Tuning Receiver deburring, O ring change, crown polishing, and barrel lap

[Toolmaker]

My o rings were damaged from last time I took the barrel out. So I had to debur the grub screw holes and transfer port. The grub screw holes I had to do by hand with cratex, and took about a half hour straight polishing. The rest went smooth thankfully, and when I reseated the barrel, the o rings felt great going in, no snags or rips I could feel and now the gun is back to firing pencil eraser size groups. The target in the pic is 15 yards, 7 pellets jsb 18.13

In the picture showing the slug on the jag there is a right angle metal scribe. It's made to scribe layout lines in tough to reach spots. Now I'm ver new to airguns, but I'm not new to my trade, an old timer taught me this is the best tool possible for removing O rings. It allows you to stab into the old o ring and lift it out so it can be hooked with another tool. It's a bad idea to try and get around the o ring because it's easy to damage the walls of the o ring groove. Just a little tip an old man taught me, I hope it helps. 

 

[Parrotculler]

You got some serious lookin' machinery there ...

What make is the gun? 

 

[Parrotculler]

You got some serious lookin' machinery there ...

What make is the gun? 

 

[nervoustrig]

Yes sir, way to go!

I like seeing how others approach this stuff. I spend a lot of my evenings in the shop doing similar things to my rifles, and the results are very rewarding.

Did you get a pic of the crown work?

 

[Toolmaker]

It's a Benjamin Akela, and I'm very happy with it. For the price, I can understand and find it justifiable for me to debur myself. This target shows before and after groups. Pls keep in mind this gun shot very ery well right out of the box, but I removed the barrel a while back and damaged the o rings. BTW, this is where I work, I don't own the machinery, but I have a key to the shop and 24/7 access thankfully. I do my personal work off the clock ofcourse but I'm allowed to shoot on the clock as long as I have a machine cutting. For the fella asking about the crown work pics, I did not machine the crown, I simply jogged out material with a stone, then cratex and polishing compound. I used common sense and ran the lathe in both directions, clockwise and counter, so that the rifling lands got polished evenly. If you polish interrupted cuts like rifling in one direction it tends to remove more material from one side or the other. 

 

[Toolmaker]

Also, the gun seems to be using much less air now, is that normal with fresh o rings? Pardon my ignorance pls, like I said I'm new to airguns

 

[Parrotculler]

Great results there!

Your o ring improvement avoids air leaks, contributing to less noice and a little more power when shooting. You have achieved a more refined gun. But I would not expect an improved o-rings seal around the barrel to reduce air usage itself meaningfully. That is because PCP air usage depends on other factors:

- hammer weight and hammer spring tension -- the more hammer dwell, the more air usage (other things being equal, see below). Often a heavy hammer with a long spring even bounces on the valve stem, and opens the valve more than once = hammer bounce and air wastage 

- valve spring tension: a stronger valve spring closes the valve faster, so less air can escape

- air pressure from the cylinder on the valve. Lower pressure, e.g. because of a regulator, causes the valve to close more slowly. This is why regulated guns often need lower hammer spring tension, and sometimes more valve spring preload as well.

- valve inlet and outlet port. Unregulated Krals, like the Akela, often have smaller-diameter ports, and are air efficient. Your gun is based on a Kral platform that gives very good unregulated performance.

As you can see from all this, air efficiency is the result of a balancing act between several factors in front of, and behind, the valve. That same balance equally influences accuracy. The new Krals are typically very well balanced out of the box.

Many would therefore argue against tinkering too much with those parameters. Unless you have an appetite for time consuming experimentation, mixed with a good deal of frustration ... In that case you could do worse than read some of the tuning topics by Motorhead and Vetmx. Other luminaries include THammer, by most accounts the Kral grandmaster, and TheBanker4. Bob Sterne has also published great tuning insights in Hardairmagazine.

Said all this, there is no doubt that an O-ring improvement like you did, a good barrel cleaning, and perhaps a mild carbon powder lube in the cocking action, makes for smoother shootin' ... Enjoy your Akela. The walnut really shines with some fine grain steel wool polishing (wet, with walnut oil) followed by several thin coats of linseed oil! It's a labor of love -- let the linseed dry in between coats, and top it off with some ballistol at the end. If you like wood you're gonna have a jewel on your hands.

 

[Toolmaker]

Thank you very much for the info! I'm very new to this and don't plan on messing with the valves or hammer tension. I felt it was very important to atleast get the holes deburred on the inside of the receiver. I figured wouldn't hurt to polish up the barrel some, and I'm pretty damn sure what I did helped. It was shooting great right out of the box but look at this new target, it didn't shoot that well until the polish. One single flyer of the bunch. Also, I'm not even using a vise, I'm using the bipod, but rest is me shaking haha

 

[Parrotculler]

Thank you very much for the info! I'm very new to this and don't plan on messing with the valves or hammer tension. I felt it was very important to atleast get the holes deburred on the inside of the receiver. I figured wouldn't hurt to polish up the barrel some, and I'm pretty damn sure what I did helped. It was shooting great right out of the box but look at this new target, it didn't shoot that well until the polish. One single flyer of the bunch. Also, I'm not even using a vise, I'm using the bipod, but rest is me shaking haha