Why is the FN SCAR-17 especially ' hard on optics' ... ?

November 11, 2019, 05:48 PM

parabellum

Supposedly, something to do with the harmonics of the upper receiver in recoil. Also, supposedly, FNH-USA began work on some kind of shock absorber system to address this issue, but never completed the work.

A SCAR-17 will eat cheap scopes in no time. Quality optics are a must.

November 11, 2019, 05:56 PM

RichardC

parabellum, I found this:

https://www.m4carbine.net/show...-HARD-quot-on-optics

It refers to the harmonics you mentioned.

November 11, 2019, 06:33 PM

Belgian Blue

I really don’t think it’s really so much that “...the FN SCAR-17 especially ' hard on optics'”

But rather, many optics aren’t durable enough for use on SCARs. FN set out to build a rifle to meet SOCOM requirements and in so doing, their primary focus was on reliability, modularity and system longevity. The end result was modular combat rifle that met SOCOM’s needs. At that point it becomes the optics manufacturer’s responsibility to offer SOCOM optics that are compatible and long term durable with the rifle SOCOM selected.

There are plenty of choices: Nightforce, Leupold, Aimpoint just to name a few. I’m not convinced the high end European makers are likely to fare as well, not because they aren’t fine optics, but rather they haven’t specifically addressed the unique recoil characteristics of the SCAR. For those who want an optic that hasn’t been well proven on SCARs, I might suggest they purchase from Brownells as they offer a good lifetime warranty on most of their products.

November 11, 2019, 07:28 PM

arcwelder

quote:
Originally posted by Belgian Blue:
I really don’t think it’s really so much that “...the FN SCAR-17 especially ' hard on optics'”

But rather, many optics aren’t durable enough for use on SCARs. FN set out to build a rifle to meet SOCOM requirements and in so doing, their primary focus was on reliability, modularity and system longevity. The end result was modular combat rifle that met SOCOM’s needs. At that point it becomes the optics manufacturer’s responsibility to offer SOCOM optics that are compatible and long term durable with the rifle SOCOM selected.

There are plenty of choices: Nightforce, Leupold, Aimpoint just to name a few. I’m not convinced the high end European makers are likely to fare as well, not because they aren’t fine optics, but rather they haven’t specifically addressed the unique recoil characteristics of the SCAR. For those who want an optic that hasn’t been well proven on SCARs, I might suggest they purchase from Brownells as they offer a good lifetime warranty on most of their products.

You could say aaaaaaaaaalllllll that, or just say that "the SCAR-17 is hard on optics." Let's call it shorthand for any rifle known to have a significant recoil impulse.

November 11, 2019, 07:31 PM

RHINOWSO

The SCAR 17 doesn't have significant recoil impulse, but it does have a 'fast' recoil.

November 11, 2019, 07:38 PM

Andyb

Scar 17's just have a taste for fine optics.

November 11, 2019, 08:44 PM

parabellum

What about the Trijicon ACOG and VCOG in terms of durability on the SCAR-17? The VCOG is an intriguing optic and I see that in addition to the 1-6, Trijicon is now offering a 1-8 version.

November 11, 2019, 08:46 PM

fritz

I no longer recall the source, but I did see a super slow motion video of SCAR receiver during the recoil process. There was a fair amount of flex in the upper receiver, and these forces acted upon the optic. It was theorized that a very stiff one-piece scope mount would add rigidity to the upper receiver, thus reducing the flexing forces on the optic.

The flexing forces might be a function of the recoil pulse & harmonics, or it might be something else.

I do suspect a heavier and stiffer upper receiver might reduce the SCAR's potential for chewing on optics, but it's just speculation on my part.

November 11, 2019, 09:55 PM

RHINOWSO

quote:
Originally posted by parabellum:
What about the Trijicon ACOG and VCOG in terms of durability on the SCAR-17? The VCOG is an intriguing optic and I see that in addition to the 1-6, Trijicon is now offering a 1-8 version.

Never heard of any issues with an ACOG on a 17, by all accounts I've seen they are good to go - however I would choose one of the models with decent eye relief.

