View Full Version : Early production LMT MRP differences
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 barrel nut area is slightly different, early ones don’t have a QD socket, but a longer lightening cut.
Early 2004 era MRP:
https://i75.photobucket.com/albums/i314/Duffypoo/2004MRP_zpsfgzpdwzh.jpg (https://s75.photobucket.com/user/Duffypoo/media/2004MRP_zpsfgzpdwzh.jpg.html)
Later models have a QD socket and a shorter lightening cut above the bolts.
https://i75.photobucket.com/albums/i314/Duffypoo/MRPs.jpg (https://s75.photobucket.com/user/Duffypoo/media/MRPs.jpg.html)
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.
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
02-12-19, 10:45
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
02-12-19, 10:52
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.
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
02-12-19, 13:51
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
02-12-19, 14:07
Colt 694x uppers with monolithic quad handguards are also forged 7075.
But for the end user does it really make any difference if both are done with high quality manufacturing processes? It is my genuine question?
I have several LMT MONOLITHIC uppers and a Colt 6945. Just really like them all.
PB
The barrel nut area is slightly different, early ones don’t have a QD socket, but a longer lightening cut.
Early 2004 era MRP:
https://i75.photobucket.com/albums/i314/Duffypoo/2004MRP_zpsfgzpdwzh.jpg (https://s75.photobucket.com/user/Duffypoo/media/2004MRP_zpsfgzpdwzh.jpg.html)
Later models have a QD socket and a shorter lightening cut above the bolts.
https://i75.photobucket.com/albums/i314/Duffypoo/MRPs.jpg (https://s75.photobucket.com/user/Duffypoo/media/MRPs.jpg.html)
Badass rigs, I really like the way you have that sling tucked to stock.
PB
jerrysimons
02-12-19, 15:07
Colt 694x uppers with monolithic quad handguards are also forged 7075.
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.
MorphCross
02-12-19, 15:17
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.
You won't catch any shade from my direction.
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.
jerrysimons
02-12-19, 15:38
You won't catch any shade from my direction.
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.
jerrysimons
02-12-19, 15:47
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! :cool:
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! :cool:
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.
It's Sling Keep B, we make and sell those :)
Badass rigs, I really like the way you have that sling tucked to stock.
PB
jerrysimons
02-12-19, 18:52
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.
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.
Wait, there are guys doing MRP conversion barrels? How exactly does that work? I’d love if I could get a .22lr barrel made.
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.
Happy to help friend :)
I too have a Gen 2, and 3 rifle length chassis, and recently had the same conversation in my head about which one to get rid of. I never use the front QD positions so I figure I'll sell the current Gen 3 chassis here shortly. The Gen 1 chassis are really rare in general as they rolled out the Gen 2 sometime in 2005 IIrc. By the time I got into the MRP game in 2009, they were on the Gen 3s.
I bought a MLR chassis that has pretty much ruined me I think. While you can't remove and install the barrel with the MLOK kit on, it's feel in the hands is perfection. It's a tradeoff with this one particular chassis, but to me the barrel hookup + monolithic top is where all the magic really is, and every chassis will have that. I like the railed ones for precision pieces still I think though. I like to pull the barrels on my 5R SS barrels to clean, and I don't really like the idea of mounting a bipod to a MLOK chassis as I would the railed one. I'm also not point shooting much with a Recce or SPR MRP setup.
Wait, there are guys doing MRP conversion barrels? How exactly does that work? I’d love if I could get a .22lr barrel made.
Spikes made .22lr and 9mm conversions for the MRP a long time ago. Occasionally one will pop up on an EE. Marvin Pitts as eluded too above is not only the best, but currently the only person doing the job commercially. I spent a month checking around, and sadly atm it's Marvin or DIY. I bought a MRP barrel off of GB around XMAS, and the guy had others that were converted by himself. They looked awesome, and I sent him multiple emails asking if he'd be interested in making some money...never heard back sadly.
This was a 5.45 barrel he did, but it wasn't threaded.
http://i63.tinypic.com/j0fyf7.jpg
He used the 5.56 16" LMT MRP barrel as donar for the pressfit headspace collar, barrel ext., and piston parts.
http://i63.tinypic.com/j0fyf7.jpg
eta: since my pics aren't showing up, here is the old listing for the .22lr conversion the guy did:
https://www.gunbroker.com/item/795056318
jerrysimons
02-12-19, 20:40
Maybe I’ll convert a Hodge Defense Barrel into a MLOK MRP chassis, is that crazy? Lol :D looks like a straight gas tube with a taller gas block and some barrel extentsion machining by Marvin Pitts is all that is required. Does the MRP chassis actually lock the barrel up tighter in the upper than a traditional barrel nut set up? Some of the the secret sauce for precision in conventional uppers is a tight upper reciever bore, I would guess the way the MRP clamps and squeezes the barrel extentsion makes for a solid lock up.
How do you get a hold of this Marvin Pitts guy? Does he have a website or store?
MorphCross
02-12-19, 21:51
How do you get a hold of this Marvin Pitts guy? Does he have a website or store?
Look up Nefarious Arms on Facebook, there should be contact info there.
