7mm SAUM Wildcat!

[redneckclimbing]

Just got the dies today. I'm having a little trouble with the Win. brass but I thnk that an annealing will help. Going to try it tomorrow. I will weigh some cases and get some actual capacities.
Even with the worst case scenario, the GT doesn't look terrible, although maybe ot worth it with SAUM numbers being so good. Also, I was reading in P.O. Ackley's book that straightening out the body of the case will allow you o safely shoot hgher pressures becaue of the way that the case grips the walll of the chamber.
With that said I don't know what would be considered a "safe" pressure to put into our calculations. Anyways, thanks alot, there is a ton of great info. there. I will try and get some cases made up tmw. and get some actual capacities posted.

Travis

[calinb]

Originally Posted by redneckclimbing

Just got the dies today. I'm having a little trouble with the Win. brass but I thnk that an annealing will help. Going to try it tomorrow. I will weigh some cases and get some actual capacities.
Even with the worst case scenario, the GT doesn't look terrible, although maybe ot worth it with SAUM numbers being so good. Also, I was reading in P.O. Ackley's book that straightening out the body of the case will allow you o safely shoot hgher pressures becaue of the way that the case grips the walll of the chamber.
With that said I don't know what would be considered a "safe" pressure to put into our calculations. Anyways, thanks alot, there is a ton of great info. there. I will try and get some cases made up tmw. and get some actual capacities posted.

Travis

Yeah--maybe straighten out the GT case a bit more. The taper is currently .0085" / inch but the 7 WSM is even less at .0058" / inch! Using the straighter WSM taper would bump the case capacity up to about 65 grains.

When you measure the cases, could be please give me the weight of the brass too, Travis?

Thanks,

-Cal

Edit: The increase in GT case capacity realized with the straighter .0058 taper only provides about a 10 fps improvement, at max velocity (N560) for COAL=2.985. Running at 65,000 PSI yields only about another 5 fps. Straighter walls help out more with COAL=2.840, especially with the bulkier powders like N560 and RL-22, which are limited by the 105% max. fill ratio. (More like 20-30 fps) improvement.

[redneckclimbing]

All right, here's an update. I got the dies from Mark Spencer just as Mr. Spanner did. They worked very well even to put a 40' shoulder on my cases. Can't say enough about Mark, really professional and my dies work very well. I did have to anneal the brass, but I was using regular Win. and not Norma which Mark had recommended.
Next, I got some cases made up, but have not yet trimmed or neck turned them yet. (Will post pics. ASAP.) took a couple and ground off the neck to measure the "real" case capacity. Got 63.25 grains of H2O. This is virtually identical when compared to a Shehane when you subtract the neck.

(I used 252.360039 grains of H2O / in.3 as per Quik Load)

Here are some other "real" capacities if anyone is interested:
7mm-08 51.3 (calculated)
.284 Win. 60.4 (calculated)
7mm GT 63.3 (measured with shortened case)
Shehane 63.7 (calculated)
.280 rem. 64.4 (measured with shortened case)
7 SAUM AI 68.1 (measured with shortened case)
7 SAUM 68.6 (calculated)
7 WSM 77.1 (calculated)
7 rem. mag 81.8 (measured with shortened case)

(With the SAUM AI I held the dies off of the ram to make the head space the same, but with a 40' shoulder. With all "measured with shortened case" I ground the necks off and measure the cases dry and then full of water.)

So, my thoughts so far are that my original criteria for the GT should be met. Might even do a little better then the Shehane, due to more efficient case design. Or maybe the same performance with a shorter barrel. Either way, I am definitely going to get a reamer print finalized and sent off to Mr. Kiff and see what happens! I'll keep you updated!

Travis

Also, on a side note, I'm going to put together a chart of cartridge "efficiencies" of some of the "Acklies" and what ever else I can find actual capacities for. It will just be sorted out as velocity / grain of powder for the fastest load I can find for that cartridge. (or something like that anyways) Will post when finished.

Cal- I am going to try to get to a friends that is totally set up for reloading, (case trimmers and all the prep. equipment) when I get some case finished and trimmed I will let you know right now they are still the same as the original WSM, about 320 grains or so.

