Manson Revolver Cylinder Throat Reamer

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pintler said:
then two bits of shim stock are used with the micrometer

I'm not tracking on the shim stock part, can you elaborate?
Click to expand...

Shim stock, slug, shim stock - like a s'more.

The shim stock serves to prevent the micrometer from pushing a flat into the soft lead slug, inducing a measurement method error.
 
mixed nuts,

so, what is your barrel groove diameter and your cylinder throat diameter?

murf
 
The shim stock serves to prevent the micrometer from pushing a flat into the soft lead slug, inducing a measurement method error.
Click to expand...

1)If you're torquing the micrometer enough to appreciably deform the slug, you're torquing it enough to deflect the micrometer frame. You want contact, not force.

And we're only talking about measuring to at best .0001 here. If you're trying to measure to millionths then a lot of factors like temperature start to matter.

2)Even if force mattered, putting flat shim stock between a flat anvil and a concave slug doesn't spread the force on the slug any; it's still a line contact.

3)Shim stock isn't all that accurate, thickness wise. For example, this company specs +- .001 on .020 shim stock. Sure, you can mike the shim stock and say that your piece is .0209, but every time you measure you're adding one more little error, and they all stack up.

https://precisionbrand.com/wp-content/uploads/2015/05/Steel-Shim1.jpg
 
Guess I've been doing it wrong for over 20yrs in servicing revolvers... o_O

Standard training for gunsmiths has always been to use dead soft lead and shim the slug to prevent deformation of the rifling impressions on the bullet. You're correct, if you have a round cylinder, you have as much contact on the anvil as you do as the shim, but wrapping the rifling impressions around the slug complicates things. I can lay more of the bullet against a wider "flat" with the shims than I can on the micrometer itself. So my way gets a true outer dia, your way gets some surface between the lands and grooves. Thanks, but I'll keep doing it my way.
 
you mean along the axis of the slug, right? like putting lumber under trailer legs so they won't sink into the mud?

murf
 
I dunno what's customary for gunsmiths, but that's not how you'd measure accurately in a machine shop.

If you have an even number of grooves you can directly measure a diameter. If you have an odd number, you want a V block or V anvil micrometer. Bridging the gap across two raised parts (where the slug filled the groove in the barrel) is measuring off a chord.

Post #2 here: https://www.shootersforum.com/handloading-procedures-practices/98058-measuring-slugs.html
is talking about wrapping a single piece of shim. That avoids the chord problem, but there is sure a lot that could go wrong there, metrology wise.

I'm not trying to rag on you; it's just that doing that in a machine shop is going to raise some eyebrows. If you're happy with the results, good enough!
 
Info 0nly!!!
Opening throats voids RUGER warranty- BTDT

Use cerrosafe and mic to measure throats- much cheaper than hordes of pin gauges-BTDT
 
Redneck method:

Slug the bore. See if the slug drops through the chamber throat. If it does, the chamber throat is larger than the bore and the throat will not need reaming.

If the barrel slug is larger than the chamber throat then of course you will need to measure the slug to determine which reamer to use. But you can answer the big question without using caliper or micrometer at all.
 
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I got a set of pin gages on sale a few years ago. I also eventually got a good electronic, internal mic. I have used them to measure all my revolvers. The only ones that were consistently tight were Ruger .45 Colt NMBH’s. They tended to around 0.450”, but varied significantly among chambers, and among the several guns. My .357’s were 0.3571” on my S&W 627PC, to 0.3590” on 50th Anniversary Ruger Blackhawk. My most accurate .357 may be my 45 yr. old S&W Model 27-2 at 0.3586”. Most of my .44’s tend to be slightly on the big side, except my DW 744, which was ridiculously tight at 0.428”. I got the Manson reamers from Brownell’s for .44 and .45 Colt. The DW is now 0.4318” and is the most accurate .44 I have. My other .44’s run from 0.4324” to 0.4327” and they are also nicely accurate. My reamed .45 NMBH tend to around 0.4528”. They now shoot much better than they did originally. Part of the reason for this is, that in addition to being tight, the throats tended to “colorful” shapes, like oval, or S shaped, or tapered. Fortunately there was enough material that after reaming they were as cylindrical as I could get them and they shot much better.

