Magpul PRS Gen 3 too long on your RPR (or any other chassis)?

[trob_205]

So I’ve really liked the Magpul PRS gen 3 stock on my 6.5CM RPR, but it has one major draw back. It’s LOP is shortest possible measurement is 15”. My AICS chassis 700 is set up for me right around 14”. I’ve contacted Magpul twice in the matter and get the same “we don’t currently offer any shorter butt pads for the Gen 3 at this time”. Cool story, but not what I was looking for. I love the feel and love the adjustable butt pad, but I was just about ready to give up and prowl for a PRS gen 2 or the LMT Precision Stock. I really didnt want to give up the adjustable butt pad. So after me and a buddy both in the same predicament. He found a buried thread on M4carbine about a guy chopping his carbine tube adapter in his Gen 3. Wheels started turning on how to cut it and I ended up here. The cut landed me just a hair over the 14” mark ??. You could take it lower but you would have to modify the carbine tube stock adjustment lug channel from the back end from what I saw. The stock still locks up very tight on the tube with no real compromise of it potentially sliding after being altered (my buddy and I both pulled really tight on the stock with just the rear screw tight and couldn’t get it to budge. So the QD slog mount screw only made it tighter!) When the Gen 3s first became available I saw a guy on the RPR thread asking if there was any alternative to the long LOp. I’m 6’ tall so I figured we weren’t the only people bummed out about this so I’d like to share some pics of the Mod.

 

[FromMyColdDeadHand]

Nice. I agree, the PRS stocks need a 'negative' adjustment for length for those of us with T-Rex arms. You'd think with all their engineering, that they would have made something by now.

 

[Matt_S]

Always was my main problem with the PRS stock system on the RPR’s, every time I installed one on a customers rifle I kept thinking there has to be a fix... trob_205 and I talked about it a few times and finally found a good solution that many people can do with a couple simple tools.

 

[mechanic1776]

So I’ve really liked the Magpul PRS gen 3 stock on my 6.5CM RPR, but it has one major draw back. It’s LOP is shortest possible measurement is 15”. My AICS chassis 700 is set up for me right around 14”. I’ve contacted Magpul twice in the matter and get the same “we don’t currently offer any shorter butt pads for the Gen 3 at this time”. Cool story, but not what I was looking for. I love the feel and love the adjustable butt pad, but I was just about ready to give up and prowl for a PRS gen 2 or the LMT Precision Stock. I really didnt want to give up the adjustable butt pad. So after me and a buddy both in the same predicament. He found a buried thread on M4carbine about a guy chopping his carbine tube adapter in his Gen 3. Wheels started turning on how to cut it and I ended up here. The cut landed me just a hair over the 14” mark ??. You could take it lower but you would have to modify the carbine tube stock adjustment lug channel from the back end from what I saw. The stock still locks up very tight on the tube with no real compromise of it potentially sliding after being altered (my buddy and I both pulled really tight on the stock with just the rear screw tight and couldn’t get it to budge. So the QD slog mount screw only made it tighter!) When the Gen 3s first became available I saw a guy on the RPR thread asking if there was any alternative to the long LOp. I’m 6’ tall so I figured we weren’t the only people bummed out about this so I’d like to share some pics of the Mod.

Hello, I joined this forum just so I could message you! Exactly how much did you cut off (sounds like just under an inch)? I am going to try this tonight. I called magpul and they actually sent me a carbine adapter free no questions asked, going to use this in case I mess it up lol.

 

[trob_205]

Hello, I joined this forum just so I could message you! Exactly how much did you cut off (sounds like just under an inch)? I am going to try this tonight. I called magpul and they actually sent me a carbine adapter free no questions asked, going to use this in case I mess it up lol.

Yea I think you could take it right to an inch if you wanted to. It was a pretty easy job. Good luck!

 

[rsb]

I have a Gen2 PRS and a Gen3 PRS and I see how the Gen3 is a bit longer. Add the folding stock part and we run too long for my short ass.

The Magpul PRS Gen3 comes with a rifle length and a carbine length of pull adapters. The carbine length is about an inch shorter on the PRS stock exterior measurements. The pictures you show appear to be the carbine length of pull adapter. Which adapter is this before the cuts? Where did you make the cuts?
Perplexed in Poughkeepsie, Nope.

 

[trob_205]

The adapters that came with my gen 3 stock were the exact length carbine or rifle. In order to get less length you need to mod carbine adapter.

 

[rsb]

My carbine adapter is a bit shorter than the rifle. Maybe a 1/2 an inch or so. The notch is larger on the carbine.

 

[rsb]

"in order to get less length you need to mod carbine adapter. "

OK thanks.

