Improving the speeds of a .22

[mjsdwash]

fins are to stabilize, and do not add energy. Actually, they remove energy, because they create drag. Drag has a stabilizing effect. Sorry if this is redundant.

 

[Riomouse911]

Huh? Let's say you get 1000 fps from a 12" twist pistol barrel. So it is turning once per foot traveled, 1000 revs per second, therefore 60,000 rpm.

For those who may not know, Vx720/T is the formula. It sure looks like I missed one on my phone calculator, too.

1,000 x 720 = 720,000
720,000 / 12 = 60,000

A .44 Spl at 800 fps from a 1/20 twist revolver runs 28,000 +\- rpm.

A .223 bullet from a 1/7 at 3000 is a bit over 308,500 rpm, etc.



Stay safe

 

[Jim Watson]

Completely unrealistic.

Now, a pair of little tiny tanks, containing fuel and oxidizer, combined with a gyro and a microchip, all fitted inside the bullet, would really be something. The remote control would require a bit of juggling, course. You'd have to put the gun down right quick, but I'm sure a bit of practice would sort things right out.

Solid fuel is cheaper. Ref. Gyrojet.
Or Brunner Kazow,

 

[jmorris]

Well a 6mm produces more energy due to higher swept volume. Thats why the 6mm creedmoor has far higher energy than any .22

Well its to do wih piston area....a wider bore means more muzzle energy....thats how he 300blackout manages to get more power than a 556.

The calculation for kinetic energy has two variables Mass and Velocity.



Volume, piston area, bore diameter, has nothing to do with the calculation.

Velocity is a limiting factor I’ve seen sabot rounds go in the low 5000 fps range and “The .220 Swift remains the fastest commercial cartridge in the world, with a published velocity of 1,422 m/s (4,665 ft/s) using a 1.9 grams (29 gr) bullet and 2.7 grams (42 gr) of 3031 powder.” Handbook for shooters and reloaders volume 1 P.O. Ackley

The other limiting factor, Mass, is only related to diameter in how much of it you can get before the length becomes the problem.

Once you get a .224 bullet up to the mass of some .30 cal bullets, they are longer than the Max OAL of a .223 bullet/case combination. Here is a good example from someone that blew up a rifle, that illustrates the point.



So, if you want anything to have more energy, you need to get it going faster, make the projectile heavier (without loosing velocity) or both.

 

[Varminterror]

Volume, piston area, bore diameter, has nothing to do with the calculation.

They do when considering KE(Max) = PE(powder), and KE(net) = n*PE(powder), related by combustion efficiency, less bore drag, influenced by the pressure retained in the bore, predicated by the expansion ratio (bore volume dependent). The KE formula above only describes the external ballistic starting point of the Bullet once released from the bore, but the pressure curve behind it integrated to a net pressure as a function of expansion ratio and bore area to determine net relative force on the base of the bullet during dwell time dictates the resulting muzzle velocity, and such, KE at the muzzle.

The premise of using “fins” as driving bands is ridiculous, and again, the idea posited by the OP simply doesn’t pencil. But bore diameter does matter - just not in the underconsidered manner the OP has proposed.

 

[jmorris]

If we were talking about internal ballistic factors we would have to consider other possibilities.

Well a 6mm produces more energy due to higher swept volume. Thats why the 6mm creedmoor has far higher energy than any .22

Swept volume isn’t only dependent on bore diameter. Swept volume can be increased by bore diameter but increasing the length of a barrel will also increase the swept volume, even with a fixed diameter.

Well its to do wih piston area....a wider bore means more muzzle energy....

If that were the case a 12ga shotgun would be more powerful than a 50 BMG.

 

[Jim Watson]

If it were a 20mm it would be.
There was an experimental round, the 16mm Vega; .50 necked up. The objective was a large enough caliber for a worthwhile explosive shell in the common aircraft Browning, just change the barrel.

 

[someguy2800]

Your driving bands would have to be pretty big diameter to get up the same bore area as a 6mm

 

[someguy2800]

Google “expansion ratio”.

The 223rem has a limited case volume, meaning a limited powder charge of potential energy. The net kinetic energy out is the result of the pressure of the sealed bore behind the bullet over the duration of the dwell time.

Expand the bore diameter, effecting nothing else, then you have increased the expansion ratio, so the “piston” system loses force (pressure) exceptionally fast.

