Magpul AFG & Troy TRX Extreme - Direct Connect Mod

[KingsideRook]

I like my AFG - I like how it positions my arm and wrist while shooting. However, nothing's perfect, the AFG included. When I first tested it, I found the surface to be too slick for my liking, and it let my hand slip off the back end of the AFG. I decided to rough-stipple the entire underside using a soldering iron. The result was very grippy and rough.

http://i90.photobucket.com/albums/k267/Juggernaut45/hg1.jpg

This AFG was previously mounted on a DD Omega X 12.0 FSP rail, and it fit nicely. I have large hands, so even with a compliment of full profile rail covers, the AFG felt right at home on that rail. The only real complaint I had was the weight.

Enter my new upper, constructed with a midlength gas CHF barrel, and an 11" Troy TRX Extreme rail. Everything about the Troy rail is great so far - I like the clean feel, the ridiculously low weight, the modularity.

When placing a rail for the AFG on the bottom of the TRX, I found that the additional thickness of the rail, combined with the thickness of the AFG, broke up the comfortable feel of the Troy rail. It didn't feel "round" anymore, and the easy, thumb-high grip I'd had with the DD rail had become a bit of a stretch with the AFg on the bottom of the TRX. Even worse, it was close, very close to being right - I just had to reduce the distance between the body of the TRX, and the underside of the AFG by about .25". If you look at it in this "before" picture, it's pretty apparent how much offset there is between AFG and rail:

http://i90.photobucket.com/albums/k267/Juggernaut45/DSC_6802-1.jpg

So I set about engineering a rail-free attachment for the AFG. I placed the backing plate for the 4" rail inside the AFG itself and marked off the holes. A little careful 1/4" drill bit work later, and I had holes right through the AFG.(The holes are round, the flashing from the stippling makes them appear otherwise.)

http://i90.photobucket.com/albums/k267/Juggernaut45/DSC_6851.jpg

http://i90.photobucket.com/albums/k267/Juggernaut45/DSC_6852.jpg

Fairly simple so far. The holes encroached a little on the internal locking tabs of the AFG, but not so much that they didn't work. I was confident that the three cross screws in the AFG would hold it together, locking tabs or not. I held the AFG to the underside of the TRX rail, and decided that a slight reduction of the internal polymer "rails" that held the Picatinny rail in place would result in a tighter fit. All told, only about 1/16" of plastic was removed from the inside of the AFG, but that made it sit snugly up onto the TRX, without any see-saw action from a raised center section. Both wings of the AFG now fit like a cradle for the TRX rail.

http://i90.photobucket.com/albums/k267/Juggernaut45/DSC_6846.jpg

A quick trip to Home Depot later, and I had the correct 10-32 machine screws with hex head that I needed. They were 1" in length - too long to fit into the rail without blocking the barrel, but fine for trimming down. I trimmed them to .5" with a cutting wheel, cleaned up with a file, and chased the threads with a 10-32 nut. I added flexible black neoprene washers to both screws, but ended up using a washer on only the front screw.

http://i90.photobucket.com/albums/k267/Juggernaut45/DSC_6854.jpg

Actually installing the AFG itself onto the backing plate turned out to be the most trouble - the TRX rail attachment system already leaves something to be desired - you have to hold the backing plate in place with your finger, inside the tube, and tighten the rail section to it using the screws. If you have short fingers, some of those sections just aren't going on easily, because you can't hold the plate in place.

http://i90.photobucket.com/albums/k267/Juggernaut45/DSC_6856.jpg

Installing the AFG with two screws onto a backing plate, with the additional difficulty of accessing the rear screw, tucked away inside the angled rear portion, took about 20 minutes. I had less trouble with the front screw - just tightened it onto the plate, once the threads caught. I had to cut down an Allen wrench to fit just below the rear screw, inside the angled portion of the AFG, and the threads just refused to catch for the longest time - possibly because they'd been cut down. However, once I removed the neoprene washer from the rear screw, the extra room was just what I needed.

http://i90.photobucket.com/albums/k267/Juggernaut45/DSC_6857.jpg

I can really only justify the couple of hours I spent on this project by saying that it really feels better. The AFG now feels like a natural gripping surface, hugged tightly to the contour of the TRX, as opposed to feeling like a block of material standing just a bit too far out from the curvature of the round rail. It's very sturdy as the backing plate is locked into a groove - no wiggle or wobble, and I have tried to make it twist loose.

http://i90.photobucket.com/albums/k267/Juggernaut45/DSC_6859.jpg

It's hard to show a .25" difference in fit on this part, but this pic captures the snug fit of AFG to rail from the front..

http://i90.photobucket.com/albums/k267/Juggernaut45/DSC_6862.jpg

It was a lot of work, since I took it slow -can't afford to ruin an AFG and replace it. I know I could do it faster next time, and I'm happy with the results. Sometimes, the only way to get exactly what you want is to engineer a solution.

