Anderson AM10

I bought this rifle used in .308 last year. Smooth firearm at the range and I plan to take it on a hog hunting trip this winter. The forearm has no rails on it except for the top. I bought some rubber grips to give it some grip but the “standard’ picatinny hex screws don’t fit. The holes are smaller. Anyone have any idea what size the holes in this rifle are? 

Ordered forearm rails from Anderson. Screws fit, screw holes don’t line up. I don’t want to add more weight to the front end of this rifle. Probably just going to find a good grippy, heat-resistant pair of gloves. In black. To match the scary rifle.