I have been struggling with caliber choice for a build I wanna do and I am curious about one thing. I was leaning towards the 7mm rum because of the high BC of the bullet I preffer the 160gr Accubond. I have a 7stw now and it is all I can do to push that bullet at 3100fps and I have read that the 7rum pushes it around 3250fps. With that I had a real concern about barrel life, so I started looking at the 300rum since it's not quit so over the top. thats when I discovered people were getting 3200fps out of it with a 200 gr bullet which has a higher BC. After running that through my calculator I am finding it superior to the 7mm. How is it poosible to get that velocity out of the same case and a heavier bullet??
I am not sure how you get the heavier bullet going faster with the same case capacity. What I do know is that it does not surprise me that you can get 3200fps with the 200grain bullets in a 300RUM. My RUM shoots the 208grain Amax at 3150+...
The 300 RUM is the one to have over the 7mm RUM. You can get 3200 fps out of the 200 AB. It is not as harsh on barrels. I have two with 28" barrels and they both get 3200 fps with the 200 AB. My favorite one I made the long shots with last year was using the 208 Amax over 3200 fps. Some barrels are faster and some are slower and depends on your barrel length. Just remember 3100-3200 fps are both going to easily kill anything just make sure the accuracy is there.
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Last edited by Long Time Long Ranger; 10-18-2011 at 01:53 AM.
Alot of guys have talked here over the years about getting 3200 fps MV with the 200AB or similar in a 300RUM. I'm not saying it can't happen, but for me in my 26" barreled 300RUM, 3075 fps MV or so is max. A 210 Berger is right around 3K fps MV max for me--unless I only want one or two firings per case. I may have a slow barrel and the others may have a fast and/or longer barrel. A 300 RUM is one of those highly overbore cartridges that could really use a 30" or longer barrel to truly see it's potential.
I forget the name of the smith now that I talked to a couple of times. He's the guy the came up with the 300 Tomahawk (300 RUM Imp.--'bout another 100fps in simlar lenght barrels with that number going up the longer the barrel, to a point) that was all the rage a number of years ago--never hear about it now. He refused to make the Tomahawk in less than a 30" barrel.
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Im kinda thinkin it's due to lower pressures from not trying to force that pressure through a 7mm hole. but I'm not sure.
Your on the right track. The 7mm has a smaller bearing surface compared to the 300. The 300 has a larger surface to push against, therefore slightly easier to get higher velocity with same bullet weight.