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: 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
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
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.
Dont think i missed anything major. Let me know if i did. So, let me know what you think. Thanks in advance.
I just finished building my own SPR and am really happy with the results. I’m not a professional builder or a mechanical engineer but, like you, I did my research and built what I thought would work best. It looks to me like you’re on the right track. I would reconsider using a mid length gas barrel. Find a barrel with rifle or intermediate gas from a reputable manufacturer an you should be fine or get a full upper. If you were having a short stroking issue from running rifle gas you could probably fix it by installing a low mass BCG or having a gunsmith open up the gas port a little. The advantage over mid length gas would be slightly smoother cycling. I think the A2 stock is a really good idea. Also, you’ll be pretty limited by the standard trigger. One of the best things about a real MK12 SPR si the tuned trigger. I would recommend a Geiselle or JP trigger or a Bill Springfield tune at a minimum. Also make sure you budget for decent glass.
Thanks for the advice! I’ll look at getting a tuned trigger now. Talking about barrels, any thoughts on the BCM SS 18" i was also considering? Thanks again.
I would also suggest a better trigger. For the barrel, i would look into centurion arms mk12 barrel. Nothing wrong with saber or
bcm, but at least check them out. I have their mk12 upper and couldn’t be happier.
I just finished an SPR build, and I would say you are well on your way.
I went with a Noveske 18" BBL using an intermediate gas system and it seems to cycle just fine with an H-Buffer using XM193, PRVI M855, PRVI 75Grain Match and Hornady 68gr and 75gr ammo.
I used a LaRue 13.2" rail to make sure the gas block is covered up.
The other bbl sugestions have all been top notch, Centurian makes an awesome barrel, as does BCM and Sabre.
Right now I have a standard trigger, but that is because this weekend was the first time I have shot anything firther than 25 yards lol. So I need to gain experience before I invest in a trigger. Right now, the rifle is better than I am, having said that, I could see where having a better trigger will help your goal. If you already have the experiance that I lack, you might as well look into a better trigger to begin with.
In your quest for glass, I will just say that I love my choice of Nightforce 2.5-10x32. Though at 200 yards I can’t see that little 5.56 hole and wish I did lol.
Yup, If i went with the rifle length gas system, which i’m kind of leaning towards now, I would definitely go with the 13.2 inch larue.
Im in the same boat as you. I would probably want to gain more experience with my SPR before i invest in a trigger. Ive done a few carbine classes and own 2 AR’s but id imagine that shooting an SPR is a little different with more considerations. Ill probably start with a standard trigger and then invest in something more advanced when im comfortable.
Since you brought up optics, along with anyone else, my friend is selling his Leupold Mk4 M1 scope to me for a pretty decent price, so for now that is what i will probably go with since he’s willing to hold it for me till im ready to buy it. But, you never know by the time im ready to buy it, i may change my mind haha.
The upper is a LaRue Stealth with an 18" ion bond barrel, 13.2" hand guards, and an LMT charging handle.
Since this photo was taken, the flash hider has been replaced with a Battlecomp 1.0 compensator.
Scope is a Mueller 8.5-25x44AO Tactical Mildot on a LaRue SPR-E QD mount.
Bipod is a Harris on a LaRue QD mount.
I didn’t bother mounting BUIS because this is a range tool, and back-up sights would be pointless.
The lower is a LaRue billet with a 3# Timney trigger, KNS pins, Phase 5 Tactical EBRv2, and a Rock River A2 stock.
Sling is a padded LaRue with my modifications.
This target was shot using two 20 round Magpul magazines loaded with 75gr Privi Match ammo at 100 yds (the limit of my club range).
Notice that out of 40 rounds, only 1 round is outside the 10 ring.
I hope to do even better with some other match ammo that I just bought.
Not trying to call you out, just trying to develop this thread. I’m not sure I understand this reasoning. If I’m shooting and I make a bad shot I want to know it’s me, not my equipment. It’s actually a lot easier to shoot with a good trigger, so it seems to me that one would want to start out with a good one and see if they could cope with a bad one when they get better.
