I myself have had the same frustrations about the lack of decent sling-mounting solutions for the Magpul PRS stocks that I own.


I also didn't want to destroy the value of my Magpul PRS stock by drilling big holes in it or otherwise butchering up my stock.


I just want an easy way to mount my sling, get it on and off fast, and use the original mounting bolts that came with the stock.


I also wanted a sling mount that would raise the sling a half-inch further away from the length-of-pull knob, so that the sling doesn't interfere and bind with the knob.





So I decided to do something about it:





This is a pic of my AR-10T with a pair of prototype QD sling mounts that I designed and machined myself.


I have been testing these for a while through several different hunting seasons and many range sessions.


The rifle had just barely gotten back from elk season, so it was kinda muddy at the time...











Anyway, they have held-up great, even without any hard-coat anodizing.  No failures of any kind, even through lots of rough terrain, crappy weather, and several hundred (and I do mean hundred) miles hanging off my shoulder.


I have the utmost confidence in these QD sling loop mounts.





Introducing my prototypes:

















The above two pics show that my prototypes are approximately four times the mass and strength over the original.  They are made of 6061-T6 aircraft-grade aluminum (same as the original).





Here are my design efforts involved with the making of these sling mounts:





Here is a split-screen showing my production design solid model and drawing, with a completed production piece on it's machining fixture in the foreground:











On my computer is a split-screen of the production fixture solid-model, with sling loops attached to the machining fixture with mounting bolts.  


In my hand is the complete machining fixture, a production QD sling loop, and the original mounted to the same fixture:











Analyzing the QD fastener dimensions in an optical comparator in order to accurately reverse-engineer the dimensions of the fastener and the ball-bearings in particular:











Pic of some drilled/tapped raw material on the machining jig and I am dial-indicating the jig with an Interapid .0005" indicator.











First-op done with a three-flute aluminum roughing endmill:











Finishing up the second-op:











center-drilling:











reaming after drilling slightly undersized:











At my fingertips and in my palm are some full-radius keyseat cutters I had custom-ground for me...precisely cuts the QD keyseat-groove.


$300 worth of custom-made cutter in this pic...spendy little bastards.  I'll be pissed if I break one of these, I just know it.











Running the corner-round:











After the keyseats are cut and the parts are pretty much finished:











A little teaser for you guys...this tray of parts are going into the tumbler and will be back next week from the anodizers (type 2 mil-spec black hardcoat)























Also...I am just one guy, so I can't make very many.





I have already invested some money in patent attorney's fees and the usual crap that goes along with any endeavor like this.





Makes me wonder why anyone comes out with anything new to the market at all...royal ( and expensive) PITA to do so.





Anyway...there you go.





A solution does exist.





So what do you guys think? (I'm kinda beginning to think that I should quit while I'm behind...)
 

First off, I'm willing to bet that this thread gets locked down quick due to vendor rules on the site since it looks like you are setting up for production.

Second, I'd contact Magpul and say "Hey, I have something I think you'll be interested in".  Sell em on the idea, and start selling them product if possible.

Good job on coming up with a solution and making it someday available to others.

I have to say, you've done an impressive job.

My suspicion is that the QD swivels became popular well after the PRS was released. Now that they're the heat, mounts need to be made.

Cost point is everything and you're surely looking at a select market, but for those in that market, money is probably no object.

That said, I'm thinking about it.

I will be having another meeting with my patent attorney on February 18th...
I will be receiving the first batch of completed second-gen QD sling loops from the anodizers tomorrow at 1:00PM  PST.

I would appreciate some beta-testers...anybody up for it?

I will be sending out 10 pairs of these sling loops this weekend to the first ten people who email me ([email protected]) with their mailing info.
I request that reviewers post their reviews (whether good or bad) to this thread by February 20th.

