What should I do? Custom cast .725 slug or .725 "E" reamer to the bore???

[cpileri]

Hope someone can help.
I am back to a shotgun i mentioned before; which has a .720 bore, then a constriction where the forend screw female shank was welded to the barrel (it also is full choke down to .701, but more on that later) and I am working on getting rid of that constriction first.

I got a set of 12ga bore hones and have been honign away at the area of the constrcition. And honing...and honing...and honing... and the constriction i still there. I suppose I will either succeed eventually, or wear out the abrasive on the hone. Either way, its taking like forever to make minimal progress. The bore is nice and shiney though!

I am thinking there must be a better way, and am thinking either fire-lapping out the constriction, or taking a bore reamer and just re-boring the area of the constriction.

If I fire-lap, I will need to pay a custom
caster to make some .720 diameter BHN ~15 slugs that have a long bearing surface -smooth sides as opposed to ridges or "rifling" or lube grooves- to hold lots of firelapping paste (I have the LBT type by Veral Smith ready to go), but are hollow base so they can obturate to the bore and remove the constriction. I know that the mold for these are available (ex these: http://cdn2.armslist.com/sites/armslist/uploads/posts/2011/11/18/232135_01_cast_shotgun_slugs_12ga_for_re_640.jpg but without the cross bar running through the skirt) but I dont have one. So thats me $timulating the economy with that purchase, plus the reloading (which i consider fun) etc.
Other consideration on that would be wether i would risk splitting my barrel as the above slug swaged down to .700 at the fixed full choke?
To be honest, i am almost ready to just lop off 2" of barrel and re-install the front sight and make it a cylinder bore.

Or...

brownells sells bore reamers in both "D" (.656" - .718") and "E" (718" - .781") ranges, plus the centering bushings;
http://www.brownells.com/gunsmith-tools-supplies/barrel-blanks-tools/reamers/shotgun-reamers/gilchrist-precision-choke-reamer-16-12ga-d-reamer-sku170-100-104-4974-11147.aspx
and
http://www.brownells.com/gunsmith-tools-supplies/shotgun-tools/choke-tube-tools/choke-bushings-prod25284.aspx
which i can use to just ream out the constriction, and the whole bore for that matter. I was thinking of taping some sandpaper to a dowel and using that, but that is too sloppy. Problem here is that each reamer is $93-99, and I would need both to get the constriction to .72, plus about 12 bucks each for 2 bushings. The whole shotgun cost about 100$.

I am looking for advice, experiences, etc: what would you do?

I am trying to make a nice slug shooter out of this gun. Is that too much to ask? :)

C-

[cpileri]

Ok, here's anothe rthought: am i off target with the skirted slug? do i want a solid or round ball?
here's my thinking:
Initially I wanted the skirt to obturate before the constriction, and then be safe to swage down at the choke. but now I wonder if the skirt will re-obturate AFTER the constriction, and try to lap the rest of the bore where I dont want it necessarily?

Therefore, would a solid or RB cast to proper size help abrade off the constriction, and then stay "small" as is scoots down the bore? If I do that, i will most certainly cut out the choke to avoid any problems.

C-

[LUTNIT]

I believe a carbide reamer is used to remove chokes and constrictions. Honing stones are just used to polish it up after the reaming is done. I've never done it myself but that is what others have mentioned. Do you have any gunsmiths near you that may have the tools? Maybe get it done professionally for less money. When polishing steel (not firearm related) I have noticed a very slight bump and have tried to get these out with course polishing paper before and it's never worked. I always need to back to the bastard file and then polish from scratch again.

The pressure by the time the slug gets to near the end of the barrel is quite low. How low and how much pressure is needed to re-obturate will depend on many factors such as the specific load, thickness of the skirt, hardness of the alloy, and other things I'm probably forgetting. The slug may hit the sides of the barrel if it doesn't obturate again and this could really screw with the accuracy.

[longbow]

How much constriction is at the welded screw? If just a thou or two then it should fire lap but if much more I think you would be best using a reamer.

