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Posted: 12/30/2005 2:54:40 AM EDT
[Last Edit: 12/30/2005 2:57:42 AM EDT by scottfn308]
I have an AR with a 14.5" barrel and a flattop upper
with an ACOG TA01 mounted on it with an ARMS #19S
mount.

That being said, here is the concern.

The scope moves a bit on the upper.
Not side to side, just front to rear, just a hair.
Not much at all, just a hair.
I know it is not the scope to mount interface, as I
used blue locktite on it. The mount just slides a bit
on top of the rail.

I was wondering if this is just the nature of the beast
for a quick detach mount, or if my upper receiver is out
of spec or something. Could the rail itself, be undersized
and causing this, or am I just paranoid ?

The rifle still shoots great groups, so I guess it dosen't affect
accuracy. I took the 4 day practical rifle course at Front Sight
and earned Distingushed Graduate honors with the rifle,
so I guess it dosen't affect accuracy, Hell I can even shoot 1.25"
groups with it at 100yds when I do my part, but I am still a bit
concerned.

Thanks for any help you can provide.

Scott
Link Posted: 12/30/2005 3:02:42 AM EDT
shouldn't move at all IMO. what kind of mount do you have lever or screw down ?
Link Posted: 12/30/2005 3:58:31 AM EDT

Originally Posted By tugboat:
shouldn't move at all IMO. what kind of mount do you have lever or screw down ?



#19S Throw lever
Link Posted: 12/30/2005 4:02:20 AM EDT
most likely its the pressure plate on the arms throw lever but if its just moving a hair front to back i wouldnt worry too much
Link Posted: 12/30/2005 4:02:38 AM EDT

#19S Throw lever


Imagine that.... One of the many reasons I have left all of my ARMS stuff in the dust!

KAC is the way.
Link Posted: 12/30/2005 4:05:29 AM EDT
i have started using larue tactical
Link Posted: 12/30/2005 4:06:31 AM EDT
Shouldn't move at all and mine shoots 1/2 MOA all day long. Not bad for a rifle meant for IMGA/USPSA 3-Gun and NOT for bench shooting.

Check your levers and it wouldn't hurt to check some dimensions on the receiver.

SPC Richard A. White, Senior Medic
249th MP Detachment (EACF)
Camp Humphreys, ROK
Link Posted: 12/30/2005 4:09:45 AM EDT
the pressure pad under the throw lever wears out and that could cause it or it could be the variance of different manufactures anodizing
Link Posted: 12/30/2005 4:19:35 AM EDT
What brand of upper are you using?

The problem with the ARMS mounts is that they are made to fit ONLY on in-spec uppers. If yours is a second or third tier manufacturer it may not be in-spec.

You could try a Larue mount, as they have some adjustability to mate better to out-of-spec uppers.
Link Posted: 12/30/2005 4:39:28 AM EDT
I was thinking it could be the pad also, as it really dosen't look to
me to be a very secure mounting system.
BTW it is a upper I got from J&T Distributing.

It has no marks on it at all, but is seems to be a good one.
Perhaps I will try another mount and see what happens.

Are the GG&G mounts for this optic good ones ?

Regards,

Scott
Link Posted: 12/30/2005 6:07:30 AM EDT
I had the exact setup and problem on a Bushy upper. There was just a slight fore and aft movement, but it wasn't really hurting accuracy.
I went with the Trij thumbscrew mount and there is no problem.
Link Posted: 12/30/2005 6:15:40 AM EDT
I had the same Upper / ARMS mount wobble.

The receiver was out of spec, so used a LARUE mount instead

The ARMS fitted only a true spec receiver; The LARUE fitted both........

The rifle came from Sabre Defense, the lower was PWA, yet the Upper and barrel remain a mystery!
Link Posted: 12/30/2005 6:54:41 AM EDT
ARMS mounts are not adjustable at the throw lever.
All upper receivers are a little different..read different sizes.

ARMS mounts are made to fit ARMS rails..
ARMS rails may not be the same size as a Colt, Bushy, LMT or CMT rails.

Use a QD mount with a throw lever that is adjustable.

It does matter if your mount moves!
Link Posted: 12/30/2005 6:56:26 AM EDT
LaRue Tactical = Solution
Link Posted: 12/30/2005 7:01:28 AM EDT

Originally Posted By in_burrito:
What brand of upper are you using?

The problem with the ARMS mounts is that they are made to fit ONLY on in-spec uppers. If yours is a second or third tier manufacturer it may not be in-spec.

You could try a Larue mount, as they have some adjustability to mate better to out-of-spec uppers.




what would you consider "mil-spec" and who would fall into second or third tier?
Link Posted: 12/30/2005 7:28:18 AM EDT
I had the same problem with my M68 mount on a Bushy upper.

Tryed it on a Colt, two RRAs, and an Oly. It was only tight with no movement on the Oly.

Since then, I changed to Larue.

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