Reduced velocity for decreasing wind drift

[flatsguide]

I shoot exclusively PP bullets so posting this question here. It is well known that .22LR subsonic loading has significantly less wind drift that the same bullets flying above the speed of sound and the .22 LR loads that drift the most are the highest velocity loadings. My PP loads in .45-70 is an elliptical 530gn bullet driven by 81.5 gn of 1.5 Swiss giving me a velocity of 1250 FPS. This is in the same ballpark as some of the .22LR higher velocity loads. Should I get less wind drift by reducing velocity to just under subsonic and also get an additional accuracy boost by not going into the transonic instability since I would be below the speed of sound at the muzzle?
Thanks Richard

[Don McDowell]

I think it best to find the best grouping load you can. Then learn to read the wind and mirage. I've witnessed 45 caliber bullets of the same style weight etc, being shot by different shooters out of different guns at the same match, and chances are the 45-70 doing just short of 1200 fps, will come out of the match with just as good and sometimes better score than the shooter using a long case with a scoop shovel full of powder , doing close to 1400 fps.
While it is true that the standard velocity 22 loads hold up better at 200 yards in the wind than the high velocity and super high velocity loads, the tiny speck of a bullet the 22's use, it's not a good comparison to the bullets shot in BPC competitions.
I believe in BPC it's more a matter of matching and keeping the bullet length just slightly under what the twist of the barrel should stabilize, especially as the bullet travels out and goes well below that transonic zone.

[jdfoxinc]

The longer the bullet is 'in the wind' the more effect the wind has.

[Petrol & Powder]

I think you're starting with a false premise.
Your statement, ".....It is well known that .22LR subsonic loading has significantly less wind drift that the same bullets flying above the speed of sound and the .22 LR loads that drift the most are the highest velocity loadings. ...." is not completely true.
.22LR projectiles that start out supersonic and then transition to subsonic speeds before reaching the target, often exhibit larger groups - BUT that's not necessarily a result of wind drift. The transonic loss of stability isn't absolutely tied to the effects of wind on the bullet.

Wind drift is the force of the wind pushing on the projectile in flight. The longer a crosswind has to act on the bullet, the greater the distance it will deflect the bullet's path.

The advantage of starting with a subsonic velocity is that the bullet never transitions from supersonic to subsonic because it was never supersonic to start with. The slower projectile will be in flight to the target longer than a faster projectile travelling the same distance and the wind will have MORE time to act upon the slower projectile. However, if the slower projectile is more stable in flight and the wind is constant (or the shooter is very skilled at adjusting for wind deflection) the projectile may still land where you want it to land.

So, you're not exactly wrong but you may be using the term "wind drift" incorrectly. Wind drift refers to the force of the wind acting upon the bullet in flight.

[flatsguide]

Hi P&P, it is not a false premise but counterintuitively true, subsonic .22LR loads show significantly less wind drift (wind drift as I understand it, is the effect of the crosswind component of the wind acting on the bullet) than their supersonic counterparts and the higher the .22LR velocity the higher the Wind Drift. The only reason I ask the question was to find out if the same held true for heavier and higher BC bullets launched at similar velocities.
The transonic instability is a totally separate issue from wind drift as I see it.
Don, I would gladly give up hamburgers and fries if I could dope the wind better. But was thinking that there may be a good benefit at 200 yd paper punching if one could get a 20% decrease in wind drift without the human wind doping factor.
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Best, Richard

[Petrol & Powder]

While I don't dispute the results with .22 LR you are relying on, I don't think you can extrapolate those same results to heavier projectiles.
The additional variable of the transonic behavior of .22LR projectiles is not present (at least at the ranges we're dealing with) when we move up to heavier bullets.
I think there's more than one factor at play when we are talking about 40 grain .22 caliber projectiles travelling at just under or just over the speed of sound.

[Don McDowell]

Richard, I've tested and seen the difference at 200 yards with the 22 ammunition, including high velocity match. Velocity at or just under 1100 seems to be about right, of course a lot depends on whether the rifle likes the brand of ammo or not. Amazing how picky those rifles can be. The big bpcr's aren't quite as picky altho I have a couple that are just as picky if not more so than 22's.
On the mirage and wind thing it's just a matter of spending a lot of time outside watching and learning, and if you can put a few rounds down range then so much the better.
The Creedmoor cup style matches, are great learning events, where it's just you your rifle and spotting scope shooting for the score at 1000 yards. Frustrating as all get out at times, but fun none the less.

[Win94ae]

I think you're starting with a false premise.
Your statement, ".....It is well known that .22LR subsonic loading has significantly less wind drift that the same bullets flying above the speed of sound and the .22 LR loads that drift the most are the highest velocity loadings. ...." is not completely true.
.22LR projectiles that start out supersonic and then transition to subsonic speeds before reaching the target, often exhibit larger groups - BUT that's not necessarily a result of wind drift. The transonic loss of stability isn't absolutely tied to the effects of wind on the bullet.

Wind drift is the force of the wind pushing on the projectile in flight. The longer a crosswind has to act on the bullet, the greater the distance it will deflect the bullet's path.

The advantage of starting with a subsonic velocity is that the bullet never transitions from supersonic to subsonic because it was never supersonic to start with. The slower projectile will be in flight to the target longer than a faster projectile travelling the same distance and the wind will have MORE time to act upon the slower projectile. However, if the slower projectile is more stable in flight and the wind is constant (or the shooter is very skilled at adjusting for wind deflection) the projectile may still land where you want it to land.

