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MK12 MOD-0 LETS SEE EM!
- Thread starter VJJPunisher
- Start date
here is mine..mostly to spec....
http://i172.photobucket.com/albums/...1-7868-463F-ACDE-7A22C9009F76_zpsjsmfqz0d.jpg
http://i172.photobucket.com/albums/...1-7868-463F-ACDE-7A22C9009F76_zpsjsmfqz0d.jpg
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can someone please help me post full size pics? I am about to punch a hole in the computer screen
Use the picture option above where you type a post, click the "From URL" tab if it's not already on that, and uncheck the "Reference locally" box if necessary.
Nice Mod 0!
Unless you're fixated on a full on spec build you can also consider the Larue Tactical Light Rail. That's what I went with and its been 100% Solid and Light Weight. Mine is a MK12 Mod 1 Inspired Build.
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I built the one shown in the top right corner of this Wikipedia page:
Mk 12 Special Purpose Rifle - Wikipedia, the free encyclopedia
That photogenic backdrop is my washed rock patio.
The funny thing is it's not a Mk 12 at all, but a 100% correct SPR upper in "pre-Mk 12" format. The lower was 100% what I liked, not Crane at all. Wikipedia of course never asked me what it was.
Mk 12 Special Purpose Rifle - Wikipedia, the free encyclopedia
That photogenic backdrop is my washed rock patio.
The funny thing is it's not a Mk 12 at all, but a 100% correct SPR upper in "pre-Mk 12" format. The lower was 100% what I liked, not Crane at all. Wikipedia of course never asked me what it was.
I've built my share of each format. Each has pluses and minuses. Plus, it gets hard to disassociate your judgement about the model in question from your feelings about the people that supplied the key components.
Mod 0:
The ARMS rear sight was almost as tall stowed as deployed, limiting how far aft the scope could be mounted.
The Swan SPR provides a means to mount any scope at the proper eye relief. Until they came out with that mediocre quality compact with special short eye relief from Leupold for the SPR Mk 12 series, this rail with conventional rings on top was the best solution to the eye relief issue. This rail also stiffened the receiver and the receiver-forend junction, giving in theory a potentially more accurate rifle. However, this theory was never proven, as there are so many other variables to the accuracy equation. This rail also weighs 12 ounces and is both expensive and hard to find. You'd better use blue Locktite on all the screws.
The PRI flip up front sight is a robust affair that could not be faulted except for perhaps its weight. But, it had such a big footprint that the barrel collar was limited in how far aft it could be placed. This in turn restricted the number of turns of thread engagement the Ops-Inc 12th Model could get on the muzzle brake. Making the barrel a quarter of an inch longer would have fixed this, but you aren't allowed to just do such things if you work for the government.
The ARMS #22 medium rings atop the rail have proven time and time again not to hold their tension. When I was an ARMS dealer, I learned that there was only a limited number of cycles to these devices before the scope would shift in the Picatinny rail slot under even the recoil of a 5.56mm. Some lasted longer than others, but eventual slippage seemed guaranteed.
The early, early version of the PRI SPR forend was a bit tedious to install. Lead shot under set screws?!? But, the later and final version is pretty much universally liked to this day. A number of SF Mod 1's were rebuilt with the PRI forend, I've learned. I myself always thought the round carbon fiber tube felt good in the hand.
Mod 1:
KAC's 600 meter micro rear sight is a mechanical work of art and stows quite low, but is this level of precision needed in a "back up" iron sight? This sight does not lock in the up position. The KAC folding front sight is slim, trim, fragile, and does not lock in the up position. Cute, though!
The KAC Long FF RAS forend was in my eyes that against which all forends were measured, at the time. It is not as easy to install as the Mod 0 PRI forend, due to the PRI's aluminum barrel nut being more forgiving than the KAC steel barrel nut. The KAC handguard nut will work loose if not put through multiple torque cycles first. I always applied a drop of Green Locktite as a final assurance against this.
The barrel collar location on the Mod 1 shared the same problem as the Mod 0, since of course it is a barrel from the same drawing.
The Mod 1 also shared the same issue with the ARMS #22 rings slipping. Later cantilever scope mount designs and better Nightforce compact scopes have solved the optic issues once and for all.
We had a dozen "real" Mk 12's made over ten years ago by the two contractors that built the majority of them for Crane. We used Young MFG bolt carrier groups, but all other components were from the same sources as specified by Crane. All met the same accuracy requirements. That was a learning experience.
