Tuning a rebuilt SMLE #1 Mk 3

I recently had a SMLE #1 Mk3 rebuilt. The rifle is a bit of a blitzer with parts ranging from 1915 on up to the 20's. The barrel is from the 50s and was still in the grease when I bought it. I am currently looking for any info on armorers State-side that know this rifle. My gunsmith did an excellent job getting the rifle put back together, but I am questioning the head space on it. He doesn't work on 303s and probably only did what he did since I am a friend of his son.

When I finally got it to the range, the first shot was with Remington factory loads and I had total case separation. After clearing the broken shell I returned to the range with handloads I worked up (174gr Woodleigh on top of IMR 4064 @ 4 different weights & 215 gr Woodleigh on top of 35 grs of IMR 4064). The rifle fired without breaking any shells, but all but one had high primers and a few pierced primers. Granted these were all unfired Winchester brass.

I just want to find somebody that knows these guns well enough to give it a once over before I sink the money into the headspace gauges & firing pin gauge to check it myself.

Thanks.