KMW M.A.C.S. KIT

[blksno]

So, a month or so ago, Terry Cross posted that he had some remaining MACS kits to be sold as is, with surplus parts and limited "build instructions"
I noticed John at 8541 Tactical shared the post and I decided...what the hell. The hardware alone is worth more than the cost of the kit...so lets give it a shot.

KMW MACS KIT

Since this was clearly sold as a project kit...I wanted to avoid the nonstop string of emails to him that this could have turned into.
I was wondering if anyone else picked one up, or would like share build tips, tricks or even just pictures of what you have, or what you've done.

Slow day at work so I'm going to start the post off now, but when I get home, I'll get some info put together on what I have, plans and pictures of what you may encounter if you decide to pick up one of his kits. Hopefully he'll contribute a little along the way.

The 3 color Desert kit is the one I grabbed, so we will see how it goes.

 

[WillHugh]

I just saw he had these posted - definitely interested to see if anyone has built one.

 

[blksno]

Since this baby is gonna get fresh paint at some point and minor tweaks to the grip area...I'm not concerned about the finish. Did some measurements, did some fitment tests and I'll pick up a fresh 1" boring bit for the hinge to go into the stock.
Looks like the original design was to have some kind of pin, or rod go through the top of the stock (it had a centered mark that corresponds to where the hinge hole will be). That way it'll be permanent and not have any way to slip out. I'm trying to decide if I will use a threaded bolt, or a smooth rod to hold it. Either way, it shouldn't go anywhere.

The tape and tags on the stock are pushing 10 years old, so it was a chore getting it off...but a little break cleaner did the trick.

Here you see the mark that came. The center point and depth perfectly lines up with where the hole in the hinge pin sits.

I took some measurements, and squared up where the hinge pin will fit. just need a fresh 1" boring bit.

 

[WillHugh]

Aside from opening up a slot for the hinge, it appears most of the milling work is done on the stock?

 

[blksno]

Aside from opening up a slot for the hinge, it appears most of the milling work is done on the stock?

to make a functioning rifle...yes.

The "Dog Bone" is a small internal mounting block that allows the pic rails to be bomb proof. That will need inlet 1:1 or bedded into place so the side rails fit where they were meant to. Doesn't look too terribly difficult.
Not sure if the mini-chassis should be skim bedded into the stock or not. I probably will since it's such a small task. It's got about 1/16th of play as it comes...but the hinge and mini-chassis form a cohesive unit that's pretty solid.
The stock itself is inlet for the loggerhead hardware, but the cheek piece is not.

 

[blksno]

Took a little time off to grab some tools and get a plan laid out and some pieces ordered.
Might have a photo ejaculation here, so I may break it into a couple posts.

Picked up a couple new spade bits and went to work on the butt. a 1" spade bit on the horizontal to accept the male end of the folding hinge. The pointy end of the spade will end up coming out the back where the cheek piece mounts to the loggerhead hardware, but it's going to be filled, and repainted anyway, so no worries.

The top hole ended up being a wee bit off kilter but it's going to be filled in anyway, so I opened it up for perfect fit between the two stock pieces and the hinge.

With the front piece of the hinge installed...I set the mini-chassis into the stock to hold the hinge tight, in place, and square to the mini-chassis.
With the front locked in place...I simply push the butt stock forward until the bottom of the thumb hole has perfect alignment. This sets the top holes alignment with the hole at the rear of the hinge. It's a 1/2" hole, so for the time being...I'm just going to hold it in place with a 1/2" carriage bolt. Everything will be bedded into place at some point, but for now...i just want a loose fit.

 

[blksno]

The butt was pretty strait forward and the easiest to get going. The butt pad set up is not included, so if you're buying the MACS, you might as well pick up a butt pad system at the same time. It's a perfect fit.

I started with holding the plate in place with some gorilla tape, and marking my holes.

I gave them a small pilot hole before I took the plate off to drill, but the bottom hole needed a little larger pilot. It's right on the stocks seem and as I started to screw in the last screw, I heard a faint crack. Didn't see anything that split, but I drilled a little larger and will fill it with epoxy and screw in when I go to complete final installation. Be careful with the bottom, middle hole.

