sizing cylinder throats

[castmiester]

Don't know where I should have posted this but, I figured this is a good a place if any.

Thoughts on the best or correct way of slugging or measuring all cylinder throats. I found this thread post here through google, and wish I had had better results searching here but I rarely do. So I think this guy has some good advice but maybe you all could chime in, thanks.

https://castboolits.gunloads.com/sho...=1#post5146641

[gc45]

For many years I have used fishing egg sinkers pushed thru each cylinder hole with accurate results. Pin gauges are also helpful in finding differences one hole to the next.

[littlejack]

You can slug each chamber (revolver) and measure the results. In a perfect world, they would all measure the same. But, that's probably not going to be your results. So, if all you want is to not have trouble chambering all the rounds, just size the boolits to a friction fit to the smallest throat dimension. If you want it done correctly and professionally, get hold of DougGuy here on the forum, and let him know what you have. Many of the members here (myself included) have had him hone their cylinder throats. He does great work at an affordable price, and fast turn around. If you decide to just size the boolits to
the tightest throat, only expect mediocre accuracy with the revolver.

[rkrcpa]

Pin gauges are the best, easiest way to get good information.

[mehavey]

Although... a "custom" pin gauge (called a properly-sized bullet)
should suffice to judge whether it can be pushed through the
cylinders-in-question with just a modicum of "feel."

Post-Scriptum:
https://www.brownells.com/tools-clea...ating-reamers/

[HamGunner]

When in doubt, ream it out. Your group sizes will decrease. The tendency to lead the bore will decrease as well, if one or more throats were small and causing the bullet to be sized down before entering the forcing cone.

Cylinders are reamed out usually with gang reamers, so you have different reamers for the different cylinder holes. If one of the reamers gets dull, they sharpen it a bit and so between wear and sharpening, they eventually get smaller, but not necessarily the same degree for each reamer. Thus we end up with multiple size cylinder throats from the factory.

I have used 4 D rentals for throat reamers and done it myself. Nothing to it.

https://4drentals.com/products/reame...nder-throater/

[Dusty Bannister]

So, if all you want is to not have trouble chambering all the rounds, just size the boolits to a friction fit to the smallest throat dimension.
If you decide to just size the boolits to the tightest throat, only expect mediocre accuracy with the revolver.

A little clarification may be in order. It is not a drastic problem to use a bullet that is larger than the cylinder throat, the throat will reduce the bullet diameter to match the throat when fired. If you size the bullet to lightly pass through the smallest cylinder throat, it will be loose in all the other throats and lead will be gas cut from the sides of the bullet as it passes through the cylinder throat, and transitions into the forcing cone and inaccuracy and leading will occur.

[reddog81]

I would say best and correct way to measure the throats are pin gauges. If the throats are consistent and you can push sizes bullets through with a bit for pressure you will probably be fine and don’t really need specific measurements.

[castmiester]

Ok so my casts vary.. Someone mentioned elsewhere in another one of my threads about grip on the mold handles, and believe that's why the sizes are vary.... .358 to .361. Couple of days ago I laid sized bullets in the mold after taking it apart to inspect and clean it. The mold wouldn't close all the way and had a considerable gap. I was also told about over sized bullets .001 to .002. I just ran a sized .360 bullet that a friend honed my Lee sizer to .359 with, and it would not pass through with a light push, yep spring back. I asked for .359 and probably is but have spring back, forgot about the extra thou, shoulda asked for .360. Concerned about even with Cowboy dies with an oversized bullet would bulge the case and not chamber.

Calipers measured .361 on the throats, which trying to pass through a .360 bullet shows that calipers don't measure correctly. A .357 jacketed bullet falls through all buy one, that very light pressure is needed. A sized cowboy case is .373 OD and a seated bullet is .375. Typical .002 neck tension. Chambers freely. Does the Expander work in conjunction with the FL CB die ?

The cowboy dies....how far can a bullet be over sized before the sizer die doesn't under size the case and cause a bulged case that won't chamber ?

[littlejack]

So if a person sizes the boolits to fit the largest chamber, said person will have difficulty chambering the rounds in the smaller throats, if said person is using boolits with the first driving band larger than the smaller
throats.

[castmiester]

So if a person sizes the boolits to fit the largest chamber, said person will have difficulty chambering the rounds in the smaller throats, if said person is using boolits with the first driving band larger than the smaller
throats.

Then that said person will have pressure spikes in the tighter chambers, l believe.

[bcraig]

You can size the cylinder throats to the size of bullets that you want to shoot after slugging the barrel.

What you really need to check for is the the throat where the Barrel is screwed into the frame.
On most Revolvers and especially the Ruger single action pistol's there is a constriction where the barrel is screwed onto the frame.
That play's havoc with accuracy as the constricted area will size down the bullet then you have a bullet that is undersized for the bore of the barrel.

A good way to get rid of the constriction or tight spot in that area without removing the barrel is to fire lap the barrel.

You can read up on firelapping a barrel on the web,Basically Taking a lead bullet and rolling the bullet on a hard flat piece of metal or glass and inbedding the bullet with lapping compound then loading the round with a tiny amount of a fast burning powder so that it just barely exits the barrel until the constriction is gone ,once it is gone your accuracy will be better as the bullet is not being constricted anymore.
Start with a load that will not exit the barrel and then drive the bullet out of the barrel then use a tad more powder until the bullet just barely exits the barrel.
Check after each shot to keep from firing a second bullet in a obstructed barrel.

