the way I do it

[alacran]

In the last couple of months, XX54 was asking about 90 degree V router bits for inletting barrels. A few days ago P. Bingham started a thread regarding the Carvermaster. I have been inletting all my barrels with a router as long as I been building muzzle loaders. If you ask why, David Rase hit the nail on the head in P. Bingham's post. About $200.00 to have him inlet a barrel if you add shipping.
I would like to say that I am frugal, but really I am cheap.
SDILTS asked in the XX54 post if I could post some pics. Also explain how I do it.
I used to do them with offset bushings and  had to be very careful with the set up.
Now I use these patterning bits.



The first one is a flat cutting half inch bit,it has a1/2 inch ball bearing locked above it.
upload
The second one is a 1/2 inch 90 degree V bit with a 1/2 inch ball bearing above it.
Before either of these are used you must make a pattern of the barrel. The pattern needs to be at least 3/8th inch thick.
On straight barrels making a pattern is a piece of cake. you need a 1 1/2 to 2 inch wide piece of quality ply wood or cherry or poplar' or anything similar.
 I figure how much I'm going to need and run the wood through the jointer. But you can do it with a hand plane. Then you need to glue two spacers the exact with of of the barrel and glue them on both ends.
As you can see in the photo you need to leave a space in font of the blank to start your router.
I like to use the mortising bit first  and run it down to the bottom of the side flat.
By the way I leave the blank as pictured and cut the sides after I am done routering.



After I'm done with the mortising bit I grab another router with the 1/2 inch 90 degree bit and router down to the bottom of the barrel.
However the whole job cab be done with just the 90 degree bit.
After that is done, I cut the sides of the blank down to the center line of the barrel.
XX54 uses a 1/4 inch bit to finish off the bottom of the barrel channel. I just use a chisel, doesn't take long and it gives me an indication of what the grain in the wood is doing.


When I started to take pictures, I was going to put a 15/16th barrel in this blank. But I changed my mind and put a 13/16th .45 cal Bill Moody barrel. The barrel was slightly undersized. so I applied 2 layers per side of masking tape to make up the difference. Each layer of masking tape is about .004 thick.
Once I make a pattern for a straight barrel specially pistol barrels I keep them. Just be sure to measure barrels. Best thing to do is take the barrel and put it in the pattern. If it is loose add tape, it is tight, let her rip.

Doing a swamped barrel, I do the same way only difference is I cut the top of the blank to mirror the opposite shape of the barrel. The bottom of the barrel is concave, the top of the blank is cut to the convex of that shape.
Also I laminate the patten on the blank with two layers of 1/4 inch Baltic birch. Also I screw the pattern to the outboard edges of the blank, don't want the thing to move while you are routering.
Normaly I would have thown this pattern for a swamped barrel for a jaeger project, But for the last 3 months my little shop looks like it has been "fragged". I found the pattern a few days ago while going through the debris.

Even though the pattern was good and tight all around the barrel, I didn't want to take any chances with an 80 year old Bastogne walnut blank.

This is the Barrel in the blank.
Hope this hasn't been as confusing to grasp as it was for me to post.

[canadianml1]

Thanks for your post. The explanation for straight barrels is clear but I don't understand how you control the depth of cut and varying flat widths involved in a swamped barrel channel. Could you please clarify this aspect. Thanks.

Grant

[jerrywh]

alacran.
  I have been doing it the same way for about 22 years except I don't use a router. I made a sort of duplicator with a router head on it and I use the same kind of bite as you on the router head.
  By the way my setup is for sale. it would be expensive to ship.

[P.Bigham]

Thanks for taking the time to post this.  Jerry Iam sending you a PM on your machine. 

[alacran]

Thanks for your post. The explanation for straight barrels is clear but I don't understand how you control the depth of cut and varying flat widths involved in a swamped barrel channel. Could you please clarify this aspect. Thanks.

Grant

You have to cut the top of the blank so it has the shape of the swamp. If you look at the barrel in profile, you see the bottom of the barrel looks kind of like an arch. You have to cut the top of the blank so when  you put it up against the barrel it fits in the arch. When you router it the router follows that shape . in other words it cuts deeper at the breech and at the muzzle. It cuts shallower at the waist. Just as it cuts wider at the breech and at the muzzle.

[canadianml1]

Thanks for the clarification. This is a very interesting topic to me as I plan to make a swamped barreled Soddy from a blank and would like to machine in the barrel channel.

I now understand that you shape the top surface of your tooling to control the vertical position of the cut, which varies to match the barrel taper(s).

On swamped barrels the width of the barrel flats vary as the size of the octagonal section varies along the barrel's axis. Since the cutter dimensions are fixed, how does your method address this?

Many thanks.

[galamb]

The (pattern) cut into the plywood template would provide the "guide" that the router bits follow from (side to side) and the profile cut into the top of the blank would give you the (depth changes) from top to bottom.

[alacran]

Canadianml1, if you are going to build a Soddy, you are going to be dealing with a barrel that is in the 1 inch atf or bigger. They have big hunking barrels in small calibers. The barrels have little swamp if any. Usually less than .065. I'm sure someone will come up with a light weight Soddy.

 The biggest problem when you do a swamped barrel, is that the breech section of the barrel tends to be wider than the muzzle. so you have to pick what depth you are going to run the router to. I like to run it to the smaller dimension and then finishing the breech area by hand. That is the most important area to have a tight fit.
I believe by your posts that you are fairly new at this. Do not know how  experienced you are using routers. I should have mentioned in my first post, that you should run the router down in multiple bites. Also the first go around you may want to try it on something other than a stock blank.
I've been running routers in many different applications, where patterns are involved. Some of the details I take for granted.
Galamb explained it well

[Scota4570]

I use a milling machine to rough out the channel. 

[Craig Wilcox]

Canadianml1, as Alacran remarked, take the wood off gently with the router - I usually go at most 3/16".  And a 2 x 4 is splendid to practice on!  Arrange your guide so you are cutting into the 2" wide part (yeah, actually about 1 5/8" nowadays).
Keep the router bits sharp and clean, and they will make nice smooth cuts in your rifle blank.