[TwoSqueeze]

:D I see a trip to home depot in my future! Awesome idea bro.

-TS

[Mikey]

Why the washer in the front?

Wouldn't just the screw be a bit lower profile?

Otherwise, looks awesome. Good idea and execution.

-Mike

[KingsideRook]

Why the washer in the front?

Wouldn't just the screw be a bit lower profile?

Otherwise, looks awesome. Good idea and execution.

-Mike

I put it on initially to give me cushion around the screw heads themselves, as the edges sat higher than the portion under the head of the screw.

Turns out the rubbery feel of the the washer is kind of annoying, and about 20 minutes ago, I grabbed one edge of the washer, and pulled it off, then torqued down the screw another turn. Great minds think alike. :D

[seb5]

I like it as I have the rail and AFG here for my next build. If you drilled the rear hole through both the angled portion and the flat portion could have you then got the allen in without damaging the structural integrity of the unit.

[KingsideRook]

It wouldn't have hurt anything to have drilled the hole all the way through, but since even the shortened screw was already too long to fit into the angled portion unless I assembled the two halves of the AFG around the shaft of the screw, I decided to shorten a wrench to fit in the limited space. I just didn't want to put another hole in my stippling, but in retrospect, a through-drilled hole would have worked just as well.

[dirt_diver]

I can't wait to see v2 AFG.

[Seraph]

What I like here is that you weren't afraid to go to work on that gear to make it suit your application better. PM sent.

[Rated21R]

Nice work.

[rob_s]

think there's any potential issue with that front screw heating up and making contact with the support hand?

[M&P45]

Great mod! I'm inspired.. I picked up an AFG at lunch time. Did you remove the material from the top or inside edge of the AFG rails?

[docsherm]

That is a great idea. The only reason am on running an AFG on my Troy rail is that I don't like the gap. Nice solution.

[eternal24k]

they TRX and AFG are made for eachother, and this just makes sense.
Looks great

[KingsideRook]

think there's any potential issue with that front screw heating up and making contact with the support hand?

I considered that, and it's likely that the steel screw will heat up as much as the rail does when firing/out in the sun. However, I think I can live with that - I would be putting my hand on the bare metal of the TRX rail if not for the AFG. I will have to test it, and if it is intolerable, I will try something else, maybe even a polymer screw.


Great mod! I'm inspired.. I picked up an AFG at lunch time. Did you remove the material from the top or inside edge of the AFG rails?

All the material I removed from the AFG was from above the edges of the inner channel that holds the Picatinny rail. I used a couple of bastard files to remove plastic from that area, basically trying to reduce the height of the center of the inside. I didn't remove very much, and if I'd been more aggressive and taken the ridges down to flats, I don't think it would have hurt anything.

[CCK]

I've been thinking of how to do this for my PRI tube.

Would it be possible to countersink the front hole?

[KingsideRook]

I've been thinking of how to do this for my PRI tube.

Would it be possible to countersink the front hole?

I actually wanted to try this - 2 minutes with a larger drill bit - and determined that I wasn't going to risk it on my only AFG. I don't think there's enough material to fully countersink the head of the screw I used, without risking making the remaining plastic too thin underneath. If the AFG were solid plastic from where it meets the TRX to the bottom side, there would be enough material, but since there's a channel for an M1913 rail between the screw and the TRX, I didn't want to risk removing more plastic, since the head of the screw is about 60% of the thickness of the plastic it goes through, and the screw goes right through the seam between the two halves.

[CCK]

could you have placed the front hole behind the removable finger part? near the allen screw tunnel that holds the two pieces together?
And use a 3" backing plate instead of 4, leaving the rear hole where it is.
Chris

[CCK]

What I've thought about doing is modding an AFG to use the center screw to go through a swivel stud.

[KingsideRook]

could you have placed the front hole behind the removable finger part? near the allen screw tunnel that holds the two pieces together?
And use a 3" backing plate instead of 4, leaving the rear hole where it is.
Chris

It looks possible - I am disinclined to disassemble this one to try it just because threading the screws into the backer is a PITA, but I will map it out on the next one and see if it's possible.

The only problem with the idea is that I'd still need to drill a hole through the removable section to access the screw with an Allen wrench - the removable finger-bump section can't be put after the screws are in place. I spent a decent amount of time holding the screws tight against the backing plate, trying to tighten a hidden screw down through a hole in the body of the AFG would probably be even more difficult.

[CCK]

It looks possible - I am disinclined to disassemble this one to try it just because threading the screws into the backer is a PITA, but I will map it out on the next one and see if it's possible.

The only problem with the idea is that I'd still need to drill a hole through the removable section to access the screw with an Allen wrench - the removable finger-bump section can't be put after the screws are in place. I spent a decent amount of time holding the screws tight against the backing plate, trying to tighten a hidden screw down through a hole in the body of the AFG would probably be even more difficult.

but you'd only have a hole and not a screw head sticking through.

