b-square or tap a m-29

I have a m-29-4 Whitetail Hunter 8 3/8 barrel that I would like to mount a scope on . I had an aimtech mount that was nothing but a problem shooting loose . I don't know how collectable the gun is but was told drilling and tapping will destroy all collecter value even though firing the 50 rds. already did that . Anyhow I can get a b-square no-gunsmith from a friend for like 20.00 bucks that he had on a 586 and the box says it will fit a 29 . Question is will it hold up to full magnum loads for deer hunting even though most shooting will be done with mid range loads ?

My experience with B-Square has been positive. For $20, I would try it out. If it doesn't work out you can sell it and have your 629 drilled and tapped.......

Are you are talking about one of those older B-square mounts that have the front barrel clamp set up? I always thought they were a bit of a rinky-dink set up until I closely examined one. I used to tease a fellow shooter that had one on a K-38. Actually, the base locks on to the frame very securely. For an older non-magnum revolver that you don't want to drill the topstrap, I say OK. I'm not sure about a 44Mag. This mount is only held on to the top strap with a couple of very small screws, although the rear attachment is a rather clever wedge design. The barrel clamps just kind of center and stabilize the mount. I would think you would have to be very diligent in checking the screws for tightness to maintain a scope zero. I would call B-Square and ask them about your application.

Thanks ,the mount is one that has the clamp on type and I'm curious if there would possibly be blueing wear from the barrel vibration of the round going off . I have seen used guns ( stainless) that had marks and because of location I assumed it came from a mount ?

If the mount is a "clamp on", I wouldn't. I'd drill and tap the top strap under the stock sight to match the newer guns. To me that's a "lesser evil" vs the damage the clamp on mount will do to the blueing, aside from it probably not staying put.

tomcatt51 said:

If the mount is a "clamp on", I wouldn't. I'd drill and tap the top strap under the stock sight to match the newer guns. To me that's a "lesser evil" vs the damage the clamp on mount will do to the blueing, aside from it probably not staying put.

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I'll second that recomendation. In addtion, any value as a "collectable" for a model 29 is probably 40 or 50 years away. Take a look at how long it was before the Registered Magnums started to genterate interest and prices that matched it's rarity. The RM's really didn't take off until the early to mid 80's.

I also think that with your long barreled version having the frame drilled and tapped to the current mounting pattern may add to it's value. It's a handgun that was intended for Hunting, so making a small addition to it's features that improve it as a Hunting Hangun should make it easier to sell and thus increase it's value. Just make sure you have it drilled and tapped to the pattern S&W is currently providing on the new guns because an oddball pattern won't match the rails now on the market and will probably reduce it's value.

Good question about possible blueing wear caused by movement of the clamp. Even though the clamp is only anodized aluminum, I guarantee you that barrel does slide and whip inside that clamp under 44Mag loads. You may wish to try a bit of tape between the clamp and barrel for protection while you analyze just how much movement occurs while shooting. Before you think about drilling and tapping your top strap to match the current factory pattern, make sure you have enough room for that forward most hole. On older k-frames, drilling the current 3-hole pattern will run that forward most hole right up beside the hole that attaches the rear sight to the top strap. I am not sure if you have room on your 29. I have a 617 and a 14 that have only two holes tapped to secure a current pattern scope mount. I have had no issues with the base getting loose. But then these are lightly recoiling guns...........not a 44Mag!

tdan said:

Before you think about drilling and tapping your top strap to match the current factory pattern, make sure you have enough room for that forward most hole. On older k-frames, drilling the current 3-hole pattern will run that forward most hole right up beside the hole that attaches the rear sight to the top strap. I am not sure if you have room on your 29. I have a 617 and a 14 that have only two holes tapped to secure a current pattern scope mount. I have had no issues with the base getting loose. But then these are lightly recoiling guns...........not a 44Mag!

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I have to take exception to this statement. While this may be the case with K frames that predate perhaps 1980, it's not the case with the more recent K frames. I've seen some posts that indicate the S&W has played around with the screw position for mounting the target sight assembly 2 or 3 times in it's history, so on older guns there may be an overlap. However on those guns that use the most recent square fronted target sight assembly, I have not seen any that would overlap with the current 3 hole mounting pattern.

One tip for the K frames, if the mounting hole for the sight is forward of the rear surface of the barrel, the new pattern will fit without any concerns. However, on the K frames that new forward hole will just barely scrape the rear of the barrel if you run the tap in deep. For a tap this small, hitting the barrel will snap the tap, so I have biased the mounting pattern towards the rear of the gun by 0.025 inch. Below is a pic of my model 67-1 produced in 1988 with the standard 3 hole mounting pattern and that 0.025 inch shift to clear the barrel. BTW, I've performed the same exercise on my 617 no dash and the hole layout matches the 67-1. Note, those 2 pre-spotted holes were due to a "blonde moment", so just ignore them.

