Improved 7 SAUM

[Evlshnngns]

ADG is supposedly coming out with 7 saum brass.

 

[TZaun]

Have any of you tried Bertram 7 SAUM brass? I have some 6.5 SAUM ordered but don't have it yet.

I just necked down 300 RSAUM Bertram brass for my 7 RSAUM, loaded up 9, and shot them. I weighed each case before filling with water. Case lengths are all within .003" after firing, and they all stayed the same. They all measured 2.002" to 2.005" before and after firing. The shoulders are blown out to within .0005" of each other. They all moved out right around .005". QL had told me that 57.6 gr. N160 would give me 2820 fps with a 180 Scenar jammed .020" to help get a good fire formed case. My LabRadar said they averaged 2917 fps. I have a brand new 30" Bartlein 9-twist on it. This lot of N160 was really fast in a 6.5-284 that I used to shoot, too. I'll tone it down a bunch for this first firing. Here's the case weights on the 9 as measured on my A&D 120:

74.92/216.02
75.06/216.92
75.08/216.64
75.12/216.56
75.12/216.36
75.22/215.04
75.22/214.98
75.32/214.56
75.44/213.40

My Norma 7 RSAUM brass had an average of 74.1 gr. H2O internal volume. This Bertram 300 RSAUM brass is going to be just under 75.2 gr. H2O. Just a very limited sample size so that's all I have for info on it so far. I plan to run it this summer for 1,000 yard F-Class.

 

[Laurie]

QL had told me that 57.6 gr. N160 would give me 2820 fps with a 180 Scenar jammed .020" to help get a good fire formed case. My LabRadar said they averaged 2917 fps.

I believe QL's default values for N160 are way out. I never trust the program with initial loads until I see actual results when it is the first time out with that barrel / cartridge. So, for a 60,000 psi cartridge say where I want an ultimate load running at maybe a little less pressure, I use QL's load prediction for 52-53,000 psi as my top initial charge weight - and while the occasional time sees actuals close to predictions, actuals at 100 fps or so above what's predicted are much more common. QL is also way out on the default loads density usually overstating the fill-ratio significantly. (I run a number of N160 loads with mild to moderate compression that are 110-115% fill-ratio according to the program.)

I suspect this is one reason why recent loads data from bullet makers and others hardly ever include this powder these days. As all manufacturers now use QL in their initial assessment to choose likely powders to try out, N160 comes over as a poor performer in many applications being predicted to produce feeble pressures and MV when at 100% fill at a SAAMI COAL. For instance on the basis of QuickLOAD defaults, nobody would ever use this powder with 140 gn bullets in 260 Rem and 100% F/R is reached at just over 41gn. Yet, a near standard UK load for N160 and a range of 140gn tangent ogive models at a little more than SAAMI COALs (throats and AI magazines usually allowing 2.85" COALs) is 44gn that combines reasonable performance with equally acceptable barrel life. In an initial test I did recently in a 28-inch barrel long-throat 260 (~2.95 COALs for most such bullets), actual MVs were well above predictions even after adjusting case capacity to the actual values for fireformed brass which are well above the program's very low default capacity value.

Prediction for 55.6gn case water capacity (actual - QL default = 53gn); 2.935" COAL; 140gn Berger BT; 28-inch barrel:

44.5gn N160 ........... 101.4% fill-ratio; 49,106 psi PMax; 2,707 fps MV

Actual for 44.5gn: less than full case / no compression; 2,823 fps MV (Labradar)

To achieve that actual 2,823 MV in QL, the charge used in modeling has to be raised for this combination by a full 2gn to 46.5 which as well as now predicting correct MV says 56,378 psi and 106% fill-ratio. To get to the full SAAMI 60,000 psi PMax takes another grain nearly in the model at 47.4gn with a predicted f/r of 108%.

Actual results would say that 45gn is tops with this particular brass / chamber / COAL.

 

[TZaun]

I agree 100% Laurie.

I don't have a good way to measure out the density yet. I'm working on something as we speak.

I just adjust Ba rate for now to get me fairly close. Changing it to .527 gets my velocity to line up. Not the correct way, but it's something. I just want a fire form load down around 55,000 psi. Sounds like there's something to laying off the gas on the brass's first firing to toughen up the primer pockets??

Glad to hear it's not just my N160 that QL doesn't even come close to modeling correctly, with the factory defaults.

 

[Capt. Oblivious]

N160 in my SLR and QL does the same thing. Its the one powder I just cant “predict” the results

 

[RustyPin]

I had a bunch of "spare parts" laying around so I took a Bartlien barrel and ran a 7WSM reamer in .177" short and set headspace with a RSAUM gauge. I pushed the neck and throat out to fit the RSAUM case and fireformed it. I shortened some RCBS dies to size/load the cases. I am working with naked 168 Bergers and Retumbo at the moment. I have 3 loads on the original 50 Norma cases I had and still have nice tight primer pockets. Running right at 3000 with no pressure and accuracy is really good. This will be my LR hunting rifle when I get a heavy sporter barrel ready to roll. I am sure that there are a lot of people who do not think the gains are worth the work but it is what I had so I made it work.

David

David, can you proved Base Measurements after Fire-Forming? I was pondering this WSM'd version in 6.5 SAUM. Only it seems the Reamer is too Wide at the Base.

 

[ben_g]

In my limited experience with a 300WSM that’s what I would keep shooting.

Only reason I also have a SAUM barrel is restrictive muzzle energy limits in some states in Australia.

 

[David L]

Amen Brother,
I agree 100% with the brass prep, but I'm not so sure its the shoulder angle. It could also be that Norma brass is softer that the Lapua brass. I sure would like to have more brass options. A choice between Norma and nothing is not much of a choice. Maybe Alpha or Petersen will get into it and give us more options.

Joe

https://atlasdg.com/product/7mm-saum/

 

[JeffT]

Jim Murphy has shot a 7rsaum improved for years.

 

[wedgy]

Have you looked at any of the Sherman Shorts ?
https://shermanwildcatcartridges.com/7-ss
https://shermanwildcatcartridges.com/7-ss-max