I am looking at purchasing one of these for my .45-70 just wondering if anyone has one and would it fit in my RCBS rockchucker press?

Thanks,

Prarie boy - Yes this die would fit your press. It is the standard 7/8" thread. But I'm just wondering why you want to buy one for your 45-70. I am sure the dies you are using now have a roll crimp die which is good for this cartridge.
The Lee factory crimp die is a good die and I use them in my .223, .270 and 30-06 (and for my 300WM when I had one) and this die works great for these bottle neck cases. The reasoning is that it provides a more uniform tension on the case mouth/bullet interface resulting in an increase in accuracy.
I've found that my accuracy has improved in each cartridge from only a little to a significant improvement. But personally I would try the crimp in your existing die.

Thanks for the reply bronko, I have been putting a roll crimp on the cartridges I have loaded thus far and my groups are all over the place, someone suggested I use one of these dies on the .45-70.

What's your definition of all over the place. I have a Marlin guide gun in 45-70 and I load Hornady 300 gr Interlock bullets and H4196 powder and have pretty darn good accuracy. I've taken 3 black bear with this load with 3 shots.

You know, I have gotten much better accuracy out of heaveier 350gr-400gr loads out of my microgroove. 300's never would shoot well.

Purchased my first for 35rem in a 336 with a tube magizine. It works great, specialy because I only partialy resize my brass for better chamber fit/head space. When I started loading the 358win with cannelured bullets I bought another,again it works great even with non-cannelured bullets.

For a tube magizine I think its tops and can give you more uniform stating pressues and thus better accuracy. You have already tyied the roll crimp the lee factory crimp is something to try and they don't cost much, so why not?