I'd like to sight my BM XM15 Flat-top for Improved Battlesight Zero as described on the MDAR15 site. However my Craftsmen 1/16" Ball End Hex tool is not turning/loosening the screw
(Step 3 below). I thought it be the wrong tool and did not want to over-torque & cause damage, so I took it to my local black rifle shop and was advised that the small pin on the opposite side of the windage knob near the UP < marking most likely was preventing the screw from turning and it might require some "surgery".

I'd like to go IBZ w/o surgery. Anyone have similar experience? Thanks!
(I also have the .40 taller site post installed)

3. Using a 1/16" Allen wrench loosen the screw (under the revealed hole) in the sight wheel 3 full turns. Leave the wrench in the screw.

Boom,

Yes I think he's talking about the ball detent on the left side "blocking" the turning. (He wasn't a smith and did politely recommend 2 smiths to me)

I'm definitely putting my Craftsmen 1/16" Ball End Hex tool down the correct top-side screw-hole as shown in the MD instruction-photos. It feels like I'm getting a good fit, but when I try to turn the hex key tool the screw is not budging.

So if your're saying that detent has no effect on blocking, and the screw will loosen and turn, then I must have the wrong tool. Should I get the flat-ended Allen wrench and maybe put a drop of oil down there 1st?

This is what I'm using

I must need this flat-ended 1/16" and not the ball-ended

I've done mine and they were all really tight. My .02.

Thanks!

Got the flat-end 1/16" loosen up with the screw with a moderate twist.
I had 6 clicks between the 3 & 4 so set my the sight at 6/3 –4 clicks (instead of –2).

Went to the range & the 50yard groupings were some of the best I've had. POA = POI.
When I moved my target out to 100 yds my groupings were scattereed (using XM193). Where on the target would you expect your POA/POI to be at 100 yards with IBZ compared to 50?    

Yes I did have to adjust my aim lower. It was fairly windy today & the range is in a valley w/ cross winds so it took awhile to tighten the group at 100 yards.

Is it better to continue to adjust my aim lower by 1-2" or should I adjust the front sight post at 100 yards? Once I got used to the aim modification groupings got a bit better.

If I should adjust do I rotate the post counter-clockwise or clockwise where it has
UP <=== imprinted? I want the bullet to come down so I'm guessing CCW. I've gotten conflicting advice in this regard.

Thanks again!  

Quoted: Yes I did have to adjust my aim lower. It was fairly windy today & the range is in a valley w/ cross winds so it took awhile to tighten the group at 100 yards. Is it better to continue to adjust my aim lower by 1-2" or should I adjust the front sight post at 100 yards? Once I got used to the aim modification groupings got a bit better. If I should adjust do I rotate the post counter-clockwise or clockwise where it has UP <=== imprinted? I want the bullet to come down so I'm guessing CCW. I've gotten conflicting advice in this regard. Thanks again!

Up and down is for point of impact on front sight pin. Want it to shoot lower turn opposite the up arrow. Glad to hear you are getting it where you want it. Happy shooting!