As far as the cylinder throats Veral Smith recomended to use a piece of cold rolled steel with a small slit cut into the center end of the cold rolled steel then place a piece of fine emery paper into the slit and wrap the emery paper around the cold rolled steel until a it is a snug fit in a throat then with the cylinder locked in a vice to prevent movement use a drill with the piece of cold rolled steel chucked in it place it in the cylinder and going slowly from the end of the cylinder(the end where you load the rounds in)push it in until you reach the cylinder throat that you want the Bullet of the diameter that you want to shoot. and start drilling ,making sure that the end of the cold rolled steel with the emery paper is centered and not cutting at an angle.
For example to determine if you can with just a little pressure push the lead bullet that you are wanting to shoot through a particular cylinder throat then dont ream that particular cylinder throat.
Do Ream the cylinder throats that the Bullet will not push through until they will.

Then proceded with the firelapping of the barrel.
After the firelapping of the barrel make sure to clean the Lapping compound from the cylinder and the barrel.
Once finished you will have a gun that the cylinder throats are uniform and matches the bullets
that you are wanting to shoot and the barrel throat matches the Bullet and the bullet matches the barrel bore .

[stubshaft]

^^^^^^^^^^
What he said!

I have seen a good number of pistols with constricted barrels. Slugging a bore with one just gives you the diameter of the constricted portion and not the actual barrel diameter.

[Dusty Bannister]

So if a person sizes the boolits to fit the largest chamber, said person will have difficulty chambering the rounds in the smaller throats, if said person is using boolits with the first driving band larger than the smaller
throats.

Please keep in mind that the chamber of the revolver is where the loaded cartridge lays in the cylinder. Then there is a transition taper to the smaller cylinder throat. It is entirely reasonable to use the largest bullet diameter that will easily chamber and be removed without a sticking bullet.

The point of bullet fit is in the throat regardless of the chamber size. Undersized bullets will likely lead the bore if the groove diameter of the barrel exceeds the diameter of the throat.

[DougGuy]

As far as the cylinder throats Veral Smith recomended to use a piece of cold rolled steel with a small slit cut into the center end of the cold rolled steel then place a piece of fine emery paper into the slit and wrap the emery paper around the cold rolled steel

DO NOT do this. This is the FASTEST way I know to ruin cylinder throats. I don't give a dang WHAT Veral says it it a NEANDERTHAL way of enlarging throats. There is NO WAY of achieving concentricity as you work, there is no pilot or guide to ensure the tool is parallel with the chamber, you have nothing accurate to go on, and your results MAY shoot a good group if you are lucky.

I have used 4 D rentals for throat reamers and done it myself. Nothing to it.

Nothing to it haha. What are you going to do when half the throats ream successfully, and the throats on the other side of the same cyilnder bog the reamer down until it is SQUAWKING when turned and you think you are going to break the shank off the reamer. Anyone who has reamed enough Ruger cylinders will undoubtedly have ran into this issue and know exactly what I am talking about.

Ruger cylinders are notorious for uneven heat treating of the billet steel rods from the steel mill, temper varies WIDELY from cylinder to cylinder and even from one side to the other side of the same cylinder.

In this scenario, the harder temper throats will finish considerably smaller in diameter than the throats on the softer side of the cylinder. The reamer itself is HSS and WILL CRUSH when forced through the harder throats and cut a smaller hole.

For THIS REASON I got away from reaming cylinders and adopted the Sunnen hone exclusively for ALL cylinder throat resizing. Not only is the finish superbly done, the stepless adjustment afforded by the hone allows for honing all the throats to consistency regardless of the temper of the metal or any changes in temper from throat to throat, allowing the user to achieve a consistent light drag fit on the pin gage, something that CANNOT be done with a reamer alone due to the variations in temper of the metal itself.

[mehavey]

The REST of the story. . .https://castboolits.gunloads.com/sho...=1#post4440004

( ... tho' I admit, I am a reamer Philistine by historical default )

[Loudenboomer]

My 2 cents would be to borrow or rent some pin gages. Throats are probably small and multi sized. Doug corrected a 44Spl. Black Hawk and a 480 SBH for me. Happy customer.

All that's left is load development and practice. Rince and repeat. Rince and repeat
Merry Christmas

[castmiester]

Merry CHRISTmas.. to all you casters.... I hope and Pray you receive Him in your heart today.

Just now I measured my sized bullet from a few years ago. they measure .359. Yes I see spring back, just like after casting.

They don't fall through the throats, nor easily pushed through. But I would like to use them to see what the throats are. It wouldn't take much to get them through to see what they actually are. Once I do that Doug, I'd be interested in sending you the cylinder to hone. It's off my Taurus 66 .357 mag.

I just ran .359 casts through the throats. All but two, were pushed through were pushed a little hard, no hammer. The rest easily through, with a very little persuasion. They measured .359. Again the .357 jacketed fell through but the casts varied going through. I'm thinking 5 out the 7 throats are ..359, the other 2 are .360-.361ish, I guess.

[littlejack]

You can measure the diameter of the pushed through boolits to see how much they were sized down. You can get an approximate throat size.

[castmiester]

You can measure the diameter of the pushed through boolits to see how much they were sized down. You can get an approximate throat size.

Sorry should have posted before. All but two are .358, the other two are .359

I appreciate all the responses, especially Dougs. So I get the variable cylinder throats, and one other poster that mentioned before and in this thread about the Barrel/forcing cone needs attention. If I slugged from the muzzle and stopped at the throat, and drove the slug back through the muzzle. My question is drive to see if I have an issue at the barrel/frame it may show up slugging or it may not ?