[Col_Crocs]

It looks possible - I am disinclined to disassemble this one to try it just because threading the screws into the backer is a PITA, but I will map it out on the next one and see if it's possible.

The only problem with the idea is that I'd still need to drill a hole through the removable section to access the screw with an Allen wrench - the removable finger-bump section can't be put after the screws are in place. I spent a decent amount of time holding the screws tight against the backing plate, trying to tighten a hidden screw down through a hole in the body of the AFG would probably be even more difficult.

This is exactly what Ive been thinking about ever since you started this thread. I just dont have an actual AFG on me to see whether or not it's possible.
You will have to drill a hole through the insert but you can keep it small enough to simply allow access by the allen wrench.
Should be a lot less bothersome than the screw head sticking out if that's the main concern.

[Col_Crocs]

What I've thought about doing is modding an AFG to use the center screw to go through a swivel stud.

Ive been looking at a few swivel studs and you might have to dremel the channel a bit to accommodate the one but that actually sounds like a great idea.
How do you ensure a snug fit though? Does this fall solely on the rear screw or do you plan on test fitting the stud as you go?

[KingsideRook]

This is exactly what Ive been thinking about ever since you started this thread. I just dont have an actual AFG on me to see whether or not it's possible.
You will have to drill a hole through the insert but you can keep it small enough to simply allow access by the allen wrench.
Should be a lot less bothersome than the screw head sticking out if that's the main concern.

It may be doable - I think the length of backer is of the correct length, etc. That said, my current install method already involves folding the two halves of the AFG around the shafts of two screws at the same time, while pushing the removable center section into place. Once you've tried getting one of these grips onto a TRX, you might discover that making the install more complex is...more complex. It's already kind of a 4 handed job. :D With a foolproof method of holding the backing plate perfectly in place, or an extra set of skilled hands, I think you would have a lot less trouble when it came to hiding the screw head under the panel - as it stands, getting the front screw in place makes installing the rear one a lot easier.

That said, I am all about people experimenting with their gear - that's how I got this done. On my next AFG/TRX combo (FDE), I will will probably measure for the "hidden screw" method on a 3" backer to see if I can make it work.

[KingsideRook]

Update - thanks to rob_s for his practical concern on the front steel screw absorbing and transferring heat. I didn't really need much of an excuse to tinker with this to improve it.

I removed the metal screw from the front of the AFG, and recessed the area around the hole, very carefully - I had a 3/8" drill bit of just the right size for the head. I located a 10-32 1" Nylon screw, and cut it down to .5", applied Loctite. The screw will not shear unless I apply some gun-destroying force - it took some effort to cut. I checked by applying pressure from all side, no looseness or wiggle has been introduced into the fit.

http://i90.photobucket.com/albums/k267/Juggernaut45/DSC_6914.jpg

The head of the nylon screw fit just below flush in the recess. Feel better, looks better, and not likely to heat up and nuke my hand. The rear screw is still a steel part, and when tightened into the backing plate in the groove, will by itself hold the AFG on very securely - so I'm not concerned about having a nylon screw securing the front.

Now, can we please get Troy to make some direct-connection-method, curved, low-profile TRX rail covers?:D

[Jake'sDad]

What a great idea, and great detailed instructions!

It's threads like this that make M4C one of the best sources of firearms info on the internet.

[Bobert0989]

Will you do this for me? ol... I just asked how this could be done/how it looks in another thread and was sent here. Is your install holding-up? Do you like the end-results?

Thanks!

[KingsideRook]

Will you do this for me? ol... I just asked how this could be done/how it looks in another thread and was sent here. Is your install holding-up? Do you like the end-results?

Thanks!

It is holding up over a lot of serious yanking - I have been trying to make it fail from rough handling, because if it's not going to hold up, I want to know now. 3 30-rd magazines test fired. I went back to using 2 metal screws, slightly recessed, because the heat transfer is unnoticeable even in rapid fire.

[Bobert0989]

It is holding up over a lot of serious yanking - I have been trying to make it fail from rough handling, because if it's not going to hold up, I want to know now. 3 30-rd magazines test fired. I went back to using 2 metal screws, slightly recessed, because the heat transfer is unnoticeable even in rapid fire.

That's good to hear that it's surviving some abuse, good overall finished product then!

[Teufelhunden]

With a foolproof method of holding the backing plate perfectly in place

I've had good luck with a method I developed. Use the allen wrench that came with the rail that fits the larger bolts that tighten the rail onto the barrel nut. Position your backer plate into place, then slide the allen wrench through the holes in the rail just over the plate. It should just fit. The end effect is once the wrench is in place, rotating it slightly will turn the edges (instead of the flats) in contact with the plate and top of the hole, putting enough pressure on the plate to keep it from sliding around. There's not enough pressure to damage anything, but just enough to keep the plate from sliding away from the screws.

-Teuf

[OMD]

Great idea Teuf!

[hirohawa]

Great job! I am going to try this

[markm]

Iraqgunz will love this one when he wakes up. :dance3: