how is the leade in and barrel port made?

[1377x]

seeing that rsterne asked his 2-shot breech question here i think this is probably the right place to ask my question
a lot of people are making there crosman guns a larger caliber let's use the .25 barrel liner for this question
so i go and buy a .25 barrel liner. i want to use it in a crosman steel breech. a bolt,leade in and barrel port has to be made for it to be used in the crosman breech
how is this accomplished?
what has to be done to properly make the leade for loading the .25 pellet into the barrel?
what has to be done to make the barrel port?
tools needed?
a step by step would be very helpful
there are a few of you that know what you are doing.i have been reading about .30 caliber marauders,.25 discovery's,.308 and 9mm discovery's.exactly what steps are used to make these barrel liners work in these breeches
Lloyd s-s,rsterne,rescue35,workingmanva,timmymac,fivestar45
i would like to hear your techniques if it isn't to much trouble.any info,video's or instruction you can point me to would be a great help. if there is a technical term other than leade in it would help to know that too
all help welcome and appreciated
ED

[rsterne]

The proper way to make a chamber and leade is with a custom reamer.... I don't know of anywhere you can buy an "off the shelf" one, so most people would make their own.... It can be done with a selection of drills and then cobbling up a reamer of sorts but the best way is to use some drill rod (O1 tool steel), machine an accurate reamer that will cut the leade and chamber in one operation (and the taper for the bolt O-ring if used), harden it, and then carefully ream out the barrel.... Making the reamer requires a lathe and milling machine.... The diameter and length of the chamber are important, and the leade (which guides the head of the pellet into the rifling) needs to be the correct angle (1.5* is typical) and in the right location for the intended pellets.... Note that it is not possible to have one leade location perfect for different lengths of pellets/bullets, so a compromise is usually required....

The ports can be done in a drill press, but the best way is to use a milling machine (or a milling attachment on a lathe).... They need to be the correct distance from the breech end of the muzzle, square and centered with the bore, the proper diameter, and the flat for the transfer port to seal against needs to be the proper diameter and depth.... Deburring the bore afterwards is critcal to prevent pellet damage....

If some enterprising machinist is interested, there would be a SMALL market for custom chambering reamers in the common (standardized) calibers, .177, .20, .22, and .25.... There would be an even smaller market for .308 cal and .357 cal reamers and larger.... but as the caliber increases, so does the diversity of diameters (eg. .45 cal are usually 0.452" or 0.458" but can be other).... so in most cases a custom reamer would be the way to go.... Since few home hobbyists would be capable of using a chambering reamer properly (or have a lathe), it might be more cost efficient to ship the barrel to somebody equipper to do the job, get a quality job done, and then ship it back.... I would like to be able to purchase chambering reamers in .22 and .25 cal that cut the leade and a parallel chamber only, where I could determine my own depth.... but I'm probably in the minority, so I will likely have to make my own.... and no, I don't make stuff for others, I barely can find the time to do my own projects....

Bob

[BALLISTIC1]

I have not used them but when I read about using a 'tapered pin reamer" I thought that it might do the trick and come in different standard sizes.... Greg

[rsterne]

The chamber is parallel from the breech to forward of the transfer port.... It's diameter is larger than the groove size of the rifling up to the size of the skirt for a pellet, or slightly larger than the groove diameter (and the sized diameter) of a bullet.... It's purpose is to provide alignment with the bore while not adding any resistance to loading which could damage the pellet/bullet.... If you happen to have a drill the right size that may work for that portion, if centered perfectly.... Without a pilot on the drill that would be hard to achieve consistently.... Sometimes you might be lucky, sometimes not....

The leade is a tapered portion ahead of the chamber, at a shallow angle of a degree or two (1.5* seems typical) where the bore transitions from the diameter of the chamber to the rifling.... The rifling lands are partially removed in that tapered portion, producing a cone that "leades" or guides the nose of the bullet into the rifling, centering it with as little damage as possible.... In order to insure an even taper on all sides, the chamber must be concentric with the bore, and the reamer used to cut the leade must have a "pilot" of the correct size to enter the bore and turn without damaging the rifling.... Some airguns have very little leade, the chamber ending in an almost square shoulder where the rifling starts.... That may be a simplification for manufacturing purposes, and may very well work OK for pellets because of their diablo (waisted) shape, where the length of the head portion where it is bore size is very short.... and the lead scraped off by entering the rifling has a place to go (into the waist).... With (properly sized) bullets, you will likely find that a very abrupt (on no) leade will result in hard loading because of the resistance of the nose of the bullet to entering the rifling.... The shallow taper of the leade eases that transition, making loading easier and less likely to damage the bullet....

Other than in a springer, I don't see how you could use a simple tapered reamer to achieve a proper leade, as the leade is the full length of the chamber inside the bore.... It starts ahead of the transfer port because only the nose of the pellet/bullet enters it during loading, not the skirt/base of the pellet/bullet....

