Splash, sounds like you are getting an after burn in the moderator, what I mean is that your propellant is not fully burning in 20" of barrel, it is burning in the moderator between baffle 2 and 3 causing a high temparature and burning of baffles.
I bet if you fire the rifle without a mod you have a hell of a flame thrower..
and you will be damaging your hearing with any less than 4 baffles.
we measured 9dB reduction with 1 baffle, 16,6 with 2 and 20,9 with 3. you need 4 to get below the damage threshold.
Gas Cutting-Wear of baffles:
We put several hundred rounds through test models in fairly rapid succession and didnt see much wear by gass cutting for the first couple of hundred and ive about 300rds through mine on my .260. with no signs of gas cutting at all yet. these have been slow steady rounds whilst hunting or at the range, Ive a mate using one of a .416 rigby, and he's no problems as yet.
what realy makes a difference is the design of the shape of the back of the baffles, as well as the actual type of alloy we use ( slightly higher melt point) plus the very hard coat anodising( hart-coatieren is what the Germans call it) they are subjected to, the shape leaves the part of the baffle that gets the most thrust fairly thick, this distributes the heat and the anodising seems to repel the heat - gas cutting fairly well.
of course with the melt point of alloy is lower than the burning temp of propellant gasses, baffles will definately suffer gass cutting at some stage ( even rifle barrles fire crack after the first shot in the thorat area)
but so what,, everyone knows you need a new exhaust on a car at some point and a moderator is no different. the beauty of the modular systems is you can, like an exhaust, replace just the back box, mid section of down pipe, rather than the whole system from manifold to tail pipe. One should keep an eye on the state of the baffles and aquire new ones as and when required.
definately i would use a couple of stainless-coated baffles ( coated to make then dark in colour) if i was using the mod on a magnum or higher intensity cartridge.
I believe the lighter weight and increased ergonomics of the alloy type moderators certainly makes up for anything they loose in lifespan.
rgds Pete