Thread: 35* long neck 7 SAUM based on WSM

Hi guys. Hopefully there are a few wildcat gurus that can share a little insight. Two things I like on case is a long neck and 35* shoulder.

I have been playing around with a few 7mm options. I had a good hard look at the 7mm LRC that Pro Martusheff developed, but based on my current position I had to scrap that option. I have also been playing around with the 284 and Shehane, as well as the 7-270wsm and SAUM and a few improved options. After being through the custom wildcat route with a 300 NM Imp, I also considered the issues around custom dies etc and the potential solutions I formulated included the following.

- take a 7mm or 300 WSM die,
- shorten the die to a length that will allow you,
- to push (SLR) the shoulder on the 7 RSAUM back from 30* to 35* and create a longer neck,
- blow the taper a little out to the same shoulder dia as a WSM
- and potentially use the shorter WSM die to size your brass?
- set up a reamer that will allow for this.

If this works and even if one needs to use a small base die to start with, you will be able to get roughly the same capacity as the straight RSAUM, but I think the 35* would make it a little more efficient, have a little less case growth, have a longer neck and you wouldn’t potentially need custom dies, although you would only size the upper part of the case. The image below shows the straight RSAUM as well as the 35* option based on CIP specs and not SAAMI.

In an attempt to bridge the gap between theory and practice, what do you guys think?

Far out, you are really down a rabbit hole there! Why go to such extremes. Is it to achieve a certain speed with a certain pill in a short action or are you just wanting something different? I would be interested to know.

Originally Posted by 300LRH

Hi guys. Hopefully there are a few wildcat gurus that can share a little insight. Two things I like on case is a long neck and 35* shoulder.

I have been playing around with a few 7mm options. I had a good hard look at the 7mm LRC that Pro Martusheff developed, but based on my current position I had to scrap that option. I have also been playing around with the 284 and Shehane, as well as the 7-270wsm and SAUM and a few improved options. After being through the custom wildcat route with a 300 NM Imp, I also considered the issues around custom dies etc and the potential solutions I formulated included the following.

- take a 7mm or 300 WSM die,
- shorten the die to a length that will allow you,
- to push (SLR) the shoulder on the 7 RSAUM back from 30* to 35* and create a longer neck,
- blow the taper a little out to the same shoulder dia as a WSM
- and potentially use the shorter WSM die to size your brass?
- set up a reamer that will allow for this.

If this works and even if one needs to use a small base die to start with, you will be able to get roughly the same capacity as the straight RSAUM, but I think the 35* would make it a little more efficient, have a little less case growth, have a longer neck and you wouldn’t potentially need custom dies, although you would only size the upper part of the case. The image below shows the straight RSAUM as well as the 35* option based on CIP specs and not SAAMI.

In an attempt to bridge the gap between theory and practice, what do you guys think?

I think you may find the WSM's have a slightly larger base size than the SAUM's. They were developed from two different cases in spite of what is written about them.
Grandpamac.

Just checked. Measured base size of a .270 WSM and 7 mm SAUM. The WSM is a little larger, about 0.1 mm or so. The SAUM works pretty well. Can't see you would gain much. The 5 degree increase in shoulder angle is unlikely to had any measurable effect other than a talking point. If you want to do it however why not?
Grandpamac.

Some of my interest in a improved version of the SAUM stems from the claimed improved performance of the Sherman Short Mag vs straight SAUM. My reason for chasing the extra performance is not to use it, but to increase barrel life. The improved performance will allow you to run the round at a lower pressure with less powder at the same node, which both contribute to longer barrel and case life. My experience is that a sharper shoulder angle leads to less brass flow. The combination of the shoulder and longer neck also pulls back the flame point back into the case neck. Bringing the shoulder neck intersection back also help with better bullet seating and contributes to shorter coal. The reason for the integration of the WSM will help with issue around custom dies.

Grandpamac, thank you for that insights. Would you mind sharing the dimensions and are those measured on FL sized or fired cases? Would mind sharing the dimensions for FL sized and fired case if you can.

Greetings 300LRH,
Both were unfired factory rounds. Unfortunately I didn't write them down so will remeasure tomorrow with the micrometer and report. In round numbers in the old measurements the WSM is about .550 inches and the SAUM .545 inches. The WSM is based on the .348 Win case and the SAUM on the 404 Jeffrey case. Will check tomorrow. This is the solid head of the case so should not change on firing, at least very little.
Grandpamac.

Greetings,
.270 WSM base measured 13.93 mm (0.5485 inches) and the 7 mm SAUM base measured 13.85 mm (0.5455 inches) for a difference of 0.08 mm (0.003 inches). There is a way that you could form a case without butchering a die. You can sit the case on top of the shell holder (using a .223 shell holder would be a good idea to make things more stable) and run the case into the die a little at a time until you get what you want. You will have to knock the case out of the die with a rod and a small hammer, a rod from a small calibre Lee Loader would be ideal. Obviously you will need to remove the decapping stem first.