The barrel is of course the key component in such a weapon. We've had a number of SPR barrels from Barnett, the original source, and countless more clones turned out from Compass Lake on Douglas, Krieger, and Lilja blanks. We are currently using a custom contour we jokingly call the "Mod 2" profile with rifle length gas system done by Noveske in a 1x8" three groove twist. CNC contoured, it weighs within a half ounce of the originals, but is stiffer. We use a 1" gas block seat precluding the use of the PRI front sight, giving us the room we need to slide the barrel collar a quarter inch aft, allowing three more full turns of thread engagement with the 12th Model suppressor on its host muzzle device. We've asked Noveske to use a Syrac adjustable gas block on our next batch.
It's a lot of fun to have an accurate clone of a Mk 12 of either format. But, to Paul and me, it's even more enjoyable to make a better one.
Mod 0:
The ARMS rear sight was almost as tall stowed as deployed, limiting how far aft the scope could be mounted.
The Swan SPR provides a means to mount any scope at the proper eye relief. Until they came out with that mediocre quality compact with special short eye relief from Leupold for the SPR Mk 12 series, this rail with conventional rings on top was the best solution to the eye relief issue. This rail also stiffened the receiver and the receiver-forend junction, giving in theory a potentially more accurate rifle. However, this theory was never proven, as there are so many other variables to the accuracy equation. This rail also weighs 12 ounces and is both expensive and hard to find. You'd better use blue Locktite on all the screws.
The PRI flip up front sight is a robust affair that could not be faulted except for perhaps its weight. But, it had such a big footprint that the barrel collar was limited in how far aft it could be placed. This in turn restricted the number of turns of thread engagement the Ops-Inc 12th Model could get on the muzzle brake. Making the barrel a quarter of an inch longer would have fixed this, but you aren't allowed to just do such things if you work for the government.
The ARMS #22 medium rings atop the rail have proven time and time again not to hold their tension. When I was an ARMS dealer, I learned that there was only a limited number of cycles to these devices before the scope would shift in the Picatinny rail slot under even the recoil of a 5.56mm. Some lasted longer than others, but eventual slippage seemed guaranteed.
The early, early version of the PRI SPR forend was a bit tedious to install. Lead shot under set screws?!? But, the later and final version is pretty much universally liked to this day. A number of SF Mod 1's were rebuilt with the PRI forend, I've learned. I myself always thought the round carbon fiber tube felt good in the hand.
Mod 1:
KAC's 600 meter micro rear sight is a mechanical work of art and stows quite low, but is this level of precision needed in a "back up" iron sight? This sight does not lock in the up position. The KAC folding front sight is slim, trim, fragile, and does not lock in the up position. Cute, though!
The KAC Long FF RAS forend was in my eyes that against which all forends were measured, at the time. It is not as easy to install as the Mod 0 PRI forend, due to the PRI's aluminum barrel nut being more forgiving than the KAC steel barrel nut. The KAC handguard nut will work loose if not put through multiple torque cycles first. I always applied a drop of Green Locktite as a final assurance against this.
The barrel collar location on the Mod 1 shared the same problem as the Mod 0, since of course it is a barrel from the same drawing.
The Mod 1 also shared the same issue with the ARMS #22 rings slipping. Later cantilever scope mount designs and better Nightforce compact scopes have solved the optic issues once and for all.
We had a dozen "real" Mk 12's made over ten years ago by the two contractors that built the majority of them for Crane. We used Young MFG bolt carrier groups, but all other components were from the same sources as specified by Crane. All met the same accuracy requirements. That was a learning experience.
The barrel is of course the key component in such a weapon. We've had a number of SPR barrels from Barnett, the original source, and countless more clones turned out from Compass Lake on Douglas, Krieger, and Lilja blanks. We are currently using a custom contour we jokingly call the "Mod 2" profile with rifle length gas system done by Noveske in a 1x8" three groove twist. CNC contoured, it weighs within a half ounce of the originals, but is stiffer. We use a 1" gas block seat precluding the use of the PRI front sight, giving us the room we need to slide the barrel collar a quarter inch aft, allowing three more full turns of thread engagement with the 12th Model suppressor on its host muzzle device. We've asked Noveske to use a Syrac adjustable gas block on our next batch.
