How a stressed memeber trigger module changes the function of a SCAR

[Fox33]

ALCON,

This thread is to answer questions about how a stressed member trigger module (Handl) in conjunction with a metal hinge changes the function of a SCAR (mk.17/17s).

#1 If you can find slow motion video of a SCAR firing from say the 4-5 o'clock or 1-2 o'clock position. I suggest you watch it before delving in. While watching watch the flex of upper receiver while the gun cycles.

#2 What I understand from the Handl guys, is the compression of the recoil spring then impact of the BCG against the base plate of the buttstock is what they call an "elastic collision". Think about slapping ghetto booty, it jiggles. If she is thick enough and you slap hard enough, her back, gut and legs will jiggle a bit too.

Now go slap the ass of a chick who is a gymnast or cross fitter. It doesn't move, it absorbs the slap (recoil). The density of the material and its tighter construction means those jiggles (secondary recoil impulses that eat optics/nvgs) don't have anywhere the same intensity. While they do not disappear completely they are hard to notice.

#3 Going back to #1 the upper receiver is the only rigid part of the gun that actually deals with recoil and not very much. The back end of the gun is all polymer taking the hits of the BCG. The guide rod retaining plate actually can act like a springboard for recoil. The stock base plate being polymer does not help with efficient return spring action. The polymer trigger module does not put any reward pressure on the baseplate nor does any of the alloy replacement other than the Handl.

The back of a SCAR is Ghetto booty, loose and sloppy.

#4 The Handl trigger module puts rearward pressure on the guide rod retaining plate. It has some changes to the dimensions and thickness of certain parts. This is in order to make the distance between the take down pin in front and the guide rod retaining plate is fixed and more importantly has pressure against the retaining plate.

#5 The buttstock base plate flexes under recoil, it transmits some of the recoil into the gun that should be going into the spring. The Handl baseplate changes that. It allows the recoil spring to work more effectively and absorb the recoil. It reduces the secondary recoil impulses into the gun (which was killing optics and NVG's)

The back end of a Handl equipped SCAR is tight like a 18 year old girls gymnastics gold medalists butt.

look at the movement in the gun between the two videos

In video #1 watch at about 5 minutes smooth during controlled pairs, recoil is straight back and up. This gun WAS NOT equipped the a stock base plate. Which IMO goes a real long way in improving the recoil management. But the effect of having a stressed member trigger module will become real apparent after video two.

http://youtu.be/8GxwVicY8SI

In video #2 look at the flex and movement in the gun, no way an accurate controlled pair is gonna happen with that. Just replacing polymer with alloy, no real improvement.

http://youtu.be/h1Y4DNLPNWk

#6 I hope this information brings clarity for those who have asked.

[MadAngler1]

Can you or Handl provide a free body diagram that explains how adding the Handl lower receiver significantly reduces the stress imposed on the upper receiver? The lower receiver pushing up against the retaining plate alone should not make much of a significant difference in reducing the stress or recoil impulse on the upper receiver. Likewise, doing so may limit the ability of the back plate to move and absorb the recoil impulse of the bolt carrier and recoil guide rod. It would be akin to limiting the travel of a buffer spring/buffer assembly on an AR-15.

If one told me about an upgraded recoil spring and guide rod, and an updated retaining plate/buttstock baseplate, then I could see a reduction in the recoil "impulse" (Force x time) as the stress of the bolt carrier upon the upper receiver/recoil spring/retaining plate would be dissipated over a greater length of time.

I have yet to see any military documentation or randomized controlled trial demonstrating that the Handl lower is superior to the stock SCAR system, reduces stress on the upper receiver, etc. Likewise, I fail to see the need for the use of SR-25 magazines in a SCAR, now that SCAR-17 mags are widely available. The whole problem I have with criticisms leveled at the SCAR system (on both sides of the debate: detractors and supporters) is that nobody provides any data or demonstrates any real tests.

[Fox33]

your post

MAD,

I will ask Alan Handl next time we talk. We have an agreement I tell him what the standards the gun should meet (without showing any .mil docs) and he tells me what they have found. I am not an employee of his I just advise him. He has a pretty serious gag order on his guys after the whole rev-engieering thing @FNfourms.

I presume you'd want to see the accelerometer data and the slow mo videos. anything else? I will ask but I can not guarantee a thing. Are you willing to PM me professional credentials? I will see if they will contact you. I am sure Handl would not want his IP just floating around the open net.

Also they do have a modified BCG and spring.

[MadAngler1]

MAD,

I will ask Alan Handl next time we talk. We have an agreement I tell him what the standards the gun should meet (without showing any .mil docs) and he tells me what they have found. I am not an employee of his I just advise him. He has a pretty serious gag order on his guys after the whole rev-engieering thing @FNfourms.