So, you're not exactly wrong but you may be using the term "wind drift" incorrectly. Wind drift refers to the force of the wind acting upon the bullet in flight.

Drag is greater when the bullet is supersonic, and drag is a function of wind drift.

That I why I keep all my handgun bullets at 1050fps or lower. Even if I can get to 1500fps, it drifts more. I've found this out when I went from a 357mag pistol to a 44mag rifle for deer hunting; I could not understand why wind drift was easier with the pistol, until I ran the numbers. I went to the rifle because I knew it would preform better, but it ended up being worse in the wind drift department.

Run the numbers in a ballistic calculator.

[Chill Wills]

Flatsguide, you are correct in that a bullet of any size and weight adheres to the same laws of physics.
This subject requires lots and lots of text to cover I'm not up for that. IN the last 20 years this has been beat around endlessly. Which is not to say it can not be again:bigsmyl2: but I will keep my part short.

Bc is Bc. Bc of .400 is a Bc of .400 - no mater caliber or bullet weight. All bullets of that Bc respond the same. Period, or they are not the same Bc.

Understand, Bc is not static. It is dynamic with velocity. This is often overlooked in these conversations.

Yes, you are correct, bullets with MV < 1100 fps have less drift than the same bullet in the 1100 to about 1500 fps range. BUT, as pointed out, there are trade-offs. As you slow the MV down, we start to see greater elevation spread on the target at distance. There are endless examples of that. In the case of very high quality 22 match ammo, very narrow velocity spreads address that and 200 meter groups can be very good.

Don is right. There are trade-offs in that to get much better high - low impacts on target at long range (BPCR) a little wind reading is called for. Take your pick. lower velocity = less wind drift and greater high/lows. Higher velocity = better high/lows and more wind drift.
Boy, I hope I don't regret stepping into this .....again [smilie=l:.

[dtknowles]

Hi P&P, it is not a false premise but counterintuitively true, subsonic .22LR loads show significantly less wind drift (wind drift as I understand it, is the effect of the crosswind component of the wind acting on the bullet) than their supersonic counterparts and the higher the .22LR velocity the higher the Wind Drift. The only reason I ask the question was to find out if the same held true for heavier and higher BC bullets launched at similar velocities.
The transonic instability is a totally separate issue from wind drift as I see it.
Don, I would gladly give up hamburgers and fries if I could dope the wind better. But was thinking that there may be a good benefit at 200 yd paper punching if one could get a 20% decrease in wind drift without the human wind doping factor.
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Best, Richard

I see in your charts that the slower bullet has a higher BC. Are they the same bullet but the BC of the bullet is higher as sub sonic than at super sonic.

[Win94ae]

I see in your charts that the slower bullet has a higher BC. Are they the same bullet but the BC of the bullet is higher as sub sonic than at super sonic.

That was a bad example to display the effect. You can always play around with the numbers yourself.

https://www.hornady.com/ballistics-resource/ballistics-calculator

[flatsguide]

Chill, I was not aware of vertical displace of hits at low velocities. I’m aware of the need for low velocity variations, ES, to prevent vertical stringing. The way I’m reading your reply that vertical stringing is more of a problem at low subsonic velocities.
Found this on Sierras site.
“The ballistic coefficient values in the three figures exhibit strikingly similar behavior with abrupt changes near the speed of sound. Perhaps the data in Figure 4.5-3 for the .44 caliber 240 gr JHC best illustrate this characteristic. If the bullet starts at a velocity near 1300 fps, the ballistic coefficient is nearly constant until the bullet slows to about 1160 fps. At this velocity the ballistic coefficient rises abruptly as the bullet slows to about 1140 fps. Then the ballistic coefficient falls precipitously to a minimum value which occurs near 1100 fps. The ballistic coefficient then rises dramatically to a second peak value which occurs near 1050 fps. As the bullet slows below 1050 fps, the ballistic coefficient decreases in value, but in a less dramatic manner.”

Anyway BC is always velocity dependent and changes with changes of air temp, pressure and humidity.
Richard

[dtknowles]

That was a bad example to display the effect. You can always play around with the numbers yourself.

https://www.hornady.com/ballistics-resource/ballistics-calculator

I wonder about the calculator. How does it handle BC. Does it account for changes in BC as the velocity changes. It asks for a BC as an input field. What do I put there, the BC at muzzle velocity. Where to get good BC data, I doubt the results because of garbage in garbage out.

Tim

[flatsguide]

Tim, I had the same thoughts as well.

[Don McDowell]

The online calculators will get you close and give you a fair idea of what to expect. But there isn't a one of them that will tell you what to expect when your line flag is going left to right, the flags about half way down the range are pointing at each other and the flags at the target are pointing straight up. The mirage showing consistent right left..
The Wind Chart that Shiloh sells is about as good as you can get.
Sometime just sit and watch a flag, such as a US or State flag on a flag pole, and take particular notice of how the flag flops compared to what you feel on the ground where your sitting, and take particular note of how the ripples in that flag are not consistent.
Tons of things shooting related can be learned by simple observation in non shooting related places.

