A while back I built a mag fed rifle in 7mm WSM and I've been using it in local precision rifle competitions. The 7WSM is a great round and has nearly optimum ballistics for the limitations of a short action, but it seems to be a bit overkill for the relatively short ranges found in these matches. I posted on this idea with some supporting data in my build thread:
http://www.snipershide.com/shooting...e-7-wsm-build-now-new-barrel.html#post2311421
This led to the idea of just using a shorter case to reduce capacity for cost purposes while using the same bolt face, same bullets, same magazines, etc. The 7mm WSSM is not a new idea, but most of the info I was able to find on it is related to gas guns. Anyway, this seemed like it might have potential as the "toned" down WSM I had in mind, plus I like to experiment; so reamers, brass, and parts were ordered... I think we all know the state of this hobby, so I'll skip ahead a number of months:
Everyone likes pictures so this picture shows the 7mm WSSM next to a few other long range rounds for comparison: the 7mm WSM loaded to mag length, the 7WSM loaded for F-class (single shot), and a 338/300RUM. The 7WSSM is roughly equivalent to the 7mm-08, though with its short case long/heavy bullets can be seated out to preserve case capacity. Enough parts finally arrived to test the theory, and now with a barrel swap I'm getting up to 2850fps with the same 180 grain SMK (superformance powder). Pressure is moderate to low so cases should last and extraction is easy for fast/smooth bolt movement (helpful in most timed stages). Eventually I'd like to test the 162 hornady bullet. Depending on what velocity I can get it may have an edge over the 180 for short range, but I already have a bunch of the 180s. I'm thinking the 162 with H4350 will be a good combination to try, if I can eventually get the components.
Accuracy so far is acceptable, but not great (1.5" at 200yards). For availability I've been using 223 WSSM brass, and its quality is not very good. So far I've just been annealing the necks and expanding them to 7mm. Because the 7WSSM is basically a 6mm PPC scaled up slightly, I was hoping to get effortless accuracy without messing around with brass. With more brass prep (turning necks, trimming to same length, sorting, etc.) I think accuracy will improve significantly. I would also like to try some 25 WSSM brass to see if there is better quality there (does anyone want to trade some for 223WSSM brass?).
The reamer was spec'd such that my WSM reamer can be simply run in to clean out the WSSM chamber if desired, but so far the experiment is looking like a success. I'll post updates as I get more experience with it...
http://www.snipershide.com/shooting...e-7-wsm-build-now-new-barrel.html#post2311421
This led to the idea of just using a shorter case to reduce capacity for cost purposes while using the same bolt face, same bullets, same magazines, etc. The 7mm WSSM is not a new idea, but most of the info I was able to find on it is related to gas guns. Anyway, this seemed like it might have potential as the "toned" down WSM I had in mind, plus I like to experiment; so reamers, brass, and parts were ordered... I think we all know the state of this hobby, so I'll skip ahead a number of months:
Everyone likes pictures so this picture shows the 7mm WSSM next to a few other long range rounds for comparison: the 7mm WSM loaded to mag length, the 7WSM loaded for F-class (single shot), and a 338/300RUM. The 7WSSM is roughly equivalent to the 7mm-08, though with its short case long/heavy bullets can be seated out to preserve case capacity. Enough parts finally arrived to test the theory, and now with a barrel swap I'm getting up to 2850fps with the same 180 grain SMK (superformance powder). Pressure is moderate to low so cases should last and extraction is easy for fast/smooth bolt movement (helpful in most timed stages). Eventually I'd like to test the 162 hornady bullet. Depending on what velocity I can get it may have an edge over the 180 for short range, but I already have a bunch of the 180s. I'm thinking the 162 with H4350 will be a good combination to try, if I can eventually get the components.
Accuracy so far is acceptable, but not great (1.5" at 200yards). For availability I've been using 223 WSSM brass, and its quality is not very good. So far I've just been annealing the necks and expanding them to 7mm. Because the 7WSSM is basically a 6mm PPC scaled up slightly, I was hoping to get effortless accuracy without messing around with brass. With more brass prep (turning necks, trimming to same length, sorting, etc.) I think accuracy will improve significantly. I would also like to try some 25 WSSM brass to see if there is better quality there (does anyone want to trade some for 223WSSM brass?).
The reamer was spec'd such that my WSM reamer can be simply run in to clean out the WSSM chamber if desired, but so far the experiment is looking like a success. I'll post updates as I get more experience with it...
