The 280AI and 7mm WSM are too close to call as far as velocity, and the 7mm WSM has the advantage of a short action but limited magazine capacity. The 280AI is on average less than 150 fps slower that the 280AI, which would make aqdifference out past 700 yds. If it was me I would go hands down with the 280AI. It recoils less, which means leass flinching and more pain free shooting. For LR, the best gun/caliber is the one you practice the most with.
7 WSM on a long action mag bolt face will give you room in the magazine to seat bullets really long.
This will allow you to load them a bit faster as you gain case capacity.
Also there is no need for a Wyatts mag box saving you $$ in the build process.
Something to consider (win, win) ...
The comparison above with the 280AI and 24 inch barrel with RL22 compared to the RM with the 26 inch barrel with Retumbo is not apples to apples, of course the long barrel, slower powder combination will give higher velocity.
In a 24" Broughton shooting 168 VLD's, I'm getting about 2930 fps with the 280AI using RL22. My 26" 7RM shooting the VLD's with Retumbo gets me around 3025 fps. The 7 Rem Mag could be pushed a little harder, but accuracy falls of in mine beyond that.
This is going on a Ruger #1 that is currently chambered in 280 Rem. It has a head space problem and since it is the short factory sporter barrel I am going to replace it. I am getting a Broughton #3 contour 24" barrel. So that is why I wondered if either of the magnums would make much of a velocity gain over the 280AI in a 24" barrel. I'm new to reloading and don't fully understand the relationship between barrel length and powder burn rates.
The name of the powder game is getting it to completely burn up before the bullet exits the barrel. The trick is lining up the powder with the bullet weight. This provides the best accuracy and shot to shot consistency in speed. This of course is what is optimal for best performance, but isn't necessarily the way things always go. You don't want unburnt powder exiting the barrel, but you don't want it to burn to quickly either. Think of a rocket taking off and flying into space. To quick of a burn will not get it into space, but a to long of a burn might send it to Mars. It is a delicate balance.
In theory a short barrel should use faster powders to achieve this optimum potential. A longer barrel requires a slower powder to get the optimal burn. Like I said this is not always the case. You just have to try different powders. If you have taken notice, the heavier the projectile the slower the burn rate on the powders. You can compare this to powder burn rate charts found on the Lapua sight and there may be one in your reloading manual. They are all pretty consistent with one another. Just compare the powders with one another and make sure to pay attention to company brands. An IMR 4350 is not the same as a Hodgedon H4350.
I hope this helps a little.
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If you have a long action, the 7mm Rem Mag will smoke anything the 7mm WSM can do in a short action. The advantage comes in the fact that the Rem Mag already has a capacity advantage in and of itself but when you seat a heavy 7mm deep into the WSM for the short action receivers, you loose even more capacity.
Yes the WSM is more efficent with barrel length and in a shorter barrel that is more significant but it will not make a dramatic difference and in the end, the 7mm WSM will fall short of the handloaded form of the 7mm Rem Mag by at least 100 fps.
Other issues, a WSM can be made to feed acceptably well in a short action receiver, its best to start with a receiver designed specifically for this type of case design but you will still have a choppy feed cycle no matter what you do.
Compare that to the 7mm Rem Mag which will feed smooth as silk in a long action, if your looking for a repeater, there really is no comparision. For a single shot, obviously no advantage either way.
One more thing to consider, brass. The 300 WSM will likely be around forever, the 7mm WSMs future is not so secure. You could make WSM brass out of 300 WSM brass but you would have to make sure you position the shoulder location properly and then fireform the case to move the shoulder location slightly forward compared to the 300 WSM.
The 7mm Rem Mag has been around for a long time and will always be around as long as we can legally own big game rifles. On top of that, brass can be made from a host of other standard magnums but this really is a moot point as there are very few, if any standard magnums more popular then the 7mm Rem Mag.
In its handloaded form, the 7mm Rem Mag is the full equal to the 7mm Wby Mag. Only in factory form is this chambering downloaded severely and this is in my opinion simiply to try to make the larger 7mm magnums look more impressive. Sad really, because it really puts a poor light on what the 7mm Rem Mag really is.
Saying the 7mm WSM is the full equal to the 7mm Rem Mag is simply not true. All things being equal, it will easily fall well short of the handloaded 7mm Rem Mag loaded to standard modern magnum pressures that the WSM is currently loaded to.
It feeds better as well.
Yes it has a useless belt but after the cases are fired once, that becomes a moot point as well as the case will then headspace off the shoulder and not the case belt as long as the case is resized properly.
The myths out there about the belts causing rough feeding are simply that, just some writer looking for something to complain about when there is really nothing there at all to complain about just in an attempt to promote a new case design.
Do not get me wrong, I do like the WSM cases but in reality, they are not the full equal to the standard belted magnums that we have been force feed to believe over the last several years.
They have great performance and its always great to have as many options as possible but for my money, for a big game rifle, I would lean toward the 7mm Rem Mag. For a single shot long range match rifle, either would do but the WSM may get the node.
The 7mm Rem Mag is not sexy any more but that does not take away from the fact its an extremely potent chambering that will out perform the WSM 7mm any day of the week.
The 280 AI and the 7mm WSM are basically ballistic twins in every way, again, the AI will fall around 100 fps or a bit more short of the Rem Mag. Its a great chambering as well but it does have its issues also. Have to fireform brass unless you buy the far over priced Nosler brass. You can form brass from other easy to get cases but the neck lengths will tend to be a bit off, not a huge issue.
As far as barrel life, the 280 AI is probably the best followed very closely by the WSM and then Rem Mag but they are all very good on barrels for their performance levels.
Again, all comes back to what receiver you want to use. Long action, I would go with the Rem Mag simply for performance.
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I have a 7 WSM on a Weatherby MKV Long action. I have to shoot it single shot obviously because the case does not taper at all. But because I am able to seet the bullets out longer, I am honestly getting 3185 fps on average with 168 Bergers. I am running 69.5 gr of H1000 and have ran it out to 2000 yards with decent accuracy.
What are the pressures like in a 280AI shooting 160 to 168gr bullets? The only reloading manual I have that shows pressures is a Lee second edition. It does not list the 280AI but shows the pressures of the 7wsm being quite a bit higher than 7rem mag pressures. Does higher pressure mean shorter barrel life, or just more felt recoil?