[Lead pot]

The best ballistic calculator is you with your rifle, a good spotting scope and a target down range 600 yards or more.
I have spend hours sitting in my back yard with a target at the far fence line 730 yards over the bean field watching the condition changes and looking at a wind anemometer and watching the mirages firing a shot.
Set a no wind zero early in the calm morning air and wait for the ground warm up and watch the mirages starting to roll and fire a couple shots when the condition is the same drive down and mark the hits and recording them. Shoot again when the conditions change and repeat the recordings. Do this without making a sight change.

:D now I have a drone that takes very good photo's and I can send it down range and it will do the running and recording :D

Doing this is better than a calculator, this is on the job training what conditions will do to the bullet drift and how far it drifts with the change you watched.

As for the high or low velocity drift with the .22, put up a target watch the conditions and shoot.

[dtknowles]

The online calculators will get you close and give you a fair idea of what to expect. But there isn't a one of them that will tell you what to expect when your line flag is going left to right, the flags about half way down the range are pointing at each other and the flags at the target are pointing straight up. The mirage showing consistent right left..
The Wind Chart that Shiloh sells is about as good as you can get.
Sometime just sit and watch a flag, such as a US or State flag on a flag pole, and take particular notice of how the flag flops compared to what you feel on the ground where your sitting, and take particular note of how the ripples in that flag are not consistent.
Tons of things shooting related can be learned by simple observation in non shooting related places.

The point was to understand if subsonic loads have less wind drift than supersonic loads at moderate velocities. I think it is clear that the time of flight advantage that a 3000 fps load has over subsonic loads over comes any advantage the subsonic load has in ballistic coefficient. It is clear that subsonic loads have a wind drift advantage over transsonic and low supersonic loads but do they still have an advantage vs.1800 fps load or a 2500 fps load but I guess the 2500 fps load is not something you can get with Black Powder.

[Chill Wills]

Chill, I was not aware of vertical displace of hits at low velocities. I’m aware of the need for low velocity variations, ES, to prevent vertical stringing. The way I’m reading your reply that vertical stringing is more of a problem at low subsonic velocities.
Found this on Sierras site.
Richard

Good morning Richard,
Correct. As an example, a 20 FPS ES as started from accurate BPCR ammo, producing 1050 FPS (MV) will show much greater vertical on the long targets as compared to equally accurate ammo producing a 20 FPS ES starting at 1300 FPS.
Additionally, when you add in head and tail wind components, they will adversely effect the slower ammo as well, showing up as much lower or much higher hits when compared to higher velocity ammo.

Again, it comes down to trade-offs. If you were to graph the different effects and overlay them, it turns out the "X" in the data for black powder driven ammo (BPCR) puts the sweet spot in the 1250 to 1350 FPS range for shooting targets at the 600y to 1000y distances. It is also "not bad" for closer targets too, but backing off a little velocity for the 200m to 385m targets does not hurt a bit either. This is somewhat subjective group think, but reflects the mainstream of national level match competitive ammo used.

There are two books on the subject of external ballistics that will make your brain itch. from memory Robert Rinker and the other is Pijsa maybe? I can check the book case if you are interested. It is both fun and dry reading. ...An immense amount of info to wrap one's head around but has useful info.
-Michael Rix

[Don McDowell]

Trying to correlate what happens with modern high-power bullets and BPCR stuff will cause no end to the grief.
I'm setting here watching the annonometer on the cheap plastic weather machine, and see enough of a speed change to need a 4-6 minute change on the windage knob with at least a 1-2 minute change just during the time of flight of the bullet.
Static calculations on a computer are great, but they are no substitute for the real world thing.

[Win94ae]

The point was to understand if subsonic loads have less wind drift than supersonic loads at moderate velocities. I think it is clear that the time of flight advantage that a 3000 fps load has over subsonic loads over comes any advantage the subsonic load has in ballistic coefficient. It is clear that subsonic loads have a wind drift advantage over transsonic and low supersonic loads but do they still have an advantage vs.1800 fps load or a 2500 fps load but I guess the 2500 fps load is not something you can get with Black Powder.

It works exactly as I have found in real world situations.

If you play with the calculator, you find it works just as you think it would.

As soon as a bullet bow shock-wave is formed, the drag is elevated, and you get a increase in wind drift. When the speed gets to about 1600fps, the drift starts to reduce, at about 2000fps, the drift is the same as it was at 1000fps, and continues to reduce as the speed increases.

This isn't really that complicated. There is increased friction at the speed of sound, which increases drag. Once the speed gets to a point that the time of flight is great enough to overcome the friction, you get less wind drift.

[Shanghai Jack]

Here's a quote from Hornady. "Ballistic Coefficient (BC) values can, and usually do change in value with changes in velocity. Most bullets exhibit a lowering BC as velocity slows. The extent of how much a BC will change depends on each unique bullet shape. When comparing BCs of different bullets, it is important to use an apples-to-apples approach."

[martinibelgian]

I do believe it might be useful to have subsonic loads - but only for the shorter ranges, say out to 300-400. Any further out, the vertical will show up much more and negate any wind drift benefit. At least, that's what I believe - and that's also the reason I built a heavy-bullet fast-twist 32-20. I should really chrono it, but it seems to work well out to 300m. It seems to like a 152gr bullet, but a 173gr Pope-style shoots well too. I'm now waiting on a David Mos mould which should be tailored to the rifle/chamber combination. But 1st I would like to be able to shoot, haven't been able to fire a single round in 6+ months...

