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Old 10-12-2021, 08:56 AM
teletech teletech is offline
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I've got a 29 with uneven throat sizes I need to uniform, but I'm not clear on best practice.
Let's assume for the moment I want match accuracy out at 100 yards.
The current range is from .429+" to .432" (yes really, and no it's not a new gun, so while S&W should be ashamed, we're just rolling with it.)
How hard do I expect this cylinder to be and will I have any trouble with HSS tooling?
Do I ream from the front and follow the existing hole, or is it better to ream from the charge hole side and follow the chamber cut? They should of course be the same, but depending on how the cylinder was made this may or may not be the case.
The obvious choice as a machinist is to simply grab a straight reamer and go for it, but of course straight reamers really do prefer to cut a bit more material than just a thou or two, it's also likely I'd have to buy that size. Can I just use one from McMaster, or do I need something fancier? Alternately, is it reasonable to use an expanding reamer since I already am likely to have one?
I could also set up a boring head and go that way, but of course that's more work.
Or, should I try to buy some special reamer that pilots on the chamber rather than the existing throat?
The current barrel measures .434" in the grooves with no real constrictions, so I'll try it out but I'm also open to replacing it if once the cylinder is dealt with I'm still not happy with the accuracy.
I know it's a lot and I might well be overthinking this, I just want a solid plan before I start making chips. Thanks,
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Old 10-12-2021, 09:27 AM
Bekeart Bekeart is offline
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Default You have the correct plan

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I just want a solid plan before I start making chips.
I have no opinion or knowledge that applies to your query.

I do applaud you for planning ahead.

Bekeart
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Old 10-12-2021, 09:58 AM
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how you really 'measure' groves and throats...I would really make sure you know the throats and also the tight throat is really really clean. Once you take tools to it you likely won't be able to find matching bullets for it. IO know a source for .432 bullets but no larger than that.
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Old 10-12-2021, 10:15 AM
Protocall_Design Protocall_Design is offline
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I would get a .432 reamer from McMaster-Carr (#8803A839). Check the face of the cylinder for squareness by holding it in the lathe chuck with a dial indicator on the face as you turn the chuck with cylinder slowly by hand. If not square (many aren't), face off just enough to clean up.

In the mill or drill press, set the cylinder with the front down and ream from the back. Use a slow spindle speed, in the 100 to 150 rpm range. Use plenty of cutting oil on the reamer, and feed down slowly. The metal will cut easily, go by the feel of the cutter. Going from chamber to throat, the taper between the 2 sizes will guide the reamer to the center of the hole. It should take 5 or 10 minutes to do all the holes. It's an easy process, but you have to do it right, you only get one chance.

Having said all that, you won't get good groups out of a .432 bullet in a .434 barrel. You always want to be going down in size from chamber to barrel. For example, a .430 bullet in a .430 throat to a .429 barrel. You can go down 2 or 3 thou. pretty easily even with jacketed bullets. I'm shooting .357 JHPs in a .355 barrel with very good accuracy.

You can have a tack driver gun if you change out the cylinder and barrel to good ones and make sure the chamber lines up with the bore, good forcing cone and muzzle crown and no barrel constriction. If everything is mechanically correct, the gun will shoot almost any load well, and some loads exceptionally.
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Old 10-12-2021, 10:40 AM
teletech teletech is offline
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Good reminder on checking squareness. I am not too keen on having to do bluing repair on a highly visible part, so if it's bad I might just go cylinder shopping and hope that saves me the cost of a reamer.

Indeed, it is true that I don't expect great things from the barrel given it's size but I figure I can swap it later. My test firing from individual chambers suggests that with some .432" bullets in properly sized throats it *might* be tolerable. I was surprised to find .430" nominal bullets shot better out of the .429" cylinders than the .432" ones. I'd have thought the even looser fit in the rifling would have made it worse. I've got .432"s on order.
I've already got one .44 that wants .432"s, so it's not the worst thing.
I did find casters who will do .433" and even .434", but I'd rather swap a barrel than have something so hard to feed.