The VCOG 1-6 is an interesting optic which never seemed to catch on as well as it's Vortex and Leupold competitors - main complaints seem to be noticeable diopter shift throughout the magnification range, but I've never seen one at the range and only played with one at SHOT show for a couple of minutes, so I can't speak to it. Never heard of one breaking on the SCAR centric forums, but I don't think many people are using them.

November 11, 2019, 09:58 PM

ZSMICHAEL

[quote]The SCAR 17 doesn't have significant recoil impulse, but it does have a 'fast' recoil.

^^^^^^^^^
Looking into one. Can you explain further?

November 11, 2019, 10:04 PM

RHINOWSO

To me the recoil comes on all at once and is gone in the SCAR 17 - some might call it a bit 'snappy', which I equate to the recoil onset being fast.

Some other AR-10 type 308s recoil harder overall to me, but it doesn't come on as fast.

Imagine a car accelerating faster than another, but not getting as fast as speed in the end.

Of course this is all very subjective but it's how I feel it.

November 11, 2019, 10:09 PM

1KPerDay

I heard some smart dude opine that the reason the 17 kills lots of optics is that the bolt carrier is pretty large and heavy and the gun is light, and it’s the shock as the bolt CLOSES that optics builders don’t often account for. All of them build optics to withstand rearward acceleration of the rifle but not the other way necessarily.

Can’t remember where I read it but it made a little sense to me. I wouldn’t say the 17 has a “fast” recoil cycle. It feels pretty slow and smooth to me. The 16 is crazy smooth.

November 12, 2019, 12:33 AM

ShneaSIG

I've never seen anything conclusive, but heard it blamed on the bolt carrier more than once.

Evidently they were rough on night vision or thermals, too, when the SCAR-17 first came around.

November 12, 2019, 12:35 AM

benny6

The M14 is especially brutal on optics as well and has an exceptionally fast cycle rate. They are known as scope killers and have the added mass of an operating rod and a piston which add to the forward cycling impulses which will kill lesser made scopes. If the SCAR has similar masses moving during recoil, it doesn’t surprise me that it’s also a scope killer.

The M14 has the initial recoil of the fired round, the bolt slamming into the heel of the receiver, the operating rod slamming into the receiver face, the piston reaching the end of travel inside the gas cylinder, then during chambering, the bolt closing and the operating rod slamming the piston into the gas plug sending shocks through the scope in the opposite direction than in recoil.

I’m not familiar with the SCAR, but if the anatomy is similar, then the recoil forces are similar as well.

Compare that with the motions of a DI AR-10.

Tony.

November 12, 2019, 01:05 AM

arcwelder

quote:
Originally posted by RHINOWSO:
The SCAR 17 doesn't have significant recoil impulse, but it does have a 'fast' recoil.

For fucks sake.

The physics of .308 semiauto are actually a constant. Boys, quit mincing.

Like many .308 autos before it, you can't just put any old optic on this rifle.

November 12, 2019, 04:52 AM

RichardC

Two way recoil caused by the operating system and receiver flex?

Riflescopes made for spring piston airguns addressed similar problems long ago: etched reticles ( not wire), two way bracing of lenses and internal parts, and one piece scope mounts.

I was remembering these features from the seventies when I got my Beeman FWB124 and the Beeman Blue Ribbon 2-7X32 scope.

Back then, spring piston air guns were destroying even expensive, high quality riflescopes.

Remember the Beeman Short Scopes? They were being used on AR15's as well as on airguns.

November 12, 2019, 07:04 AM

cigardad

Good mounts are important as well. A mount made specific for the SCAR helps such as the ADM AD-Delta.

November 12, 2019, 07:14 AM

sigfreund

quote:
Originally posted by cigardad:
A mount made specific for the SCAR helps such as the ADM AD-Delta.

I am curious what is special about that mount as pertains to the SCAR.
I believe I have seen many mounts of essentially the same design. (Not a challenge or dispute because I know virtually nothing about that rifle, just genuinely curious.)