Ballistic Coefficient Question

[Broz]

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?

Well that kinda says it all right there. I think it is more of an owner pride thing that pushes the smaller caliber and imposes limits on the larger ones in an effort to keep them even.

We have many good choices out there. Almost unlimited. I say go for as big of a chambering as you will use to close to it's full potential. Anything the small caliber will do the big one will just do a little better.

Jeff

 

[Broz]

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).

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

PS and for the hi-lighted part of your post.

The 215 in the 300 win will out perform the 7 RM with a 168 or 180. Not as you state "as good" but in fact substantially better.

 

[Michael Eichele]

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).

Comparing two equal bullet weights and designs, you are not wrong. I've stated the exact same thing (this is my third time).

That's not our point. Our point is (as far as pure ballistic limitations) that a 7mm is not superior to any thing but a smaller caliber. OR the .300 is not superior to a larger caliber and so on.

 

[MontanaRifleman]

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).

Like everyone else has asked, why would you compare the same weight bullets in different calibers. Basically, you are comparing the 7mm long lean high BC bullet to the 308 short fat low BC bullet. Of course the 7mm bullet will have the advantage ballisitically in the long run. These bullets do not have the same form factor or SD and form factor with SD determine BC.

BTW, SD in itself does not determine BC. If you have a 180 gr bullet that is basically a cylinder with a flat nose and tail and has a great SD than a 150 gr bullet with long slender nose and boat tail, the lighter/lower SD bullet with the better form factor will perform much better than the heavier/higher SD bullet with a poor form factor.

That said, SD is an important factor in BC, but it must be combined with good form factor.

 

[sp6x6]

Well Im going back to your first post. I grew up hunting in NW MT , and have killed my fair share of Highwood bulls.I hung up my 7mm over 20 years ago,pushing it well past 500 then,went to 340 Wby in my early 20's.Now as mainly elk hunter I want the superior Energy at long range so I shoot the very high Bc berger 300, out of one of the what would be consider one of the smaller supermags-338 Norma. There are many more big 338's in the field now than back then,many didnt exist back then. My 7rm is loaned out to a friend of my sons, but I gave him a treat and let him shoot his first bull with my Norma at 550 yrds.

 

[1simplemann]

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.

I don't think I'm confused at all. Simply trying to confirm or unconfirm another person's opinion. Basically your explanation is in agreement w/ my friend's. He made a convincing case for shooting the 7MM. I may have stirred up a hornet's nest here w/ my question but it wasn't a which caliber question(7mm or 300WM?). Just a question on BC which I wasn't aware of before last week. I now have to make my decision on which caliber. I'm leaning towards 300WM because of the ability to shoot heavier bullets. I have not ruled out the Magnum 7mm's however. I shoot heavy arrows and fully appreciate the benifits of them. My only concern is recoil. I definitely don't want to shoot anything w/ a brake nor do I want to be undergunned. I'm looking for a balance of speed and power.Another thing to consider is that I really don't instend to shoot beyond 750 yds max. Preferbly under 600. I'm just not sure how much recoil I'm willing to put up with. I have a turkey gun that sits in the safe because it's NOT fun to shoot. It's a real turkey killer but tries to take your shoulder off. If I'm going to build gun I want one that is enjoyable to shoot. I don't another gun that sits in the safe. What I need to do is shoot someone else's gun or guns to get a better idea of what I'm willing to tolerate. Thanks for the response though. It helps.

 

[Broz]

I definitely don't want to shoot anything w/ a brake nor do I want to be undergunned.

You need to do exactly what is right for you. A rifle that fills all your needs. But let me offer that you check out todays offerings of a good side discharge brake like a JP tactical compensator, the Muscle Brake, Defensive Edge brake and so on.

Like bullets they have came a long ways in recent years. I assemble, set up and shoot many long range rifles. I would not want anyone that is serious about long range, a willing to make the commitment of practice it take to be good, to go into it shooting either a 7 mag or a 300 win without a brake. Comfort, accuracy, follow through and spotting shots are a huge benefit of a brake and the reason you see them on almost 100% of the serious long range rifles.

I see you are only a couple hours away from me. You have an open invitation to stop by and shoot one of my rifles. This might help you to know for yourself what is going on and what you need in the end. Just PM me if you are interested and we will set up a time.

