Highest measured BC on a .45 cal bullet

[gunlaker]

Just some rainy weather pondering...

What are the highest measured BC's you've seen for a .45 cal bullet?

Richard Gunn listed the NEI # 349-C Gunn Seacant RN as having a measured G1 BC of 0.51.
Dan's numbers for the .45 money bullets were between 0.5 and 0.55 depending on the weight and groove design ( or no grooves, i.e. PP ).

When shooting the BACO 458535M and BACO 459530M4 using an estimated G1 BC of 0.5 matches the trajectory quite well (although the bullet shoots a few minutes flatter between 800 and 1000 than the G1 trajectory predicts, but this is expected).

I think the elliptical bullets may be a small improvement but I've never seen data and haven't personally shot an elliptical past 300 yards.

Chris.

[firefighter1990]

I'm having a mould made by Steve Brooks that's based of Harlan Sage's design that I tweaked a little bit in the nose geometry. I'm having it built up for my 17 twist 45-100 that shoots an equivalent ppb at 1375 fps.

This bullet is of the tapered micro mini grooved design. 1.55" long and will weigh 570 grains. Harlan estimates the bc to be around .6

[bruce m]

chris,
interesting how you relate money vs ellipyical b.c.
i have an elliptical and a money that when started at 1300 fps track each others' trajectories out to about 700.
after that the elliptical has noticeably less drop out to 1000, the max range shot at.
at about 600 to 700 these bullets go from transonic to fully subsonic, suggesting that the elliptical has lower drag characteristics when subsonic.
good bullets for regular barrels in 40 and 45 cal seem to be able to exceed 0.5, but not by much, say 0.51 or 0.52 max, based on muzzle velocities and trajectories in firing tests.
you really need to take into account sight radius in determing comeups and moa which most programmes use.
firefighter,
i hope you get 0.6 b.c, but doubt that it will be much over 0.550.
i also hope that you do not get stability issues in horrible winds.
personally, 1.460 is max length for 18 twist, and 1.50 is max for 16 twist.
0.050 over length will still work well at shorter ranges.
keep safe,
bruce.

[gunlaker]

I've been running some numbers this morning to compare fast ( 1375 fps ) loads vs slower ( 1275 fps ) which is basically the velocities I see in my .45-100 ( .45-2.6 ) vs .45-70. Mostly to look at how 1000 yard vertical is (theoretically) affected by changing headwinds. Ultimately it looks a little bit better to stay at 1375 fps and go from a 0.5 BC to 0.55 BC than it is to stay at 0.5 and move up to 1375 fps.

Regardless of what is done, you pretty much end up increasing recoil to gain something like a 10% advantage. We are in the zone of diminishing returns with the big boomers.

Just something to occupy the mind on a non-shooting day .

Chris.

[firefighter1990]

chris,
interesting how you relate money vs ellipyical b.c.
i have an elliptical and a money that when started at 1300 fps track each others' trajectories out to about 700.
after that the elliptical has noticeably less drop out to 1000, the max range shot at.
at about 600 to 700 these bullets go from transonic to fully subsonic, suggesting that the elliptical has lower drag characteristics when subsonic.
good bullets for regular barrels in 40 and 45 cal seem to be able to exceed 0.5, but not by much, say 0.51 or 0.52 max, based on muzzle velocities and trajectories in firing tests.
you really need to take into account sight radius in determing comeups and moa which most programmes use.
firefighter,
i hope you get 0.6 b.c, but doubt that it will be much over 0.550.
i also hope that you do not get stability issues in horrible winds.
personally, 1.460 is max length for 18 twist, and 1.50 is max for 16 twist.
0.050 over length will still work well at shorter ranges.
keep safe,
bruce.

I hope so too Bruce. The driving band on this bullet is very wide by design. This gives me the ability to chuck it up in a lathe and bring the oal down if need be. Building a bullet to theoretically match my velocity and twist rate is all done on the hopeful yet narrow ledge of the basic math formulas out there, only proof there is comes from firing it and seeing for sure. I'll test things out on the silhouette ranges and press out further if the results are positive. High bc designs are very dependent on alloy and speed, I'm just going to cast them hard and drive them hard and hope for the best.

[bruce m]

chris,
your computer simulation could be a double edged sword.
on one hand it eliminates certain meteorolical factors and unknown physical factors due to transonic issues, making a basic understanding of issues easier.
on the other it cannot take into account the above factors, and thus could still present surprises.
such factors can include wind shear, sonic shock waves, and things we have yet to recognize, let alone understand.
firefighter,
that is a cunning plan designing a bullet you can shorten.
it might save you some money in moulds.
you are too right about the "narrow ledge of basic formulas" out there.
even guys like brian litz sidestep the issues we need answers to when asked directly.
there is just not the knowledge of transonic flight, even at top levels, to fully understand associated issues, and subsonic flight is no much better.

we now know from the experience of many that harder alloys retain b.c. better than softer ones due to nose shape retention.
12:1 has proven to have less drop than 16:1, and 16:1 less than 20:1, and so on.
we know so little of wind shear, head and tail winds, side winds raising or lowering point of inpact, and the effects quartering winds have on our bullets.
stability in transonic flight and going through the transonic to subsonic threshold, if there is one, is not understood, and this can affect b.c. also.
my next thing to try is cupped base bullets. this is due to the fact that the cupped base moves the centre of mass of a given length bullet forward towards the centre of pressure, reducing the overturning moment.
this translates into improved stability.
the o.d.g. used slower twists than we now seem to need with our flat based bullets, and quite long bullets.
why were their bullets stable if it were not for that reason.
only problem is you have to swage those bullets to get say a good elliptical nose.
swaging gear for 12:1 alloy will of necessity be mighty, and who can make dies of the required shape and strength these days.
perhaps a hammer swage?
whatever the velocity range, a higher speed, higher b.c. bullet will always be better, but you have to be able to shoot it.
frank hyde was known to try the 2 7/8 case and very heavy bullets, but does not appear to have pursued that line of thought.
even for a tough o.d.g. that might have been too much, particularly in a 10 lb rifle.
keep safe,
bruce.

