Take a look at the B5 Systems BRAVO SOPMOD stock, a little lighter than the original SOPMOD stock but have similar shape and size buttpad.
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I have 2 of these I got several years ago ... a gen1 and a gen2 (black). Thinking about switching them for something a little lighter.
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I have this B5 Systems Bravo stock which I replaced my wider and heavier Vltor IMOD stock, it is also narrower but not too narrow like the standard M4 waffle USGI stock.
The Bravo stock also have a non rotational QD sling attachment and I prefer it than my other Magpul CTR and MOE stocks.
If you wanted something even lighter than the Bravo stock the Magpul CTR and MOE stocks are lighter, the CTR have a friction lock that minimizes or eliminates wobble from the buffer tube and it have a QD sling mount.
The MOE stock doesn't have the friction lock and no QD sling mount, but the MOE would be one of the lighter full size stocks currently available in the market.
Ref:
http://b5systems.com