Jmorrismetal
Active Member
- Sep 27, 2014
- 468
You wouldn’t see me shoot a subsonic 6.5 at any range, that’s not “it’s game” so to speak.
Might be worth plugging in some numbers to see difference between the two and what setting a speed limit does to trajectory as well as get a better idea of what would be a “useable range” for each.
If we took the 123gn SMK and loaded it to 1050 FPS the first thing we do is take a hit in the BC, normally .510 over 1635fps but drops to .420 subsonic (not that it matters much going that slow).
https://www.sierrabullets.com/store/product.cfm/sn/1727/264-dia-65mm-123-gr-HPBT
Anyhow zeroed at 100 we get
0 yd -1.5” 301 ft/lb energy
50 yd 3.4”
100 yd 0
150 yd -12.1
200 yd -33.5
300 yd -105.3 229 ft/lb energy
Keeping everything the same but using a 405 gn bullet with a .281 BC we get
0 yd -1.5 991 ft/lb energy
50 yd -3.5”
100 yd 0
150 yd -12.7”
200 yd 35.2”
300 yd -111.5” 674 ft/lb energy
So the big old bullet that has the BC of a brick doesn’t loose that much before trajectory gets almost unusable, with both loads. It is also worth noting that it has more than twice the energy at 300 yds than the lighter bullet has at the muzzle and over 3 times the energy upon exit.
The point was Mathematically the better BC bullet will catch up and surpass the other, in energy, at some point but it will be beyond their usable range. At 2000 yards the lead for energy the 405 has over the slicker 123 is cut to just 63 ft/lbs but you are looking at 879.5 FEET of drop at that point...
Might be worth plugging in some numbers to see difference between the two and what setting a speed limit does to trajectory as well as get a better idea of what would be a “useable range” for each.
If we took the 123gn SMK and loaded it to 1050 FPS the first thing we do is take a hit in the BC, normally .510 over 1635fps but drops to .420 subsonic (not that it matters much going that slow).
https://www.sierrabullets.com/store/product.cfm/sn/1727/264-dia-65mm-123-gr-HPBT
Anyhow zeroed at 100 we get
0 yd -1.5” 301 ft/lb energy
50 yd 3.4”
100 yd 0
150 yd -12.1
200 yd -33.5
300 yd -105.3 229 ft/lb energy
Keeping everything the same but using a 405 gn bullet with a .281 BC we get
0 yd -1.5 991 ft/lb energy
50 yd -3.5”
100 yd 0
150 yd -12.7”
200 yd 35.2”
300 yd -111.5” 674 ft/lb energy
So the big old bullet that has the BC of a brick doesn’t loose that much before trajectory gets almost unusable, with both loads. It is also worth noting that it has more than twice the energy at 300 yds than the lighter bullet has at the muzzle and over 3 times the energy upon exit.
The point was Mathematically the better BC bullet will catch up and surpass the other, in energy, at some point but it will be beyond their usable range. At 2000 yards the lead for energy the 405 has over the slicker 123 is cut to just 63 ft/lbs but you are looking at 879.5 FEET of drop at that point...
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