.338 Whisper?

[mks]

Keith,

I've got a Merrill with a 10", 10 twist 32-20 barrel and a .308 bore. I've always shot 110 grain Sierra HP's in it ahead of 296. Kind of like a scaled down 357 mag. You've got Quickload, don't you? Give me something for 175 and 210 SMK's Loaded length looks like 2.00" and 2.20" with my throat. We can call this one the Peeper.

Thanks

Greg

No, I don't have Quickload. What powder and case capacity would we need for the Wooper/Wopper?

 

[Peter]

The 50AE is probably the best option. I've done one off the 458 socom necked up but there was way more room than necessary for a subsonic charge. 24 gr of AA#9 will get you to 1040 with 647 ball.... in the 510 whisper.

 

[Greg Culpepper]

No, I don't have Quickload. What powder and case capacity would we need for the Wooper/Wopper?

I don't have a clue. I'm a concepts man. I'll fire up the old wet finger in the wind analog ballistic computer and see if anything falls out the bottom.

 

[Greg Culpepper]

Keith,

I think we're inventing the 500 Linebaugh.

 

[Charles E]

OK guys, time to stop being clever -- or only clever -- and do some work. Now I know a lot of the work can only be done at the range, but if buying a barrel, reamer & dies are involved, some headwork up front should save a few bucks.

As a sop to Greg, I've shot Hunter Silhouette with a T/C Contender 32/20, 308 bore. In my notes, I have a listing of 12 grains 4227 (MAX load for strong, modern firearms) for a 150-grain bullet. After that, you're on your own, though I do have some data for a .30 Herrett with up to 180-grain bullets. And I do have a 10-twist Herrett barrel for the T/C...

* * *

So, first thing: this is a competition round. It has to group about .040 less than caliber size, for 25 shots, or it's no improvement on the .30BR. Second thing: it has to have less wind drift. If not, again no advantage. Match grade bullets needed. If jacketed lead, I imagine this is .338 or maybe the .50s, or just possibly, a 416. If solid copper, I suppose some the Barnes triple-shock X or Hornady's Tac-X would work. Barnes even has a .50 BMG 647-grain triple-shock X bullet at $31.50 for 20, and Hornady a Tac-LR 750-grain .50 BMG for $36 for 20.

(I seem to remember Shehane remarking that solid copper bullets needed a different rifling profile? This when he was working up a .505 Gibbs for somebody.)

But there are pluses, too. Don't care how it feeds through a magazine. Don't care about drop at 100 or 200 yards. We can assume a very good barrel, dies, and reloading technique. In reading over Whisper postings on other sites, most talk about 1-2 inch groups, but some people are reporting 0.5 inch groups. Maybe they're improving the tale, maybe not. Finally, it doesn't have to be subsonic, though I can't imagine a MACH 1.5 chambering that wouldn't kick like a proverbial mule.

Now, Keith mentions velocity variations. OK, why is that? I imagine it's more than dropped instead of weighed charges. What else is there? The case too big for good loading density; i.e., even ignition? The kind of powder? I remember Jack O'Conner remarking that powders had a preferred pressure to burn at, over or under this region, accuracy wasn't as good. Old wives tale, or true?

Thoughts? Esp. useful ones...

 

[mks]

Keith,

I think we're inventing the 500 Linebaugh.

That's it!

 

[mks]

Now, Keith mentions velocity variations. OK, why is that?

Charles,
Just because muzzle velocity variations are impossible to eliminate. Any BR cartridge must perform in spite of muzzle velocity variations. With a ballistics calculator, I estimated that a 30BR (BC of 0.29 and velocity of 3050 fps) will have 0.3 bullet diameters of vertical from an ES of 20 fps at 200 yards from a fixed muzzle. Not a big problem. But the 510 Wooper/Wopper (BC of 1.05 and velocity of 1050 fps) will have 3.2 bullet diameters of vertical from the same ES at the same yardage. Big problem. The faster bullet will hit the nine ring high and the slow bullet will hit the nine ring low. For the big bullet to work, the ES has to be extremely small, like 2-3 fps, or the rifle needs to be tuned to compensate for the different bullet exit times. That small an ES may be impossible. Tuning with the barrel may not be possible either, barrels are too stiff. Tuning with a flexible stock may be the best approach.

