.357 Rem Maximum throat design

[Spokerider]

To those of you that have re-chambered a .357 mag to .357 Rem maximum, what throat design did you decide upon and why?

I have a Uberti Baby Rolling Block in .357 mag that I am going to rechamber to .357 maximum. I made a chamber slug of the carbine, and found that the throat design was a short forcing cone design about .200-.220 in length, with the bore at the lands being approx .3475 and the bore in the grooves being about .355

I can see that the .357 maximum case length will pretty much remove all of the current .357 mag throat, leaving plenty of fresh bore material to form the new throat and freebore.

I do NOT want the SAAMI revolver-type long forcing cone where the bullet base is left unsupported. It seems that all of retail reamers are of this SAAMI design........grrrrr. I am thinkking that I need to have a reamer made or adapted to a throat design of my dimensions. I do not have a lathe to do this myself.

Here`s a link to some reading on the subject
http://www.bellmtcs.com/store/images/downloads/357%20Max%20Handloader%2094.PDF

http://www.bellmtcs.com/store/index.php?cid=120

http://www.lasc.us/BellmThroats101.htm


So.......I`m thinking of a throat that is stepped down from the case mouth to .359, with a taper to .357 where it will meet the rifling. Not sure about the length of the throat just yet. I want it just long enough so the bullets I shoot http://www.castperformance.com/Detail.bok?no=5 will be off the lands by .010-.015 .


Thoughts?


Also, anyone have a .357 max reamer for sale or rent??
Alternatively, I`m looking to these guys for a reamer http://www.jgstools.com/mainarea.html

[leftiye]

You've got a 9mm barrel. Ideally you would shoot a .356" boolit (.357 will work too). Don't taper your freebore. In fact you can do without freebore if you want. Use a slow taper leade, and a minimum ( .356 boolit plus .012" X2 + .380 plus .002" for clearance or a bit more) .382" chamber at the case mouth. Then you can just seat into the leade or give it a little freebore. .002" freebore may be too much. The Max likes 180 and 200 grain boolits, and they can be seated thumb tight in an unsized case, and seated out sum if you want. Some guys here have gotten 2200 fps. from the 200 grainer with VV N120 (I think) and AA MP3100. 1600 works good too, but doesn't get the last Nth of speed. Dave Manson at Manson reamers will work with you (as it looks like you need a custom reamer). Nice guy.

[45r]

I got a max RIFLE reamer from Dave Manson and it cost 120 bucks.I did my 12 inch 357mag contender barrel.It shoots great,quality is excellent.Wish I could find a good deal on a 357mag rifle or rifle barrel for contender or encore.Love the max in contender.No problem getting boolits to engrave.Ragged hole groups with no leading.If you get one make sure it is a rifle reamer and not one for a revolver with the crappy forcing cone.I talked to him and he E-mailed me a drawing of his rifle reamer,you can go from there if it looks like what you want.The rifle reamer is custom and cost a little more.

[Spokerider]

Thanks fellas, your info is a great help.
Does Dave Manson have a web site I can visit?

[45r]

Thanks fellas, your info is a great help.
Does Dave Manson have a web site I can visit?

Mansonreamers.com

[Spokerider]

Thanks 45r.

I contacted Dave at manson reamers, and he can alter the throat design of a standard SAAMI .357 max reamer to make it more rifle barrel friendly.

Have a question about chamber reamers.........
Solid pilot bushing or removeable, what`s the difference and advantages / disadvantages.
Solid pilot is $30 cheaper.
This is likely a one-time use for me.

[lathesmith]

Hey guys, I've seen this in discussion before... and I am hoping some of you machinist/gunsmith types can clarify a few points I have been wondering about. When you say that the standard reamer is a revolver type with a forcing cone, do you mean that the reamer is designed to cut a chamber meant to transition to a forcing cone? After all, a revolver's forcing cone isn't part of the chamber, or even the cylinder for that matter.

If this is the case, then when chambering a single-shot barrel for a straight-wall cartridge like the max, why not just use a boring bar, cut a relief for your brass, and then cut just enough relief for your boolit? I know a pro wouldn't do it this way because it's too time-consuming, but for one-timers why not do it this way?

BTW Spoke, that sounds like a great project! At one time I had one of those Uberti rolling block pistols in 357 mag, I'll bet that carbine is really neat. I currently have a T/C carbine in 357 mag, it's my favorite barrel.

lathesmith

[45r]

Thanks 45r.

