PDA

View Full Version : Question about shotgun barrel mods


rezman
December 21, 2002, 01:16 PM
Does anybody have any tips for a home gunsmithy to use to modify a shotgun barrel?

I picked up a used 870 and want to turn it into a HD shotgun.

I'm looking for advice on shortrning the barrel, like how to square/crown the cut, and how to mount a new bead?

And has anyone lengthened their forcing cone at home?

TIA

Dfariswheel
December 21, 2002, 04:02 PM
The method I recommend for those who don't have access to guided barrel facing tools is this:

Measure the barrel and mark it at the length you want it. Make SURE you do this right, and always give yourself 1/2" extra to insure you don't wind up with an illegal length barrel.
The method I use is to put a dowel or cleaning rod down the barrel, mark the length, and measure off the length you want the finished barrel plus 1/2".

Wrap a piece of tape around the barrel at the point you will be cutting.
Using a fine toothed hacksaw blade carefully make a shallow, one or two stroke cut all the way around the barrel, using the tape as a guide. Then, making two or three cuts at a time then rotating the barrel, saw all the way around the barrel, until it's cut through.
This method helps keep the barrel square, reducing the amount of squaring up needed.

After the barrel is cut, use a fine cut file to level the cut end and remove all saw marks. If you've done a good job wrapping the tape evenly, and followed the line well with the saw, it should not require any actual trimming to be reasonably square.

Using a fine cut half-round fine or Moto-type tool, lightly bevel both the inside and outside of the muzzle. You can do an acceptable job with some fine sandpaper on the ball of your thumb. The idea is to remove sharp edges, so major removal isn't desirable.

I don't recommend the use of a tubing cutter as some people have done. Tubing cutters will usually compress the muzzle as they make the cut, and can damage the finish around the muzzle.

To install a new bead, I recommend buying a Remington-type bead and ramp from Brownell's. This is the same unit Remington brazes to their Police and HD guns, and eliminates drilling and tapping the barrel for a press in or screw in bead.
These can be attached by soft soldering to the barrel, and will take all but the most abusive use.

To attach the ramp, align and level the ramp on the barrel, then mark around the ramp with a very fine lead pencil.
Leaving a narrow border INSIDE the pencil lines, remove all bluing from the barrel and roughen the area slightly. The idea is when you place the ramp back on the barrel, you will see NO bright metal. This insures that no solder will be visible when finished.
Remove all finish from the bottom of the ramp and roughen.

Buy some paste-flux SOFT solder from Brownell's. Unless you are prepared to refinish the barrel, don't attempt hard silver solder/braze. The soft solders flow around 450 degrees, the true silver solder flows start around 1100 degrees.
There is a silver BEARING soft solder that is a soft solder with about 3% silver added as an anti-tarnishing agent, but this IS NOT real silver solder. This type of soft solder is preferred for gun work, since it doesn't tarnish and is somewhat stronger than standard soft solder.

Apply some anti-flux to the entire end of the barrel around the area to be soldered. This will prevent any solder that oozes out from the sight from sticking to the barrel and damaging the finish.

Clean the bore of all oil or lube, DO NOT attempt to plug or seal the muzzle.

Apply a thin coat of solder/flux to both the barrel and the ramp, and position the ramp upright and square on the barrel.
Unless you have the special ramp clamping device from Brownell's, I don't recommend attempting to clamp the sight. Most clamps will either tip the sight or simply fall off the barrel when the solder flows, knocking the ramp assque.
If I feel a need to clamp, I'll use a large screwdriver to press down on the ramp as the solder flows. It helps if you have a buddy to either apply the heat or hold the ramp down, whichever you prefer. Clamping or pressing the ramp down firmly does help insure a better fit and hold of the finished job.

Apply heat with a torch to both the ramp and barrel until the solder just flows, hold for a few seconds longer to insure a full flow, then pull the torch slowly away from the work area. DO NOT over heat, remember the heat needed is only 450 degrees.
If you are holding with a screwdriver, hold until the solder sets, usually 15-20 seconds.

Go away for 30-45 minutes.
When the barrel is cool enough to hold in the hand, take it plastic screwdriver handle and TAP, (not smack) the ramp to insure a good bond. Then take the barrel to the sink and give the entire barrel a scrub down with hot soapy water and a toothbrush. Also soap the bore. This removes any flux.

If necessary, clean up any excess solder, and touch up with cold blue. Lube inside and out to prevent rust.

Done properly, the ramp will stay put very well.

The same general instructions work for silver braze/solder but the higher heat will destroy the finish, and can damage the barrel if not done correctly.

rezman
December 21, 2002, 08:32 PM
Dfaris,

Thank you for the excellent explanation. I would like to shorten my barrel to 20" and with your guide it shouldn't be too difficult.

Does any one have any pointers on creating a long forcing cone using a brake hone?

I read an article someplace in the past year about doing this modification but can't remember where I found it.

It seems that by creating a slightly overbore (10-15/1000's) jug in the bore in relation to the muzzle diameter, smaller patterns can be acheived.

Anyone remember the article or done this themselves?