[desert deuce]

I suspect the answer is similar to many other issues in life. Balance.
The final measure of which probably is the ability of the shooter.
If the measure of success is the results it comes down to what combination of factors does the shooter shoot best.

AND, as Frank Hyde may have discovered, a .6 BC bullet with 100+ grains of powder in a 10 lb rifle was not it.

[art ruggiero]

what is the bc of the old standard paul jones 4501 creedmoor that shoots so well ? art

[rdnck]

As I see it, bc is important, but only up to a point. It is well known that some bullets are more accurate than others in a given rifle. I will take the most accurate bullet out of my rifle that I can reach the target with over one that shoots a couple of minutes flatter but gives a larger group. That is what the elevation knob on the rear sight is for--to add elevation if you need it. Now if you get off on bragging rights that go with having an over the top bc, have at it. Just don't be surprised if someone skins you up using an "inferior" bullet design. Shoot straight, rdnck.

[rdnck]

As I see it, bc is important, but only up to a point. It is well known that some bullets are more accurate than others in a given rifle. I will take the most accurate bullet out of my rifle that I can reach the target with over one that shoots a couple of minutes flatter but gives a larger group. That is what the elevation knob on the rear sight is for--to add elevation if you need it. Now if you get off on bragging rights that go with having an over the top bc, have at it. Just don't be surprised if someone skins you up using an "inferior" bullet design. Shoot straight, rdnck.

[desert deuce]

Heresy Warning Bruce M. Heresy, Heresy...

Silhouette Rifle Max weight is 12 pounds 2 ounces. Target Rifle International 13.0 pounds, American 15.0 pounds, American Tollofson 25.0 pounds. Early ODG American Rifles Europe and American 10.0 pounds.

Ever notice we rarely mention total rifle weight in relation to bullet weight and barrel twist in these BC discussions?

I have seen, witnessed actually, a competitor in a large silhouette match use a .45 caliber bullet over 470 grains weight. It was a scoped rifle and I assumed it was well over 12 pounds 2 ounces in weight simply by appearance. He was shooting next to me as I was spotting for my shooter. The bullet in the loaded case did indeed appear long and large. What was remarkable was how well it shot and the fact that one could visually follow the bullet from muzzle to steel at all four ranges which indicates it was probably subsonic when leaving the rifle and all the way to the rams. Even then, it was clear that it was the ability of the shooter with that particular rifle and load that was responsible for the high score under those challenging conditions.

Wondered if the success was related to no transonic event for that bullet. Tried the idea in my 11.5 pound 45-70 and the groups in calm conditions were good. In twitchy conditions not good and load had to be increased velocity wise with a 535 grain PJ 45001 1-20 bullet 18 twist barrel to impress the turkeys and rams, accuracy wise. The caveat here is: If you don't hit the steel animal chances are very good it will not topple over which results in a miss.

Which all falls back on the results flowing from the combination of shooter ability, rifle and load.

And the true heresy: Is the shooter, rifle, load, combination still as high performing after 55 shots in a day as they were after five or ten shots testing ? If you don't shoot matches, how will you ever know

Shooter fatigue is even more important in long range creedmoor.

[rdnck]

470 or 570? rdnck.

[desert deuce]

thanks for catching that, yes 470 was a typo, the bullet was over 570 grains.

[bruce m]

no heresy there zack, and bill too.
after safety, the 1st rule is accuracy.
the aim of shooting is hitting.
high b.c. is not sought after for flat trajectory, but rather to minimize wind deflection.
as bill says, you can always wind the sight up, but the bullets must group when they get there.
the big difficulty is countering wind deflection, and we can only do that to a certain percentage of perfection.
the smaller the total deflection, for the same percentage we stay closer to the centre, giving an edge in competition.
as range increases, so vert becomes more the main issue.
there will in all probability be more vert with slower bullets.
wind we have some control over, but a high or low shot is a miss we can do nothing about until we fix the problem that caused it.
and yes, recoil does grind you down for fine shooting.
rumour has it that hyde went back to the 2.4" case after using the 2 7/8" case and a 600ish gn bullet. that load would have used well over 100 gns of powder, possibly approaching 120 gns.
not fun even in the back position.
he went back to what was considered standard, as that had evolved because it was the best compromise.
keep safe,
bruce.

[Kurt]

I agree with Bill on the high BC part. I would sooner raise the sight a turn more as long as the bullet hits what I want it to.
I got caught up in the pointy bullet hype myself and have more then a few of them but I could never get them to shoot as well as the more blunt nosed bullets especially in high wind conditions.
I had Walt at NEI cut me a 4 cavity mould for the .45-90 and the .40-70 and one cavity was the .458-535 #349C for the .45-90 that was a problem rifle and that speed bump bullet at almost 1.5" long was the only bullet I have found to shoot well and the PJ 45001 in that 18 twist rifle. Brooks has a long heavy 5 groove like his Creedmoor nosed that is right at 1.5" long that shoots well in the .45-90 18 twist and the .45-70's I have.
Some other rifles I have shoot the flat and round nosed bullets better then the elliptical and some shoot the elliptical better as far as my sights will reach. It all comes down to what works best in the rifle.