[flatsguide]

Talk about timing, I just started reading my copy of the “Modern Schuetzen Rifle” by Schwartz Dell. In it they mention numerous time the benefits of subsonic loads to reduce wind drift. Of course they are shooting at 200 yds.
Chill, I would certainly be interested in those books you mention!
Leadpot, sounds like you have the best of both the old world and new world with the luxury of a long range at home. Please don’t tell me you just open your window at home and your bench rest is in the den.
Don, I’m going to start to be a bit more aware of the wind...especially the subtleties.
Thanks again guys all good info,
Cheers Richard

[Don McDowell]

Richard on the range sometimes its the flags that are lying, and it's the mirage that needs to be heeded.
There are a couple of ranges I've shot Creedmoor on, that the mirage actually has 2 or sometimes 3 layers, and if you don't look past an thru the first , things won't go particularly well.
Lots of voodoo, involved in getting the bullet on target sometimes.
Couple of notable quotes I've over heard from top spotters, "well looks like with these conditions every shot is going to be starting a new match" and " let me roll these chicken bones again before you get in the gun"

[flatsguide]

Don, I’m sure that takes a lot of experience to see through two or three layers of mirage,in fact, I’ve never New there was a phenomenon like that but it does not surprise me. It’s like seeing wave patterns at sea you can see two but seeing 3 or more just takes time and observation; or like seeing Bonefish, not known as the Grey Ghost for nothing, out of the water they are silver in the water they reflect the bottom and almost disappear from sight, sometimes only their shadow gives them away....takes a long time to learn to see them too. Thanks Don for the help
Richard

[Lead pot]

No Richard I cant use the field anymore. My Neighbor passed and his Daughter is anti everything. She even called the sheriff on his best friend for walking his dog on the waterways in the field.
But yes, I can shoot out of my kitchen window or from the front porch where I have a bench into a large berm I pushed up at the fence line :D

People are changing, not just here but all over this great Country.

[Don McDowell]

Richard I think a lot of the attraction to this game beyond the nostalgia of shooting 100 plus year old technology, is the challenge that simple basic things mother nature can throw at you.

[flatsguide]

Leadpot, sorry to hear that, no accounting for some people, sad really.
Don, when you think about it I’m as guilty as others when it comes to ignoring things governed by nature, human body included. Some of nature whims you can’t control but just need to learn to minimize their effect as in reading the wind or mirage, same thing for offhand practice. I spent most of my time in pistol and rifle shooting trying to get the best groups and minimize the “human factor” , spending that time and money too on toys and tools and much less time on reading wind or offhand practice. I think one can see that in the gun magazines, at least most of them on the bookstore shelf, touting the latest gun or gadget and very little of wind “doping”, physical conditioning or offhand shooting, no bucks to be made in that area I suppose. Like I mentioned I’m as guilty as charged in this area.
Off on a tangent, but I wonder what would be the result in this country if gun safety and shooting was taught in grade schools with air rifles and smallbore was taught in high schools. What am I smoking lol. Fat chance that ever happening.
Richard

[Don McDowell]

Richard there was a time not so terribly long ago when high schools had rifle teams, and shotgun teams. Some isolated places still do.
Take a look at the sheer number of youngsters participating in the 4H shooting sports.. and the number of young hunters.
There is still some hope :)

[Don McDowell]

One more thing if you take or buy on occasion the BPC News, the next issue is supposed to have a full write up about the Desert International match held this past March at the Ben Avery Range. The load details ( altho the only patched shooter was Ray Hanson with his muzzle loader) will reveal some stuff that is likely to make some collective heads expode. :)

[Shanghai Jack]

Richard there was a time not so terribly long ago when high schools had rifle teams, and shotgun teams. Some isolated places still do.
Take a look at the sheer number of youngsters participating in the 4H shooting sports.. and the number of young hunters.
There is still some hope :)

I sincerely hope that the times change but I'm not holding my breath.

You should have seen the consternation on the face of my principal when I and a few parents approached him with the concept of a fully funded air-rifle club at the middle school. I thought he was going to have a coronary. After that it was all obstacles, one after another after another.

I'm old enough to remember the days when we could go to school, put the .22 with ammo in the coat room, and go hunting when the school day was over.

[flatsguide]

I guess that news will be in the Summer issue of BPCNews.
I remember the same and at 15 bought .22 ammo and shotgun shells at the local hardware store. 82 years young, in my mind...my body has it own thoughts though.
Best Richard

[flatsguide]

Well I’m getting serious about trying subsonic loads! The club I’m going to join hold a BPCR 200yd, 10 shot, Benchrest shoot twice a month. As a refresher, my current load in my 45-70 is 81.5gns Swiss F1.5, 530gn PP elliptical MV 1250fps. I want to use the same bullet seated almost completely into the rifling as I do now and get the velocity to 1050 to 1100 FPS. For no good reason I’d rather not use case fillers (although it may come to that). My thoughts run to filler wads something like a half inch thick veggie wad or two quarter inch thick veggie wads. An extreme thought is machining a brass filler to press into the case to reduce case volume. It would have a hole in it naturally for the primer flame and covered with a newspaper wad to prevent powder from getting into the extended flash hole. Would only need to make around 15 so that’s not too bad. Seating the PP bullet deep into the case may be one option though. Any thoughts, ideas, suggestions ? Any idea on where to find thick veggie wads?
Thanks guys,
Richard

[Don McDowell]

1f powder, or as you say seating the bullet deeper.
To much wad stack can cause you grief.
If the leading edge of the patch engages the rifling an 1/8 inch or so it'll likely shoot well.
Have never quite grasped on to the need to load a 45-90 load in a 45-70 case.

