7mm Rem Mag reamer option pros/cons?

[DepthAfield]

Cross-posted from the LRI group buy thread:

I will be sending in my parts to LRI for my LR build soon, but wanted to pick the general populations brain first.

Rifle will be chambered in 7mm Rem Mag (26" 1-9 Bartlein). I am beginning to put together a reloading setup but will be using commercial ammo for a while at first. Holding on to the brass for future reloads. My question is the choice between the two reamer choices, given my long-term reloading plan:
7MM REMINGTON MAGNUM MIN SAAMI SAAMI SAAMI HSS GO
7MM REMINGTON MAGNUM (180 GRAIN) 0.3170 1*30 0.22 HSS GO/SHOULDER
Should I go for the former until a rebarrel, at which time I'd probably be 100% reloading? Would there be a downside to the latter chambering for the heavier bullets if I started out shooting say 168 grain commercial?

Not new to shooting, but quite wet between the ears in regard to micro-management of the chamber/ammo.

Will primarily be using the rifle for killing paper and steel at long range, and secondary use of hunting elk (also at LR)

Thoughts, concerns, insights?

 

[.284]

I'm not sure there is an easy pick since you're not going to reload right away.
I use min spec reamers with separate throating dies so I can set the distance to the lands myself.
I like to be able to have the bullet still in the neck of the cartridge when it touches the lands. I have found that most factory 7 mag reamers have long throats and should you want to use bullets which are sensitive to settings depths like some Bergers are that if you try to seat them out close to the lands that there is really not enough bearing surface in the case neck to keep run out down to a minimum. Since the rifle build will be the most expensive part In relation to your reloading set up I would suggest you consider where your reloading knowledge will be in a year or so and remember how long it took to have everything smithed. You may be happier in the long run to consider a separate throating reamer and make up some dummy rounds to send in with your build. By doing this you will be able to ensure that whatever bullet you want to use fits in your mag and allows you room to seat them out further to chase the lands as your throat erodes if need be.
Just my thoughts on what I have learned looking back through all the builds I have done

 

[DepthAfield]

I'm not sure there is an easy pick since you're not going to reload right away.
I use min spec reamers with separate throating dies so I can set the distance to the lands myself.
I like to be able to have the bullet still in the neck of the cartridge when it touches the lands. I have found that most factory 7 mag reamers have long throats and should you want to use bullets which are sensitive to settings depths like some Bergers are that if you try to seat them out close to the lands that there is really not enough bearing surface in the case neck to keep run out down to a minimum. Since the rifle build will be the most expensive part In relation to your reloading set up I would suggest you consider where your reloading knowledge will be in a year or so and remember how long it took to have everything smithed. You may be happier in the long run to consider a separate throating reamer and make up some dummy rounds to send in with your build. By doing this you will be able to ensure that whatever bullet you want to use fits in your mag and allows you room to seat them out further to chase the lands as your throat erodes if need be.
Just my thoughts on what I have learned looking back through all the builds I have done

Here's the rub: This is a complete build. I'll be sending in the parts and the unchambered Bartlein. The two reamers are the rem mags that LRI does. Working up dummy rounds and perhaps having a custom reamer made may be the option when it comes to rebarrel.

Am I understanding it correctly that the latter choice of the two would (in a nutshell) be more jump to the lands with commercial with less than 180gr? Would it be an appreciated effect on accuracy overall with say 168gr?