Jeff

 

[Michael Eichele]

My only concern is recoil. I definitely don't want to shoot anything w/ a brake nor do I want to be undergunned. I'm looking for a balance of speed and power.Another thing to consider is that I really don't instend to shoot beyond 750 yds max. Preferbly under 600. I'm just not sure how much recoil I'm willing to put up with. I have a turkey gun that sits in the safe because it's NOT fun to shoot. It's a real turkey killer but tries to take your shoulder off. If I'm going to build gun I want one that is enjoyable to shoot. I don't another gun that sits in the safe. What I need to do is shoot someone else's gun or guns to get a better idea of what I'm willing to tolerate. Thanks for the response though. It helps.

And while I like to ruffle 7mm fans feathers, recoil is a consideration and yes, the 7mm RM offers a great balance of recoil and downrange energy. It does have a pretty good recoil to performance ratio. For a 600-750 yard rifle, 7mm are hard to beat.

I think I just get tired of hearing how 7mm is totally superior to the 30 caliber and I just find it gratifying to try and ground them. So I am sorry if I ruffled any feathers. He!! I'm getting ready to put a 284 win together. A bit more 1000 yard punch than my 308 with less recoil than my 300 and better barrel life than my 6.5x284.

Don't let us talk you out of the 7RM. If you can't handle the recoil of the 300s and wont use a break, they're hard to beat and you're preaching to the choir here. I can't handle a lot of recoil due to neck, shoulder and back injuries and I hate brakes too. I only keep my 300 because it shoots too good to get rid of or re-barrel. I only shoot it a few times a year and only hunt the largest game with it so I deal with it. Also, above all, I hate cooking barrels so naturally, I shy away from 7mm magnums. Its all a big conundrum really. Which qualities of each do you like or hate more? For me, I hate brakes and recoil but I also hate short barrel life. So its almost a toss up between a 7mm Mag and a 300 WM. Since I have the 300 WM, I jus stick with it.

Keep us posted as to how your 7mm comes along.

M

 

[1simplemann]

You need to do exactly what is right for you. A rifle that fills all your needs. But let me offer that you check out todays offerings of a good side discharge brake like a JP tactical compensator, the Muscle Brake, Defensive Edge brake and so on.

Like bullets they have came a long ways in recent years. I assemble, set up and shoot many long range rifles. I would not want anyone that is serious about long range, a willing to make the commitment of practice it take to be good, to go into it shooting either a 7 mag or a 300 win without a brake. Comfort, accuracy, follow through and spotting shots are a huge benefit of a brake and the reason you see them on almost 100% of the serious long range rifles.

I see you are only a couple hours away from me. You have an open invitation to stop by and shoot one of my rifles. This might help you to know for yourself what is going on and what you need in the end. Just PM me if you are interested and we will set up a time.

Jeff

Jeff , Generous offer that I may take you up on. Which rifles(calibers) do you shoot? I have a very good friend in Townsend. He's a Deputy Sheriff. He also invited me down for visit as well.

 

[1simplemann]

And while I like to ruffle 7mm fans feathers, recoil is a consideration and yes, the 7mm RM offers a great balance of recoil and downrange energy. It does have a pretty good recoil to performance ratio. For a 600-750 yard rifle, 7mm are hard to beat.

I think I just get tired of hearing how 7mm is totally superior to the 30 caliber and I just find it gratifying to try and ground them. So I am sorry if I ruffled any feathers. He!! I'm getting ready to put a 284 win together. A bit more 1000 yard punch than my 308 with less recoil than my 300 and better barrel life than my 6.5x284.

Don't let us talk you out of the 7RM. If you can't handle the recoil of the 300s and wont use a break, they're hard to beat and you're preaching to the choir here. I can't handle a lot of recoil due to neck, shoulder and back injuries and I hate brakes too. I only keep my 300 because it shoots too good to get rid of or re-barrel. I only shoot it a few times a year and only hunt the largest game with it so I deal with it. Also, above all, I hate cooking barrels so naturally, I shy away from 7mm magnums. Its all a big conundrum really. Which qualities of each do you like or hate more? For me, I hate brakes and recoil but I also hate short barrel life. So its almost a toss up between a 7mm Mag and a 300 WM. Since I have the 300 WM, I jus stick with it.

Keep us posted as to how your 7mm comes along.

M

That's just it, I don't have one nor have I made a decsion. Heck, my BnL still keeps telling me 300 WBY is the way to go and that the recoil isn't that bad. While still others insist that it's miserable to shoot W/O a break. I really love to shoot them all and compare. Hard to do w/ my busy schedule.

