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Thanks. They have a shorter rail with the QD mount. Do you think that would work just as well as what you have?

The PMM mount is well made and I wouldn't have an issue running it in the rear/top config or maybe even slightly forward. The MS4 sling is nice as well. I should have gotten these instead of MS3's from a few years ago. I have a bunch of them with the claw on QD-sling mounts, and the MS4 setup is far cleaner.
 

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Thanks. They have a shorter rail with the QD mount. Do you think that would work just as well as what you have?

The PMM mount is well made and I wouldn't have an issue running it in the rear/top config or maybe even slightly forward. The MS4 sling is nice as well. I should have gotten these instead of MS3's from a few years ago. I have a bunch of them with the claw on QD-sling mounts, and the MS4 setup is far cleaner.
It should work fine but just be aware that the 6 slot rail has the thick offset pretty much built into the rail body, doesn't give you a choice/options there. The reason I went with the 9 slot was to get the QD as far forward as I could and have some options as to how far it stuck out from the body.

I like the MS4 (it's what I have connected in those pictures). The front mount, is pretty much set, I'm happy with it. The rear I'm still working on, I've got it set to the top rear most bolt position at the moment.
 

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Yea I have the MS4 as well. I didn't realize Damage Industries might be the same person that ran Critical Dimensions. I had his front rails for over 10 years, they were well made!
 

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Yea I have the MS4 as well. I didn't realize Damage Industries might be the same person that ran Critical Dimensions. I had his front rails for over 10 years, they were well made!
Never heard of Critical Dimensions. I have had my Damage Industries 9 slot QD rail since 2014 and have no complaints. The fitment is good, the finish is good and has held up. When I bought it I was using a 1 point buckle attachment system sling but thought I might switch over to QD later down the line. The buckle type setup worked well for single point but 2 point was a bit of a mess in the front attachment area as the buckles were fairly large compared to QD.

I went ahead and ordered a second PMM QD cup. The cup is so small it's not really a big deal to just add a second cup to the mid section that is more optimal for single point. QD is meant to give the user flexibility and easy movement of setup/configuration, I might as well make use of it by having an anchor point that works well for 1 point and another for 2 point.
 

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Never heard of Critical Dimensions. I have had my Damage Industries 9 slot QD rail since 2014 and have no complaints. The fitment is good, the finish is good and has held up. When I bought it I was using a 1 point buckle attachment system sling but thought I might switch over to QD later down the line. The buckle type setup worked well for single point but 2 point was a bit of a mess in the front attachment area as the buckles were fairly large compared to QD.

I went ahead and ordered a second PMM QD cup. The cup is so small it's not really a big deal to just add a second cup to the mid section that is more optimal for single point. QD is meant to give the user flexibility and easy movement of setup/configuration, I might as well make use of it by having an anchor point that works well for 1 point and another for 2 point.
I got my Critical Dimensions rails in 2007 and I think they were on close out sale at that time. I remember because he was based in Mishawaka IN and I see Damage Industries is there as well. I ordered a second PMM cup as well. I'm still waiting on EA to ship out their set. I'll try them out and see what I like.

I never liked the Urban ERT setup because of all the fastex buckles and webbing that would rub on the stock/receiver.
 

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I got my Critical Dimensions rails in 2007 and I think they were on close out sale at that time. I remember because he was based in Mishawaka IN and I see Damage Industries is there as well. I ordered a second PMM cup as well. I'm still waiting on EA to ship out their set. I'll try them out and see what I like.

I never liked the Urban ERT setup because of all the fastex buckles and webbing that would rub on the stock/receiver.
I'm going to guess that you'll get your second PMM shipment before your EA shipment.

The buckle system were fine but as things evolves, something better comes along. Slings and gear is probably one of those things that evolve as we do, in 6 years, the MS4/QD might get replaced by something else. I do appreciate the simplicity and compact nature of the MS4/QD though.

Years ago, I had seen an MS4 clone with a web loop for the adjustment part, I guess it was based on a much earlier generation Magpul design. Thought about trying it back then as it looked interesting but didn't want to bother with cheapy made stuff. Recently saw some YouTube videos that pointed out they were Magpul clones so that's what got the ball rolling to replace the sling system.
 

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My second PMM QD cup came. I tried different positions but didn't like them. I also got the Damage Industries QD rails (the 6 and 9 inch models) but couldn't find a rear sling position I liked. The rearmost worked for the most part until I got the sling buckle/sling jammed into my collarbone during testing. It just gets in the way. If I moved the cup forward 1 spot (right behind the mag release), I'd get jabbed in the cheek if I wasn't paying too much attention. The EA parts are finally shipping but the PMM QD cup front position gets in the way of the charging handle so I imagine the EA setup will get in the way as well.

I think I'll go back and stick with the Spectre sling. It's low-tech and not the best single point setup but it's lighter than the MS4 and doesn't get in the way when I am using the PS90.
 

