6MM/55 SMc

A

Al Virgilio

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Has anyone experimented with any of the Smalley Mcpherson cartridges? I am thinking about building a custom rifle in 6MM/55 SMc. Where do you buy or how do you form the cases? I know Pacific Tool has the reamers. The information on the website is interesting, to say the least.
 
Case Design

The spherical shoulder seems to be the big selling point behind this particular design. The idea is improve the internal ballistics.
It would be interesting to have a 6PPC Reamer ground with that spherical shoulder, leaving everything else the same.
In the end, it might be another well thought out answer to a non existant problem. But the guys who came up with this did put forth a big effort, and according to the info, have some sound engineering data on their side........jackie
 
Al,

We shot a case like this for some time at our Varmint Shilo matchs.

http://www.brooksiebuffstuff.com/varmintshilo.htm

It is not far from what you are talking about, we called it a 6mmJD (basicly a 6 Rem Improved with the body/shoulder/neck junctions radiused) after my friend Jim Davis that designed it.

I loved the cartridge accept the availabilty of brass. We made ours from 7x57 Norma.

I don't beleive there was any performance advantage. I find it hard to believe that the bullet can be affect enough in the nano sec at time of ignition to make any difference?

What I did find was an advantage was case life and straightness. One of the problems with these improved case I have seen is keeping the case straight, the seem to banana very easily, the radius seems to help that. Why, no clue, just my observations. I have always wanted to do a 243 AI with the radius's junctions. But there are so many new things out, you just have to say WHY BOTHER?

Case stretch was vertually non existant. I think in the 3 years that I shot this case, I lost 3 cases. And that was only because I did not like the way they looked.

I would still be shooting this round, but someone used the reamer and gaulded the end of the reamer for the bushing :eek: When it came time to rebarrel, I did not want to wait for another reamer, so I went to a Dasher.

Jim has rescently had a reamer made with the same radius in 6.5 x 55. We are waiting to see how it performs.


Jackie, I have thought the same thing, it would be an interesting experiment. Let's talk about do one. I'll pop for the reamer. PM or email me.

Randy
 
Last edited by a moderator:
Ramsh00ter said:
We shot a case like this for some time at our Varmint Shilo matchs.

http://www.brooksiebuffstuff.com/varmintshilo.htm

It is not far from what you are talking about, we called it a 6mmJD (basicly a 6 Rem Improved with the body/shoulder/neck junctions radiused) after my friend Jim Davis that designed it.

I loved the cartridge accept the availabilty of brass. We made ours from 7x57 Norma.

I don't beleive there was any performance advantage. I find it hard to believe that the bullet can be affect enough in the nano sec at time of ignition to make any difference?
What I did find was an advantage was case life and straightness. One of the problems with these improved case I have seen is keeping the case straight, the seem to banana very easily, the radius seems to help that. Why, no clue, just my observations. I have always wanted to do a 243 AI with the radius's junctions. But there are so many new things out, you just have to say WHY BOTHER?

Case stretch was vertually non existant. I think in the 3 years that I shot this case, I lost 3 cases. And that was only because I did not like the way they looked.

I would still be shooting this round, but someone used the reamer and gaulded the end of the reamer for the bushing :eek: When it came time to rebarrel, I did not want to wait for another reamer, so I went to a Dasher.

Jim has rescently had a reamer made with the same radius in 6.5 x 55. We are waiting to see how it performs.


Jackie, I have thought the same thing, it would be an interesting experiment. Let's talk about do one. I'll pop for the reamer. PM or email m



Randy
Click to expand...

Ramsh00ter and Jackie,

Keep be posted on how the experiment goes. I am interested on the velocity spread or the consistency of pressure, but I guess that depends on what brass your using. May be Lapua will develop cases in the near future.
Correct me if I am wrong, but is this the reason the development of the WSSM wasn't a success due to the thick walls of the cases which resulted erratic pressures?
I have a 22-250 ackley and enjoy not having to trim cases since I do a lot of chuck hunting. The only problem I had with it was since I had a tight neck chamber I had to turn the necks before fire forming. I had to trim them to the same length before I turned the necks and after I fire formed them the cases had slight variations in length. I really didn't notice that much effect on accuracy.

Thanks Guys!! Happy Holidays!!
 
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