Do Colts Open Tops Shift POI?

[Smokerr]

I had two previous sessions with the 47 Walker and my home built front sight. The unmentionable cylinder was hitting 5 inches high, BP cylinder quite close at a tad low.

Today, the unemotional loads were hitting pretty close to POA, got some decent groups.

So the $64 question is, can that shift if the barrel seats differently in regards to key and arbor?

 

[KingOfKindling]

I had two previous sessions with the 47 Walker and my home built front sight. The unmentionable cylinder was hitting 5 inches high, BP cylinder quite close at a tad low.

Today, the unemotional loads were hitting pretty close to POA, got some decent groups.

So the $64 question is, can that shift if the barrel seats differently in regards to key and arbor?

Yes. If the arbor is too short you will get a bunch of variation in vertical spread. Every time you seat the wedge it'l be a bit different, and if it's bad enough, it'l move around as you shoot.

When the arbor is short, if you drive the wedge in further, it'l raise the point of impact. Only good way to avoid this is to correct the arbor length.

 

[Smokerr]

I do have it shimmed. Oddly it was consistent high with unmentionable and not shifting around cylinder change to cylinder change. . I am trying to be consistent with the smack to seat the wedge

Other thought was sight picture but not sure why I would change it as I know to fill the notch with the sight and even on the top. Vs why would I shift even not intentionally with the BP cylinder.

A bit baffled but the groups were better today as well.

 

[KingOfKindling]

I do have it shimmed. Oddly it was consistent high with unmentionable and not shifting around cylinder change to cylinder change. . I am trying to be consistent with the smack to seat the wedge

Other thought was sight picture but not sure why I would change it as I know to fill the notch with the sight and even on the top. Vs why would I shift even not intentionally with the BP cylinder.

A bit baffled but the groups were better today as well.

Is the arbor length exact? If it is, it shouldn't matter how hard you drive the wedge in, unless you're doing it hard enough to actually smash and shift metal.

 

[Ed C.]

Sometimes it seems bullets go where they want, but usually it is us. Any small thing, trigger pull, lighting on the sight picture, a little more or less shaky, etc. Even shooting off the bench can have human factors involved.

 

[Uncle Miltie]

It's inherent in the design and the main reason you will almost never see them in MLAIC matches.

 

[45D]

It's inherent in the design and the main reason you will almost never see them in MLAIC matches.

It's inherent in the Uberti execution of a most excellent design!!
If the arbor length is correct, the sight line will be the same every single time.
Smokerr, if you have a CORRECT spacer that's actually thick enough, the poi will be the same every time. A HARD tap isn't the same as screwdriver handel tap. If the wedge isn't driven in, it can vibrate around and allow changes from shot to shot. If a hard tap locks the cylinder up, the spacer is obviously not thick enough.
It's a lot easier to start with a "too thick" spacer and thin it down to what you want your endshake to be. Shimming UP to get your endshake isn't a good way to achieve the same thing.

Edit: otherwise, you couldn't shoot five shot groups like this (shot in blue circle was from a different grouping/ different revolver).

Mike