Keith

 

[Charles E]

Charles,
Just because muzzle velocity variations are impossible to eliminate. Any BR cartridge must perform in spite of muzzle velocity variations. With a ballistics calculator, I estimated that a 30BR (BC of 0.29 and velocity of 3050 fps) will have 0.3 bullet diameters of vertical from an ES of 20 fps at 200 yards from a fixed muzzle. Not a big problem. But the 510 Wooper/Wopper (BC of 1.05 and velocity of 1050 fps) will have 3.2 bullet diameters of vertical from the same ES at the same yardage. ... Keith

I'm confused. Is this an acceptable ballistics calculator?

http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi

Because when plug in the numbers for the 710-grain A-max, then I reduce the velocity 30 fps, I get essentially no change in point of impact -- drop -- at 100 yards. And I'm using total drop; I didn't start with a 100 yard zero (that would have been a big mistake, of course).

This, like all the programs I'm familiar with, work in inches, not calibers. Which makes me think you're referring to something else entirely...

 

[mks]

I'm confused. Is this an acceptable ballistics calculator?

http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi

Because when plug in the numbers for the 710-grain A-max, then I reduce the velocity 30 fps, I get essentially no change in point of impact -- drop -- at 100 yards. And I'm using total drop; I didn't start with a 100 yard zero (that would have been a big mistake, of course).

This, like all the programs I'm familiar with, work in inches, not calibers. Which makes me think you're referring to something else entirely...

Charles,
I didn't have a ballistics calculator that would directly calculate the difference in drop that we are looking for. I used the Hornady online calculator, but the JBM works the same as far as I can tell. You have to input a muzzle velocity and a zero range for each case. The program automatically adjusts muzzle angle for each case. I used 1040 and 1060 fps velocities and 100 yard zero range, and checked the drop at 200 yards.

This isn't exactly correct for the cases we want to compare, which would be a muzzle fixed at an angle that gives 200 yard zero range with say 1050 fps, but with +/- 10 fps muzzle velocity. So my numbers are just an "estimate," maybe not correct for each caliber, but good for comparing one to the other.

I divided the differences in drop in inches by the bullet diameter, because bullet diameter is a measure of how far off the bullet strike can be and still hit the dot. For one bullet diameter of difference, half up and half down, the two holes each still wipe out half the dot.

Cheers,
Keith

 

[Greg Culpepper]

The 50AE is probably the best option. I've done one off the 458 socom necked up but there was way more room than necessary for a subsonic charge. 24 gr of AA#9 will get you to 1040 with 647 ball.... in the 510 whisper.

Peter,

I'm very interested in what you learned, Would you share more of your observations with us?

Thanks,

Greg

 

[Charles E]

Keith,

Hmmm. May just be the JBM program, but if I change the caliber to .338 (from .50), and the bullet weight to 300 grains (from 710), but leave the B.C. alone (bullet is now made out of unobtainium), I get the same numbers. And if I use a 10-inch scope height, rather than 2 inch, things get much worse.

I think that silly program is only computing gravity drop -- 32ft/sec^2 -- for the time of flight, and your "muzzle angle" is simply a function of scope height.

 

[Greg Culpepper]

OK guys, time to stop being clever -- or only clever -- and do some work. Now I know a lot of the work can only be done at the range, but if buying a barrel, reamer & dies are involved, some headwork up front should save a few bucks.

Can a straight sided chamber reasonably be cut with a boring bar and a throating reamer? How about a zero freebore chamber with boring bar only? Commercial pistol dies for 50 AE or 500 Linebaugh are affordable.