I bought a MLR chassis that has pretty much ruined me I think. While you can't remove and install the barrel with the MLOK kit on, it's feel in the hands is perfection. It's a tradeoff with this one particular chassis, but to me the barrel hookup + monolithic top is where all the magic really is, and every chassis will have that. I like the railed ones for precision pieces still I think though. I like to pull the barrels on my 5R SS barrels to clean, and I don't really like the idea of mounting a bipod to a MLOK chassis as I would the railed one. I'm also not point shooting much with a Recce or SPR MRP setup.
Which 5R, 16" or 20"? Do you have dedicated BCGs (or bolt) for each barrel assembly, or run common BCG and just switch out the barrel?
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
Those are going to be in/lbs not ft/lbs;) Mine is a Gen2 but didn't come with a Figure 8 washer but just the 2x siver washers.
It's Sling Keep B, we make and sell those :)
Thanks , just put in an order for a few.
PB
Those are going to be in/lbs not ft/lbs;) Mine is a Gen2 but didn't come with a Figure 8 washer but just the 2x siver washers.
Excuse me, and I appreciate you correcting my mistake.
I have an early Gen 2 that had the silver washers as well, and talked with Gene back in the day, and they sent me a few Figure 8 washers.
I imagine sometime into Gen 2 time they changed the washer setup.
ETA: Info from a conversation I had in 2010 with a friend who worked at LMT
"There are a few reason we did the switch.....
1) Torque specs
2) Equalized clamping force. The Silver lock washers put more force on the receiver where the silver washers contact the MRP. The new style ones spread the pressure out more which allows for a higher torque spec. The original 90inlb was only recommended for like the first 6 months of the MRPs release to the civi world.
3) Some of the reasons are proprietary and I cannot go into depth on them."
Which 5R, 16" or 20"? Do you have dedicated BCGs (or bolt) for each barrel assembly, or run common BCG and just switch out the barrel?
These are the older Mike Rock 5R SS SPR barrels. Last time I checked LMT was trying to make these barrels in house.
My MRP Recce w/ the 16" uses an exclusive BCG, but outside of that I don't dedicate any BCG to others barrels. I bought a 14.5" MRP barrel recently that came with a dedicated bolt so I will continue on with that one as well. Bear in mind, I only run Colt, LMT, or BCM bcgs in these rifles.
https://i.imgur.com/Ou8TaUE.jpg
https://i.imgur.com/HX0iM03.jpg
ETA: 16" & 18" models.
Thanks ALCOAR, I figured best practice was dedicated bolt but was wondering what actual field practice was like. I have a new 20" L7SD1S, two chassis and two 16" CL. I really prefer the 16" configs, and have no time behind the 20" yet to see what it can do.
militarymoron
02-14-19, 10:46
Spikes made .22lr and 9mm conversions for the MRP a long time ago.
I have one of the spike's .22lr MRP barrels. Note that it's not compatible with CMMG-type .22lr bolts; the collars are different. POI of the .22lr MRP barrel was quite a bit different than the 5.56 MRP barrel, which required an optics swap when changing barrels.
https://i.imgur.com/AlUlt2v.jpg
https://i.imgur.com/SA0GYGe.jpg
Thanks ALCOAR, I figured best practice was dedicated bolt but was wondering what actual field practice was like. I have a new 20" L7SD1S, two chassis and two 16" CL. I really prefer the 16" configs, and have no time behind the 20" yet to see what it can do.
If you really want a great round for every MRP barrel I've ever shot it out of, then get some Hornady 55gr. VMAX. I've used it as my "control" for years when evaluating accuracy/precision out of MRPs.
If you decide to run dedicated bolt/barrel setups, make some of these widgets to keep the bolts stored together with the barrels. I can't take credit for the design, I just bought it.
https://i.imgur.com/mZSWYXQ.jpg
https://i.imgur.com/gklS7mO.jpg
I have one of the spike's .22lr MRP barrels. Note that it's not compatible with CMMG-type .22lr bolts; the collars are different. POI of the .22lr MRP barrel was quite a bit different than the 5.56 MRP barrel, which required an optics swap when changing barrels.
https://i.imgur.com/AlUlt2v.jpg
https://i.imgur.com/SA0GYGe.jpg
Lucky dog you! I'd love to have one now that I have spare chassis, as I would run a dedicated .22lr setup so the optic/shift wouldn't bother me.
Great pics, and info as always.
Lucky dog you! I'd love to have one now that I have spare chassis, as I would run a dedicated .22lr setup so the optic/shift wouldn't bother me.
Great pics, and info as always.
ALCOAR, were you formerly screen named Trident82? I’ve loved your MRP posts over the years, and they contributed to me finally picking up one of the CQB uppers when Brownells has them on sale. I’m hooked.
ALCOAR, were you formerly screen named Trident82? I’ve loved your MRP posts over the years, and they contributed to me finally picking up one of the CQB uppers when Brownells has them on sale. I’m hooked.
Thank you for the kind words. Yeah my former screenname was Trident82, but after years I realized it was likely signaling to some I had a "Trident" as in the Navy Seal kind especially on a gun board, even though that was never my intent when choosing it back in the day.
It's great to hear you got the Brownells MRP deal. That was such a fantastic opportunity to bring those into the MRP fray that had always been curious, but stayed away from the cost. Welcome to the MRP family!
LMT has made significant changes towards the civilian market over the last year or two, and their products are reflecting that. Moreover they actual have a social media presence, and are much more approachable as a civilian. You can use the code IG15 if you buy anything from their website if you need proof of this;)
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