I contacted Dave at manson reamers, and he can alter the throat design of a standard SAAMI .357 max reamer to make it more rifle barrel friendly.

Have a question about chamber reamers.........
Solid pilot bushing or removeable, what`s the difference and advantages / disadvantages.
Solid pilot is $30 cheaper.
This is likely a one-time use for me.

The solid pilot is the one to get for 357mag to max for what you want.My brother did mine with a keyless chuck by hand.The removeable ones are used by the custom guys like MGM.I might put mine up for sale on E-bay but want to do a rifle barrel someday.I've only used it once.The one I got is a modified reamer.They cut the cone part to a rifle throat.

[45r]

Hey guys, I've seen this in discussion before... and I am hoping some of you machinist/gunsmith types can clarify a few points I have been wondering about. When you say that the standard reamer is a revolver type with a forcing cone, do you mean that the reamer is designed to cut a chamber meant to transition to a forcing cone? After all, a revolver's forcing cone isn't part of the chamber, or even the cylinder for that matter.

If this is the case, then when chambering a single-shot barrel for a straight-wall cartridge like the max, why not just use a boring bar, cut a relief for your brass, and then cut just enough relief for your boolit? I know a pro wouldn't do it this way because it's too time-consuming, but for one-timers why not do it this way?

BTW Spoke, that sounds like a great project! At one time I had one of those Uberti rolling block pistols in 357 mag, I'll bet that carbine is really neat. I currently have a T/C carbine in 357 mag, it's my favorite barrel.

lathesmith

You can cut the chamber with a body reamer that cuts only where the 357 max brass ends.The long cone shape on my T/C 357mag barrel was .4 inch long and still would have room for the boolit to be seated right without being too deep in the brass.I didn't go that way in case I wanted to do a custom rifle on a SS action.I wish I could find a SS action with a matching stock and forend and match it up with a Handlapped barrel from one of the custom makers like Shilen.Then I could use my 357max reamer to make a super tack-driver rifle that would be easy to work with and didn't use a lot of powder or need a lot of alloy to make lots of boolits.

[BABore]

A solid pilot reamer has the pilot diameter established at a nominal size. It will be just a shade the under nominal bore diameter of 0.350. If your bore diameter happens to be on the big side, then you have the potential of having the chamber not quite concentric to the bore. Reamers that take removable pilots can be custom fit to the bore diameter. You usually get some incremental sizes to check fit.

Since your getting a semi-custom reamer for this, it may behove you to look at other dimension on it. Namely the chamber diameter. You need to work backwards from the groove and throat size, planned boolit diameter, and case wall thickness. Set the chamber dimensions so you have just enough clearance for safe boolit release. Otherwise, you may end up with a sloppy chamber. This will cause a couple different accuracy concerns. One, the case will lie at the bottom of the chamber. The boolit won't be aligned with the bore. This can be later remedied by only neck sizing the cases to just below the boolit base position. Two, when the case expands to seal the chamber, excessive slop between the case ID and boolit OD can allow the boolit base to cant. If the boolit enters the rifling canted, the boolit base will exit the muzzle unevenly.

Reamers also rarely cut dead on their measured size. Usually just a little bit bigger. Your pilot fit also affects this.

[Spokerider]

A solid pilot reamer has the pilot diameter established at a nominal size. It will be just a shade the under nominal bore diameter of 0.350. If your bore diameter happens to be on the big side, then you have the potential of having the chamber not quite concentric to the bore. Reamers that take removable pilots can be custom fit to the bore diameter. You usually get some incremental sizes to check fit.

Since your getting a semi-custom reamer for this, it may behove you to look at other dimension on it. Namely the chamber diameter. You need to work backwards from the groove and throat size, planned boolit diameter, and case wall thickness. Set the chamber dimensions so you have just enough clearance for safe boolit release. Otherwise, you may end up with a sloppy chamber. This will cause a couple different accuracy concerns. One, the case will lie at the bottom of the chamber. The boolit won't be aligned with the bore. This can be later remedied by only neck sizing the cases to just below the boolit base position. Two, when the case expands to seal the chamber, excessive slop between the case ID and boolit OD can allow the boolit base to cant. If the boolit enters the rifling canted, the boolit base will exit the muzzle unevenly.

Reamers also rarely cut dead on their measured size. Usually just a little bit bigger. Your pilot fit also affects this.


