For those who may not know, Vx720/T is the formula. It sure looks like I missed one on my phone calculator, too.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.
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.
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.
Volume, piston area, bore diameter, has nothing to do with the calculation.
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....
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.
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.
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.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.
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.
Fins at an angle to add spin, that would be cool.The OP wants fins, let him have fins.
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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.
Fins at an angle to add spin, that would be cool.
Like an arrow.
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.
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.