First, Hello I'm Dave.
Is anybody using them?  I shoot a Colt Accurized rifle with a Jewel trigger and Mark 4 - 16X at paper and Pdogs.  Also play with a Colt 7.62 X 39 upper used on Deer and paper.  I'm real curious about the different buffer weights for the collapsable stocks and the recoil cycle function of these rifles.  Love the black rifle as a shooting platform.  Best for distance Pdog with the Colt is 1106 yards, 75 grain Hornady A-Max and lots of Varget...  best groups IMR 4064 and IMR 4895 and 77 Sierra's Yes in a 1 in 9.  appreciate the input.  Thanks for the use of your time and this site.

first off....thats some mighty fine shooting!

the Tubbs weighting is serving the same enhancement principal that heavier buffers, full auto carriers vs semi carriers do.

The more mass (weight) behind the carrier upon return to battery, the more reliable the lock up, and the the lighter the recoil

The latter serving the shooter in terms of a follow up shot, and the former in terms of reliable feeding

There is some very interesting reading on the subject here under the heading of "Buffer weights" (see thread link below) and while the Tubbs puts weight in the carrier, the principal is the same - weight behind the action

some related material - starts off a bit slow but covers the gammut

Welcome aboard, Dave!

ar15.com/forums/topic.html?b=3&f=12&t=241393

i use the mgi buffer in all of my rifles along with m16 bolt carriers.

How much Varget are you using to get the 75 AMAX to 1000 yards while still supersonic?  I'm an expreienced reloader, it's only safe in your rifle, work up, yada yada.....

Fixed Redfisher's linky

Gentlemen thank you for your thought provking responses.  I guess I'll have to touch and feel these items myself and form my own opinions about usability for my purposes.  

Now on the loading and my Oehler 35P, initial velocity is 2775 ft/secs and is just going subsonic at 1,100 yards according to my Sierra Infinity program.  This includes the temperature and humidity and altitude the dog was dusted at.  When this tube was new 5 shot 100 yard groups ran in the low 3's.  While following manufacturers instructions: Just add powder till you have what you want or have to rebarrel.

another benefit is that the rifle stays locked a little longer, allowing the pressure to subside a little more.  important when loading on the hotter side.

The benefits of the additional weight are pretty much accepted, and it doesn't matter to the rifle whether it's in the carrier or the buffer (as they are traveling together during cycling).  I have heard, however, that the flange on the base of the carrier weight can cause problems when "breaking open" the upper from lower.  This is not an issue with a heavier (but standard shaped) buffer