Measuring cylinder chambers...where?

[Mus408]

Took all my .45 revolvers out mostly Rugers and set about measuring the diameters of the chambers.

I notice they all have a taper to them getting smaller as you go deeper to the throat.

Do you measure near the entry or midway?

 

[pisgah]

The measurement most people are interested in is the chamber throat. That's the smallest-diameter section of the chamber, out in front of the taper. Measuring is pretty simple. Take a soft lead bullet, ball, or fishing weight slightly too big to push through the chamber manually. Then take something like a hardwood or nylon dowel and a plastic or brass hammer and drive the bullet through the chamber from rear to front. Measure the diameter of the slug with a dial caliper, and you have your throat diameter. Do the same for every other chamber, and note the diameter of each. What you are looking for is the diameter bullet most likely to give good accuracy. Sometimes, opening up the chambers and making them consistent is needed to obtain the best performance. And sometimes, the first off-the-shelf load you try in it will be just fine.

 

[Mus408]

Well I was measuring the chambers just to see how they varied from each revolver since some of my reloads will not fit in my Alaskan since it has tighter chambers.
My old .45 Colt NV,which I sold a while back had larger chambers and I would not resize all the way down due to the Dillon sizing die bringing them down smaller than needed. They would still load fine in the NV and my Uberti revolver plus cycle in my Uberti/Winchester 1873 rifle.

Now my recent Bisley NM Blackhawk in .45 Colt is in between the Ruger NV and the Alaskan as some of my old reloads with chamber.

I started with new brass for my Alaskan and only resize down enough for the bullet length plus a bit and
keep that brass separate from the other.

I assume the slight taper at the entry of the cylinder is for easy loading.

Have already measured the throats of my revolvers.

Measuring about 1/4 inch into the chamber I got....

.481 for the Alaskan .483 for the Bisley BH and .485 for Uberti Running Iron SA revolver and Schofield.
These measurments are close but maybe not exact to Ruger measure.

 

[Chuck 100 yd]

Resize your .45 Colt brass in a .454 die. .45 colt chamers are notoriously oversized and not all .45 Colt dies will return brass to SAAMI spec. Dies made and marked for the .454 , not the genaric " will work with all " dies , are what you need to use. And run the Colt cases all the way in. Also the bullet may need to be smaller to chamber in the .454. Many load manuals call for cast bullets sized .451" to be fired in the .454
Guns as most have very tight chambers. Good luck.

 

[contender]

I use a set of pin gauges to measure mine. And as noted,, the throat is the most important area.

 

[s4s4u]

I've never had a 45 Colt case full length sized with my 45 Colt RCBS FL die and loaded with an appropriate bullet fail to chamber.

 

[NikA]

It sure sounds like the OP is "neck sizing" straight wall pistol brass. I would propose that this is pretty much useless unless the objective is to cause frustration chambering cartridges in different guns. Straight wall brass doesn't typically grow a measurable amount on firing; a more typical failure mode is cracking at the case neck, which will not be prevented by "neck sizing" only.

In summary, you should resize straight wall brass all the way down. If you feel that your die is sizing the brass smaller than necessary, you should alter it or contact the manufacturer for warranty work.

 

[Ale-8(1)]

Some current SAAMI diameters for the .45 Colt chamber . . .

Immediately adjacent to rim counterbore 0.4870" (+0.004")
0.200" deep from breech face 0.4862" (+0.004")
1.2949" deep from breech face (start of short taper to throat) 0.4800" (+0.004")
Throat (cylindrical) 0.4520" (+0.0075")

Cases are 0.480" cylindrical. (-0.006")

For the .454 Casull . . .

Immediately adjacent to rim counterbore 0.480" (+0.004")
0.200" deep from breech face 0.4797" (+0.004")
1.4070" deep from breech face (start of short taper to throat) 0.4775" (+0.004")
Throat (cylindrical) 0.4525" (+0.004")

Cases are 0.4775" cylindrical. (-0.006")

Just FYI.

Note that the classic check of throats is to slip a 0.451" jacketed bullet into the throat from the front and if it will slip thru the throat with little to no "push" it's pretty darn good. Most throat reamers are 0.4525" diameter.

 

[Jimbo357mag]

Take a fired case and a sized case and see how the fit in each chamber of the cylinders for a comparison.

 

[Mus408]

My Alaskan and Bisley Blackhawk will take same as fired case sizes which is .482 and nothing larger.
The two Uberti revolvers expand the brass to .483-.484.

So since I neck size only,due to my Dillon sizing die needlessly bringing them down to .470..I will keep the fired brass separate.