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11/2/2022 4:30:06 PM
Posted: 9/15/2020 5:49:16 PM EST
If this is old news or a dupe, I’m sorry as it’s new news to me.

Heard some interesting info today from a local shop...

I know I know local shop and whatnot but info is info and I had not heard this one yet.

So we were discussing scopes for the SCAR 17 and I had mentioned about the rumors of the 17 killing optics.
He said he actually had brought the question up to his FN rep and was given an actual answer.

The rep apparently said FN is aware of the situation but won’t officially say anything.
Said that in FN’s testing they found the cause.
Apparently it stems from the mass of the bolt causing the top rail to flex/vibrate up and down.
The flex is enough that it damages the optic.

Now here’s the key to saving optics - according to FN apparently.
You have to mount the majority of the optic behind the charging handle slot where the receiver is solid.
This can be also remedied with a long cantilever mount mounted to the “ok” zone, the monster ADM mount or an optic built like a tank such as an Elcan.
Optics like the Aimpoint apparently just aren’t effected.

Now I know it’s gun shop talk but do what you will with the info... I’m not big on rumors but just thought it was interesting.

TL/DR:
The slots on the SCAR receiver weakens the rail causing flex to damage optics; mount behind charging handle slot.

Picture I made for reference:
brownells
Link Posted: 9/15/2020 6:05:40 PM EST
[#1]
Yes.
Link Posted: 9/15/2020 6:07:37 PM EST
[#2]
Interesting. You said something about an UGG boot right?




j/k
Interesting take on it, makes a bit of sense I guess.
Link Posted: 9/15/2020 6:09:49 PM EST
[#3]
So theoretically if I take a long picatinny to picatinny rail adapter/riser that runs the length of the existing rail, that should remedy it?
Link Posted: 9/15/2020 8:58:46 PM EST
[#4]
Gas tune your SCAR via gas jets and add MotoTech’s rubberized buttpad...and keep your stock OEM...

Aftermarket stocks get rid of the polymer stock housing for aluminum. The factory poly stock housing acts as a secondary buffer.

Also. Don’t cheap out on optics and especially mounts. You DO NOT want to run a cantilever mount unless it has a backbone built in like the GEISSELE or Leupold IMS...
Link Posted: 9/17/2020 6:12:54 PM EST
[#5]
Interesting answer. I've only ever heard that it was due to the significant recoil impulse from huge BCG.  I never heard of optic placement. I went with an Elcan 1.5x/6x, which is built like a tank and mostly behind the charging handle.

For the 17S, you just have to buy a high quality optic. As stated above, proper tuning of the gas jets with PMM gas jets is advised due to the 17S being over-gassed to aid in reliability.
Link Posted: 9/18/2020 8:36:20 AM EST
[#6]
Everyone just needs to watch this video:

https://www.youtube.com/watch?v=9Zi52codWEY&t=1443s
Link Posted: 9/19/2020 10:54:22 PM EST
[#7]
I’m going to use a Vortex 1x10 with a Bobro SCAR monolithic mount.
Link Posted: 9/23/2020 12:37:27 AM EST
[#8]
The upper is extruded to save $, rather than milled from billet, which is more rigid.
Link Posted: 9/23/2020 12:51:10 AM EST
[#9]
Sounds like typical gun store bullshit and doesn't even make sense.

Bolt slamming home creates lateral forces.  Mounted on the solid portion, there is less flex which means the optic absorbs more of the shock.  A flexing handguard would essentially be a shock absorber.
Link Posted: 9/23/2020 12:54:41 AM EST
[#10]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Everyone just needs to watch this video:

https://www.youtube.com/watch?v=9Zi52codWEY&t=1443s
View Quote



The SCAR gas valve doesn't work by bleeding but restricting
Link Posted: 9/23/2020 1:10:38 AM EST
[#11]
I have a TA11E-G on my 17S and have never had a problem with it.

I tend more to believe it is more the double recoil impulse that causes problems.  Once when the massive bolt carrier slams into the back of the receiver and a second when it slams forward.  I have a couple thousand rounds through it and I figure if I end up buying another to replace it, the other features of the rifle out weigh the bad.

Link Posted: 9/23/2020 7:29:13 PM EST
[#12]
Discussion ForumsJump to Quoted PostQuote History
Quoted:



The SCAR gas valve doesn't work by bleeding but restricting
View Quote


Have you looked at the scar plug?

