How would you compare the MPI or Rock Rim to McMillan.
I've used Brown Precision, the now defunct Garrett Accu-lite, Basner, HS, and B&C. Brown and Garrett made good quality stocks, but are more costly than McMillan and are usually not true bolt on like B&C and McMillan.
If you don't mind the extra weight of the B&C and HS they shoot well. While HS is a good stock it is $100+ more than B&C and doesn't seem to offer a single advantage that I can see. At least none over the B&C Medalist stocks. Their Carbelite and Ti stocks with no bedding block are junk.
I've used one of the Bansner stocks. They offer the cheapest way into a light stock if you don't mind doing the final fitting and finish work. They list their weights with no recoil pad, so the finished stock with a pad is not really that light unless you go with a flip-flop pad. By the time I purchased the materials to finish and paid to have it bedded, it ended up about the same price as a McMillan. Would have been more expensive and weighed more had I not opted for the flip-flop pad.
Never really looked at Rock Rim, but have researched MPI. No doubt they are good stocks, but to get a 20 oz. stock from them would be an unfinished stock blank and only around $50-$60 less than a completely finished McMillan ready to bolt to my gun. It is not clear if that 20 oz. stock includes a pad or not. If not add $40 more to the cost and 4-6 oz. more weight.
Three of my 4 McMillans were purchased used and to get a 20 oz. lightweight stock were the cheapest route I've found. Mine have all been simply bolted to the guns with no bedding and all shoot sub MOA, some very close to 1/2MOA.
Not trying to sound like an advertisement for McMillan, but for the money they are the best bargain I've found for a quality lightweight stock. The B&C Medalists shoot as good as anything and are my choice if weight is not an issue. But weight is an issue on on most of my rifles. I'm open to other options partly because I'm debating on which stock to put on my newest project. I'm on the lookout for another used McMillan Edge for a short action Winchester, but if one doesn't turn up soon I'll have to pay for a new one.