Bullet B.C. or Weight ?

D

dpopl8r

CGN Regular
Rating - 98.1%
52   1   0
Location
Alberta
I shoot a 300 RUM with bullets that have very high B.C (.505 or greater). However, I see the various .338's are often preffered for long range shooting, I would assume because of the higher bullet weights and not B.C., whihc is lower than the hevay .308 bullets.

What is more important for for long range shooting, B.C. or bullet weight, and why ?

This may decide whether or not I rechamber to 300 RUM or .338 RUM.
 
unfortunately, the best Hunting SLUG FOR THE 338 IS NO LONGER MADE- forgive me- caps stuck again- anyway, the best 338 hunter bullet was the 275 grain speer, better b/c too than the 250 and the same dose of powder- plus it fits in my bar which is something the 300 does not- i ain't got the twist for it either
 
dpopl8r said:
I shoot a 300 RUM with bullets that have very high B.C (.505 or greater). However, I see the various .338's are often preffered for long range shooting, I would assume because of the higher bullet weights and not B.C., whihc is lower than the hevay .308 bullets.

What is more important for for long range shooting, B.C. or bullet weight, and why ?

This may decide whether or not I rechamber to 300 RUM or .338 RUM.
Click to expand...
B.C. or Balistic coefficient describes the aerodynamics of the bullet. A high B.C. indicates that the bullet travels through the air efficiently, and is affected less by wind, and has a lower trajectory than a bullet with a lower B.C. Weight is only that. weight. Just because a bullet weighs a lot does not mean that it will get to the target accurately.
As this is a precision forum I am assuming that you are concerned about accuracy. In long distance precision shooting, when it comes to the most important factor in hitting what you are aiming at, it is B.C.
The secondary factor is recoil. The bullets with the absolute highest B.C. will also weigh the most. So there is an issue where increasing the B.C. beyond a certain point makes the rifle somewhat difficult to shoot, without flinching.
That is why the 142 gr. 6.5 VLD bullets are so successfull.They provide a very high B.C. with very minimal recoil. Hense very high acuracy. Especially over a long match where over 100 shots are fired.
There is a small ammount of experimentation going on with 7mm 180 gr. bullets at long range. And under certain conditions they have proven superior to the 6.5 mm. However the 6.5 is still the King.
 
Tons of factors and I'm just a beginner so correct me if I'm wrong. Shape is more important than weight. A heavy blunt bullet isn't going to beat a VLD.

Another consideration is time of flight. A fast say 155 gr 308 bullet is going to be exposed to the elements (wind) less time than a 200gr. (or is it?). But, will the 155 shed it's velocity faster as it gets out there? All very confusing, but interesting. Never really understood why in 30 cals, 155 and 175+ gr. bullets are used for 100m's but the 168's are frowned upon.
 
bisonhd said:
Tons of factors and I'm just a beginner so correct me if I'm wrong. Shape is more important than weight. A heavy blunt bullet isn't going to beat a VLD.

Another consideration is time of flight. A fast say 155 gr 308 bullet is going to be exposed to the elements (wind) less time than a 200gr. (or is it?). But, will the 155 shed it's velocity faster as it gets out there? All very confusing, but interesting. Never really understood why in 30 cals, 155 and 175+ gr. bullets are used for 100m's but the 168's are frowned upon.
Click to expand...

A 155gr .30 slug, unless a palma type such as the excellent lapua scenar with a BC of .500, will arrive on target potentially after a heavier bullet with a higher BC that left the barrel slower. So while the heavy may be slower to start, depending on the range it can physically pass the lighter bullet, and once that happens, the gap grows very fast. 168's tend to go erratic past 600-800 yards in a .308.
 
C = SD / i = w / id2

C = ballistic coefficient
SD = sectional density
i = form factor
w = Mass of object, lb or kg
d = diameter of the object, in or m
 
You don't mention application. For extreme hunting, you need high velocity, highest BC, larger frontal area and highest weight. Right now the gem is the 300gr 338 MK leaving a muzzle anything over 3000fps. The fastest accurate combo I know of reaches 3350 to 3450fps and is sub MOA at a very long ways out.

If you are thinking competition, then it boils down to the rules and weight/recoil. Here we balance the different factors depending on the task of the competition.

In unlimited 1000yd BR, 338's rule because you can build a 120lbs monster so recoil is not an issue.

For a Light varmint class, recoil becomes an issue so smaller cals are usually used.

Ideally, you want to use the highest BC bullet at the highest velocity launched by the least amount of powder all with the lowest amount of recoil that can shoot accurately enough to win.

Jerry
 
You must log in or register to reply here.
Back
Top Bottom