Jimmy, I'm sure you have done this already but check the muzzle of your barrel. If it has been eroded by too much cleaning, and if there is enough barrel left, have it cut down on a lathe to the end of the erosion, and recrowned. 4-6 inches cut off should get it past the erosion.
I seriously doubt that an 1895 Spanish rifle was used in WWI by the Germans. Most likely used in the Spanish revolution. A good friend had an 1895 which was rechambered to .308 X 57 (rechambered by IDI) and if I were looking for a problem of undersized bullets that would be the first thing I'd look for, otherwise I'd think a shot out or cleaned out, as the one I have has been. More barrels having been cleaned from the muzzle are worn out at the muzzle from aluminum cleaning rods than were shot out.
Want to ruin a bbl quickly? Use an aluminum cleaning rod, clean only from the muzzle and do it often. In WWI and WWII the Germans were given a segmented cleaning chain with aluminum beads to pull through their bbls.
Okay, why is an aluminum cleaning rod so bad? Take a look at one, you are not looking at pure aluminum but rather at aluminum oxide, one of the most abrasive substances known to man. Shove, pull, push, drag or by some other method, one through a gun barrel and watch the rifling disappear like fog on a sunny day. But yours is coated with plastic. Good for you, because now you have traded aluminum for whatever gunk was in the barrel and has just been transferred (imbedded in) to the plastic. Brass, hard steel, or stainless steel are the only cleaning rods which see the inside of my barrels and even then they are inserted with a centering funnel. This is one reason why so many M1 barrels need replacement, and also why the only proper cleaning rod to use on an M!, M1A, M14, M1 Carbine is the issued cleaning rod, made of steel, one piece or segmented.