Magpul PRS - WTF?

[judgedelta]

I recently got a Rock River Predator Pursuit that had been pimped a little and which sported a Magpul CTR. Needing more eye relief, since not much is furnished by the 6-inch rail on top of the receiver, I put on a rifle tube, spring, buffer and an old A-2 stock I had in a drawer. Rifle was better, shooting less than an inch at 100, but still couldn't get far enough back for full eye relief with the stock in my shoulder, so I opted for a Magpul PRS. Found one on the Left Coast and had it shipped in. Upon installing, it was tight on the tube. A little oil solved the problem and went out to shoot with same reloads I'd been getting about half or three-quarter inch groups, when I did my part. Now I am getting about one and a half inch groups (regularly) and it is shooting about 2 inches low and right.

I am familiar with the PRS since I put one on my LMT MWS with absolutely no problems.

I guess I'll take it off and start over, but has anyone else experienced this with an AR?

 

[gunfreak101]

That is crazy I have never had anything like that happen.

 

[Regalkismet]

Instead of changing the stock to get more eye relief maybe you should have just changed your scope mount to an offset scope mount which will effectively move your scope further forward over the forearm.....which IMHO is the better way to acquire proper eye relief and comfort with non monolithic uppers on AR style rifles ..Especially if you don't want to restrict access to the charging handle any more than necessary . I've never heard of such issues with the prs stock but I'm an ubr fan.

 

[bluto77]

Is the tube the correct size? If the PRS is mil-spec, then the tube has to be as well. Same with commercial. I can't remember which one is bigger, but I think out would be possible to install the PRS over the smaller wrong size tube, which may allow for too much wiggle, and open up your groups.

 

[judgedelta]

Is the tube the correct size? If the PRS is mil-spec, then the tube has to be as well. Same with commercial. I can't remember which one is bigger, but I think out would be possible to install the PRS over the smaller wrong size tube, which may allow for too much wiggle, and open up your groups.

Tube is mil-spec; came from Bravo company. It is tight, hence the oil... Maybe too much torque on the screw?

 

[bluto77]

I guess my reading comprehension sucks.

Could have something to do with the weight of the buffer, strength of spring, and/or the combo of the two. If different than before, it could be changing the way it recoils. Maybe you're just not used to the new recoil impulse.

 

[dang472]

There is only a difference in buffer size with the 6 position carbine tubes. There is no Commercial/Mil Spec with a rifle-length buffer tube. You went from a carbine buffer and spring to a rifle spring and buffer. It will probably cause a minor effect on your go-to load. You've also changed the way you shoulder the gun and your cheekweld. I imagine all of these small changes added up to a difference on paper. FWIW, I would expect the PRS to be tight on the tube, it's supposed to be an extremely stable platform for precision shooting. A sloppy stock fit is a no-no.

 

[judgedelta]

1. Changed the tube, spring and buffer. Put an A-2 stock on. Shot FINE (way less than 1").. Shooting off bench, need more stock length to get long nose off of charging handle.

2. Took A-2 off, put PRS on; went to crap....? Still need more length for eye relief on scope (Swaro 3X18). Have rail extender on order. Thanks everyone.

 

[Laseredge]

Loosen the two screws that hold the front sling loop and the stock will slide on more easily. Retighten once installed.

 

[ORD]

Loosen the two screws that hold the front sling loop and the stock will slide on more easily. Retighten once installed.

^^ +1 on this!! ^^

Its a known issue with the PRS stocks that the two cross bolts that secure the sling loop that runs parallel to the stock body get torqued down VERY tight from the factory. I have not installed one in years (a few dozen) that slid right on the receiver extension without need for loosening those two bolts first then re-torquing/tightening them after the stock body was secured.

As for your accuracy woes...it could be a number of factors, but I'm betting your inability to get an ideal position on the rifle in terms of your body's fitment and eye relief/scope placement (and perhaps some parallax issues to boot) is the culprit. Wait until you can get the scope mounted properly and then reassess.

