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MY MKA TAC-12 build


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After much anticipation, my TAC-12 lower finally made it's way home on Thursday. As a machinist and programmer, I can say this is a very nicely machined part. No chatter marks, funky edge breaks, engineering shortcuts or mediocre workmanship. A very nice component. The only thing I would note to FB is add some material to the top of the bosses that the bolt lock roll pin goes through. Scary thin in the event the pin needs to be removed for any reason.

 

My MKA is not the light weight it once was, but not that heavy either. Definitely a very solid gun without feeling awkward or overweight. I bought a Magpul CTR stock that was supposed to go on the MKA, but it wound up on my Daniel Defense M4v5 instead. If I don't like the Mako I'll get another CTR for the MKA and drop some weight in the process.

 

So far, my build consists of:

 

Pre XN MKA

FB TAC-12 lower with Ambi-Safety assembly

FB Handguard with charging handle, standard length

Tromix trigger with disconnector

FB Hammer

Salem6 gas piston

T&N Charger Handle

Primary Arms Micro Dot sight with UTG lower 1/3 co-witness riser

Magpul MOE +Grip

Magpul MBUS front & rear sights

Magpul Angled Fore-Grip

Magpul Rail Sling Attachment

Noveske rear sling mount

Trulock Tactical Choke

Mako GL Shock stock

Vltor shotgun receiver extension

Thordsen Bilateral Magazine Lock

 

 

The next up is to install the Thordsen Bilateral Magazine Lock. This requires drilling and tapping. I need to get an electrician to install a subpanel in my garage and hook up my phase converter so I can get my mill and lathe up and running.

 

I'm also going to make a new magazine release/bullet button assembly. The stock one is a loose piece of garbage.

 

The stock needs to be drilled and pinned before I venture onto any public land out here.

 

The FB handguard needed some Dremel work to fit over the barrel extension. Apparently the extension diameter varied on earlier MKAs, and mine was one of the bigger ones.

 

The Vltor extension has a cap that screws off and on so you can use it for storage, but there is no way to reach it without removing the stock. I'll drill, tap and permanently attach a low or button head screw to the cap so I can just remove the stock pad and unscrew the cap with a short allen key.

 

I ran into the same issue others have with the bolt catch not engaging the bolt and did some minor filing. This did not help, and the TAC-12 lower exposes an issue with the factory MKA magazines. I'll make a separate post for this.

 

Now I need to get time off from work to go shooting.

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Edited by cad_man
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One other note, I did not use the safety detent FB included with the lower. Instead I bought a long nose spring plunger from McMaster, part# 84985A13. You don't need a plunger wrench like it says in the product description, it is slotted for a screw driver.

 

http://www.mcmaster.com/#catalog/119/3345/=mtovvl

 

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Will do. The Mako is a loose fit on the Vltor extension since its made to also fit commercial spec tubes. To fix that, I put a 1" wide strip of .022" thick UHMW tape along the top of the tube and a strip of PTFE tap in the receiver channel of the stock and that eliminated all but the slightest hint of wobble, and the stock still slides back & forth freely.

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One other note, I did not use the safety detent FB included with the lower. Instead I bought a long nose spring plunger from McMaster, part# 84985A13. You don't need a plunger wrench like it says in the product description, it is slotted for a screw driver.

 

http://www.mcmaster.com/#catalog/119/3345/=mtovvl

 

So does the safety feel positive when you change from S to F.No slop.

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Yes, a positive feel without any stiffness when moving out of the detents. With the longer nose you are able to preload the plunger without bottoming out the ball. Part # 84985A52 has a slightly higher spring rate.

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How much was shipping ?

One other note, I did not use the safety detent FB included with the lower. Instead I bought a long nose spring plunger from McMaster, part# 84985A13. You don't need a plunger wrench like it says in the product description, it is slotted for a screw driver.

 

http://www.mcmaster.com/#catalog/119/3345/=mtovvl

 

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  • 2 months later...

8 months after buying my MKA I finally get to shoot it.

 

I added a Magpul B.A.D. lever, swapped the Trulock Tactical Choke for the stock choke with three notches on it, and went with the Magpul MOE Fixed Carbine Stock.

 

Very very nice.
Let us know about the Mako GL

With the added weight of the FB lower and standard length handguard, the Mako GL was a little too heavy and had to go. It also loosened up a little just from pushing it in and out before I even shot the MKA, and I just couldn't get over that looseness. I like my firearms nice and solid. The Magpul MOE Fixed Carbine Stock it turns out is the perfect length and is rock solid.

 

The B.A.D. lever is a must. Releasing the bolt with the bolt catch alone was a bitch with some magazines. The leverage of the B.A.D. lever makes that a thing of the past.

 

Didn't get to shoot it until the tail end of our time at the range, so I only ran a couple boxes through it (Federal Power Shok rifled slugs, 1610 fps) with a factory 10 round magazine.

