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Update Dimpled: [Modding an LMT MRP CQB Quad w/ Riflespeed etc]

Bilb0

Bilb0

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Sep 16, 2023
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Dexter, Missouri
LMT MRP CQB 9.25" with 11.5" barrel

Riflespeed part number RS7533

.750
3.3 inches long = (gas block+knob length)

The 1.9" and 2.1" knob would not peak out of quad rail enough for ease of use. The 2.1" knob would have been cutting it close. I may be wrong but we shall see.

I dig and find nothing posted anywhere about modding the LMT barrels with adjustable gas blocks besides slight mentions about how D. Wilson provides these services.

So I thought it would be a good idea to show others what Im doing and we can see how it turns out 😁. Fail or win.

The 45° gas port is on the barrel side. Gas block is normal. .750 gas block.

LMT must press fit their pins. Im convinced after bending a typical punch and having to step up to a heavier punch and hammer, then it came out like butter.

LMT gas blocks are press fit. Torching it won't make it budge. Obviously didnt want to overdo the heat so moved on.

I didn't want to deal with putting the muzzle end under pressure with the press. So I made a few relief cuts with the grinder by taking off the bulk of the block metal on both sides symmetrically.

Then stepped to a Dremel with grinding wheel for the more precision cuts in the tight areas of the gas block so that the barrel itself wouldn't get tickled.

Once enough material was removed it slid off like butter by gentle tapping it.

Don't judge my grind job 😂, i was testing different techniques and angles to avoid any damage to the barrel.

Next up Riflespeed fitment.

20240315_134253.jpg
 
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Did similar on my POF Revolution DI. Was a b*tch to get the stock gas block off but unfortunately none of their control knobs (really adjustment collars) are "ideal". There's a good gap between the .950" and the 2.160" knob (which is too long) and they need a new knob right in the middle of those two for rifle-length gas systems. Please Keith please. Had to design my own low profile quick lever kit to work under the POF's hand guard. Now that it's on, works well and as good as the stock POF dictator gas block is, the Riflespeed is better and tool-less adjustment is the bees knees. That's the .950 collar in the pic.

IMG_5485.jpg
 
Ape_Factory said:
Did similar on my POF Revolution DI. Was a b*tch to get the stock gas block off but unfortunately none of their control knobs (really adjustment collars) are "ideal". There's a good gap between the .950" and the 2.160" knob (which is too long) and they need a new knob right in the middle of those two for rifle-length gas systems. Please Keith please. Had to design my own low profile quick lever kit to work under the POF's hand guard. Now that it's on, works well and as good as the stock POF dictator gas block is, the Riflespeed is better and tool-less adjustment is the bees knees. That's the .950 collar in the pic.

View attachment 8373651
Click to expand...


Nice work! ; I noticed the same when measuring how well one between 2.1 and 3.3 would have worked well on this project. And luckily the 3.3 fit decent. I'm assuming your can would hit the 2.16 knob as why you went with the .95?
 
Yeah unfortunately the Huxwrx muzzle device would cause interference. If one were running a straight muzzle brake that's close to the same diameter as the barrel, no issues, could go with the longer collar. Here's the 2.1 and how much over it'd be. So close yet so far away.
IMG_4618.jpg
 
Ape_Factory said:
Yeah unfortunately the Huxwrx muzzle device would cause interference. If one were running a straight muzzle brake that's close to the same diameter as the barrel, no issues, could go with the longer collar. Here's the 2.1 and how much over it'd be. So close yet so far away.
View attachment 8373664
Click to expand...
Psst. That's the 3.3 , what I have.

So your using the 2.1 I noticed the quick lever threaded holes. I accidentally bought the quick lever kit for the 1.9 thinking it had the threaded holes and realized the 2.1 knob only has the threaded holes for the quick lever kit lol.

