Many have fit the Camp with the heavier (21# ??) Wolff spring and the blue buffer and shot the +P stuff in them without issue. However, I have never seen a good reason to shoot +p or +P+ ammo in every day use. That ammo was made for military sub-machine guns that were built for it. If you put the heavy springs in some blowback 9mm's they then don't like all "stock" ammo. I find a happy compromise is the "middle" spring Wolff makes. It seems to work just fine with all standard ammo including the ammo I normally shoot, mild loads.
While some just have to shoot the hottest loads they can find years of "the school of hard knocks" taught me that its not always a good idea to beat up the gun with hot loads just to shoot targets at the range. Normal power loads work just fine. In fact I reload and like many prefer to go with "medium" power loads. Easy on the gun, easy on the shooter and things last forever. I do have personal defense loads for home security but prefer not to shoot much of that stuff for practical reasons. Test it to insure its reliable and then set it aside for "duty".
The M-1 9mm I held and examined was very plastic looking. It did not seem very well made at all. Considering that companies track record with the .22 they stuck people with I ran away from that rifle as fast as I could.
Also, remember Erma? If not, check out their history with M-1 looking rifles. (.22 and .22 Mag.) Once they were common but now.....