to do is turn a valve to go from unsuppressed to suppressed.

Is it worth it? Gemtech basically claims it's all you need to run a suppressed gun.