 

[338RUM runner]

Thanks for the tip on the cross bolts.

 

[jdr724]

Maybe? The screw used to secure the stock to the tube under the butt pad has a small hole through the center, does yours?

 

[bluto77]

Post a picture of your rifle with the scope and mount in view. Seems like you're needing to get excessively far back behind the scope to get enough eye relief. Based on what I'm understanding you to say, it sounds like another option would be to move your scope forward.

 

[Regalkismet]

That's basically what I was saying in post #3..... Btw op many people shoot nose to charging handle or fairly close to it, unless it's uncomfortable for you, its a very common and effective way to shoot ar platforms. All that's needed is an offset scope mount.

 

[Palehorse68]

FYIW
I switched from a UBR to a PRS on my LWRC REPR and noticed an improvement on my shot groups.

 

[mdmorrow]

I've only had good luck with PRS stocks. I don't try to nose forward on it like I would on a carbine though. Just stick your cheek on the pad and position your scope on the rail accordingly. I wouldn't think you would be in need of a forward extension.

 

[samnev]

I have the PRS on 3 308 rifles (LMT, DPMS SASS and an Armalite) and have not noticed any accuracy problems. I am with the others that suggest perhaps you are nor getting proper eye relief or not positioning you check on the stock at the same position on the PRS for every shot. It took me a while to get the proper position nailed down.

 

[mdmorrow]

I have the PRS on 3 308 rifles (LMT, DPMS SASS and an Armalite) and have not noticed any accuracy problems. I am with the others that suggest perhaps you are nor getting proper eye relief or not positioning you check on the stock at the same position on the PRS for every shot. It took me a while to get the proper position nailed down.

I would agree, you cheek position is probably different than what you've been used to.

 

[Strykervet]

I would agree, you cheek position is probably different than what you've been used to.

Yep. Because that stock isn't gonna change how the rifle shoots, not really or enough to measure, but it will/can change how you shoot the rifle considerably.

 

[judgedelta]

I'm not good at pictures. Here is the stock and scope. As you can see, the scope is about 2 inches back of the charging handle. Can't go any further forward...

<a href="http://s1186.photobucket.com/user/derekeparker/media/photo2.jpg.html" target="_blank"><img src="http://i1186.photobucket.com/albums/z362/derekeparker/photo2.jpg" border="0" alt=" photo photo2.jpg"/></a>

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[Regalkismet]

I really think an offset scope mount would really help you get proper eye relief and comfort.....I think scope could go forward a couple inches.... Albeit everyone has their preferences and what feels comfortable and repeatable but IMHO scope is way too far back and trying solve anything till that is corrected is mute. I generally keep my scopes a hair forward of the charging handle, but that's what is comfortable for me using UBR stocks and I don't like my charging handle obstructed anyway. Is there a reason you don't want to use an offset scope mount? IMHO it's the proper way and most common way to solve this issue. Your accuracy issue could be the simple fact you changed the way you were looking through/positioned on the scope.... Being consistent with that is important, so having everything set up properly and being comfortable is critical.

 

[FrozenRopes]

A lot could have happened.
My guess is something came loose or was bumped while you were installing the stock.
I would check all the screws and nuts on the system. Start with the scope, most of the time that's the issue.
It doesn't make sense that just a stock would have that much effect on accuracy. Check to make sure you didn't bend the buffer tube in the installation process. That could definitely change consistency.

 

[judgedelta]

I loosened the screws on the sling loop "footman's loop" and took the stock off and put it back on and tightened the screws back up, firmly, but not as tight as possible. Will try this PM and report back. If that doesn't work, I'm going to put the A-2 back on it and try again. Thanks all...

 

[FrozenRopes]

I really think an offset scope mount would really help you get proper eye relief and comfort.....

That or just move that rear ring up a half inch on the rail and slide the scope forward more.
That back ring is real close to the ocular bell anyway.

 

[ORD]

The tightening/loosening of the sling loop screws will only effect installation/removal and how difficult (or impossible) it is to accomplish either one. It won't do ANYTHING with respect to accuracy, etc.

