New Failure Mode (for me)

At the range testing my Perry ammo and nothing was on the paper. When I wiggled the scope to see if something was loose, it came off in my hand. After only 15 years and who knows how many 10's of thousands of rounds...

I remounted the scope on the front section, which will get me through Perry.

Wow! Unbelievable that the thing didn’t come flying off on its own.  Two immediate questions come to mind.  

If that’s the original dot sight, what brand and model? 

Second, what’s the warranty on that frame mounted rail?

That is one of Jack Weigand's mounts. Pretty good stuff in my experience.

Nothing a little duct tape couldn’t fix.

Nothing that can keep you down from Perry! It's fortunate this happened before and not during

Most if not all bullseye rails aren't cut to true picatinny specs where most of the dots we use are made for them. I've had issues before, would sure make it easier if they were true to picatinny specs.

RodJ wrote:Wow! Unbelievable that the thing didn’t come flying off on its own.  Two immediate questions come to mind.  

If that’s the original dot sight, what brand and model? 

Second, what’s the warranty on that frame mounted rail?

I hope it was obvious that my second question was firmly tongue in cheek. If not, my apologies!

Nothing made from aluminum is 'for ever'.

The gun was not dropped of hit. It has been used a lot.

It isn't completely clear, but to me it looks like fatigue from the top down, maybe from both sides until there was about 1/16" of material, then it is a sudden break. It looks like it started from the bottom of the first cross bolt cut behind the main body of the mount. It makes sense that would be the highest stress area.

Are there good reasons to use this kind of mount, rather than mounting a typical rail, such as the one that is sold by Jon Eulette, to the slide?

mikemyers wrote:Are there good reasons to use this kind of mount, rather than mounting a typical rail, such as the one that is sold by Jon Eulette, to the slide?

Keeps the dot from cycling with the slide, which promotes better life of the dot, less chance of a wandering zero from improper torque or no Loctite on dot mounting screws.  You can also look at for similar weight pistols, one with a frame-mounted dot has less mass cycling above the shooter's hand, resulting in less affect on recoil recovery.

I currently shoot a slide-mounted Matchdot,
 
but have had frame-mounted in the past, bot for Bullseye and USPSA.  This mount look familiar?

I don't feel qualified to suggest which is better.   But as an un-qualified shooter, the weight of that large plate with mounting screws is probably more than what I think is Jon's rail in that top photo.  (I bought one of Jon's rail, then two more.)

Assuming the weight of the sight is important, which certainly sounds reasonable, why don't more people use the 1 inch model of the Ultradot sight, or lighter yet, the Aimpoint Micro?  The one-inch sight is just as bad as the 30mm version when it comes to reducing the apparent size of the image of the target, but the Aimpoint shows the target at 100% size.  Of course the Aimpoint costs more.

Back when I barely knew how to spell the word Bullseye, people discouraged me from using a side mounting plate.  I don't remember all their reasons, but since then I've never even considered using the plate.

Final thought - weren't the top records for Bullseye Competition achieved with open sights?

Mike, I think that frame mounts were the thing in the day of more delicate dots and optics. It also did not require “rebalancing” the firearm to shoot a dot.  Now we have better more robust dots so the advantages of a frame mount are gone.

Probably the reason I prefer a frame mount is because my first bullseye gun had it and I am used to it. When I bought this gun in about 2005 or 2006 I started with a rail. I tried to adapt to it for a year, but the extra weight on the slide made recovery back to the target so slow I never liked it.

With a frame mount there is less moving mass, so the recoil is sharper and faster, more of a kick or snap. With a slide mount recoil feels more like a shove or push. The peak force may be lower, but it lasts longer. 

A frame mount gives a little more freedom to use loads that would be too light to cycle a slide mount.

On the other hand frame mounts may be slightly less accurate because the slide-to-frame fit is a additional source of error. I don't think that amounts to much, but it is commonly accepted.

The total weight of a frame mount is probably slightly more than a slide mount, but it's not much.

Wouldn't have happened I bet with a scope with a front and back ring.  
Totally on the back there is like a fat man on a diving board.