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Best bullet weight for 300rum

 
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  #1  
Old 01-10-2009, 04:54 AM
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Location: Canberra, Australia
Posts: 111
Best bullet weight for 300rum

Ok I have been punching some numbers here.
JBM - Calculations - Trajectory
and I'm struggling to work out why I should use anything heavier than a 150 grainer.

I'm not a physicist but I'll try anything once.

Due the fact that as the bullet gets heavier the speed gets lower I end up with less energy.

Since the barnes TSX retains most if not all of its weight as it passes through the target animal. Doesn't this mean all the energy will be transfered to the target until the bullet eventually stops.

I understand that I heavier bullet penitrate more but concidering that the surface area of the bullet is .3". The only resistance is the frontal area of the bullet. To calculate how far anything will travel I would have thought the formula would be something like energy minus resistance irrelivant of weight.

Anyway.

130 grain, muzzle vel 3700 ft/sec = 1000 meters vel 1205 ft/sec = 419 ft/lbs
150 grain, muzzle vel 3450 ft/sec = 1000 meters vel 1395 ft/sec = 648 ft/lbs
168 grain, muzzle vel 3350 ft/sec = 1000 meters vel 1249 ft/sec = 582 ft/lbs
200 grain, muzzle vel 2950 ft/sec = 1000 meters vel 1136 ft/sec = 573 ft/lbs

And as far as I can tell it's all down hill from there.

The 150 grainer also has the shortest flight time.

I have had a little experience with formulas for vehicle accidents and skid distances calculating speed. The formulas used for this don't consider the weight of the vehicle but the friction increases in line with weight due to gravity but this obviously isn't a consideration in bullet penitration.

Anyway thoughts please.

Last edited by joel0407; 01-10-2009 at 05:57 AM.
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  #2  
Old 01-10-2009, 09:50 AM
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Join Date: Mar 2007
Location: Montana
Posts: 1,325
Re: Best bullet weight for 300rum

I'm not sure if your velocities are quite right. Out of a 300rum you should be able to run a 200g Accubond @ 3150fps or so. You should be able to push the 180g E-tip to about 3400fps.

Here is my calcs. from JBM @ my elevation 3000ft:

180 E-tip @ 1000yrds
muzzle vel= 3400fps
-19moa drop
5.3moa wind
1860fps
1382 ft lbs

200 Accubond @ 1000yrds
muzzle vel= 3150fps
21.3moa drop
5.1moa wind
1824fps
1478 ft lbs

It is at about a 1000yrds that the Accubond starts to out run the E-tip. So depending on how far you plan to shoot, I would choose the 180 E-tip.

Steve
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  #3  
Old 01-10-2009, 10:37 AM
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Location: AB, Canada
Posts: 549
Re: Best bullet weight for 300rum

hi joel,

you forget the wind!
past 500yrds for 300 rem ultra mag bullets you have to calculate the wind deviation.
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  #4  
Old 01-10-2009, 03:01 PM
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Join Date: Dec 2008
Location: Canberra, Australia
Posts: 111
Re: Best bullet weight for 300rum

Quote:
Originally Posted by RockyMtnMT View Post
I'm not sure if your velocities are quite right. Out of a 300rum you should be able to run a 200g Accubond @ 3150fps or so. You should be able to push the 180g E-tip to about 3400fps.

Here is my calcs. from JBM @ my elevation 3000ft:

180 E-tip @ 1000yrds
muzzle vel= 3400fps
-19moa drop
5.3moa wind
1860fps
1382 ft lbs

200 Accubond @ 1000yrds
muzzle vel= 3150fps
21.3moa drop
5.1moa wind
1824fps
1478 ft lbs

It is at about a 1000yrds that the Accubond starts to out run the E-tip. So depending on how far you plan to shoot, I would choose the 180 E-tip.

Steve

Sorry mate, I'm only quoting velocities from ADI powder loads.

I'm about halfway there saving for a Sendero II in the 300rum with a JP brake, I should be ordering in about a month or so. I'm just working out what I'll be loading. My next post will be deciding on what power Night Force scope.
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  #5  
Old 01-10-2009, 04:14 PM
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Location: The rifle range, or archery range or behind the computer in Alaska
Posts: 3,418
Re: Best bullet weight for 300rum

Yeah your numbers are VERY conservitive. You can safely get 3100-3200 FPS out of a 200 grainer. Sierra game king is .560 on the BC and the 200 AB is .588. These will offer around 1300 FPE at 1000 yards in standaard air conditions. I am getting 3000 FPS with a 220 SMK and at 1K offers 1400 FPE with its mean BC of .630. The 180 AB I am getting 3300+ FPS. This is getting me over 1050 FPE at 1K. The 150's are only offering me less than 800 FPE at 1K. You question why use anything more than the 150's? Most would question why use anything less than a 180-200 in this cartridge. 30 cal 150's with their low sectional densities arent well suited for long range elk or moose. The 180's and 200's+ are very well suited as well as their energy levels are 1.5-1.75 times higher than the 150's. These of course are real word results here not "paper" ballistics.
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Quote:
Originally Posted by Broz View Post
Please just answer one very simple question. Why would anyone shooting long range load a low BC , low SD 168 gr offering in a 300 win???????

My answer to this is. The only reason is to make the 7 RM look good. There is no other reason.

Jeff.
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  #6  
Old 01-10-2009, 10:37 PM
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Join Date: Jul 2004
Location: Texas
Posts: 5,192
Re: Best bullet weight for 300rum

jOEL

I think your velocitys are a little slow also but keep in mind that velocity is not everything.

Wind drift and long range trajectory depend a lot on ballistic coefiecent for optimum
performance so I would also recomend 180 to 200gr bullets for all around performance.
in the big 300RUM.

Run the tables out to 2000 yards and I think you will see the trend of heaver bullets.

If you were shooting a 308 then the 150 to 170gr bullets would be correct.

Also at the point of impact the heaver bullet has more momentum to achieve better
penetration and expansion.

I allways like to look at the required energy to bring down the game to be hunted ( I know
that taylor knock out values are just a guide line ) but it's a place to start.

Example: A white tail deer . 1000 ft/lbs of energy is recomended (not required ) an elk would
be 1500 to 2000ft/lbs . so I look at the maximum distance the round will acheave that energy
with minimum trajectory and wind drift . That gives me something to start with as far as
bullet weight.

I hope this helped
J E CUSTOM
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  #7  
Old 01-18-2009, 01:27 PM
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Join Date: Nov 2001
Location: Wyoming
Posts: 92
Re: Best bullet weight for 300rum

As posted, it's not so much about flight time and drop as it is wind bucking ability. Drop is pretty easy to compensate for, just plug your distance and such into a ballistics program along with all the other required fields and put in your clicks. Windage is not an exact science though. It's a best guess based on wind speed and direction where you are and what speed and direction you think it is down range. The higher the BC, the less effect your miss-guess has on the impact point. For fun, check the impact difference between a 15 mph full value cross wind and a 12 mph cross wind from 2 O'clock. Run that test on several different bullets and you'll see what I mean. Lighter bullets can realize twice the effect of a heavier, high BC bullet.
All that said, I'm falling all over myself to take my new 208gr Hornady A-Max bullets and try them in my 300 Wby when the snow melts!

Coyoter
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