The bottom line is, measure carefully before you spend money on a reamer. IME, the .357’s tend to be a bit oversized, rather than undersized. And what is also critical in a revolver is chamber alignment with the barrel. I look at the distribution of fouling in the forcing cone to see if the chambers are aligned. If they aren’t, then ministrations of a competent gunsmith are required.
 
MixedNutz:

The Manson reamer works great. Yes, a .358 diameter cylinder throat will usually shoot hard lead bullets great in a .357" diameter bore assuming there are no constrictions. It is not unusual to find a "thread-choke" in the bore where the barrel screws into the frame. BEFORE you ream the cylinder be sure your bore slug is measuring the true groove diameter of your barrel not the constriction where the threads are.
 
I use inside pin gauges. They are less than $4.00 a piece currently. I just built my own set in .0005 increments. Mine start at the smallest reamer pilot (.3545) and go up past the largest pilot (.357 - 'cause I'm curious) to .360 in .0005 increments. They are simple to use for the non-machinist / gunsmith (me).

Of course this is only good for .38/.357's. But that's the only revolver caliber I've owned multiple guns in. I have other calibers, but for the cost I just send them out if needed.
 
murf said:
you mean along the axis of the slug, right? like putting lumber under trailer legs so they won't sink into the mud?

murf
Click to expand...

To make life easier, I cut the shim stock pretty long, then as wide as the length of the bullet. That lets me hold the shims in place a little easier than trying to live with smaller stock. I mark the shims where I want my mike to contact, mike that location, then insert the bullet. Subtract the shim thickness, bango, that's the unadulterated dia, within the necessary margin for error. ETA: I do roll the bullet and take a few measurements, as it's not uncommon to have bores be slightly out of round.

Wrapping the shims is for the birds, way too much induced error. The method I was taught and have used all of these years really no different than measuring between parallels, which the last time I was managing a machine shop, wasn't so uncommon of practice, and not so dissimilar to using a V-block. At the end of the day, we don't have to be accurate to the 1/10th or 1/100th thou, we're talking about steel bores and malleable copper, gilding, or lead bullets. It's really not rocket science (and having done work in the space, rocket science isn't so complicated in itself), we want the bore to be the smallest diameter the bullet sees, cascading down from throat to forcing cone to bore, and we want to be sure the bore is as regular as possible, free of thread crush constrictions, or imbalanced friction points such as the caliber stampings on the barrel, or the front sight screw hole... Achieve those things and most likely, the gun will shoot. Have too much of that out of whack, and the dog won't hunt... If we were shooting steel bullets, life would be different, and we'd have to live in a very different world. Since we're not shooting steel slugs, we have the luxury of a few 10 thousandths margin without consequence.
 
Mixed Nuts said:
Thanks, gentlemen, I appreciate all the advice.

I've thought of one last question. If the cylinder throats are cut to be .358 and the barrel slugs at .357. Then can i expect to shoot .358 BNH 18 hard cast bullets at low power without leading? Or have I just improved my chances of success? Is it always a trial and error game?
Click to expand...
I would say you will not have solved the problem without softer bullets. I did all that and only changing to 38 Special bullets cured my 357 Magnum leading. On the throats issue, I would not be aiming for .358 but the more common .3575. To follow the rule of thumb, bullet is larger than the throat, is larger than the bore would yield the sequence .358-.3575-.357, assuming the bore slugs at spec. All I did to know which cylinders to ream throats on was to see if I could lightly tap a nominal diameter, lead bullet through, e.g. a .358 through a .357 Mag or 38 Special. I learned to pretty much know that Smiths were not setup to shoot lead until modified and that newer ones generally had the wrong type of rifling. On the Rugers I had my heartaches with the older SIX series with mildly cut rifling but not much on newer guns, zero problems on 327 Fed Mag.
 
murf said:
mixed nuts,

so, what is your barrel groove diameter and your cylinder throat diameter?

murf
Click to expand...

