someone gave me a harris bi-pod and every gun i have put it on the bi-pod cants the rifle. it is not the pivoting version and i have fiddled with it all i can to get it straight. nothing appears to be bent or broken. Any suggestions?

This may take some experimenting to get the exact thickness but you need to glue a shim of leather to the low side of the bipod where it contacts the forearm. Make it exactly the size of the bipod's existing pad's footprint and that should solve the problem.

I found on a couple of guns that the bipods don't sit right because the sling swivel is not centered in the forearm.

Hello,
It sounds to me like you do not have the attaching device securely, totally, going through the swivel stud. And if you do, then it is not tightened enough to bring it into level. The Harris base which mates with the forearm of the stock is like a v block and would seek center when tension is applied. Double check to see that the two ears are evenly positioned around the swivel stud and then snugged up and if that still does not work, call Harris, they are very helpful and will suggest other things I am sure.
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dsiteman.

The sling swivel is probably off center if tightening the mount doesn't work. If the swivel screw is off center, try bending it a little. It is hard to bend the sling mounts as they are hardened and tend to break, but they are cheap to replace.

Like Fjold, I would definitely put some kind of shim between the forend and the mount, if I cared about the rifle finish. You might even put a thicker shim on one side to space it over.