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Long Range Hunting & Shooting
7mm Terminal Performance Issues? True or False?
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<blockquote data-quote="NZ Longranger" data-source="post: 433052" data-attributes="member: 14"><p>Scot,</p><p>This old world is just one big place now! The difference between the USA and NZ is just seconds on the web or 4 days via airmail! Everything you have we have as well.</p><p>As I said above, if a bullet doesn't perform, its due to it being chosen for the wrong application not anything to do with a few thousandths of an inch difference in diameter. Certainly the big 7mm's are capable of driving bullets very fast, but you'll have the same issues if you drive the comparable SD bullet of the same type that speed in the same case capacity family. A case in point would be the RUM family and the 7mm 162gn A-Max at say 3300fps verses the 30 cal 178gn A-Max at the same speed. These velocities are straight out of the Hornady manual and are for comparison only. You can drive the 162 way faster than this out of the 7mm RUM. Anyway, the point is you'll get similar terminal performance with both these examples, with a very slight edge going to the 30 cal due to the 16gns more bullet weight and 24 thou more diameter. Up close they'll both tend to over expand and may lack penetration depending on what bones are hit, but will perform well out past 300 yards or so. The 7mm does have a significant advantage in BC though, .625 G1 verses .495. This is where the 7mm's shine - BC verses velocity.</p><p>If at the other end of the bullet construction spectrum, you choose the Swift A-Frame in 7mm 175gn at 3000fps verses the 30 cal 200gn, both at about 3000fps, again out of the Swift manual, the expansion ratio would be similar for both if hitting the same size animal in the same place. The 30 cal will penetrate a little more due to the 25gn increase in bullet weight, but the 7mm again has the better BC, .493 verses .444. It also has the better SD. These bullets will both penetrate like hell on animals at close range and I have put them lengthways right through animals like the Gemsbok in Africa and the Red stag here in NZ.</p><p>The point of these examples is that it is the bullet construction that is the difference between the A-Max over expanding up close but working superbly at long range and the A-Frame penetrating right thru up close, not 24 thou of bullet diameter! </p><p>If you choose the same weight bullet of the same family in each caliber, you'll have an even more noticeable over expansion in the 30 cal due to the increased velocity you can drive it at due to the larger expansion ratio.</p><p>The 300 RUM pushing the 168gn A-Max at 3400fps plus will be a bigger bomb than the 7mm 162gn at 3300fps.</p><p>The 30 cal 180gn A-Frame at 3200fps out of the RUM won't penetrate anywhere near as far as the 7mm 175gn due to extra 200fps of velocity causing more expansion. The 7mm's .310 SD also aids penetration verses the 30 cal 180's .271 SD.</p><p>None of this is opinion, this is fact. You will find examples of hunters choosing the wrong projectile for the job in any caliber, and maybe in some of the above poster's experiences they happened to see more guys shooting 7mm's using the wrong bullets, or hitting in the wrong places. But that doesn't mean the 7mm is a worse killer than the 270 for example! That just simply ain't credible!</p><p>Greg</p></blockquote><p></p>
[QUOTE="NZ Longranger, post: 433052, member: 14"] Scot, This old world is just one big place now! The difference between the USA and NZ is just seconds on the web or 4 days via airmail! Everything you have we have as well. As I said above, if a bullet doesn't perform, its due to it being chosen for the wrong application not anything to do with a few thousandths of an inch difference in diameter. Certainly the big 7mm's are capable of driving bullets very fast, but you'll have the same issues if you drive the comparable SD bullet of the same type that speed in the same case capacity family. A case in point would be the RUM family and the 7mm 162gn A-Max at say 3300fps verses the 30 cal 178gn A-Max at the same speed. These velocities are straight out of the Hornady manual and are for comparison only. You can drive the 162 way faster than this out of the 7mm RUM. Anyway, the point is you'll get similar terminal performance with both these examples, with a very slight edge going to the 30 cal due to the 16gns more bullet weight and 24 thou more diameter. Up close they'll both tend to over expand and may lack penetration depending on what bones are hit, but will perform well out past 300 yards or so. The 7mm does have a significant advantage in BC though, .625 G1 verses .495. This is where the 7mm's shine - BC verses velocity. If at the other end of the bullet construction spectrum, you choose the Swift A-Frame in 7mm 175gn at 3000fps verses the 30 cal 200gn, both at about 3000fps, again out of the Swift manual, the expansion ratio would be similar for both if hitting the same size animal in the same place. The 30 cal will penetrate a little more due to the 25gn increase in bullet weight, but the 7mm again has the better BC, .493 verses .444. It also has the better SD. These bullets will both penetrate like hell on animals at close range and I have put them lengthways right through animals like the Gemsbok in Africa and the Red stag here in NZ. The point of these examples is that it is the bullet construction that is the difference between the A-Max over expanding up close but working superbly at long range and the A-Frame penetrating right thru up close, not 24 thou of bullet diameter! If you choose the same weight bullet of the same family in each caliber, you'll have an even more noticeable over expansion in the 30 cal due to the increased velocity you can drive it at due to the larger expansion ratio. The 300 RUM pushing the 168gn A-Max at 3400fps plus will be a bigger bomb than the 7mm 162gn at 3300fps. The 30 cal 180gn A-Frame at 3200fps out of the RUM won't penetrate anywhere near as far as the 7mm 175gn due to extra 200fps of velocity causing more expansion. The 7mm's .310 SD also aids penetration verses the 30 cal 180's .271 SD. None of this is opinion, this is fact. You will find examples of hunters choosing the wrong projectile for the job in any caliber, and maybe in some of the above poster's experiences they happened to see more guys shooting 7mm's using the wrong bullets, or hitting in the wrong places. But that doesn't mean the 7mm is a worse killer than the 270 for example! That just simply ain't credible! Greg [/QUOTE]
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