LMT SOPMOD Question

[ez bake]

An H-buffer won't hurt to have in that carbine. The sling mount you will be happy with depends on what you plan on doing with the carbine (I have 2-point slings on all mine but I recognize the need/benefits of a single point and know plenty of folks who own them.

If you're looking for a single point on the back of the receiver, then I'd get a Magpul ASAP. They're a bit tricky to install, but worth it for weak-side transitions if you ever use your AR for comps, hard training, or just serious fun.

You'll need an AR-15 spanner wrench made for the castle nut to replace the extension tube. Everyone who owns an AR should have one of these (they can be had for cheap) so its a good idea to pick one up.

I'm planning on ordering an LMT Mil-Spec Tube.

I have the 16" M4 carbine type of bushmaster. Would you recommend an H buffer and sling mount?

Also, do I need to take this to a gunsmith in order to replace tube?

Thanks for the info.

 

[kriket1911]

I second the vltor Tube it is closer to spec then any of the other one's. And if your not a handyman type, then I would take it to a gunsmith. It's not a difficult process but it might be better to go that route. Good luck and enjoy your new stock they are 1,000 times better then the standard m4 stocks.

 

[ActionJaxn]

Anybody have an excellent castle nut wrench for sale?

 

[ez bake]

Anybody have an excellent castle nut wrench for sale?

I'm pretty sure that Mark's Firearms carries them.

 

[ActionJaxn]

Okay, got an armorer's wrench, VLTOR tube, and Magpul ASAP. Now all I need is a Magazine well block. Thinking about filming this for youtube and addding to the collection that is already out there, lol.

 

[BeRotten]

Okay, got an armorer's wrench, VLTOR tube, and Magpul ASAP. Now all I need is a Magazine well block. Thinking about filming this for youtube and addding to the collection that is already out there, lol.

Beware the rear take down pin detent spring. It's held in place by receiver plate. I loosen the castle nut while holding the plate down. Once the nut is fully loosened, slowly let the plate rise and rotate the plate and tube, capture the spring and remove, then go about your replacement business.

Just a note, due to having nearly putting my eye out with that spring.

 

[ActionJaxn]

Well, here are the steps I did to take the stock off.

1. Unassembled rifle, took buffer spring out of lower.
1. Inserted an old steel gi (unknown manufacturer) mag that I had lying around into magwell of AR lower.
2. Used the magazine to hold the AR lower to a Vise.
3. Used GearTec armorer's wrench to loosen castle nut.
4. Removed lower from Vise.

Now, this is where it gets stupid.

After having viewed several videos of the proper way to unassemble the buttstock, I proceeded to not follow their advice and unscrewed the buttstock without thinking twice about it (stupid). The detent pin and spring flew out of the buttstock. I had to spend a few minutes finding the buffer detent pin.

4. After finding, screwed castle nut onto VLTOR tube using the whole thread (very tight fit).
5. Fitted magpul ASAP onto VLTOR tube.
6. Screwed tube onto lower to get it started making sure not to bend detent spring.
7. Carefully held magpul ASAP against receiver while screwing buffer tube into lower receiver, while holding buffer detent pin down for buffer tube to screw pass holding it into place.

That step was needing four hands to do, lol.

8. After buffer detent pin was held down by buffer tube, I used a needle nose plier to insert the tiny steel block to hold magpul and vltor tube in place.

Also required four hands.

9. I then proceeded to hold ASAP down while using Armorer's wrench to tighten down castle nut (tight castle nut).
10. After castle nut was tightened against lower, set whole assembly into vise again.
11. Tightened castle nut using wrench.

Notes after install:
Don't remove buffer tube without holding down buffer tube detent pin and spring.
Is the castle nut supposed to be that tight screwing onto VLTOR tube?
Using the geartec wrench to loosen and tighten the castle nut left little circular indentions on castle nut where wrench contact it. Was I using wrong method?

 

[BeRotten]

If this is your final assembly and modification to your receiver tube, you might consider staking the nut so that it can't back off. The smaller notches on the nut on the receiver plate side are used for this. This is the military method of securing the nut. Some people use a drop of loc-tite. The users over on ar-15 are against the loc-tite method and recommend staking.

 

[ez bake]

If this is your final assembly and modification to your receiver tube, you might consider staking the nut so that it can't back off. The smaller notches on the nut on the receiver plate side are used for this. This is the military method of securing the nut. Some people use a drop of loc-tite. The users over on ar-15 are against the loc-tite method and recommend staking.

I wouldn't stake it if you ever plan on changing it again - as a matter of fact, I put a tiny bit of oil on the threads and run the nut over them (and then remove the nut and wipe/clean off any excess) so that I can get the castle nut on/off easier and I've yet to have a castle-nut back off if you properly torque it.

That is the only point on "the chart" that I have contention with - it serves no purpose other than to ensure that you break a castle-nut wrench (or gall up your castle-nut).

The nut will stay on there with no loc-tite if you torque it properly.

Sound like the OP had a good learning experience - that Magpul ASAP is a great product, but I still don't know why they made it puzzle-tastic with that stupid tiny cube of metal instead of just making it like a normal retainer plate.