171gr .243 @ 3300 FPS?

[SN13]

I calculated that a 171gr .243 bullet would have a BC of about .800

To get it at 3300 fps you'd need to neck down a .300 Rem Ultra Mag.

It sure would be a long bullet.

What's the best BC of standard loads in a 6 to 7mm projectile going at 3000+ FPS?


Need Cartridge and BC.

Looking for a fast long range bolt action. I just can't find a .243 Rem Ultra Mag with 171gr. Bullets


Also, a 215gr 6mm (.243) bullet would have a BC of over 1.0 .... do you create black holes at that point?

 

[dakotasin]

custom bullet makers can/will do whatever you want. there is one out of canada that is producing some 160 grain 257 bullets for example.

also, this is not as simple as necking down a bottle of powder and letting it buck. for instance, my 7 rum does not generate the velocity you would think it should. 100 grains of powder is a lot of powder to get out of that tiny hole... powder burn rates are also a huge factor.

all that said, my suggestion for you is to go the other way. look at a 338-300 rum (300 rum case necked up to 338 - the 338 rum case is actually smaller than the 300), 408 chey-tac, etc.

for bc's... 338 then 6.5mm then 7mm. after that, i'm not sure what the order is. i would imagine the 6's and 257's are good, and the 30 cal is probably right after the 257...

long range shooting is not a pure velocity game. it is more of a bc game.

good luck!

 

[JesseL]

Velocity is a function of something like:

(pressure * bullet diameter)/bullet weight


Even with a necked down .300 RUM, you'd need an exceptionally long barrel and ridiculously slow powder (and probably a fair amount of freebore too) to get much velocity out of a bullet that heavy-for-caliber.

 

[gvnwst]

Looking for a fast long range bolt action. I just can't find a .243 Rem Ultra Mag with 171gr. Bullets

try a 7mm WSM with 168 or 180gr bergers. .648 bc. or a 6.5 with 140gr bergers @.640bc.


if you want the highest possible BC, look up lutz moller. he is a german ballistican who makes some SUPER high bc bullets. like a 1.700 bc 50 cal one. normal weights, just made of lighters metals than copper and lead, his are a copper tin mix i think.

the bullets can run up to $3.00 apice, so be careful. his also require special barrels.

 

[Vicious-Peanut]

Talk about overbore!

 

[plinky]

This would be a text book application for a sabot round. I don't know if anyone has gotten the needed accuracy from a sabot in smallarms. Ideally it should be fin stabilized from a smoothbore barrel.

 

[JesseL]

This would be a text book application for a sabot round. I don't know if anyone has gotten the needed accuracy from a sabot in smallarms. Ideally it should be fin stabilized from a smoothbore barrel.

Good points.

A bullet that long would need a crazy fast twist to spin stabilize, and of course a twist that fast would make it even harder to realize the desired velocity.

 

[gnut]

High Bc

That's right, just give up you can't get any better than 30-30. But if you wanna keep banging your head against the ballistics computer wall, 338 sierra 300 grain is high BC.
.308 240 grain
.264 142matchkings, 140 Berger VLD
.243 105 berger Etc, there are tons of 6's that would be cool.
I like that idea of high bc/fast launch/accurate bolt/ long range rifle.
6mm/284 105 berger at around 3k or more.
But I have come to realize the point is to hit the target/make small groups.
If drop is the issue then your pushin a rope.
If wind is the issue you have everything to gain.
Accuracy I believe is paramount but drift due to wind is the hardest to read and while not easy or simple can be reduced with this pencil in the wind technique. Ammoguide.com is a neat tool I use to research Bc's and loads.
I have kinda settled on .243 winchester, but, I like all the super fast 6mm/50bmg ideas. Don't let the naysayers get you down.
Gnut

 

[JesseL]

I hope I didn't come across as naysaying. I just believe that it's important to understand the rules before you try to break them.

 

[younganddumb]

noob question what is BC?

 

[gvnwst]

ballistic coefficent. how aerodynamic something is. the higher the number, the better. not to be confused with coefficent of drag, in which the lower the number, the better

 

[JesseL]

noob question what is BC?

http://en.wikipedia.org/wiki/Ballistic_coefficient

In a nutshell, it's a measurement of how aerodynamic a projectile is. A higher ballistic coefficient bullet will retain its velocity longer than one with a lower coefficient. This in turn relates to how much the bullet will drop or be effected by crosswinds at extended ranges, as well as how far it can retain its terminal effectiveness for hunting or warfare.

 

[younganddumb]

ok thanks so you want the highest BC lowest drag and a good weight to have a great bullet right?

 

[gvnwst]

yes, that about sums it up, except that the heavier bullet for a certain diameter, the higher sectional density, think of throwing a beach ball compared to a stone the same size. at around the same velocity. the beach ball has a lower SD, and will lose velocity faster.