As a sop to Greg, I've shot Hunter Silhouette with a T/C Contender 32/20, 308 bore. In my notes, I have a listing of 12 grains 4227 (MAX load for strong, modern firearms) for a 150-grain bullet. After that, you're on your own, though I do have some data for a .30 Herrett with up to 180-grain bullets. And I do have a 10-twist Herrett barrel for the T/C...

Thanks Charles
* * *

So, first thing: this is a competition round. It has to group about .040 less than caliber size, for 25 shots, or it's no improvement on the .30BR. Second thing: it has to have less wind drift. If not, again no advantage. Match grade bullets needed. If jacketed lead, I imagine this is .338 or maybe the .50s, or just possibly, a 416. If solid copper, I suppose some the Barnes triple-shock X or Hornady's Tac-X would work. Barnes even has a .50 BMG 647-grain triple-shock X bullet at $31.50 for 20, and Hornady a Tac-LR 750-grain .50 BMG for $36 for 20.

I think a banded or grooved bullet would be a poor choice for reasons of drag. We're chasing low drift here and at subsonic velocities air flow is laminar around a smooth sided bullet. Grooves in the side will produce turbulance, more drag, more time lag and more drift. This isn't much of an issue at supersonic speeds as the grooves are in the low pressure cone of the shock wave where they can't add much to drag.

(I seem to remember Shehane remarking that solid copper bullets needed a different rifling profile? This when he was working up a .505 Gibbs for somebody.)

But there are pluses, too. Don't care how it feeds through a magazine. Don't care about drop at 100 or 200 yards. We can assume a very good barrel, dies, and reloading technique. In reading over Whisper postings on other sites, most talk about 1-2 inch groups, but some people are reporting 0.5 inch groups. Maybe they're improving the tale, maybe not. Finally, it doesn't have to be subsonic, though I can't imagine a MACH 1.5 chambering that wouldn't kick like a proverbial mule.

Well, I think subsonic MV is going to be crucial. Time lag and wind drift at MACH 1.5 are huge compared to subsonic as rimfire science and experience prove at exactly the same speeds as we are discussing.

Now, Keith mentions velocity variations. OK, why is that? I imagine it's more than dropped instead of weighed charges. What else is there? The case too big for good loading density; i.e., even ignition? The kind of powder? I remember Jack O'Conner remarking that powders had a preferred pressure to burn at, over or under this region, accuracy wasn't as good. Old wives tale, or true?

Thoughts? Esp. useful ones...

I wouldn't dare being clever but the smallest ES I have seen on a chronograph has been in BPCR loads with black powder. I'm talking about ES of 1 fps just like a compound bow or a match pellet gun. It is a fact that these loads used lead bullets not jacketed and they were well engraved in to the rifling when chambered. How much does engraving force variation add to ES. Just wondering.

The convenient thing about a short, straight case and a long bearing surface bullet is you can experiment with case capacity and powder selection as a determinant of ES just by varying seating depth. Once you've determined a promising loaded length overall you can pick a case length and freebore and set back/re-chamber the barrel.

The thing about old wives tales is that if you can't afford science, they might beat nothing. Sort of like the Law Of the Old West trumping inaction if a law firm or cop is not presently convenient.

Greg

 

[mks]

Keith,

Hmmm. May just be the JBM program, but if I change the caliber to .338 (from .50), and the bullet weight to 300 grains (from 710), but leave the B.C. alone (bullet is now made out of unobtainium), I get the same numbers. And if I use a 10-inch scope height, rather than 2 inch, things get much worse.

I think that silly program is only computing gravity drop -- 32ft/sec^2 -- for the time of flight, and your "muzzle angle" is simply a function of scope height.