 

I had 2 FTEs, and when I got home I found I could twist the barrel side to side easily by hand. The retaining nut & the gas spring retainer came loose, so I'll chalk up the FTEs to that. The other rounds went boom and ejected just fine. I'm going to modify the retaining nut to prevent it from coming loose in the future.

 

All of my shots grouped to the lower left corner of the target and I'll contribute most of that to the barrel. The bore in the upper receiver is a loose fit for the barrel extension, and the barrel angles downward slightly because of it. When the gas spring retainer is tightened it pulls the barrel downward. I don't see any good fix for that other than see if RAAC will replace the upper. FB has posted pictures of their MKA upper and that may be the direction to go. Better machining and the slick receiver/handguard interface FTW.

 

The stock choke tube also worked loose. Dry firing would transmit shock through the barrel and the Trulock would become loose from that alone, so that's the reason for running the stock choke. But it looks like anything will work loose unless there is some sort of mechanical means to tighten it.

 

FTEs aside, the MKA is a blast to shoot with a nice bit of recoil to keep you honest. We where shooting at an indoor range and my wife said other shooters would walk by really slow behind me to check out what was making the kabooms versus their pops, and they would comment on the length of the 10 round magazine. There apparently are not many MKAs in California.

 

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Edited by cad_man
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Glad you are having fun. When mine was new (polymer lower and 5 rd magazines shooting 1300 fps loads) the recoil was quite noticeable but manageable. Add the weight of an aluminum lower, a 15 rd magazine and 1200 fps loads, it shoots like a dream. Instead of an AR, it hoists more like a Garand.

 

You mentioned the choke coming loose while dry firing. I'm still having problems with Carlson chokes coming loose after around 15 shots fired. Still looking for a cure since we occasionally have stages up to 30 rds.

 

Earlier I posted the question of whether dry firing the MKA 1919 was recommended or harmful to the gun. Has your dry firing been extensive and have any problems developed?

 

Thanks.

 

Bill

Edited by Flatland Shooter
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I'd say my dry firing hasn't been excessive, but at every step along the way of my build I rack & dry fire as part of function testing. Most of the dry firing was during magazine feed lip tuning, and that took a while to get the bolt open function working on all of my magazines. The ever loosening choke is the only issue I've seen, and it doesn't take many handle pulls to get it loose. The wall thickness of the barrel seems too thin to allow a threaded lock ring, so I'll probably just use a drop of high temp thread locker and call it a day.

 

This is my first and only shotgun. Are loose chokes an issue on other shotguns?

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I'd say my dry firing hasn't been excessive, but at every step along the way of my build I rack & dry fire as part of function testing. Most of the dry firing was during magazine feed lip tuning, and that took a while to get the bolt open function working on all of my magazines. The ever loosening choke is the only issue I've seen, and it doesn't take many handle pulls to get it loose. The wall thickness of the barrel seems too thin to allow a threaded lock ring, so I'll probably just use a drop of high temp thread locker and call it a day.

 

This is my first and only shotgun. Are loose chokes an issue on other shotguns?

 

On this and other forums, some folks have indicated they have problems keeping the chokes tight on these shotguns.

 

The MKA 1919 is the only gun I own that uses WinChokes. I have several Remingtons for hunting and two Browning O/U's for sporting clays that have all seen a lot of use without the chokes coming loose. I also have an after-market Hasting barrels that keeps the chokes tight.

 

I've heard from friends that some of the high end Beretta O/U's (Optima choke) will occasionally have problems. These are folks that shoot thousands of rounds each month. If they don't need to change out the chokes, some shooters have heated up the barrel with heated hair dryers and then tightened down the choke. That seems to work but you need to re-heat the barrel to remove the choke.

 

I use my MKA for 3 Gun and want to have the flexibility to change chokes if needed. Usually I have a "LM" in the gun but other chokes have their uses. That rules out LocTite for me.

 

I'm experimenting with different choke lubes to see if there might be one that grabs the threads a little better than the others.

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  • 1 month later...

Installed the Thordsen Bilateral magazine Lock. It was designed for ARs, but works on the MKA too.

 

I have the Thordsen Armorer's Kit for this which contains a couple jigs, but it only works for ARs. So I needed to measure the distance between the mounting holes, position the lock on the receiver to drill & tap the first hole, then move to the next location and finish the second hole. Then mark the location for a tapped hole on the magazine latch, remove it and drill & tap. The latch sticks above the FB receiver (don't remember if it did on the stock one), so it interfered with the lock. Milled .040" from the notch on the lock that sits over the latch and the lock functions perfectly.

 

The great thing about the lock is the actuating lever in it is drilled & tapped, so the gun can be taken out of California and you can install a button and use it as a normal magazine release. My wife and I have been talking about leaving here, and as soon as that happens the Bullet Buttons on all of our rifles are coming off as soon as we cross the California border.

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