'Texas10' - Your Krag, #133937, was assembled around October, 1898. Therefor, it is not really a "low number" Krag.

What is your barrel length? Both model 1898 carbines and rifles are found near your Krag's serial number.

If you 'slugged' your bore (with a soft lead oversize slug), you could easily measure your bore's land and groove diameter.

FWIW - I have generally found my model 1898 Krag barrels to run about .3085 to .3095 inches in groove diameter.

My rifles in .30-06 and .308 Winchester & NATO calibers have 'tighter' bores.

My Krag barrels shoot .308" diameter commercial jacketed bullets well.

If you are going to shoot cast bullets, it is important to know your actual bore dimensions. Cast bullet shooters generally use projectiles sized .001" or .002" over barrel groove diameter.

Most of us would enjoy seeing photos of your 'Family Krag'.