It's a lot of fun to have an accurate clone of a Mk 12 of either format. But, to Paul and me, it's even more enjoyable to make a better one.
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WOW...Learning something New Every Day! That is some Great In Depth write up on Both MK12 models. I always enjoyed all your posts and Especially the Rifle Picture ones!
A quick question sir. How is the Collar attached to the Barrel Section after the Ops Break? Also can you tell me the Barrel Dim at the Collar as well? Eventually I would like to get a set from BCM to put one on my current SPR as well.
Thanks in advance and also Great Post Sir!
Cheers
HOG
A quick question sir. How is the Collar attached to the Barrel Section after the Ops Break? Also can you tell me the Barrel Dim at the Collar as well? Eventually I would like to get a set from BCM to put one on my current SPR as well.
Thanks in advance and also Great Post Sir!
Cheers
HOG
The barrel collar has an internal step in it. This step abuts a shoulder contoured into the barrel. The collar is secured at this point with a super dinky set screw, but I have found that when the barrel heats up, the set screw is often not sufficient to keep the collar in place. That's why I also add a generous dose of red Locktite under the barrel collar. Woe be unto whoever has to remove it!
The location of this shoulder and dimensions of the barrel at this point can vary greatly, based upon the application intended. There are also all sorts of barrel collars out there of different dimensions for the different Ops-Inc suppressors.
But, I do have a drawing for the SPR barrel from Mr Phil Seeberger himself, dated 2002. The step in the barrel, going forward from the gas block toward the muzzle, is 0.7495" down to 0.725". In the Ops-Inc drawing, this step is 2.27" from the actual end of the barrel.
We have moved this step aft 0.25" in our custom Noveske SPR "Mod 2" barrel contour, to allow three more complete turns of thread engagement with the suppressor on the muzzle device.
Thanks for the Detailed Response Sir! But based on your information it doesn't look like I'll be able to use my current barrel with the OPS Break/Collar setup. In that case I'll hold off a bit and hopefully find more time and ammo to shoot out my current barrel first. Its not the spec barrel profile but this Walther Lother barrel still shoots like a dream for me. Thanks again!
"Shoots like a dream for me"?!? What could possibly be better than that?
You can always have a custom collar fabricated and a step contoured into your present barrel to accept the Ops-Inc 12th Model suppressor. No one would be better for this task, I would not think, than Ron Allen, himself, the guy that builds Seeberger's suppressors.
Personally, I feel the same way about my own precision AR' uppers. I currently don't even have a precision 18" rig, but I've got one in the works.
I do have a 14.5":
And a 16":
The 18" I have planned will have our custom Noveske SPR "Mod 2" barrel with 1x8 three groove and rifle length gas system, Ionbond Diamondblack coated (gas tube, too). LMT proof round tested, MP-inspected bolt, D/B coated down to the gas rings, fitted at precisely 1.4646". Young MFG National Match carrier, first forged, then centerless ground, then hard chromed, and THEN D/B coated, along with the LMT internals. PRI Gas Buster, of course, for suppressed use. Surefire MB556 for SOCOM can that is bound to get here some day.
I have a couple of scopes I'll alternate on it to see what suits me better. The logical choice for any precision AR' is the new Nightforce 2.5-10x42 NXS. But, I have an older spare NF 5.5-22x50 NXS that despite its size and weight is a real luxury for old eyes. Who cares if the rig ends up looking like a scope with a little rifle under it?!?
The lower will be a Vltor with A5 recoil system and H1 buffer; Geissele SSA-E trigger; SPR pistol grip: and prototype fixed stock being worked up by R&R.
I'm undecided on the "chassis", the receiver/forend. While I'm pretty excited about the Vltor VIS-3 in KeyMod format, I think I want a longer forend than 12". So, a Vltor MUR with forward assist and one of the following forends: Noveske NSR; KAC URX 4; Geissele Mk 4; KAC URX 3.1; PRI carbon fiber Competition forend in natural finish; or maybe a Seekins IRMT3 upper with SP3R forend???
As always you build some Beautiful Rifles. If you don't mind me asking, what rails are on these two rigs? It seems like the slim design and the key mod option are all the new Craze these days! How much do these two weight in without the can? Is it really that much better than the quad rail designs? Thanks!
Personally, I feel the same way about my own precision AR' uppers. I currently don't even have a precision 18" rig, but I've got one in the works.
