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.
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.
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?
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!
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.
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.
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.
Ah thanks, also LWRCi’s upper/rail design is forged (“coined” forged/struck twice) aswell as their Ambi lowers. Their DI guns I think are worthy of M4C embrace (bracing for flaming). Probably the best value in custom/“improved” offerings out there.
Getting back on topic just like the MUR I conceptually love the MRP (whether Quad/proprietary negative/M-Lok) for the reinforcement at the barrel extension/receiver lockup area.
Like Mark said I don’t think it makes much difference to the average consumer whether your MRP is forged or billet but I am a huge fan and geek out on LMT MRP. Look at the rail races for IR laser users moving toward bomb proof fat profiles or 7075t6 billet over 6061 and while that is interesting too I have to chuckle a little and think LMT got you beat 10 years ago with single piece forged 7075 monolithic upper/rail.
Then again ironically I don’t own an MRP but have spent time scouting the EE for used Hodge wedge lock rails. Why? I suppose it is because the barrel you are stuck using which are great but you are stuck with it. LMT could certainly offer more profile options. LMT did make it to the negative space mount system party with MLOK, better late then never!
I, for one, am impressed with the number of option available. in DI 5.56, theres 10.5, 11.5, 16, 18, stainless 16, maybe even a few others. Then there’s piston 12" and 16" 5.56. .300 BO in 10.5" and 16". 6.5 Creedmore options, .224 Ruger…that’s actually a pretty good variety. I currently have a 10.5 DI 5.56, 16" DI 5.56, and 12" .300 BO. Always on the lookout for an 11.5" and a piston conversion.
I more meant the profile of the barrel / weight over the caliber or length. Another thing barrel related to why I haven’t picked up an MRP is the barrels gassing. I like to turn the gassing down on most set ups to run suppressed and you are stuck with LMTs port sizing. Nothing too big in either case just kinda thinking out load as to why I like MRP so much but never got one. I think Marvin Pitts is the only Smith still doing MRP barrel conversions. I would like to research more into the quality of conversions versus factory barrels.
