Im building an SBR...

[Mr.Goodtimes]

Im going to start piecing together my first SBR (and first NFA item) build here soon and am debating weather or not to go piston or DI.

Im a left handed shooter, and the gun will be run mostly suppressed with an AAC M4 2000. Ill be buying both gun and suppressor at the same time.

The only piston system im really considering is the LMT MRP. Whats the deal with these? how bad is carrier tilt? bolt life?

If i stuck with a DI gun, would the blow back be to much to handle conidering im left handed?

Weather i go Piston or not, im most likely going to go with an MRP upper. If i go piston, it will be the 12.5 variety, if DI ill go the 10.5 route.

[LonghunterCO]

So I see what you are looking for in your SBR build, but I am not seeing what you are wanting to do with it. Have you looked in the weight of the LMT MRP vs. a DI upper? Is this increased weight worth the ability to quickly change out the barrel on a SBR? Have you looked into the advantages of a piston on weapon that is going to be ran mostly with a can?

[Mr.Goodtimes]

Gun is going to be a gun for the range (training) and serious social purposes (home defense, etc..).

From my understanding, Piston seems to be most usefull in supressed rifles and SBR, or a combination of the two. My big question, though, is do the positives out weigh the negatives?

How bad is blow back out of a short barreled suppressed gun?

Also, the reason I want to go with the MRP is for its strength, rigitity, and modularity.

Im not concerned with weight. Less weight is better, but, im not a weight faggot. If a piston driven system offers a signifigant advantage in terms of shootability and reliability, then ill suck up the extra few ounces.

My main concern is blow back. Being a left handed shooter, that leaves me more succeptable to it. Just how bad can i expect the blow back to be out of a 10.5 with say an M41k or M42k on the muzzle?

[foxjordan22]

piston guns shine with barrel lengths below 10.5, or running a suppressor. with your face behind the ejection port the blow back and gas will be a big concern. a piston will stop the gas from going into the receiver, but wont help with the blow back from the can. the total ammount of gas in your face will be noticeably less though with the piston. i know you like the LMT but ADDAX tactical has a great 11.5 gas piston upper than can be orderd with a left sided ejection port. this would eliminate most of your problems. if i was a lefty this would be my setup. here is the link. http://www.adxtactical.com/store/pc/viewPrd.asp?idproduct=1331&idcategory=172

[ekujustice]

I would just build a left hand gun

[buddyhoohaw]

FWIW, I have multiple SBR's and no suppressors because I am a left-handed shooter. I find the blow-back associated with left-handed, suppressed shooting to be prohibitive and counter productive. One of my shooting buddies has suppressed, piston SBR's in both 5.56 and 6.8 and I have noticed little relief regarding blow-back over a DI. I considered building a left-handed upper in order to host a suppressor however for my use it just wasn't for me; I invested in a nice pair of electronic muffs instead. Just my opinion and your mileage may vary.

Cheers

[Nevermiss]

Mr. G. I was in the exact same boat a few months ago looking for an SBR to run mostly suppressed and to have available for home defense.

I went with a Noveske 6.8 12.5" with Switchblock.

I was also considering all of the same things that you are (except I am right handed) and they are all good options.

[No Bananas]

I have a DI 12.5" and an Adams Arms Piston conversion on a 10.5". Reliability (thus far - about 1000 rounds for both) has been great for both. The only difference I've noticed is in cleaning. The piston is much cleaner. Particularly in carbon build up on the bolt and bolt carrier. No that doesn't mean that it never needs to be cleaned, but there's a lot less elbow grease involved. You said that you would mostly be shooting suppressed. For that reason alone, I'd say go piston.

[edwin907]

I'm a left handed shooter, run multiple SBR & 16+" uppers with suppressors, have never used a Noveske switchblock, and I have little problem with blowback. I have a PRI Gas Buster CH on all of these suppressed uppers and that's it.

On my Recon and two 18" SPRs, I use the OPS 12th and blowback is minimal at worst, even running the weapon fairly wet.

The 10.5" to 14.5" uppers (SpecWar2) have more blowback, but it's hardly a deal breaker. The 14.5" mid-length CLE WOA barrel in particular gives very little gas in your face, it's almost as good as the Mod0/OPS 12th. Now the SpecWar is a big, heavy, quiet suppressor, with good internal volume.

Might be a good idea to check the barrel port size, if there is excessive blowback on your particular combination.
I was worried about my new Bushmaster 11.5" 1/7 HBAR barrel, but it's just like my LMTs, with a properly sized gas port (unlike the 14.5" and 16" barrels with an oversized port).