I did a careful measurement of the cylinder throats on my 629-4 MG today using an expanding ball tool and a micrometer. It seems that they are .4293 give or take a tenth or so. My bore groove slugs out at .4296-.4299. It would appear that I need to have the throats reamed out a bit. I have seen a link here to a fellow who calls himself Cylindersmith, has anyone used his services and is he still doing it? Another question. When I shoot .430 jacketed XTP bullets out of this gun what is it doing to the cylinder and to the pressures getting through the throat? If I have the throats reamed out to .4305 will the gun have problems shooting .429 jacketed bullets accurately?

I don't see a problem here requiring reaming. I would leave it alone unless you are having accuracy problems.

You could have it reamed out a bit but I think you'll be wasting your time. Your looking at .0007 which is insignificant. If you are capable of measuring that accurately to begin with. Remember you have 40,000psi pushing that bullet through. Throat dia. is a known problem in some revolvers, in some calibers, not yours.

Well, it is good to know that it probably isn't needed. Back at the beginning of time I was a mechanical inspector, 1st articles and what not coming from machine shops so I am pretty sure about my numbers, particularly the throat diameters. Since the bore has 5 grooves that dimension is a little harder to be sure about but the fit of the slug through the throats, (very tight, goes through with a light hammer tap but not by pushing), leads me to think my figures there are good also. My main concern was in shooting cast bullets so I think I must just load and shoot a bunch to get a good idea. Thanks.

I've been lurking here for years but post very little. I prefer to learn but this is a subject I'm very much in touch with. I carry plug gauges in my range bag at all times and at gun shows when I'm looking to buy. My personal experience runs the gamut from early p&r guns up to current Performance Center guns. Most every p&r gun I've measured has been in the range of .432 - .435 and none of them were consistant good shooters. Sure there were some good groups but just when I was happy wth the load bullets would start flying all over the target. After 3 or 4 different 29's and 629's I wasn't a very happy camper and I had alot of money tied up. I settled on a 629 with .432 throats and custom cast and sized .432 240gr. bullets. Then a fellow club member bought a used 629 classic and the throats measured .429. I was really excited with this discovery and volunteered to sight the gun in for him. The groups were fantastic. We used a .430 240gr. cast bullet. I lucked into a chance to buy a 629 Classic for a good price so I sold my original 629 and bought the Classic. It shoots excellent with .430 cast bullets and .429 throats.I then had a chance to buy a 629 Stealth Hunter. The throats measure .4285 and it's a tack driver with the .430 bullets. Over the past 2 years I've measured 90% of the guns that come through the doors at the pistol range and from the Classic series onward the throats all measure .429. All the Performance Center guns I've measured are right at .4285. I'm sure there's a limit here but as far as my experience goes the tighter the throats the better the gun will shoot. I've also done this with .45 Colt, .38 Special, and .41 Magnum with the same results. Remember this is for cast lead bullets. Jacketed or copper plated is a whole different animal due to the difference of friction between the two metals. The throat size is not nearly as critical with copper. Just my .02cents worth.

With that info I will definitely NOT have them lapped bigger and consider myself lucky to have them as small as they are.

It depends on the groove dia of your bbl & what size lead bullet you want to shoot. If you are shooting a 0.431" lead bullet, the smaller cyl throat is going size it down & you will get leading & marginal accuracy. Polishing out to the dia of the bullet you are going to shoot &/or groove dia is perfect. I have a machinist friend do mine, he specializes in ID/OD polishing, easy to do, takes about 15min for the whole job. It will not affect your jacketed bullet shooting at all. Many S&W rev have larger than groove dia cyl & they will only shoot jacketed w/ any real accuracy.
A recent RBH I bought had tight 0.450" throats I was shooting 0.452" bullets. Accuracy was marginal & always leaded the first 1" or so, why not, the bullets were coming into a 0.451" groove 0.001" too small. After polishing to 0.4515", leading is almost completely gone & accuracy is twice as good @ 25yds. Yeah, it can help quite a bit.