Once I had the plate fixed to the butt...I realized there are two lengths of mounting screws, depending on how many spacers you use...so I drilled out behind the threaded holes so if I eventually need to take a spacer out...I won't have to worry about the bolts bottoming out. They have a nice little pocket to sink into.

Perfect fit...
I only have one threaded Grovtec flush cup on hand, but I have a dozen on order. Lets get them started.

Small pilot hole to make sure it's centered.

Drilled 1/2 inch hole slowly from each side till they met in the middle. Ran my tap in nice and slow from each side.
Once I get them all installed, I will fill the void, lock the threads in place and run the fill up to the edge so they are nice and smooth.

 

[blksno]

The dog bone was a little more work, but should be relatively easy as soon as I pick up some screws from the hardware store.
The plan is to lay out where the rails will go, secure them with tape. Mark the holes on both sides drill a pilot hole.
Once I know where the screws will go through the stock itself...I will know the precise location and depth of the dog bone in the stock.
Clean out an oversized pocket, open up the side rail holes if necessary, attach the rails to the dog bone and bed it in place. Remove the rails, and fill in the side holes if they were opened excessively.

Side holes are marked and drilled.

Dog bone is in place. Dropped the barreled action on top to make sure she is deep enough.

I'm probably going to end up bedding this with a couple layers of tape so it will pop out easier once it's bedded. It's unlikely I will ever have anything mounted on these rails.

Still not sure if I'm going to buy the MUNSter NV mount whenever it's back in stock, or if I will use t -nuts. The rail up front sits flush like the side rails do...which means (in theory) you could run an ARCA over the TOP of the picatinny rail and it would still be flush with the stock.
Or i may simply sand down that little nub at the rear, fill the void up front and make it flat for an ARCA. Time will tell.

 

[Jester308]

That stock is glorious!! Im a sucker for a nice thumbhole and a folder to boot!

 

[blksno]

Anyone have ideas on how to keep it in the open position??
I thought about reaching out to Manners but haven't yet.
Neodymium magnets were another idea but I don't really want to bed one in the hand guard and the butt to make them hold...and I'm betting it would need to be pretty big.

 

[blksno]

Picked up some 1" long screws for mounting the rails to the dog bone. they fit absolutely perfect, but you can get by with 3/4". Don't remember the thread pitch off the top of my head.
I put a layer of gorilla tape around the middle hole of the dog bone to keep it empty, greased the sides and bottom, and filled the north/south screw holes with a grease soaked q-tip to keep the epoxy out and let me thread in a screw later to help pop the dog bone out (worked perfect)

I put a small layer of epoxy in the bottom, let the dog bone "float" a little and squeeze excess out around the edges. Then I threaded the pic rails in from the sides, got them centered in place, and torqued them snuggly where they were suppose to be. Then started to fill-er up.
It's not pretty, but lets be honest. I'm not a gunsmith and this will be under the barrel anyway.

I popped it out after it was a bout 2/3 cured so it could fully cure over night with a little more air flow.
This morning after it was fully cured to a sandable hard, I used a 1" dowel, wrapped in 60 grit sand paper to knock down the high edges .
You can see where I didn't quite have it full, but it's good enough for who it's for. It's rock solid.

Torqued in place. Perfect.

Here you can see how the rails are "flush" with the stock lines by design. Prevents chewing up your hands and snagging on things.
Will make sliding into an Eberlestock Pack MUCH easier.

 

[BOISCOID]

This is so awesome.

 

[GUNNER75]

Nice work. Bought the same kit. Hope to start on mine next week.

 

[blksno]

Nice work. Bought the same kit. Hope to start on mine next week.

Hopefully we can brainstorm and come up with a suitable spring system and a way to lock the stock open instead of floppy flop style.

Sent a message asking about the MUNSTer NV mount. Waiting for a reply

 

[Waorani]

Sent a message asking about the MUNSTer NV mount. Waiting for a reply

He's got some coming in around Dec 14 or so. Asked before I got what looks like might have been last set w/ NV inlet.

