SpudFiles

jackssmirkingrevenge wrote:That must make quite a crack! Interesting rifle build, I'm guessing it's a home made hammer valve?

Yes, very loud even with a silencer.
That's right, just basic hammer valve system.
Get about 40 shots per fill, don't think I'll continue with Helium though.
The cost along with how loud it is doesn't make it worth the small increase in velocity.

Eljefe13 wrote:

jackssmirkingrevenge wrote:That must make quite a crack! Interesting rifle build, I'm guessing it's a home made hammer valve?

Yes, very loud even with a silencer.
That's right, just basic hammer valve system.
Get about 40 shots per fill, don't think I'll continue with Helium though.
The cost along with how loud it is doesn't make it worth the small increase in velocity.

That means you could go longer barrel, you have more power in there because its so loud...or smaller chamber?

Eljefe13 wrote:At 2000 psi I'm getting 1150 fps.
Might try 2500 and then 3000 today and see how it goes.

OK, yeah, you're Mach1+ for air. That means that the ability of air to literally move it's own self is a major hurdle. Helium should really help things along...And apparently it has!

D_Hall wrote:

Eljefe13 wrote:At 2000 psi I'm getting 1150 fps.
Might try 2500 and then 3000 today and see how it goes.

OK, yeah, you're Mach1+ for air. That means that the ability of air to literally move it's own self is a major hurdle. Helium should really help things along...And apparently it has!

Does that mean it won't get much quicker with air?

First Rule Gentlemen.

Yes, very loud even with a silencer.
That's right, just basic hammer valve system.
Get about 40 shots per fill, don't think I'll continue with Helium though.
The cost along with how loud it is doesn't make it worth the small increase in velocity.

That's quite a respectable shot count, and I agree that helium is fun for pushing the boundaries but for practical purposes, compressed air or nitrogen are much more convenient. The transonic region also tends to be an unstable one for airgun projectiles, you're better off with a heavier projectile in the 950 fps range.

Thread cleaned! Behave yourselves... :bigsmurf:

I missed it :blackeye:

jrrdw wrote:Thread cleaned! Behave yourselves... :bigsmurf:

Thank you i was wondering when that was going to be deleted.

farcticox1 wrote:I missed it :blackeye:

Didn't miss much, but being made to look like a pedophile does not gel well with me.

Eljefe13 wrote:Does that mean it won't get much quicker with air?

Pretty much. Once you're past Mach1 in the working fluid it gets much more difficult for every bit of extra speed. REsult is the gun gets a lot louder, uses a lot more air, and only goes a tiny bit faster.

Options are to use a lighter gas (like helium), to heat the gas up (like firearms), or both (2-stage light gas guns).

jackssmirkingrevenge wrote:First Rule Gentlemen.

Yes, very loud even with a silencer.
That's right, just basic hammer valve system.
Get about 40 shots per fill, don't think I'll continue with Helium though.
The cost along with how loud it is doesn't make it worth the small increase in velocity.

That's quite a respectable shot count, and I agree that helium is fun for pushing the boundaries but for practical purposes, compressed air or nitrogen are much more convenient. The transonic region also tends to be an unstable one for airgun projectiles, you're better off with a heavier projectile in the 950 fps range.

I wondered why most of the latest air rifles only have a 900-1000 fps limit.
A previous build that I still have but is dismantled now was made for 8mm steel ball bearings but I wasn't sure how accurate it was going to be past 25-30 metres being a smooth bore system.
In your experience, how do round projectiles out of smooth bore perform in trajectory over 100 or so metres?
I would imagine the higher the velocity the more stable and accurate the projectile would travel, or is that not the case?
Thanks for your advice.

D_Hall wrote:

Eljefe13 wrote:Does that mean it won't get much quicker with air?

Pretty much. Once you're past Mach1 in the working fluid it gets much more difficult for every bit of extra speed. REsult is the gun gets a lot louder, uses a lot more air, and only goes a tiny bit faster.