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My second PMM QD cup came. I tried different positions but didn't like them. I also got the Damage Industries QD rails (the 6 and 9 inch models) but couldn't find a rear sling position I liked. The rearmost worked for the most part until I got the sling buckle/sling jammed into my collarbone during testing. It just gets in the way. If I moved the cup forward 1 spot (right behind the mag release), I'd get jabbed in the cheek if I wasn't paying too much attention. The EA parts are finally shipping but the PMM QD cup front position gets in the way of the charging handle so I imagine the EA setup will get in the way as well.

I think I'll go back and stick with the Spectre sling. It's low-tech and not the best single point setup but it's lighter than the MS4 and doesn't get in the way when I am using the PS90.
The front mount position issue was why I decided to do the QD on the rail, any of those bolts up front are just too close to other more important things. The other choice would have been to rig something up to the barrel but that wasn't something I wanted to do. This was why I did 1 point in the beginning.

For the rear mount, the bottom 2 point (bolt next to the horizontal slit and bolt behind case ejection port) is probably what I will end up settling on. It's pretty close to the location used for the Urban-ert sling. The top rear doesn't get in my way but I can see how it could while the one near the mag release was never an option for me as that position is too close to my cheek.
 

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For the rear mount, the bottom 2 point (bolt next to the horizontal slit and bolt behind case ejection port) is probably what I will end up settling on. It's pretty close to the location used for the Urban-ert sling. The top rear doesn't get in my way but I can see how it could while the one near the mag release was never an option for me as that position is too close to my cheek.
OK, now I understand what you had meant by the bolt not being long enough. I measured the bolt forward of the one by the slot, and it needs to be a 1.5" long M4x0.7mm black oxide stainless socket screw, which isn't readily available. There's either 35mm or 40mm (too short or too long) in non-black oxide. I'll have to dig further to find one. The one closest to the slot would sit on the chamfered part of the stock and isn't totally flat.
 

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OK, now I understand what you had meant by the bolt not being long enough. I measured the bolt forward of the one by the slot, and it needs to be a 1.5" long M4x0.7mm black oxide stainless socket screw, which isn't readily available. There's either 35mm or 40mm (too short or too long) in non-black oxide. I'll have to dig further to find one. The one closest to the slot would sit on the chamfered part of the stock and isn't totally flat.
Yep, that's what I'm still working on. PMM probably never thought of those locations as a mounting possibility or they would offer a bolt for them. They only offer a bolt for the center part (the handle part) and that bolt is obviously too short being 1 1/16 inches (or about 28 mm). The factory bolt for the location just rear of the case ejection (what I'm thinking as my ideal spot for a 1 point QD cup location) is 1 3/8 inches (or about 35mm), which is too short for the PMM QD cup. PMM obviously didn't test that location as their instruction points the user to use the factory bolts which is too short by a few millimeters. What I plan to do is buy a 40mm bolt and just cut it down to 38mm, very easy to do using a Dremel. I haven't found the exact black oxide coated bolts but I have found a cheap alternative to test with.


The picture they used is a stock image and the actual bolt is probably the unfinished steel. I ordered those last week and still waiting for it to come in via snail mail.

As for the other location (near the slot) that I plan to move the 2 point QD cup down to from the top rear bolt location, that actually looks easier out of the 2. Because that location is slightly slanted, I'm thinking of just leave the factory bolt nut in place and just use a longer bolt than the factory 35mm. The PMM screw shaft is a little less than 3mm and the factory nut is slightly less than that. Both combine is slightly over 5mm which is about the depth of that cavity so it should be a tight fit with the slant portion not having an affect of functionality, it just won't look flush of course. A 40mm bolt looks like it might just fit without any mods. If not, it would need to be a 45mm cut down to 41mm or possibly 42mm. I ordered that size just in case.

The funny part in all this is if the PMM thread shaft was almost twice the length (5mm) instead of the 2-3mm it is now, these problems wouldn't exist. We would be able to just take the nut out and just screw the factory bolts to the cup. Far more of the threads would be engaged that it wouldn't be a point of doubt in my head for the longevity of this mount. That cavity on the PS90 body is about 5mm deep and they're using a thread depth that only goes down 3mm. The factory bolt is too short and the PMM thread shaft is not long enough. It mounts, but it's not a secure mount as only a couple of those threads are actually being engaged. To be honest, I'm not completely confident even the other location they suggest would be secure long term or through active use. Because the thread shaft on the QD cup is so shallow, even that top rear mount location doesn't fully utilize all the threads with the stock bolts. Granted it's more threads than the bottom location but it's still just 1 mm of threads (out of the 3 mm available). The picture below is with the stock bolt and you can see how much of the thread is left unused. As the product is now, you need longer bolts at all mounting locations for a truly secure mount. The product could use a revision to a longer 5mm thread shaft on the QD cup IMO and since this is something they machine themselves, would be something they could do, probably easily.

144951

144952
 

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Be careful if you use that position near the slot. It's not fully seated so it will dig into the plastic stock.

A 40mm bolt may work without having to cut it. I used my caliper to measure the delta between being flush with the stock and the factory bolt for the position just forward (near the ejection port) and a 1.50" length bolt would be perfect.

The OEM/factory screws are black oxide 18-8 stainless. I can't find any in M4-0.7mm x 40mm length. It's either stainless plain finish or black oxide steel.

