SPR Build: What rial/forearm? DONE!!!!! [Archive]

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Mauser KAR98K

12-12-12, 11:09

Not sure if this belongs here or the Custom build page, but I am racking my head over this SPR build I am doing.

I have a Rainer matched upper/lower that thus far I have assembled the lower and the basic upper parts. A barrel will come next month (Noveske 18.1" SPR).

I am very lost in what rail to place on it. What should the length be? Should I go a Noveske NSR, a Troy Alpha, a Daniel Defense, etc? What are the benefits of longer lengths (past 13 inches)? What are the benefits of the a recommend rail/tube for a precision build.

http://farm9.staticflickr.com/8055/8425911066_255863f8a7_b.jpg

http://farm9.staticflickr.com/8496/8425885224_d2a5819dd7_b.jpg

wlptpd3

12-12-12, 11:41

I just recently completed my SPR style upper and decided to go with the Centurion Arms 12" rail, I really liked the mounting system and I can tell you it is pretty solid once mounted. I looked at alot of different rails and kept coming back to the Centurion.

What sold me on the Centurion was the mounting system, you retain the factory barrel nut there is no proprietary or after market barrel nut used. I dont have alot of rounds through my SPR style upper yet basically just shot it for function testing but the Centurion seems rock solid.

Toyoland66

12-12-12, 12:00

Do you want quad rails or a slick rail?

Do you have the tools to install it yourself or will you have a gunsmith install?

Shooterman017

12-12-12, 13:48

I let what I wanted to use the rifle for dictate length. My rifle was put together as a do everything recce-style/carbine, so prone shooting for precision, home defense, and just about everything else under the sun. I first installed a Midwest Industries SS 15" rail. I wanted the extra length so I could run my hand further out front where I prefer it, and still have room for the bipod...just happens to help that having it out further works better...I wanted to keep weight down so went with something where I can move rail sections only where I needed them. Before I removed it and sold it, I had a VTAC mount with a Surefire G2X, an Atlas V8.1 and an AFG2 on it, and a KAC rail panel up top. I decided that even with the lack of 3 6 and 9 oclock continuous rail, it was a little too heavy when not shooting from prone with irons, the EOTech I had briefly mounted, or the Viper PST 1-4, and with the bipod removed.

I now have a URX 3.1 installed and it's just right for me. I'm expecting a Surefire 951 shortly, and because the profile of the rail is so much more thin I don't use an AFG...I still want to put some of the URX panels on the sides, maybe the handstop on the bottom...but I could totally live with it as it. Even with the bipod attached and not shooting prone it feels much more handy to me.

I wouldn't have any qualms about using another rail, the URX 3.1 just appealed to me the most for what I wanted to use the rifle for.

Mauser KAR98K

12-12-12, 14:21

Do you want quad rails or a slick rail?

Do you have the tools to install it yourself or will you have a gunsmith install?

I'm doing it myself. I have the tools.

But going quad or slick, that is what is raking my brain. I run a quad on my main weapon, but I am not sure of the advantages of running it on a SPR. This rifle will mostly be prone with a bipod.

The_Hammer_Man

12-12-12, 15:56

SPR's are be definition heavier than carbines. Rails add weight.

My personal SPR has a Samson EVO 15" on it and my carbine has a 12.37 Evo no it.

I can put my rail sections pretty much anywhere I wish and w/o the rail sections both of them weight under a pound.

Because my tube weighs so little I was able to go with a slightly heavier barrel profile and not break 10 lbs with my optic and bipod on it.

polymorpheous

12-12-12, 16:02

The Troy Alpha is light and cost efficient.
Noveske makes a low profile sling swivel that you can mount a Harris bipod on.

