7mm SUAM Wildcat!

[redneckclimbing]

Hey Everyone-

I am going to build a long range hunting rifle in some sort of 7mm. I am set on components: Lawton 7000 SA, 30" Kreiger 1-9 twist, AI stock. My dilemma comes with the 7SAUM and loading 180 Berger's long. (I want to use an AI stock and magazines and obviously they won't work this way.)
I had also noticed that a .284 Shehane will do basically the same velocities but is even a tad longer when loaded long. This got me thinking wildcat. My idea was to take the proportions of a 6mm Dasher and push them out to a SAUM case.
When I did these calcs. I found some interesting things:
- This gave me almost identical volumes to a .284 Shehane
- The start of the shoulder was only slightly shorter than a standard SAUM

So, I thought why reinvent the wheel? Keep the lower (below the shoulder) part of the case the same, and put a 40' shoulder on it. With this combination it should have a slightly larger capacity than the Shehane but not much. This smaller volume should be more efficient than the SAUM or WSM. I am hoping that with about 56 grains of H4831sc it will consistently reach the 3000-3050 fps velocity node.

Advantages:

- This will easily fit into an AI mag. with a 180 Berger loaded long
- with the 40' shoulder I think that t will give slightly better vels. with similar charges as the Shehane
- With a similar powder load to the Shehane I was thinking that the barrel life should be similar (everything else being the same).

I have drawn up a reamer for Mr. Kiff but am needing some suggestions on some things I didn't really know. (the question marks on the print) I was also wondering if someone could run this through QUICK LOAD and see what it spits out.

I also have not had a chance to measure any bullets yet so if anyone knows the bearing surface lengths of some bullets and could post them that would be great so that I can finalize the freebore length. As you may notice this is basically a SAAMI chamber with a 40' shoulder and a slightly tighter neck.

Please let me know what you think!

Here is a copy of what I have so far.

 

[redneckclimbing]

Also, I forgto to mention that the body has been shortened .100 this should give a COAL of 2.80" and about 67.5 grains of H2O capacity. Almost identical to the Shehane.

 

[redneckclimbing]

Sooo, I thought why not straighten out the case a bit? This reamer would give the same body taper as a WSM and add about a 1.5 grain of H2O cap. Has anyone had any problems extracting their WSM's or does anyone think this could cause a problem?

 

[alf]

A couple of questions.

Don't the AI mags run a 2.995" OAL?

If so, where does the 180 sit in a regular SAUM loaded to that dimension?

With the powders currently used for the SAUM, where does the max load come up to in the case, in relation to the bullet base seated? Meaning, if the powder capacity doesn't impede on the bullet seating, why re-invent the wheel?

 

[lurcher]

I went a different way and bumped the shoulder on a saum down 200 thou.

case capacity is 62.5 -63 grains of water so I'd say your predictions on case capacity are close. With a 162 amax seated to within 20 thou of the lands I have a OAL tip to toe of 2.8 exact.

 

[wildchild]

I went a different way and bumped the shoulder on a saum down 200 thou.

case capacity is 62.5 -63 grains of water so I'd say your predictions on case capacity are close. With a 162 amax seated to within 20 thou of the lands I have a OAL tip to toe of 2.8 exact.

Thats kinda sexy ;D ;D Could we see a bullet in it for full effect viewing? Whats velocity and hows it shooting?

 

[redneckclimbing]

Wildchild-

I saw your post when I was looking to see if anyone had done something similar. Idefenitely used your capacity as a reference for figuring out this capacity.
I was also curious what kind of velocities you are getting with that thing. I was hoping the little more capacity and the 40' shoulder would help up the velocity.


My understanding is that AI magazines are 2.90" but I have not measured one myself.


I do not know where the powder fills up to in the SAUM case (I am assuming you are refering to loading it shorter?).


