Just put a new scope on. Looking for a bipod that will attach to a rail. The Harris bipods that I have seen all attach to the lug. I don’t want to buy a adapter too. Not sure how long the legs should be. Rifle will be used mostly at the range. Should I get one that swivels? Here is a pic of the gun it will be going on.

There are a few threads here if you use search that discuss bipod options. Here’s a thread on bipods with a poll.
https://www.m4carbine.net/showthread.php?t=44604
As I recall, some leading bipod options are:
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Some variation of the Harris. This is what I have, plus an Am. Defense QD mount for the Harris.
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The Bobro combat mount. Incredible from what I hear, but spendy.
http://www.bobroengineering.com/view/product/1/ -
The TD Bipod. Here’s a look:
http://www.rainierarms.com/?page=shop/detail&product_id=695
You can find advocates for all of these. For me, the Harris + mount works for range shooting and combined cost was still less than the others.
Atlas
It ain’t cheap.
http://www.accu-shot.com/catalog/product_info.php?cPath=24&products_id=68
Harris is a good Bi-pod with a good price.
A buddy used a Harris on his M249 while in the Army…He stressed how robust it was.
So I got one and it has held up to my “abuse”…one example:
My rifle fell off the back of my ATV, and down several feet hitting rocks on the way, while cruising along a creek bed…was still locked on tight and nothing was bent. Except my front sight post…
Edit: The one I got had a rail attachment come with it. I can attach it to the rail on me foregrip (MOE).