I have been meaning to try Ramshot Magnum in my buddies 300 win mag that I load for him. I am planning on using the 180 grain Inner bond of 180 grain accubond. Has anyone tried this combo(s).I have many other slow burning powders but was interested in trying this Ramshot product.

I've played with it some and it didn't impress in my gun which is not to say it might work great in yours. I can say my tikka t3 has a generous freebore and usually needs more than max published loads to shine. I got all the way up to 84.2 grains with the 180 ab and it was doing just a tad over 3000fps but had vertical stringing.
I think you'll find it slower than ramshots data suggests so work up. Most results I see with rsmag in other guns says it will be slower too. But that's why we always work up. Good luck.

It is a tad slow for 180 grain bullets. I have a very accurate load for a particular rifle but I'd use ramshot hunter instead.

What IMR or hodgdon powder would have a burn rate similar to RS Magnum ?

Ramshot Magnum is in the same burning-rate range as IMR7828 or H1000.

I've tried Magnum with various bullets in the .300 Winchester Magnum. It works VERY well with 200-grain bullets, but with 180's Hunter works better.