ACOG Meets ARMS #18
Posted January 1st, 2012 at 03:20 PM by jmoore
Found a Trijicon TA33G-9 ACOG quite by purposeful accident whilst looking for a TA11E on 31 Dec 2011. The TA33 IS smaller and has 1/2 power less magnification than TA11, but it's eye relief is over an inch longer than the bigger scope. Plus it's lighter than the "11", which is altogether appropriate as it's intended for the Lightweight M1A rifle project.
It did have a really tall "flat top" adaptor installed, which was kinda ludicrous considering the built-in attachment's height.
But after 30-45 minutes pondering the change in optics choice, money was squandered and we went to lunch.
As expected, the flattop adaptor was way too tall, but I had an old TA31 M4 with a short adaptor, so it got robbed to see how the scope worked on the rifle. - Not bad!
Just randomly slapped on top of the ARMS 18 mount the little ACOG came up VERY well. No craning the head to find the reticle at all! It is pushing the limits of eye relief, but the scope's very forgiving, so it's not much of an issue.
BUT, as those of you that bother to read these ramblings already know, I can't leave well enough alone, so Jan 1 was spent doing an initial mating of the scope to modified version of the flattop adaptor. A bit more work than expected, but it's done enough to take to the range. Photos!:
TA31 adaptor: Added height for scope about 0.160"
TA33 adaptor. Much taller! Didn't think to record size.
The upside to having all that extra metal is the opportunity to provide extra support to the scope after modification:
Scope will be about 0.060" lower now than with the TA31 adaptor. Good snug fit, too!
Not quite ideally situated yet, but it's already fairly super! Surprisingly so.
It did have a really tall "flat top" adaptor installed, which was kinda ludicrous considering the built-in attachment's height.
But after 30-45 minutes pondering the change in optics choice, money was squandered and we went to lunch.
As expected, the flattop adaptor was way too tall, but I had an old TA31 M4 with a short adaptor, so it got robbed to see how the scope worked on the rifle. - Not bad!
Just randomly slapped on top of the ARMS 18 mount the little ACOG came up VERY well. No craning the head to find the reticle at all! It is pushing the limits of eye relief, but the scope's very forgiving, so it's not much of an issue.
BUT, as those of you that bother to read these ramblings already know, I can't leave well enough alone, so Jan 1 was spent doing an initial mating of the scope to modified version of the flattop adaptor. A bit more work than expected, but it's done enough to take to the range. Photos!:
TA31 adaptor: Added height for scope about 0.160"
TA33 adaptor. Much taller! Didn't think to record size.
The upside to having all that extra metal is the opportunity to provide extra support to the scope after modification:
Scope will be about 0.060" lower now than with the TA31 adaptor. Good snug fit, too!
Not quite ideally situated yet, but it's already fairly super! Surprisingly so.
Total Comments 5
Comments
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Lest you think it went without a hitch, there were some modifications required to make the adaptor work with the ARMS #18 mount. (I was about to max out on photos, so that's why this is a "comment".)
Firstly, the front clamping knob would not tighten as it "crashed" a horizontal extention of the mount. But there's a fair amount of extra metal on the OD, so after turning off a bit, that drama was sorted. The knobs were off anyway to allow clamping the adaptor in the mill's vise.
The TA31 adaptor was "dry tested" jusing just one screw. It wasn't intended to be anything but a compatibility check. Having served it's purpose, it'll go back on it's old scope.
The head of the screw must be reduced in size or a flathead version used with a countersink. It cleared when "rattled around" in the #18's central slot, but apparently it isn't actually centered when mated together. Odd.
Expect a few more mods before this project is finalized...Posted January 1st, 2012 at 03:35 PM by jmoore
Updated January 1st, 2012 at 03:55 PM by jmoore - Test fired the rifle as detailed in the comments section of "Lightweight M1A build notes" blog entry, and found the scope quite usable. But for maximum efficiency, it was thought that moving the ACOG back a bit would be ideal.
So, mod the adaptor or mod the receiver?
Eh, it's the receiver's fault that there's not more flexibility in setting optics, so the receiver it is!
Simple, but expensive (in case of resale) modification:
Results? Worth it! YES! "Poiyfect"
Now for range test again. The best part of tinkering.Posted January 7th, 2012 at 03:52 PM by jmoore -
I'm curious if you considered using an arms#19 variants for acogs... the 19a or 19ld look like they would have easily worked... I'm sure you had your reasons and I do not mean to be rude. I hope this works out great!
also I found this:
http://www.google.com/imgres?q=arms+...1t:429,r:1,s:0
From the description it would seem that they used an older split rail arms mount and I know that you want to keep the weight down and these "stackable" solutions aren't the most accurate but I think it may have been easer to find a rail that came backwards toward the rear sight more...
I also realize that these solutions can be somewhat expensive...Posted January 9th, 2012 at 11:50 PM by CNelson
Updated January 9th, 2012 at 11:55 PM by CNelson (must put foot in mouth.) - Weight is the primary reason. Also, by modifying the Trijicon mount, I was able to get it lower than otherwise possible.Quote:Originally Posted by CNelson
I'm curious if you considered using an arms#19 variants for acogs... the 19a or 19ld look like they would have easily worked... I'm sure you had your reasons and I do not mean to be rude. I hope this works out great!...
]From the description it would seem that they used an older split rail arms mount and I know that you want to keep the weight down and these "stackable" solutions aren't the most accurate but I think it may have been easer to find a rail that came backwards toward the rear sight more...
I also realize that these solutions can be somewhat expensive...
Plus, time was a factor. New scope, purchased by "accident" on Dec 31. Mated to the rifle well enough to test on Jan 01. Test fired soon thereafter.
It seems to work very well. But the old 22" barrel may just have to go back on the rifle if the new 18.5" bbl. won't group better than it does now. - Little dramas.Posted January 11th, 2012 at 12:08 AM by jmoore
Updated January 11th, 2012 at 02:11 AM by jmoore - Whilst changing the barrel- again- the scope mount had to come off so here's supplemental photos:
May ditch a conventional mount altogether...Posted February 4th, 2012 at 07:04 AM by jmoore
