What is best way to chamfer interior lip on Benjamin Akela?

[pipcount]

My Akela barrel has a step on barrel which registers against a shelf on the block during insertion.  Issue I have is that the lip of this shelf it pretty sharp and cuts the barrel o-rings up terribly.  Upon my first disassembly I found both o-rings on barrel had multiple cut sections.

First attempt to remove:  using my wood lathe I made a hardwood dowel with a 45 degree end, simply chucked up in drill and slathered on polishing compound, went to town.  Worked fairly well, but until I get new o rings I just re-inserted and prayed.  So no check yet if this really solved the problem.  Once I get some o rings spares will test, see if it works or not.  If not, looking for ideas.

Thoughts: 
1. - Try again if not sufficient.
2. Wrap up a reamer in paper until it is a VERY tight fit to the outer diameter of the barrel hole, insert lightly to take off a few thou around the lip.  Concern:  Chatter.  Polish again when done....
3. Build custom tool from drill rod that is tight fit to large bore, with hand filed cutters on a chamfer at  bottom.  Sure would work, but going to consume an afternoon.  Might still face some chatter.  Polish again to reduce.
4. Find appropriate sized round ball grinder bit, take off material with diamond dresser if needed, wrap middle in paper to protect large bore.  Not too bad for time I expect.
5.  Just use cratex rubber grinding bits and some patience...

Any better tips? 

[pipcount]

Could use your input.. surely someone on forum has done similar and has experience at best/simplest approach.

[pipcount]

adding an idea to list.. simplest so far I have:  turn drill rod to large bore size, chamfer end at 45 degree, simply place to shelf and tap a few times to deform aluminum block/remove sharp edge on register face.  If it changes the register face a few thou it wont matter to shooting, and if it puts lip in small bore it should be very small and easy to sand out.  Simple and quick.

[sb327]

Maybe an image of the offending area or at a minimum a sketch to better describe the situation. Several here with skills to do the job but a limited number who have that exact gun.

I’ve read the description of the shelf and THINK I am envisioning it correctly but without seeing it I’m not sure.

Good luck,
Dave

[eeler1]

I'm with Dave on a picture being helpful.  You can get a commercial chamfer tool like this;

https://www.amazon.com/dp/B0C4B7R4M5/ref=redir_mobile_desktop?_encoding=UTF8&aaxitk=b56f1043db63e2775fac1bf2ee0c2a5d&content-id=amzn1.sym.cd95889f-432f-43a7-8ec8-833616493f4a%3Aamzn1.sym.cd95889f-432f-43a7-8ec8-833616493f4a&hsa_cr_id=0&pd_rd_plhdr=t&pd_rd_r=58dd4e01-4b12-43e2-b695-c67adcfc4676&pd_rd_w=4sCjl&pd_rd_wg=B5CJZ&qid=1693589822&ref_=sbx_be_s_sparkle_mcd_asin_2_title&sr=1-3-9e67e56a-6f64-441f-a281-df67fc737124

Or this;

https://www.amazon.com/dp/B0BP1KM4GC/ref=redir_mobile_desktop?_encoding=UTF8&aaxitk=b56f1043db63e2775fac1bf2ee0c2a5d&content-id=amzn1.sym.cd95889f-432f-43a7-8ec8-833616493f4a%3Aamzn1.sym.cd95889f-432f-43a7-8ec8-833616493f4a&hsa_cr_id=0&pd_rd_plhdr=t&pd_rd_r=58dd4e01-4b12-43e2-b695-c67adcfc4676&pd_rd_w=4sCjl&pd_rd_wg=B5CJZ&qid=1693589822&ref_=sbx_be_s_sparkle_mcd_asin_0_title&sr=1-1-9e67e56a-6f64-441f-a281-df67fc737124&th=1

There are plenty of other similar products, countersinks, etc.  that would work fine. 

[pipcount]

new guys are not allowed to post images or even links for a while, so I cannot post image or link.. very frustrating, thank you guys for your patience.  I regret not being great at explaining this, let me try again:

It may be easier to think of the barrel first:  the barrel fits into a stepped hole in the block in which it fits.  The barrel itself is straight up to about the last 1-2" which are turned down about 50-75 thou.  This turned down section of the barrel has two o rings grooves to set to seal the air coming up from reservoir transfer port.  Key idea:  Barrel is turned down a bit at the end, with a flat where it steps down. 

The block then has a hole for the barrel that has a large bore that reduces to a smaller bore matching the barrel.  The barrel registers against this flat on the small bore.  The flat interior register face has the sharp lip which I am working to either chamfer or simply smooth off enough to not cut the o-rings.

Hard Air magazine has a post called "Generation Two Diana Stormrider Parts Diagram"  There is an excellent close up pic of a similarly turned down barrel with two o rings cut into the smaller diameter at the end of barrel.  Once you see the barrel I think it should be simple to imagine the issue inside breech block. 

But.. I cannot post either links or pics for another ~25 posts, so I cannot link to pic or add my own pics. 

[KWK]

Just post little comments on various posts on the forum. It won't make any difference to the thread. Go to something like " what did you shoot today" "What did you buy today" or something. I's as much (or more) comments as anything.
Remember, Some responders have something to say. Others just want to say something.     It's a forum.
Hope to see photos soon.

[sb327]

Like this?

[pipcount]

exactly!

[JPSAXNC]

Get a piece of aluminum or brass hobby tubing, long enough to reach the hole and a ball bering that's a little bigger than the hole. Epoxy the ball bering to the hobby tubing. As the tube is hollow the bering will be centered. Put some compound on the bering.

