Gunsmithing 338 LM Reamer

[dustingaunder]

I have a couple barrels that were cut with an unknown reamer. Berger 300s at the lands are still seated well in the case. Approximately 3.842” COL to the lands. Would this be a standard Saami reamer? How much freebore do you think it has? I’d like to get a .338LM reamer with about .100 less freebore so I can load them to mag length with less jump. Then I can always throat longer if I want. I’d like to have a mag fed barrel and a long throated single feed barrel to keep the boat tail above the N/S junction. I can call Manson this week but was curious if you guys had any thoughts.

ETA: How much jump is too much? If I could just throat my existing barrel to around .200-.225 or so freebore I think that would put the bullets where I want for single feed. I’m already jumping .110 with the hybrids from a mag, is .200 going to matter?

I feel like my chamber is too long to mag feed and too short to single feed. I mostly single feed now to get the extra velocity but I know there’s more left on the table.

 

[Steel head]

There is a mag fed orientated 338 chamber.
338 lapua tactical match I think.

 

[dustingaunder]

I did some measuring today. I need about .100 more freebore to get the bullet where I want it in my existing barrel. Anyone know how much total freebore is required to get the bearing surface above the donut on the 300 Berger?

 

[dustingaunder]

Doing a little digging I think I’ve got a SAAMI or CIP chamber. Freebore on both is essentially around .125-.130 if I’m reading the prints correctly. I need about .225-.230 to above the dounut. I have two matching barrels. I think I’ll throat one out to the donut and try single shot with some N570 or RL33. 2750 feels too slow. If I’m still not happy I’ll AI it I guess.

 

[dustingaunder]

Talked to Manson when I ordered my throater. Looks like I’ll need about .255 total FB to seat the 300s above the donut. I seated a bullet out there and I am about .050 from being able to eject a live round from my TRG. I can push the bolt release and get it before I hit my cheek riser so not a huge deal. We’ll see how it turns out.