Barrel length is 21 inches and overall length is 41.3 inches. This short rifle features a turned-down bolt, recessed 5 round magazine, Guardia Civil Crest on the receiver (as shown below), fixed side support and sling swivel. These rifles are considered to be small ring Mauser receivers and are two-lug designed bolts, lacking the third safety lug commonly found on other Mauser rifles.
The two rifles are very similar except for caliber and barrel length (the 7mm barrel is a hair longer). The converted rifles typically have the caliber 7.62 marked on them. The Guardia Civil rifles, marked with the crest of crossed sword and fasces, apparently were converted to 7.62 from both 19 rifles in the 1960’s. Original 1916 short rifles were in 7mm Mauser (7x57). According to sources, these rifles were made by the Ovideo arsenal between 19. Using the model 1893 rifles, Spain developed the Spanish Civil Guard, M1916 Short Rifle, a rifle that changed a 29 inch long barrel to 21 inches. Here is an article from Surplus Rifle you can read:
Some shoot 308s and say no harm but I would shoot them with reloads that are not max loads if it was me.
Doubt very much they would take that pressure as they are a small ring model 1993 Mauser made for the 7x57.