I wouldn't expect to get extra velocity or lower pressure at the same velocity from the steeper shoulder. This is often claimed for wildcats with steeper shoulders but actual comparisons using pressure testing equipment have failed to show any improvement. Wildcatters discussing their creation often show as much objectivity as a man talking about a grandson who has been named after him. At best you will get 7 mm SAUM performance at 7 mm SAUM pressures or higher performance at higher pressures.
Regards Grandpamac.

What about just getting a Sherman reamer in the size you want and the dies directly from him? I'm sure that there could be a few interested in helping cover the costs of the reamer depending on what you decide on. I was thinking of doing a 6.5 SST for a while but now that I can get 6.5PRC brass made by ADG i'm going that way as it's easy.

I do have a few wildcat reamers but did quite a bit of research beforehand to make sure someone else had done the hard work and that dies were available. Both are Alex Wheeler spec reamers from JGS. One in 6mmBRA, with Whidden dies and the other in 300 Norma Mag Improved using Hornady custom dies. Both of these are load and shoot, with a fire formed case as a result. I was hoping to have the BRA up and running a month or 2 ago but stuff went missing over lock down...

I also have a 20 Tactical, which I size down 223 brass for, creating a roughly formed case that seems to produce very accurate rounds. I do have a couple hundred Lapua cases that I'm planning on reusing but also a heap of 223 brass that I'm not worried about picking up, if I do it's a bonus.

Originally Posted by grandpamac

Greetings,
.270 WSM base measured 13.93 mm (0.5485 inches) and the 7 mm SAUM base measured 13.85 mm (0.5455 inches) for a difference of 0.08 mm (0.003 inches). There is a way that you could form a case without butchering a die. You can sit the case on top of the shell holder (using a .223 shell holder would be a good idea to make things more stable) and run the case into the die a little at a time until you get what you want. You will have to knock the case out of the die with a rod and a small hammer, a rod from a small calibre Lee Loader would be ideal. Obviously you will need to remove the decapping stem first.

I wouldn't expect to get extra velocity or lower pressure at the same velocity from the steeper shoulder. This is often claimed for wildcats with steeper shoulders but actual comparisons using pressure testing equipment have failed to show any improvement. Wildcatters discussing their creation often show as much objectivity as a man talking about a grandson who has been named after him. At best you will get 7 mm SAUM performance at 7 mm SAUM pressures or higher performance at higher pressures.
Regards Grandpamac.

Thank you grandpamac. The plan is do butcher/shorten the die, if I can get a cheap one somewhere. Based on your measurement around the base, the measurement from the shoulder down could even be closer. I think a lot of the wildcat gains is a result of increased case capacity, but I think a shoulder angle do contribute to the efficiency of a case. This is partially based on my understanding and experience in water and pump design and friction losses etc. The way I see it is that a flatter shoulder helps with the ignition, but that a sharper shoulder helps with the pressure flow. Or at least that is theory.

Originally Posted by The Claw

What about just getting a Sherman reamer in the size you want and the dies directly from him? I'm sure that there could be a few interested in helping cover the costs of the reamer depending on what you decide on. I was thinking of doing a 6.5 SST for a while but now that I can get 6.5PRC brass made by ADG i'm going that way as it's easy.

I do have a few wildcat reamers but did quite a bit of research beforehand to make sure someone else had done the hard work and that dies were available. Both are Alex Wheeler spec reamers from JGS. One in 6mmBRA, with Whidden dies and the other in 300 Norma Mag Improved using Hornady custom dies. Both of these are load and shoot, with a fire formed case as a result. I was hoping to have the BRA up and running a month or 2 ago but stuff went missing over lock down...

I also have a 20 Tactical, which I size down 223 brass for, creating a roughly formed case that seems to produce very accurate rounds. I do have a couple hundred Lapua cases that I'm planning on reusing but also a heap of 223 brass that I'm not worried about picking up, if I do it's a bonus.

The Claw, had a look at the sherman mags but decided against them. Also did a 300 NM Imp from scratch and learned a lot. So yes I'm trying to do as much as possible research and testing. Got some SAUM brass for a start. The first test would be to try and identify the challenges associated with forming the brass and if a shortened 7 wsm die can work.

I'd be interested to hear what you learnt from your 300NMI build that could benefit me, in saying that I have everything ordered now so probably not a lot I can do to change the outcome...

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The other thought I had was to look at the 7mmLRM. It's a long action round, but has a long neck and a reasonably improved case design already. Shortening it could be feasible?

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What about putting a steeper shoulder on the 7mm Blaser Magnum? Could also neck down to 6.5??

Have you read Greg Duleys article on the 7mm Fatso ?

Originally Posted by Moa Hunter

Have you read Greg Duleys article on the 7mm Fatso ?

The 7mm BM is not far behind the 7mm Fatso velocity wise. I am not sure the benefits of a short action outweigh the amount of time spent on pissing around with brass to form the Fatso. But that's just me - I find brass prep to be a chore