[rfd]

Back in the late 50's to very early 60s I rode a bus and train to high school rifle team practice with my cased rifle. No one even blinked an eye. The good ol' dayze that'll never return.

Loading a PPB .1" into a .45-70 case full of 1-1/2F sorta makes it into a kinda virtual .45-90 whether one likes it or not. :)

[Chill Wills]

Here are the two books referenced. Some fun reading along with some hard math and science. Even covers info on the big Naval Guns.

[fiberoptik]

Go with a heavy for caliber boolit subsonic. Maybe 750.gr.


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[M-Tecs]

It would be interesting to see actual Doppler radar printouts verse the ballistic programs based on models.

[flatsguide]

Fiberoptik did you mean 570 grains. I was looking to see if BACO had any but no.
Chill, thanks for the book titles, appreciate it .
Don, I can understand what you are saying and compared to most of you here I’m a novice when it comes to BPCR shooting, and most of my BPCR load development come from this PP site in general. Your comment about not understanding why 45-90 loads are put in a 45-70 case was never, to my knowledge, ever addressed here before. It was always about getting the bullet shoved so far up the spout that to get it any further up would require a breech seater. It would be nice if the was a factory 45-60 case. I will try seating the PP bullet deep in the case with about a 1/8 of paper into the rifling, my loads now are shooting under 1 moa but wind is my nemesis that I need to come to grips with too.
Thanks guys, Richard

[rfd]

... I will try seating the PP bullet deep in the case with about a 1/8 of paper into the rifling, my loads now are shooting under 1 moa but wind is my nemesis that I need to come to grips with too.
Thanks guys, Richard

Under 1moa at what distance and with what shooting position?

[flatsguide]

RFD, 100 yds with 200 yds occasionally. Occasionally means I don’t test at 200 but when I do it also is under 1 MOA. The MOA groups are at a bench with a forward bench rest and rabbit ear sand bag at the rear. I have not tested my groups from prone X sticks but manage to clean most of the sillhoette targets( we won’t talk about the chickens though). The load is Starline brass annealed stretched and trimmed to .005” shorter than chamber length, 81.5 guns Swiss 1 1/2 compressed.030” wad is .063 LDPE and one freezer paper wad under bullet, bullet is 530gn elliptical .444 dia. Patched to .4495. Seated .125”. CCI BR2 primers. Rifle is Miroko knock off of an 1885 Winchester, it is theBPCR model. MVA 8x scope. Shaver-trigger job at a heavy to me 4 lb.
Richard I can’t upload any of my other target photos for some reason

[flatsguide]

For some reason I cannot load any photos. If someone watching can post them for me that would be great. I can send them to you via email then you could post them.
Just PM your email to me. Thanks a Richard.

[Chill Wills]

For some reason I cannot load any photos. If someone watching can post them for me that would be great. I can send them to you via email then you could post them.
Just PM your email to me. Thanks a Richard.

I see one picture in post 41. were there any more? If not, you are doing it right.
Nice wallet group. I've never shot a group that small ...but, I test 5 to 10 shots at a time.

[Chill Wills]

I just reread your group details and match performance. I would say you have it going for you. You are there. Cleaning all the lay-downs is saying something.

[flatsguide]

Hopefully the pics show up...
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[flatsguide]

Reading SPG’s “BP Cartridge Reloading Primer” p.112, states that with a 10 mph crosswind, a somewhat elliptical.45/500gn bullet with a MV of 1100 FPS has a 6.33” wind drift at 200yds whereas the same bullet starting out at 1200 FPS has a wind drift at 200yds of 7.34”. Is it worth the effort, probably. If the bullet does not have to go through that transition one may gain even more accuracy in no wind conditions.

[Chill Wills]

I think you are in a sweet spot now with velocity in the mid 1200's .
However, ...I'll be reading your report to see what you come up with.
On a different note.... Too bad it is so far from one BPCR silhouette match location to another. It would be fun to shoot shoulder to shoulder with everyone I would like to. See how it goes for them.

[fiberoptik]

Nope. 750.


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[flatsguide]

Chill, that would be nice. Unfortunately my short flirtation with Silhouette shooting is about over, I’m almost 83 and my bad back makes it agonizingly painful getting down and up from the prone position and sitting looses to much long range hits. A local club that I’m going to join has BPCR 200yd shoots off a bench twice a month so I’m looking forward to continuing to shoot there.
Fiberoptik, I would probably get below subsonic with that heavy a bullet but I doubt that the rate of twist, 1:18, in my barrel especially at that low a velocity would stabilize that long of a bullet. Good thought though.
Cheers Richard

[Chill Wills]

Nope. 750.


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45-70-750 black powder Blackout :razz: fun stuff to muse about

[flatsguide]

When Fiberoptik mentioned the 750 gn bullet I did a google search for it and found nothing so I thought he mistyped and meant a 570gn bullet. Can one of you guys steer me to the “blackout” loads for .45-70.
Thanks Richard

[Don McDowell]

Chill didn't you guys over there on the west slope get Bernie to build you some 700's grain mold blocks?