Well, Murf, I haven't done it yet. I've got the right size lead fishing weights. And I've got a .358 and .356 pin gauge. I've got three more gauges on order, a .354 .355 and .357. The stuff was ordered about a month ago and was shipped from Amazon - where you can buy individual pin gauges for cheap - and shipped via UPS Sure Post, which is a service whereby UPS delivers your package to a nearby post office. In my case a PO Box.

Shipment has just up and disappeared. I got online with amazon and told Jayson - whose real name is almost certainly Ashoka Manaktala or some such - my story and he said he'd resend everything. I said thanks and told him it might be difficult to find all three pin gauges in stock but he said "no problem." So now I'm waiting again.

I could probably attempt part the procedure with what I've got. And I probably will soon. Just have cheapo calipers wanted all the stuff on hand in case I ran into an unexpected problem. But should at least slug.

I will slug tomorrow.
 
RealGun said:
I would say you will not have solved the problem without softer bullets. I did all that and only changing to 38 Special bullets cured my 357 Magnum leading. On the throats issue, I would not be aiming for .358 but the more common .3575. To follow the rule of thumb, bullet is larger than the throat, is larger than the bore would yield the sequence .358-.3575-.357, assuming the bore slugs at spec. All I did to know which cylinders to ream throats on was to see if I could lightly tap a nominal diameter, lead bullet through, e.g. a .358 through a .357 Mag or 38 Special. I learned to pretty much know that Smiths were not setup to shoot lead until modified and that newer ones generally had the wrong type of rifling. On the Rugers I had my heartaches with the older SIX series with mildly cut rifling but not much on newer guns, zero problems on 327 Fed Mag.
Click to expand...

Interesting. I cannot tap a factory labeled .357 bullet through any of my cylinders. And I don't have a .3575 gauge coming. Maybe I could use a method suggested here... where I just slug the cylinders and measure. I could probably check my cheap calipers against my .358 pin gauge.
 
Curator said:
MixedNutz:

The Manson reamer works great. Yes, a .358 diameter cylinder throat will usually shoot hard lead bullets great in a .357" diameter bore assuming there are no constrictions. It is not unusual to find a "thread-choke" in the bore where the barrel screws into the frame. BEFORE you ream the cylinder be sure your bore slug is measuring the true groove diameter of your barrel not the constriction where the threads are.
Click to expand...

Thanks Curator. Nice avatar :)
 
ClemY said:
I got a set of pin gages on sale a few years ago. I also eventually got a good electronic, internal mic. I have used them to measure all my revolvers. The only ones that were consistently tight were Ruger .45 Colt NMBH’s. They tended to around 0.450”, but varied significantly among chambers, and among the several guns. My .357’s were 0.3571” on my S&W 627PC, to 0.3590” on 50th Anniversary Ruger Blackhawk. My most accurate .357 may be my 45 yr. old S&W Model 27-2 at 0.3586”. Most of my .44’s tend to be slightly on the big side, except my DW 744, which was ridiculously tight at 0.428”. I got the Manson reamers from Brownell’s for .44 and .45 Colt. The DW is now 0.4318” and is the most accurate .44 I have. My other .44’s run from 0.4324” to 0.4327” and they are also nicely accurate. My reamed .45 NMBH tend to around 0.4528”. They now shoot much better than they did originally. Part of the reason for this is, that in addition to being tight, the throats tended to “colorful” shapes, like oval, or S shaped, or tapered. Fortunately there was enough material that after reaming they were as cylindrical as I could get them and they shot much better.

The bottom line is, measure carefully before you spend money on a reamer. IME, the .357’s tend to be a bit oversized, rather than undersized. And what is also critical in a revolver is chamber alignment with the barrel. I look at the distribution of fouling in the forcing cone to see if the chambers are aligned. If they aren’t, then ministrations of a competent gunsmith are required.
Click to expand...