I never thought to check Home Depot as I already ordered them from McMaster.
 

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Be careful if you use that position near the slot. It's not fully seated so it will dig into the plastic stock.

A 40mm bolt may work without having to cut it. I used my caliper to measure the delta between being flush with the stock and the factory bolt for the position just forward (near the ejection port) and a 1.50" length bolt would be perfect.

The OEM/factory screws are black oxide 18-8 stainless. I can't find any in M4-0.7mm x 40mm length. It's either stainless plain finish or black oxide steel.

I never thought to check Home Depot as I already ordered them from McMaster.
I used Home Depot because of the free shipping.

For the location near the slot, the stock hex nut would need to be used to stabilize it due to the slant, the nut is pretty well anchored to the weapon body so that's a plus. The QD cup is pretty much just threaded to the tip and since the cup thread shaft sits directly on the hex nut, it's very stable as is, it just doesn't look it. The pictures above is with the cup just hand tighten onto the factory setup as a test fit. It's very stable but just isn't symmetrically flush looking which is less of a concern for me than structural stability. The only thing that mount needs is longer bolts to engage all of the threads.

For the location near the case ejection, I'll probably just leave the hex nut in place too. There's really no point to take it out since the PMM cup doesn't fully reach all the way down the 5mm cavity nor is it as stable in that cavity just by itself. Having the cup sit right on the nut and still be flush is just more reason to leave the nut in. It's more stable with the nut in place so might as well just leave it.
 

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Just talked to Home Depot about my bolt shipment since my package has been sitting at a UPS facility in Atlanta for a week without any movement, I was told UPS is 10 business days (2 weeks) behind at that location so probably won't be for 2-3 weeks till I get my shipment. UPS has been weird lately, even my local facility has had odd stoppages like that multiple times this past year.

I'll just return the Home Depot bolts when they eventual arrive and I went ahead and ordered some elsewhere. I looked on Amazon and couldn't find any even close. I decided to try eBay before having to resort to McMaster, I'm not a fan of the we'll tell you the total with shipping after we've shipped approach that McMaster takes and they use UPS which means a minimum of $6-7 for shipping a $3 part. I was surprised to find pretty much the same black oxide bolts used on these PS90 and from multiple sellers on eBay. Have a pack of 5 being shipped to me for a grand total of $3.67.
 

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My local HD's all have them in stock. I opted to order from McMaster, yeah their shipping is insane at $6-$7 nowadays. I would have ordered from Grainger but they had only the shiny SS at a higher price for a large bag of them. I'm going to try the PMM's one more time but I'm still not comfortable with the PMM QD cups stressing the stock even though it is flat. I may just stick with the Spectre sling.
 

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My local HD's all have them in stock. I opted to order from McMaster, yeah their shipping is insane at $6-$7 nowadays. I would have ordered from Grainger but they had only the shiny SS at a higher price for a large bag of them. I'm going to try the PMM's one more time but I'm still not comfortable with the PMM QD cups stressing the stock even though it is flat. I may just stick with the Spectre sling.
All my local HD's were pitiful with their selection of M4's which was why mine ended up getting shipped.

What's the anchor point for the Spectre sling? The rear loop slot or similar to the Urban-ert?

Now that I've decided to leave the hex nuts in place and just use longer bolts, I'm a bit more confident about the PMM cups than I was before. When I had removed the nut and basically replaced it as the end point for the bolt, it was a bit iffy since the cup, even though it was flush with the body, didn't form fit/fill into the shell/body cavity like the nut does. I don't know how much force it would take to rip one of those stock bolt/nut from the plastic body but I would imagine that's a lot more force than a sling would put on during typical use. I'd imagined the QD system itself would fail first.
 

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Yeah I normally Home Despot has a horrible selection of bolts but their website shows inventory at all of the local stores. The Spectre Sling uses the slot in the stock with a thick 1" loop, and then the actual sling goes through that loop. Sounds complicated but is basic/simple. In 2006 I made my own with web sling to copy that, but with one mod where I have a Fastex to disconnect the entire sling. I was not a fan of the Urban ERT because of all the webbing/Fastex connectors that would rub on the stock.
 

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Yeah I normally Home Despot has a horrible selection of bolts but their website shows inventory at all of the local stores. The Spectre Sling uses the slot in the stock with a thick 1" loop, and then the actual sling goes through that loop. Sounds complicated but is basic/simple. In 2006 I made my own with web sling to copy that, but with one mod where I have a Fastex to disconnect the entire sling. I was not a fan of the Urban ERT because of all the webbing/Fastex connectors that would rub on the stock.

That one?
 

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Yes that is the one. I’ve eyed that since 2005 and only bought it recently to replace my Homemade setup.
You're worried about ripping the bolt off the body with a sling but you're not concern with using that slot as an anchor point? Early on, I considered rigging up something similar to that using that slot for a sling anchor but never did because I was worried about snapping the slot with too much force. I abandon that idea and dealt with all the webbing and buckles early on. It's was probably an irrational fear since even plastic will take a lot of force, way more than what a sling would normally impart on it.
 
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