 

[westford86]

Obviously with a bolt gun you don't have to worry about the spring and buffer, so you could get even shorter if you chopped the tube. I am supposing this as I don't have first hand experience with a Gen 3 yet; from what I have gathered it's secured via pinch bolt to the buffer tube.

Someone correct me if I am wrong, but the Gen 3 PRS is also compatible with A5 buffer tubes. What I am wondering is, just how short can you go via modifications on a semi-auto where the buffer tube must remain intact. I swear by the A5 system for the AR platform, so I want to avoid going to a carbine buffer on a smi-auto .308 build, so I want to know just how much room for shortening there might be? I prefer shorter LOP than most people my height. Does anyone know how much depth there is for the buffer tube?

 

[Viper X]

Obviously with a bolt gun you don't have to worry about the spring and buffer, so you could get even shorter if you chopped the tube. I am supposing this as I don't have first hand experience with a Gen 3 yet; from what I have gathered it's secured via pinch bolt to the buffer tube.

Someone correct me if I am wrong, but the Gen 3 PRS is also compatible with A5 buffer tubes. What I am wondering is, just how short can you go via modifications on a semi-auto where the buffer tube must remain intact. I swear by the A5 system for the AR platform, so I want to avoid going to a carbine buffer on a smi-auto .308 build, so I want to know just how much room for shortening there might be? I prefer shorter LOP than most people my height. Does anyone know how much depth there is for the buffer tube?

So I’ve really liked the Magpul PRS gen 3 stock on my 6.5CM RPR, but it has one major draw back. It’s LOP is shortest possible measurement is 15”. My AICS chassis 700 is set up for me right around 14”. I’ve contacted Magpul twice in the matter and get the same “we don’t currently offer any shorter butt pads for the Gen 3 at this time”. Cool story, but not what I was looking for. I love the feel and love the adjustable butt pad, but I was just about ready to give up and prowl for a PRS gen 2 or the LMT Precision Stock. I really didnt want to give up the adjustable butt pad. So after me and a buddy both in the same predicament. He found a buried thread on M4carbine about a guy chopping his carbine tube adapter in his Gen 3. Wheels started turning on how to cut it and I ended up here. The cut landed me just a hair over the 14” mark ??. You could take it lower but you would have to modify the carbine tube stock adjustment lug channel from the back end from what I saw. The stock still locks up very tight on the tube with no real compromise of it potentially sliding after being altered (my buddy and I both pulled really tight on the stock with just the rear screw tight and couldn’t get it to budge. So the QD slog mount screw only made it tighter!) When the Gen 3s first became available I saw a guy on the RPR thread asking if there was any alternative to the long LOp. I’m 6’ tall so I figured we weren’t the only people bummed out about this so I’d like to share some pics of the Mod.

What tool(s) did you use to cut the carbine tube adapter?

 

[trob_205]

Ban saw, hack saw, file, and sand paper

 

[Viper X]

Ban saw, hack saw, file, and sand paper

Thanks.

What extension tube did you use? Messing with this right now and the rifle length tube is too long. Will a carbine length tube work?

 

[trob_205]

Yup. Used carbine tube for mod

 

[Viper X]

Yup. Used carbine tube for mod

Thanks again. How did you screw into the carbine tube? Guessing drilled and tapped it then picked up the proper length screw.....Ace Hardware or ? Any other tips would be appreciated.

 

[trob_205]

Carbine tube is friction locked with sling port and the other screw close to the tube. Only use the rear screw with the rifle length tube. Tried pretty hard to get the carbine one to move with no such luck

 

[Viper X]

Carbine tube is friction locked with sling port and the other screw close to the tube. Only use the rear screw with the rifle length tube. Tried pretty hard to get the carbine one to move with no such luck

Thanks, good to hear. Just seems like the carbine length attachment method was less solid than the rifle length attachment method.

 

[Graybug]

This thread has gotten pretty cold, but I'm about to make this mod. Anyone got any more info or 'lessons learned' about making this mod between late last year and now? . . .

 

[trob_205]

This thread has gotten pretty cold, but I'm about to make this mod. Anyone got any more info or 'lessons learned' about making this mod between late last year and now? . . .

Keep on rocking in the free world. I’ve recommended the process to a few and they have all been happy.

 

[tinman52]

Great solution. I have the same problem. Thanks for posting this

 

[DannC]

I posted just last week in another thread about the same problem. Wish you had made a video of the mods. Thanks for the inspiration.