Options are to use a lighter gas (like helium), to heat the gas up (like firearms), or both (2-stage light gas guns).

Thanks for your advice, greatly appreciated.

A previous build that I still have but is dismantled now was made for 8mm steel ball bearings but I wasn't sure how accurate it was going to be past 25-30 metres being a smooth bore system.

While they intuitively sound good, steel balls are quite poor projectiles.

First of all, a sphere has quite a high drag coefficient compared to a conventional "bullet" shape:



This means that it's going to lose velocity at a higher rate, and drop is going to be significant over range meaning that correct range estimation is absolutely crucial to accuracy at distance. The fact that steel also has a relatively low density compared to conventional bullet materials such as lead means that for a given diameter it will lack weight and therefore less momentum to counter air resistance - think of it as the comparison between throwing a golf ball and a ping pong ball, both are about the same size and shape but even if thrown at a lower velocity, the golf ball is going to go much further because it slows down at lower rate.

In your experience, how do round projectiles out of smooth bore perform in trajectory over 100 or so metres?

Not terribly well, especially if there is a significant discrepancy between the the diameter of the barrel and the projectile.

If you can close that gap, and accuracy means reliably hitting a 3 x 3 foot target than a 1 inch circle, then it might be acceptable.

This does not mean that you necessarily need a rifled barrel to hit a target at 100 meters - one can for example have good results with shotgun slugs in a smoothbore but if you're relying on drag for stability, as velocity starts to drop then group size increases.

You've made a very respectable launcher with higher performance than most projects on this forum, perhaps if accuracy is your goal then you should consider making your own rifled barrel (assuming purchasing one is not an option) and casting your own lead bullets?

jackssmirkingrevenge wrote:

A previous build that I still have but is dismantled now was made for 8mm steel ball bearings but I wasn't sure how accurate it was going to be past 25-30 metres being a smooth bore system.

While they intuitively sound good, steel balls are quite poor projectiles.

First of all, a sphere has quite a high drag coefficient compared to a conventional "bullet" shape:



This means that it's going to lose velocity at a higher rate, and drop is going to be significant over range meaning that correct range estimation is absolutely crucial to accuracy at distance. The fact that steel also has a relatively low density compared to conventional bullet materials such as lead means that for a given diameter it will lack weight and therefore less momentum to counter air resistance - think of it as the comparison between throwing a golf ball and a ping pong ball, both are about the same size and shape but even if thrown at a lower velocity, the golf ball is going to go much further because it slows down at lower rate.

In your experience, how do round projectiles out of smooth bore perform in trajectory over 100 or so metres?

Not terribly well, especially if there is a significant discrepancy between the the diameter of the barrel and the projectile.

If you can close that gap, and accuracy means reliably hitting a 3 x 3 foot target than a 1 inch circle, then it might be acceptable.

This does not mean that you necessarily need a rifled barrel to hit a target at 100 meters - one can for example have good results with shotgun slugs in a smoothbore but if you're relying on drag for stability, as velocity starts to drop then group size increases.

You've made a very respectable launcher with higher performance than most projects on this forum, perhaps if accuracy is your goal then you should consider making your own rifled barrel (assuming purchasing one is not an option) and casting your own lead bullets?

Thanks for the detailed response, answered a lot of questions and confirmed some of my opinions.

I'm actually using a .22 calibre rifled air rifle barrel with .22 pellets, it's the only part of the build apart from the scope that's not homemade.

Cheers for the advice.

I'm actually using a .22 calibre rifled air rifle barrel with .22 pellets, it's the only part of the build apart from the scope that's not homemade.

Consider some heavyweight pellets (25 grains or more), here are some available types: https://www.pyramydair.com/a/Ammo/Airgu ... /pw_grain5

Pushing these to high subsonic velocities makes 100 yard shots more than possible.

I'm not a remarkable marksman yet I've personally shot a 2 inch group at 120 yards with 16 grain pellets at 900 fps from a FX Monsoon, as long as you have your distances well measured and wind properly dialed in it's not a huge challenge shooting from rest.