Right, the drop doesn't depend on caliber or weight, just BC and muzzle angle, velocity, etc. It isn't quite as simple as just 32 ft/sec^2, but that's the main term for anything close to flat fire. The peeve I have with current ballistics programs is that you can't set muzzle angle, it is buried in the program. it isn't just a function of scope height, but also of your choice of zero range, the cartridge, head/tailwind, etc.

 

[mks]

I think a banded or grooved bullet would be a poor choice for reasons of drag. We're chasing low drift here and at subsonic velocities air flow is laminar around a smooth sided bullet. Grooves in the side will produce turbulance, more drag, more time lag and more drift. This isn't much of an issue at supersonic speeds as the grooves are in the low pressure cone of the shock wave where they can't add much to drag.Greg

Actually, subsonic flow is not automatically laminar. In fact, the flow on the bullet is probably laminar on the front, transitioning to turbulent on the back. Remember the reason for dimples on a golf ball? Grooves on a subsonic bullet could be beneficial, if they were in the right place.

I wouldn't dare being clever but the smallest ES I have seen on a chronograph has been in BPCR loads with black powder. I'm talking about ES of 1 fps just like a compound bow or a match pellet gun. It is a fact that these loads used lead bullets not jacketed and they were well engraved in to the rifling when chambered. How much does engraving force variation add to ES. Just wondering.

The convenient thing about a short, straight case and a long bearing surface bullet is you can experiment with case capacity and powder selection as a determinant of ES just by varying seating depth. Once you've determined a promising loaded length overall you can pick a case length and freebore and set back/re-chamber the barrel.

The thing about old wives tales is that if you can't afford science, they might beat nothing. Sort of like the Law Of the Old West trumping inaction if a law firm or cop is not presently convenient.

Greg

Maybe I spoke too quickly about low ES being impossible. Maybe ES naturally scales with muzzle velocity and would be smaller for subsonic loads? Someone who has cronographed pistol loads would know this.

Interesting about black powder and engraved bullets. I have also wondered if jacketed bullets fully engraved into the lands would perform any better than the same bullets jumping into the lands.

Cheers,
Keith

 

[Greg Culpepper]

Actually, subsonic flow is not automatically laminar. In fact, the flow on the bullet is probably laminar on the front, transitioning to turbulent on the back. Remember the reason for dimples on a golf ball? Grooves on a subsonic bullet could be beneficial, if they were in the right place.

Keith,

Spheres and streamlined bullets behave differently. While the dimples on a golf ball do reduce drag they will not help a bullet. You could say that the bullet shape is a drag optimized modification of a sphere. Dimples are the best you can do if you have to leave a sphere a sphere. The longer you can keep air attached to an object (laminar) before it breaks off in turbulence the lower its drag will be, hence boattails. There is a good discussion of why dimples don't help on other shapes at www.aerospaceweb.org/question/aerodynamics/g0215.shtml/. There is no right place to put grooves (or dimples) on a streamlined bullet to lower subsonic drag.

My link doesn't work. Google "golf ball dimples and drag" or go to aerospaceweb.org and search for the same.

Maybe I spoke too quickly about low ES being impossible. Maybe ES naturally scales with muzzle velocity and would be smaller for subsonic loads? Someone who has cronographed pistol loads would know this.


Interesting about black powder and engraved bullets. I have also wondered if jacketed bullets fully engraved into the lands would perform any better than the same bullets jumping into the lands.

Cheers,
Keith

I haven't tried to refine pistol ammo accuracy by chasing low ES. It's just been checking average velocity of a known accurate load. I've found loads accurate enough for the task without getting LRBR obsessive about it.

I have chrono'd rimfire ammo toward those ends however. What I found was a very strong correlation between low ES and observed accuracy. The most accurate was Fed UM 1 (not the lower velocity UM1 B) which had a 10 shot velocity spread of 7 fps. Eley Tenex black box was next most accurate with an ES of 12. Most lesser match ammo showed ES's of 18-25 fps. Discount ammo and High Speed ammo were likely to show greater than 25 fps ES on ten shot strings. I don't know how low an ES could be achieved with careful ammo prep in our subsonic 50 but with smokeless powder it might not be enough for the task without a tuner strategy layered on top. I am left wondering if you can get 1 fps ES out of a jacketed bullet with and BP aa I've seen with a lead bullet.