Bob

[1377x]

im listening
it is really going to be cost effective for me to learn this.with the money spent on getting barrels cut,i could have bought a lathe by now.with the left over portion going to waste i could turn it into another barrel if i know how.i am mechanically inclined.you guys all remind me of my dad with the precision of your work.he was an engineer also and precision was everything.when your young you do as you will and when its too late then you want to listen.im listening now!! before it gets too late again.
thanks for the help
keep it coming please,
ED

[1377x]

i was looking at 4.5mm reamers but thats just big enough for the pellet.i take it 5mm is to big for a 4.5mm/.177 pellet
with a properly made tool,could this be done on a lathe? i have a pdf file on sharpening lathe tool havent opened it up yet,hope there is some useful info in there
this is the stuff im going to be reading it looks like its going to a big help
https://sites.google.com/site/bobdole42nd/pdf

[PakProtector]

On making your own, Greg's tapered pin reamer would serve, but you'd put it on a surface grinder with a rotating chuck to cut the thick portion down to your pilot/chamber diameter. Ream chamber to just past the transfer port, then in with the tapered reamer.
cheers,
Douglas

[1377x]

On making your own, Greg's tapered pin reamer would serve, but you'd put it on a surface grinder with a rotating chuck to cut the thick portion down to your pilot/chamber diameter. Ream chamber to just past the transfer port, then in with the tapered reamer.
cheers,
Douglas

do you have any more info on the tapered pin reamer?
pak,greg???

[BALLISTIC1]

I HAVE NOT USED THESE BUT READ ON THE YELLOW FORUM SOMEONE THAT DID and I do think they could work well ...I just searched 'tapered pin reamer' lots of charts and graphs etc... Here is a link, depending on caliber I think these could have some promise... On my big bore I did use a regular old tapered reamer, it worked okay and seemed to cut much smoother than I had expected... http://www.stanlok.com/Taper_Pin_Pages/taper_pin_reamers.html. Greg

[1377x]

I HAVE NOT USED THESE BUT READ ON THE YELLOW FORUM SOMEONE THAT DID and I do think they could work well ...I just searched 'tapered pin reamer' lots of charts and graphs etc... Here is a link, depending on caliber I think these could have some promise... On my big bore I did use a regular old tapered reamer, it worked okay and seemed to cut much smoother than I had expected... http://www.stanlok.com/Taper_Pin_Pages/taper_pin_reamers.html. Greg

sounds good but i got a 404 instead of a site
if the pellet/bullet loads smoothly and seals with no leaks wouldnt that be better than okay?

[1377x]

I HAVE NOT USED THESE BUT READ ON THE YELLOW FORUM SOMEONE THAT DID and I do think they could work well ...I just searched 'tapered pin reamer' lots of charts and graphs etc... Here is a link, depending on caliber I think these could have some promise... On my big bore I did use a regular old tapered reamer, it worked okay and seemed to cut much smoother than I had expected... http://www.stanlok.com/Taper_Pin_Pages/taper_pin_reamers.html Greg

sounds good but i got a 404 instead of a site.there was a (.) at the end of the address removed it and the page popped up
if the pellet/bullet loads smoothly and seals with no leaks wouldnt that be better than okay?

[PakProtector]

sorry...never used one. Just getting into this scary modification stuff. Probably know just enough to start and have to do it a few times to learn the details I don't have any idea even exist...

Check out:
http://www.victornet.com/subdepartments/Taper-Pin-Reamers/2548.html

One starts out at .2071 and goes to .2601 across 2-9/16". For a .22 cut the chamber at 5.55 and grind all the reamer away that is bigger than that 5.55. That looks good now...what don't I know?
cheers,
Douglas

[rsterne]

It's been a loonnngggg time since I had to use a SIN function.... but my calculator says that works out to only 0.6* per side, which is a lot less than the recommended 1.5* taper per side for a leade.... Will it work?.... probably.... My question would be how are you going to cut the chamber accurately to 5.55 mm and concentric with the bore?.... How about holding the reamer straight so that it will remove the same amount of rifling on all sides?.... It won't have a pilot.... Would I try it?.... heck yes, but on a Crosman barrel, not a Lothar Walther....

Bob

[1377x]

i hear that!
i have a few crosman barrels to practice on and can get some more for practice when guys swap out barrels the old barrels are usually given away.
they will be put tp good educational use
can a lathe be used to cut leades and chambers? it sounds like its best accomplished by hand with a pilot
mr.sterne with your tools and know how, was it very hard to make the tools you use for cutting leades and chambers?

[PakProtector]

Bob...I think you used the arc-Sine function...

A lathe can be used. Cut the chamber with a boring bar. Take the modified taper reamer that will 'pilot' from the rear and run it in. It will be difficult to get the diameter to match well...getting a cutting edge profile so that it reams the chamber a wee bit larger as you run it in will take care of that. Some experiments will be needed...
cheers,
Douglas

[rsterne]

mr.sterne with your tools and know how, was it very hard to make the tools you use for cutting leades and chambers?

I'll let you know the first time I do it properly.... I've only done a couple, and I used a drill for the chamber and a "reamer" made from mild steel (I didn't have any O1 drill rod at the time) and sort of "wore" the leade in by hand.... Crappy method, but it worked OK.... I asked an expert and he posted his method on AGH....

http://airgunhome.com/agforum/viewtopic.php?t=8608

All you need to know except the dimensions is right there....

Bob

[1377x]

mr.sterne with your tools and know how, was it very hard to make the tools you use for cutting leades and chambers?

I'll let you know the first time I do it properly.... I've only done a couple, and I used a drill for the chamber and a "reamer" made from mild steel (I didn't have any O1 drill rod at the time) and sort of "wore" the leade in by hand.... Crappy method, but it worked OK.... I asked an expert and he posted his method on AGH....

http://airgunhome.com/agforum/viewtopic.php?t=8608

All you need to know except the dimensions is right there....

Bob

lol!
as long as its functional thats what really matters when doing work on your own guns
thanks for the link i'll check it out

[1377x]

would any of these reamers work for making the the leade chamber ?
http://www.brownells.com/gunsmith-tools-supplies/barrel-blanks-tools/reamers/centerfire-reamers/index.htm