Reaming 357 mag. throat & 357 max. chamber

[GrizzLeeBear]

I just traded for a 10" 357 mag. Contender barrel and bought a Lee 358-180-rfn group buy mold from a couple of members here. Was doing some measuring and it looks like this barrel has little or no throat (one of the earlier barrels from what I gather). Looks like I will only be able the seat the bullet to a COL of about 1.560", so I will not be able to crimp in the crimp groove. I also measured it with RCBS 35-180-Sil & 35-200-FN boolits. I will not be able to seat any of these out enough to crimp in the groove. Since this is a single shot, not being able to crimp in the groove is not a big deal, but I would also like to be able to shoot the same ammo. in my GP-100 crimped in the groove.
So my question is, can I just run a 357 throat reamer in by hand until a bullet seated in the crimp groove will chamber?

I am also planning to get a 14" 357 mag. Contender barrel (maybe & NEF, too) to rechamber to 357 max. I have seen a post hear about someone using a .381 chucking reamer by hand to extend a 357 mag. chamber to a max. chamber in a NEF. I would assume you could do the same in a Contender. Could you then use the same 357 throat reamer to do the throat for the max?

[nicholst55]

Let me take a shot at this. You can easily extend the throat on your Contender barrel to allow you to seat your boolits out to the crimp groove. In fact, I just recently did this to an NEF barrel in .45-70. NEF also cuts very short throats, at least in that caliber.

The trick here is to 'cut a little, and check a lot!' It takes very, very little cutting to do what you need. I loaded a couple of dummy cartridges with the boolits that I wanted to use and cut just enough so that they would chamber without engraving the rifling. It only takes a little 'twist!'

As far as opening up a .357 Mag chamber to .357 Max, I would think that the best way to do that would be with a chamber reamer. There are a couple of sources for rental reamers, so you won't necessarily have to buy one. They probably rent neck & throat reamers, too. Do a Google search.

[leftiye]

I've got an H&R .357 max with about 1/8 " of freebore. It's okay, but a 200 gr. Mtn Molds boolit seats out clear to the front of the grease groove! You can probably lengthen the chamber itself of a .357 mag to 357 Max length with simply a chucking reamer, and then use a throater to make the leade/freebore. Use a 357 max case trimmed to max SAAMI lenght (NO crimp, maybe a fired case or expanded with oversize expander or flaring tool = full diameter case mouth the desired full diameter of the chamber ) and cut it carefully until the case fits. Then do as Nichols says with a dummy case loaded as you want to use to fit the freebore/ leade with a throating reamer. As per the above example, not much freebore is needed, maybe about the width of the front driving band. No crimp is needed in these single shots, in fact no sizing is often okay, finger tight boolits.

Nichols, how did you lay out the H&R barrel, I've got one of those with that problem too! NO throat, NO leade.