Udot HD Micro

To rehash, I bought an HD Micro in early 2016 and after 1000 rounds on my S&W 986 the windage adjustment started to "jump" doubling and tripling my adjustment at 25 yds. and  sometimes I would get double groups in the same 10 round target.   I sent it back to FL and they sent me a new one.  Once I began to approach 1000 rounds on the new one the trouble began at 50 yds.  I ran 10 patches of JB bore Paste thinking fouled or dirty bore.  I am certain the mount is solid.  

I began shooting groups at 50 yds. this summer.  5 to 7 of 10 rounds hold under 2" off a Hyskore rest.  The other 3 to 4 rounds are out of the main group at all clock positions 3 to 4 inches from the main group.   The best load I've found for the 986 is 5.4 CFE Pistol, 115 HAP, 1.150 COL, no crimp (bell removal) and any brass including unfired Starline.  I do not mix brass in any one group.  My hold on zero is very good and when the trigger breaks my 2 MOA dot is right on the center of POA.   There seems to be no dependency of clean or dirty bore, shot sequence, or weather.  My vision is 20/20 corrected.  I've had accurizing work done; cone centrality and polishing, crown centrality and polishing, 3 lb. trigger and yoke centrality by a qualified pistolsmith.  I've also characterized each chamber and found all 7 equally hold POI at 25 yds.  

I'm really losing confidence in my HD Micro and would like to know if others have had a similar problem with this sight.  Those flyers are just about driving me nuts.  I have not yet gone back to 25yds to see if I get similar results on a smaller scale.  Any advice would be appreciated.  Thanks.

Try a smidgeon of crimp, say 0.002 reduction in diameter.  The bullets may be moving a tad during recoil.

Thanks Wobbley.  I've done crimp jump evaluations, some going from 1.150 to 1.165 and had no issues at 25yds.  It will be worth a try at 50 and I'll do it next range visit using no crimp, slight crimp, medium and heavy crimp.  My Lee FCD die needs a good workout.

What you are describing don't seem to be your loads. Granted it's possible but the fact that the load was OK for the first 1000ish shots and then changed both times would indicate the problem is with the Udot. It can be in the mount but if when the replacement Udot was mounted without any mount changes i.e. tighten the screw,  etc. the problem was eliminated only to return again.  As I see it the only change was the Udot. I'm assuming after seeing this problem you checked screw tightness on the Udot. One thing I see on the Udot micro (a friend let me check out his when it was new and never mounted) is that the dove tail Weaver type clamp is not made right. On the side opposite the clamp nut the cut angle  drops a slight amount on the nut side there is no step so when mounting the micro it's slightly canted. Looking at the joining of the angles on the screw head side daylight can be seen also indicating it's canted. I returned the Udot and looked for something else. However I don't think that error will create the problem you are having if the clamping nut is kept tight. Eventually the aluminum will creep and that gap will close also it will wear in as long as the nut it tightened periodically. But I'm thinking this could squeeze only in the center so as to allow the scope to pivot. But should happen at all ranges.
 You problem seems to be occurring when making sight change. It seems  to be OK at 50 yet has problems at 25 after what I assume is an elevation change. Just for information how close to center of the range of adjustment is your sight setting, is any at or near the limit? I've never taken a micro apart so I don't know how adjustments are accomplished but in the full length version that can be a problem.

Am I missing something? Why not put on a different dot sight and shoot it as a trial of gun versus possibly bad sight?

Good idea Olde Pilot but I think he did that, put replacement Udot on and problem went away for 1000ish rounds. Udot micro is slightly different than most micros in the it seems to be a miniaturized version of the standard Udot. I'm thinking a sight change is required but which one? Aimpoint will set him back quite a few bucks, the AMU removed the H1 because of similar issues. I have a Precision Arms micro on my .22 but that's different application. Thought it maybe better to find the problem before spending more money on another sight. He might want to check Parallax though I don't know how that will change after 1000ish rounds. Maybe a lens is getting loose.
 What I'm thinking is the real problem is that the action shooters like IDPA can put anything on and it work for them due to that they can't shoot good anyway. Missing the complete target at 5 yards so a few inches at 25 means nothing to them! So the industry is happy with selling junk forgetting the Precision shooters.

Yes I love it when writers say it is really a fine piston it shoots 2 1/2" off the bench at 25 yds.  Don

Froenek, the adjusted elevation and windage are within 20% of center of travel.  These flyers are a good 6 MOA from the main group @ 50.   If mounting is the problem I should be able to "feel" it.  Everything is blue Loctited and tight.   Maybe it's time to call Udot for heart-to-heart.

Oh OK, rereading you post I see the problem started at 50 yards. As I mentioned before I have no knowledge of the internals of micros. Maybe someday I might get a cheap one on ebay that don't work and take it apart. I agree with you Bigt that the problem is with the Udot. The one thing I don't like with the micros is the attachment method. The built in attachment and no rings seems to not be a good idea. Most rings are made from a good Aluminum alloy yet the micros are die cast Aluminum that is usually of poor strength. I'm thinking that the screw will pull the Aluminum tight to the base but only at the head area of the screw and from shooting the outer ends creep away from the base and allow the scope to pivot causing a windage change due to recoil. Wouldn't be easy to feel since only a few thousandths in pivot will cause quite a bit of change especially at 50 yards. As you continue shooting the problem gets worse. A possible test would be to loosen the screw, apply rotational pressure and tighten the screw, fire a shot the again loosen the screw and do the same thing and keep doing it over for a 10 shot group always applying rotational pressure in the same direction. If the group is good then possibly do the same thing again but 5 shots in one rotational direction then 5 in another.
 Not that will be good for shooting but will be a point to make when talking to Udot as I'm sure they will say there is no problem with the scopes.