[calinb]

Originally Posted by redneckclimbing

(I used 252.360039 grains of H2O / in.3 as per Quik Load)

7mm GT 63.3 (measured with shortened case)

Cal- I am going to try to get to a friends that is totally set up for reloading, (case trimmers and all the prep. equipment) when I get some case finished and trimmed I will let you know right now they are still the same as the original WSM, about 320 grains or so.

Great progress! Looks like my higher-confidence 63.9 grain estimate was pretty close--especially not knowing the brass weight. Now I realize I could've just extrapolated the GT weight from the WSM weight.

I usually use my electronic reloading scale to measure water capacity. Zero the scale with the empty brass resting on it and then just fill the brass with water and weight it.

[redneckclimbing]

So, if anyone is interested, here are the "efficiency" ratings that I found for some various 7mm cartridges. The idea, only a marginal representation, was to find the most efficient case capacity of a 7mm cartridge.

The numbers listed below are the velocity (in ft./sec.) divided by the grains of powder it took to make said velocity. Ratings were given from the fastest load that could be found from reliable sources a.k.a. published reloading data. (Most of the calibers were found on the Nosler reloading web-site so as to give more consistency to the numbers).

All cartridges, unless otherwise noted, were loaded with a 175gr. bullet. Here we go:

7mm BR (w/ 150 gr. bullet) 39 / 87.8
7mm-08 51.3 / 59.2
7x57 55.6 / 62.5
7x57 AI 57 / 58.7
7x64 Brenneke (w/ 160gr. bullet) 62.6 / 45.3
.284 Win. 60.4 / 52.2
.284 Shehane 63.7 / 55.1
.280 Rem. 64.4 / 50.2
.280 Rem. AI 67.6 / 49.1
7mm SAUM 68.1 / 48.3
Lazzerroni Tomahawk 71.2 / 47.9
7mm WSM 77.1 / 49.6
7mm Rem. Mag. 81.8 / 43.5
7mm Weatherby Mag. 82.2 / 43.6
7mm STW 88.9 / 42.6
7mm RUM 106.4 / 34.4
Lazzerroni Firebird (w/ 160gr. bullet) 124.4 / 38.3
Wade Super Seven Mag. Case / 47.0
7mm Gradle Mag. Case / 50.4
7mm Ackley Magnum Mag. Case / 49.2
.284 Durham Magnum Mag. Case / 50.3

7mm GT (from Quikload estimates) 63.3 / 54.9

The first number is the powder capacity in grains of water and the second number is the efficiency as stated previously. The "Mag. Case" cartridges are wildcats form P.O. Ackley's reloading manual vol. 1 so I don't know what the exact volume are. However, they are all made with belted H&H brass or something similar, and are left fairly long therefore they will have larger case capacities.

I know that this is not a complete study in that it doesn't account for all the different loads listed, or "accuracy loads" that could possibly shoot a little faster but, I think it gives a good general representation.

What I am seeing out of this is that with the 7mm bore shooting a 175. gr. bullet the ideal powder capacity (translating into, efficiencey and barrel life) is somewhere between 60-64 grains of capacity.

The only major deviant from this is the 7x64. I don't know if this is due to the 160gr. bullet or something else as I did not put a rediculous amount of time into researching loads. But there it is interpret it how you will.

Travis

[redneckclimbing]

Here is a pic. of a "dummy round". Now that is what I call "PURTY"!

[calinb]

Originally Posted by redneckclimbing

Here is a pic. of a "dummy round". Now that is what I call "PURTY"!

Nice work! I think efficiency mostly comes down to matching the case capacity to the job--at least at Quickload levels of prediction.

I have a couple of Ruger RCMs--the 300 and 338 (and a lifetime supply of brass and ammo, though Steve Hornady told me the RCM will not be orphaned). The RCM is more efficient than the 300 and 338 Win Mag because the RCM case capacity is lower. Another benefit is it shoots well from short barrels. With a few loads the Win Mag is faster, but it's less efficient.