Author Topic: Custom load help  (Read 173 times)

qiip

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Custom load help
« on: December 14, 2018, 11:25:40 AM »
How fast would a 55 grain .22 pellet go when shot with 3000 PSI of pressure? 24 inch barrel length. Would it be feasible? Would the pellet be stable?


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ShakySarge

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Re: Custom load help
« Reply #1 on: December 14, 2018, 12:29:31 PM »
That depends entirely on the platform.
  • Clarksville, Tennessee
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qiip

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Re: Custom load help
« Reply #2 on: December 14, 2018, 12:49:32 PM »
So maybe elaborate? That wasn't helpful.
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ShakySarge

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Re: Custom load help
« Reply #3 on: December 14, 2018, 01:26:51 PM »
What I mean is that we need to know what gun you plan on souping up. All you gave us was fill pressure and the size bullet you want to shoot and the barrel length. Given only those three factors, we can't tell you how fast it would shoot. Without the platform, we can't give you a definitive answer. Suppose you had a marauder with a beefed up valve and transfer sleeve. Let's say that it shoots 18.13's at 1,000 FPS. I would assume that the 55GR would travel quite a bit slower. Without knowing what it shoots now, I don't think anyone could tell you an exact number.

Basically, your reply was exactly what I was saying initially.
  • Clarksville, Tennessee
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Alan

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Re: Custom load help
« Reply #4 on: December 14, 2018, 02:12:03 PM »
I agree.

A fifty-five grain, .22 caliber pellet would be VERY long (≈one inch). Most airguns, designed to fire PELLETS, won't handle a projectile that long. In fact, some won't fire the JSB heavies (≈34 grains) due to their length. And, what you would need, is a true .22 caliber airgun (.224 rather than .220), with a much faster twist. But to directly answer your question, I'll stab at this, based on nothing other than the information you stated. I guess about 450 FPS, and even that might be a stretch.

And just for the record... Airguns designed to fire heavy projectiles, are often referred to as slug guns, which refers to the fact, they don't shoot pellets. The moment right now, it to larger calibers, and heavy bullets, much heavier than pellets have every been.

The question remains, what do you plan on using such an airgun for, and perhaps Matt or I can get a bit closer.
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Alan

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qiip

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Re: Custom load help
« Reply #5 on: December 14, 2018, 02:21:59 PM »
Right. Okay, so bear with me. Say I take an Umarex Hammer .50, and do some kind of trick switch and stick on a .22 barrel. Odds of that working notwithstanding, how fast would it go? If it's totally implausible, then at least what formulas would I need to do that kind of calculation?
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Re: Custom load help
« Reply #6 on: December 14, 2018, 02:28:14 PM »
I would imagine that necking down a .50 air gun to shoot a .22 slug could potentially produce some serious speeds. On the other end of the spectrum, it could cause some serious issues with the valve and such on the air gun due to over pressure but I could be wrong. If it were feasible and safe to do so I would expect that there is potential to push a .22 55gr at speeds of 1500FPS or more, theoretically. Perhaps Bob will chime in and provide some known equations to provide a more accurate number. 
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Re: Custom load help
« Reply #7 on: December 14, 2018, 04:10:17 PM »
You bring up an interesting bit of technology.

The only way to put air into an airgun breach, is through a hole. This "hole" os typically on the underside of the barrel. This limits the size of the hole to about 80% of the bore size. In some special cases, it might be possible to use the whole bore size, but doing so is impractical.

Given any size bore (caliber), the transfer port hole size, the valve, valve dwell, and about a dozen other design parameters, there is a practical limit to velocity. You stated 3,000 PSI, which limits the amount of air which "could" be utilized to propel the projectile. Well, only so much cab be shoved into the breach at 3,000 psi. Now if we were to use helium, at say 4,500 psi, you might get over the speed of sound. So what? The main advantage of an airgun, is its quiet factor. But once you get over the speed of sound, airguns make as much noise as firearms.

Again. What are you trying to accomplish?
  • Roswell, New Mexico
Alan

I have an Omega compressor. If you're a fellow Guild member, and you pass through Roswell, NM, I'll fill your portable tank as a courtesy.

qiip

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Re: Custom load help
« Reply #8 on: December 14, 2018, 05:08:56 PM »
In my state(Illinois), an airgun over .18 or 700 FPS is considered a firearm. So, I was thinking of engineering an airgun in .177 or even .17 hornet, that goes fast enough to pack enough wallop, regardless of sound, to be feasible to hunt large game with.  All this, while not being a firearm. I decided to start with .22 because I didn't know whether or not it would even be plausible to get an airgun pellet moving fast enough(around 2800 FPS). Sounds stupid on paper, but it made sense in my head. So ignoring the previous request, Is it plausible(or even possible) to move a 21 grain .177 projectile down a 24 inch barrel at 4650 FPS, and how much pressure would I need in a tank.
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rsterne

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Re: Custom load help
« Reply #9 on: December 14, 2018, 06:18:31 PM »
To your last question, NO....

You can get a rough estimate of what might be possible, if you do everything perfectly, by using the following formula to determine what I call your "lofty goal".... This formula is intended for a bullet at 950 fps, where the weight is half the FPE....

FPE (max.) = barrel volume (cu.in) x pressure (psi) / 24

Your barrel volume is (0.177 x 0.177 x PI/4) x 24 = 0.0246 x 24 = 0.59 CI....

At a pressure of 3000 psi, that works out to a maximum FPE of (0.59 x 3000 / 24) = 74 FPE.... using a 37 gr. projectile....
At 4500 psi (about the maximum practical currently) it works out to 110 FPE with a 55 gr. projectile....
Lighter projectiles, travelling faster, are harder to accelerate, so the FPE you can achieve would be less than the above....

A 21 gr. projectile at 4650 fps is over 1000 FPE, so that is completely out of the question....

Quote
In my state(Illinois), an airgun over .18 or 700 FPS is considered a firearm.

It would seem that anything over 700 fps is illegal anyways, right?....

Bob
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