People usually run a 13" forearm on a 16" barrel.
I figure because the BUIS radius is close to that of a 20" rifle.

mic2377

12-12-12, 16:43

Personally, unless you are going hang lots of stuff off the rifle, I would go with a smooth handguard of some type. A Troy Alpha, Samson EVO, or MI Gen 2 SS would be perfect, in either 12" or 15" length depending on your preference. I have a 12" MI Gen 2 SS and like it very much. If you are into slim/light (VERY light) rails, it is a great choice.
Most of these rails come with provisions for a add-on section of rail as well, my MI came with 3 sections of rail and all of the hardware. This is ideal if you want to attach something like a bipod.

I am not much into full rails as I have never felt the need for that amount of real estate. Can't offer much advice here.

ASH556

12-12-12, 16:55

I agree with the smooth-type rail for a precision gun where you're not attaching much. If it were me, I'd use a Geissele SMR. 15" on an 18" barrel.

ALCOAR

12-12-12, 18:41

I'm biased as it's what I used on a new SPR build of mine, but I couldn't ask for anything else in a rail than what the SMR delivers for a precision AR.

The barrel nut design really helps with regards to precision/accuracy by adding rigidity and enhanced heat dissipation over conventional barrel nut designed rails as well.

http://i888.photobucket.com/albums/ac81/trident1982/DSC07024-1.jpg
http://i888.photobucket.com/albums/ac81/trident1982/DSC07053-1.jpg

ETA Benefits for going longer with rails:

1. Getting your bipod closer to the end of your barrel.
2. More rail surface area = more heat dissipated through it.
3. Protecting your actual barrel from hard use ..i.e. more rail covering more barrel

BrigandTwoFour

12-12-12, 18:46

The SMR is VERY nice.

If you want to keep weight and cost down and use the stock barrel nut, then I think the Troy Alpha or Samson Evolution series work very well. I particularly like the style of the Rainier Evolution (same as Samson, but different cutouts).

A longer rail out in the 15" range lets you get the bipod further out there, which is almost always a good thing for precision oriented rifles.

krisjon

12-15-12, 03:26

No scope yet, but I went 16.7 NSR/NST upper on my latest Noveske build. I've shot it with irons and it's just plain awesome and lightweight. Can't wait for a NF 2.5-10x32 on it.

Benito

12-20-12, 00:21

Wow Trident,
That is a very nice slick, minimalist setup you have there.
Also, I've become a bit of an ADM fanboy, myself.
What barrel length is that?
This maybe a bit off-topic but what do you guys think about using a chrome-lined lightweight profile 14.5" barrel for an "SPR-ish" build??
Yes, I know stainless is more accurate, heavier profiles have better harmonics, and longer ones have better velocity/trajectory, but that's why I added the "-ish" at the end.
Something to accurately hit out to say 500m?

Magic_Salad0892

12-20-12, 03:46

Gieselle, or KAC.

edgecrusher

12-20-12, 05:53

kind of surprised no one mentioned the PRI gen 3 forearms, I used one on my mk12 mod 0 build. This is my spr build, after duracoat.

djmorris

12-20-12, 08:20

I'd go with the Troy Alpha Rail. You can pick up a brand new 13.8" for like $150 on Ebay. Can't beat that.

ZoneOne

12-21-12, 18:52

I went with a Midwest Industries T series 12"

I've used some MI products before and they where all very good. Never used their rails until now.

It has the look that I'm going for and it's definitely with in my budget.

chakup

12-22-12, 10:55

Kinda old thread but I love my Apex handguard

308sako

12-23-12, 21:03

Yes, it's just doesn't get the exposure it deserves.

http://i181.photobucket.com/albums/x160/308sako/RockPebble.jpg

Mauser KAR98K

12-24-12, 10:22

Thank you for the responses. I am actually leaning towards the PRI MKIII 15", but I am still on the fence with all of you all's suggestions. Sign. So many choices. If a ban wasn't being proposed, I would not be freaking out.

I have a larger question:

Should I wait for Noveske to get the 18" SPR barrels back in stock, or should I go with a Rainier 18" while they are still in stock?