These sling loops are made from aerospace quality 6061 T6 aluminum.
This is quality US-made aluminum with certified inspection report available from SAPA Industrial Extrusions out of Spanish Fork, Utah...NOT some cheap-assed Chinese mystery-metal.
All threads are form-tapped for maximum strength.
The swivel socket features are machined directly into the sling loop, so there is no glued-in flush-cup to slip out when the glue eventually breaks down.
The swivel sockets now feature a swivel rotation-limiting design
100% US made.

Note: I cannot be held responsible for overtightened (stripped) threads, cross-threading, or failure to use lock-tight (red) during installation.

By the way...while I was visiting the anodizers today, one of the ball-bearings in my VLTOR heavy-duty sling swivels fell out, yet my QD sling loop prototypes are just fine.
Therefore my sling loops have lasted longer than the swivels themselves...

I would defiantly be interested in testing a QD mount for the PRS.  Where do I sign up?

IM sent

email sent

I've been trying to find a way to attach my TAB Gear Sling to my Grendel I use in Practical Precision matches and was just about to give in and drill a hole.

What sort of attachment points do you have on the TAB gear sling?

Email Sent.  

I was going to order a new set of quick swivels.  Please specify which you would prefer I used in the testing.

The the same as what you have in those pics. I got the sling and installed Flush cups in the stock on my Rem 700. I want to use the same sling with my grendel, I have a way to attach the Tab sling up front on my grendel, but no way to attach the sling in the back.


It's basically this sling

Awesome!
My QD sling loops would work perfectly for that application.

I agree, and I would happily post my review over at Snipers Hide also where I bet lots of people would be interested.

Here is a look at the 1st and 2nd Op Jig design:



And the 3rd Op Jig design:



one of my 3rd op jigs in action:





Here is a view of the 50-piece model I designed to machine the QD sling loops with:



Here is a look at one of the 50-piece final op jigs in action:







Here is a pic from the batch I picked up from the anodizers about an hour ago.



These will get mailed out to my beta testers first thing in the morning.

Thanks guys!

Very Nice...need something like this for Magpuls MOE handguard.

[/quote]I agree, and I would happily post my review over at Snipers Hide also where I bet lots of people would be interested.[/quote]

Me too.  Someone should start a thread over there...

ARctangent,

I just got back from an event where we were talking about your PRSQD Sling Attachment Point (PRSQDSAP) for short- kind of for short- and everyone was excited to see it.  For instance shooting from a bench, I always prefer to remove a sling on any rifle.  However with the PRS and a 2 point sling, there are any number of ways to remove the sling from the front stock, but that leaves you with the sling dangling from the butt stock.  Sure one could use the PRS's picatinny rail to add a sling attachment point, but at the least ergonomic point on the butt stock.  Well we are excited to try this out, I'm sure it will work great.  Have you thought of making a similar attachment that could be bolted to the free floated tubular front hand guards often found on precision AR's.  I'm thinking of free float hand guards like the Hogue, and others.  Many of us who use our ARs as precision rifles, hunting p-dogs, chucks and the like, need a sling to hump these heaviest of ARs around.  

Oh, yea I was just assuming that I was on the list, could you please confirm.

Thanks!

Yes, you are confirmed.  Package was sent with two of the QDSL's inside.
Everything went out this morning via USPS first class mail.

Confirming beta-testers:
DasRonin
kingston
JTrusty at Gear Sector
Mudbug
Matt F
GWhipp

Still waiting for a mailing address from PhillipW.

Willing to give a set for testing and evaluation to:

justpete
eracer

If they would shoot me an email with a mailing address and be willing to post a review.

Edit:
justpete and PhillipW now confirmed as of this morning.

This is a good question and deserves further explanation.

