Bullet sizing questions and chamber throat reaming

[AggiePharmD]

I own a Model 57 and Model 586. Slugging the bore on the 586 resulted in 5 lands/grooves which I didn't remember would be the case until AFTER I'd produced the slug.

Question: Guys that shoot these two models, what are you sizing to?

Question: Chamber throats can be too small and affect accuracy but what about being too big? For instance .4125 for a .410 or .411 and .3595 for a .358 or .359?

TIA

[DougGuy]

The problem I run into sometimes with a .359" is that the assembled round will hit the shoulder of the chamber and not want to go all the way in, even if the cylinder throat has been properly sized for the boolit in question. I would suggest, IF you have a sample boolit that you want to use, sized to whatever size you want to use, load it in a dummy case nose down, and crimp it flush with the case mouth. Now, see if this will seat in all 5 or 6 or 7 chambers without running into the issue of the case being larger than .380" right behind the crimp. If it will, then you could proceed with cylinder throat reaming to fit that boolit.

It makes no sense to ream cylinder throats to suit .359" or .360" boolits if those boolits won't then seat in the chambers after assembly.

I almost *always* request dummy rounds from guys I do cylinder work for in .357 caliber, so I can see if after reaming everything is going to work for them. I caught a few "gotchas" by doing this before they were ever sent back out to the customer.

Edit: Your question about being too big.. if the boolit is close to the throat diameter, there won't be a problem. When you have throats that are .003" and .004" over the boolit diameter you will have problems. The barrel, with it's forcing cone, doesn't seem to care as much if the boolit is oversized. Obviously there comes a point where too much difference will cause problems but in a revolver cylinder dealing with the dimensions you mentioned I don't think you will have any problems there, and will still shoot factory j-worded ammo too.

I once owned a Ruger BH in .45 Colt, a convertible, with .456" throats in both cylinders. Accuracy was HORRIBLE! Then again I was shooting .451" and .452" boolits as well as j-words. Would it have performed better if I was sizing .454" or honed out a sizing die so the boolit was a light drag fit in the throats? Of course it would. I sent this back to Ruger and asked for two new cylinders with .4515" throats, and they DID exactly as I asked! .4515 on both cylinders. The groups immediately shrunk by 2/3rds, and even more after firelapping the bore.

[AggiePharmD]

Great explanation. I'll give this a shot before I send you the cylinder. I know for a fact on throat is closer to .356 than .357 so it's gotta be done. I'll let you know.