 

[GUNNER75]

I sent that folding unit of mine to my partner machine shop. They have been working with some specialty springs for similar working components outside the firearm industry. Hope they nail it soon. Told them I'd take 50 or 100. Figured I'd set a few aside and send the rest to Terry.
I got lucky and snagged a MUNSter last Thurs/Friday in the for sale section.

c_bass16, curious on your thoughts on bedding up the chassis to stock. (prep, material used, etc) I've been bedding stuff for 20 years. Darn sure want to nail this one the first time. LOL

 

[Steel head]

Looking forward to finished pics, looks awesome.

 

[blksno]

I sent that folding unit of mine to my partner machine shop. They have been working with some specialty springs for similar working components outside the firearm industry. Hope they nail it soon. Told them I'd take 50 or 100. Figured I'd set a few aside and send the rest to Terry.
I got lucky and snagged a MUNSter last Thurs/Friday in the for sale section.

c_bass16, curious on your thoughts on bedding up the chassis to stock. (prep, material used, etc) I've been bedding stuff for 20 years. Darn sure want to nail this one the first time. LOL

If you find a spring system to work solid, I'd be down. The one I have in right now is far from acceptable...but it works. The small c-type washer that holds the whole thing together is a SERIOUS weak point IMO. Not sure how to fix that just yet.

Im worse than amateur at bedding, so I'll get it all assembled and shoot it first. It's a pretty good fit, but I'm sure it will need something.

 

[blksno]

It's getting close enough to see the end, but I'm going to need to...
1. Wait for loggerhead hardware, or use something different...
2. Wait for the MUNSTer (should be in stock any day now.
3. Finalize the bond from the hinge to the butt
(Need to source a brass bushing to press fit into the hinge linkage to reduce slop)
3a. Decide if I'm going to follow through with having it fold to the right and cover the bolt.

 

[Waorani]

Anyone come up with a spring yet? Based on measurements this one looks like a possibility but I'm not sure about strength. Don't have anything else I need from McM right now or I'd just order some. Not room for much of a spring in there.

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

 

[blksno]

Anyone come up with a spring yet? Based on measurements this one looks like a possibility but I'm not sure about strength. Don't have anything else I need from McM right now or I'd just order some. Not room for much of a spring in there.

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

I'll try to get a picture tonight of the one I'm using. Tension is good, but I had to cut it in half.
I just took my hinge to the hardware store and found a spring that fit.

The real issue for me will be finding a bushing that allows a solid lock up and reduces slop when folded. The hinge pin itself appears to have an OD of .249" (I'm going of memory) and the hinge has in ID of about .270" or something like that. Both parts of the hinge have an oversized ID, which multiplies the slop after the stock is attached. It's a heavy butt, so when its folded...its going to flop all over without a bushing.

Also, I'm still not convinced that little C clamp that retains the pin is going to survive. I've thought about threading that pin put a cap bolt on...or even having a precision turned hinge pin made a little longer,but with the precise dimensions to fit the hinge itself.
If you look in the pictures Terry has...he has some kind of brass/nylon bolt on it as well.

 

[Waorani]

Went ahead and got the springs. I wanted flat/ground ends and seems to be strong enough but hard to tell w/o stock mounted plus it binds given slop in the pin. There's about .035" of difference in the pin vs hole diameters so definitely going to need some type of bushing but that takes away even more room for the spring. Also got some e-clips that work but I think just a hair too thick. I'm not a Dremel kind of guy but I think in this case that might be the easiest way to knock off a little on the undersides of the tabs. I'll mess with a bushing soon, just not ready to give up on that pin.

 

[GUNNER75]

My spring option has been put on hold due to the parent job they were working on. Was hoping to have mine complete by this weekend but I'm afraid it might be another week or two. The "dog bone" for the rail connection: I hope to have this on the CNC for a quick minute or two inlet. If I get that up I'll likely work out the Cheek Piece inlet as well. Couple minutes on each and it's right on the money.