Any (heavy duty) push-button sling swivel with a 3/8" diameter shank will work.  
When I initially started this project, I bought five different brands of HD push-button swivels and mic'd then all.
They're all pretty close to .3730" diameter with a tolerance variation around +/- .0005" from nominal.
Wanting the maximum shank and ball-bearing engagement as possible, I sent a few of my prototypes in to the anodizer's.
I wanted to get an idea of precisely how much build-up would occur...the anodizer's advice was correct in that he predicted a build-up of .002" (per side) with a total of .004".
That being the case, I then used a .379" oversized reamer for my socket holes, with a .0004" total anodizing build-up leaves the final dimension at .375".
Which means that the largest QD swivel (.3735" shank diameter) will fit with .00075" clearance (all around), and an nominal sized one (.3730") will fit with a .001" clearance.
Being that the tolerances were so tight, I designed the QD socket feature with a through-hole such that any debri (sand, dirt, and such) can simply be blown-out and not allowed to accumulate.

Here is a pic of one of the VLTOR heavy duty sling swivels with a 3/8" shank diameter (actually .3730" mic'd):

 

Now, the rotation limiting design feature within the socket hole...
It is designed in such a manner that if you insert your QD swivel such that the loop ring is coplanar with your rifle bore axis (i.e. "horizontal" ) you'll have a rotation limit approximately +/- 30 degrees from the "horizontal"



Counterclockwise limit from horizontal:



Clockwise limit from horizontal:



Conversely, if you insert your QD swivel perpendicular to you rifle bore centerline, it will result in a rotational limit +/- 30-degrees from the "vertical":



Counterclockwise limit from "vertical":



Clockwise limit from "vertical":



In addition, this is a Blue Force Gear Female Fastex Adapter with a heavy-duty push-button swivel:



It mic's right on at the .3730" nominal dimension that best fits my QD sling loops:



It drops right in:



So now the Magpul PRS stock can be used directly with a number of Blue Force Gear series of single-point slings, including the SOC-C Sling, the Vest/LCE strap, and the UDC sling.

http://www.operationparts.com/PhotoGallery.asp?ProductCode=CONPAK-OD

http://www.operationparts.com/PhotoGallery.asp?ProductCode=SOC-C-V-CB

http://www.operationparts.com/BLUE_FORCE_UDC_ONE_POINT_SLING_PUSH_BUTTON_BLACK_p/udc-pb-bk.htm

I am not a high-speed-low-drag guy (more of a mechanical engineering geek) but you could conceivably even use a single-point sling in conjunction with a two-point sling...

Allowing you to carry or rest the rifle on the single-point sling, yet allows you to instantly disengage the fastex buckle and go to your two-point or sling:



Combined with any number of pic-rail QD swivel adaptors up front (in this case a daniel defense version) any number of two-point slings can be used, pictured is a Turner Saddlery all-weather national match sling:



But ANY two point sling with HD sling swivel adapters can now be used in conjuction with the Magpul PRS stock, such as the Larry Vickers  Combat Applications sling with two HD QD sling swivels on the ends::

http://www.operationparts.com/PhotoGallery.asp?ProductCode=VCAS-PB-FG

Or the TAB gear sling with the heavy-duty QD sling swivels (my personal favorite sling...LOVE TAB gear stuff from Rifles Only!):

http://www.riflesonly.com/store/TAB/sling_big.html

If you are willing to sell these, I'd certainly like to get a pair of them for my stock.

I'm so glad you mentioned the Rotation limiting design. I thought for sure that would be the first change I was gonna suggest since it's often left out of QD mounts. Nice job of thinking the whole thing through.

Thanks!
I tried to come up with the best design possible...
You'll be receiving your set by the middle/end of the week.

My hope is that:

People who were on the fence about buying a Magpul PRS stock (because of the severely limited sling options) will be prompted to buy them up (lets face it, it is quite possibly the best stock ever designed for scoped AR's).
I foresee a lot of single and two-point slings being sold along with heavy duty QD swivels when news of my parts catches on...

Though it happens all the time, hopefully somebody won't rip off my design and I'll be able to make a few bucks...hell I'd be happy just to break even at this point.

Willing to be a beta-tester?
One last set available.

I am so willing to help you out.... Dam I wish Io had seen this product sooner..... I just bought a UBR cause my PRS did not have flush cups....