[sb327]

It would be pretty easy to chuck up a dowel rod (hardwood) in a drill. Spin it while using a file to create a taper that fits. Slice the tapered end with a thin saw (hacksaw works). Insert some sandpaper (for metal) into the slit, wrap it, oil the paper up good and go to work.

The ball idea to lap will work but the material of the ball needs to be softer than the metal you want to cut. When lapping, the softer material becomes the lap (holds the abrasive) and the harder material gets cut.

Good luck,
Dave

[pipcount]

Thanks Dave and JP.  If you check my original post you will see I essentially have already lapped with hardwood which is similar to both suggestions.  I cannot get my fat fingers inside to feel the lip, but my wife says it is no longer sharp.

Guess I will just put back together and see if I cut up my o-rings or not.

[pipcount]

And thanks to guys that said... just post stuff.  I do appreciate it.  I am a pretty heavy contributor on TradTalk archery forum, decades there, lots of folks know me.

I doubt I will get to same recognition here.  But I might end up contributing a bit in the machinist forum area.  Likely to begin with "well, dont do this" type posts as I learn by trial and error.

[sb327]

Is the transfer port smooth/burr free as well? Could be another offending spot.

Keep posting, even questions are good contributions.

Dave

[pipcount]

Dave - I smoothed transfer port on inside of barrel with needle files and felt/polish on foredom rotary handle, lightly touched up the lead with the felt and polish but tried to stay away from it for now.

On outside of barrel i more or less chamfered the port and smoothed it- did not open up any, just tried to set up so if not perfectly aligned that the air would have a smoother transfer into barrel.

On barrel crown I centered, then used small grinder to put a very clean and smooth new crown on rifle.  The original crown looked as though it were done by hand by someone suffering from delirium tremors.

On working bore of rifle- cleaned, polished, worked back and forth a lot at choke until it felt a bit easier.

Working on airguns is pretty straight forward so far.  Now I have to see if it shoots!  Going out to friends ranch on weekend, will let folks know. 

At this rate I may be able to post images and video in a few weeks.

[pipcount]

Took out to a friends ranch this weekend and shot the Akela with Crossman Premier 10.5gr .177 domed pellets (and maybe RWS 8.3gr domed).  After sighting in, and having some rough fun, I held 3x 3/8" and 2x 1/2" groups of 5 shots at 25 yards, with only one for sure flyer, perhaps two in ~40 pellets. 

Unfortunately I ran short of pellets.  I dropped my 3 mags (one filled, one mostly filled, one half filled) in my archery range bag, but forgot to add the pellet tins.  So after sighting in with ~10 shots for the new scope, playing around a bit with the gun to see how it worked, I ran out of pellets and was unable to try greater distances, different pellets, or weights.  I suspect the mags were 2xpremier, and perhaps 1x RWS 8.3gr domed... but as I was simply doing rough sighting in at time, planned to have fun until empty and refill to see if any significant differences occurred.

Net positive/things learned/things I will call good enough:
1. Work done unlikely to have caused any issues in rifle.  The gun likely shoots better than I can hold at this stage with the rough gear I used as "bags" and the fact I am a bit shaky.
2. Gun used ~1000 pounds of air for ~35 shots.  I had hoped to shoot enough to be certain... but not going to stress it too much.  This was of interest to me as I am going to install a Huma reg next.
3. I maybe took too much slack out of the connecting rod from trigger to the sear mechanism, and the trigger pull is perhaps too light.  I really did not feel a "first stage".  I find it a pretty pleasant trigger as is, but may experiment upon it later.


Next steps:
1. Get a range bag for pellet rifle shooting to hold key gear in one place...
2. Get a broader variety of pellets so I can see if gun is pellet sensitive or I was simply lucky with the pellet mix I shot.
3. Install Huma regulator

My primary goals for this little airgun project: 
1.  Get some experience on inexpensive gun.. if something goes wrong I wont be crushed and angry with myself.
2.  Learn about basic accuracy improvement possible via nice crowning, barrel polish, port smoothing
3.  Improve shot count of air fill.  Now that the barrel and simple port work is done, my next real priority.  I am using a Four Uncles pump... increasing shot count is pretty important now.  If I really enjoy this, will likely buy compressor.  For now, waiting. 
4.  Reduce report... tinker with some custom wipes, dampening material, etc. etc.

Immediate next steps (simpler / less time consuming stuff first)
1. Install Huma reg
2. tinker with sound dampening material in existing silencer chambers and perhaps improved wipers- felt?

Longer term:
1. Change hammer/spring items:  de-bouncer/spring stop device (SSD), mass, length, etc.  I think the SSD is a must-do project, but will take an afternoon I don't have right now.  I really want to conserve air. 
2. Play with trigger.  Watch airgun detective video, etc. and try something new.  I improved an old benjamin nitro piston break barrel about a decade ago, simple enough then, and the results were well worth the time spent. 

General comments- having something to do with my machine tools is GREAT.

What this gun is NOT about, at least now:  small game hunting or power tuning... If all other stuff works out might consider in future for sparrows and squirrels, but for now just for paper targets, spinners, plinking, and education.

[luge007]

A belated welcome to the forum.


A quick note on 'suppression' and 'wipes' for airguns......you are welcome to try wipes, but most have discovered it radically throws off accuracy.  You might trylooking up a member going by "Subscriber"  (as well as several others) for ideas/STL files on quieting down your project.  There are even a few members on this forum who manufacture devices that may help you out if you choose to buy something instead of build. (simple searches will swamp you with reading material)


and finally "beware the dark side" The rabbit hole of PCP's runs deep......


Cheers,
M