Greg

 

[mks]

Keith,

Spheres and streamlined bullets behave differently. While the dimples on a golf ball do reduce drag they will not help a bullet. You could say that the bullet shape is a drag optimized modification of a sphere. Dimples are the best you can do if you have to leave a sphere a sphere. The longer you can keep air attached to an object (laminar) before it breaks off in turbulence the lower its drag will be, hence boattails. There is a good discussion of why dimples don't help on other shapes at www.aerospaceweb.org/question/aerodynamics/g0215.shtml/. There is no right place to put grooves (or dimples) on a streamlined bullet to lower subsonic drag.


Greg

Greg,
That is a nice article that you reference, but it doesn't support the conclusions you make from it. A sphere is not a special shape that is the only one that can benefit from dimples or other boundary layer trips. For instance, vortex generators are used on airplane wings and ridges were used on the America's Cup yacht, and neither of these are spheres. Bullets, and most other objects in external flow, have regions of adverse pressure gradient that can lead to boundary layer separation. The purpose of the trip is the same in all cases - to add momentum to the boundary layer to move the point of separation downstream. The place on bullets where trips might work is just upstream of wherever separation occurs on smooth bullets.

http://www.nennstiel-ruprecht.de/bullfly/fig4.htm

Above is a picture of a short subsonic bullet that does not have boundary layer separation upstream of the tail, but it has a groove, so we don't know if separation might have occurred without the groove. Longer subsonic bullets would be more likely to have separation, and could benefit from trips.

http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA219106

Here is an article by McCoy with shadowgraphs of subsonic 50 cal bullets that also don't show separation before the boat tail. But these bullets also have grooves upstream of the boat tail.

Another point that can be seen in the figure of the dimpled golf ball in the article is that both laminar and turbulent boundary layers can be attached, and both laminar and turbulent boundary layers can be separated. The separation point does not necessarily coincide with transition from laminar to turbulent flow.

Cheers,
Keith

 

[Melvin Calliham]

Keith,

I've got a Merrill with a 10", 10 twist 32-20 barrel and a .308 bore. I've always shot 110 grain Sierra HP's in it ahead of 296. Kind of like a scaled down 357 mag. You've got Quickload, don't you? Give me something for 175 and 210 SMK's Loaded length looks like 2.00" and 2.20" with my throat. We can call this one the Peeper.

Thanks

Greg

I shoot the 32-20 with .308 bore(30-20) in my MOA and RPM silhouette handguns, bot with 10.75" barrels. I use 10.0 grs. Vihta Vhouri N-110 with a fed 205M, and a Nosler 190 Custom Competition bullet, velocity is 1280 fps, ES 17, SD 7. The twist is 1:10 in both guns. Very accurate out to 200 meters, and low recoil
Melvin calliham

 

[Greg Culpepper]

Thanks Melvin,

That's exactly what I was looking for. As you know The Merrill was made by RPM and re-named X-L when Jim decided that the accumulated improvements to the pistol had outrun the license from Rex. I always shot the 32-20 at NRA Hunter100 yd pistol events with a scope and used a 14" 7 Rocket barrel with irons for the 200 M. IHMSA events. Wish I'd been clever enough to use longer bullets in the 32-20 thirty years ago. At least we figured out to use 200 gr spitzers and 38 cases in our 357 mag revolvers.

