SPR questions

[mike452]

Hey guys,

I want to put a SPR together, but have some questions:

1. Do they make SPR barrels with 1:8 twist? I don't have any special purpose except to shoot mostly 55 gr. and 62 gr. ammo.

2. M4 Extension on the barrel will work with NO extension on the upper receiver (MEGA)?

stainless or chrome lined?
mid-gas
Midevel Muzzle Brake
Magpul PRS
YHM Specter XL

Thanks!

[Prc329]

From what Steve at Adco told me, a barrel with M4 extensions will work in an upper without but it will not reliably feed the other way around. I have not seen any SPR barrels in 1-8, that does not mean someone makes one. You could probably get a barrel recontured to SPR that is a 1-8, that is if you truely need an SPR contour or you just want to build one in the spirt of one.

[6172crew]

Hey guys,

I want to put a SPR together, but have some questions:

1. Do they make SPR barrels with 1:8 twist? I don't have any special purpose except to shoot mostly 55 gr. and 62 gr. ammo.

2. M4 Extension on the barrel will work with NO extension on the upper receiver (MEGA)?

stainless or chrome lined?
mid-gas
Midevel Muzzle Brake
Magpul PRS
YHM Specter XL

Thanks!

The SPR is made for 1/7 but I think they do make a 1/8...look at CMMG which is chrome lined. Im going to use a Mega upper w/o any extentions yet the barrel has them.

The WOA barrels are rifle length gas systems but the Noveske ones are midlength as well as some others. The other stuff is whatever turns ya on.

[bwiese]

The orig SPR spec was, in fact, 1/8" twist 18" barrel.

Quite a few folks are making SPR bbls with 1/7" twist since they're just turning down 'bull' barrels.

Depending on mfgr there may be a choice of gas tap - carbine position or "middy", with middy being preferable. You may be able to choose front sight position as well - rifle or middy position (though I believe true SPR has front sight at rifle position)

Both CMMG and Sabre Defence advertise chrome-lined 18" SPR-profile barrels, and CMMG's does have 1/8" twist (not sure about Sabre's). Unfortunately both have long lead times and are out of stock on these lesser-ordered profiles - I know, because I'm looking for one myself!!

Generally you want to use feed ramp setup on bbl extension that matches your receiver. (M4 extension should use M4 receiver; regular bbl extension should use regular receiver.) Using an M4 extension in a non-M4 upper receiver may work OK (though there's a 'dip' in ramp profile that a bullet tip might hang on); using a regular bbl extension in an M4 ramped receiver may well interfere with feeding as bullet tip can tangle on a ridge prominence.

Smaller bbl vendors of much-shorter-lifespan non-chrome-lined bbls may be able to supply you with one or the other bbl. Randall Rausch's AR15barrels.com provides non-chrome-lined bbls that are very accurate and I'm sure you could get your choice of extension for your receiver.

But you can always sell/trade your receiver for one with M4 ramps, don't get hung up on whose upper receiver you have, it's the barrel that does the work.

[Prc329]

The SPR is made for 1/7 but I think they do make a 1/8...look at CMMG which is chrome lined. Im going to use a Mega upper w/o any extentions yet the barrel has them.

The WOA barrels are rifle length gas systems but the Noveske ones are midlength as well as some others. The other stuff is whatever turns ya on.

You can get a WOA with a mid-length. Adco has them. They are stainless steel and in stock right now.

[Jicko]

bwiese:
are the *originals* 1:8 or 1:7.7?


mike452:
Compass Lake have Kreiger 1:7.7

http://www.compasslake.com/kreiger.htm;

these are the same one they used on Marines' SAM-R, those are also made by Compass Lake

I believed Compass Lake should also have 1:8 Douglas SS barrel too... u can get it fluted like the ones used in Army's SDMs.

"I don't have any special purpose except to shoot mostly 55 gr. and 62 gr. ammo." <- 1:7 or 1:8 works with those too..... OR you can get into reloading of 77grainers.... will cost like 20c to 25c a round... similar to today's XM193 prices...

BTW, what kind of SPR are you talking about building? A "Mark 12 Mod 0/1 SPR" or u are just using the term "SPR" to describe a generic "AR15-series rifle modified to provide increased accuracy over range"?