 

[Waorani]

Stumbled across a piece of small diameter aluminum tubing so played around on the lathe and made a simple bushing. Aluminum is probably not the best material, and I'll eventually remake, but it completely eliminated the slop/binding. If you're building one of these, you're definitely going to have to make a bushing.

ID - .250
OD at spring - determined by spring ID - mine spring = .273 so I went w/ .271
OD below clip in top part of housing - .281
length - .875

 

[Waorani]

Made another bushing out of bearing bronze and refined the measurements a bit. Only other bushing option I can think of would be a press fit in the upper hole below retaining clip just the thickness of that piece and not extending underneath the spring. That would give room for a little extra spring wire diameter/strength but since I haven't found one I'm sticking with the spring I've got for now. The e-clip seems to be working fine w/o any grinding and takes some work to get off so I think that's going to be fine. Speaking of which, I've got a bunch of the e-clips and a few of the springs I'm using if anyone wants to try them. Just PM me.

 

[blksno]

Got my Loggerhead and MUNSTer parts in today.
Got the loggerhead bedded. Will pop it out tomorrow.
Need to grab some screws for the MUNSTer tomorrow.
Filled a couple voids with epoxy and I. Mapping out a plan to keep the stock folded. It's going to be loosely based on the Christensen Arms folding lock up.

 

[blksno]

Well. For a test fit, I've got the RimX mounted and ready for a test run this weekend. Have a 22NRL match Sunday. Not ideal to take an unverified weapon system...but fuck it.

I did notice while trying to install my TL3...that my heavy profile pipes (MTU) DO NOT clear the inside of the MUNSTer.
Pretty sure my RimX is an M24/M40 and it just barely fits.

Last thing to do mechanically is drill the hole for the tension screw on the Loggerhead...but I have a different plan for that I need to plan out first.

 

[winniethepooh]

“But fuck it” awesome build so far

 

[blksno]

decided to fold the stock to the right, but abandon the plan to have it fold over the bolt. Could have made it work by choosing different cheek hardware....but decided to stick with the loggerhead. I had planned to mill out a pocket for the bolt to fit...but the rearward post of the cheekpiece is in the same place.

Had i chosen a different piece of hardware, I could have chosen an option with a single middle post, or even an adjustable middle post with a front post for stability...leaving the rear available for a pocket. I figured I'd just leave it with full KMW hardware, and since the only time it will be folded...it will be vertical in a stock pack, i should still be fine with having the bolt open, as gravity will keep it forward.

You may have seen, at the rear of the right side, there's a 3/8 hex bolt threaded and epoxied into the stock. When folded...it locks on to a "Steelie" magnet mount for cell phones that's up front. Low profile, and relatively secure. If I shake it hard...it'll pop loose but as i said. It's only gonna be folded when it's in a stock pack.

 

[blksno]

Cerakote the hardware a tan color???

 

[GUNNER75]

No opinion on the hardware. Probably gonna leave mine as is.

Hats off to ya for getting me motivated. Started on mine just a hour ago. Been wanting to, just been too busy. Gonna try and knock it out over the next couple days.

 

[GUNNER75]

C_bass16. Quick question for you. How did you get past the inlet on the cheek piece. Stock side not cheek piece side. Mine was inlet already however when I drop the loggerhead unit in, the tension hole is lower than where the loggerhead is......

Appears as you filled your RH side in........on the stock.


I am folding to the left. Had to machine .050" off the folding arm that meets the bedding block to get the bedding block to set almost true. Left a little for crush and contact.

 

[blksno]

For the tension unit holes on the sides...I filled BOTH them in, as I didnt like the recessed position. It was originally set up for a big ass wheel that isn't used anymore. I'm planning to use a throw lever, on the LEFT side, set into the stock so its flush. The tension hole for me is very close elevation wise, but its off 1/8 to 3/16 front to back. Thats why you see the little lines and dot in red sharpie on the pic when it's folded
(Imagine something like this...as the plan anyway)

As for the hinge...i just put the bottom metal on...and torqued it all together once or twice with the action installed to "force" the mini-chassis to seat everything together. it was VERY tight.
I'd have to see a picture to see what you're issue was.