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I have several Smith 629's that have cylinder throats that measure.4285. Since I also have Smith's and Rugers that have throats that measure .431, I size all my boolits to .431. The .431 boolits shoot extremely well, (if occassional 5 shot groups of less than 1"@25 yds with a scoped Classic DX is good!) and I get little or no leading. Sure makes life simpler than wringing my hanky about "proper boolit to match throats" diameters.

Then you are fortunate as it doesn't work that way for many lead bullet shooters.

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Ok, it certainly makes sense that if the throat size is less than the groove dia. then gasses will get by and melt lead and deposit it in the barrel. But, it doesn't seem to do it for everybody. There is an awful lot of pressure behind the bullet, maybe not 40,000 psi, at least not in the loads I am using but surely at least 25,000 psi. Is that enough to deform the bullet and seal the bore? Seems that the answers are not simple.

That depends on the BHN of the bullet you are shooting, a choice that is also important, depending on the other factors. Flapjack.

SAAMI spec for 44mag is 36,000psi. As you can see opinions and results vary greatly with everyone sure they have the right answer. In my opinion with max pressure and bullet expansion occurring soon after ignition and probably before the bullet passes through the throat that no bullet expansion occurs after the bullet passes the cylinder gap so whatever size the throat is the bullet should remain that diameter through the barrel. I don't think there's enough pressure left to expand the bullet once it reaches the barrel. If I'm wrong on that then it adds another layer of complication to throat size. Is it possible lead is soft enough to still expand and copper won't?

A copper jacketed bullet won't obturate, neither will a very hard lead bullet, so throat size may or may not matter to accuracy, but can play havoc w/ leading. The only way to get the over size, throated S&W 45colts to shoot well is shoot jacketed or a very soft, oversized lead bullet.

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Perhaps my "good" results are due to the hardness of my alloys? I use boolits that measure Bhn 11, which I cast myself and adjust my alloys to reach that by the use of a Saeco hardness tester. It seems to me that a lot of folks run into leading and accuracy problems with diameters due to their use of commercial or home grown "hardcast" or quench cast boolits, whatever "hardcast" is defined to be.
I've always maintained that shooting cast boolits ain't a science, it's an art, and I'm still learning after playing around with them for 48 years!

When you think about what is occurring when you shoot a cartridge it is amazing that it works at all. It is a little like the physics of hitting a golf ball. With all the variables such as club angle, where on the face the ball is hit, speed of the club, etc, it isn't possible for anyone to do it but they do none the less.

I think a little of both. Many that shoot commercial "hard" cast will have leading issues. Casting your own allows size & alloy control for a better result, but casting is not for everyone & getting more expensive every year as cheap alloy dries up. Thank you the State of Kalif & the EPA.

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Hi,

I have 629 MG and recently starting loading cast bullets since I live in Mass and getting components for ammo has become a real challenge.

My first batches resulted in some fairly extreme leading problems, 240gr SWC with 12g of Blue Dot. After half a box the grooves were no longer visible. This was a load worked up by a relative who had good results with it.

I first started looking at my lead alloy since this was a new load for me, and then asked my relative to put some through his Ruger. He had no issues at all with the ammo.

We then took a look at the throat dimensions and I was surprised to find the throat was so tight, similar to what the OP was reporting. After measuring the cast rounds (.430) it seemed awfully tight in comparison with the throat. The Ruger was relatively loose so much so that the .430 cast bullets could be dropped through the cylinder with ease whereas my Smith couldn't even get the bullets started.

To be able to shoot cast, should I be resizing the cast down to .429 or maybe even .427? I really can't afford to shoot purchased ammo, if I can even find it at the moment, so any recommendations would be appreciated.

Thanks,

Dan

Dan, most folks seem to think the bullet should be sized to fit the throats (exit bores) of your cylinder, or maybe 0.001" bigger - as long as you can seat the loaded cartridges in the chambers without a problem. I think the theory here is that the base of the bullet can receive a lot of damage before it leaves the cylinder if it is not a good fit for the exit bores. I tend to agree with this. Whenever my cast bullet loads are properly sized for the exit bores of the cylinder, I have very little trouble with leading and poor accuracy. Just make sure your loads easily "drop in" to the chambers.

