Early production LMT MRP differences

[dwd1985]

A few weeks ago, LMT made a post on their facebook page showing what they refer to as early production MRP CQB uppers, and mentioned how the early models were billet produced. The actual copy/paste is "Throwback Thursday! Early MRP and CQB monolithic uppers. Fun fact: our early MRPs were billet produced. A lot of quality CNC machining went into these. #lewismachineandtool #lmtdefense #mrp #monolithic #quadrail #cnc #billet #og"

What is the production process for current MRP uppers, and how does it differ from the older method of billet machining? Is there any advantage or weakness in either version? I'm just unclear on why they would have changed the manufacturing process, and if that makes a stronger product now then they used to offer.

[Duffy]

The barrel nut area is slightly different, early ones don’t have a QD socket, but a longer lightening cut.

Early 2004 era MRP:


Later models have a QD socket and a shorter lightening cut above the bolts.

[dwd1985]

The barrel nut area is slightly different, early ones don’t have a QD socket, but a longer lightening cut.

The QD socket I knew about, as for the lightening cut, they look identical to me in your pictures, but I suppose there could be something I'm not seeing. What I'm really asking is, if they make reference to how the early production models were billet machines, what is the current production method if not billet machined?

Edit: I now see the difference in the lightening cut in both rifles in the second pic. I was comparing the rifle in pic 1 to the front rifle in pic 2, and admittedly didn't really look at the rifle in the background of pic 2. The difference in lightening cuts is pretty clear there.

[Duffy]

I'm not sure, the two MRPs I have are almost 10 years apart, I can't tell the differences other than the rear QD sockets, shorter lightening cuts, and maybe provision for the KAC cover clips in the rear. Maybe the newer ones were extruded then machined, vs. machined from a solid block?

[jerrysimons]

A few weeks ago, LMT made a post on their facebook page showing what they refer to as early production MRP CQB uppers, and mentioned how the early models were billet produced. The actual copy/paste is "Throwback Thursday! Early MRP and CQB monolithic uppers. Fun fact: our early MRPs were billet produced. A lot of quality CNC machining went into these. #lewismachineandtool #lmtdefense #mrp #monolithic #quadrail #cnc #billet #og"

What is the production process for current MRP uppers, and how does it differ from the older method of billet machining? Is there any advantage or weakness in either version? I'm just unclear on why they would have changed the manufacturing process, and if that makes a stronger product now then they used to offer.

Current MRP’s are machined from a forging (hot metal pressed into shape, like standard mil-spec recievers) early ones we machined from a single block of aluminum. Somebody who knows CAD better than me could add here but in addition to forgings being stronger I think it takes less machine time to make because the rough forging follows the rough shape of the final piece as opposed to a box or block shape of billet. As a process, using custom forgings is a bigger commitment financially to develop and requires a high volume of sales to amortize the investment, which LMT has impressively accomplished. This is why your average boutique AR manufacture uses either standard Mil-Spec reciever profile forgings commonly available or the billet cnc process if they have custom profiles. Vltors MUR uppers (forged 7075), Aero’s M4E1 (forged 7075), and of coarse LMT’s monolithic upper reciever rail combo (one piece, forged 7075) are the exceptions I know of and I’ll add to that Noveske’s old Gen 2 lower receivers for nostalgias sake!

[jerrysimons]

Adding to me last post I believe LMT also mentioned you could also slightly make out tooling marks under the anodizing on the early billet machined MRP’s shell deflector. With this comment I surmise that the shell deflector is an area on their forging that as an outer extremety get its shape from the rough forging process where as with the billet process the shell deflector had to be %100 machined and contoured into shape.

[ALCOAR]

Early proto, and initial release models of both MRP, and MWS chassis were made of billet, however they are really rare. Much more common to see the early MWS billet chassis vs. an early MRP chassis.

The MRP hit the market circa 2004.

Gen1 had no QD sockets, 2 silver washers, and called for 90ft/lbs torque

Gen 2 had rear QD sockets, figure 8 washer, and called for 140ft/lbs torque

Gen 3 had front/rear/bottom QD sockets, figure 8 washer, and called for 140ft/lbs torque

Gen 4 was the SLK slick chassis

Gen 5 was the MLR/MLC MLOK chassis

From LMT.....

" forged is always stronger. Billet is usually extruded aluminum, meaning raw material is pushed through a sizing die creating round or bar stock. In the case of forged, the raw material is smashed into a mold creating all the external features in the process and making for a denser material with better strength characteristics. The benefit of billet is freedom to machine whatever you want. Forging dies are expensive, that’s why you see some AR manufacturers that have no requirement for milspec external features, choosing billet.

[dwd1985]

Really good info across the board here, from all who responded. Thank you. didn't know a lot of these details.

Gen1 had no QD sockets, 2 silver washers, and called for 90ft/lbs torque
Gen 2 had rear QD sockets, figure 8 washer, and called for 140ft/lbs torque
Gen 3 had front/rear/bottom QD sockets, figure 8 washer, and called for 140ft/lbs torque
Gen 4 was the SLK slick chassis
Gen 5 was the MLR/MLC MLOK chassis

I have two chassis. From this list, it seems I have a Gen 2 MRP (rear QD and quad rail) and a Gen 3 MRP (front/rear/bottom QD and quad rail). I realized I don't need two, so trying to figure out which one to part with, and this info helps immensely. Thanks again.

[jerrysimons]

Really good info across the board here, from all who responded. Thank you. didn't know a lot of these details.



I have two chassis. From this list, it seems I have a Gen 2 MRP (rear QD and quad rail) and a Gen 3 MRP (front/rear/bottom QD and quad rail). I realized I don't need two, so trying to figure out which one to part with, and this info helps immensely. Thanks again.

I think only gen 1 was machined from billet extrusion.

[MorphCross]

Colt 694x uppers with monolithic quad handguards are also forged 7075.