If you slugged the bore from the chamber to the muzzle you squeezed the lead slug down to the smallest diameter and least worn section of the barrel, normally the middle of the barrel.

Example: I had a Springfield 03-A3 30-06 that was .312 in the throat, .309 in mid bore and .310 one inch inside the muzzle. The good news was it shot the Hornady .308 170 grain bullet designed for the 30-30 like a dream come true.

Try slugging and checking the bore a few inches down the throat and a short distance down the muzzle. Doing this will give you more information on your problem barrel.

Note: Different brands and type bullets are made and constructed differently, the 30-30 Hornady bullets I was shooting in my Springfield were designed for the 30-30 Winchester. These 30-30 bullets had a large bearing surface (the amount of bullet contacting the bore) AND a softer lead core. When these 30-30 bullets were kicked in the seat of the pants when fired the softer lead core allowed the bullet to expand more and fill and seal the bore.

Moral of story, try different brands of ammo and types of bullets in your Enfield before you give up on your barrel.

My Springfield barrel looked like a sewer pipe and had no rifling at the muzzle and still shot extremely well with the right bullet.