FWIW, a month ago I finished off 750 rounds of Wolf .308 through my 1919A4. This was three belts left over from a shoot last year. Last year this stuff shot just dandy - the neghbor's kids took turns holding down the trigger, and I kept dumping 5 gallon buckets of water over the barrel to keep the gun from catching fire. No problems at all.
This year, I had all kinds of problems! Same ammo, still in the belts I had loaded last year, all from the same lot and same cases. But the gun wouldn't fire more than ten shots without stopping!
*Twice* it failed to load a fresh round and go into battery, and both times I discovered all the powder from the previous round all over the action. When I checked the bore, both times there was a bullet lodged just past the throat!
1919's are tough guns, but I've had my share of bad ammo blowing this one up, and I'd like to not have to fix it yet again...
After I managed to get through the first belt, the last two ran fine. That first belt ran up and down on the cyclic rate. I took some of the loose rounds and put them through my Ishapore Enfield (my "BMG ammo suitability test fixture") and sure enough, I had a bunch of hang fires. Between the two guns I managed to chop down a coupla trees, but it was annoying having a problem with ammo I had run flawlessly last year!
Nearest I can figure, this is the cause: I was using cloth belts for the 1919A4. I soak my belts in ATF (automatic transmission fluid) to soften up the .30-06 pockets to accept wider-bodied .308 rounds. The first belt was a crummy old green one, the other ones were the white ones. My guess is that I had a *lot* of oil in the first belt, which soaked into the Wolf ammo (probably the primer). This screwed things up, although it took a year for it to happen.
Never had this problem with any other ammo yet.
So don't oil up your ammo and let it sit around for a while - especially with the Wolf stuff!