I put one in my WASR-10, and the red dot sight shook loose. Yes, I did use thread-locker. No problem with function though.
When the spacer broke off the recoil spring guide for the TWS scope mount, I put the buffer from the WASR-10 into the Tantal. All the stock screws and the buffer tube castle nut shook loose. Again, I had used thread locker on the screws and the nut. The buffer didn't affect function though.
Thinking that, with the variety of 12 gauge ammo, a buffer would probably be a good thing in the Saiga-12 to protect the stock trunnion from impact, and keep the rivet holes in the receiver from egging out. I had intermittent stovepipe jams. I tried turning the gas plug to open up the gas flow, and I still had the stovepipes, and the shotgun beat up my shoulder pretty good.
Without the stupid buffers, the Saiga-12 has been running 100% with the high-brass gas setting (not beating me up as much) and the carbines are holding together, and not shaking loose anymore. The buffers are going into my bag o' AK junk with the crappy Tapco folding stock, the stock Saiga-12 trigger, the heavy gritty Century Arms trigger and unfinished wood stock set, and the foreign-made parts that I'm not allowed to use. I don't need the buffer for the TWS scope mount anymore since they sent me the proper recoil spring guide, the Saiga 12 doesn't work properly with one, and there didn't seem to be any benefit to having the buffer in the WASR-10.