I have a box of Sierra MatchKing 135Gr SP. I'm having a hard time finding ANY reloading data for this bullet. The latest Sierra load manual doesn't even list the 135gr. I'd like to use Winchester 748 for the powder as I have tons of it. Any suggestions to start with would be great.
Hodgdon has data with 130 and 140 grain bullets. They list W748 in between 4064 and BLC-2. With a bit of interpolation between the two bullet weights to arrive at 135gr I would consider 44-48grs.
I am only offering assistance to your question based on internet data not my own testing with your combination. Use at your own risk.
308 Winchester in a T/C Contender & Encore (Lyman Reloading Manual 49th Edition)
Warning! Notes: This data was developed for use in the T/C Contender and Encore handguns. It can also be used in other single shot or bolt-action handguns such as the Remington XP-100 and Savage Striker. Do not use these loads in any other type of handgun. Cases: Remington; trim-to length: 2.005"; primers: Remington 9 1/2; primer size: Large Rifle; Lyman shell holder: No. 2; cast bullets used sized to .308" dia.; firearm used: Thompson/Center Encore; barrel length: 15"; twist: 1-10"; groove dia.: .308"
Be Alert: Publisher cannot be responsible for errors in published load data.
Wt. Bullet Powder Manufacturer Powder Charge Velocity (FPS)
135 Sierra Jacketed SP Winchester W-748 44.0 2335
Remarks: sugg. start load; 2.725" OAL
135 Sierra Jacketed SP Winchester W-748 50.2 2603
Remarks: max load; compressed powder charge; 2.725" OAL