 

[GUNNER75]

Loggerhead hole is about .350" too high or inletting is high in the buttstock. Gonna check my other KMW this evening and see where the lower unit is positioned. I could maybe drill another hole and make it work.

When I installed a barreled action, my action was slightly nose diving in the stock. Maybe this is correct and I screwed myself as maybe bedding kept the front of the bedding system elevated, but I did what I did, so I'll adjust to that. I machined off about .045 to .050" surface, bolted up action, and it was true to bore line.

I didn't invent the beast, but I can see where minor adjustments might need to be made in assembly. Overall, everything is going together quickly.

I need to machine the dog bone and drill, drill 1" in folder, and mine is pretty much together. I did go about .020" wide on the Cheek Piece and slightly broke through to the finger groves in it. (Know a guy that can fix it so I'm not too worried).
I was shooting for a clean install, but this little goof........not so much. HA

 

[GUNNER75]

oops!

 

[blksno]

oops!

no biggie on that lol. I am actually thinking about filling mine in so they are flush

 

[GUNNER75]

Well, everything is up and going with the exception of bonding. The extension into the buttstock portion is tight enough I might shoot it a little this weekend just to ensure everything is 100%.

I used a .2" tall, .375" ID bushing for the folder (non folding at the moment) until I can come up with a spring.

I kept loosing hardware for a few of the components. #1 dog bone, used 10-24x1.25" FHSCS on the sides and bottom. #2 the Loggerhead I had in stock. (no big deal, # 8x1" SaberDrive wood screws to hold in place)

With the exception of the cheek piece blowout, I'd likely bond and run it. Might anyway, but maybe I'll work up some special finish for this one.

Edit: I used a 1" Forester Bit on the buttstock. Slightly undersized and super tight fit. Worked out slick. 1.5" depth.
I went with .4" depth on the dogbone. That is after I predrilled holes for the side rails. Once side rails were set I used the dog bone to spot drill for the bottom rail that will be used on a tripod (might change out for ARCA).

 

[SilentArms]

Hello all! My name is Kevin Harris and I'm the President of SilentArms located in Wendell, NC. Yup, it's a small town you may have never heard of! At any rate, I was presented with an opportunity to build one of these KMW M.A.C.S. kits and I wanted to post the details to the forum in case anyone might be interested. I'd like to thank Gray Sloan of Swift Creek Rifles for letting me do the work. If anyone else has any questions- just let me know!

P.S. - As a brand new member (and just receiving the rules for this forum) please let me know if any of this is a violation. I am not trying to sell anything. I'm just using this post to show how I went about this build. Hopefully it helps one of you guys out!

 

[blksno]

beautiful!!!
As much fun as it was to do mine from scratch...I probably would have just paid for the work to be done for me.
Very nice.

 

[cav1993]

Wownicely done gents!!

 

[SilentArms]

Just to shoot out an update since I've been quiet on here for awhile...

Here's a look at the last 3 of these KMW M.A.C.S kits I've processed through my shop!

 

[blksno]

Switched a couple things up.
The Gen3 razor is too long to use tenebrex caps with the MUNSTER. Probably gonna use the Vudu 5-25 on this one.
18" 22 creed for predators

 

[Mike_in_FL]

The Gen3 razor is too long to use tenebrex caps with the MUNSTER. Probably gonna use the Vudu 5-25 on this one.


View attachment 7814793

As dumb as this may seem to you, why not just use taller rings? You have an adj. cheekpiece, I'm a curious kind of guy (Seinfeld) so just asking. Or is this the height of a clip-on determining ring height?

 

[blksno]

As dumb as this may seem to you, why not just use taller rings? You have an adj. cheekpiece, I'm a curious kind of guy (Seinfeld) so just asking. Or is this the height of a clip-on determining ring height?

I hate. HATE using rings that are taller than necessary.
The Vudu us currently in an ARC M10 QD-L and it's just higher than I want. I'll sell it, take the loss, and buy rings that are better suited for the 50mm obj