above or below the speed of sound

[canuck4570]

I have a 4570 and I am developping a hunting load ..... and my maximun hunting range is 200 yards....should I develope it in a way that at the maximun range of 200 yards the speed of the bullet would be obove the speed of sound...or my question put in another way .... does the transition from supersonic to subsonic affect the accuray and to wich point... any of you have experience in this .... thank you....

[felix]

The only rule to apply here is that the longer the boolit, the more effect the transition will have. Now, for the opposite side of the coin. The shorter the boolit is, the move effect the ambient conditions will have. Take your pick. So, put your targets up at 50 yards, 100 yards, 135 yards, 200 yards to see if your accuracy demands are met. ... felix

[canuck4570]

thank felix.... I like my 575 gr. bullet but the recoil even at 1100 fps is not confortable to shoot... but my 350 gr is a dream and when shot at 1600 fps still is 1150 at 200 yards ( chrono ) and I have notice less accuracy when I shoot it at 1500 fps wich mean at 200 yards it will be less than the speed of sound... 1075 fps...for you who reads this put a steel plate in front of chrono... I have ruined my first chrony that way without puting this steel plate.....this is when shooting at 200 yards...

[Ricochet]

SOS is something like 1140 FPS under standard conditions, I think. I'll look it up when the coffee kicks in.

[felix]

Canuck, save that 500 grainer plus for the 800-1000 yard matches. Would be best to have a 18 twister for this application, to be able to shoot through some unseen strong gales way out there. Use your standard 22 twisters for the 300-400 grainers, and shoot for effect during your typical hunting weather. Pie plate accuracy at 900 fps at target should suffice for deer sized game. ... felix

[canuck4570]

you are right Felix made some study and my 22 inches twist is a bit slow for this bullet never tought of this before..... just cast some 350 gr from my Saeco mold and will be pushing them at around 1600 fps for the same energy of my 575 gr...at 1100 fps .. but will be less difficult to hit at 200 yards...and less hard for the sholder..have a burris balistic plex on my ruger no 1 and a range finder because here in my part of the woods during the day I hunt in the bush and at sundown in the farmer field where there are long shot to be made... but I limit myself at 200 balistic plex realy help to make good hit at far distances.....and at 1600 fps I would be running at about 1150 at 200 so it will be over speed of sound....

[pdawg_shooter]

I load a .451, 430gr paper patch over 52.0gr AA 2495 with a CCI 200. Velocity? Who knows. Accurcy? 3.5 @ 300, Lyman peep on a 1895g. Alloy is 17lb lead, 2.5lb LT, 1/2 lb tin. Four deer with 4 shots. Im happy !!!

[Ricochet]

OK, at 70°F, the speed of sound in air is 344 M/S, which converts to 1128.6 FPS.

[Blackwater]

Just a side note here, but there's a really excellent article in Precision Shooting's 1995 or 1997 Annual about bullet design for black powder cartridges that goes in depth, and is about as understandable to the layman as anything I've read on the subject. It goes into the technical side of this just enough to help understand the parameters at work, and how they're best dealt with technically and through history.

Those books were on sale for a long time, but I haven't subscribed in several years - probably a mistake on my part. I think they were available for $5 a copy at one time. Put "Precision Shooting Magazine" in a google search, and see if you can find them. Dang good books, and worth the asking price even if the discount's no longer in effect - IF they still have them, of course.

[montana_charlie]

should I develope it in a way that at the maximun range of 200 yards the speed of the bullet would be obove the speed of sound...or my question put in another way .... does the transition from supersonic to subsonic affect the accuray and to wich point...
This is another subject kinda like 'fluxing to save tin'. A non-scientific type can read the theories carefully enough to believe he understands...then he 'translates' the science into terms he is comfortable using. How much of the science gets lost in that 'translation' is the question.

I understand that, as an object's velocity increases into, or decreases below the speed of sound, it is affected by a form of turbulence not related to weather.
I have come to believe (after my personal 'translation'), BPCR bullets shed speed at a rate that causes them to spend a rather lengthy time in that transonic velocity range. A bullet (of a given design) that was in stable flight while supersonic, might lose that stability if exposed to the transonic turbulence for long enough, and the BPCR bullet is likely to be asked to do it's work after contending with that 'long period of turbulence'.

Testing seems to prove that the 'average' BPCR bullet falls below the speed of sound at a range just greater than 300 yards. A question for the long range shooter is, "Is my bullet still flying well after it has passed through that transonic turbulence?"
For that reason, some will only test their ammunition at ranges exceeding 350 yards. They feel that 100 yard shooting may be OK for aligning sights, but little else.

This author's question involves (what would be considered) short range shooting, so he can expect his bullet to remain above the speed of sound for the entire journey, if the muzzle velocity is high enough.

This should allow him to build ammunition which allows a second (or third) shot with no need for fouling control, and which can stand rough handling. What is not required is hair-splitting accuracy, nor a search for the aerodynamically perfect bullet.

A bullet that kills well and punches a round hole is adequate, and the charge needs to be large enough to achieve SOS at the muzzle.
CM

[Larry Gibson]

OK, at 70°F, the speed of sound in air is 344 M/S, which converts to 1128.6 FPS.

