Leade work on Discovery

[cheerIO]

I want to build my Discovery for maximum accuracy.

I have heard talk of doing work on the "leade" or taper of the barrel but I haven't seen any particular mention of what this entails. I do notice that sometimes it feels quite rough when inserting the pellet with the bolt though.

Looking at the leade, everything seems really rough. I can see where the pellets would get caught on concentric grooves. Should I just chuck it up in the lathe and smooth things out with some Emery paper and Scotch Brite? I'm going to perform the work on my spare barrel.

Do you guys have any specific suggestions on how to approach this?

[cheerIO]

Picture of stock leade, kinda rough. 

[Gary]

Go for it. Just keep in mind that the oring on the bolt needs to seal in the barrel. So don't go overboard. You might want to check the transfer port for burrs in the barrel while you are in there.
Gary

[MustangMike]

cheerio

if you want you could prolly send a pm to lloydss or rsterne aka bob i know they know how to properly do this.

[TimmyMac1]

Leade work can be performed with a simple split end rod. If you fashion a piece of .177 rod material so it has a Hacksaw cut 1/4" deep from end perfectly centered you can chuck that and file it down to a Pointy end. Take some 180 grit Aluminum Ozide cloth backed paper and fold a 1" square in half(for .22) abrasive out and slip it into the slot.
You can take that tool and use it in the tail stock of the lathe, fit it to a drill motor or my favorite put it in a verticel drill press.
When you turn the drill press on the flapper uses centrifical force to sand the lead and if you force the issue it will deburr the transition into the rifling so the back of the lands and grooves are sanded through their respective depths. Once that transition is properly cleaned up the pellet ramps into the rifling without getting hacked and a long bolt probe is able to push the pellet fully into the rifling with minimal resistance.
You'll find the burr is rather work hardened so it will take a few pieces of fresh abrasive to finally break thru on occasion. I go 180 then 240 grit Alu Ox as a final. When done right it will clean up any accuracy issues related to the leade sizing down pellets or scraping the skirts. .20 cal uses a 3/4" square piece of abrasive and a smaller rod is used with a 1/2" square for .177 cal.
By the time you break thru the burr from the breech to rifling transition the burrs at the port and rough ness at the sealing point will be well fixed.

[Tom SC]

   I did what Tim said some months ago and it works very well. Found the bolt o-ring needed to go up one size due to the material removed from the leade. Maybe I was to agressive,don't know . Anyhow the pellet loads smoothly , bolt seals fine. I say definitely worth doing.

[Motorhead]

I use my small near worn out CRATEX points on my dremel tool.
Lead flare gets a nice polish and also run them into the freebore area and against start/lead of rifling to lightly de-burr so the rifling press's into pellets skirt/dome and NOT cutting it !
Results in accuracy have been dramatic and well worth the effort.

[cheerIO]

Thanks for all the tips guys. I'm gonna undertake this mod this week.

Mac1: Thanks a tonne for the detailed description. When "honing" should I keep the stick moving or just keep it in place contacting the end of the rifling?

Tom SC: If I need a bigger o-ring, what size are you speaking of? Nearest I can tell, the stock o-ring is an 005. I have 006's in the shop but they seem a little loose on the inner diameter.

[TimmyMac1]

Thanks for all the tips guys. I'm gonna undertake this mod this week.

Mac1: Thanks a tonne for the detailed description. When "honing" should I keep the stick moving or just keep it in place contacting the end of the rifling?

The size of the piece of abrasive controls how deep the thing wants to go in to the back of the rifling. Your just trying to break the edge and to get the best results spinning the barrel while moving it from side to side will be the most effective method to average out your cut and get the pointy end of the abrasive to work on the burr. You can look thru the transfer port and see when the transition is a nice smooth bevel. If it looks rough with the naked eye it is really bad.
I like tio look at the stuff with 7 power headset loop and you can see it good.
The Oring is a 005 for .22 when using my Probe but each bolt is different and often factory probes work better with a 006. The oring doesn't need to seal on the ID as it is sealing the bolt to the ID of the barrel and the ID of the Bolt is not a sealign point. The back of the groove is the low pressure side and that is where the oring is headed to seal when the gun fires.

Tim

[cheerIO]

Finished my leade and crown work and the results so far have been Awesome!!!

I ended up getting some of those rubberized dremel tips and turning them down on the lathe to fit the leade. Thanks for the tip on the tips Motorhead.

It is much smoother pushing the pellet in and closing the breach and accuracy has been much improved as far as I can tell right now. I have only shot CPHP's out of it but now all the holes are touching at 15 yards where before they were like .75" groups with those pellets. They were my worst shooting pellets before but they seem to be doing great now. I hope it stays that way.

I shot a 3 round 3/8" group at 60 yards and a 5 round 3" group at 90 yards also with the CPHP's. Before, there was no way I would have even been on paper at 90 yards with those pellets.

I haven't even started on my extended probe yet. But hopefully I can chuck it up tonight. When I finish the probe I am really curious to see what pellets she likes the best now. Hopefully the cheap ones. 

[stacycfi]

Today I polished the lead a bit kinda like TimmyMac1 was describing except I chucked up
a piece of bamboo skewer in a Dremel tool and split it with a Xacto.  Then slide in the emery in the cut.
Spin a couple of pieces in and out then some cotton t-shirt patches with some red rouge and high speed
on the Dremel. Then a thorough barrel cleaning.  Had to double check the pellet loaded a couple times,
it felt too smooth and I thought the pellet fell out of the breech.  It hadn't just the silky smooth load.

Thanks everyone for the tips.

Gettin 1.5 inch groups at 100 yds now with CPHP's

[Poorman Plinker]

Many ways to skin a cat!!!
Not  wanting to spray grit or change dimensions I used drill bit rod stock and semichrome which is a low grit polish to burnish the freebore and to cut a leade into the rifling. I used a .222 spiral concrete bit that I covered with vinyl tube for the freebore. The vinyl acts as a drill stop and provides a smooth surface for the drill chuck. I cut the end off of a 3/32 (.218) HSS bit and rounded the end to burnish a leade into the rifling... it does not take the entire edge of the rifling off just rounds it a bit. I also have vinyl tube on it to act as a drill stop. I do not want the pellet sliding down the barrel just want to take a bit of resistance off the pellet when pushed in by hand.
Chamber = freebore + leade. Freebore - cylindrical. Leade - conical. Or so I have heard.

[mooseslayer]

I did mine a while back as well. My bolt had a rough spot when I first got the gun and gouged the wall where it slides so I had to sand it a fair bit. It also leaked there so I used dental floss under the oring to make it fit just a bit tighter. The good thing with that is you can easily add more or take some off until it is just snug.

[oldgearhead]

My PC77 would not chamber those Gammo Red Fire pellets after I installed the steel breech.
Also it was quite difficult to chamber much shorter Crosman pointed pellets.
I used the Dremel 0.175 tapered sharping stone to form a leade and used red rouge on a .22 caliber bore brush to polish.
Now it's a bit difficult to chamber the Red Fires and very low resistance with shorter pellets. With 11 pumps and a Crosman pointed chambered
it passes the 'tissue test'..

[ScottB]

NT