bore diameters in revolvers

[M. De Land]

Got out my plug gauges tonight and checked my three .44 cal. revolver bores. MD
58 Rem Pietta- .440
60 Colt Pietta- .436
ROA - .4425

 

[TFoley]

Got out my plug gauges tonight and checked my three .44 cal. revolver bores. MD
58 Rem Pietta- .440
60 Colt Pietta- .436
ROA - .4425

Interesting, but BP arms tend to measured to the grooves, and not the lands - that's why most .44cal BP revolvers take a ball around .451" or, in the case of the ROA, .457".

Single-shot target pistols, on the other paw, are usually patched ball shooters, so THEY will shoot a ball more in keeping with the alleged calibre.

tac
[.451" Walker and .457" ROA]

 

[Da_swed]

my r&s revolver shoots a 457 rb

 

[phoenix511]

The issue of CB revolver chamber diameter, bore diameter, and groove diameter has been punted around for some time.

In my mind, for best accuracy, the issue is the relationship of the chamber diameter to the barrel's groove diameter. If the ball, as forced into the chamber, is less than the groove diameter, it likely would not properly engage the rifling in the barrel. Chamber diameters are fairly easy to measure, groove diameters, especially with an odd number, require special equipment.

One can make a guess at the groove diameter with an expanding plug gage with small enough fingers to just fit the grooves. Most of my replica CB revolvers have groove diameters same/slightly smaller than the chamber. They shoot good enough for me, but skilled marksmen may want better results.

Don't know if soft lead ball obturates enough to fully engage rifling, or if it even matters.

 

[Dickydalton]

Measure the grooves on a recovered ball. That will help tell the true size. Shoot into sand at a long enough range that the ball doesn't expand.
You're going to have an almost flat part of the ball caused by the cylinder shaving the ring of lead off that can vary due to cylinder chamber v/s ball diameter. Measure the rifling grooves on the forward end of the ball and the rear on the same rifling groove. If the front is narrower than the rear it may be because the rifling isn't gripping enough or because the powder charge is too large. I used to see marks on hard cast Keith style bullets loaded hot in my 44 Mags that were narrow on the front bearing ring and wider progressively on the last two.

 

[M. De Land]

Just put the barrel in the padded vice after cylinder removal and drive a bullet through from the muzzle. Use a steel rod and tape it to bore diameter so it cant hurt your crown or lands, lube up the bore and drive it through.
Shot balls or bullets are not very reliable as they can expand from impact some even it snow capture. MD

 

[nkbj]

The issue of CB revolver chamber diameter, bore diameter, and groove diameter has been punted around for some time.

In my mind, for best accuracy, the issue is the relationship of the chamber diameter to the barrel's groove diameter. If the ball, as forced into the chamber, is less than the groove diameter, it likely would not properly engage the rifling in the barrel. Chamber diameters are fairly easy to measure, groove diameters, especially with an odd number, require special equipment.

One can make a guess at the groove diameter with an expanding plug gage with small enough fingers to just fit the grooves. Most of my replica CB revolvers have groove diameters same/slightly smaller than the chamber. They shoot good enough for me, but skilled marksmen may want better results.

Don't know if soft lead ball obturates enough to fully engage rifling, or if it even matters.

Colt and Remington pattern Piettas seem to go with chamber diameters that are in between the barrel bore and groove diameters.
Putting the eye ball on recovered balls and conicals makes it obvious that upset of the lead does not take up all the slop in the grooves unless you have enough powder behind a hollow base and that's real tough to do unless you're shooting a .44.
Question for the aficionados: Was this the common practice in days of old to allow for fouling build up?

My other question is when is the airline going to bring my lost luggage but I'd need a forked branch, a pendulum and a Ouija board to figure that out.

 

[t.l.a.r. eng]

If the chamber diameter was left small for fouling reasons, the gun still won't shoot straight if the ball isn't firmly in the rifling.

Case in point, my 51 Navy .36 wouldn't hit anything reliably while working up the load for it. Going from 15 grains to 35 grains in 2 gr incriments showed fouling became heavier after the true load the gun wanted [20gr] was reached.

Accuracy never improved with or without the fouling. Once the chambers were opened to groove size + .002 the pistol was remarkably improved. Even going past 20 grains the optimal load, increased fouling did little to hurt accuracy.

It just made things dirtier and harder to work with.

Just observations made with my litty Navy.