Mike i was checking the chamber length of my 357 mag barrel ( contender 10" ).I done the cerrosafe checked chamber length it is .045" longer than a 357 max case.Is this enough clearence? I have shot 8 rounds in barrel everything looks okay,cases fall out,primers are round,the loads were pretty accurate.How long is a 357 max chamber?

I get nervous running case mouth end clearances much less than about .020" for most chambers. This is figured from at least recommended trim length, and sometimes I run more clearance than that.

.045" end clearance for some applications is excessive, but on something like the Mag. it is ok. How many people stop to trim .357 Mag. cases? If they grow some in length, the end clearance keeps the user out of trouble.

Trim on .357 Max. is I believe either 1.6 or 1.610." My chambers are about 1.630" from memory.

Further to the clearance issue, if a person knows his exact chamber length and will do it carefully, he can sneak right up on the end of the chamber neck and come pretty close to zero end clearance, but this is something I have hardly touched on. It has been enough of a challenge getting the idea of size die adjustment and headspace across.

For some where the shoulders of cases have to be blown forward, I have set the chambers up with short necks. Then all cases are trimmed to rather exact case length equal to the distance from the end of the chamber neck to the breech face. Thus the case headspaces on the mouth of the case like a 9mm Luger, .45 ACP, .30 Carbine, etc. and the shoulder is fire formed forward. Usually when fireformed, the brass shortens some, and the fireformed length becomes the trim length, just a bit shorter than the overall length of the chamber. But this is another subject entirely. Just thought I'd stir it into the pot along with the other info about end clearance.

Smart thing for a savvy shooter to do is to learn what the actual chamber length is, then let his cases grow out to just under that length, but always leaving some room for error, remembering that interference at the mouth of the case jacks pressures up about as fast as the wrong powder can, no pun intended.

How do you determine what the overall length is? Use the barrel for the guage it is. Push a shoulder back too far on an overly long case and drop it in the chamber with the barrel OFF the frame. So long as the shoulder or other parts of the case do not touch the chamber, it will be the end of the neck in the chamber the case stops on. Measure how far the case sticks out, whack off just a few thous. short of that amount, and measure again. If it still sticks out a few thous. more than it is supposed to, tweak off the last few thous. until you get it exact. For general use, I would still leave at least .005" to .010" end clearance in case you make a mistake along the way, down the road. Depends on how detailed you like to work and how reliable your measurements are.

You will find some chambers cut with clearances a tenth of an inch, .1," or more. I have ground that much or more off the ends of the neck sections of more than one Clymer reamer. And years ago before I got smarter about reamers, I have used off the shelf Clymer reamers with those kinds of clearances! So just because my name is on it does not always mean it was cut with close tolerances..... depends on what point of the learning curve the job was done at. So it is a good idea to know what is in your chamber.... whether done someone else or me.

Mike