[fiberoptik]

I read an article in a gun magazine where the guy had a .45-70/.45-90/.45-120. He was talking about using the biggest, longest, heaviest bullet he had, which was made for the.45-120. He said if he couldn’t go over the sound barrier, he was going to make sure he launched the heaviest bullet he could, to carry velocity as best with the highest B.C. to carry it through. I’m certain he said it was a 750 grain cast boolit. Wish I could remember where I read it.
That boolit looked like a cigar! Maybe paper patched?
Looking at moulds, maybe [emoji848] I do have it wrong.......

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[flatsguide]

Lol, I bet it looked like a cigar. I have searched high and low for that bullet. I guess it was a custom mold.
Cheers Richard

[Idaho Sharpshooter]

750gr...? Maybe Accurate Moulds or NOE?

Rich

[MichaelR]

I hate to rain on somebody’s parade, but a .45 bullet going 1100 FPS is not going to be subsonic. It’s not the speed over the ground that counts, it’s the speed of the air over the bullet. The air has to travel a lot farther around a .45 bullet than a .22 bullet.

[flatsguide]

And that’s why it’s called the transonic range.

[Chill Wills]

I hate to rain on somebody’s parade, but a .45 bullet going 1100 FPS is not going to be subsonic. It’s not the speed over the ground that counts, it’s the speed of the air over the bullet. The air has to travel a lot farther around a .45 bullet than a .22 bullet.

100% correct. The displaced air accelerates as it is compressed going around the bullet. Then add the additional drag as turbulence filling the cavitation behind the bullet. Much drag in the transonic zone. Marginally stable bullets can get lost en route to the target.

However, starting it slower = less time in the critical center of the zone. That may or may not be beneficial to the end goal. Details mater.

"The air has to travel a lot farther around a .45 bullet than a .22 bullet."
I think that would depend competently on there individual sectional density. Hmmmmm....

[flatsguide]

I’m not sure Michael is correct. A bullet at a standard day at SL is just below the speed of sound at 1100fps. by definition it is air speed and if there is a no wind condition it is ground speed too and is not related to the Mach shock waves on the bullet, which are supersonic. To Michaels second point, unless I am mistaken, it is more a function of the thickness to length ratio or fineness ratio if you will. Say a .45 caliber bullet with a length of 1.750 inches and a PP diameter of .444”, .444/1.750 =.253 or thickness ratio of 25%. For a .22 LR bullet with a bullet length of .480 and a diameter of .222, .222/.480 =.46 or 46% . This shows that a .22LR bullet has almost twice the thickness ratio of a 45 cal BPCR bullet. What I take away from this is the air has to accelerate quicker over the .22LR bullet, but not necessarily further, to create the Mach shock wave on the bullet. It is the thickness ratio that determines the airspeed/FPS that the onset of the shock wave start on the bullet. I believe that is called the Critical Mach number. One only needs to look at airfoils thick curved ones to operate well in the subsonic ( we don’t want any shock waves on these airfoils) and supersonic airfoils that have very fine thickness ratios and non or almost no curvature. Interestingly, I don’t know of any aircraft that are designed to operate in the transonic zone. They are either operating about 15% below the speed of sound or well above it.
Bullets that are decelerating and are just above the speed of sound experience a rapid rise then rapid drop in pressure I think this may rapidly change the center of pressure location on the bullet and that is the cause of the transonic stability problems.
I’m not a ballistics expert, just an old not too bold pilot with just enough knowledge of aerodynamics to get in trouble. Would it not be fun to shrink down, strap a saddle on a bullet and ride it out a thousand yards or so...

[Mr_Sheesh]

Only if you like the dizzy part of being spun up to many, many RPMs, oh and the G forces from firing LOL

[flatsguide]

Yaa think ? Lol
Richard

[dtknowles]

I’m not sure Michael is correct. A bullet at a standard day at SL is just below the speed of sound at 1100fps. by definition it is air speed and if there is a no wind condition it is ground speed too and is not related to the Mach shock waves on the bullet, which are supersonic. To Michaels second point, unless I am mistaken, it is more a function of the thickness to length ratio or fineness ratio if you will. Say a .45 caliber bullet with a length of 1.750 inches and a PP diameter of .444”, .444/1.750 =.253 or thickness ratio of 25%. For a .22 LR bullet with a bullet length of .480 and a diameter of .222, .222/.480 =.46 or 46% . This shows that a .22LR bullet has almost twice the thickness ratio of a 45 cal BPCR bullet. What I take away from this is the air has to accelerate quicker over the .22LR bullet, but not necessarily further, to create the Mach shock wave on the bullet. It is the thickness ratio that determines the airspeed/FPS that the onset of the shock wave start on the bullet. I believe that is called the Critical Mach number. One only needs to look at airfoils thick curved ones to operate well in the subsonic ( we don’t want any shock waves on these airfoils) and supersonic airfoils that have very fine thickness ratios and non or almost no curvature. Interestingly, I don’t know of any aircraft that are designed to operate in the transonic zone. They are either operating about 15% below the speed of sound or well above it.
Bullets that are decelerating and are just above the speed of sound experience a rapid rise then rapid drop in pressure I think this may rapidly change the center of pressure location on the bullet and that is the cause of the transonic stability problems.
I’m not a ballistics expert, just an old not too bold pilot with just enough knowledge of aerodynamics to get in trouble. Would it not be fun to shrink down, strap a saddle on a bullet and ride it out a thousand yards or so...