[cali-man]

I believe mine is a 1/7.5 or 1/7.7 - I can't remember. The barrel I have is a Noveske 16" Pac Nor SPR barrel. I know the original was an 18" but Noveske made a special run of 16" barrels. I am having trouble putting on a Larue Low Pro gas block. Can anybody help? I am in Fontana. Will drive 30 min. and pay in cash or ammo.

[Technical Ted]

M4 barrel extension in a non-M4 upper receiver isn't going to buy you anything. May as well go with a standard barrel extension if your upper receiver doesn't have the cuts.

[mike452]

I am using the term SPR to describe the external appearance of the rifle. To me it’s just a configuration sales gimmick. I don’t see any special purpose except for the cool factor.

I will look in to the price and accuracy trade-off of just getting a heavy fluted stainless or fluted chrome-lined instead of a SPR barrel.
I think a SPR barrel without the standard extension and 1:8 twist is what I should look for.
I will have to put a nice scope on it, so I won’t be spending that $250 for PRI sights.

cali-man: What problem are you having?

I wonder if I can send my upper and barrel to YHM for them to install the gas block, muzzle brake, and specter hand guard. Their web site does say they can install what they sell for free.

[cali-man]

I can get it half way on, and then its a no go. I put a decent amount of oil before attempting this. I already mangled a Larue gas block. Had to buy another. Its really a tight fit.

[xenophobe]

Ah so much for facts then.

I don't see why you're even asking what you are then. Just build it with whatever you want and call it a SPR.

[Jicko]

Ah so much for facts then.

I don't see why you're even asking what you are then. Just build it with whatever you want and call it a SPR.

I know... wasted my time for digging out accurate info for him....

[Prc329]

I can get it half way on, and then its a no go. I put a decent amount of oil before attempting this. I already mangled a Larue gas block. Had to buy another. Its really a tight fit.

I had to use a little CLP, a piece of thick rubber I had laying around, a large punch, hammer, a shot of tequila and a few words i hope my daughter did not hear to get me gas block on It is supposed to be really tight.

BTW, the only thing SPR about my build is the fact that it has a scope on it and an SPR profile barrel and a muzzle brake made by ops inc.

[mike452]

Sorry people! Didn't want to waste your time. I do want to build a SPR. Just some of the options are side tracking my thoughts.

I do want a "Mark 12 Mod 0/1 SPR", but willing to get copies instead of the original makers on the hand guard, receiver, and gas block.

I think I have what I need to start shopping! Thanks!

[Omega13device]

There's definitely no reason to go for "original" parts unless you've got a jones for being historically accurate.

With the Mod 0, some of the parts aren't even around and if they were you wouldn't want to use them anyway. The original PRI float tube was inferior to the current, third-generation tube, and the ARMS rail has been redesigned to accommodate the newer tube. And a lot of people forgo the Ops Inc muzzle brake due to the cost, instead using some other kind of brake or just a flash suppressor.

The Mod 1 originally used a KAC four-rail free float tube, if I remember correctly, but there's no advantage to using a KAC rail over LaRue, Daniel Defense, or whatever.

Here are some basic ingredients for each, anyone feel free to add anything I left out:

Mod 0
Upper receiver and bolt/carrier/charging handle of your choice (not sure what they used for the original)
18" SPR countour SS barrel with 1:7 twist (substitute: chrome-lined barrel, any other contour, any other twist)
Ops Inc muzzle brake (sub: any other brake or FH)
PRI gen 3 free float tube
ARMS #38 PEQ-2-3 Swan Sleeve
PRI flip-up front sight gas block (sub: YHM flip-up front sight gas block)
ARMS #40 BUIS (sub: any other BUIS)
Leupold Mark 4 3-9x36 MR/T M3 scope (sub: a cheaper scope)
ARMS #22 medium throw-lever rings (sub: cheaper rings)

Mod 1
Upper receiver and bolt/carrier/charging handle of your choice (not sure what they used for the original)
18" SPR countour SS barrel with 1:7 twist (substitute: chrome-lined barrel, any other contour, any other twist)
Ops Inc muzzle brake (sub: any other brake or FH)
12" four-rail free float forearm (many people use DD or LaRue, but you could sub YHM, MI, Samson, etc.)
KAC front and rear BUIS (sub: anything cheaper - ARMS, Troy, etc.)
LaRue SPR scope mount (sub: a cheaper scope mount)
Leupold Mark 4 3-9x36 MR/T M3 scope (sub: a cheaper scope)

For both I would also add a Harris bipod and appropriate bipod mount.