Please contact me ASAP and GREAT job love stuff like this.

IM sent.

Got my beta set today in the Mail.  They look great.  The first thing that I noticed was the swivel stop limit milled into the bearing races.  Unfortunately the two QD Sling Swivels that I have are too big and will not fit.  I just place a large order with a bunch of swivels and slings.  I will post pics when they arrive.  Just FYI, the two that I have are not marked, but came with my Beretta Xtema II shotguns, these are the ones that do not fit.  These measure .3740 and the mount measures .3750 on my Mituoyo CD-S6"CT calipers.

ARctangent, check your PMs and Email...

Hmmmm...might  be some funky-sized proprietary QD swivel design from Berretta that I have never seen before...

The swivel-stop milled into directly into the bearing race was a particular PITA to design and machine...I wanted a smooth roll-out of keyseat cutter.

I got the little Beretta bugger in, but it is tight.

.3740" should fit.  .3750" is going to be a little on the tight side.
You might want to try to fully depressing the button with your thumb while holding the swivel buckle with your index and ring fingers.
My QD sling loops were intentionally designed to be a little on the tight side (when new) to account for wear over time...like I said, maximum possible engagement.

ARctangent PM me your regular email and I will send you some pictures.

Just IM'd several responses.

JTrusty at Gear Sector totally rocks!

That is all...

If still avaialble, I'll take them.
You must have not gotten my email a few days ago.

Edwin

I got mine today and got them installed. These things are fantastic. I truly hope you are able to hold onto a patent for this design and sell tons of them or Magpul pays you for the rights to sell them with their stocks.

I will says one minor thing. While the offset design makes it possible to access the LOP adjustment wheel, it does still make it kind of awkward, but that is not the fault of the design, it's just a fact of dealing with the magpul placement of the sling loop, and it's no worse than if you had a sling running through the regular attachment they have. Still, the other side of the wheel is completely clean and free of obstruction.

All of the QD rings I have fit just fine. Most of them are what comes on my TAB sling, or the Uncle Mikes variety both the regular and hefty designs.

Here are just a few initial pics till I get a chance to run my gun iwth these things on it.

Very nice and clean job on the milling and anodizing.


Installed on the stock.


Sling in the rear position.


Sling in the front position.


Sling installed front to back.

For those arfcommers watching this thread I am sending my reports directly to the OP.

I will say this... the quality of workmanship is outstanding!  I am pleased with how my testing is going, and this is a great idea which was well executed.  A couple of minor "tweeks" and it is good to go!

As the OP knows... more tests results to follow, as I have not finished my series.

I appreciate the opportunity to be a part of this review and testing!

You guys are AWESOME!!!!

Precisely the kind of feedback I was looking for!

So happy I did this!

You could sell these with a pattern, screws, and washers and they could be installed on an A2 stock. In fact once I decide which position I want to use on this stock I may install the other one on my SPR which wears an A1.

Not sure if there are any left for beta testing, but if not I would like to get on the list to purchase.

Thanks.

Great pics, Mudbug.  These appear to be very nicely made.
You could certainly mount them on anything, but they look fanastic on the PRS.
My lower with the PRS is a KAC ambi unit, so it has the receiver mounted QD fittings on each side.
But I really need the QD mounts for the stock, 'cause it is one of the few guns I would run the sling from the stock more than from the receiver.

I Mounted these and took the AR out last night and everybody thought these were the cat's ass!  Superbly well made.  The reaction was WOW!  The stops on the bearing races was a great idea!  Pics to follow...

Got mine and tried them out with Daniel Defense pushbutton swivels.  The two swivels I measured mic'ed dead on at 0.3750 using a B&S #1 micrometer and are too big to fit.  Checked a DD rail mount attach point with minus plug gages and got 0.3780 as the best running fit.  I don't have an internal dial caliper like an Interapid but the races appear to be definitely more shallow and narrower on the DD part.  I drilled one of yours out with a 3/8" bit (double checked OD w/mic) and it didn't help since the shank of the swivel increases slightly toward the body so I drilled it out to 25/64" just for the heck of it and of course it's too loose but by allowing the swivel to seat it was possible to get a feel for the tension put on the retention balls by the ID of the raceway.  The DD part seems to keep them compressed a bit more as the button 'feels' harder to push to start the release processusing the same swivel of course but that's a purely subjective result.  FYI.

