Looking for a design for a large caliber air rifle

[seventh_shooter]

Any one got any ideas? Thanks, Steve

[DonT]

Please if you have any luck let me know.  I built a .22 PCP Air rifle and have considered building one in .45 Cal. but I am unable to get more than 600fps out of the .22 so I am not sure how I would get enough air to power a 45 Cal roundball.

I have tried to change the striker weight and changed springs trying to get more hang time on the valve, nothing.  I have tried charging the tank to different pressures (2,000psi to 3,000psi) and this does nothing.  Actually the speeds slow some till the pressure gets to about 2,000 and I think that is because the air pressure is prematurely closing the valve.

I have opened the air port the bolt, nothing, I have put a tube in the bolt that reduces the diameter of the final output behind the pellet hoping that would work, nothing.   So the testing goes on.

Like I said until I can get more speed out of the home built .22 pellet gun I am not wasting the time on building a big bore.  Now I have considerd buying one like the dragonslayer to study..  Have to wait and see....

Later..
DonT

[lamerabbit]

With a pcp you need a long barrel, or a whole lot of air!  That is to say the bigger the hole going behind the pellet the more air will go to push it out the barrel.  I have bumped up a coulpe of pre-charges this way, just porting the transfer port and the barrel.  I have also done some porting of the firing valves to gain more fps.  A tightly choked barrel will also slow down pellets, sometimes the difference not a lot, but it is there. 

They managed to build air rifles that would kill a man or a dear at over 200 yards, almost 400 years ago, so I see no reason why it can't be done now, in fact there a several guys that do build them!  That's a bit more power than I want though.

Jim

[DonT]

Jim,

I have fooled with the ports some.  may have to go bigger.  Increasing the size hasn't shown much change in pellet speed.  I am using plenty of air from a tank that holds 3,000 psi.  Just gonna have to play some more.  The barrel on the one I built is a lothar Walther choked barrel so less resistance to start and it chokes down to proper size  the last 6" or so...

DonT

[S.S.]

I too have been unsuccessful at this with larger bores.
Good luck with this, for the moment, I have given up.

[BUTCHER45]

     What are you guys wanting out of the boolit?  Target or hunting?

     It is important to make use of a chrony, to monitor velocity, and experiment with various fill pressures.

     The EPP/UG is very accurate in SamYang 909 guns.  This 240grain WFN (BlackHogDown sells them) hits incredibly hard, and would be my recommendation for hunting bigger stuff.  Designed specifically for Sam Yang 909 barrels.



     Typical group off the steady stix at 50 yards.  Small squares on target are .5 inch

[jlwilliams]

Tag

[lamerabbit]

Hi DonT:

I know it is kind of tricky, but you have to enlarge all the holes.....   The one inside the valve, where the air comes in, where the air goes out, and the transfer port, and the transfer port in/on the barrel.  If you only do one oods are you velocity will stay the same or even go down.  You can get high velocity with much less pressure than 3000 psi.   The daystates that I have messed with, seem to shoot faster at lower velocities.   I actaully get the highest velocity at 2000 psi, or ther abouts.  There are many air rifles that shoot quite fast at 1600 psi, like the USFT, but it is a 177 caliber gun....

Jim