Super Blackhawk and scope mount

[blackdragon]

I've recently been trying to mount a scope on a Super Blackhawk.

I purchased the weaver base and rings, mounted the scope, and shot it. It was OFF; 10" high and right at 15'.

After (far too) long of checking things out, I think the gun, not the mount, rings or scope, is off.

If I set the gun so that a level shows the rear-most part of the frame is level, the front of the frame is off, by a fair bit.

I've tried to use calipers to see if I could find a measurable difference between the sides, so I can tell where I should shim, but I haven't found any.

Is there any part of the revolver that I can use as a 'true' point to compare the top frame to?
Could the frame be twisted?

Keith

 

[444marlin]

is it a SBH hunter or a standard SBH? I have not seen a scope mount for a standard SBH and I would not think the way Ruger machined the mounting points on the SBH hunter that anything could be off with the gun. if it is a standard SBH how does the scope base mount to the frame? does it use the rear site screws?

 

[blackdragon]

It is a standard blackhark -- weaver makes a special mount for them

It is similar to the pic at http://www.gunaccessories.com/Weaver/PistolMountSystem.asp
, except that the two 'prongs' are in front of the forward ring instead of behind it.

the prongs are actually slightly circular, and hold to the barrel; the base screws to them. It has two sides right behind the prongs that tightly fit over the sides of the frame, and also screws into the screw hole that holds the rear sight (which must be removed).

The mount is more solid than I expected; if it actually lined up properly I would enthusiastically recommend it...(well, after a few more test shots, anyways)

Keith

 

[Majic]

A lot of the clamp sight bases move during the recoil of magnum loads. It doesn't take much and that could be your problem. I doubt that your frame is warped. Was the revolver an accurate shooter with the iron sights?
A much stronger and sturdier mounting system would require you to drill and tap the topstrap. You then wouldn't have to worry about mount shifting. The mount should be firmly anchored in 2 places, not just one.

 

[BlkHawk73]

Are there actually any screws holding the base to the frame? I've never seen that type of mount and wonder about the possible movement of it. I'd think there would need some attatchment to the rear part as well. I also notice that there isn't a listing for any heavy calibers on the linked site. The only Ruger SA's listed are the Single Six and the SRm (which is a unique frame by itself) This could indicate that this mount isn't intended for such recoil.
All the Ruger mounts I've seen are securely mounted with screws to the topstrap by removing the rear sight and drilling & tapping for anothe on the front of the topstrap. I use this setup and have no problems with movement.

 

[blackdragon]

I don't think the base is moving....the groups are tight.

I have not fired the revolver with the original sights ( It is not mine, I'm mounting it for someone else), so I cannot attest to it's normal accuracy.

In the pic, we have a screw at the back at 'D', where the rear sight was, and a large one at 'E', holding the base to the barrel. The one I got is for the Super Blackhawk; that was the first link that I found that actually had a pic; I should have found a more relevant one. (For those who wondered how the base attaches)


If I put the run in a rest, and use a level, the flat points at 'A' and 'B' are both level ( or very, very close), but 'C' is not..the right side is low by 10-20 thousands. ( or, are 'A' and 'B' high by 10-20 thousandths??? does it make a difference??)

Since the mount contacts the frame at 'B' and 'C', I'd have expected that they should be even; with them uneven, I do not see how the base could fit correctly.

I shimmed the right side at 'C' by approx 10thousandths, and the POI moved almost half the way back to POA.

I'm guessing the best course of action is to re-center the scope, shim the base until it appears perfectly level, and the POI is as close to the POA as I can get, then adjust the scope the rest of the way.

Having a reference point to adjust to would be best, but I dont know how to ensure that the bore is level (barrel is tapered, so outside of barrel won't work). Would the point at 'F' (cylinder out..) be paralell to the bore? Or is there a more obvious way to do this?


Keith

 

[Majic]

You could machine a brass rod to fit the bore and insert it thru the forcing cone for a bore reference.

I have heard shooters complain that systems that uses barrel clamps sets up just fine, but in time shoot loose with heavy recoil. The large scopes pull on the mount with each recoil.