Chamber size difference between my 2 flattops.

[Joe S.]

I slugged the chambers in my two 357 Blackhawks tonight. It was a purely scientific experiment. :)

I used unsized cast bullets at approximately .362 diameter driven in at the muzzle end with a brass hammer and then punched out with a brass punch and measured on the front driving band of the bullet.

here are the results.

Om flattop, circa 1958
.358
.3595
.360
.3585
.3595
.358

Nm anniversary flattop
.358
.358
.358
.358
.359
.359

Now. What should this mean???

 

[Rainy Day Shooter]

It should mean the NM would produce more accurate and consistent performance. Is this the case, or are you finding the chamber size difference is, on paper, not noticeable between the two?

 

[Joe S.]

The anniversary is very accurate.
However the OM seems to be as well, altho i havent put it to the test like i have the anniversary. My shooting was cut short the other day when i broke the ejector rod. Hoping to get that fixed today if the part arrives.

 

[Chuck 100 yd]

There is a lot of variables going on when slugging and measuring those slugs, The use of pin gauges is the most accurate way to measure chamber throats. Slug the bore and use pin gauges on the throats.
That said, your measurements are not all that bad. Shoot and have fun!

 

[Joe S.]

I need to invest in some pin gauges. That is just one thing i havent had a serious need for...

 

[Srb08]

I need to invest in some pin gauges. That is just one thing i havent had a serious need for...

I thought the same thing, before I bought a set.
I check guns now, before I buy them.

 

[gramps]

Just get a set of bullets starting at .356, .357, 358, .359, .360. Then drop them into your cylinder. When one stops then that size is the one to shoot for that cylinder. I find it a lot cheaper and easier than pin gauges. Granted it is rough, but accurate enough IMO.
gramps