What is the difference between the two? What is the advantages of a 1/8 twist rate? What are the advantages of Noveske's SPR gas system?

http://www.rogtac.com/rainier-arms-medcon-barrel-18.html
Thank you all.

chakup

12-24-12, 10:58

My SPR has a WOA barrel so I'm not much help there. Rainier barrels get good reviews and will be cheaper than Noveske. Noveske barrels are just amazing but ya pay for it.
And here's my Apex on a 14.5" Noveske barrel for more pics!

http://i1260.photobucket.com/albums/ii580/gunzforsale/20121224_085654.jpg
http://i1260.photobucket.com/albums/ii580/gunzforsale/20121224_085630.jpg

Mauser KAR98K

01-01-13, 10:43

Just ordered a Navy SPR 18" barrel from Fulton. It is described as an "overrun." I am going to make this into a MK12 for sure now. Gaining the funds for the PRI GenIII; just deciding to either go the 15" or 12". I have a low-profile gas block, so the 15" should fit around it.

Question is: What gas tube does their barrel require, and what muzzle device should I use? I was thinking of going with the expensive Ops Inc 12th, but am highly considering an AAC blackout FN.

http://www.fulton-armory.com/barreldouglas18navysprcm1x8threaded.aspx

BrigandTwoFour

01-01-13, 14:41

I really like the look of that Apex tube. I'm planning to use one on my .308 SPR project.

As far as the Fulton Navy-SPR barrel, the description says it's a rifle gas length. Grab a rifle gas tube and you should be set.

Muzzle devices are a personal thing. My Recce-ish carbine uses the AAC Blackout, and I'm happy with it. Took me a while to start ignoring the tuning fork style ringing after each shot.

If this gun is pretty much a range toy, or you plan on mounting a suppressor some day, I'd go ahead and get the brake. If you plan on suppressing it, then figure out what suppressor you want and get the brake that fits it. If you just want a brake, I've heard a lot of good things about the Z-Comp that recently came out. But there are a lot of other decent ones around, I'm sure a good search will turn up lots of good choices.

ra2bach

01-01-13, 14:43

I like the Centurion rails. fairly light weight while very sturdy, and use the existing barrel barrel nut. the only problem in your case is that they top out at 12" and for an 18" barrel I'd want something a little longer.

with 18" barrel I'd look at the new Geiselle 15" but it is more money and uses a proprietary barrel nut which if you didn't have the tools and expertise to change would add gunsmithing costs...

Mauser KAR98K

01-01-13, 16:41

I am going to confirm my decision on creating a MK12 Mod 0. I am ordering the PRI front sight/gas block base, and I guess the rifle length GENIII handguard for it. I have been bitten by the bug. Since I am getting the true Navy SPR barrel, might as well.

BrigandTwoFour

01-01-13, 20:24

Nothing wrong with that. Enjoy it! I've been wanting to try some higher powered glass on my Centurion CHF-Barreled carbine. The TR24 is fun, but I want to see what I can do with a 3-9 or so.

skywalkrNCSU

01-01-13, 21:09

Just ordered the Evolution 15" rail from Rainier for my SPR rail, it was either that or the Troy Alpha.

The_Hammer_Man

01-02-13, 15:16

You'll like the Rainier/Samson tube.

Just make sure you install the heat sinks properly. Open hole goes under the barrel!

Made the mistake of reversing a set. Took forever to tweak the tube back into spec.

skywalkrNCSU

01-02-13, 17:23

BiggLee71

01-05-13, 20:05

Mauser, good choice with going the PRI MOD 0 direction. I always wanted one myself. I own a Knights SR-15 Match which is basically a MOD 1. Now you have me itching to build a MOD 0 myself!!!

And Trident 82, beautiful sticks....as usual.

Mauser KAR98K

01-17-13, 22:09

Quick update:

I am not going the FULL Mod 0 route. I have, though ordered the PRI tube, raised rail system (name escapes me), gas tube, OP 12 muzzle brake. What is making this a 90% version is the choice in stock, and a low pro-gas block.