I presume you'd want to see the accelerometer data and the slow mo videos. anything else? I will ask but I can not guarantee a thing. Are you willing to PM me professional credentials? I will see if they will contact you. I am sure Handl would not want his IP just floating around the open net.

Also they do have a modified BCG and spring.

If they modified the BCG and spring, in addition to the retainer plate and stock hinge assembly, then I could see that it would matter. Hence, one could make such claims. However, I have yet to see a evidence of a single military contract for Handl, or any evidence that his lowers or parts are being used by the US military. The same goes for Sgt Stryker's stuff over on the FN forum, and Hi-Desert Dog. Likewise, the US military has not released any data to the public to suggest that the purported issues of "lower receiver cracking" and "optics failure" due to the SCAR's design actually exist. I have to conclude then that my SCAR-17 rifle is not in need of a new lower receiver, and my as-issued FN magazines are just fine.

Mr. Handl isn't any more obliged to publish his technical data than FN, as few if any gun companies actually publish such info. My problem though is that Handl is making claims that essentially FN's millions of dollars spent on engineers and product R&D failed to develop a good lower receiver that can withstand the rigors of .308 abuse. When making such claims, a company should at the very least publicly demonstrate how their lower works and provide quantitative measurements for decrease stresses on optics and components. The Youtube videos posted don't really do that objectively.

I'm actually a medical doctor with a biomedical engineering degree from my college days. I don't work in the gun industry, and I haven't touched SolidEdge or Matlab in ten years. However, I do believe in evidence based medicine (EBM). I firmly believe that the principles of evidence based clinical science can be applied to gun, cars, etc. Handl's lower receiver and FN's purported SCAR issues are no different. I am not trying to start a flame war with anyone, but I am trying to be objective. As an owner of a SCAR-17, I would like to see data, info and publicly available information regarding these matters.

Thanks

[Fox33]

understood I will see what I can do

[ScottsBad]

MadAngler1, I too tend to be skeptical of claims that are made without hard numbers. I'm a computer scientist turned Exec now retired kinda guy, but there are certain things we do know that are incongruent. First, the Handl lower was originally marketed as a lower that could be used to convert the feed of the SCAR to use PMAGs (SR-25) mags instead of SCAR mags. I don't recall any mention of recoil modification.

Second, the whole analogy of the "fat bottom women" just doesn't ring and seems bass-ackwards. A stiff backing plate is going to transfer more recoil directly back to the shooter. One of the things I love about the SCAR is the less abrupt recoil, if I wanted it to shoot like an AR-10 I would have bought an AR-10 instead of two SCAR 17S. I've been pretty intimate with my 17 and I personally see controlled pairs being less about the stock, BCG, and action spring than I do about the muzzle device, good form, and practice.

Third, I really don't give a rat's ass if some optics and NV break, the optics and NV ought to be able to handle the SCAR recoil impulse. You don't muck with the rifle to keep the optics from breaking, you tell the optics makers to fix their optics. If the light on my motorcycle quits because it can't handle the vibration of the motorcycle you don't redesign the frick'en motorcycle.

Finally, to MadAngler's point. If it is such a large problem, why isn't FN on top of it. You'd think that if the problem were that large FN would be fearful of losing sales (Especially to the military) so they would jump in to fix the problem. Why is it that little Handl Defense is the only outfit that can do it? Doesn't make sense from an outside observer's view.

Look I will NEVER buy a lower so I can buy cheaper mags, mags are expendable. I've not had any problems with optics. The only interest I have in the stock hinge is the extra strength.

Sorry, but it is really hard to imagine Handl Defense out engineering FN. Maybe they can, but you'll have to prove it to me with more than the lame fat butt analogy and a couple of inconclusive videos.

[Koshinn]

Fox33, you'll post them here right? Or will you be only PMing the data you receive from Handl?

[ScottsBad]

Certainly data posted here would help your case. I'm used to hearing all kinds of claims, as others do, but Fox33 you stuck your head out of the fox hole and asked for it. I'll be interested to see what you can produce.

[1911-A1]

Fox33,

Your language and claims remind me of an old-fashioned carnival barker, relying on flowery, polysyllabic vocabulary to disguise his lack of content. Nothing you said was very specific, and moreover would be difficult to prove through testing. Frankly nothing you posted tells me much aside from "Handl product good", and what you did say could have been conveyed in FAR fewer words. Are you trying to build credibility through technical jargon? Seems like a lot of flak to me. We're talking "padding a college essay-grade flak".

Also, it's clear you're associated with Handl, so maybe you should mention that in your signature going forward. Historically, this site hasn't been enthusiastic about shills.

[Fox33]

1911

I have stated pretty consistently that I have advised them and done T&E for them. I not a paid employee, don't want any connotation, or impression, or even hint of conflict of interest with what I do for the military. But I'll add some signature information if you would like.

Everyone else,

I will talk to the guys at Handl Defense and see what they say, and what they will give me. I will post up whatever I get.