Seeing your pics...that scope is WAAAAYYYY too far back for 99% of the populace to get a proper (much less comfortable) position on that rifle. Even assuming you only have as little as 2.5" of eye relief (which I'm betting its more with that Swarovski), you are all sorts of out of position. You can probably buy yourself an addt'l 3/4" or so of forward positioning of the scope by moving the rear ring forward a few slots and sliding the scope forward in the front ring so that its almost touching the turrets, but that's still not going to be enough in my opinion/experience. You really need to offset/cantilever mount to get the scope's eyepiece up to where is probably should be for most people (as in the back of the eyepiece hovering roughly even with the CH...not 2" behind it).

 

[Regalkismet]

Thanks ORD.... I mentioned this in the 3rd post and I'm feeling ignored for trying to help.....lol

 

[mdmorrow]

My rifle is set up in a similar fashion. I've got a Larue LT104 for a forward mount and I have my eye piece about even with the charging handle. Seems to be about right for the PRS cheekpiece.

 

[bluto77]

Check out my mount. It's a Burris PEPR. There are definitely more expensive and better ones available, but you get the picture. My scope is only about 1 inch further forward than yours (if that), but key in on where it is attached to the receiver, and you'll see that I could move the entire mount a good 3 inches forward. You obviously have very long arms, so such a forward mount may be what you need.

 

[judgedelta]

Thanks guys. All good advice. I just got my offset mount from Yankee Hill ( rather buy yankee than chinese) and will be trying it out shortly...

 

[judgedelta]

After putting the stock back on (reading the instructions sometimes helps), and getting enough eye relief, she's gone back to shooting some better. All I need now is some practice. Getting some horizontal dispersion, need trigger control. Thanks all for the help and encouragement.

<a href="http://s1186.photobucket.com/user/derekeparker/media/photo2-1.jpg.html" target="_blank"><img src="http://i1186.photobucket.com/albums/z362/derekeparker/photo2-1.jpg" border="0" alt=" photo photo2-1.jpg"/></a>

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[ORD]

That looks like a big improvement to what you explained you were experiencing before now that you've gotten your scope mounted better/have the rifle better fitted for you. Glad you are getting it sorted out.

One more thought...at some point in time, you might want to get some lower rings. They were probably ok when mounted direct to the receiver rail, but now that you've added the riser, your optic is mounted pretty high (even though you can compensate for it somewhat with the cheek riser on the PRS).

 

[mdmorrow]

That looks much better.

 

[mdmorrow]

Those are really high. There's already some height in the base.

 

[303_enfield]

Are you using a chin weld? That setup looks high as hell. Look at the black rifle thread and find a better set up if that one give you problems.

Good luck!

 

[judgedelta]

No problem with the cheek weld. As you can see, I have barely raised the riser. I do have a little too much eye relief, maybe 1/2 inch and will come back next time. Will take some tuning... Thanks again everyone.

 

[sawman556]

I use the ADM recon x mounts on my AR's. Larue also makes a extended version of their LT104. IMO, it would be worth the investment to switch over from your current set-up.

 

[Downzero]

You do realize that with proper cheek weld, that stock length has no bearing on eye relief, right?

If you're shooting with your nose on the charging handle, a longer stock won't get your eye further from the scope.

 

[judgedelta]

What do you do if your nose is on the charging handle and the stock is 2 inches from being in your shoulder? I have a problem in steadying the rifle without my shoulder in the stock (or the stock in my shoulder). I'm also having problem with my pistol grip, which feels like its about 3/4 inches wide; like the grip on my Ruger LCP. I'm use to a wide grip like on a double stack Glock. Any suggestions?

