who has used one of these, what has your experience been? are they soild enough for 300yd shots off of bipods with this as a rear rest?

Will227457: If you are referring to the Dog-Gone-Good made Darrell Holland designed 3"x4"x5" "Toe Bag" then I have one and have used it extensively on Varmints and several times on Big Game!
I recommend everyone carry one of these in their day pack or clipped to ones belt. I have used it not only as a toe bag but as a "soft" rest for the top of a wooden fence post and as a soft rest for the top of a metal fence post. I have used it as a forearm rest on volcanic rock and on and on.
Now as for me promising you that YOU can hit a Prairie Dog at 300 yards with a bi-pod front rest and the Darrell Holland designed toe bag as a rear rest - I can't promise that!
But I do know when using this "adjustable" sandbag as a rear rest you would have a whole LOT better chance hitting said Prairie Dog than if you were "free handing" it!
I used my rear toe Dog-Gone-Good bag to help me harvest an Antelope at a lasered 505 yards last October!
That IS the furthest verified distant head of Big Game I have ever taken.
I had the Harris Bi-pod on the front of my Remington 700 Sendero in 270 Winchester, had my Leupold 8.5x25 variable cranked up to 25 power and had the whole rig stabilized with the Darrell Holland designed rear toe bag!
That was as close to that nifty Buck Antelope as I was gonna be able to crawl and I took my time setting up that shot to make sure I was as steady as I could possibly be.
Bang - flop!
I heartily recommend you pay the $12.00 or $15.00 for one and use it!
Hold into the wind
VarmintGuy

I ordered one arrived in less than a week, going to the range tonight will give it a little test run and have a varmint hunt set up for later this month to really try it out!!!!!