Regarding cylinder throat size..

[long_arm]

The revolver is an S&W 29-2.

The goal is to obtain cast bullets which are sized correctly (ie that which yields greatest accuracy) for this gun.

In lieu of a perhaps more appropriate measuring device I am wondering if I can measure the cylinder throats precisely enough via a measured slug, in this case an XTP measuring .430", to achieve the stated goal.
The slug freely slides through all cylinder charge holes without requiring any assistance, such as being pushed through with a dowel, etc. At the forward end of the cylinder, nearest the forcing cone, there appears very little play at all between the slug and the cylinder walls.

So... Size to .430" or .431"?

https://i.postimg.cc/QVZdzbHY/PXL-20220203-035557711.jpg (https://postimg.cc/xNgQJLGL)

https://i.postimg.cc/k4DFcx6t/PXL-20220203-035650638.jpg (https://postimg.cc/mzfHZ1Sb)

https://i.postimg.cc/FsxdYY1t/PXL-20220203-041921735.jpg (https://postimg.cc/7ffYcYgX)

P. S. Yep, gun is dirty.. had fun at the range today

[Jtarm]

You need over sized soft lead slugs, larger than the throats,
.

Tap them through so they get swaged down to actual throat diameter, then measure.

LBT sells tapered slugs for that exact purpose.

[jrayborn]

All you have really determined is that the throats are at least .430. You are probably correct that sizing to .431 would be proper but you are still kind of guessing. Buy some pin gages. If you buy six, starting at .430 through .436 then you will be able to determine "exactly" what size the throats are. After you clean them...

:)

Seriously, investing in a few pin gages is a good idea.

[JRLesan]

Do a search; reams have been written on sizing under, at and over throat size both here and elsewhere...

[ABJ]

All you have really determined is that the throats are at least .430. You are probably correct that sizing to .431 would be proper but you are still kind of guessing. Buy some pin gages. If you buy six, starting at .430 through .436 then you will be able to determine "exactly" what size the throats are. After you clean them...

:)

Seriously, investing in a few pin gages is a good idea.

This is the best way. Having said that if you size at .431 and have .432 throats a mid range load will bump up enough not to lead depending how hard or soft the alloy is. A powder puff load will allow gas cutting and may cause leading. I shoot a lot of cowboy loads (750ish) so I size to the full size of the throat and it doesn't bother me to be a half thou. larger. If my cylinders will take a .431 pin and no go on a .432 then I size to .432.
Tony

[DougGuy]

Size to fit the throats. It makes no sense at all to size larger than the throat because once pressure forces the boolit through the throat, it will exit the front of the cylinder at throat diameter. You can't push a .431" boolit through a .430" hole and then hope it will still measure .431"

Using soft enough alloy, and/or stout enough powder charges you can expect the boolit to obturate until it is confined by the throats, and once in the bore it will obturate into the rifling, whatever that diameter may be, and form a good seal.

For the record, for every 100 44 caliber cylinders I hone, maybe one will request I hone it to .4305" for .430" boolits, the other 99 will get honed to .4315" for .431" boolits, this works VERY well for any 44 caliber centerfire revolver.

If you are wanting pin gages, consider half thou increments and get the pins in between the thousandths. .001" increments are too coarse for cylinder reading.

Also, the pin gage measures in a 360 degree direction, besides air gaging it is the only form of gaging a hole that does this. Every other measuring tool measures point to point across the diameter, the cylindrical pin measures -exactly- as the boolit will see the hole, all the way around the circumference.

[243winxb]

.430" Barrel groove diameter will be smaller, if like my 29-2. Harder is better. https://www.thehighroad.org/index.php?media/casting-bullets-for-over-50-years.3532/full

[gunther]

Also, look at "Small hole gauges". A set will be about $20 for imported. Three times that for domestic. Both work. Avoid bevel base bullets. If you have shooting buddies who shoot muzzle loaders, an over sized soft round ball driven through the throat (With the cylinder off the gun and well supported) can be measured and will give you believable numbers. Inside measurements with dial calipers can be problematic on hole diameters.

[long_arm]

Thanks for your responses.

Sounds like pin gauges are the way to go.

Where do you buy individual gauges?

[murf205]

long arm, I bought my pin guages from Meyer Gage Co in Windsor, Ct., 1-800 243 7087, at least that is the # on their catalogue. Get them to send you a catalogue, it's full of information. They sell individual pins and have a $20 minimum order, so no big deal. Great people to deal with and for a 44 I would start with a .428 and go up to .434. That should get you a pretty good idea of most 44 revolvers. The ones I have are in 1 thousands increments and they have served me well. The pins were listed at about $5.57 per pin but they could have had a price increase(who hasn't)! Valuable tools for us wheel gun junkies.

[long_arm]

Roger that and thanks, murf!

[PoppaJoe]

Hello, Doug
I am new to this site, and have been following your discussions on Ruger cylinder throats. I have a Blackhawk, .45 Colt, that has throats ranging from .450 to .451, and would like to get them reamed/honed to .4525. Do you offer this service, and if so, how do we proceed?
Joey

[DougGuy]

Hello, Doug
I am new to this site, and have been following your discussions on Ruger cylinder throats. I have a Blackhawk, .45 Colt, that has throats ranging from .450 to .451, and would like to get them reamed/honed to .4525. Do you offer this service, and if so, how do we proceed?
Joey

Use the message function on this site. Click in my signature where it says "Click here to send me a PM" OR, Left click my username and a menu will drop down, click on Private Message and it's like email.

