Is Faster or slower generally best?

[bruce m]

arnie,
you have gonr to the trouble of finding an ideal alloy.
if they were 30:1 or even 20:1 things might well be different.
chris,
i agree the it would be fantastic if the us govt were to do exhaustive work on this.
we as individuals just could not even think about that.
with regards b.c. as you describe i will have to get up to your paygrade.
do you know offhand the formula for b.c.?
i think alloy bullets are predictable when you get them right.
bruce.

[bruce m]

further to the above.
there is in commonwealth countries a discipline called match rifle.
it is shot at 1000, 1100, and 1200 yds with 308 only.
those guys absolutely shit themselves about transonic flight, often loading with 2 powders at once in an attempt to get the max muzzle velocity possible.
they use long throats, and use saami max chambers to increase case capacity.
one bullet they will not touch with a long bargepole is the 168 gn sierra matchking, because is wildly erratic when transonic, often tumbling.
the same bullet at 300 mt is absolutely deadly accurate.
the old sierra 190 gn matchking was a proven performer at 1200 yds, and had to go transonic due to low muzzle velocity in the small case.
jacketed bullets have their problems too.
just that most of their work is supersonic, and only in recent times have they had to work subsonically with ultral long range shooting becoming more popular.
in fact if you think of all the black powder rounds fired, most of them are travelling at some time transonically.
maybe we don't do too bad in comparison to jacketed smokeless on that basis.
bruce.

[beltfed]

Bruce, I have heard it is also called "Fullbore" rifle.
The club in Lodi,WI has "Fullbore" matches, out to 1200yds now
beltfed/arnie

[bruce m]

hi arnie,
in commonwealth countries, match rifle comes under the banner of fullbore.
the other part of fullbore is 300 to 900 yds, or 300 to 800 meters, depending on range layout.
the shorter range discipline is irons and sling, while match rifle allows a wrist rest and a scope or irons.
rifles are very similar to palma rifles.
bruce.

[beltfed]

Bruce,
Thank you for the update and clarification as to "match rifle' and "Fullbore"
I had heard the term "Fullbore" around Lodi used more recently.
Used to know it as simply "High Power rifle" to include Match Rifle/Palma rifle and Service Rifle
and more recently "F-Class".

It has been something like 15+ years since I have shot Service Rifle
and my Palma rifle. With jacketed bullets, that is. More recently I "play"
with the 30 cals with cast bullets.
beltfed/arnie

[bruce m]

you're welcome arnie.
is service rifle the same as across the course?
bruce.

[bruce m]

here is the formula for b.c.
b.c = mass divided by (drag coefficient x cross sectional area)
from this we can see that if we increase mass we increase b.c.
if we increase cross sectional area de decrease b.c.
from this we see that in the same calibre, the only way to increase mass is to make the bullet longer, the cross sectional area remaining the same.
smaller calibres simply cannot have the mass to have a high b.c. without being just too long to spin stabilize with any sensible twist.
increasing the drag coefficient will also reduce b.c.
i have yet to come to grips with drag coefficient, as it is more complicated. but suspect it goes up with drag
someone (chris?) might be prepared to elaborate on this.
\bruce.

[bruce m]

here is the formula for drag coefficient.
2 x drag force divided by (mass of air x flow speed squared x reference area)
coming to understand some of these terms in detail is taking some reading and thought.
(chris where are you?)
bruce.

[BFD]

While talking about drag and ballistic coefficients, you might look at this and read about its efficiency.

Looks remarkably like a Prolate BPCR bullet if I do say so myself...

https://www.cnn.com/travel/article/cele ... index.html

[beltfed]

Bruce,
Service rifle is generally shot "across the course", though
it is also shot at 600yds and long range prone matches as
its own category
beltfed/arnie

[gunlaker]

here is the formula for drag coefficient.
2 x drag force divided by (mass of air x flow speed squared x reference area)
coming to understand some of these terms in detail is taking some reading and thought.
(chris where are you?)
bruce.

Sorry Bruce. I've been focusing non-shooting stuff for a while. Here are the pages from McCoy's book "Modern Exterior Ballistics" that shows how drag is computed in a typical simulation. I use it for my software and it has generally been very good for calculating come-ups and differences between morning and afternoon air, or differences from one range to another based on weather and altitude.

The equation at the top right of this page is for calculating the drag force. You'll see that it makes no reference to the ballistics coefficient, but talks about a dimensionless drag coefficient. This is a function of velocity. I've included McCoy's tables for the various standard projectiles but you can find "better" ones on the internet. The second page, near the top defines the ballistic coefficient. It is not a fundamental part of the equation, but just a little mathematical convenience. If we had the resources we could make a new table specifically for say, a 540gr mini groove money bullet. McCoy's book gives specific tables for certain bullets like the .30 cal ball M2 projectile.

Chris.

[bruce m]

thanks chris.
woll have to read it a few times.
bruce.

[desert deuce]

Not intended to be criticism. Just a thought from another perspective.

Forced to make a plebian observation here: ocasionally............there is a difference between what should work and what does work.

With that in mind: When what does work conflicts with what should work by producing the superior result take what does work to the match.

Esoterica is no substitute for positive results in the crucible of competition.

[gunlaker]

Definitely Zack. But people need to understand that theory and measured results are not opposing philosophies. Theory tells you what things to test and how to test them. The results can confirm or reject a hypothesis, that's all. Reality is of course always correct.

I will say though, for reasonably massing, slow moving objects like our bullets, F=MA is absolute. Nothing even slightly hypothetical about it. The only room for significant error in the predictions of the computer model is in the dag curve data. And of course errors in writing code. This would also be the same with wind predictions. It's not that the theory isn't sound, it's just that it's impossible for us to collect the data. This is why, particularly for our big slow cast bullets, it's hard to look out at a range full of wind flags and use a computer to decide exactly how to stack them in the ten ring. This is also why BPTR is fun . I have spoken to a number of F-Class guys who claim that they can use their iPhones and Kestrels to make perfect first shots at 1000 yards. I suspect that, like always in the shooting sports, that there is a lot of b.s. in the air

Chris.

[bruce m]

good post chris.
bruce.