Thus far, how it looks since the barrel came in today.

http://farm9.staticflickr.com/8229/8391480840_1753412fec_b.jpg

Douglas barrel SPR Navy over run from Fulton-Armory. 1x8" twist, HBAR, rifle length gas system and chrome moly. Chamber says:

FA 2 3 9.

Barrel was rather stiff getting seated into the upper receiver.

http://farm9.staticflickr.com/8498/8390483583_075c93668b_b.jpg

Sorry for crappy pics and dirty floor.

Mauser KAR98K

01-18-13, 20:59

My gas block and gas tube are stuck half way and I cannot remove the tube from the block. I greased it on my first attempt, but no it is stuck? What can I do, I am I screwed?

Pic!

http://farm9.staticflickr.com/8214/8393099053_896494eb12_b.jpg

Picture of build thus far.

http://farm9.staticflickr.com/8464/8393102467_f96f72b660_b.jpg

wetidlerjr

01-18-13, 21:49

My gas block and gas tube are stuck half way and I cannot remove the tube from the block. I greased it on my first attempt, but no it is stuck? What can I do, I am I screwed?...

I would try some penetrating oil (Kroil) or try freezing the parts or heating the parts (causing expansion or contraction). Is the gas block steel or aluminum?

ridgerunner70

01-18-13, 21:57

Mauser KAR98K

01-18-13, 21:57

I would try some penetrating oil (Kroil) or try freezing the parts or heating the parts (causing expansion or contraction). Is the gas block steel or aluminum?

Steel.

tresmonos

01-18-13, 22:42

Mauser KAR98K

01-18-13, 23:53

soak it in a penetrating oil overnight. If that doesn't work, grip the gas tube with some parallel jaw pliers (not squeezing hard enough to crimp the tube) and lightly tap the pliers head with a hammer.

If you're forced to replace the gas tube, pinch the gas tube with some wire cutters or dykes; using the gas block as the fulcrum (of a lever), wiggle the tube out of the block. Or hold the gas tube and beat the block off of it with a rubber mallet.

Maybe I'm too used to building AK's, as I'm not at all afraid to beat on a firearm with a mallet.

Wilco on the oil. I inadvertently forced the tube into it gas block and in my efforts I had opened the gas hole in the tube a bit. Any negative effects?

Why do I go for the most expensive stuff on my first builds at anything...? Mind over matter= matter wins.

The_Hammer_Man

01-19-13, 02:57

The size of the port hole in the gas tube makes much less difference than the tubes overall integrity.

In your efforts to insert/extract the tube did you damage it? Any cracks or the like?

If not.. don't worry about it.

Now as to fit... I have, on occasion had to ream the tube hole in a gas block. Even high end products are sometimes out of spec.

To avoid this in the future get a tube and gas block from the same manufacturer. "Usually" their proprietary parts will socket together w/o binding.

When/If you decide to mod the parts for fit do NOT mod your tube!!!!

Mod the gb instead.

chakup

01-19-13, 11:10

The_Hammer_Man

01-19-13, 11:43

RHINOWSO

01-19-13, 14:04

Sweet build!

Mauser KAR98K

01-19-13, 21:56

Slide a thin allen wrench or similiar through the gastube hole to get some leverage and slowly walk it out. I've had a couple do this. On one I just finished seating the gastube and took some work to align the holes but it wasn't going anywhere.

THIS is why I put anti-sieze grease on my gas tubes before inserting them.

If I had a dollar for every time I had to wrestle with seized tube I'd be a billionaire :)

Thank God I am not the only one. :sad::rolleyes:

I did the allen wrench and I did the anti-seize, and I am stuck. Been a little too busy to put the liquid wrench on it, but I am worried it is stuck in there for good. (I wen ahead and ordered another GB and tube from Bravo--PRI's cross-bolt GB/front-sight). I am going to try to salvage it.

Mauser KAR98K

01-19-13, 21:57

Sweet build!

Thanks.