 

[NCsmitty]

The 115 gr. DTAC has a .585 ballistic coefficient @ 2850fps+, and is as good as it gets without going to specialty custom bullets in 6mm, as far as I know.

http://www.6mmbr.com/catalog/item/1308478/799896.htm

NCsmitty

 

[akodo]

ballistics is never simple, necking up and down is mechanically easy, but what goes on inside can change a lot.

For starters, a principle in hydrolics is that a wider based piston is more efficient, less wasteful than smaller ones. Same with bullets, pushing on a wide base is more efficent. Using the same charge and say 200 grains, a 30 cal vs a 25 cal, the 30 cal will come out a bit faster, but of course the 25 cal will cut through the air better.

But also when necking down, say you have the 300 RUM and are necking it down to .243 as you suggest, to acheive higher velocities, but that also translates to less time in the barrel, so less time for the powder to burn, more wasted powder being burned after the bullet leaves.

Further, a short powder column burns better than a longer one.

Sticking a smaller bullet on the same stack of powder will never give you the results you want.

Sure, you may develop a real fun toy, but there would be a ton of load development to do.

 

[MachIVshooter]

ok thanks so you want the highest BC lowest drag and a good weight to have a great bullet right?

Depends what you want to do with it. For punching holes in paper at long range, yes, the highest BC bullet is preferable. But for a guy hunting big bears in heavy woods, a bullet that will be fast and accurate at 1,000 yards may not serve his purpose as well as a slower, heavier pill with a large meplat.

 

[SimpleIsGood229]

Are you actually Nolo posting under a different user name?

What kind of twist rate would be required for such a bullet? 1:5?

 

[gvnwst]

if you are talking to the OP, i don't think Nolo would try something like this.

and it would be more like 1:1.5

 

[Dr. Tad Hussein Winslow]

try a 7mm WSM with 168 or 180gr bergers. .648 bc. or a 6.5 with 140gr bergers @.640bc.


if you want the highest possible BC, look up lutz moller. he is a german ballistican who makes some SUPER high bc bullets. like a 1.700 bc 50 cal one. normal weights, just made of lighters metals than copper and lead, his are a copper tin mix i think.

the bullets can run up to $3.00 apice, so be careful. his also require special barrels.

This is good advice. Typically, ASIDE from .50 BMG which has the best ballistics bullets, by far, the best BC/weight ratios are from 7mm bullets, followed closely by 6.5mm bullets and .338 bullets. Since .338 will beat you up an awful lot in recoil and expense, look at rounds in 7mm or 6.5mm, such as the 6.5-284 Norma, 7mm Rem mag, 7mm WSM, 7mm Dakota, 7mm STW, 6.5mm-'06, .264 Win, etc., if you want some smokin hot laser-like trajectories at very long ranges, with *reasonable* recoil and non-custom bullets (from the likes of Sierra, Berger, Lapua, etc.). Then, if you ALSO want to add long barrel life to the mix as practical shooters do, then you'll end up with a 6.5 Creedmoor or .260 Rem.

 

[gvnwst]

Typically, ASIDE from .50 BMG which has the best ballistics bullets, by far

actually, of all current cartridges, the .416 barrett is best. it edges out the .408 by a hair.

7mm bullets, followed closely by 6.5mm bullets and .338 bullets.

.338, .300, 7mm, 6.5 in that order. a 300gr .338" SMK has a bc of .711, and a 240gr .308" SMK has around the same.

Then, if you ALSO want to add long barrel life to the mix as practical shooters do, then you'll end up with a 6.5 Creedmoor or .260 Rem.

don't forget the 6.5x47 lapua

 

[Dr. Tad Hussein Winslow]

OK, but apples & oranges:

Best BCs, period: .338, .300, 7mm, 6.5mm - can't argue with that.

But best BC - to - weight - ratios (as I said) go to 7mm, then 6.5mm, then .338, then 6mm, then .300/.308. 7mms have very high BCs at lowish weights, making the ratio superior and thus overall performance superior. Ditto on 6.5. .338s and .300s with high BCs are so danged heavy that their velocity stinks. Whereas you can crank a 129 gr 6.5 or 145-150 gr 7mm much much faster with *almost* as good of a BC, and far superior to the BC of a .300 or .338 with same velocity.

SeewhutI'msayin? Oh yeah, forgot about 6.5x47mm.

 

[gvnwst]

a berger 140gr match has a bc of .509. it takes above 160 (hornady AMAX, 162gr, berger VLD 168gr) to get really good bc with 7mm bullets. now, compared to 30 cal bullets, that is great, and if you need the energy, but a 140gr berger 6.5mm has a bc of .640. in a 6.5 creedmoor, launchig that puppy at 2,800, that is a great load.

i agree about the weight to bc raitos, but it is 6.5, 7mm, 6mm, then .338, .300

 

[Dr. Tad Hussein Winslow]

OK, I'll buy that. But 6.5 and 7mm are essentially a tie.

Myself? Yes, the Savage 12 F Class PTR *IS* on my list of "stuff to get within a year" - and it's in 6.5-284 Norma, and I plan on shooting it at 600 yards, which we have at one gun club here.

 

[gvnwst]

yeah.