Here's the good oil on the 7mm Walker straight from the horse's mouth :
Mark Walker in Tx wrote:Hey Guys,
.284 Lapua brass as the native, shoulder is blown out .009-.010 depending on your starting .284 print (I started with a "Lapua 284 Match" print). Shoulder angle is 40° as Steve notes, and then the base of the case body is reduced about .0015 from same .284 print.
I been shooting this case since fall of 2010 and it seems to shoot ok. I'm on my 8th barrel now, normally get 2k rounds of barrel life or so. Case seems to be pretty easy to tune, and provides for a wide tune window. Lodi to Raton to Phoenix, or home here in Houston, has not seemed to matter.
Some barrels have wanted to run the same speed as a straight .284, about 2820, to shoot their best, some have wanted to run up to about 2920. I'll take what they give me, won't try to force a certain velocity on one, most run in the middle as you'd expect, 2870 or so.
At 2820-2870, primer pockets are not an issue as your not running the brass hard with the extra capacity. (One of the main reasons I developed the case.) Get up to 2920-2950, they start to get loose and I'll trash them after a few (4-5) firings. I mean, they will hold a primer but I won't take them to a FCNC or the Berger.
I have a print but can't seem to find a digital copy, I'll keep looking.
Whidden and Neil Jones have made dies for folks, and can make a set for anyone interested. I use both and both work well. Whidden's made most of the sets recently, fwiw. PT&G is where the reamers came from, Kiff and I spent quite a bit of time working out the #s - great guy if you have not worked with him. Nothing is proprietary, have at it!
Yeah interesting equipment list. Seems like they mention over 20 rifles and I wondered if that was from 20 potential members of the team or the 8 (is it 8?) Actual members of the team having multiple rifles?
The walker looks like a promising thing. Would think it would end up having a touch more capacity than the shehane because of the 40deg shoulder?
BATattack wrote:Yeah interesting equipment list. Seems like they mention over 20 rifles and I wondered if that was from 20 potential members of the team or the 8 (is it 8?) Actual members of the team having multiple rifles?
The walker looks like a promising thing. Would think it would end up having a touch more capacity than the shehane because of the 40deg shoulder?
I would think yes, but hardly enough to matter. The Shehane only holds about 2 grains more than the 284. And it looks like he has exactly the same problem as we do with brass. If this Bertram brass works it'll be a big plus for all the 284-based chamberings.
I looked at a 284AI with 40 degree shoulder (practically a 7mm walker) a while back when I had done a barrel in 284 shehane and it failed to impress. In the end to me it was too much running around doing fancy things with fancy dies so I did another shehane to try and get it right before trying something else. I dont think there will be any benefit of a 7mm walker over the shehane- until dies are as easy to get ahold of at least.
There is another possible option. If the Aussie .284 win brass project goes ahead, there may be a chance to make "Long .284 brass". I have seen this done with other brass recently and the amount of case capacity can be increased quite a bit. Much more than the 2 grains that the Shehane gives. This larger increase in case capacity, could increase the performance level up to that of the 7mm SAUM. Imaging a .284 win with an extra 0.100" or so of actual body length! With this option the shoulder angle stays the same so that the original dies can be used to reload the cases. So no extra dies are needed. This is a bit like using 6mmBR dies to load for the 6mm BRX. When the chamber is cut the reamer simply goes in further to match the "long .284 brass" length. This may make the base area of the chamber slightly wider so there is a limit to how long the chamber can be cut with a standard reamer. Ideally a custom reamer would be made to suit the dimensions of the longer brass and so maintain a tight fit down near the cartridge base. If the body is made too long, you may need to make a FL die to size the case base as the standard dies may not size this area enough. The cartridge neck length stays the same as the case is trimmed after forming to a longer overall length.
Norm would it be worth just going to the 280ai? That seems to be a really well balanced case. It's not rebated head like a 284 but it runs close to the SAUM and wouldn't need custom dies/ reamer and you can buy brass off the shelf?
I'm keen to see what happens with the bertram brass. I hope it goes well as it would make it an easy way for new shooters to get behind a really competitive caliber from the word go. just load and shoot with 0 Forming required!
BATattack wrote:Norm would it be worth just going to the 280ai? That seems to be a really well balanced case. It's not rebated head like a 284 but it runs close to the SAUM and wouldn't need custom dies/ reamer and you can buy brass off the shelf?
I'm keen to see what happens with the bertram brass. I hope it goes well as it would make it an easy way for new shooters to get behind a really competitive caliber from the word go. just load and shoot with 0 Forming required!
I agree there are other options. I can think of quite a few, but the discussion was about variations and improvements to the basic .284 Winchester case to Shehane etc. people like to play with different things so I guess they will always look for the best. What ever that may be. I know of someone who is looking to do something very interesting with the .284 case but that is not public knowledge so I can't say much. Still hard to beat the straight .284 and I think I will stick with it for a while yet.
BATattack wrote:...would it be worth just going to the 280ai? ...
Adam,
A few have tried the 280ai, but I can't think of anyone who has had a lot of success. I get the impression they're harder to tune than a 284 - could be the long thin powder column? Nearly all cases with short fat powder columns e.g. 6BR and 7 RSAUM, seem to be easy to tune. The 284 is somewhere in the middle in that respect.
Didn't matt paroz do quite well with one? Shot some 60s with high X counts?
There are a few down this way that seem to shoot really well! I think the SA long range team won the nationals with most using them. At this stage not a lot of those shooters have traveled and shot side by side 284s in bigger events but I think they can be competitive given equal shooter/ tuner ability and even numbers at big events.
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