It bleeds off two ways...
Link Posted: 9/23/2020 7:52:47 PM EST
[#13]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
I have a TA11E-G on my 17S and have never had a problem with it.

I tend more to believe it is more the double recoil impulse that causes problems.  Once when the massive bolt carrier slams into the back of the receiver and a second when it slams forward.  I have a couple thousand rounds through it and I figure if I end up buying another to replace it, the other features of the rifle out weigh the bad.

View Quote


IMHO it's that second impulse that's the culprit.  Rifle scopes are built to handle the rearward impulse, but not the forward impulse.  Same reason piston air rifles destroy standard rifle scopes.
Link Posted: 9/29/2020 7:24:07 AM EST
[#14]
Discussion ForumsJump to Quoted PostQuote History
Quoted:


IMHO it's that second impulse that's the culprit.  Rifle scopes are built to handle the rearward impulse, but not the forward impulse.  Same reason piston air rifles destroy standard rifle scopes.
View Quote



This.

The heavy carrier and high speed are similar to a slide hammer , on each end.
Its similar to .50 BMG rifle using an effective brake that reverses rear G forces to forward G force in milliseconds and the reason some optics were re-engineered to compensate.

Select an optic and mount designed for the SCAR , like the ADM mount and a good optic.

Recoil force on a .50 with brake~




Elcan~

Tough as nails





MKIV in ADM mount.

Link Posted: 10/14/2020 11:38:12 PM EST
[#15]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Interesting answer. I've only ever heard that it was due to the significant recoil impulse from huge BCG.  I never heard of optic placement. I went with an Elcan 1.5x/6x, which is built like a tank and mostly behind the charging handle.

For the 17S, you just have to buy a high quality optic. As stated above, proper tuning of the gas jets with PMM gas jets is advised due to the 17S being over-gassed to aid in reliability.
View Quote


My SA58 FAL was hard on optics as well.  Broke a TA31-RCO ACOG.  Got it repaired and mounted it to my 17.  Broke again.  Same failure. Has run fine on my AR15 for years.

Massive bcg on both rifles. My SA58 is super light as well.
Link Posted: 10/14/2020 11:56:05 PM EST
[#16]
Quoted:
Apparently it stems from the mass of the bolt causing the top rail to flex/vibrate up and down.
The flex is enough that it damages the optic.

...
This can be also remedied with a long cantilever mount mounted to the “ok” zone, the monster ADM mount or an optic built like a tank such as an Elcan/Acog.
https://i.imgur.com/XhsBRkB.jpg
View Quote


Uhhhh, wouldn't cantilever be worse if it flexes up and down? An ADM or Bobro "SCAR" mount would be better options.

Here is the thing that the "SCAR bad on optics crowd" never talks about. If you are shooting your SCAR 17, chambered in freaking .308, enough to break a scope. You can just buy a new one you rich mothaf***a.

OR

Most reputable companies would probably warranty repair or replace it.
Link Posted: 10/15/2020 8:43:43 AM EST
[#17]
So I recently talked to a rep at Aimpoint and was told that during a SOCOM test they placed a T2 on a 45 degree mount.
They then fired 20k rounds using various other optics... all the while the Aimpoint remained on the rifle.
After the testing they reviewed the Aimpoint and found zero issues... it held through the entire test.
According to this rep, it was the only optic that survived the test.
Again, words are words so take it as it is but still interesting info.
Link Posted: 10/17/2020 10:56:04 PM EST
[#18]
MY HK SR9TC recoils so violently; that it turns on and off the scope sometimes.

It actually activates the rubber on/off button.
Link Posted: 10/18/2020 9:01:42 AM EST
[#19]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
MY HK SR9TC recoils so violently; that it turns on and off the scope sometimes.

It actually activates the rubber on/off button.
View Quote


BONUS
Link Posted: 10/18/2020 9:25:58 AM EST
[#20]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
MY HK SR9TC recoils so violently; that it turns on and off the scope sometimes.

It actually activates the rubber on/off button.
View Quote


Link Posted: 11/8/2020 8:25:12 AM EST
[#21]
Discussion ForumsJump to Quoted PostQuote History
Quoted:


IMHO it's that second impulse that's the culprit.  Rifle scopes are built to handle the rearward impulse, but not the forward impulse.  Same reason piston air rifles destroy standard rifle scopes.
View Quote


This!
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