I would like a little guidance/opinion on spec'ing a custom reamer...
I want to make a 7mm SLR. My concept is simply a 7mm version of the 6.5mm SLR. If you're not familiar with the cartridge, here is a link to it:
http://6mmar.com/65_SuperLR.php
I'm not counting on this cartridge doing something "magic" that 7mm-08 can't do, but I do see a number of advantages. Here are some of my thoughts/desires:
-162amax @ ~2800fps from a 24"(ish) barrel
-175smk @ 2700fps
-Fit/feed from AW magazines (means 7mm-08ai is not a good choice)
-Use EASILY AVAILABLE and cheap brass that I won't care about if I lose it at matches
The 7mm-08 basically fits all these criteria, but it seems the 7mm SLR has a few key advantages:
-Loaded to 2.950", the bullet shank is north of the neck shoulder junction, it is not for the 7-08 (requires 3.000"). Thus, no worries about donuts.
-30* shoulder allegedly provides a little better case efficiency and is a design element of most of the worlds most accurate cartridge.
-The 6.5mm SLR case seems to provide some extra velocity over 260, that might translate to a little better speed in 7mm, but again, not "counting" on it.
-Longer neck/shoulder angle might make barrel last longer
-Looks a lot sexier than a 7-08
Here is the 6.5mm SLR reamer print:
After doing some prototyping on the bench, I determined with a chamber that accomodated brass 2.040" long, I would need .170" freebore to put a 162amax on the lands @ 2.950", and .150" FB to put a 175smk on the lands at 2.950". After necking 10 .243 cases up to 7mm and seating a bullet, I found that 9 of the loaded neck diameters were .311" or .312". One of them was .314".
I contacted JGS reamers to cook up a quickie print. What I've got is identical to the 6.5mm SLR reamer print above except the neck diameter, and consequently, the neck length (a couple thousandths different).
My intent was to buy the 6.5mm SLR dies, then bore the neck of the sizing die .020" to allow the 7mm neck to reach the bushing and buying the appropriate 7mm neck bushing and 7mm seating stem from Redding.
Questions:
1. Does it make sense to keep all the body dimensions identical to the 6.5mm SLR so that the 6.5SLR sizing/seating dies will work properly?
2. Does it make sense for the brass length the chamber will allow be identical between 6.5 and 7? Or, should I shorten the 7slr chamber ~.005"? I have a giraud trimmer, so I don't require a bunch of growing room in the chamber.
3. I am not interested in a super tight "match" type chamber. I don't want to neck turn. Based on my 10 cases I necked up and loaded, ought I go with a .315" neck in the chamber - and consequently sort my brass and cull the occasional fat one, or should I bump the neck diameter up to ~.317" or .318" to accomodate anything winchester/remington throws at me? For reference, the SAAMI neck diameter for 7mm-08 is .316".
4. I figured I'd spec out a FB of .160", to split the difference between the 162amax and 175smk @ 2.950". Does that make sense, or should I shorten it a little to give myself some room to "chase the lands"? If I shorten it much, the bullet shank will start to get into the NSJ, defeating some of the purpose of the project.
5. Is there anything I'm missing?
I want to make a 7mm SLR. My concept is simply a 7mm version of the 6.5mm SLR. If you're not familiar with the cartridge, here is a link to it:
http://6mmar.com/65_SuperLR.php
I'm not counting on this cartridge doing something "magic" that 7mm-08 can't do, but I do see a number of advantages. Here are some of my thoughts/desires:
-162amax @ ~2800fps from a 24"(ish) barrel
-175smk @ 2700fps
-Fit/feed from AW magazines (means 7mm-08ai is not a good choice)
-Use EASILY AVAILABLE and cheap brass that I won't care about if I lose it at matches
The 7mm-08 basically fits all these criteria, but it seems the 7mm SLR has a few key advantages:
-Loaded to 2.950", the bullet shank is north of the neck shoulder junction, it is not for the 7-08 (requires 3.000"). Thus, no worries about donuts.
-30* shoulder allegedly provides a little better case efficiency and is a design element of most of the worlds most accurate cartridge.
-The 6.5mm SLR case seems to provide some extra velocity over 260, that might translate to a little better speed in 7mm, but again, not "counting" on it.
-Longer neck/shoulder angle might make barrel last longer
-Looks a lot sexier than a 7-08
Here is the 6.5mm SLR reamer print:
After doing some prototyping on the bench, I determined with a chamber that accomodated brass 2.040" long, I would need .170" freebore to put a 162amax on the lands @ 2.950", and .150" FB to put a 175smk on the lands at 2.950". After necking 10 .243 cases up to 7mm and seating a bullet, I found that 9 of the loaded neck diameters were .311" or .312". One of them was .314".
I contacted JGS reamers to cook up a quickie print. What I've got is identical to the 6.5mm SLR reamer print above except the neck diameter, and consequently, the neck length (a couple thousandths different).
My intent was to buy the 6.5mm SLR dies, then bore the neck of the sizing die .020" to allow the 7mm neck to reach the bushing and buying the appropriate 7mm neck bushing and 7mm seating stem from Redding.
Questions:
1. Does it make sense to keep all the body dimensions identical to the 6.5mm SLR so that the 6.5SLR sizing/seating dies will work properly?
2. Does it make sense for the brass length the chamber will allow be identical between 6.5 and 7? Or, should I shorten the 7slr chamber ~.005"? I have a giraud trimmer, so I don't require a bunch of growing room in the chamber.
3. I am not interested in a super tight "match" type chamber. I don't want to neck turn. Based on my 10 cases I necked up and loaded, ought I go with a .315" neck in the chamber - and consequently sort my brass and cull the occasional fat one, or should I bump the neck diameter up to ~.317" or .318" to accomodate anything winchester/remington throws at me? For reference, the SAAMI neck diameter for 7mm-08 is .316".
4. I figured I'd spec out a FB of .160", to split the difference between the 162amax and 175smk @ 2.950". Does that make sense, or should I shorten it a little to give myself some room to "chase the lands"? If I shorten it much, the bullet shank will start to get into the NSJ, defeating some of the purpose of the project.
5. Is there anything I'm missing?