The OP's gun sounds fine to me. I would not make any adjustments to the exit bores.

my current loads do drop in the cylinder fine, they are tight to exit though. Based on your comments, do you agree I should try and resize the bullets to .429? My main concern here is to reduce the crazy leading I'm getting. Am I following the right path? I'm not currently looking to mod the gun at all if I can help it.

Thanks,

Dan

A while back, he changed to only doing .45 cylinders. I had sent him a 32 H&R cylinder, but he was unable to ream the throats. So I got a Manson throating reamer and did my 3 cylinders myself. They turned out just fine.

I recently throated my 629-6. As you mentioned it was tight like yours is. I buy my reamers directly from Manson's rather than through Brownells. I do this mainly as they will put on the pilot I want, rather than an undersize one as those sold by brownells. After throating my cylinders were ~0.4315". I shoot 16 BHN sized to .431 and they are just a snug thumb press through each throat. I keep my pressure up on these and get really no leading with excellent accuracy.

As others have mentioned, there are MANY theories on what to do. I'm not going to say someone else is wrong, but I do know what works well for me.

IMO, a 0.429" bullet is likely to lead early in the bbl. It matters little if you size it to that size, the throat will size it for you on firing. An undersize bullet entering the bbl is just that, regardless of how it gets there.
I would rather open the cyl up. Any good grinding outfit can do it. A buddy of mine has such an business & showed me how to run his machine & I did my own on a RBH in 45colt. The cyl throats were very tight, like 0.450" or a bit less. I opened them them to 0.4515" for a .0452" bullet. Accuracy got better & leading was reduce. I am a believer.

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Dan, don't go smaller with your bullets. If necessary, open the exit bores of your cylinder to 0.4300 - 0.4305". The correct way to do this is with a honing machine. Remember to keep your bullets the same size as the exit bores, or a bit larger.

I have not used Blue Dot in .44 Magnums but you might try some other powder before you ship your cylinder off for honing. I am very partial to #2400, though I will begrudgingly admit it is not the only powder for .44s. Give 18.0-19.0 grs. of #2400 a try (standard primers) and see if your leading situation changes. I'd think it would be worth the cost of a pound of powder.

You didn't say exactly what they measured & tight to exit isn't very specific. If you can measure the throats & post it that would be helpful.

My 29-2 has .4325" throats & has always been very accurate with .430" cast lead & 17gr/2400 for some reason. Wish my SRH 454 was as good.

SLightly larger throats are often not an issue. IT's the smaller throats sizing the bullet down before it gets to the bbl. Really excessive throats, like some of the M25s @ 0.455", won't do as well with cast. I size all my 44s to 0.431" for several guns. Better slightly large than slightly small.

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thanks for all the info, sorry for not including the throat diameter.

I measured .428 by running one of my cast bullets through the throat. There was some rebound since I still can't easily push the bullet through the throat but I measured .428 with a micrometer so it's probably slightly smaller yet.

I ordered a .427 sizing die as a trial to see what the effect would be of matching the bullet closer to the throat. I figured that would be a simple test before considering to have the cylinder modified.

Also, another question. I reviewed the SAMI spec and was not sure I read it right but it looked as though the spec was .4325, wouldn't that mean my cylinders were out of spec?

Thanks,

dan

Exactly right, IMO. If your exit bores measure 0.428" I would sure consider opening them to 0.430" for use with 0.430" bullets.

Matching the bullet size to the exit bores is generally helpful as long as the exit bores are larger than your groove diameter. If smaller, the bullet is going to rattle around going down the barrel with the usual problems.

M29,

My plan is to get the exit bores opened up. I ordered the .427 sizing die to satisfy my curiosity since that should leave the cast rounds close to the exit bore but larger than the groove diameter.

I will also try some 2400 with the test loads if i can find any.

Thanks for the info/advice.

Dan

How? I doubt the groove dia is less than 0.429", so sizing the bulelts smaller will play havoc on accuracy & leading. You are going the wrong way. As noted before, if the cyl throats are smaller, that is the size the bullet will be, regardless of what it starts at. The result, it then has to bump bacl up as it hits the rifling. If it's soft enough, it bumps early & you may get decent accuracy w/ a little leading. If it's too hard, they may not bump at all & accuiracy will suffer & you should get leading for the first half of the bbl.
Undersized bullets just do not shoot well in anything IME. SO intentiopnally sizing smaller, why? Fix the gun or don't shoot lead. It won;t matter as much with jacketed, but you'll never get realyl good accuracy shooting an undersized bullel.