That said, I'm obviously barrel and cylinder shopping, but with mail-order parts you get pot-luck so I've got no idea if what I'd buy would be any better than what I've got.
Selling this one and buying one at a show that I've more carefully inspected *could* be an option, but then I'd have to: find a blued 29 in good shape for a fair price in a barrel length I want, and then sell this one.
Selling would sort of be kicking the can down the road. I mean, sure, I'm sure many folks just want a pretty 29 to look at and can't shoot better than 5" at 25 yards, if they ever went out farther than 7 yards, but I'd feel a little dirty charging 99% 29 money, considering. I'd just as soon fix this one.
Looks like $100-200 for a cylinder and $150-250 for a barrel, but the challenge is getting good ones. After all, they could have been removed for a reason....
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Old 10-12-2021, 10:50 AM
Protocall_Design Protocall_Design is offline
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What barrel are you looking for?
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Old 10-12-2021, 01:32 PM
teletech teletech is offline
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What barrel are you looking for?
4", blue, non full-lug.
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Old 10-13-2021, 10:03 AM
Protocall_Design Protocall_Design is offline
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I have a few, but not that one.
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Old 10-13-2021, 08:45 PM
rkrcpa rkrcpa is offline
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.44 Special Throating Cutter - 4D Reamer Rentals

This might be of interest
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Old 10-13-2021, 09:15 PM
M29since14 M29since14 is offline
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I strongly suggest you skip the reaming idea and send your cylinder to a shop that can hone it for you using proper equipment. That specifically would NOT be a “flex hone.”
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Old 10-13-2021, 09:41 PM
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a 4 year machinist will know how to use and sharpen a reamer. lots of oil and slow turning.
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Old 10-13-2021, 11:30 PM
series guy series guy is offline
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Before doing anything try loading up some plated or jacketed bullets. I have found that they can make a huge difference in accuracy in guns with oversized throats.
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Old 10-13-2021, 11:53 PM
bruce381 bruce381 is offline
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go to 4 d rent the correct reamer then you will know its right.
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Old 10-14-2021, 08:28 AM
series guy series guy is offline
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Let me expound on my previous post. Ten or so years ago I picked up a Model of 1988 625. I was pretty stoked. During the first trip to the range I found it patterned instead of grouping. So I tried some different loads without success. Then a friend mentioned that he had good luck with plated bullets. I bought a box and loaded some up. That was the key. This gun now shoots extremely well even with the .432 - .433 throats. I added an ebay $30 Propoint and my wife used the gun to win our club pin shoot for 5 years running. I finally updated the optic to a Fastfire III. This target is 20 yards D/A.
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Old 10-17-2021, 09:14 PM
teletech teletech is offline
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That's an interesting resource, thanks for the link.
They list that one as cutting to .431", but I'll reach out and see if they have larger so I can uniform mine.
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Old 10-17-2021, 09:22 PM
teletech teletech is offline
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I strongly suggest you skip the reaming idea and send your cylinder to a shop that can hone it for you using proper equipment. That specifically would NOT be a “flex hone.”
Pretty sure nobody even floated the idea of a flex-hone. I did mention an adjustable reamer, but of course that is nothing like the same thing but rather a bladed reamer with tapered blades and tapered slots in the body so one can adjust the cutting diameter. They used to be rather common, but I fear have gone out of fashion these days. I checked and don't have one that will go to the requisite size anyway, so the McM reamer is pretty attractive at this point.
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Old 10-17-2021, 09:34 PM
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My old 625 shot great right from the get go, it was a Colt Anaconda in .45colt that patterned for me until a friend gave me some plated bullets to try. Bingo. Next time I reloaded .454s for it and got great accuracy. Used them in bowling pin shoots.

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Old 10-18-2021, 09:22 AM
Protocall_Design Protocall_Design is offline
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Pretty sure nobody even floated the idea of a flex-hone. I did mention an adjustable reamer, but of course that is nothing like the same thing but rather a bladed reamer with tapered blades and tapered slots in the body so one can adjust the cutting diameter. They used to be rather common, but I fear have gone out of fashion these days. I checked and don't have one that will go to the requisite size anyway, so the McM reamer is pretty attractive at this point.
You can still get the adjustable reamers, but they are fiddly to get set to an exact size, and sometimes chatter in the cut, even when turning by hand. For this type of work, you are far better off with a solid, ground to one size reamer.
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Old 10-18-2021, 04:52 PM
rkrcpa rkrcpa is offline
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You could also just send it out to be honed, Dougguy over on Castboolits has an impeccable reputation.
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Old 10-18-2021, 06:06 PM
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I might have missed this, but how accurate is it now? Is there a performance-related reason you want to modify it?
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Old 10-19-2021, 01:17 AM
teletech teletech is offline
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I might have missed this, but how accurate is it now? Is there a performance-related reason you want to modify it?
Sadly, there very much is, the gory details are here:
29-10 accuracy potential?
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