I do have a 14.5":
And a 16":
The 18" I have planned will have our custom Noveske SPR "Mod 2" barrel with 1x8 three groove and rifle length gas system, Ionbond Diamondblack coated (gas tube, too). LMT proof round tested, MP-inspected bolt, D/B coated down to the gas rings, fitted at precisely 1.4646". Young MFG National Match carrier, first forged, then centerless ground, then hard chromed, and THEN D/B coated, along with the LMT internals. PRI Gas Buster, of course, for suppressed use. Surefire MB556 for SOCOM can that is bound to get here some day.
I have a couple of scopes I'll alternate on it to see what suits me better. The logical choice for any precision AR' is the new Nightforce 2.5-10x42 NXS. But, I have an older spare NF 5.5-22x50 NXS that despite its size and weight is a real luxury for old eyes. Who cares if the rig ends up looking like a scope with a little rifle under it?!?
The lower will be a Vltor with A5 recoil system and H1 buffer; Geissele SSA-E trigger; SPR pistol grip: and prototype fixed stock being worked up by R&R.
I'm undecided on the "chassis", the receiver/forend. While I'm pretty excited about the Vltor VIS-3 in KeyMod format, I think I want a longer forend than 12". So, a Vltor MUR with forward assist and one of the following forends: Noveske NSR; KAC URX 4; Geissele Mk 4; KAC URX 3.1; PRI carbon fiber Competition forend in natural finish; or maybe a Seekins IRMT3 upper with SP3R forend???
Seekins SP3R (12")on the 14.5" and Knight's URX 3.1 (13.5") on the 16". Both weigh approx 12 ounces.
MSTN
"The 18" I have planned will have our custom Noveske SPR "Mod 2" barrel with 1x8 three groove and rifle length gas system, Ionbond Diamondblack coated (gas tube, too). LMT proof round tested, MP-inspected bolt, D/B coated down to the gas rings, fitted at precisely 1.4646". Young MFG National Match carrier, first forged, then centerless ground, then hard chromed, and THEN D/B coated, along with the LMT internals. PRI Gas Buster, of course, for suppressed use. Surefire MB556 for SOCOM can that is bound to get here some day."
What would the weight of this rifle be without optics???
"The 18" I have planned will have our custom Noveske SPR "Mod 2" barrel with 1x8 three groove and rifle length gas system, Ionbond Diamondblack coated (gas tube, too). LMT proof round tested, MP-inspected bolt, D/B coated down to the gas rings, fitted at precisely 1.4646". Young MFG National Match carrier, first forged, then centerless ground, then hard chromed, and THEN D/B coated, along with the LMT internals. PRI Gas Buster, of course, for suppressed use. Surefire MB556 for SOCOM can that is bound to get here some day."
What would the weight of this rifle be without optics???
That looks like A LOT OF Scope for that rifle! It might look less Bulky without the Sun Shade I think. I got two of those Bushnells with the G2 Rets and Loves them! Nice Rig Sir!
The stock PRI Mod 0 upper is solid though I'm still not sold on the HDMR.
My MK12 Mod O Clonish. Using Black Hills Red box 77 grain .223 loads I was able to get these groups.
5-1/8'' group at 800 yds - 8.9 mils of elevation.
3-1/2'' group at 600 yds - 5.2 mils of elevation.
Used an Accuracy First Wiz Wheel. I am right at sea level.
5-1/8'' group at 800 yds - 8.9 mils of elevation.
3-1/2'' group at 600 yds - 5.2 mils of elevation.
Used an Accuracy First Wiz Wheel. I am right at sea level.
Here is my Mk 12 Mod Merle rifle I recently put together:
I used a Daniel Defense rail instead of KAC and a Vltor upper. The parts that matter most are up to standards like the Centurion Mk 12 barrel and the KAC 2 stage trigger.
I used a Daniel Defense rail instead of KAC and a Vltor upper. The parts that matter most are up to standards like the Centurion Mk 12 barrel and the KAC 2 stage trigger.
18" Krieger with SF break. I had the NF modified with their new Mil-R reticle and used it to nail 40% IPSIC's out to 740 yards.