As for the N frames, on the recent guns it should not be an issue, that forward hole will be well back from the rear surface of the barrel and no pattern shift is needed.



Now for the dimensions for the pattern used on the newer guns. Note, these dimensions include that 0.025 inch shift mentioned previously. All dimensions are from the vertical face of the notch cut into the top strap that the adjustable sight nests into. The dimension for the front hole is 1.750 inch from that face to center. The dimension for the middle hole is 1.150 inch from that face to center. The dimension for the rear hole is 0.485 inch from that face to center.

Can't just finish the front hole with a bottoming tap?

Thanks everyone , this is why I joined the forum .If a question is asked about S&W's the help is always there and my knowledge has greatly increased .I believe I will drill and tap and I'll relay this to you . I ran into a guy at the range with a m-19 with a 6 in. barrel and wear marks on the front of the frame . He said he had a weaver no-gunsmith that never was a problem but when it came off there was blueing wear and he sad he had a 617 no dash that did the same but its easier to dress up stainless . Vibration must be an issue ? And thanks scooter123 for dismanteling your sight for the pic .

<Below is a pic of my model 67-1 produced in 1988 with the standard 3 hole mounting pattern and that 0.025 inch shift to clear the barrel.>

While shifting the scope base to the rear to give clearance for that rear sight screw hole may work on a 617 or lightly loaded .38, this would be a VERY POOR idea for a 44Mag. All of the scope bases made for the factory drilled/tapped S&W revolvers have a recoil lug that butts up tight to that rear recess in the top strap where the rear sight assembly fits.........even the cheap Weaver 401. I am a big fan of Weigand scope mounts. I have a bunch of them. You may wish to give Jack Weigand a call, and get his advice on your specific gun. If you do decide to PROPERLY drill/tap your 29, make sure that your gunsmith does this on a milling machine so that recoil lug is dead nuts tight on that rear sight recess of the top strap. If all he has is a drill press, run...........don't walk away. You don't want to be the one having to live with some pretenders "blond moment".

Tomcatt, the front hole can be finished with a bottoming tap series. However, at a cost of 24 dollars for each tap this can get to be somewhat expensive. In addition, you won't easily find a bottoming tap series in the #6-48 size, most likely they will have to be made by progressively grinding the tip back on 2 of the 3 taps to make the semi bottoming and final bottoming tap. Finally, it's always risky trying to cut a bottoming tap hole and it a size this small it's a distinct invitation to a broken tap.

Tdan, you have a good point and it's worth noting. In hindsight I've found that the mounting screws supplied with most rails don't require that the holes have the threads formed fully through the top strap. So, I really didn't need to run the tap for the forward hole all the way past the barrel. However, I didn't have the advantage of this knowledge when I did the work and I was concerned that the tap might bind on the barrel and then snap, so I saw no harm in shifting the pattern to the rear to insure this didn't happen. BTW, I used a Bridgeport vertical mill equipped with a DRO to do the work and also reamed the drilled holes to size before tapping to insure a perfectly sized hole. With taps this small, breakage of the tap is a serious concern, so I made quite certain that didn't happen.

As for that blonde moment, I initially thought that overtapping the existing hole would be a good idea, then I realised that would result in a non standard pattern that wouldn't fit a pre-drilled rail. Fortunately, after a bit of thought I realized that would be a mistake and used the standard pattern. As for the N frames, the frame window on the N frame is long enough that there is not concern that the forward hole will intrude on the barrel so no pattern shift is needed. As can be seen in the pics, there is at least 0.10 inch of web between the holes with the pattern shift applied, so tapping an N frame without any pattern shift won't have a problem with the tapped holes interfering, as long as it's an N frame of recent vintage. For someone considering tapping an older gun, I would strongly suggest laying out the holes before doing any drilling. Anyone doing an N frame should just take those dimensions and add 0.025 inch to them to obtain the current factory pattern. As for a K frame, for a 357 Magnum I'd use the standard pattern without the shift and be very very careful when tapping the forward hole. On anything milder, I'd shift the pattern just for the extra margin of safety while tapping. The simple truth is that a broken tap will probably cost 100 bucks to have removed via EDM machining.

You should also note that the dimension baseline I used is that key vertical face that you refer to. While I'll admit to the occasional blonde moment, I do take the time to think things through before committing myself to something like this.