This much misalignment of your cheese-grater will cause 20 MOA error...


PDA






W.E.G.
July 11, 2009, 04:46 PM
This much misalignment of your cheese-grater will cause 20 MOA error...

…in point of impact if your front sight is mounted on the cheese-grater.

5 MOA error for every 1 degree misalignment.

http://i227.photobucket.com/albums/dd7/rkba2da/rifle%20pics/troyhandguardmisaligned1.jpg

http://i227.photobucket.com/albums/dd7/rkba2da/rifle%20pics/troyhandguardmisaligned2.jpg

If you enjoyed reading about "This much misalignment of your cheese-grater will cause 20 MOA error..." here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!
gvnwst
July 11, 2009, 04:47 PM
This is why I have a monolithic rail. ;) :D

jpwilly
July 11, 2009, 05:12 PM
Yip - It's called a "canted front sight" and it's going to be an issue down range.

jhco
July 11, 2009, 05:24 PM
Wow thats not good

RyanM
July 11, 2009, 08:51 PM
Hm. Yikes. I believe that is why the list of handguards which are consistently suitable for optic mounts (and by extention, front sights) is very short. And I don't recall Troy being on them. KAC (not the RIS), LaRue, Magpul, and Daniels, IIRC. Edit: and Vltor. I knew I was forgetting one.

It's also fairly obvious that someone at Troy doesn't know how to count. 12, 13, 14, 16. :p

Uncle Mike
July 11, 2009, 11:24 PM
Loosen it up and index it... it is a common problem... no biggie!

:D

1858
July 11, 2009, 11:54 PM
I've got a Daniel Defense Omega rail on my POF but I have a Troy front sight mounted to the gas block ... works for me!

http://128.171.62.162/hawthorn-engineering/thr/pof/pof_dd_1.jpg

:)

Eightball
July 12, 2009, 12:47 AM
Wow. Didn't expect to see that much rotation.

What'd you expect?

W.E.G.
July 12, 2009, 07:33 PM
Went back to the range today.

Considerable improvement from yesterday's 40 MOA debacle. http://www.ar15.com/images/smilies/icon_smile_big.gif

Despite having resolved the gas-block interference issue, I still could not get the two halves of the Troy rail to cinch-down in perfect relation to the
upper receiver. The Troy rail is still "cocked" a little to one side. I swear I "bridged" the rails, and Itried everything including voodoo to try to make those
halves settle at just the perfect spot.
tighten-loosen-wiggle-shift... tighten-loosen-wiggle-shift... tighten-loosen-wiggle-shift... tighten-loosen-wiggle-shift... tighten-loosen-wiggle-shift... http://www.ar15.com/images/smilies/smiley_confused.gif
No dice.

http://i227.photobucket.com/albums/dd7/rkba2da/rifle%20pics/troyhandguardmisaligned10.jpg

I ended up having to put one-and-a-half turns right windage on the knob to bring point of impact to center.
The sight allows just over three full turns left or right from center if needed. So, I can live with this.
The gun ran 100% with-and-without the suppressor using Federal white box XM-193. So, at least I didn't bugger the gas system. http://www.ar15.com/images/smilies/smiley_abused.gif

http://i227.photobucket.com/albums/dd7/rkba2da/rifle%20pics/troyhandguardmisaligned9.jpg

One “discovery” to note”
I discovered that this gun shoots about 5 MOA to the left when the suppressor is removed.

Otherwise, the targets below were each fired with the suppressor.
None of these results are anything to write home about, but they are what they are.

Best target at 100 yards today was with the EOTECH while the targets were shade by cloud cover.
The shot out the bottom here happened when the sun peeked out suddenly for one shot during the string.

http://i227.photobucket.com/albums/dd7/rkba2da/targets/2009-07-12/eotech.jpg

Another weird thing I discovered was a shift in point of impact when the gun was allowed to cool for only a minute or two.
Using the scope, I could shoot pretty decent groups about 2.5” as long as I kept the suppressor consistently hot.
When it cooled, even for a minute, it would consistently “throw” the first shot when firing resumed. Then the rounds would drop back into the “group.”

I would really like to be able to speak to the question of where does this gun shoot from a stone-cold bore.
I do not know the answer to that question at this time.

The out-of-the group shots (including the off-the-target shot) are circled or marked by magic marker here.

http://i227.photobucket.com/albums/dd7/rkba2da/targets/2009-07-12/leupold.jpg

Next purchase will be a FACTORY-INSTALLED front sight on the gas block, and from a major manufacturer.
The guys who do this all-day-every-day must have it figured out better than me.

If you enjoyed reading about "This much misalignment of your cheese-grater will cause 20 MOA error..." here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!