Something else you might try is to cast a slug in the barrel then use that to lap out the tight spot. You could rotate it slowly with an electric drill at the tight spot until it is removed then lap full length of the barrel to make sure it is evened up. It may take a few slugs but should work fine if you are careful. You could start with fairly coarse valve lapping compound then go finer after the constriction is about gone. Then maybe fire lap to polish.

As for the chokes, if you don't mind shortening the barrels or reaming the chokes out, you are better of without them if this is to be a dedicated slug shooter.

I would be inclined to use a solid slug or ball for fire lapping. I think a hollow base Foster slug will compress too easily at the tight spot then possibly re-obturate. I am not sure how well fire lapping a shotgun barrel will go either at least to remove any substantial amount of metal. There is a jump through the forcing cone which may complicate things some too. I think you would be better off hand lapping or reaming.

Just my $0.02 worth.

Longbow

[cpileri]

You all sure have given me good advice so far, in this and other threads. i am wondering now if a rod attached to a slug )properly sized) and embedded w polish would be the way to go...
Then hone it up to smooth it all out again.
C-

[cpileri]

What would be the best abrasive for grinding down the constriction? The bore hones I have are smooooothe, but not designed to take off much metal.
I want to make short(er) work fo it, but not dig a ring in the bore in areas that dont need it.

I was thinking of tapping a long lead slug (if I can find one)down to just ahead of the constriction to get the dlug to bore size, then applying the compound and pushing it to the constriction before turning on the drill. I expect to have to do it a few times since I will probably mash up the sized slug before the constriction is removed.

If I had a lathe, i could get a mild steel rod to the correct diameter, but i dont have the capability of doing that precisely.

I'm still in the planning phase- although will start very shortly.

(right after I load up those round ball slug loads i have been going over in other threads!)

C-

[longbow]

I use valve lapping compound. I have Permatex 475 which I am assuming is the grit. There is no other marking.

I have lapped several moulds and two barrel with it all successfully. It is a bit coarse and leaves a slight texture on moulds but the two barrels I lapped came out very nicely. I would go finer for finishing but I couldn't find anything locally and would have to order a rather expensive industrial size "tub" to get anything finer.

This seems to be a common grit here and is available in 4 oz. tins. I have to figure it is "adequate" for folks lapping valve seats by hand. It is coarse enough to remove metal fairly quickly but does leave a pretty good finish.

Nonetheless, if you can get finer, start with something around 400 to 500 grit then go finer to polish or use your brake cylinder hone to finish.

I would use a soft lead slug and it should be slightly under bore size when you start or it may jam up once it has lapping compound on it. The grit will impregnate the lead and make the lap larger in diameter. Your idea of pushing the slug through first is probably a good idea. i would oil it and drive it through then lightly coat it with lapping compound and drive it through again a time or two until it slide through easily, then turn it.

Don't spend too much time at the constriction without checking, you don't want a jug choke part way along your barrel! A little turning is probably all you will need, then long strokes right through the barrel.

Another thought occurs to me too, not sure about your access to a good gunsmith but if there is one nearby you might check to see if he can swage the tight spot out for a reasonable price.

If it is just a few thou then lapping should do it but if it is significant (more than about 0.003" or 0.004" strikes me as significant) then maybe swaging it out would be better. I have been told that sized hardened slugs oiled up and driven through the bore work to remove dents then there are hydraulic systems and this expander:

http://www.ebay.com/itm/12-Gauge-Shotgun-Barrel-Dent-Remover-Gunsmith-Tools-/110925608496?pt=Vintage_Hunting&hash=item19d3ae7630

and here is a write up on a home made fix:

http://www.thehighroad.org/archive/index.php/t-521265.html&&

You have to paste the links to photos into your browser but they work. Pretty slick and kind of like the hardened slug idea but with some help from the outside with a copper hammer.

Anyway, you have options.

Longbow

[cpileri]

Well, I bit the bullet and bought the brownells reamers and bushings. Its slow going: oil, ream, brush off chips, clean bore, more cutting oil, lather, rinse, repeat...
I have been getting a few minutes each day, and its by hand, so at this rate i'll be done in a few short months no doubt! (joke)

Anyway, i will let you all knwo how it goes, fwiw.

Thanks for all the good advice!

C-