Will be better once I can get out and shoot it.

Mauser KAR98K

01-25-13, 13:21

Update yet again, and it is STILL not finished.

The top rail I ordered from PRI was for their delta handguard, so I had returned it for the correct one, plus more proper tools. If anyone in my area is looking for a MK12 repair shop, they can come to me.

I bought the front-site, gas block from BCM, alas it is the cross bolt. lock tight will be in order.

I did get to shoot it. 6 rounds without fail or malfunction. But I have to take it apart to get the top rail on, and to double check the barrel nut. This is my first full complete build and I was ecstatic to say the least that it worked.

Pics.

http://farm9.staticflickr.com/8369/8414968682_3091a9e692_b.jpg

http://farm9.staticflickr.com/8331/8414963602_2c23dc6605_b.jpg

http://farm9.staticflickr.com/8232/8413857479_a09a4cef3c_b.jpg

mic2377

01-26-13, 12:30

Looks great! Digging the whole combination! Just needs an NF optic on top :)

Mauser KAR98K

01-28-13, 20:23

Project complete. Sorry, mic227, Vortex 5X15 Viper HD.

http://farm9.staticflickr.com/8073/8424790663_cdf17401a0_b.jpg

Got to test fire it once more after a few tweaks and scrutinizing adjustments. Overall, it is solid: 14 pounds there are about's. Have not tested accuracy as of yet.

I put the scope on the rings myself with a leveler and ruler. I am going to take it to my local gunsmith Thursday for a final fit and torque down of the screws.

Harris bipod rocks, but I have it on a YHM bipod adapter.

Changed the hand grip to a Bravo: much nicer feel; a bit more natural (but I still love the MIAD grips).

VLTOR EMOD is perfect for this, and I do not have a cheek weld issue, surprisingly when I was fearing the ADM 20MOA Recon rings and base was going to make it too tall with the PRI top rail riser.

http://farm9.staticflickr.com/8491/8425876724_44eb17dc80_b.jpg

Yes I have a hand stop behind the bipod. No I am not taking it off because it works just fine for me. I need to get some rail protectors and a gear sector hand stop just behind the bipod in order to not scratch the hell out my hand.

The Ops Inc muzzle brake will take some getting used to; but it would not be a MK12 without it.

http://farm9.staticflickr.com/8353/8424782529_7394a2fdd4_b.jpg

This was my first build from top to bottom (minus machining). I am rather satisfied and proud of myself in taking the effort to really do this. By no means this could have been done a lot better, a little cheaper by getting the correct parts and tools, and less scratches by using masking tape next time. To be honest I should have built a mid-length fist before this, but the political climate and availability of parts in a way forced me to go the MK12 route in the end.

I had set out to make a SPR and the thread was started to ask what rail system to get. But alas, the gamer in my latched on to the MK12 Mod 0 in one of the games I frequent: AMRA2 with the ACE mod. I studied and looked into it and decided I was going to make a semi-clone of it. By the grace of God my Google-fu led me to Fullton Armory and a "NAVY SPR overrun" on Douglas SS blanks. Everything else either PRI or BCM actually had in stock.

Troubles and problems:

Gas block and tube did not fit. Ended up ordering the PRI cross bolt gas block w/front sight and another gas tube. Fit was perfect.
Get the correct tools and parts. Saves money and goes along way. Plus I am I can now open a MK12 MOD 0 repair shop in my local area.
Had to replace the crush washer after removing the muzzle brake for checks.
scratches here and there: masking tape next time.

Hopefully this weekend I can sight it in and see how it groups.

Thanks everyone who contributed.

Pictured with my new Glock 22 and Pelican case.

http://farm9.staticflickr.com/8496/8425885224_d2a5819dd7_b.jpg

What DiFi would like me to build.

http://farm9.staticflickr.com/8516/8425889596_19f402be05_b.jpg

ShootinRN

01-28-13, 21:21

Very nice...and I would imagine extremely gratifying.

Love the last pic....!