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Dan, no, you've got it backwards. It is almost certainly going to leave them SMALLER than groove diameter (as Fred points out) so you want to go the other way with both exit bore size AND the size of your cast bullets. I'd increase both at least to 0.430", always keeping the bullets as large or a bit larger than your exit bores. But don't get carried away! Remember, you can always make them larger - pretty tough to make them smaller.

Don't have too much experience with enlarging chamber mouths, but had two tight-chamber mouth S&Ws done by a professional 'smith. My 696 no dash 3" and 629-4 4" both ran .4280 -.4285 and were at best 2.5" @ 25 yd guns. Now under 2" with lead and factory jacketed, after both relieved to .430.

My .44 mags that are around .430 are definitely more accurate than the one or two that are .432 or .433 in chambers [e.g., Ruger SBH 4.625" @ .433]. [Of course, realize that if bores huge, that is another issue - as with my .41 Ruger BH OM with .410 chambers and .412 bore...].

Regards,

Dyson

I imagine it would depend on the size of the lead bullets you are using. FOr me, nothing a proper lead bullet won't do in a big bore as well or better than jacketed, at any handgun vel. My RBHB scoped will do 3" or slightly better from a rest @ 100yds using a 2x scope with good lead bullet loads. FWIW, your Magnaporting may be the issue w/ lead bullets.

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great info, thanks. I'm just waiting on a reply from S&W before I look to get the throats opened to .430. I emailed S&W asking why the throats are so close to being out of spec relative to SAAMI. In the SAAMI docs, the throat is listed as .4325 +/- .004 which leaves a throat of .428 just barely within. After a reply, I'll be looking to find someone reputable to do the honing.

I am so glad I found this forum because before this I never considered reviewing the specs on my gun. I thought my leading issues were a result of too soft lead. I even went so far as to start electroplating my cast rounds. Came out pretty good too, I was plating 50 rounds at a time with a nice hard shiny coating. I was shocked when I tested the rounds and they leaded horribly too. Live and learn

Getting your bullets the right size for your gun (and/or adjusting the gun to properly sync exit bore size with groove diameter) will make a believer out of you. Small exit bores may work fine with jacketed, I wouldn't know, but I do know they are miserable with lead. "Soft" cast bullets are usually not a problem with most handgun loads unless the barrel is exceptionally rough or the metal has been contaminated.

last S&W I'll ever own. PERIOD. Just got off the phone with customer service and they are the worst I've ever experienced bar none. I may just use this piece as a boat anchor just in spite. I've dealt with other manufacturers and this was my worst experience. Good luck to everyone else on here you have all been most helpful and I really appreciate the advice and assistance.

That sucks. S&W just replaced my cylinder because the throats were too small. I have. 625-8 and they only had it a week. Granted I had to fight with them to send it back, but they eventually did. Not all customer service guys are created equal. I had one guy from S&w tell me to shoot smaller bullets! I told him I wanted to shoot the caliber bullet stamped on my barrel. Call back and ask to talk to a supervisor. They will fix your gun, but if you let a non S&W smith screw with it, your warranty will be void.

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I too would suggest you call again & talk to someone different. When I had to deal with CS for my 325NGs problem, some people were helpful & informative and some were jerks & you just wanted to smack them, but it got repaired. Try again.

ANY good polishing/grinding shop can do this job. All that is require is an ID honer. I did mine @ my friends grinding shop in about 20min after he set it all up & showed me how. A set of pin gages or ID micrometer are the ONLY way to accurately measure cyl throat ID, a caliper won't get it done.

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yah, now that I've cooled down a bit, I might call CS back an try again. I am looking for a shop with a honing machine now in the event that S&W fails.

I verified the throat dimensions with a mic(pushing a lead round through) and gauge pins so I know where I'm starting. I'll try and get the throats to .430. When I manage to get the mods done I'll come back and let everyone know how I made out and the results.

