From Doug Bowser's book on Swedish military rifles:
"WARNING!!!! Do not shoot Danish manufactured 6.5 x 55mm military ammunition in a Swedish Mauser. The combination of soft jacket material and sharp edges on the lands and grooves of the rifling contributes to heavy fouling, which may cause high chamber pressures. There have been reports of several Swedish Mauser Rifles being blown up by this ammunition. The first reference I have seen on this problem was in The Book of Rifles by Smith & Smith. (The ammunition is also mercuric primed!!!)", page 86.
Like I said, I've shot thousands of rounds of this ammunition. Maybe close to twenty thousand. All through four different rifles. No signs of extreme jacket fouling build up.
I didn't find it any more difficult to clean than any other smmo loaded with cupro nickle jacketed bullets.
I shot the pulled bullets that were sourced out in 5k bulk lots as well as cases of loaded ammunition.
I cleaned the rifles back to the metal of the bore, every 50-60 rounds, on that same evening, after the shooting session. I'm very fussy about cleaning. Maybe that's why I didn't have any issues.
At the time, all of the brass I had was Berdan primed and started out with corrosive primers. Tony at International sent me a 5000K count of proper primers for reloading. I don't know where he got them, they were corrosive as well. Maybe that's why he didn't charge me for them???
I'm not trying to contradict Doug Bowser. I'm just giving you my personal experience with thousands of rounds of this ammo.
Danish and Swede troops/civilian shooters were well versed in proper cleaning procedures for corrosive ammo.
I've seen M96/38 rifles with their receiver rings blown off. In every case, it was due to HOT loads or failure to clean the rust out of bores, before shooting. When these rifles and the ammo, from Norway, Sweden, Denmark, Finland was surplussed, most shooters had no idea the ammo was corrosive and didn't clean appropriately.
I still see a lot of people today that just give a blank stare when corrosive primers are mentioned. Lots don't even know the difference between Berdan and Boxer primers.