Greg

 

[Melvin Calliham]

Hey, Greg
Lot's of changes in IHMSA, especially since they incorporated the topple rule many years ago. It doesn't take a lot of power to knock over the ram now, although the load mentioned above has a terminal momentum of around 1.00. I started shooting IHMSA in 1981, and have been shooting it since.When I first started, we used full house loads in 30-30 in 10" barrel Contenders for Production class, and still would leave a ram.Ole Jim Rock is still going strong!! Still making the RPM. I used to shoot at Charlotte Rifle and Pistol club with Jim Bost, Tommy Abernathy, Tommy Helms, Bill Shehane, Harry Frady, and a bunch more I can't remember.
MC

 

[Greg Culpepper]

Greg,
That is a nice article that you reference, but it doesn't support the conclusions you make from it.

As I noted in my post, the link didn't work.
I'm not sure which article you reference but if its the one titled "Golf Ball Dimples & Drag, Can you explain why a golf ball has dimples? If dimples reduce drag, why don't we see this surface feature on other aerodynamic shapes like airplane wings?" (or bullets, ed.) I didn't draw conclusions from it. I referred you to it so I wouldn't have to write as much. If we're talking about the same page it does support my contention that dimples or ribs or whatever don't improve drag on bullets

A sphere is not a special shape that is the only one that can benefit from dimples or other boundary layer trips.

Sure it is. The only thing you can do to a sphere to lower its drag is to alter its surface to create turbulence. This allows the turbulent air to travel farther around the curve of the ball before it breaks off than laminar air will. This produces a smaller wake behind the ball and lower drag. But there is a price. You get more drag on the front of the ball. Its less additional drag than what you save at the back but its there. Do anything else to sphere than alter its surface and its not a sphere anymore. The issue here is that as soon as you stretch into an elongated shape to reduce the size of the low pressure wake at the back you no longer have a shape that gains more on the back than it losses on the front when you alter the surface. (Please don't tell me about dolphin skin or Olympic swim suits.)

For instance, vortex generators are used on airplane wings and ridges were used on the America's Cup yacht, and neither of these are spheres.

Vortex generators reduce surface drag on aircraft wings and postpone separation at high angles of attack to postpone stalls. They do not reduce drag at the front or the rear of the wing. The only things I know about America's Cup racers is that they have strict rules about length at the waterline because the longer a boat is, the faster it is. Also they ain't cheap. Even Ted Turner doesn't use them once and throw them away. Well, maybe he does but he doesn't like it.

Bullets, and most other objects in external flow, have regions of adverse pressure gradient that can lead to boundary layer separation. The purpose of the trip is the same in all cases - to add momentum to the boundary layer to move the point of separation downstream. The place on bullets where trips might work is just upstream of wherever separation occurs on smooth bullets.

Now the thing to do here is not create turbulence to postpone separation, just don't create the separation with a poor shape to begin with.

http://www.nennstiel-ruprecht.de/bullfly/fig4.htm

Above is a picture of a short subsonic bullet that does not have boundary layer separation upstream of the tail, but it has a groove, so we don't know if separation might have occurred without the groove. Longer subsonic bullets would be more likely to have separation, and could benefit from trips.

http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA219106

Here is an article by McCoy with shadowgraphs of subsonic 50 cal bullets that also don't show separation before the boat tail. But these bullets also have grooves upstream of the boat tail.

Keith, this is a little like saying, "See that guy over there with the yellow tie? His pants didn't fall down. Could be the tie."

Also notice the shock wave originating at the cannelure at mach 1. The shock wave at the nose is no longer visible but the cannelure is still dragging like all getout. At mach 0.9 there is still drag there that adds nothing but drift. Now if you want to lower the drag of a subsonic 50 BMG bullet the place to start might be to turn it around backwards, round off the boat tail and shape it more like a WWII airplane drop tank.

Another point that can be seen in the figure of the dimpled golf ball in the article is that both laminar and turbulent boundary layers can be attached, and both laminar and turbulent boundary layers can be separated. The separation point does not necessarily coincide with transition from laminar to turbulent flow.

Well, you don't know what a relief it is to completely agree with you on this.

Cheers,
Keith

Cheers back atcha,

Greg