Possible tight chamber neck?

[redneckdan]

Hi yall

I picked up a T/C made .375 JDJ carbine barrel.  While constructing loads for this barrel I noticed that the loaded rounds seem to chamber tightly. 

I took some measurements.


My reloads:

290gr RN

Loaded
.3993"
.3994"

Fired
.3978"
.3981"
.3975"


380gr LFN

Loaded
.3993"
.3997"

Fired
.3979"
.3977"
.3978"


Factory 220gr

Loaded
.3965

Fired
.3970

What do yall think?  It seems at best there is .0005" clearance with factory rounds and at worst a couple thou interference with cast bullet loads.  These bullets are sized at .378" because the barrel slugged at .3768"  Should I stay with the tight neck and turn the cases or should I try to find a .375 caliber neck reamer?

-Dan

[Slowpoke Slim]

I've measured some of mine:

Loaded rounds with 270 gr Hornady spire points:

.396
.3955
.3955

Fired brass:

.3995
.3995
.399

My brass is Remington 444 brass necked down. My necks measure:

.0125
.0125
.013


Mine's an SSK, not a TC. How thick are your necks? I would at least size those bullets down to .376. Maybe consider turning necks if they're thicker than say .013" . I have some factory 375 JDJ brass laying around somewhere. I'll look for it after supper. I doubt it could be any thinner in the neck though.

Yes it sounds like you're tight. You may have to give up on the cast bullet idea altogether, depending on how much accuracy you're expecting. You can always size them down to .375 or .374 and they'll shoot, but probably not very well.

I don't think I'd be firing any more of those over sized bullets down that neck, unless you were sticking to starting loads. You're going to make max pressure very quickly. The 375 JDJ is right up there at about the limit of the Contender frame IMO. I would be careful about over pressure loads in this cartridge, frame stretching is a real possibility here.

I don't know that I'd ream the chamber though, plenty of chance to screw it up and have to toss the barrel. If this had happened a few years ago, I'd say to send the barrel back to TC for replacement. But I seriously doubt TC has any of these barrels laying around to replace it with. I think that ship has (sadly) sailed.

[redneckdan]

The two options I have found so far are to either use a .400" 38-55 reamer to increase the chamber neck area or to neck turn the brass.  Most of my shooting is with cast.  The reason i went with a 'tender in the JDJ instead of an encore in H&H is that the JDJ can be fully utilized without exceeding the performance limits of cast.  If i am going to shoot a lot of jacketed I might was well have got the H&H.  The cases are from the T/C 220gr loads.  The neck thickness is .014"

[Slowpoke Slim]

Have you slugged just the throat area? I wonder if the throat itself is .3768?

You could always turn the necks down to .012, that may give you enough room. I don't think I would turn them any thinner than that.

My last choice would be reaming the chamber, but that's just me.