Hello,

I am looking at my next project. I had wanted to go bigbore but lacking the funds to do so. Since I still have a new blank 22 Cal German made airgun barrel I will go that route for now.

I am wondering about the feasibility of making a rifle that can launch a heavy .22 pellet, like 45 to 50 grains, which would be around 7/16 to 1/2" plus in length?

Seeing Tofazfu's results with the .25 CAL , 102 grain Spitzer's wondering if that would work in .22 CAL?

Thinking further, I think I can use a test bed I made a few years ago, as the barrel is 16mm and the hole is 0.625".

Here are some CAD pics of the proposed rifle I hope to build. It will be a side lever for loading and let hand cocking handle (So Far)

Your feedback is greatly appreciated.

Pedro

Hello Pedro,

Looks nice. Hey - I have to use an old school pencil! haha.

Your bullet design will be key. The rule of thumb is you'd need a much faster twist barrel for the long slug - but I've had mixed results. I've had some long bullets shoot from moderate speed guns, with medium twist barrels. Had some long bullets and very fast twists that just don't want to group.

You know that you can get your push and spin control just from a drive band or two - you probably wouldn't want to try to engrave a 1/2" long straight side bullet.

I'm not seeing your lever geometry correctly. I think I see your handle portion forward. To cock and open the bolt seems like opposite actions. Where are your pivots? I'm seeing it backwards and would like to follow your drawing better.

Hope it works well for you. I'm jealous - with my tools locked up 1,100 miles away - boo hoo ...

Gary

Hi Gary,

Thanks, when you mentioned the longer pellet, I remembered that the twist has to be faster. I will be using driving bands and experiment with lengths. If nothing else use heavy commercial pellets

Below are some snap shots of the CAD for the lever, hope it makes more sense. I haven't completed the design as I want to change a few things to make the barrel rigid as possible to the breech, thread and set screws. Still have to design the internals. Haven't decided on trigger/sear combo. But will play with the design for awhile no rush at the moment.

Using Solidworks. Self taught basically, I like drawing projects as I learn for work related items. But it can be deceiving. The CAD model can look really good, but proportions can be off as you do not physically have a model in front of you. Hence the Pellet probe lever looks rather large, but I can mill it down some later if needed or make a new one.

Programming a die, 3D milling, for my dad at his shop right now and after will machine the old platform rifle I have to accept the barrel and hopefully try it next week.

Thanks again for your help.

Nice rendering work there, hope the project works out well.

Hi Pedro, your design looks great. Garry is right about the twist rate of the barrel. You could either use a .22 rim fire barrel which generally have a 16'' pitch or there abouts, they are usually available quite cheaply. Or use shorter slugs in your airgun barrel. Generally speeking the rim fire barrel is slightly larger in both bore and in the groves than an airgun .22 barrel so you will need to choose/size slugs/bullets accordingly. Danny.

Hi Danny,

Thanks for the comment. I guess many of us do not realize that rimfire barrels would work? I will check the twist on the barrel in a few days or week. It is a Lothar Walther airgun barrel but I cannot remember the twist rate. Checked their website but it doesn't list the twist rate.

Thanks again,

Pedro

I would bet it's 1/16"

Only thing with rim fire barrels is their very wide lands. That is a lot of real estate to engrave with the air blast. Now, back pressure can be a good thing to build breech pressure, but you have to have a slug with short rings and few, or you are going to have a fight to get it out of the breech. Just plan for it if you go that route.

Gary

Hi Pedro,
That looks good. I now note the articulated lever. Are you counting on it to toggle overcenter - to lock your breech?
And, or course ... you had already shown that you have a seperate side cocking lever.
I might suggest that you extend your bulk material forward over your pressure tube - in order to give yourself more material to mount your barrel into.

Gary

Gary,

The lever does travel over center but I am thinking of making a catch for safety. Maybe a thumb lock released with thumb pressure. To add barrel support I can increase the breech length accordingly. I did some modifications to the test rifle and hope to complete this coming week. After I get a chance to test some pellets I will work on the final design of the air rifle.

Looking forward to seeing you back in the shop Gary!

Pedro

Hi again Pedro, I ran your slug weight/length through the twist calculator at 1000 fps and come up with 11''-12'' pitch. One of the rim fire barrels I have used was about 12'' pitch , I think it may have been an Anshaults. I cast 27gn hollow pointers for it which grouped real nice out to 50 yrds and 1050 fps but I cant say I tried it out any further than that. All of the rim fire barrels I've used have had micro lands, that said Gary is right about building the gun a bit stronger to withstand the extra residual pressure etc. If your LW barrel is designed for standard air rifle slugs it will be no good for the longer slugs as they will be under stabilized and will eventually tumble. Also looking at your design it may be advantageous to keep a bit more bulk material in the receiver around the loading port if you are going to float the barrel as the upward pressure of the transfer port will tend to flex the receiver therein flicking the barrel upward effecting the shots. Danny

tha design is like Airarms S400 or s500. its very nice. if you make long slug you must make power rifle about 100 fpe and your tube must be aver the 400c to move and accuary shots. I will wait finish your project and see you slug and rifle performans... good luck

Thanks,

I didn't model the rifle after any commercial but took ideas from many that I have seen online in the last few years.


Pedro