Experience in a year quite frankly will depend on availability (and price!) of raw components.



edit: It's a AICS chassis/magazine, in regard to fitting in the mag

 

[.284]

I believe you would be correct in assuming that there would be more jump with lighter than 180's but that would be dependent on the ogive really as all factory stuff will be loaded to the same overall length. A call to the smith would confirm that though. It's hard for me to guess how the 168's (I assume berger's) would react accuracy wise. I know that when I used a sammi spec reamer for a 9 twist barrel that I could not get the 168's to shoot for the life of me. I was using the hunting vld's. My assumption was that there was too much freebore and that in the time between the bullet leaving the neck and touching the lands that they were not consistently entering the bore and possibly canted somewhat from shot to shot. The 180's worked well but I was hand loading and I'm not aware of factory any factory loads using the 180's.
If you've yet to send in the parts it may be worth a call to discuss the reamers available versus where you want to go with this build. I use pacific tool and gauge reamers. They may have something available immediately or the wait may not be too long. Dave Kiff has always made time to talk to me on the phone and I've never been led astray by him.
In the end I'm sure your rifle will shoot something well. It really just depends if you want it to shoot something in specific well

 

[idahoorion]

DepthAfield.

I believe all LRI reamers are min spec. so you will get a nice chamber where your brass will not grow in the shoulder much and you be able to reload with min. shoulder setback to make the cases last longer. The sammi spec chamber is just like you would buy in a commerical gun. Likely to set the 168 and more likely the 180's you will need a longer freebore to have the bullet where it has a good relationship with the case shoulder/neck. The second reamer is a reamer set up for the 180 class bullet. it is a .317 neck which is a no turn neck, it has the 1*30 lead angle which is optimized for VLD bullets and the .22 freebore so you can seat the longer 180 bullets out. LRI did my build and I borrowed a similar reamer except it had .188 freebore for the 168's and still is pretty good with 180's. I think if you wanted a different freebore LRI could neck ream it for you. it seems to be pretty standard for most gunsmiths. You can also do this later if go with a sammi reamer to shoot factory ammo and then you start to reload and need to lengthen the freebore.
have fun!

Idahoorion

 

[DepthAfield]

DepthAfield.

I believe all LRI reamers are min spec. so you will get a nice chamber where your brass will not grow in the shoulder much and you be able to reload with min. shoulder setback to make the cases last longer. The sammi spec chamber is just like you would buy in a commerical gun. Likely to set the 168 and more likely the 180's you will need a longer freebore to have the bullet where it has a good relationship with the case shoulder/neck. The second reamer is a reamer set up for the 180 class bullet. it is a .317 neck which is a no turn neck, it has the 1*30 lead angle which is optimized for VLD bullets and the .22 freebore so you can seat the longer 180 bullets out. LRI did my build and I borrowed a similar reamer except it had .188 freebore for the 168's and still is pretty good with 180's. I think if you wanted a different freebore LRI could neck ream it for you. it seems to be pretty standard for most gunsmiths. You can also do this later if go with a sammi reamer to shoot factory ammo and then you start to reload and need to lengthen the freebore.
have fun!

Idahoorion

That pretty much enlightens me a bit. Most likely (besides commercial ammo) I will be loading A-Max 162s and Berger 180s.

So SAAMI for starters, and then freebore if need be later. By the time powder, bullets and primers are in stock, it should be all crystal clear.

 

[Gray]

I shot a 7mag that was a hammer, mine was chambered with a Min SAAMI reamer that had a .315 neck and was throated for the 180 VLD. I ended up liking the 168 VLD better since the BC was close to the 180 but had less recoil. Mine also shot HSM 168 VLD Factory ammo in 3/8" groups. Really regret selling it...

 

[mdesign]

I have a min SAAMI chamber that works very and I would probably recommend that you start there. One of the watchout's of longer throating is if the loaded round will fit into the mag box when you do so. If not, you end up single feeding. Chad should know the answer to this so I would ask if mag feeding is a concern to you

 

[DepthAfield]

If I understand correctly, the ogive on the VLDs would relate to the lands similarly to a non-VLD. But with more of the bullet forward. Am I kind of correct there?


edit: CBTO would be similar, but OAL would be different?

 

[DepthAfield]

This looks like it is good reading on the subject: http://www.bergerbullets.com/effect...coal-and-cartridge-base-to-ogive-cbto-part-2/

So much to learn! After further reading I am sorely tempted to purchase a separate seater die for each of the two bullet types.