Ballistic Coefficient Question

[Broz]

Not at all Michael, I just wanted to state what I have found and that is Berger 99% of the time, has been spot on for me with BC's.

By the way, I agree with you and Mark that the 7 RM will never out preform a 300 win in any way when current heavy offering for both are used. I have nothing bad to say about a 7 RM, just stating facts and I have been attacked for stating this before from self proclaimed experts in la la land.

Jeff

 

[Broz]

You know you want a .375 Jeff

PS sorry for getting even further off topic.

Almost, but not yet. When the bullet technology catch's up for the 375 I will have to.

jeff

 

[mrb1982]

I agree with everything said here basically. good stuff. I own a 7RM but if I were to do itall over again and know what I know about bullets and ballistics now, I would have bought a 300win mag.

 

[paphil]

I really like both the 7mm and the 300win mag as long as they are shooting heavy bullets! It almost makes me want to cry when I see all the light bullets that are available . Yes, they shoot fast but the wind drift and energy down range are major reasons to not shoot them. Stick with the heavy for caliber bullets.

 

[1simplemann]

Wow, Thanks for the responses! I spent the day skiing and come back to 3 pages! So, at the end of day the answer is "No the 7mm does not catch up to the 300WM after 500 yds? What about some of the hotter 7mm rounds such as the STW?

 

[Broz]

Wow, Thanks for the responses! I spent the day skiing and come back to 3 pages! So, at the end of day the answer is "No the 7mm does not catch up to the 300WM after 500 yds? What about some of the hotter 7mm rounds such as the STW?

No it does not.

If you wish to go hotter with a 7mm there will always be a hotter 30 cal as well to be fair in the comparison.

Not to say any of these are a bad choice, but as you go larger case the smaller diameter bore will suffer from shorter barrel life.

Here is a great comparison. I have built three 7mm-300 wins. This is simply a 300 win necked down to 7mm. Shooting the 180 Berger from the 7mm/300 win and comparing it to my straight 300 win with a 215 Berger. I am still choose the 300 win. But like I stated before, if the Berger 7mm 195 does come about and has a BC of .750+ I probably will be switching back to a 7mm-300.

Jeff

 

[Lefty7mmstw]

No it does not.

If you wish to go hotter with a 7mm there will always be a hotter 30 cal as well to be fair in the comparison.

Not to say any of these are a bad choice, but as you go larger case the smaller diameter bore will suffer from shorter barrel life.

Here is a great comparison. I have built three 7mm-300 wins. This is simply a 300 win necked down to 7mm. Shooting the 180 Berger from the 7mm/300 win and comparing it to my straight 300 win with a 215 Berger. I am still choose the 300 win. But like I stated before, if the Berger 7mm 195 does come about and has a BC of .750+ I probably will be switching back to a 7mm-300.

Jeff

yup...
where my 7stw goes my 300 rum will do the same with a heavier pill, where my 7rum goes a 30-378 (or similar) will do the same with a heavier pill, etc., etc.. Step up again to 338 and the 30's get whooped. You've got to know what you need for the game you intend to play.
For Broz and a few of the others that go well past 1,000 yards you need about the best bc pills out there in a stable, accurate chambering. I'm still screwing around with bullets I bought years ago but I'm migrating to heavy hpbt's as I upgrade my rifles. I still haven't drunk the Berger kool-aid, but I think my 7rum may want some 180 Bergers and rl50 to play with.

 

[gslinger]

Wow, Thanks for the responses! I spent the day skiing and come back to 3 pages! So, at the end of day the answer is "No the 7mm does not catch up to the 300WM after 500 yds? What about some of the hotter 7mm rounds such as the STW?