We can shoot the same bullet weight in 6-45 as we shoot in standard 223, over relatively similar charge weights. The results are underwhelming. It takes about 15% more powder in the case to produce the same velocity behind the 6mm as the smaller diameter 22 cal, because the expansion ratio is simply too great, and the small powder charge is not able to sustain the pressure curve in the larger bore.

This entire thread indicates a gross misunderstanding of physical principles. The guy is assuming constant pressure curve as the bore is enlarged, which simply won’t happen.

That is just not true. Comparing almost any cartridge variation with the same parent case, same bullet weight, same barrel length, and same peak pressure, the larger bore diameter will always net higher muzzle velocity within normal rifle barrel lengths.

 

[.308 Norma]

Deleted.

 

[richalexander97]

Careful with those missing zeros.

Anyway, I don't think the why has been answered yet? And if you want Creedmore energies, use a Creedmore.
Btw, could you explain this better?

Let's just use a number like 2400 ft-lbs for the 6.5 Creedmore using a 120 grain Amax at around 3000 fps (just for example) -- then I would expect to launch my hypothetical 55 grain 22 bullet at about 4435 fps to match the Creedmore energy in this example. It would be hell on the bore, especially around the throat area so again I ask, why? A 40 grainer would have to be in the neighborhood of 5200 fps and a heavy 80 grainer would need to be traveling around 3675 fps. Again, why?
I'm hoping you'll be able to explain your fin idea in more detail. I'd really like to hear it.

As ive said many times, the idea is not for the fins to stabilise the bullet. It would still have a twist....hopefully a slow one.

No...the idea was for these 'lumps' to increase the bore diameter up to 6mm. This creates the same effect as a sabot and allows for far higher energies. Its just like a 300black which has more power than 556 despite using the same case.

All i wanted to know is....would it work. With, say, polygonal rifling, which shouldn't disturb the fins.
Obviously u need a wad behind the bullet to create a seal.

 

[CapnMac]

Its just like a 300black which has more power than 556 despite using the same case.

Ah, but they don't, use the same case, that is. They have the same case head dimension, and the chamber diameter is similar--see the photo above.

So, it's not a situation where we can just add some lumps to get a given diameter.

Especially not when, if this were the desired result, it would be "easier" to just neck a 5.56 case to 6mm. Sadly, the selection in .224 rounds is not all that great. And, necking a 5.56 case up to 6.5/.256 is pushing things a bit. Especially given the number of existing 6.5 rounds already in existence making a .256/5.56 wildcat kinda dumb.

 

[someguy2800]

Ah, but they don't, use the same case, that is. They have the same case head dimension, and the chamber diameter is similar--see the photo above.

So, it's not a situation where we can just add some lumps to get a given diameter.

Especially not when, if this were the desired result, it would be "easier" to just neck a 5.56 case to 6mm. Sadly, the selection in .224 rounds is not all that great. And, necking a 5.56 case up to 6.5/.256 is pushing things a bit. Especially given the number of existing 6.5 rounds already in existence making a .256/5.56 wildcat kinda dumb.

6.5 is .264. There is a 6.5 wildcat based on the 5.56 case called the 6.5 tcu. It is just a 5.56 case necked up and the shoulder blown out. It was a very popular metallic silhouette round. They also made 6mm and 7mm versions and the dies are still readily available. There is also a .257 one called 25-45 sharps which has reached some popularity and one similar to 300 blackout in that it uses a shortened 5.56 case and .277 bullet which is called 277 wolverine.

 

[Jim Watson]

The OP wants fins, let him have fins.

When the Army was looking at flechette rifles, they typically had very slow twist rifled barrels. The purpose was to separate the sabot by centrifugal force; ballistic stabilization was by fins.

 

[Varminterror]

That is just not true. Comparing almost any cartridge variation with the same parent case, same bullet weight, same barrel length, and same peak pressure, the larger bore diameter will always net higher muzzle velocity within normal rifle barrel lengths.

When the case has enough powder to do the job - in other words, enough potential energy to sustain sufficient pressure curve behind the bullet.

In most cases (cartridge cases), we do have enough overbore capacity to overcome the increasing expansion ratio. But the x45 case in question is an example of where our bore can exceed our cartridge capacity. It ain’t the same comparison as the 338 and 7RM, or 7-08 and 308. It’s closer to the relationship between 22LR and barrel length, where we run out of potential energy before we run out of bore.

Hence why so many folks are pointing to larger cases here to accomplish the goal.

