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Reaming a chamber?

7K views 9 replies 5 participants last post by  tnekkc 
#1 ·
Well , I just ordered an H&R Trapper model in 357 Mag. I am going to have this turned into a 357 Maximum and that is where I have some questions.

I have talked to a local gunsmith and was quoted $125 for the job. I don't know if that is in line or not...any comments? He told me he has to rent a reamer and I assume I will get a SAAMI chamber which after reading on Belm's site , that is not the best for accuracy because of the forcing cone in the chamber.

Is a chamber reamer necessary for the job? I am not actually cutting a new chamber but really just lengthening the mag chamber right? That leads to another question...I read up on using a 380 reamer that doesn't have the chamber profile with a forcing cone like the Maximum uses. I imagine all you are doing there is lengthening the throat to accept the longer cartridge.

I guess a little advice would be appreciated. I have never had a project like this done before but am thinking with the cost of a gunsmith vs. the price of renting reamers I would attempt this on my own if it isn't too complex of a job.

Thanks,
Jeff
 
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#4 ·
Thanks guys. I actually spoke with Mike Bellm today about this and he gave me the contact info for David White. Very nice gentlemen , both of them. Mike actually referred David for the job and said he is set up better for the H&R. So off to him it goes!

I have been looking for a rifle to shoot the Maxi through for a while now and for the money this little H&R Trapper is hard to beat. I was going to use a No.1 and before I spend that kind of money this H&R will be great for testing the Maxi in a rifle.
 
#7 ·
You'll be very happy with the work David does and find the MAX, in a rifle-length barrel, is a lot more "fun" than a revolver. It's even suitable for deer out to ~200 yards, with the right handloads and is 1-5/8" legal, if you live or hunt in a state with such restrictions. You probably already know this, but one of the advantages to reaming a .357Mag to .357MAX is that you can frequently cut out that ridiculous forcing cone. I'm not sure if H&R's rifle barrels even have it, but I know the factory T/C barrels do/did. (Why any manufacturer would do that to a rifle barrel, regardless of SAAMI specs, is completely beyond me!)
 
#8 ·
In a rifle, you might be happier with a tighter and cheaper change to the chamber, than a SAAMI reamer.

If you measure you loaded cartridges before you put them into the chamber, and measure the chamber, the difference is clearance. That clearance can hurt accuracy in a straight wall cartridge.

When shooting groups at 100 yards, this make a difference, but if you just want to feel recoil, it does not matter.
 
#10 · (Edited)
What I found for shooting groups with 45acp is that if I re sized the loaded ammo, it pinched the .452" bullet down to a much smaller size inside the case mouth.
The Lee Carbide sizer has a carbide ring with an inside diameter of .467".
Brass or cartridges will come out ~.469".
So I reamed the chamber with a .469" reamer.
I then throated with a 45acp throater until the bolt just closed on a 230 gr loaded cartridge at 1.275".
Through sizing the base of the cartridge is another issue.

The carbide ring in my RCBS 357 mag will pass a .371" pin gauge.
357 max as well as 357 mag have ~.009" wall thickness at the neck.
If the brass come out at .373", then the ID of the brass is .355".
The lead cannot spring back a full .002" like the brass can.

When I lengthen a 357 mag revolver chamber, I use a .380" straight fluted reamer. But what can I hit with a revolver? I am great shot with a scoped rifle.

The rear of your chamber is probably .381" and the base of the your 357 max brass is probably .376", so you already have .005" clearance in the rear and no way to fix it. The way to gain accuracy is how small the additional reaming can be done.

If I had a handi rifle barrel in 357 mag that I wanted to convert, I would probably be in the neighborhood of a .373" reamer. They cost ~ $23 and come in .001" increments.
http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO=1704924&PMT4NO=81515581

The exact size chosen would depend on the loaded ammo I produced and used as the headspace gauge.

I would bet money that any gunsmith you can find in the phone book is going to want to chamber it so that factory ammo will fit. .380" is my guess.

There are guys that can compete with me in straight wall Schutzen rifles. They seat the bullet when chambering, and shoot cast bullets. That way the bullet enters the bore concentricly.
But with a 357 max rifle, I think you want to go faster than cast velocities, or you would stay at 357 mag.

If you do go to a gunsmith and let him have his .380" way with it, you can optimize with handloads by seating long and jamming into the lands. Pulling an unfired round could get a bullet stuck and powder spilled, but it is easy enough to have a cleaning rod around.
 
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