I think you have it a little confused,here is how i understand it.
Most of my research comes from this site and 6mm br and custom builders.
I did a lot of research (finding the science behind it).
If im wrong i hope someone will correct me.
Ballistic coefficient and sectional density are everything.
The higher the bc and the sd,the less drag and wind deflection,on the bullet.
Berger makes a 168g vld for both.i'll compare themm
A 7mm rem mag shooting a 168g berger vld (BC of .617 and sd of .320) and a 300 win mag shooting a 168g berger vld (bc of .473 and sd of .271)
The 7mm will out preform 300 win mag.
The higher bc of the 168g 7mm will catch and pass the low bc of the 168g .308.
By 600 yards,the 7mm should be going faster.
The greater drag on the .308 will slow it down geometrically
By a 1000 yards the 7mm will have passed it.
By 1400 yards the .308 win mag will no longer be super sonic and will
lose accuracy.
The 7mm will be super sonic to 1900 yards.
Even at 600 yards the higher sd of the 7mm should give you better penatration than the low sd of the .308.
To get a 300 win mag to preform as good as a 7mm rem mag,you will need a 215g berger vld.
You might have feeding issues with long 215 vld and have to seat deeper in the case,and will lose powder capacity.
Having to use a heavy 215g bullet will increase recoil.
My research say's with proper parts you can get the 7mm recoil
down to a 243 recoil
7mm;s usually out preform thier counter parts.
7 08 and 308 - 280 and 3006 - 7mm and 300 win mag.
Long distance records held by 6mm are dropping like flies to the 7mm's.
The 7mm berger in 180g hybred is even better,crazy high bc.
The 7mm stw can hold it's own against any .308,but you gain a lot of recoil.
I'm building a 7mm rem mag, here are my parts.
Howa 1500 action.
Benchmark 1 in 9 twist 30 inches.
Nightforce picatiny rail.
Ior steel rings.
Nightforce nxs 3.5-15x56 with zero stop.
laminate thumbhole tactical stock.Ajustable butt and cheek.
The only part missing is the Kirby allen painkiller muzzle brake(3 port slab),his e-mail said i could order now.
Well that;s my two cents.

 

[Broz]

This is the problem when comparing a 7mm RM and a 300 win Mag. Some wish to use the same weight projectiles. That is tipping the table to favor the 7mm. They are two different bores, they are not the same, so why handicap the 300? I say lets use some of the largest , highest BC bullet commercially available for both. Which ever complements each caliber, the best choice available for both. Like the 180 for a 7 and the 215 for the 300. We are talking about long range ballistics here. This is where higher BC's pay off. So why, when talking long range would anyone load a 168 in a 300 win? Maybe years ago when we didn't have the great selection we do today, but today the 300 win mag at long range will retain more velocity, have more energy and less wind drift than a 7 Rem Mag. Why would any owner of either caliber, that was wanting the best long range performance, choose a lighter lower BC bullet for either? They wouldn't.

As for recoil, put a JP tactical compensator of either rifle and let even the kids shoot it. I took a 13 yr old girl in for her first elk this year. She shot my 300 win with a 215 Berger. I had her dry fire a few times then she stoned her elk at 601 yards. After, I asked how the recoil was compared to her 243. She replied "there was no recoil"

Jeff

 

[Broz]

The 7mm will out preform 300 win mag.
(No, not unless you handicap the 300 with a light for caliber bullet to tip the table toward the 7 Rem).

By a 1000 yards the 7mm will have passed it.
By 1400 yards the .308 win mag will no longer be super sonic and will
lose accuracy.
(Only again if you choose to handicap the 300 with a 168 that no one will shoot for long range, use top performing bullets for both and the 300wins by a large margin)

Even at 600 yards the higher sd of the 7mm should give you better penatration than the low sd of the .308.
(But use a High SD choice for the 300 and then look at the difference. I have drove 210's clear through bull elk at 1000 yards with my 300 win)

To get a 300 win mag to preform as good as a 7mm rem mag,you will need a 215g berger vld.
(No, not "as good" far better that the 7RM. But I am glad you understand this part and support my statement that the only way to get a 7 RM to out perform a 300 win is to handicap the 300 win with an unreasonably light low BC bullet)

You might have feeding issues with long 215 vld and have to seat deeper in the case,and will lose powder capacity.
(Nope, the 215 has fed fine from every 700 Rem we loaded them in with standard mag boxes. Plenty of case capacity there and this proves your lack of experience with a 300 win and a heavy bullet)

Having to use a heavy 215g bullet will increase recoil.
(easily dealt with using a good brake, and the 7 will be nicer to shoot with a brake too)

My research say's with proper parts you can get the 7mm recoil
down to a 243 recoil
(So you again choose to use a brake for the 7 but not the 300,,,)

7mm;s usually out preform thier counter parts.
7mm and 300 win mag.
(not true if best components for both are used)

Long distance records held by 6mm are dropping like flies to the 7mm's.
(Not sure about that, but What about all the records held by the 300 win?)

The 7mm berger in 180g hybred is even better,crazy high bc.
( but still substantially less than the 300's 215 or 230 offerings)

The 7mm stw can hold it's own against any .308
(BS, the 7 stw is an awesome round but did you forget the 30-378 Weatherby, 300 RUM or many other wildcats?)

You stated "If im wrong i hope someone will correct me." My replies and facts are in parenthesis after your statements.

I will race my old mountain trail horse against the fastest dragster if you will only allow the dragster to use bicycle tires on the rear.

