Re: 7mm Dakota
If you take the same throat length for both rounds, the Dakota has 13 to 15% more case capacity then the Rem Mag. That comes out to right at around 10 to 11 grains more capacity.
What is harder to compute into the comparision is that XPs handgun is specially throated to seat the 200 gr ULD RBBT WAY OUT THERE. Just guessing I would suspect this will add another 3 to 4 grains capacity over a factory throated 7mm Rem Mag.
Also, the throat on XPs handgun is very tight which will greatly add to the velocity of the barrels potential compared to a factory chamber job.
Other things you need to realize as well is the VAST majority of velocity is generated within the first 15" of barrel length. After that the increase in velocity per inch of barrel is certainly still there with these big rounds but it drops off significantly from this point out.
Also, it is easier to get a heavy bullet to good velocities in a handgun length barrel then it is to drive light bullets to high velocities in the same barrel length. The reason is because the heavy bullets produce a more efficent powder ignition and burn in the first several inches of barrel length.
Back to your rifle, I would not be surpised at all to see your 7mm Rem Mag reach 2700 fps with a 24" barrel. In fact I would expect a bit more then that in most cases. The 7mm STW will get around 3000 to 3050 fps with this bullet in a 28" barrel or longer.
A 7mm RUM will get you into the 3100 fps range and the 7mm AM will get you +3200 fps.
If I had to guess, I would say you could play with the 2800 fps range with your barrel length but that is just a guess. The 175 gr pills are a better choice for the 7mm Rem Mag in my opinion with that length barrel.
The question of stability comes into play as well. If you have a 1-9 I would say 50-50. If you have a 1-9.5 I would say no.
In testing XPs handgun before I shipped it, I was pushing just shy of 2700 fps with this same buller without even pushing things. I suspect his XP would get even more velocity if he pushed her really hard but if you read his post you will see he is loading the accuracy load which is around 2700 fps.
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