 

[someguy2800]

When the case has enough powder to do the job - in other words, enough potential energy to sustain sufficient pressure curve behind the bullet.

In most cases (cartridge cases), we do have enough overbore capacity to overcome the increasing expansion ratio. But the x45 case in question is an example of where our bore can exceed our cartridge capacity. It ain’t the same comparison as the 338 and 7RM, or 7-08 and 308. It’s closer to the relationship between 22LR and barrel length, where we run out of potential energy before we run out of bore.

Hence why so many folks are pointing to larger cases here to accomplish the goal.

Even in the x45 and smaller cases it is not true. A 223 will push the same weigh bullet faster than a 20 practical. A 6x45 will push the same weight bullet faster than a 223. A 25-45 will push the same weight bullet faster than a 6x45. The gains in a small capacity case like an x45 are pretty small, but you said you would need 15% more to equal it, and there is just no truth in that statement.

 

[Leon tP]

The OP wants fins, let him have fins.
...

Fins at an angle to add spin, that would be cool.

 

[Jim Watson]

Like an arrow.

 

[Varminterror]

Even in the x45 and smaller cases it is not true. A 223 will push the same weigh bullet faster than a 20 practical. A 6x45 will push the same weight bullet faster than a 223. A 25-45 will push the same weight bullet faster than a 6x45. The gains in a small capacity case like an x45 are pretty small, but you said you would need 15% more to equal it, and there is just no truth in that statement.

I load benchmark under 50’s in 6x45. Matching the same powder in the same barrel length with 223 with a 50grn bullet takes ~3 grains more powder. All the truth I need in my life.

 

[Varminterror]

Fins at an angle to add spin, that would be cool.

Like an arrow.

All this does is reduce ballistic coefficient by increasing drag. We spin arrows to increase drag and add steerage (move center of pressure rearward). Rifling spins bullets faster - orders of magnitude faster - than could remotely be influenced by fins on the bullet.

 

[someguy2800]

I load benchmark under 50’s in 6x45. Matching the same powder in the same barrel length with 223 with a 50grn bullet takes ~3 grains more powder. All the truth I need in my life.

You will need a faster powder in the 6x45 compared to the 223 to reach maximum velocity in both because of the expansion ratio. You know this.

 

[Varminterror]

You will need a faster powder in the 6x45 compared to the 223 to reach maximum velocity in both because of the expansion ratio. You know this.

Yup... I know this...

Which is why I pointed out the fact expansion ratio matters, debunking the claims previous which stated bore diameter was irrelevant. Thanks for backing me up.

 

[someguy2800]

Yup... I know this...

Which is why I pointed out the fact expansion ratio matters, debunking the claims previous which stated bore diameter was irrelevant. Thanks for backing me up.

Yes expansion ratio matters very much which is why using the same power when comparing 2 different bore sizes is a ridiculous comparison.

 

[Varminterror]

Yes expansion ratio matters very much which is why using the same power when comparing 2 different bore sizes is a ridiculous comparison.

Ok, have it your way... I put the same charge of Varget under a 50 grain bullet in 223 as I put of Benchmark (a faster powder) under a 50grn in 6-45, and I end up with 100fps faster in the same barrel length in the 223....

Does that satisfy your desire? Whether using the same powder and requiring more powder to attain the same speed, or using the same charge weight with a faster powder to attain a slower speed...

Irrefutably, if we can sustain the same pressure curve in a larger bore, we will have greater net force by increasing bore diameter. But the x45 case is small. If we can’t feed the bore to sustain the same pressure curve, then our net force behind the bullet can fall behind the smaller bore. Yes, we CAN and we do exceed smaller bores with larger ones, by the point in all of this has been that this observation isn’t absolute that increasing bore given no other change in potential energy input will produce greater KE out of the muzzle. We get more out of the larger bore. But we have to put more in to get it.

I can point to the same relationship in the 44mag case (although less fair, as necking to 357/44 does steal a lot of capacity). I can hit the same speed with a 180grn .357” bullet using 5-6grn less H110 as I can hit with a 180grn 44cal pill.

 

[someguy2800]

No because varget is going the wrong way in 6x45. To expand it to a larger scale of difference we would not use the same powder in 243 as in 338 federal and expect both to be optimal. Use the max charge of whatever powder nets the fastest velocity in both, not the same powder or powder charge in both. Same thing for 357-44 and 44 magnum, don't pick some arbitrary powder charge weight. Use the powder charge in both that nets maximum pressure.