Quite correct. There are other atmospheric conditions that effect the speed of sound through air but the 1128 fps is pretty much accepted. However when refering to object moving through air the sonic barrier is lower for blunt objects, expecially blunt bullets with large diameters. A bullet goes trans sonic when the speed of the air moving around the bullet exceeds the speed of sound. Given two .45 caliber bulltes, one a spitzer and one a round nose, the air must move faster (farther) to get up and around the round nose bulet. Hence round nose or blunt nose bullets will begin "breaking the sound barrier" when the bullet is traveling 1050 fps, some more and some less simply because the air moving around the bullet is faster than the speed of sound. Therefore it is diffuclt to say what the sonic transition range is for a bullet without testing. It is easy to do if one has a sound suppressor and a chronograph. Most do not have a suppressor so the best thing is to put targets out to 200 yards as Felix suggests at shoot for groups. I'd go with the lighter bullet unless you're talking about hunting really big big game.

Larry Gibson

[Dale53]

Shooting extensively at BPCR silhouettes I have found light bullets in the 45/70 and 40/65 (350 45/70 and 300 in the 40/65) to work well until just before the Turkey range (385 yards) but do NOT do well on the Rams. I am talking accuracy here, NOT knock down. Accuracy is marginal at the turkey but very good to excellent on the pigs (200 meters) and chickens (100 meters).

I have limited my range on deer with the 45/70 class of cartridges to a max of 200 yards. Actual range time has shown me that I don't have a "theoretical" problem at the ranges that I plan to shoot deer. This has been mostly with black powder (both straight and duplex loads) but I have done enough smokeless work with these cartridges to feel confident in my parameters. I like the 350's in the 45/70 and KNOW that they will do the job on deer at appropriate ranges.

I don't use a rangefinder and with the trajectory of this class of cartridges 200 yards is far enough for me. I shoot well but I can't judge range at lengthy ranges well enough that I am going to take a chance on shooting a deer "around the edges". It's is not quite like a steel target. Live animals bleed and hurt and I don't intend to add to their misery any more than necessary to harvest them.

Shoot center!
Dale53

[44man]

I have a pile of molds for my BPCR and the biggest problem is stability beyond 300 meters. I have several boolits that match the twist (18) and look like they should shoot but just go crazy at long range. Some that look poor, like the gov't round nose actually stay stable.
I still have the boolit that 45 2.1 designed for me to test. I have just not been able to get to the club yet. I know he is waiting for results. I have only been able to test it at 200 and it shot great.
For 200 yd's or less, anything I shoot is good enough.
The real surprise is my 45-70 BFR revolver and my flat nose boolit. (LBT style) I have shot these a lot at 500 meters and although the drop is horrible at 26 feet, they stay stable and watching them in a scope doesn't show the wobble that starts with my BPCR boolits.
I also have shot my .475 Linebaugh, flat nose, truncated cone boolit at 400 and 500 yd's with amazing accuracy, keeping most shots on a small swinger target. There is no indication of bad flight in the scope.
I have read a thousand times that the flat nose is bad at anything past 50 yd's. You will never prove it by me. I have none of the problems with them that the long, pointy nose boolits give me. Someday I am going to make a long boolit with a flat nose to test with my BPCR.
The whole point is that boolit design is more important then the transition to sub sonic flight. BPCR is the hardest sport I ever started and those that win all the time have the perfect mix of boolit to load, to barrel, bottom line. A poor boolit and/or rifle will keep your scores low no matter how good a shot you are. You also need a lot of money to keep buying rifles, molds and barrels until one works.
My suggestion for 200 yd's and under is to find a boolit shape and alloy that kills deer, sight in, learn the sights and go hunting.

[Dale53]

It took me quite a while to learn to shoot BPCR-Silhouette. Then, about the time I had "arrived" my vision left. by the time the NRA dicked around allowing scopes it was too late for me (and a LOT of old timers). However, I have a friend that I introduced to BPCR and he is shooting up a storm (several State Championships (different states) and tied at Raton on silhouette last year and came in 4th or 5th at Long Range. He keeps me up to date on the latest developments even if we do live a couple of states apart.

My first 40/65 had an 18" twist and my second had a 16" twist. "C. Sharps" stated that twist was a non-issue in this caliber (either 16 or 18 being just fine) but if I had my druthers it would be 16". I like 18" in the 45/70. Of course, for lighter bullets and hunting (think max 200 yards) the original 22" twist would probably be just fine in the 45/70. When you talk the longer ranges and heavier (longer) bullets a faster twist (18") would be my choice.

I sure know where you are coming from with buying rifles and bullet moulds. I was raising a family when all of that was going on and I was certainly limited in available funds (as were most of the people I was shooting with). You cannot buy a win in BPCR Silhouette but that doesn't keep some from trying it:mrgreen:

Good game, that is for sure. I surely enjoyed it but now it has to be a thing of the past for me (he said wistfully, with a catch in his throat).[smilie=1:

Dale53

[44man]

It might be hard to buy high scores but all of the guys that win every shoot here all own their own businesses. Those that don't have more money too and are always having custom guns built or build them themselves with special barrels. I could not even touch one of the actions let alone build a rifle with all of the expense.
The top shooters think nothing of shooting more boolits in a day for practice then I can make in a month. They go through tons of lead and powder.
That costs money, lots of money! Good black powder alone is very expensive and when you only get 100 shots a can, best have some money. Lead and tin is not cheap!
Some shooters drive from two states away, come a day ahead of time with a camper that costs half as much as my house and shoot all day friday before the shoot on Saturday.
It's like the old saying; if you can afford the monster truck, you can afford the gas.
It is getting harder and harder all the time to compete with the cost for components plus entry fees that continue to go up, then add gas to get there. Then each year you have to pay for the score book.
Soon, I will have to quit and just keep shooting in my woods for fun.
Any shooting sport is now a rich man's sport. I have had to give up IHMSA, archery, muzzle loader and shotgun competition, soon to be followed by BPCR.
Retired sucks! No more overtime.