I own a sandman S and K, and use them on an 11.5, 13.7, and 16" gun. As would be common sense, the weight of the cans is exacerbated as the barrel length is increased. My current set-up that I use for almost everything is a 13.7" 5.56 with the sandman-K attached. This is ideal for me as I get a acceptable amount of forend to hold the gun like I want to, enough barrel to keep velocity up, while not being as long as a 16" gun. The K works very well as a can to take the edge off of the noise. I have shot it indoors a few times without ears on and it is loud and uncomfortable, but taking shots indoors without ears will not totally ruin your hearing, which was the goal. This rifle is next to my bed, so I wanted a set-up that would be possible to shoot sans ear protection and not be overly damaging to my ability to hear.
Putting the K on the 11.5 gun is very handy, but sounds quite a bit louder than the 13.7, as well as having more muzzle flash. I invested in the flash hiding end cap from dead air, and that has seemed to help. Also, bulk blaster ammo like federal xm193 is much flashier at the muzzle with the K than something like gold dots or federal fusion which I keep in the gun.
When it comes to 'performance,' I actually feel like I shoot my 13.7 gun better with the can than without. With less noise and concussion, it's easier for me to keep my eyes open and track the recoil of the gun to get it back on target and press the trigger again. I have not done any significant numbers testing to back this up, but I have ran through a list of drills with the rifle set up with a can, and based on my current ability to shoot a rifle, the can is not decreasing performance in any significant way, while adding benefits.
Having owned the sandman cans for some time, and shooting them quite a bit, I realize now that, for mer personally, I could do just fine with a lighter-weight can that is less 'rugged' for lack of a better word. For example, on my short 300 blackout rifle, I use an Omega 9K. It is very short and incredibly light weight. I can't shoot a belt-fed 308 through it like my sandman cans, but I don't own and probably never will own, such a firearm. If you are trying to decide whether to suppress your rifle or not, for me after owning cans and shooting suppressed, I will never go back. The comfort and enjoyment levels go way up. If you have concerns about weight and handling, there are many high-quality cans out there with surprising levels of durability that are also light weight. I do like having at least one rifle can like the Sandman that I know is as close to bombproof as I can get, but something a bit lighter might be what you are looking for. If you are in the Northern Utah area, I am happy to bring out a variety of cans and barrel lengths for you to try out. I also have friends around here that have a variety of suppressors that you could get a pretty good idea of what you like. If not, I would encourage you to go out and try before you buy, especially with suppressors. Even if that means buying a muzzle device or two, or driving a bit to meet someone. The benefit of being able to know exactly what you are getting in sound reduction and handling, etc. are well worth it.