grinding out chamber ?

[crankshaft]

 I want to use various parts accumulated over time to make another  trade gun.  I have a rusty 12 ga. bbl I don't want to cut off 3 " of the chamber like I did on the last one  in order to keep it as long as possible. 
 What do you think... if I grind out the chamber edge, it would make a kind of choke, but for shot would this be a problem?    I will be a beater  gun left in the barn to mainly shoot starlings.

[L. Akers]

Make a breechplug that fits the chamber-including the forcing cone.  See Brockway's book on recreating muzzleloading shotguns.

[Jerry V Lape]

. Solution I would prefer would be to sleeve the chamber and forcing cone to match the bore and put a typical breech plug behind it.   You might get away with just putting in a breech plug  but that could make it tough to get a good enough seal in the chamber because it will be larger diameter than the bore possibly  allowing gas to get around the wad before the barrel was sealed.  The forcing cone won't cause a problem and it will not give any choke effect as it is too far from the muzzle to have any sustaining effect on the shot column. 

[crankshaft]

sounds like a plan.  thanks,

[Hungry Horse]

 Just a little information from someone who has been down this road. I did just what you proposed to a miniature trade gun in .410 for my young son. I just cut the external threads off of a shortened smokeless shotgun barrel, and added internal threads for a breechplug. What could go wrong? The first time we shot it with shot, we discovered that in that short barrel the old force cone worked just like a jug choke, when loads were shorter than the original cartridge, My young son busted a clay at thirty yards with the little gun, and it was the first time he shot a shotgun. Two adults shot the little gun because we couldn't believe it. Sure enough, she shot a pattern about the size of your gimme cap, at thirty yards. But, when loaded beyond the force cone, it shot like any cylinder bore shotgun with an eighteen inch barrel.
 I don't know what it will do with a bigger bore, and a longer barrel, but it might be interesting.

  Hungry Horse

  Hungry Horse

[crankshaft]

 No external threads to cut off...it is a break open bbl.

[Hungry Horse]

You still will be shortening the chamber by the length of the breechplug. I think when shooting shot the effects will be mostly positive, but shooting round ball may be another story.

  Hungry Horse

[Jerry V Lape]

Well I am certainly surprised the forcing cone acted like a choke in this manner!  Goes against everything I know about chokes.  An overly long straight section of the bore ahead of the choke constriction in modern guns tends to reduce the choke effect.  Wonder what else is going on here?  Can you describe your load please, over powder wads, sleeves etc? 

[jerrywh]

 Sorry but that is impossible.  You can only choke a shotgun at the muzzle.  Once the shot travels down the bore the size of the patter has been set no matter what it started out to be at the breech end. The only way to change the pattern then is to alter the muzzle. Argue all you want. This has been established for over 100 years. Go read the gun and it's development.

[Hungry Horse]

So how do you explain choked patterns from loads with less overall length than the existing chamber, and open patterns with loads that extend beyond the existing chamber? I ain't magic, there has to be a reason. And, I sincerely doubt anybody thought of creating a jug choke at the breech. His barrel is quite short, being a kids gun and all, but I'm not sure it wouldn't work on a longer barrel.

  Hungry Horse

[Hessian]

Just spitballing here but was the charge that extended past the forcing cone a heavier charge? To extend farther down the barrel there had to be more shot or more powder in the charge column. Perhaps that had something to do with it?
Hessian

[jerrywh]

 No matter what the load is at the breech as it hits the bore it becomes bore diameter all the way down the barrel.
 Your argument is a joke. You won't fool many guys on this forum. Furthermore, when you choke down the load at the breech like that you raise the pressure at the breech because you are forcing the charge through a restriction in a small amount of space. You are raising the pressure to abnormal pressures.  You have no idea what the breech pressure is. Your only salvation might be that the barrel is modern shotgun steel. When it comes to guns and pressures ignorance can kill you or someone else.

[crankshaft]

   If I may inquire,  where can I get a plug for the .800 ?  I don't think TOW has and plug this large.  what size drill and tap for the .800  ?   .796= 51/64  84%
  If memory serves. the last one .577 was made with a bolt with welded tang.  It was a few yrs ago.

Wait...wait...TOW does have a 7/8x 14 plug........

[Hungry Horse]

Jerry;
 It's a flintlock, which is a vented breech, it was initially loaded with 30 grains of 3F for a child, it was witnessed,and tested, by several old suspicious buckskinners. They shot as it was originally loaded, and then they shot it with a load that was the same except for an additional cushion wad, to extend the charge beyond the force cone. Oh, and since you have never experimented with this, who made you the expert?

 Hungry Horse

[Jerry V Lape]

From what you are telling me, I think you are assigning the pattern difference to the wrong cause.  With a light load of powder producing a relatively slow velocity you might very well be getting a tighter pattern.  And I don't know if you are using a barrel which has any remaining choke at the muzzle.  Then when you add wads to fill the same load past the forcing cone the wads and shot may be causing a pressure rise with the wads eventually producing a donut hole  in the shot swarm as it exits the barrel.  But I do know the forcing cone will not act as a choke if the bore forward of it is of uniform dimension all the way to the muzzle.  Every experiment I have read about or know about with chokes confirms the constriction must be at or very near the muzzle.  But if it works for your son with the light load great!  You may have found an anomaly that will not likely repeat itself in other barrels and/or loads. 

[jerrywh]

 I.m an expert a because I have been doing this for over 60 years and studying it all my adult life.  Your just  lucky it's a small gun.  You are arguing against hundreds of year of experimentation.  Most debates on the internet soon turn into a matter of who is correct in place of what is correct. No body really cares who is correct. What most people want to know is what is correct.  Just go do some studying on shotgun bores and chokes some.   Go put your post on a shotgun forum and see what kind of reaction you get. Good luck on that.

[ddoyle]

Never met a barn I'd shoot a ML in or around. Smouldering patches- vented bits and barn contents do not mix well. Might have been ok in the old days when the next barn was just a batch of nieghbours away but theys expensive in cash money to raise now adays.

If ya got a starling problem a net will cut a swath in em