I'm definatley interested in purchasing these when they are available. Great idea!

Keep us posted.

Wait... you ruined one of yours in order to try and make it fit an out of spec part?

Final test report of the prototype QD sling mounts made by ARctangent.

02/08/2010
Units arrived, initial impressions/visual inspection.

The overall machining and finish is top quality! I have one Uncle Mike's QD swivel and one Daniel Defense QD swivel. The Uncle Mike's fit a touch tight but snaps into place and swivels within the limits of the partial cut races, as designed. However, the Daniel Defense QD swivel fits so tightly it has to be pushed and wiggled with a bit of oil on it to eventually get it seated.

The Uncle Mike's fit is what might be considered barely acceptable if someone bought/ordered one to use, that alone indicated the ID needs to be a touch bigger. The fit with the Daniel Defense QD is totally unacceptable under such circumstances. The ID of the socket is too small and needs to be opened a sight bit.

I moved to Texas a bit ago and most of my tools are still in MO. So as much as I wish I could I would normally get my digital dial calipers and tell you the OD of the swivels to give you a better idea of how much more the ID of your unit needs to be opened.

Wear/fitment test.

Before I intend to mount them to the stock I had planned to do a wear test of sorts.  Each QD swivel was placed in one of the sling mounts.  By hand the swivel was rotated from stop to stop back & forth, limit to limit 100 cycles on each.  After 100 cycles each swivel was removed, reseated and the test continued until 10 cycles of 100 was completed.  At each 1000 cycle point, both swivel and mount was inspected carefully by means of a close visual inspection, and any wear noted.  Each QD swivel was  tested in a different sling mount, and each one was wear tested to 10,000 cycles.

The Uncle Mike's QD was installed dry, and by necessity the Daniel Defense QD was oiled with Machine Gunners Lube I had purchased from LaRue Tactical.  After 1000 cycles each... no wear shown on either unit.  The Uncle Mike's originally fit slightly snug... just slightly.  After the first 1000 cycles, the fit seems to be less snug to the point I would say what I expected originally for such a mount with tolerance stacking of the unit ID and the sling swivel OD being at maximum specs.  The UM QD slips in with very little effort.  However, this tight a fit might be problematic in dusty environments, and is not as "loose" as the same QD swivel going into my Magpul UBR factory stock swivel mount for example.  

As to the Daniel Defense QD swivel... I see no perceptible change in how tight it fit.  Effort must be made to turn the swivel in your mount, where with the Uncle Mikes, holding the mount and watching the UM swivel, it freely rotates under its own weight freely moving either direction stop to stop in the race cut.  With the DD swivel, it must be rotated by hand to get any movement at all, and friction resistance is felt... even with the coat of oil.  It remained to be a tight fit throughout the test.

I continued the rotational limit to limit test.  At the 3k cycles inspection, the oil was removed from the DD QD swivel and the sling mount, and it was further tested dry.  Both the UM and the DD swivels were further tested to 10k cycles.  At 3k the wear has leveled out and no further wear was observed on either sling mount.  On the unit with the UM QD swivel, essentially no wear was shown except for a very very small spot at the limit of the interior race cut.  One has to look hard to see it.  The bluing on the UM swivel shows significant wear, with the bluing worn down significantly.

The unit with the DD swivel loosened up to the point that it did not have to be forced into the unit at about 3k cycles.  No change beyond that was shown through 10k cycles.  The interior race cuts show small spots where the anodizing has been worn through at the limits.  It is very small, and after the 3k cycle point no additional wear was shown through 10k cycles.  There was significant wear on the parkerizing on the DD QD swivel.  Most of the parkerizing was worn through.