So we both could utilize the size between 2.1 and 3.3 heh heh. Will be fun to try if they make one


Screenshot_20240315_235434_Brave.jpg
Screenshot_20240315_235953_Brave.jpg
 
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Yes, part number RS7533 if you purchase as a complete unit. I was under the assumption, perhaps wrongly, that the 7533 was the 2.160" length. The RS7521 is the .95" length, not the 2.160" length, as that would make too much sense. The shortest, which is 7519 (in the .750 gas block journal size) is .75" in length.

So...
7519-.75"
7521-.95"
7533-2.16"
7543-3.160"
7548-3.660"
7558-3.460"
 
Ape_Factory said:
Yes, part number RS7533 if you purchase as a complete unit. I was under the assumption, perhaps wrongly, that the 7533 was the 2.160" length. The RS7521 is the .95" length, not the 2.160" length, as that would make too much sense. The shortest, which is 7519 (in the .750 gas block journal size) is .75" in length.

So...
7519-.75"
7521-.95"
7533-2.16"
7543-3.160"
7548-3.660"
7558-3.460"
Click to expand...
I turned my knob to 12 and measured. Think that may be why the difference I believe it becomes longer. I was hoping you had the 7519 but I noticed your quick lever holes. I have some new if you want them for yours to make it easier to adjust

Oh! I measured from far end of the gas block to the end of the knob to get their measurements.
 
They do get longer as you adjust. The last photo I posted was at the shortest setting so it'd only get worse with adjustment. I actually ordered some of their quick control knobs and ended up misplacing them, possibly thrown out. I have lots of small hex head screws and ended up with some that worked and cleared the hand guard. But appreciate the offer!
 
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Ape_Factory said:
They do get longer as you adjust. The last photo I posted was at the shortest setting so it'd only get worse with adjustment. I actually ordered some of their quick control knobs and ended up misplacing them, possibly thrown out. I have lots of small hex head screws and ended up with some that worked and cleared the hand guard. But appreciate the offer!
Click to expand...

No problem 👊 Oh nice that's right you have a tight squeeze with the handguard clearance! The riflespeed screws stand quite proud
 
@Bilb0 that looks like a great setup. Out of curiosity, did you also look at the feasibility of doing this with the M-LOK monolithic uppers? curious if the internal dimensions would create interference between any accessories mounted around the gas block/Riflesspeed. It shouldn't at all on the Shovelnose uppers, but it's unclear on the SPECWAR and MRPs.
 
Leftie said:
@Bilb0 that looks like a great setup. Out of curiosity, did you also look at the feasibility of doing this with the M-LOK monolithic uppers? curious if the internal dimensions would create interference between any accessories mounted around the gas block/Riflesspeed. It shouldn't at all on the Shovelnose uppers, but it's unclear on the SPECWAR and MRPs.
Click to expand...

Thank you!

The Internal clearance for attaching Mlok accessories on Mlok versions of this upper with the riflespeed gas block is unknown. Machining out material to allow clearance needed for attaching Mlok accessories around gas block area may be needed.

I sadly don't have an Mlok version of this upper to know. Would be fun to see what needs to be done to make it work.

20240317_122631.jpg
20240317_122851.jpg
 
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LRRPF52 said:
A buddy of mine just had a shop do a Noveske 12.5” Grendel MRP conversion for him.

Looking forward to seeing it come together.
Click to expand...

Nice, yeah I'm about sleeve and notch a 22lr barrel to play with so I don't jack up this one with leading.
 
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If I could go back in time, I would show Stoner the MRP upper receiver and quick-barrel change system to make it the standard out of the gate.

They didn’t have CNC yet though, and machining that upper would have been a bit of a witch in mass-production, so it would have been anachronistic.

A forging with some type of QC barrel extending the upper forward a little bit would have been good and appropriate for the time, with modular handguard and barrel length options. The flange fit joint approach would have been doable as well, but with some way to avoid needing longitudinal fasteners and wrenches.
 
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