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Peska · Member

I've got a couple of pump-ups and was just wondering something.
I've seen some good target guns that generate about 400 fps with
one pump. If that's the case, then why isn't it possible to make a
rifle rated at say, 750 fps, with just two pumps?
I guess there's a reason, but it seems to me if it's possible to get 400 fps
with one, why not 800 with two or three?
Cliff

Alstone · Moderator & Site Supporter

Because the pressure increases on a logarithmic scale, similar to (1+1/2+1/4+1/8+1/16 etc).

Al

Westonhill · Member

My guess is that even they somehow can make a pump that doubles the pressure on every stroke, the heat that it generates would be doubled on every stroke as well and hence may damage some parts in a gun. Isn't that the same reason that says to go slow when charging up PCPs?

thepaladin · Senior Member

Right and the power to pump would also go up geometricly. As noted, heat always goes up with pressure, just ask the PCP users about temps on their pumps and compressors. Power has to be built at given levels though you can do a lot with the release valves.

Some of the moded multi-pumps can be pumped as many as 50 times for their max power.

airbuddy3 · Member

Hi Cliff ,
Its been done ...Its called a spring gun !!
1 pump 900fps 8gr even 860fps in .22 14.3 ( some companies claim more ..but these are actual numbers )

it also has been done with Pneumatics , useiing a debounce device and prepumping the gun 5 pumps ...then adding 3 pumps for each shot and get 800fps 14.3gr ...do a search on the Yellow forum
Steve of NC did some work on this with James Perotti in the past year .

Regards ,
Frank

Alstone · Moderator & Site Supporter

thepaladin · Senior Member

Well. to a point. It's true that temp rise slows, but unless you're dealing with an inert gas (like nitrogen) there is some relation between pressure rise and temp. I was (until disabled) a refrigerstion tech for 25 years and one of the big killers of equipment (compressors etc.) was heat. a contominated system can't dump heat effecently and so on. so my only point was that there is a relation between temp and pressure. using a pcp you can actuall burn yourself baddly.

A springer uses a different system. It uses one self generated "puff" that drives the pellet out of the gun. Interestingly "to a point" a pnumatic gun like a pcp or a multi-pump gun can actually produce a little more power with a longer barrel (like I said, to a point there is a point of deminishing returns) where a springer gets it's power in one release of a piston so the barrel length dosen't effect power that much.

(good discusion).

I'm sort of addicted to power in springers to. I've been considering the new Mendoza magnum. It's supposed to be a powerful gun at a good price. the reviewers all say it's pretty loud though.

Alstone · Moderator & Site Supporter

thepaladin · Senior Member

You have to be careful of that in the US. While we can get most any power air gun legeally any kind of silencer is usually illegal. Odd laws. I worry a little about the noise as the reason I got into air guns heavely was that I can't get to a range or out to the woods so much now, but can have a fairly nice legal range in my back yard for air guns....unless I tick off the neighbors. So, while the Mendoza gets good reviews and I could use it for not only targets but small game etc. I have to be aware of the neighbors.

AirGunEric · Site Admin

Not illegal in most places in the US (California is one notable exception) to get a silencer- if you get a BATF permit and buy the silencer from a licensed dealer, etc. etc. Silencers, especially for airguns are basically just cost prohibitive (the permit is a bit over $200- and the permit is only good for the person to whom it was issued and for the specific silencer purchased under it- and a silencer that can be bought in the UK for $50 USD costs 10 times that in the U.S.).

The idea that silencers are "illegal" in the US is a common misnomer- they are restricted and owners do have a file on them with the BATF after that in respect to the permit- but not illegal.