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View Full Version : Building an SPR any advice?


islice
10-31-2010, 9:05 PM
Im in the process of building an SPR and I thought I'd ask for some suggestions, opinions, and i guess considerations i should make. Heres the current set up i was thinking of:

Upper receiver: ZEDU MEGA (had from a previous supposed too build)
Lower receiver: MEGA GTR-3S (already had from another build)
Barrel: Sabre Defense SS 5.56 18" midlength gas system
Handguard:Larue 12" handguard
Optics:Ehhh....thats a whole other question altogether deal with later
BUIS:TROY front and rear
Stock:A2 stock or UBR
Bipod:Harris 6-9 with larue adapter
Grip:Magpul MOE
BCG:BCM BCG
Charge Handle: BCM Mod 4
Trigger:Standard Mil-Spec
Brake:Surefire MB556K

Dont think i missed anything major. Let me know if i did. So, let me know what you think. Thanks in advance.

pyro3k2
10-31-2010, 9:19 PM
what is the twist rate on the barrel and you need to get it in a rifle length gas system to be in SPR spec, other wise it looks good so far.

PS stick with the A2 stock for this build and spend the extra money on a scope or ammo.

islice
10-31-2010, 9:33 PM
what is the twist rate on the barrel and you need to get it in a rifle length gas system to be in SPR spec, other wise it looks good so far.

PS stick with the A2 stock for this build and spend the extra money on a scope or ammo.

The twist rate is 1/8. There is some debates ive read about the gas system length. I know the true SPR is rifle length, but ive read while doing research that the dwell time between the gas block and end of the barrel may be too short for an 18" barrel and could cause short stroking in the operation. I know the majority use rifle length gas systems for SPRs but is there a huge difference in using midlenth rather than rifle length for an 18" barrel? Id like to hear opinions on this as well.

But if i do go with a rifle length barrel id probably go with the BCM SS ionbonded 18" barrel.

Thanks again for your opinion. Its exactly why i posted my potential build.

neal0124
10-31-2010, 10:06 PM
I went with a rifle length gas system on my mk12 mod0 rifle and it functions perfectly with everything I've shot through it, all sorts of factory ammo and hand loads with several different types of powder that I've tested with. I also have a 1/7 twist barrel. All my hand loads have been with 77gr SMK's.
I had a UBR stock on mine for a while, I changed it out to an A2 and like it much better. I only have an A2 birdcage on it now, but after putting a battlecomp on my carbine I've decided that one will also eventually go on the SPR. I should be able to keep the target sighted in with it on. I was thinking about putting the ops inc comp on the rifle but I shoot from a bench and figured the battle comp will be more friendly to the people next to me, plus I'm never gonna be able to put a suppressor on it so it would just be a waste.
Start reloading. You'll really see a difference in accuracy with the 77gr SMK's.

killshot44
11-01-2010, 12:33 AM
Send your trigger to Bill Springfield, he'll send it back with a 3lb or 4lb (your choice) pull for around $50. http://triggerwork.net/ar15s.html

Look at White Oak Armament's barrels, they are fantastic. Get a 1/8, full-length gas. Happy Time.

PEBKAC
11-01-2010, 9:38 AM
You would probably save some dough if you went with a WOA barrel instead of a Saber.

NewGunner
11-01-2010, 9:51 AM
Pretty much have the same setup you are thinking about but with a WOA barrel in midlenght, giessele trigger, and a billet mega upper. It is a sub MOA gun shouldered with bipod out front and my 69gr reloads. It took a couple months to develop the skills to shoot it sub MOA but I couldn't be happier. That is also with a not-so-good Millet 1-4 scope.

You should skip the BUIS for now and invest that money in the trigger. That is just my opinion and assuming you will have a scope on the gun.

Omega13device
11-01-2010, 9:54 AM
I know the true SPR is rifle length, but ive read while doing research that the dwell time between the gas block and end of the barrel may be too short for an 18" barrel and could cause short stroking in the operation.
If rifle gas were a problem do you really think they would have used it on the real ones?

rero360
11-01-2010, 10:24 AM
Rifle length gas system with Larue gas block.
WOA Barrel
Better Trigger
Atlas Bipod or the Larue Harris with the intigrated QD mount unless you already have a Harris you want to use.
Other than that everything looks pretty good to me.

Optics, USO SN-3 1.8-10x with a USO or Larue QD ring/ mount set up.

dawson8r
11-01-2010, 10:32 PM
I went the "cheap" route and picked up a cmmg 18" with midlength gas. With medium contour barrel and pws 556 brake hardly even moves off target. Spent the savings on a acog ta31. It is my shtf zombie snuffer!