New .357 mag chamber specs

[coyotejoe]

A few days ago I got my handirifle back from H&R with a new barrel in .357 Mag, seven weeks from door to door and that included Christmas and New Years. The first thing I did after cleaning the bore was to pour a chamber cast. There is no throat as one usually expects to see in a rifle chamber, instead there is just a long gradual taper down from case mouth to bore. It measures about 1.850" from breech face to the first trace of lands. It also is a bit oversize at the base, about .386" more or less, it isn't perfectly round.
 I used some Federal American Eagle factory loads for barrel break-in and there was a pronounced swelling of the fired cases about 1/4" ahead of the rim. The accuracy of those was very disappointing, five shot groups running 3-5" at fifty yards. I've found that ammo to be quite accurate in other .357 rifles and handguns so I thought "oh brother, another dud". But some handloads with the Remington 180 grain JHP seated out did much better.  I never got a decent group with 158 grain JHPs even when seated out long but the 180s gave me 1-1 1/4" groups with two different powders, so that was encouraging. Even the 180s could not be seated out to reach the lands with .357 magnum brass.
 I intend to rechamber to .357 Maximum and have already ordered a reamer so the brief run through with .357 mags was just an experiment but all in all I have never encountered a rifle so picky about loads, from one inch groups to five inch groups from the same rifle on the same day, that seems pretty wild to me and I have no doubt the lack of any real chamber throat has much to do with it.

[Haywire Haywood]

Got any 357DW brass to try in it?  Won't solve that base problem tho, but neither will the max reamer... good luck.

Ian

[quickdtoo]

I think Ian meant 360 Dan Wesson brass,  it fits in mine after I trim .010" off it, otherwise it's sticky getting out of the chamber, it definitely would after being fired with a full house load. 

Tim

[PHATINJUN]

mine works well with the 360dw brass no trim needed it shoots 180 and 200 gr under 1" at 50 yards with limited testing so far .kurt

[Vic49]

So 360 DW can be shot out of a .357 factory barrel?

[PHATINJUN]

works well in mine w/no trimming fact is when i start testing it again i believe the max brass will need minimal trimming to fit.might be cheaper to trim the max than to ream and there can't be that much difference in performance. but each chamber seems to be differant. kurt

[MSP Ret]

.360 DW fit, fired, and ejected from my .357 Mag factory barrel with no trimming. As has been said, each chamber may be a bit different....<><....

[coyotejoe]

Each chamber different but none of them right!    I guess that is what makes Handi-rifles interesting, trying to find ways to work around the factory defects to get satisfactory results from an unsatisfactory rifle definitely keeps one thinking. I tried some cases fired in the handi and they would not chamber in any of my three revolvers, they'd enter about 1/3 of their length before becoming too tight, I don't know what sort of chamber specs H&R may use but clearly not up to industry standard. I never had any intention of interchanging loads between rifle and revolver since I favor different loads for different purposes but this would be a problem for anyone who does have that intention. The good news is that if you don't enjoy trimming brass you will never have to trim .357 mag brass for this chamber!