Good info to know, thanks.
Dave Manson sent me a drawing of his .357 Rem Maximum reamer. The pic showa that the case at the web is .380 and the diameter at the case mouth is .379

Would this tighter fit at the mouth ensure that the case at the mouth does not stretch too much upon firing, so the bullet base does not get canted to the side as you have said can happen?

[Spokerider]

The solid pilot is the one to get for 357mag to max for what you want.My brother did mine with a keyless chuck by hand.The removeable ones are used by the custom guys like MGM.I might put mine up for sale on E-bay but want to do a rifle barrel someday.I've only used it once.The one I got is a modified reamer.They cut the cone part to a rifle throat.

Me thinks you should just sell the reamer to me :smile:
In the event that you need it again, I will still have it to send back your way.
It`s a one-time use for me too.

[45r]

Me thinks you should just sell the reamer to me :smile:
In the event that you need it again, I will still have it to send back your way.
It`s a one-time use for me too.

I might sell it later,I'm getting bug hole groups with my contender using 185 and 215 grain GC boolits and I'd probably regret not having it around in case I find a rifle or rifle barrel to do.Shipping to Canada might be too expensive and this time of year might not be a good time to ship something.Wouldn't want it to get lost.

[Spokerider]

No worries!

[Spokerider]

Well, I have a reamer coming from Dave Manson. Will be able to get this project underway shortly.

Have a few questions about using a reamer to re-chamber by hand please.......


Cutting oil?? A high sulfer content oil? something like a thread cutting oil? Does the type of oil I use really make a difference?

How much pressure will I need to apply to BEGIN the cutting process, and how much pressure will I need to apply to CONTINUE the cutting process? If you could reccomend a pressure in lbs of pressure please, or ounces, to give me an idea of how hard to push, and not push on the reamer.

Trying to avoid any reamer chatter and related complications......as I`m not sure why or how chatter comes about.

I`ve read not to turn the reamer counterclockwise, so I won`t do that.

Thanks.

[45r]

Well, I have a reamer coming from Dave Manson. Will be able to get this project underway shortly.

Have a few questions about using a reamer to re-chamber by hand please.......


Cutting oil?? A high sulfer content oil? something like a thread cutting oil? Does the type of oil I use really make a difference?

How much pressure will I need to apply to BEGIN the cutting process, and how much pressure will I need to apply to CONTINUE the cutting process? If you could reccomend a pressure in lbs of pressure please, or ounces, to give me an idea of how hard to push, and not push on the reamer.

Trying to avoid any reamer chatter and related complications......as I`m not sure why or how chatter comes about.

I`ve read not to turn the reamer counterclockwise, so I won`t do that.

Thanks.

I got my brother to do mine since he has the tools being a machinist.He used a special oil and a large pro grade keyless chuck.He took his time,took the reamer out several times,removed chips,reapplied oil and kept cutting till it was done.He said you don't want the reamer to get hot and used the keyless chuck to get a good feel and said it works well for him and he knew just how much tension to apply to the reamer and do it.You can probably do it yourself but I like having someone that has years of experience for stuff like this.It didn't look hard but I'm glad he did it.It looked like no big deal for him.No chatter,came out real smooth looking and shoots real good.I think I'd take whatever I had done back to him in the future,he says a lot of things can be done better by hand if you have the experience and the feel for it.

[rockrat]

I rechambered my rifle using a regular tap handle and "mississippi mud", a MoS2, moly disulphide lubricant. It cut quickly, with only maybe a couple of ft-lbs of torque.

Someone, don't remember which site, recommended to use a fine artist paint brush and put a little white paint in the recess for the rim, and when the reamer starts cutting the paint you only have a few thousandths to go.

[Eutectic]

For a singleshot I'd cut the chamber first only to max. case length. I would throat separately and specifically for the bullet type I wanted to use. Any "wallow" room (as in tapers) with lead boolits flirts with or downright seduces accuracy.... I like the newer cutting fluids for tapping and reaming. Use these, not greases or oils. I used white lead many years ago before it became dangerous!

Eutectic

[Spokerider]

I rechambered my rifle using a regular tap handle and "mississippi mud", a MoS2, moly disulphide lubricant. It cut quickly, with only maybe a couple of ft-lbs of torque.

Someone, don't remember which site, recommended to use a fine artist paint brush and put a little white paint in the recess for the rim, and when the reamer starts cutting the paint you only have a few thousandths to go.

I like the paint tip.
Cut too far into the rim and the headspace is buggered.........I`m aware of that.