I have two 338 Ultra Gen 1s. One of them is used exclusively on 6.5CMs, the other gets used on 300 and 338NM, 338LM, and 300PRC. They are amazingly quiet on the 6.5s. For my type of shooting (square range/ELR) the extra length and weight are a non-issue. The reason I dedicate the one for just 6.5s is because if I switch around between rifles, the magnum rifles will knock loose carbon build-up inside the can that accumulates from the 6.5s. When I only had the one can and switched around, I'd shoot mostly 6.5 in the winter when my range was too wet/muddy to access the ELR portion, so I'd shoot the winter months with the 6.5s at 1000-1200 yds. When the range got dry enough in late Spring to go out to the extended distance for the magnums, they'd knock loose carbon that had built up inside the can from the 6.5s during the winter. Take the can off and black crumbly stuff would fall out. It's not really a problem, it just bugged me. Now I have two, and as long as one stays on 6.5s, that doesn't happen, and neither does it happen on the other that stays on the big guns all the time. Again, this isn't a real problem, it just bugged me. I'm considering getting a third one, a Gen 2 SR.