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Posted: 2/5/2004 12:21:05 AM EDT
| Gents, I am currently deployed in Afghanistan and need some of your collective technical assistance. My buddy sent me a TA31 and I have a personally owned TA01, I would like to mount these on my issue M4 flattop. When I did this I found I could not zero the scopes due to not enough vertical adjustment ie I couldnt get the point of impact within 20 inches of the point of aim (impact was way low). I attempted to get on paper at 25 and then zero at 100. I know both those scopes are factory calibrated for a 20 inch barrel firing M193 55gr off of a carry handle. My setup was a 14.5 inch barrel firing 77gr and 62gr off of the flattop mount with 2 thumb screws. I am doing something wrong or am is this just not possible due to the internal calibrations. We are issued M68 CCOs and I have not been able to find at TAO1NSN. Over here with the long distances a powered scope rather than red dot sight would be preferable. Thanks. |
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You're doing something wrong or your ACOG is seriously broken. The distance drop at 100 yards between a 14.5 and 20" barrels pretty much isn't 20+ inches which would be the minimum come up/down on an ACOG I'd guess. I would make sure that you've got it mounted flat and tight to the rail. I didn't know we (military) were issuing 77 grain cartridges? Why not get some mil-spec federal ammo and zero the weapon? Last time I checked it was cause for a courts marshall to get caught firing non-issued ammo in a issue weapon - something change when I wasn't looking??? |
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Paul, I think if you check in the Ammo folder, you will find that the Army issues some troops 77 gr OTM Black Hills rounds. It is designated MK262 Mod 0 and Mod 1. Depends upon bullet maker. GPSS had a lot made for a group purchase. You can check it out in the Ammo forum or on GPSS website. Ed |
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Paul, While 77gr Mk262 is no where near "standard issue", there are quite a few units who are able to get it issued to them. MTN5FWD, Several dozen (at least) of our members are using TA01s and TA31s on M4s with 77gr ammo, so this combo is definitely workable. The BDC "ladder" isn't going to be exactly on, but that's no big deal. Something somewhere has to be mechanically out of alignment if you're that far off. Can you zero this rifle with a detachable carry handle? Do you need to be at the extreme ends of the adjustment range with front sight elevation to do so? If so, you could have a damaged upper with an upper-to-barrel misalignment. This isn't as uncommon as you'd imagine if your M4 has had a lot of weight mounted on the M4 RAS rails. Next, check the scope-to-base mounting. Make sure the mounting rail on the scope is fitting correcly into the base. It doesn't take much of an angle change to make a big difference downrange, and if I were to bet, I'd say this is the most likely place for a misalignment. Finally, the base-to-upper fit needs to be good and flat. Please let us know how it goes, or if we can be of anymore help. -Troy |
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I had the same problem with my TA 31 ( I was the problem)I thought I damaged the scope because I was so far off. I went back to the basics as per the manual using the 300m line for 25m. I got 4x4 sheet of cardboard just for 25m, I'm glad I did because I could not believe how far I had the scope out of adjustment.I used M855 ammo. I then went to 100m using the 4x4 sheet of cardboard. I was still about 7 O'clock 18inches low. I was then able get the zero very quickly. I then used Bart Roberts BDC I used the 16" 75gr OTM for the 77gr OTM out of a 1/7 14.5" vel. should be within 100fps...good luck Soldier |
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Gents, Thanks so much for all the feedback, my frustration meter is pegged at the moment. I am hanging some weight off of the rails (PEQ2, gangster grip, M3 illuminator) so that may cause some issues. The black hills 77grain stuff is great, I squirreled a case away for special occasions. I really want to get the ACOG squared away for long range engagements. have a folding stock AK with an Aimpoint on it for close work. Thanks again and keep up the good work, this is a great resource. Will try all the suggestions and let you know how it works. |
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