No worries. Since I started this thread. I have been back and forth on alot of my original decisions. The trigger was big one. I believe your right about starting out with a good trigger, so for now anyway, my decision will be to get the G&R LPK less trigger group and most likely go with the Geissele Combat Trigger - SSA.
Thanks everyone for your input so far. It is really appreciated.
It was my first build ever and I have to say, when I pressed the trigger for the first time and it actualy shot, cycled and locked back on an empty mag, I was a very proud papa. LOL I was half expecting to have to come on here and have to post asking what I did wrong lol.
Now I just have to get a true accuracy test out of it. I went to shoot it at 100/200 yards this past weekend, but I had no way of supporting the stock so its hard to judge but I was still able to keep most groups within 2" at 100yards in 10-15mph gusts.
In regards to that group posted: Privi 75 gr OTM is not very accurate. I know that Molon was able to get amazing groups with Privi, but for my friends and I, Privi 75 gr’s accuracy has been subpar compared to SMK 77 gr.
I shot 1K of the factory stuff, and thought the lack of accuracy was due to factory loadings. Handloads with Privi projectiles weren’t much better.
The difference between 77 gr Sierra Match Kings and Privi’s 75 gr OTMs was like night and day.
For example, I went to a long range shoot near Bend, OR this summer, and rezeroed for the 5K gain in elevation. These are just casual groups at 50 yards shot off of dried mud with a Harris bipod
Performance at extended ranges confirmed my informal findings, that while Privi 75 gr is better than XM-193, it’s not up to par of quality American projectiles.
I’ll want to experiment with Hornady 75 gr projectiles eventually
Have not had a chance to buy any 77gr Sierra Match King yet, but in addition to the Privi, I have some Wolf Gold Match (75gr, BTHP, brass case) that I want to try.
Just have not had the time.
I don’t handload (and have no plans to), so using commercial loads will have to suffice for now.
Also, my clubs high power range is limited to 100 yards, so that is what I shoot.
Edit: I also have a couple of boxes of Hornady TAP (75gr BTHP) Training ammo, but have not had a chance to shoot that one either.
Instead of the SSA, I would recommend you look into the SSA-E or one the new designs due for release through Midway in the near future. The SSA has a pull in the 4.5 lb range, but for an SPR, I would recommend a G trigger in the 3.5 lb or less range.
I recently bought a BCM SPR MK12 with the 18" SS410 Ion Bond barrel. It has the rifle length gas system and has run perfectly will all ammunition so far, and is extremely accurate. The rifle length gas system is very soft shooting, and I am running an H3 buffer as recommended by Paul the owner of Bravo Company.
I recently shot back to back sub 1/2 MOA groups at 200yds (5 rounds less than an inch), and have several groups less than 0.5 an inch at 100yards. This rifle surpasses the accuracy I have been able to get from my Lothar Walther barreled Recce.
The rifle was perfect when delivered, is 100% reliable, and amazingly accurate. I highly recommend the BCM SPR uppers and barrels.
Specs:
Bravo Company Manufacturing in house upper - BCM Mk 12 Mod 3X-Bravo (DD14)
BCM 18” SS410 Ion Bond DLC Stainless Steel 1 in 8” twist barrel 5.56 USMC SAM-R chamber A2 Flash Hider
Rifle Length gas system with H3 buffer
BCM bolt carrier group
Daniel Defense 14.0 Lite rail
Leupold MK4 4.5-14x50mm Tactical Milling Reticle Larue SPR QD mount
BCM/Troy back up iron sights
Harris Ultra Light Bipod
Bravo Company Manufacturing lower
LMT 2 stage match trigger
Magpul UBR stock
Magpul MOE grip
Magpul MOE trigger guard
Magpul XTM rail panels
Magpul BAD lever
KNS anti rotation pins
Vickers Combat Applications padded two point sling
