300 nmi reamer dimentions?

[jb1023]

I am ready to place my order, just received final drawing from Manson's last night, but want to see what you think of these specs for a 300 NMI w/35* shoulder.

Shoulder = 35*
Freebore = .2150
Body taper = .0241
Case OAL = 2.5020
Neck length = .28767

Does this look like it will work well for fire forming parent cases and handle a Hornady 225 ELD-M?

For those of you already running a NMI, what is your H2O capacity?

 

[highdrum]

You should post the reamer drawing up for us to look at. Sounds like you're moving the neck/shoulder junction ahead, as well as reducing taper and going to 35° you're going to lose a lot of neck by forming that much extra case.

 

[jb1023]

You should post the reamer drawing up for us to look at. Sounds like you're moving the neck/shoulder junction ahead, as well as reducing taper and going to 35° you're going to lose a lot of neck by forming that much extra case.

A print I obtained for a 300 NM has a neck of .318 and a 20* shoulder so I'm thinking this is a standard. So my neck will be .030 shorter. The body taper is essentially the same, .001 diff.

 

[jb1023]

The Manson is the 300 NM standard(?). Hopefully this is okay to post, it is not my drawing, just one that Manson had on file. The second is from JGS and is the one I plan to use, albeit with Manson doing the reamer.

 

[elkaholic]

Personally, I would run less taper and leave the neck shoulder junction alone. The neck will end up shorter whether you like it or not because it will shrink in length when you fire form it by likely .015". It you don't shorten the original oal, then your bullet will be jumping an excessive amount of end clearance from the case neck mouth to the lead. (Same affect as over trimming your brass)

 

[highdrum]

Your improved version has neck/shoulder junction and neck length in same dimensions as my Manson non improved reamer. Some guys will actually shorten the neck/shoulder to base length by 5-10 thousandths for a slight crush fit on virgin brass for fire forming purposes.

 

[IdahoCTD]

The 225's have a rather long bearing surface. If I was throating just for them I'd go .250"+. Many people use .280" for 230 Bergers and I'd bet the 225 have at least that long of a bearing surface, I don't feel like measuring them. My reamer has a .235" throat and 230 Bergers in mine have to be seated rather deep.