I have used several different mounts over the yrs on this type of rifle, and have settled on 2 different mounts for mine...
The first is the Bassett low picatinny mount.
http://www.bassettmachine.com/prod_smpr.htm
Have had a couple of them for awhile now, and they do work as advertised. The nice feature I like about this mount is that once the optic is zeroed, I can remove the mount/optic combo from the rifle, use iron sights, and re-mount the Bassett/optic to the rifle without loss of zero.
This mount does not use the cartridge clip guide slot as a mounting point, so I can also use "stripper clips" when the mount is removed.
If I had to pick only one, then it would be the ARMS#18. (I like the older split rail version the best)
It is lightweight, compact, and very low in profile as compared to the other receiver mounts (to include the LRB M25). It is also very solid if properly installed. This mount uses the cartridge clip guide slot as a mounting point, just FYI. Quick release rings might come in handy if you wanna switch back and forth between optics and irons. Once the optic is removed, it allows use of the iron sights without having to remove the mount itself.
Note: Be advised that thier is a similar mount out there now that closely resembles an ARMS18. (Promag if memory serves me). I dont know if the knockoff mount is worth the $$ or not, but they do cost less than an ARMS does, so dont be fooled into thinking that it is an ARMS #18 mount. Look for the NSN on the mount itself, along with the swan logo ifn's you want an ARMS18....
Using the rifle pictured above with the ARMS#18 split rail mount, a set of Millett type rings, and a very low priced Simmons 3-9 scope, I have taken TX hogs out close to the 400yd mark. On the flip side, I have also dumped them at about 15ft in the brush using iron sights. ( Any closer and I might of had to buttstroke that little piggy...lol)
I'm currently searching for an optic that will work for both extremes, and looking at something along the lines of a 1-4 to mount onto the ARMS. Here are a few I'm looking at....
http://hi-luxoptics.com/index.php?option=com_content&view=article&id=51&Itemid=56
http://www.opticsplanet.net/weaver-rifle-scopes-v3-hunting-849400.html
11B