The main idea that I had was that using 7 or 8 grains less powder and still getting the same velocities, it would have less felt recoil (for F-Class and 1k benchrest guys) and also maybe have the barrel life of a Shehane (reportedly around 3000+ rounds) as opposed to a SAUM (reportedly round 1500+) or the WSM somehwere between 700 and 1500.

 

[redneckclimbing]

A 180 Berger "loaded long" (top of the "tail" at the bottom of the neck) is approx. 3.02" in the SAUM, 3.16" in the WSM, and 3.19" in the .284.

 

[skyking]

I end up doing something almost the same . I did a 35* shoulder on my saum. Did it in a short action. Also have a friend from on Snipershide doing a 40* saum right now.
My goal was to push the Berger 168 faster then the benefits of the 180. Leave more room in the case, then seating the 180 deep. Also got 40 fps faster meloniting my barrel.

http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=2961029&page=1

 

[wildchild]

I have a wildcat based off 300WSM Norma Brass run in a 7mm SAUM Die to push the shoulder back to SAUM headspace and gives a nice long neck, guess one could do the same and keep it a 30 cal. Dies would be easy.

 

[redneckclimbing]

Skyking what is your COAL? And are you running out of room in the case to seat the 180 deeper?

Also that meloniting treatment looks pretty interesting! Keep us posted on where you settle out with your load development.

 

[redneckclimbing]

Well, I've got a 1-9" twist Broughton on the way and a resizing die from Spencer Tool & Grind on the way! It is going to have a 35' shoulder for now. Going to check the case cap. and then will have a reamer made from a "dummy" round. Getting pretty excited now, I will let everyone know how it comes along.

 

[Spanners]

I went a different way and bumped the shoulder on a saum down 200 thou.

case capacity is 62.5 -63 grains of water so I'd say your predictions on case capacity are close. With a 162 amax seated to within 20 thou of the lands I have a OAL tip to toe of 2.8 exact.

Whos dies are those?

I'd like to do the same thing with a 284 - get it to mag length with proj seated correctly in the case

 

[Erik Cortina]

Spanners, the dies are from Mark Spencer at www.spencertoolandgrind.com

He made me a die also and it is awesome! Very high quality.

 

[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.

 

[JohnMill]

Ammoguide dot com has all the capacities, plus diagrams so you can figure the taper per inch per side (I think that figured into Ackley's form). Save you some legwork.

John

 

[redneckclimbing]

Mr. Mill-

It definitely did factor into his designs, it states in his reloading manual (that I just got the other day) .0085in / in. is the taper he used. I found it interesting that he says this not only makes brass last longer due to less stretching, but makes extraction easier, because the case does not become "wedged" in the chamber. Pretty interesting!

 

[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 website 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, efficiency and barrel life) is somewhere between 60-64 grains of capacity! ;D



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 ridiculous amount of time into researching loads. But there it is interpret it how you will.



Travis 8)​

 

[redneckclimbing]

Hey everyone-

A quick update: Sooo, some things have changed. I am going to be going with a blue printed 700 action. (Bought an SPS in .300 WSM). I have a Broughton barrel (Kreiger has a long wait list), Badger recoil lug and picitanny scope base. Going to put all of this into a Manner's T2 stock with the M-5 bottom metal from Stocky's. They had McMillan's in as well but they were inletted for the BDL and I did not want to fart around with inletting the bottom metal and I definitely wanted to have a DBM set up. I am really hoping that this whole set up topped off with a Leupold Mark IV will come in under 12#.
The plan as of right now is to start putting it all together the first week of June. This should be good as I have a Mountain Goat tag burning a hole in my pocket already for the beginning of Sept. and I really want to shoot it with this rifle.
I will let you know how the velocities pan out as soon as possible.

 

[redneckclimbing]

Forgot to mention, the case capacity filled up to the shoulder (not the top of the neck) came out to 63.25 grains of H2O. I think that this will go up just slightly after fire forming as the bottom of the case is not even being sized at all yet by the die. This is almost exactly the same as the .284 Shehane so that is encouraging, I think.