I know of a number of aircraft that are designed to operate in the transonic region. Cessna Citation X+ Mach .935 (536 kn; 993 km/h) Cruise speed 528 kn (978 km/h) Minimum control speed 114 kn (211 km/h) Range 3,460 nmi (6,410 km) Ceiling 51,000 ft (15,545 m) Time to altitude 24 min to Flight level 470
First flight: 21 December 1993
Manufacturer: Cessna
Number built: 339: 310 X + 29 X+
Produced: 1996–2018
Height: 19.2 ft (5.85 m)
Cessna Citation X - Wikipedia

Korean war era jet fighters often operated in the transonic region.

The F-15 had so much thrust it could climb to sixty-five thousand feet in just 122 seconds. In horizontal flight, the F-15 could reach speeds of Mach 2.5, and cruise at speeds of Mach 0.9.

Tim

[Claudius]

Almost all the civilian aircrafts operate in the subsonic region, some others can operate in the supersonic region. A supersonic aircraft cannot avoid the transonic region when accelerates to supersonic speeds, but the subsonic jet aircrafts stay below the transonic because the shock waves start to begin. The transonic region is not so comfortable for both the pilots and the aircrafts, because the shock waves are intermittent and not uniform, so the aircraft structure is overstressed.

The jet fighters of Korean war like a F-86 were subsonic aircrafts, but easily could go through the transonic region when diving, for this reason some of them had spoilers to slow down and stay in the subsonic region: it was a safety measure, also.

You can read the memories of the WWII and the Cold War pilots, they had terrible experiences with the transonic regime. Yes, the WWII pilots knew the problem of the transonic regime and it was extremely dangerous when diving. The subsonic jet fighters could go through the transonic regime but just for a very short time because the stress on the pilot first, and the aircraft structure second.

Regarding a subsonic black powder bullet my opinion is that we have to see other more important aspects: a bullet is not an aircraft. Usually a 530gn bullet shot at 1250 fps starts in a transonic regime and stay there for 100 or 200yds, so why a bullet doesn't seem to suffer of the tragic transonic intermittent shock waves? They do, but in a different way compared to an aircraft because their difference of weight and section. At sea level the air density is the same for a bullet and an aircraft, but the first one is small, compact and heavy and its body is rotating, a subsonic aircraft is a complex and fragile structure. And an aircraft flies straight, it is not rotating. A bullet has no wings and no stabilizers or a rudder, just a rotating "fuselage", for this reason we have to focus on good barrels, good black powders, good alloys, good bullet geometries.

I don't know if real subsonic bullets are better for accuracy, I have my doubts on this because they were designed just to make less noise, and not for the transonic problems.

Longer the distance, longer the barrels, longer the bullets, heavier the black powder loads: I think that subsonic speeds can be obtained just shooting with black powder revolvers and pistols.
The round bullets can go well over the transonic regime, but their symmetrical design is not efficient aerodynamically, and not for transonic reasons.

[flatsguide]

Wow! General Aviation has sure upped their game with high performance aircraft. A bullet in an ideal world would spin about its axis and any shock wave pressure would be evenly distributed, but when a bullet is processing the shock waves would be in different places and I think that’s what causes the instability.

[MichaelR]

Richard you are correct. With the same ogive different caliber bullets would have the same trans sonic properties. But trying to get to 1000 yards or even 500 with the least wind drift has been a goal of most BPCR shooters. But in practice faster seems to beat out slower in practical application.

[Mr_Sheesh]

In WW2 the P38 aircraft, at first, had BAD problems in dives etc. with compressability stalls, been a while since I was up to date on that but I remember they had PROBLEMS. Boolits have it easy, they're much more solid and stronger by comparison, than an aircraft. Always more to learn tho :)

[Claudius]

In the attached photo you can see a modern rifle bullet slowing down to transonic speeds, you can see how the shock waves behave, moving the centre of pressure to the rear of the bullet. This has a really negative effect in accuracy because the centre of pressure is applied on the tail! In an aircraft the problem is caused by the shock waves forming differently on different surfaces (wings, tail, rudder, etc.).

In our BPCR the bullets start at transonic regime but after 100 or 200 meters they will transit to the auspicated and beloved subsonic speeds. I think that for this reason we can get very good results at the long distances. Also our bullets are heavy and after a flight of 1000 yds they have still a lot of energy.

282160

[Chill Wills]

As you can see in this G1 based chart below, the typical BPCR Creedmoor ammo is does not drop out of the transonic range until most of its flight is complete to 1000 yards. Again, because there are so many contrasting qualities to useful BP match ammo or accurate ammo if you like the term better, you end up balancing one improvement against creating a liability. In other words, tradeoffs.


Drag Function: G1 Ballistic Coefficient: 0.45, Bullet Weight: 540 gr Initial Velocity: 1300 fps

Zero Range: 1000 yd Chart Range: 1000 yd Maximum Range: 4671 yd
Step Size: 50 yd
International Standard Atmosphere Altitude: Sea Level (0 ft)
Barometric Pressure: 29.92 Hg Temperature: 59° F Relative Humidity: 50%
Speed of Sound: 1116 fps

Range Vel[x+y]
(yd) (ft/s)
0 1300
50 1246
100 1197
150 1153
200 1114
250 1080
300 1049
350 1022
400 998
450 976
500 956
550 937
600 919
650 903
700 887
750 872
800 858
850 844
900 831
950 818
1000 806

[Chill Wills]

The dynamic nature of a bullet's Bc is shown looking at the 250 of 300yd mark on the chart. See how the Bc really climbs. This points out one aspect of the better subsonic 22rf match ammo competing to 200 meters.

