Pressure vs. tight cylinder throats

[leftiye]

An old Bobby Vinton song?

[Carsten]

To be on the safe side I will downsize my boolits just a hair.
I want them to be .430 after sizing.
My Lee .430 sizer leaves them 431.
I will get a lube sizer on of the days so the question is if I should get a .429 die or an RCBS .430 will actually size them to .430?

[leftiye]

About .005" smaller than chamber mouths is what "they" say is optimum size for boolits. .001" (to .002") larger than groove diameter is good for chamber mouths.

[Silver Jack Hammer]

Size your boolits to fit the throats as near as possible. The base of the boolit will expand and form a gas seal at the cylinder throat anyway if your boolits are sized less than the diameter of the cylinder throat.

If your boolits are sized to within .001 or .002 over throat diameter you will be fine. Plenty of handloaders including myself have shot boolits cast and not sized at all without any problem of overpressure.

Year ago CCI/Speer did a few tests with their new half-jacket semiwadcutter in .38 Special and found boolit size did NOT contribute significantly higher pressures. Since jacketed boolits are much harder than lead alloy it is reasonable to expect oversized cast boolits will not cause a significant pressure rise over what might be expected with boolits sized to within .001 or .002 inch over cylinder throat diameter.

Stick with boolits of one in 16 alloy or Lyman #2 with a BHN (Brinell hardness number) of about 15, one in 20 is bit soft for your load but OK with faster-burning powders at lower pressure.

[45r]

If the barrel isn't hand-lapped,fire-lap it and you'll see an improvement in accuracy.
My Ruger bisley 41 mag shot a round 2 inch a 50 and now 1 inch after fire-lapping.
It has a slightly over 2 pound trigger which helps also.

[cbrick]

Carsten, cylinder throats are made to guide the boolit to the barrel, and they work best when the boolit will slide into the throats with minimal resistance.

From post #29, that is correct. Far too many people look at a revolvers throats as sizing dies. They are not even though they work superbly as such. No matter how big you size your bullets they will be throat diameter when they exit. From an accuracy point the bullet should be a mild snug fit in the throats and not be sized down going through the throat and then blown back out in the bore or forcing cone should the bore be a bit too small or large. The less the bullet is molested the better, they fit the throats which match the groove diameter. What exits the muzzle is what you chambered plus rifling engraving which is the difference between bore diameter and groove diameter. The sole purpose of revolver throats is to align the center line of the bullet with the center line of the bore.

Rick