Questions for AR-15 SPR and LW carbine build.

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So like the title suggests I have questions about an SPR and carbine build I have been working on for awhile now. I'll list my current parts list for each of them and follow it up with questions about improvements to make.

SPR: DPMS upper/lower receiver
criterion 18" hybrid contour barrel 1:8 twist, rifle length gas system
surefire muzzle brake
troy 15" free floating quad rail, low profile gas block
bravo company medium sized charging handle
standard dpms trigger
magpul UBR adjustable butt-stock
bravo company gunfighter grip
trijicon 1-4 scope (30mm tube) with burris QD unimount.
Notes: Yes I intended the rifle to be heavy from the get go, wasn't looking to make a light weight SPR, just a medium weight/range (300-500yds or so) bench/field rifle.

LW carbine: Stag Arms upper/lower receiver
brownells 14.5" gov't contour barrel 1:7 twist, carbine length gas system
troy 11" alpha rail, free floating, low profile gas block
double star ARFX skeleton buttstock, A2 length
magpul MOE pistol grip
Miculek muzzle brake
standard stag arms trigger
I have an eotech and leupold delta point red dot but can't decide which one to use

Sor here are my questions. #1 on both of my rifles I notice that there is a very slight jiggle between the upper and lower, does anyone know if that affects accuracy or how to fix it? #2 is an 18" barrel adequate for the types of ranges I am looking to shoot my SPR from? 3# I really want to switch up my optics on the SPR, what would you guys recommend? #4 for both rifles what kind of triggers would you recommend I swap them with if at all, I prefer a light trigger pull but it really only makes a big difference when I'm shooting a long distances. #5 Are there any other weight saving measures you would recommend for the LW carbine? #6 Some magazines I have will not seat properly in the magwell of my DPMS, what could be the cause of that and is this common? #7 If there is any advice at ALL that you could give to make some sort of improvements to either I am all ears. These have been two project rifles for a number of years and I'm just getting around to finishing them up.

Thanks for any input.

 

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So like the title suggests I have questions about an SPR and carbine build I have been working on for awhile now. I'll list my current parts list for each of them and follow it up with questions about improvements to make.

SPR: DPMS upper/lower receiver
criterion 18" hybrid contour barrel 1:8 twist, rifle length gas system
surefire muzzle brake
troy 15" free floating quad rail, low profile gas block
bravo company medium sized charging handle
standard dpms trigger
magpul UBR adjustable butt-stock
bravo company gunfighter grip
trijicon 1-4 scope (30mm tube) with burris QD unimount.
Notes: Yes I intended the rifle to be heavy from the get go, wasn't looking to make a light weight SPR, just a medium weight/range (300-500yds or so) bench/field rifle.

LW carbine: Stag Arms upper/lower receiver
brownells 14.5" gov't contour barrel 1:7 twist, carbine length gas system
troy 11" alpha rail, free floating, low profile gas block
double star ARFX skeleton buttstock, A2 length
magpul MOE pistol grip
Miculek muzzle brake
standard stag arms trigger
I have an eotech and leupold delta point red dot but can't decide which one to use

Sor here are my questions. #1 on both of my rifles I notice that there is a very slight jiggle between the upper and lower, does anyone know if that affects accuracy or how to fix it? #2 is an 18" barrel adequate for the types of ranges I am looking to shoot my SPR from? 3# I really want to switch up my optics on the SPR, what would you guys recommend? #4 for both rifles what kind of triggers would you recommend I swap them with if at all, I prefer a light trigger pull but it really only makes a big difference when I'm shooting a long distances. #5 Are there any other weight saving measures you would recommend for the LW carbine? #6 Some magazines I have will not seat properly in the magwell of my DPMS, what could be the cause of that and is this common? #7 If there is any advice at ALL that you could give to make some sort of improvements to either I am all ears. These have been two project rifles for a number of years and I'm just getting around to finishing them up.

Thanks for any input.

Cool builds. I'll take a stab at a few of your comments/questions:

1)The jiggle doesn't effect accuracy too much from my reading. You could install an Accuwedge or just add a #7 o-ring around the front lug to tighten up the receiver slop. The rattle can be a little annoying and won't help accuracy any.

2) An 18' barrel is a great SPR length and the most popular. That Criterion is a shooter I bet. Should be great with Hi BC rounds out past 800y.

3)For optics, a great config for an SPR is a 2.5-10x. The military has used Nightforce in that config and overall would be my pic if you could afford one. For a little cheaper, the newer Vortex PST 2.5-10x32 gets rave reviews. I'd move the Triji over to the LW carbine, and that happens to be my favorite 1-4x24 out here right now... love that glass and true 1x.

4) For triggers you will find almost everyone says (including me) that Geissele is the overall best trigger on the market. I love my SSA-E in my SPR. I'd do that in the SPR (2-stage) and either a SSA or the cheaper G2S 2-stage in the carbine. I haven't used their 1 stage, but guys love them and you should check them out too.

5)You can save weight in a few ways. Light optics (like the triji) and light weight mounts help a ton. The Skeleton stock should be pretty light. Govt barrel is a little heavier than a light weight profile, but not too bad. Troys are nice and light. I'm running a polymer lower on a AR pistol (New Frontier Armory $99)and it is super light with a LW profile 11.5" BCM barrel and 11" Rainier Evo rail.

6) The mag not seating on the DPMS could be from out of spec machining, or maybe just the magazine catch is funny some how. Check it for burs or any obvious fitment issues. I haven't looked into that issue before, arfcom has several topics on that I'm sure.

Nice builds! Only thing I'd personally change are the triggers and get the glass you want on there. When you get 'em all dialed in, post up some pics.

 

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I appreciate the input. I'll check into the accu-wedge, found some on amazon for like $2 a piece so hopefully it'll be a quick fix. I looked at both the optics you mentioned And I'll have to wait till next paycheck for one of those, same with the triggers haha. I was a bit surprised that you recommended nothing over 10x, although I've spoiled myself a bit when it comes to optics. And I should have mentioned this before put both rifles are chambered for 223/5.56 NATO, the criterion has a 223 wylde chamber. Will a heavier 5.56 round really reach out that far? I was under the impression that the most you would get out of it was 500yds or so. But yeah when I get them together I'll post some pics of the finished products and range reports. Thanks for the help!