I prefer round, and filled with lead shot, not sand. Truthfully, there is no functional difference based on shape
That's what I thought. However, I 've mainly seen the round ones and they are a little more money around here. I have also heard about the lead shot so where would I get some of that?
Bird shot like in shot gun shells from your local sporting goods or gun store.. someone else will have to suggest the best size. It will be in the reloading supply section.
I just used sand because I wasn't sure about what size lead shot to use and there is a beach down the street with more free sand than I could ever use. It seemed like the natural choice to me at the time. Would just normal .177 cal BBs work as well as the lead bird shot?
Wow! Bass Pro has a 25lbs bag of #9 lead bird shot for $54.99. I'm not sure how many bags I'd need, but keeping my free beach sand is looking pretty damn good right about now. By the way: #9 Bird (0.75 gr.) 2.01 mm (0.079")
I've got #7 STEEL in my small round bag (10"). It took just under 10lbs. 25lbs of steel would fill a large bag but I'd think the 25lbs of lead might not be enough. I went with steel because I don't particularly like dealing with lead when I can avoid it. I ordered it from http://www.ballisticproducts.com/
The site I checked suggested not using steel because it will rust and cause the bag to break down earlier than it should.
I have no preference for square or round, but recently made some with a 2" band around the outside (ie some vertical height) instead of just top and bottom stitched together - I like them much more, they don't flop around, loosen up easier and the more compact overall size vs weight just seems handier. For filling I just use river sand (more rounded grains less likely to cut up the leather) but a smaller bag filled with lead makes a handy dolly for a few situations
Rinsing it with a strong solution of soda ash ( and letting it dry before filling) should inhibit rust for a long time unless the bag is getting wet or something...