<a href="http://s22.photobucket.com/user/georgemac/media/MIL-R_zpsa9b7eb21.png.html" target="_blank"><img src="http://i22.photobucket.com/albums/b328/georgemac/MIL-R_zpsa9b7eb21.png" border="0" alt=" photo MIL-R_zpsa9b7eb21.png"/></a>
<a href="http://s22.photobucket.com/user/georgemac/media/MIL-R_zpsa9b7eb21.png.html" target="_blank"><img src="http://i22.photobucket.com/albums/b328/georgemac/MIL-R_zpsa9b7eb21.png" border="0" alt=" photo MIL-R_zpsa9b7eb21.png"/></a>
Love that reticle. I'm thinkin about going over board and putting a 5-25x56 atacr on my mk12 and using it as a quasi spotting scope.
18" Krieger with SF break. I had the NF modified with their new Mil-R reticle and used it to nail 40% IPSIC's out to 740 yards.
<a href="http://s22.photobucket.com/user/georgemac/media/MIL-R_zpsa9b7eb21.png.html" target="_blank"><img src="http://i22.photobucket.com/albums/b328/georgemac/MIL-R_zpsa9b7eb21.png" border="0" alt=" photo MIL-R_zpsa9b7eb21.png"/></a>
What bcg are you running in that thing
I have a Youngs chromed BCG in a Colt M4 upper with the PRS charging handle. The barrel is a 1/7.7 with a Wylde chamber and it loves the 77's.
SH MK12 MOD0 HCS Built
Amazing how long some of these builds can take when compiling certain parts one feels nothing else will do. Still a bit more to do with it on the optic and muffler front.
Amazing how long some of these builds can take when compiling certain parts one feels nothing else will do. Still a bit more to do with it on the optic and muffler front.
Doh, thanks! Fixed 'em.
Billet SH MK12 Mod0
High Caliber Sales Built
16” Douglas stainless barrel 1:7 twist with OPS INC collar and brake
Battle Arms Development BAD-A ambi selector fitted with Short left and end plate right (non-ambi)
PRI Gen III fore end, PRI gas block/front site, #40 standalone ARMS rear site, PRI’s SPR-PEQ sleeve
Larue LT706 Atlas V-8 Bipod
Area53 SH Edition Billet Lower
Spikes Tactical Gen II Upper
LMT Machine Enchanced bolt carrier group
Sierra Precision Grip
V7 Weapons systems: Ti Gas Tube, Ejection port door, port door pin, light catch, titanium take down pins unfinished, titanium grip screw
Seekins Precision Catch Button, enhanced latch
KAC 2 Stage Trigger
MagPul UBR buttstock with MagPul Strike Plate and Modular Driven Technology Adjustable but pad
Fortis Rail Attachment Point
Magpul Flat Foliage Green Cerakote
KNS Anti-rotate pin set Gen
Badger Ordnance Tactical Charging latch Gen I
Tactical Springs LLC White H2 Buffer
BlueForce Gear Padded two point sling
Damage Industries Quick Detach Sling Swivels Unfinished, Cerakoted
Colt Small Parts Kit
Cerakote on all but lower by Spectrum
AEM5 suppressor pending
Billet SH MK12 Mod0
High Caliber Sales Built
16” Douglas stainless barrel 1:7 twist with OPS INC collar and brake
Battle Arms Development BAD-A ambi selector fitted with Short left and end plate right (non-ambi)
PRI Gen III fore end, PRI gas block/front site, #40 standalone ARMS rear site, PRI’s SPR-PEQ sleeve
Larue LT706 Atlas V-8 Bipod
Area53 SH Edition Billet Lower
Spikes Tactical Gen II Upper
LMT Machine Enchanced bolt carrier group
Sierra Precision Grip
V7 Weapons systems: Ti Gas Tube, Ejection port door, port door pin, light catch, titanium take down pins unfinished, titanium grip screw
Seekins Precision Catch Button, enhanced latch
KAC 2 Stage Trigger
MagPul UBR buttstock with MagPul Strike Plate and Modular Driven Technology Adjustable but pad
Fortis Rail Attachment Point
Magpul Flat Foliage Green Cerakote
KNS Anti-rotate pin set Gen
Badger Ordnance Tactical Charging latch Gen I
Tactical Springs LLC White H2 Buffer
BlueForce Gear Padded two point sling
Damage Industries Quick Detach Sling Swivels Unfinished, Cerakoted
Colt Small Parts Kit
Cerakote on all but lower by Spectrum
AEM5 suppressor pending
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Amazing how long some of these builds can take when compiling certain parts one feels nothing else will do. Still a bit more to do with it on the optic and muffler front.
What butt stock is that?
John 15:13
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