This is an interesting post. When the hammer is locked back in single action there is some play in the cylinder. I've always sort of wondered how that all works itself out when firing. Yet the gun is accurate with factory, jacketed, 158 American eagle JSP. It was never quite as accurate with the 18 BNH hardcast bullets and I tested four powders and many power levels before low power Unique leaded everywhere.

Some of the posts hereabouts have me thinking slightly softer bullets may be better, generally speaking, for accuracy.
 
walnut1704 said:
I use inside pin gauges. They are less than $4.00 a piece currently. I just built my own set in .0005 increments. Mine start at the smallest reamer pilot (.3545) and go up past the largest pilot (.357 - 'cause I'm curious) to .360 in .0005 increments. They are simple to use for the non-machinist / gunsmith (me).

Of course this is only good for .38/.357's. But that's the only revolver caliber I've owned multiple guns in. I have other calibers, but for the cost I just send them out if needed.
Click to expand...

Yeah, this I hear. I'm going to order 10,000ths to fill out my set tonight.
 
J-Bar said:
Redneck method:

Slug the bore. See if the slug drops through the chamber throat. If it does, the chamber throat is larger than the bore and the throat will not need reaming.

If the barrel slug is larger than the chamber throat then of course you will need to measure the slug to determine which reamer to use. But you can answer the big question without using caliper or micrometer at all.
Click to expand...

Nice! I will do this as a first step.
 
walnut1704 said:
Well if they measured them they would all be perfectly equal. That would tip them off.
Click to expand...
Good one. Too many of my Rugers have replaced cylinders, a part which Ruger contracts out rather than make themselves (my understanding). Rather than repair one, I believe they just reach for a new one. I had to get my gun back and buy my own reamer for one of my 327 Fed Mags, I forget which. Not sure how they would ever be certain that a cylinder had been modified internally, voiding a warranty on the rest of the gun.
 
Mixed Nuts said:
So far, my ruger, security six leads a lot with some hard cast low power loads but not with magnum loads launching the same bullet. The prevailing opinion hereabouts was that the cylinder throats were smaller than the bore. This sized bullets smallish as they launched from the cylinder and, when the loads were low power, kept them from obturating to fit the bore when they were traveling down the barrel.
Click to expand...
If the throats were smaller than the grooves it would lead no matter what. I bet you are OK there. The first thing to try at low power is softer bullets. Likely they won't lead.

The bullets obturate to fill the throats, assuming enough pressure. Not enough pressure and they do not. If they are undersized as cast for your groove diameter they will lead. The lower pressure load is not bumping the hard bullet up and you are getting gas cutting. The higher pressure load is bumping the bullet up to seal the throats and the bore.

Try a softer bullet. if this does not lead, I was right. If it still leads, start checking groove diameter and throat diameter. That said, if the throats are smaller than .359/.358 you may want to ream them to .358 or .359. If you are going to do that though, you should really check your groove diameter first, even though .359 would likely solve any issues.

Always fit bullets to the throats, if they are under, there must be enough pressure to bump them up to seal the throats.
 
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Regarding buying a micrometer, that is the wrong tool to use to measure your chamber throats. I suspect you may be talking about a caliper, not a micrometer.
Click to expand...

Oh yes you can. You just have to have the right tools to do it it with. Here are the tools I use. Sorry I don't remember the correct name for the expanding "T" handle but as you can see I have them in several sizes. I used the smallest one for the .357. These came to me after my dad passed away. We used them in his machine shop I worked in off and on, mainly on from the time I was 10 to around 24 years of age.

The pictures show the set of T measures. The small one expanded then closed. You use these by inserting at at angle then loosen to expand. Rotate the tool and it will slip to fit the hole and hold that size. Next measure the T Expander with the micrometer. In the case the cylinders on this unfired model 28 measured between .3582 to .3584. The expander has rounded anvils so it will show the true diameter of the hole. S&W made some consistent guns didn't they? I guess that explains part of the reason for the accuracy from the older models.

MVC-001S.JPG MVC-002S.JPG MVC-003S.JPG MVC-004S.JPG MVC-005S.JPG MVC-006S.JPG MVC-007S.JPG
 
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