taurus chamber

[saint_iverson]

6" 7 shot model 66 - shot .357" bevel base 158gr swc unit with minimal accuracy, and .358" 200 gr loads, both 2400 powder. The .358" had a lot of leading... I took a set of calipers to the chambers and they came out to be between .3560-.3565 (+/- caliper tolerances ). Should I try 9mm boolits or use a .356 sizer? Is this narrow chamber common among Taurus? Also tried lighter .357" 148gr wc in it to test accuracy, again, poor.

Also, the rear sight has a lot of play, not unusual of this model though because I tried another at a different shop and it had the same amount of play. Also shooting well to the left, inconsistent at best, so im also suspecting a bent front sight.

This piece was bought new by a friend and I'm doing what I can to work up a load for him, any help would be appreciated. Although right off the bat my gut is telling me to size down the boolits and try and get the mftr to do something about the sights.

[MtGun44]

You probably mean throats, but it is really hard to get accurate measurement of throats
with a caliper, usually measures small due to small misalignment. Too big will not normally
cause problems. Try slugging the barrel to see it it has the very common bore constriction in
the barrel thread area. This often the cause of inaccuracy and leading.

Bill

[saint_iverson]

Is this something thats easily corrected? Is this squeezing the boolits down? Appears the leading runs the length of the bbl, and yes throats of the cylinder

[cbrick]

As Bill said, you canot measure the ID of a round hole with flat faced calipers.

You need to either use pin gauges or slug the throats and measure the slugs with a micrometer. Once you have an accurate measurement of the throats slug the bore for two reasons 1>To know that the groove diameter is at or just a tick SMALLER than throat diameter. 2> To see if there are any tight or loose spots in the bore.

Assuming the groove diameter/throats are a good match size the boolits to throat diameter.

If the throats are smaller than groove diameter the throats will need to be reamed by a smith. If this is the case yes, the throats will squeeze the boolit down and it will then be to small for the groove diameter.

If there is a bore constriction as say the barrel threads it can be fire lapped to remove the constriction. If there is a constriction yes, this will squeeze the boolit down and it will then be too small for the rest of the bore.

First things first, you need GOOD measurements.

Rick

[rststeve]

I am sure I will get beat down with this comment but here it goes. You can do all the tricks you want to make the gun function correctly. Although you now have a gun that has a few specific loads it will shoot well. I had a gun that did the same thing, I fire lapped it now it shoots almost any thing. Everything except under sized bullets! go figure. I size every thing in a .358 sizer. One thing I have noticed with Taurus is, cylinder timing is very poor. Good luck with your project.

[saint_iverson]

Could there be an issue with the cylinder alignment, or just the timing? You mean issues with lock up/cylinder skip?