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Henry_Coughlan · New Member

I work for a personal saftey equipment manufacture and the company have recently bought a CO2 .22 rifle to bolt to a trade show demonstration rig for the testing of goggle.

I need to know is there any suitable way to slow the speed of the pellet before or as it leaves the gun. I have no idea if this is possible to do or dangerous?!

The gun is an SMK XS78 http://sportsmk.co.uk/item/362/

Someone did suggest using .177 pellets - would this lead to jamming?

Alstone · Moderator & Site Supporter

A quick answer Henry is yes, all you need to do is fit a weaker hammer spring.

This is quite easy to do provide you have a little machinical skill, below is a photo of a QB78 insides the spring in the photo is the one that want's changing for a weaker one.

BTW welcome to AirGunHome

http://airgunhome.com/agforum/viewtopic.php?t=481&highlight=polish

Al

PS: .177 pellets would'nt shoot very well out of a .22 barrel.

If the whole idea is so the pellet does not penatrate the goggles, then remove the O-ring on the end of the bolt, this will reduce the output considerably. Mr. Green

Henry_Coughlan · New Member

Thanks alot, thats really useful

donec · Senior Member

I'm sorry but why would you want to reduce the speed of the pellet? I mean if you are saying the goggle will withstand the force of the pellet then reducing the speed would well.... How about placing the whole exhibit with-in a Plexiglas safety cage and let the pellet just bounce around in side safely after hitting and not damaging the goggle?

fritz · Silver Status Member

Eric said the technical stuff spot on, but I have problems with the ethics behind this experiment.

oddtodd · Silver Status Member

I have an issue with this too. It sounds like they first bought the rifle and it busted the safety glasses so they are trying to make sure the goggle at least looks like it passed the test. To me this raises the BS flag bigtime.

Verado · Member

Maybe use some PBA ammo, place the gun in a cold area to have minimal expansion of CO2 or 1 12g cart instead of 2, weaker hammer spring. Might want to advise your customer's that the gun has been de-tuned and the impact energy is approx. 8 FPE.

kanyon · Silver Status Member

Sport thats just BS...These are saftey goggles....
If they are not up to it DON"T sell them... Rolling Eyes

I use saftey goggles every day to save my eye site
lathe/mill etc...
And my 8yo son uses saftey goggles while shooting...

better end there ..before I'm band...

Pete

Dukemeister · Member

I hear and agree with those of you saying watch the ethics. I bust stuff for a living so I will offer some technical (not ethical) advice. I looked up the ASTM standard for testing protective eye wear, and found that it has to pass an impact test with a 1/4" steel ball fired at 150 fps. This is about 2.8 FPE. A stock .22 cal QB78 running at 450 fps with a 14 gr pellet would give about 6.5 FPE, more than double what the standard requires. If he slows the QB78 down to about 300 fps he will get the correct impact energy. As long as there is no claim that the goggles could protect you from "shooting your eye out" with an air rifle then, ethically this may be OK. Of course, he SHOULD just get a Red Ryder BB and shoot the goggles with that. It should pass the test, they only put out about 1.5 FPE. A tuned for Canada .177 rifle with a 5.1 gr BB pellet at about 495 fps gives an almost perfect match to the ASTM impact energy of 2.8 FPE. A Canadian Tire Beeman 1040 should do the trick.