 

[okiefired]

Brother, I just cant imagine you getting proper check weld with a scope that high (even on an AR).....and I noticed you have your check piece raised to boot. Another thing I dont care for on that is how much of the front of the entire set up is unsupported. It looks like there is only about 2" of your riser/rail that is actually supported by the flat top, thats a lot of unsupported weight out front. Several manufactureres (i.e. G,G&G) make very strong duck billed riser/rails that clamp the entire length of your flat top and give you every bit that much extension forward. An Armalite one piece AR mount is all it took to put my scope even with the rear of the charging handle on my AR10T. There's no reason to worry about accuracy until you're sure your set up is solid. Good luck with it

okie

 

[ORD]

What do you do if your nose is on the charging handle and the stock is 2 inches from being in your shoulder? I have a problem in steadying the rifle without my shoulder in the stock (or the stock in my shoulder). I'm also having problem with my pistol grip, which feels like its about 3/4 inches wide; like the grip on my Ruger LCP. I'm use to a wide grip like on a double stack Glock. Any suggestions?

If you like the texture/feel of your current Ergo grip aside from the dimensions...check out the Ergo Tactical Deluxe grip which has palm swells on both sides and is a good bit wider than the basic A2 grip and the basic Ergo you have now.

As for the stock length...if you REALLY need almost 2" more inches of LOP to get setup on the rifle correctly and comfortably, you are going to have to go at it from both sides of the stock. First, Magpul makes an extended buttplate that will buy you an extra 0.5" or so. From there, you are going to have to add length to the receiver end with something like the following add-on: DPMS Buttstock Extender 1 AR-15 Aluminum Matte

 

[gunfreak101]

Go talk to the guys at larue Tactical and get yourself self a lt104 it will be the best money you have spent on your rig. Having a bad mount on a good scope is like having street tires on your 4x4 when the roads muddy it just does not work to well.

 

[judgedelta]

Thanks. I've got the Ergo Tactical deluxe grip on the way... The Yankee Hill offset mount seems very stable and I'll try it for not. I'll keep the suggestions in mind if it doesn't work out. Thanks, all...

 

[Downzero]

What do you do if your nose is on the charging handle and the stock is 2 inches from being in your shoulder? I have a problem in steadying the rifle without my shoulder in the stock (or the stock in my shoulder). I'm also having problem with my pistol grip, which feels like its about 3/4 inches wide; like the grip on my Ruger LCP. I'm use to a wide grip like on a double stack Glock. Any suggestions?

The PRS has an adjustable length of pull, that may help. My McMillan stocks have adjustable systems as well, so I was able to dial in my own rifles to my preferred length.

I would be very surprised if you needed a stock that long. I am a tiny guy so I prefer shorter stocks (my M1 Garand is perfect; men were shorter then). The M16A2 stock, on the other hand, is very long. That's not to say that I can't shoot it comfortably, but a shorter stock is preferable, if available.

There are a TON of pistol grips available for ARs and most of them are quite cheap; i'm sure you can find what you need.

Either way, you gotta get that scope much further forward and get a proper cheek weld. Without proper cheek weld, you will never have consistent groups. Cheek weld is one of the principles of marksmanship. There is no substitute for proper cheek weld.

 

[mdmorrow]

Go talk to the guys at larue Tactical and get yourself self a lt104 it will be the best money you have spent on your rig. Having a bad mount on a good scope is like having street tires on your 4x4 when the roads muddy it just does not work to well.

X2

Thats what I've got on my GAP-10, awaiting a scope right now but it'll settle the eye piece right over the CH or just a hair in front of it as it I'm planning. I've got them on other rifles as well. They're awesome.

 

[bluto77]

Is that mount all one piece, or is it a rail extension with rings attached to it? If you have rings on top of it, then you need to get shorter ones. That scope is sitting incredibly high. I'm sure you don't want to go out and spend even more money on this, and you've already said you'll keep the Yankee Hill mount for now, but you're not going yourself any good if you're trying to force a fundamentally unsound set up work. What size is the tube on that scope? I may have some extra rings you can borrow to see if it works any better for you.

 

[Regalkismet]

I too think you should cancel the Yankee hill order.... Buy once cry once....

 

[sentry1]

There is no substitute for proper cheek weld.

Yes there is. DUH.