 

[Broz]

Jeff , Generous offer that I may take you up on. Which rifles(calibers) do you shoot? I have a very good friend in Townsend. He's a Deputy Sheriff. He also invited me down for visit as well.

There is a good chance your friend and I know each other.... In a good way of course.

My rifles I have set up for long range are a 6mm BR shooting 107 SMK's

My 300 win shooting 215 Bergers

And my new LRKM in 338 Terminator shooting 300 Bergers.

But I have access to a friends wife's 7mm Rem that I built shooting 168 Bergers.

Any of these rifles will pound into a small group at 700 +

Jeff

 

[gslinger]

Guys, I'm thinking about building a gun. Because who doesn't want a nice gun in their safe? Anyway, I've been researching, talking to a bunch of my customers that shoot. I had a conversation w/ my taxidermist. I mentioned that I was considering the 300 Win Mag. He mentioned the term BC and how I should take that into consideration before I choose a caliber. I understand the concept. Basically, Some bullets fly better than others. Makes perfect sense to me. Well he's a big fan of his Rem 7MM. He has a custom gun and the gun(his whole family uses it) has over 20 elk kills w/10 or 12 of them being over 500 yds. He explained to me that he shoots his w/ 180 gr Bergers at about 3020fps. His bullet has a higher BC than a simular 180 in 300 Win Mag. Even though the 300 win starts out faster than his 7MM, his berger's actually catch up to the 300 Win and at 500 yds his bullet has more energy left because of it's BC. Basically he said his setup shoots flatter w/ the same size bullet. This sounded plausible to me. I asked him where he got this info from. He said the guys at Gunwerks gave him the details. I even called his gunsmith and he said the same thing although he also said that I couldn't go wrong w/ either caliber. Is this the real deal? Hard to argue w/ success. If so, I may have to look at the 7mm's. I'm not a huge fan of recoil so a gun that's a killer AND enjoyable to shoot would be a plus in my book.

I was trying to give the op an easy understanding of bc's and sd's(like it was explained to me),sounded like he didn't understand the concept.
When he sees bc and sd while making his bullet selection.
He will have an understanding of the concept of what they mean.
That is the only reason i used 2 different calibers of the same wieght.
I thought the huge difference in bc's and sd's would be easier to understand.
And to show him how important bc's numbers are, i should add,even in the same caliber.
It also sounded like he needed an opinion(i might have pushed my favorite
caliber a little hard on him).

(I don't think I'm confused at all.)

I'm sorry, i read and misunderstood your post.

( Simply trying to confirm or unconfirm another person's opinion).

Bc's are science, not opinions,you really need to understand how they will affect barrel twist.

Maybe ,i read that wrong too?
Have a nice day,

 

[mrb1982]

I think the main facts of BC were pretty much covered in the first few posts.

I am a 7RM shooter. When I bought it, it was becasue it was easy to find components, cheaper to shoot than some of the real super big mags, and still does everything I need it to do.

If I were to do it all over again, it would be a 300 win mag. The 300 RUM is extremely enticing to me, but just can't decide if I want to use all that extra powder, all that extra recoil, and more expensive to shoot for a few more feet per second over a 300 win.

For me, I will probably turn my sendero into a 7mm/300 win, shoot the 180's with a little more smoke, and probably deal with it until it is time for a rebarrel and then decide what I want to do. I think the 7mm/300 would give me just enough more energy for that added pop out long that the 7RM might struggle a little more with. Just my experiences coming from a 7RM guy. Great rifle, excellent caliber, but..............the 300 win just takes all the questions away.

 

[cowboy]

.Another thing to consider is that I really don't instend to shoot beyond 750 yds max. Preferbly under 600. I'm just not sure how much recoil I'm willing to put up with.

With the criteria you have laid out above and no desire to use a brake I think both the 7 and 300 wm are way more than you might need.

If I was you I'd be looking at one of the 6.5's. Shoot the heavy for caliber bullets and it'll take anything within your "preferably under 600" or "750 yds max" range. They are pleasant to shoot, very manageable recoil and probably cost 3/4 of the 7 or 300 per round fired. And besides that - I would not consider you under gunned for anything that we have here in Montana.

No matter what you decide, I would not pass up on Broz's offer to get together. Once you've played this LR game for a while, 750 yds. soon becomes a chip shot if you stay with it. That was very thoughtful of Broz.