[Claudius]

@Chill Wills, regarding the transonic region, we know that the critical speed for bullets and aircrafts is CLOSE to the speed of sound. So following your measurements we see that the most critical value is at 1300 fps, at 200 yds the speed is still critical, after the flight is without any stress. So, why the books say that the transonic region is starting from M 0.8 to M 1.2? because the altitude: the air density decreases with altitude, and the speed of sound follows the same physics.

Your data were taken at sea level at standard values, so we can easily understand that the real subsonic flight starts just after 200/230yds.

Anyway, your value of 1300 fps is one of the most critical for a 540gn black powder bullet because normally I see 1100/1250 fps. Higher muzzle speed is not necessarily bad, I had 405gn bullets from a Lee mold that flew just a bit over 1400 fps with very good results at 200 meters, but it was a failure when I wanted to repeat the experiment.

[Kenny Wasserburger]

Reducing the vertical is the key. Going slower in my experience isn’t the answer, anyone that has experience at 800-900-1000 yards, knows it’s not.

Edwin Perry’s book tells of working up your load, to reduce the vertical then adding 1 or 2 more grains of powder. Modern Observations on Rifle Shooting, the 1880 edition.

My load at 1 mile has a vertical of 18 inches from top to bottom bullet strike. It starts out around 1418 FPS. It is with a 537 gr PP bullet.

The key is to load to reduce the vertical, then the deep dark secret is to learn how to read the conditions and know what your bullet requires to correct for it.

Fouling control and being mindful of that, goes without saying.

Kenny Wasserburger

[martinibelgian]

I agree with Kenny - for long range shooting, going slower will create more issues than it solves. For short-range work, it might have some merits though... Still to be proven.

[flatsguide]

I agree with Kenny too. As the OP, I was tossing this idea out for two hundred yard shooting only. I’m out of ideas on how to load PP with reduced loads and still keep the the seating depth of the bullet into the case of .120”. I’m a bit leary of fillers especially at this reduced of a load. I do have a GG 530gn mini groove that I may be able to get down far enough in the case with a single .063” LDPE wad only; hoping that the bullet lube alone will prevent leading as I’ll be cleaning ( BACO bore pigs with dry patch one shot cleaning that works fine with PP loads.) between shots. Any recommended lube? I do have some SPG on hand. As a reminder I’m shooting a .45-70 and want to get the load shooting around 1050-1100 FPS. No insult intended about GG bullet on this venue...lol.
Thanks guys

[rfd]

In the past I've used a wad stack with 60+ grains of 1-1/2f, and 400 grain slicks for 200yd matches with some winning results using a rolling block. My current load is 80.5 grains of 1-1/2f under a .060 LDPE wad, under a 529 grain Jim444530E slick and that's kinda overkill for my local 200yd matches. I just loaded 65 grains of 1-1/2f under the same wad and deep seated slick in an effort to start looking for a reduced short distance PPB load - still an excess of lead. Haven't had the weather to test it out yet, but do have an Accurate 405 grain slick on order and will revisit a redesign of the wad stack, and maybe try grease cookies, too. The fun never ends.

80.5 vs 65.5 ...
https://i.imgur.com/95sSUlR.jpg

Wad stack ...
https://i.imgur.com/MdOmBjS.jpg

[Don McDowell]

Richard, 1 f powder combined with a .030 fiber wad, and a 1/8 in felt wad will likely get you down in the velocity you're looking for.
Seating a patched bullet deeper into the case is not the detriment some on the internet would have you believe.

[Gunlaker]

Kenny has it right. The name of the game is controlling vertical and then understanding how to read wind and mirage. There is a reason that in nasty conditions the bigger cartridges usually come out on top in long range.

With respect to the transonic zone, because of pressure differences around the bullet, different parts of the bullet will see the shock wave at different velocities, so the nose of a bullet may have no shock wave, but each grease groove might for instance. I think this is at least part of the reason why ballisticians say the entire velocity range is trouble.

Chris.

[Don McDowell]

The velocity thing is something I don't think will ever be settled. I know I feel better shooting bullets just short of what the twist will allow at 1300 fps or better. But having said that I've seen national records and championship's won in midrange with 535 gr bullets trotting along at 1200 or a bit less.
Recent case in point would be Steve Ferringers run at Byers Money match,Phoenix and 3rd place finish at Lodi. His 45-70 load is reported to run at 1175...
The just to muck things up a bit more, Chip Mate's win in the 1000 yard match at Phoenix and his placing in the top 3 overall, with a 450 grain bullet.
So there are examples out there that defy the " accepted" knowledge.

[Good Cheer]

You guys are making me want a spire point mold for the .52 cal with 38" barrel.

[Keith Andersen]

My .45-70 might reach 1200 fps but mostly it runs 1180 and it will do just as good at the 1000 yard as the .45-100, 110, or the super horsepower .45-3-1/4. It's not the speed it's the shooter that gets the job done.
As far as the vertical, Yes, head, tail, full factor, halve factor will cause verticals but mostly it's a bad load development that puts it in the grass or over the top.

Shoot straight

Keith

No Good Cheers, you don't want to go there.

[Good Cheer]

Keith, it maybe might be some fun to experiment with but ponying up for a custom mold... nuh-unh.
But why in your experience do you think no?

[Keith Andersen]

I used a 500 gr ring tailed for hunting in my slant breech here in the north woods and it got the job done if I didn't stretch it.