DannC

 

[Ciaschi123]

Hi guys. I joined the forum yesterday I believe great resource. I recently purchased a savage evolution in 6.5. I was slow to jump into that caliber but I’ve made the leap. I too had a problem with LOP with the prs gen 3. Also because this particular rifle has a full length flat top rail the scope needs to be mounted rather high. With the prs I wasn’t able to get the height I needed to get a good sight picture. I made 3 mods to the prs/ rifle to accomplish both. First I took about an inch off the adaptor like the post said. That got me the perfect LOP. The second was I cut the buffer tube to be out of the way of the riser. When you lift the riser on the PRS it stops when it makes contact with the tube. I gambled on weather or not it would have the stability after taking a couple inches off the tube. Granted I haven’t shot it yet but it feels rock solid in the shop. This got me a TON more elevation on the cheek rest. The third mod was to the retaining QD screw. Actually the two adjoining parts to it. I shortened the smaller one to give a little more clamping power when I attached it. Here’s a couple pics. I hope this helps anyone in my shoes wondering what to do. Thanks fellas.

 

[Macmathews]

Nice work guys,
With respect to gaining (or losing LOP) even a little more there has to be some kind of option or alternative for the butt pad ?

Kyle

 

[Infantry01]

I don’t understand why Magpul would change one of their biggest products based on adjustability and make it less adjustable (ie. too long of lop).

 

[TRG65]

I cut mine almost back to the flush cup and it was still a bit longer than I would have liked. I went back to the stock rpr buttstock. I have a gen 2 on my AR10 and have no issues. Even added the thicker recoil pad on that with no issues.

 

[Tx_Aggie]

I don’t understand why Magpul would change one of their biggest products based on adjustability and make it less adjustable (ie. too long of lop).

PRS stocks have always been extremely long. This is because it's designed to add adjustable LOP to a rifle with a rifle buffer system (the stock has to be designed so that it's longer than an A2 rifle stock).

The gen 3 is really the first that is a candidate for this sort of modification, since it's the first that can also be mounted on a carbine buffer tube. Gens 1 & 2 had to be mounted to a rifle tube and so weren't as easy to modify.

 

[EzGoingKev]

I have a PRS Gen2 and had been thinking about shortening it. After looking at the Gen3 I think I am going to upgrade to one once pricing drops back to normal.

When I was looking I did find this shorter rifle tube from a company called DoubleStar. I do not know anything about this company so I cannot comment on their level of quality.

A1/A2 receiver extension = 10 1/8"
DoubleStar AR381 receiver extension = 9" 7.5"

I was thinking I could shorten the Gen2 whatever I could and make a spacer to make up the difference.

ETA - Doublestar's AR381 receiver extension is actually 7.5", not the 9" they originally told me.

 

[Samuel Whittemore]

@trob_205 @FromMyColdDeadHand

Wondering about buying one of these for my Ruger precision rifle. But not if I have to go make all the modifications (no shop per se to make the hack) So may I ask... what's your height? Dress shirt sleeve length? Knowing that could help gauge if it's a fit.

 

[combatgrunt84]

Blast from the past I have a 6.5CM does it matter if it’s an ar10 or ar15 buffer tube

 

[daved]

Buffer tubes differ only in diameter - mil spec vs commercial - and length - carbine or rifle. None are specific to AR10 or AR15.

 

[combatgrunt84]

Oh thanks I’m assuming a commercial then for a factory rpr

 

[daved]

Sorry, not familiar with RPR. Suggest you start a new post in semi-A guns and ask. You should get plenty of responses as to the specs of the RPR buffer.

 

[combatgrunt84]

Thanks for the help

 

[AXMC]

The RPR is a standard mil-spec tube.

 

[combatgrunt84]

Awesome thanks

 

[trob_205]

@trob_205 @FromMyColdDeadHand

Wondering about buying one of these for my Ruger precision rifle. But not if I have to go make all the modifications (no shop per se to make the hack) So may I ask... what's your height? Dress shirt sleeve length? Knowing that could help gauge if it's a fit.

Damn sorry I just saw this. Probably a waste to reply but just in case, I’m 5’11” not sure on dress sleeve length honestly. If you’re into archery I have a 30-30.5” draw length lol

 

[combatgrunt84]

What barrel but took did y’all use my buddy tried both of his and they didn’t line up

 

[trob_205]

What barrel but took did y’all use my buddy tried both of his and they didn’t line up

I guess I’m not sure what you’re asking?

 

[combatgrunt84]

We tried two different barrel nut tools sorry my voice to text and cell phones suck at typing. I was able to get it off of the brass punch

 

[VinnyHM3]

I just put a Magpul Gen3 prs on my rugar and I actually like the LOP. My only question is the screw that go under the buttplate doesn’t bite into anything. Not sure if that’s a problem or not. I think the buffer tube is just too short. Anyone have any knowledge on that?

 

[AXMC]

Yes, that screw is for use on a rifle length buffer tube that reaches the end and is threaded for it. However, a carbine length tube (like on the RPR) is too short, isn't threaded and doesn't need it.