[TurnipEaterDown]

PappaJoe: In a different post I saw Doug say to drop him an IM and converse that way.
Look at the menu bar, just under "Chat".
I never worked with him (yet), but may get to that...

[Froogal]

The jaws on the top of your calipers are intended for measuring inside diameters.

[long_arm]

Froogal,
I gave that a go. Didn't strike me as a very accurate method. Cylinder holes measured this way gave me .429" but they are clearly larger than that as a measured .430" jacketed slug will slide right through.

[murf205]

Froogal,
I gave that a go. Didn't strike me as a very accurate method. Cylinder holes measured this way gave me .429" but they are clearly larger than that as a measured .430" jacketed slug will slide right through.

long arm, get a micrometer. They don't cost a ton and then get a mic stand. I am fumble fingered and this is the best $20 I spent on Amazon in a looooong time. Make taking measurements a lot more precise.295755

[long_arm]

Murf,
Better than my Mitutoyo?

[DougGuy]

Murf,
Better than my Mitutoyo?

He's probably talking about using the stand to hold the mic. I have the same setup.

295756

[murf205]

Well, not better or worse, but the mic and stand make a lot steadier platform.

[Froogal]

Froogal,
I gave that a go. Didn't strike me as a very accurate method. Cylinder holes measured this way gave me .429" but they are clearly larger than that as a measured .430" jacketed slug will slide right through.

Takes a bit of experience. Gotta hold the calipers just right, and hold your tongue just right. I have a wee bit of experience as a machinist/tool maker.

[kenton]

Also, yes micrometers are more accurate and consistent than calipers.

The common way to hold a micrometer is to hook your pinky through the frame and hold it to your palm. Then use your thumb and fore finger to turn the barrel to take your measurement.

[long_arm]

Takes a bit of experience. Gotta hold the calipers just right, and hold your tongue just right. I have a wee bit of experience as a machinist/tool maker.

Glad it works for you, Froogal. I just tried it again a moment ago and again found results to be variable and still not a single .430" measurement. It's pins for me.


Kenton,
Thanks, adding a piece of gear today.

[NuJudge]

I bought a pin set to measure my 29-2 and 25-2. The 29-2 would pass a .428" pin, but not a .429" pin on all the throats. The 25-2 appeared to be .453" with a vernier caliper, but would pass a .455" on all the throats, and a .456" on three of them.

Get a set of pins to find out what they really are.

[DougGuy]

I bought a pin set to measure my 29-2 and 25-2. The 29-2 would pass a .428" pin, but not a .429" pin on all the throats. The 25-2 appeared to be .453" with a vernier caliper, but would pass a .455" on all the throats, and a .456" on three of them.

Get a set of pins to find out what they really are.

Get pins in .0005" increments .001" is too coarse to measure cylinders.

[alamogunr]

I bought a set of pin gauges on Ebay. A few pins were missing which degraded the price significantly. The pins that were missing were not in the range of any that I wanted for gauging cylinder throats. Best to get a minus(-) set. Be aware that shipping can be significant because of weight.

I got the set rather than individual gauges in order to get the case they came in because it is easy to see if a gauge is missing you have a place to return a gauge after using. For me that is important since I tend to lay things down after using them. Amazing how often I forget where I laid them.

Pin gauges come in handy for a lot of things. It is significant how much variation there is between Ruger(example only) cylinders and Freedom Arms cylinders.

[243winxb]

The test- https://www.thehighroad.org/index.php?media/44-magnum-soft-alloy.3118/full VS https://www.thehighroad.org/index.php?media/44-magnum-hard-alloy-25-yards.3117/full

[sniper]

Before I knew much of anything, I borrowed an inside measuring caliper from a co-worker, miked the throat diameters of my revolver, and after each one, measured the diameter with my Micrometer. They all measured .357, so I ordered a .357 Lee push-through sizing die, and shot hundreds of boolits sized that way.
No leading, but it may have been thanks to the "almost" Lyman #2 alloy I mixed on my Coleman camp stove, and the pan lubing/cake cutter kit I bought. Some sort of red icky-sticky goo lube, but ZERO leading! I guess I got lucky. 8-) But...those were good days!

[murf205]

Before I knew much of anything, I borrowed an inside measuring caliper from a co-worker, miked the throat diameters of my revolver, and after each one, measured the diameter with my Micrometer. They all measured .357, so I ordered a .357 Lee push-through sizing die, and shot hundreds of boolits sized that way.
No leading, but it may have been thanks to the "almost" Lyman #2 alloy I mixed on my Coleman camp stove, and the pan lubing/cake cutter kit I bought. Some sort of red icky-sticky goo lube, but ZERO leading! I guess I got lucky. 8-) But...those were good days!

sniper, you are exactly right. I have a .357 with .357 barrel and .357 cylinder throats and I size to .357 for that gun (might as well). No lead and good accuracy but we never know until we shoot first and check for lead/accuracy. It took a long time for me to learn, but always let the gun tell you what it wants.

[Cosmic_Charlie]

I would try some medium loads at .431" . My 24-3 has .432" throats but shoots .431" boolits just fine. Never had very good luck with boolits larger than the throats. If you can't push them through with a finger they are too big.

[JimB..]

I’d clean the cylinder before taking measurements. Could easily have a thou of crud

[Hickok]

Just my experience with the older M-29's, they seem to be a bit large in cylinder/chamber throats. I am thinking about .432"-.433".