Thanks again folks

You can't go wrong with Bowen Classic link

True enough. Last I knew Mr. Bowen was still doing the work for a reasonable sum. Once the right mandrel is in the machine and trued up, this is such a simple procedure that it is probably one of the "best bang for the bucks" jobs a gunsmith can do. Might check with him. I seriously doubt S&W will do anything with your cylinder as long as it is within the range of the factory's tolerances.

S&W has been cutting the late model cylinder throats tight to boost jacketed performance. The actual SAAMI Spec is .4325 but all the late model 629s I've seen are .428"-.4285". I only shoot lead and fit is a lot more important. I bought the Manson Reamer and opened my 629 throats to .4313" and size bullets .431"+ to match over a .429" groove. After about 200 rounds a couple passes with a stiff bronze brush will knock out a few sparkles of lead powder but that's it. The real surprise was how much better specials shoot. I'm hitting 100m Rams with Specials now (no Mags allowed).

The slight tooling left by the reamer is not an issue. Alignment and constant diameter is more important than perfectly smooth. Polishing will open up throats too but more equipment is required.

Dan,

It's been several years ago, but I have used the services of the "Cylindersmith". I don't remember the actual numbers, anymore, but I know my 629-4 MG had cylinder throats that measured less than the bore. I mainly shoot cast bullets sized to .431 or .432. I had my cylinder throats opened to .4305 (that I do remember), and get good accuracy with next to no leading at 1100 to 1200 fps.

Cylindersmith only does 45 cal. now. At one time he offered 2 sizes of 44 cal throats. Manson made him a couple reamers in sizes not offered in the catalog.

thanks for the additional info, I'm narrowing down a few shops in my area that can do the job. looking forward to getting this done once and for all. Thanks again.

Well, Dan, I just got my model 24 Classic back from the Customer Dis-service department amd they told me the same old song and dance--"it's within spec, no service required". Mine has .428 throats(as per pin guage), and it leads like the devil. On a good day it shoots about 4 1/2" @ 25 yds. I'm no pro, but I can do a bunch better than this 44 will shoot. You can bet you last $ this is my last new Smith. BTW, they test fired my gun but they neglected to send me a target--like I did for them to see.
Murf

my saga still continues as far as getting the throats opened up. I was not able to find anyone in my area interested in opening the throats up so I ended up contacting S&W again. I asked what the charges would be to have them do the work and they estimated ~170$. I'm not comfortable doing this type of work myself so I asked if they could evaluate the piece, knowing full well they won't cover it, and then elect to pay them to do it. Yah, not my first choice but hopefully they can handle it.

That was 1 month ago, they said I would receive a shipping label to send in the piece. After several emails asking ***, I finally received the label and will be sending it in on Monday. They are definitely not the same S&W from years back. Live and learn. When I receive the piece back, I'll update how it went.

Dan

Just curious why you chose to pay $170 rather than $75 at Bowan Classic? I personally would prefer to have Bowan hone them rather than have S&W do the work. The turnaround time will be substantially less also.


From the Bowan site link

No. SW230(*) Hone cylinder throats Undersize throats are adjusted, where indicated, to proper diameter to improve accuracy and minimize leading.

SW230 $75.00

S&W pays the shipping to and from, and according to the Bowan site, the cost for Fedex next day air is 65$ so paying shipping both ways and then the cost of the service ends up costing more. Also, if the planets align and they actually agree to cover the cost of the mod then I end up paying nothing. I know this isn't gonna happen but worth a shot.

Thanks for the additional info though

I believe you made the best choice, though I understand your reluctance. Hopefully you'll be peasantly surprised. (I'm sending my 657-5 back Monday too because the chambers are oversized causing case bulging.)

Previously I looked at the SAAMI specs for the 41Mag & I just looked at them for the 44Mag. As I read it, the chamber specs are "all dia. +.004" (not +/-), per the footnote under Chamber, from the .4325" chamber spec. (The groove dia. spec is .4290") These must be a carry-over from the "old days", just like the loose ones they show for the 45 Colt.

I hope S&W does cover the shipping and does the work for free. The shipping to Bowan would only be around $6. You only have to send them the cylinder, not the revolver. So you can ship it in a small USPS flat rate box.