Jeff

 

[Michael Eichele]

I think you have it a little confused,here is how i understand it.
Most of my research comes from this site and 6mm br and custom builders.
I did a lot of research (finding the science behind it).
If im wrong i hope someone will correct me.
Ballistic coefficient and sectional density are everything.
The higher the bc and the sd,the less drag and wind deflection,on the bullet.
Berger makes a 168g vld for both.i'll compare themm
A 7mm rem mag shooting a 168g berger vld (BC of .617 and sd of .320) and a 300 win mag shooting a 168g berger vld (bc of .473 and sd of .271)
The 7mm will out preform 300 win mag.
The higher bc of the 168g 7mm will catch and pass the low bc of the 168g .308.
By 600 yards,the 7mm should be going faster.
The greater drag on the .308 will slow it down geometrically
By a 1000 yards the 7mm will have passed it.
By 1400 yards the .308 win mag will no longer be super sonic and will
lose accuracy.
The 7mm will be super sonic to 1900 yards.
Even at 600 yards the higher sd of the 7mm should give you better penatration than the low sd of the .308.
To get a 300 win mag to preform as good as a 7mm rem mag,you will need a 215g berger vld.
You might have feeding issues with long 215 vld and have to seat deeper in the case,and will lose powder capacity.
Having to use a heavy 215g bullet will increase recoil.
My research say's with proper parts you can get the 7mm recoil
down to a 243 recoil
7mm;s usually out preform thier counter parts.
7 08 and 308 - 280 and 3006 - 7mm and 300 win mag.
Long distance records held by 6mm are dropping like flies to the 7mm's.
The 7mm berger in 180g hybred is even better,crazy high bc.
The 7mm stw can hold it's own against any .308,but you gain a lot of recoil.
I'm building a 7mm rem mag, here are my parts.
Howa 1500 action.
Benchmark 1 in 9 twist 30 inches.
Nightforce picatiny rail.
Ior steel rings.
Nightforce nxs 3.5-15x56 with zero stop.
laminate thumbhole tactical stock.Ajustable butt and cheek.
The only part missing is the Kirby allen painkiller muzzle brake(3 port slab),his e-mail said i could order now.
Well that;s my two cents.

Equal bullet weights and equal form factors, smaller calibers win. You're right there.

Maximum potential always goes to a bigger caliber.

Comparing the 260, 708, 308, they all have equal windage abilities. Apples to apples lets use the 140 amax, 162 amax and 208 amax at realistic velocities. 2750, 2700 and 2600. Using published BCs which are close (at least to 600 yards, all a but less at 1000), you'll see that the windage is nearly identical. The energy goes up as the caliber gets bigger. The trajectory between the 260 and 308 is only 20" different at 1k. If all you cared about was trajectory, you can run 155 grain pills at 3000'sec in the 30 version which a 260 can't touch until you drop to 120s.

Again though, the recoil goes up with the bigger bore but so does the down range performance. Barrel life goes up as well. Barrel life for me is more important than some added energy. I do a lot of shooting and grow tired of cooking my trusted and sweet barrels.

 

[Broz]

Comparing the 260, 708, 308, they all have equal windage abilities. Apples to apples lets use the 140 amax, 162 amax and 208 amax at realistic velocities. 2750, 2700 and 2600.

I agree Michael, and just to keep things clear to all readers, when you list "308" above you are referring to the 308 Winchester chambering not a .308 caliber 300 Winchester Magnum chambering. Correct?

Jeff

 

[Michael Eichele]

I agree Michael, and just to keep things clear to all readers, when you list "308" above you are referring to the 308 Winchester chambering not a .308 caliber 300 Winchester Magnum chambering. Correct?

Jeff

In my above illustration I'm comparing the 260 Remington to the 7mm-08 Remington and the 308 Winchester. All the same case and comparing heavy for caliber bullets. The same example can be used for the 264 win, 7rm and 300 win.

I usually catch a lot of flack comparing these calibers and how close they really are. Because hey, we all know smaller calibers are superior to larger ones right?

 

[gslinger]

To get a 300 win mag to preform as good as a 7mm rem mag,you will need a 215g berger vld.

COMPARING BC AND SD OF THE TWO 168g PROJECTILES.
Could you tell me where in my post i was wrong.
Is my understanding of how bc and sd work wrong.
You have not corrected anything i said,accept to say a 215g will make
the 300 equal or better.
I have said that
To get a 300 win mag to preform as good as a 7mm rem mag,you will need a 215g berger vld.
Which one of my points are wrong (not how it works).