Use what ya have. Most screw stock is lead bearing steel so it machines easily. I just cant justify paying $3 to$4 for a simple #10 or #8 lock bolt. I have examined many original rifles , and a lot of them show#10 lock bolts w/ the front bolt thinned to a #8 size to allow for ramrod clearance. In light of that ,I have a hardware store that sells unplated # 10 x 24 threads per " carriage bolts for $2 a pound. They come in many lengths . The rounded large heads need a slot sawed in them, and the square part of the shank filed off. The heads can quickly be reshaped by putting the bolt in an electric drill motor and holding the head against a fine belt sander , then against a hard buffing wheel for an extreme polish good enough to heat blue w/ soldering torch. Hold in the flame 'til the bolt head turns iridescent blue and quickly drop in water. oldwood