At the end of 10k cycles the DD QD was put into the unit used with the UM QD swivel in this test. It fit very tightly and had to be twisted and slightly forced to get it to seat and lock in place.  Basically the same fit issue when it was originally placed in the unit when the rotational testing began.  I was a little surprised as I assumed the parkerizing had worn off the DD QD swivel and any high spots worn down on the OD of this swivel.  I assumed it would fit the same as the one it was tested with, and I was wrong to do so.  The two parts wore together during the 10k cycles of the test.  Apparently the shiny spots in the ID of your sling mounts were high spots that wore during the rotational testing by the unique high spots each of the OD of the individual QD sling swivels.

At this point the units were mounted on the stock.  When I removed the Magpul sling plates I set them back to back with the units you made.  With them held back to back I threaded the screws to determine the alignment/spacing of the two units to determine if the center to center on both aligned.  I was able to screw the Magpul  sling plate and your QD sling mount together with the spacing of the two screw holes matching perfectly.  This indicated the center point between the two screw holes of the unit you made perfectly matched the Magpul specs.

Your QD units perfectly fit the Magpul stock!  Overall you have done an outstanding job on this product.  After slightly increasing the ID on the cut by .002 as you indicated, in my opinion no further changed would be necessary.  You indicated when we discussed the under size of the ID of the sling mount bore, that you were looking into changing the finish on your QD sling mounts.  Changing the finish to a more durable one is taking a step to make a good product even better!  The finish on the QD mounts provided for this test proved to be durable when compared to the bluing and Parkerizing on the QD sling mounts I used in the test.  Where both of those QG sling loops showed significant finish wear, your QD sling mounts showed very little finish wear.

I was very impressed with the overall QC of the QD sling mounts provided to me to test.  A slight change is warranted to the inside diameter cut of the bore of the socket, as we discussed.  With that minor change in your specs, I feel the product is ready to go into production.  This is an outstanding item, and I feel privileged to have been a part of the product testing!

DasRonin

No big deal.

I have been incorporating all that I have learned from you guys and making changes/upgrades to the next batch.

Changes:

1) Going up one size on the reamer...should better accommodate all the different (i.e. non-spec) sizes of QD swivels out there.
2) Sinking the bearing race 40% deeper down into the socket hole...would not  BELIEVE what an effect (net positive!) that does in the FEA (Finite Element Analysis) computation results!
3) Changing the the bearing race rotational stop design from a two-lug to a four-lug configuration, so that all four bearings on the QD swivel are loaded equally.
4) Bead blasting prior to anodizing, more "tooth" for the anodizing and further breaks sharp edges.
5) Changing anodizing companies to one with superior quality control (though they're a bit more expensive, I believe it is worth it).

Apologies for not keeping up with the thread...10 hours a day at my day job and 4-5 hours afterward on weekdays and upwards of 10-12 hours/day on weekends on this project doesn't leave a whole lot of spare time.

I'll try and check in on the thread more often.

No apology needed, unless you forget to let us know how we can purchase a couple when you are through with the R & D.

Keep up the good work.

Oh, I won't forget...just incredibly busy.  
Being a divorced single father of three doesn't help things much either...but I am getting there.
Thankfully, I have some good kids.

Out of spec?  Daniel Defense?  Hardly.  About as in-spec as you can get.  For some time the only mil-spec phosphate coated pushbutton swivels you could buy.  You do know they supply USSOCOM/NSWC with RIS II parts (sole source SOPMOD Block 2) as well as URGs, etc.?

They don't make them, As far as I know there is only one domestic maker of Flush cups and the Sling loops for them and that is GrovTec. So despite the fact that DD makes top quality gear, it's very possible that your Sling loop is either just a mistake or imported from from someone that is making them out of spec.

I would be very interested in these if I had a PRS...I think if I ever do a precision rifle build, I'll know where to get sling mounts.

Good work!