Seeking input on shotgun barrel liners.

[300BLK]

I found this elsewhere:
"There were three different Ithaca Gun Co. hammer doubles. The first was the Baker Model which was made from the founding of the company in the early 1880s into 1887, when it was replaced by the New Ithaca Gun (NIG) at serial number 6550."

I found this auction with photos
https://www.gunauction.com/buy/7886131

 

[KeithB]

You know, this gun could well be an Ithaca. I had not seen this gun in over a year due to where I keep it and where my physical condition let me go. Shows what happens when you depend on memory only, I had no notes to look at and remembered the wrong name. I will look for (and photograph) any other markings on this gun tomorrow. In any case you can see the general configuration is as I remembered and described, i.e. a "coach gun". I don't hunt (health not moral reasons), wouldn't want to play shotgun games with it, and was happy with the thought of it being a wall hanger. But acquiring liners seems like a way to safely resurrect the old girl for limited duty.

 

[Ian]

300BLK nailed it, it's definitely an Ithaca, made under W. H. Baker's patents when he and L.C. Smith's brother Leroy split off to form Ithaca Gun Company in 1880. I have two books on L.C. Smith shotguns, but none dedicated to the Ithaca history. There is so much the internet is lacking in well-researched and intelligibly-presented information that I am always grateful to have a pertinent reference book rather than be forced to depend on google etc.

I'm betting that the Baker patents is why all the subsequent Hunter Arms L.C. Smith doubles had the separate lock plates and the Ithaca and original Baker hammer doubles had the hammers in the receiver.

 

[fiver]

I'm also thinking [best as I can see] those are NOT Damascus barrels.
steel or twisted steel, but not Damascus.

the pitting could be a concern depending on their depth and where it is located.
shot shells have that sharp uptake shown in the chart Ian posted, but the pressure drops off just like the chart shows also.
there is almost no pressure about 2" down past the end of the hull mouth.


that's a pretty nice piece of wood.

 

[300BLK]

"In 1883, Baker, Smith, and several partners moved to Ithaca and established the original Ithaca Gun Company."

Baker Double Barrel Shotguns


Serial Number Year of Manufacture




1 - 2447 1880 to 1885 *****serial 2121 falls right in here*****


2448 - 4104 1886


4105 - 7003 1887

 

[Pistolero]

Barrel steel in the photos does not look like Damascus steel, but perhaps just the photos.


Damascus



And perhaps it is a distinction without a difference.


Bill

 

[fiver]

I think the difference was iron and steel.
they both can suffer the same problem of rust, and I'm sure that is the main concern here. [as it should be]

if I had the wherewithal to make my own liners I would probably do them in 16ga.
it wouldn't be as easy to procure ammo at every general store on the planet but it would keep the weight in a realistic zone and provide some better ballistics, terminal performance, and payload weight.

 

[KeithB]

Fiver, I agree with your reasoning about making it into a 16 gauge. Considering the fact that I probably won't shoot it 25 times the rest of my life the cost of buying one box of good shells is insignificant. I was thinking 20 gauge because it would make a little thicker liner and I already have a 20 gauge shotgun, a Lee loader in 20, and several hundred empty cases and wads. But at this point my mind is still open.

 

[Pistolero]

The diam of 12 ga chamber is .798, 16 ga chamber is .685. Wall thickness of a 16 ga insert would be 0.0565".
Hoop stress controls, so stress = Press * Mean Diam/2 wall thickness.

Assume 20,000 psi peak pressure, mean Diam = 0.7435". This puts peaks stress in insert, if entirely unsupported,
at 131Ksi. That is entirely doable with a heat treated alloy steel liner. If you use the readily available, and
easy to machine 4140, heat treat by oil quench from 1550F, then 800F temper, you get yield stress at 195ksi, which
gives a ~50% stress margin. Ultimate stress is 210Ksi. Temper at 700F gives yield of 212Ksi, ultimate 230Ksi.
Yield would actually just tend to lock the liner in place, not a bad thing, just considering worst case failure mode
behavior. Would not happen.

The liners would be quite light, adding relatively little to the weight. Might epoxy them in place to prevent some
future person from harming themselves if they didn't understand. Exterior original barrels, if epoxied, would actually
provide massive reinforcement, creating huge safety factor. Inner liner would guarantee no local failure if there is a weak
spot.

OTOH, making a .0565 thick liner might be a challenge on the lathe. Deep boring would need a long drill and reamer,
large size. Perhaps a piece of 4130 chrome moly seamless aircraft tubing would be a more reasonable starting point. 4130 will
heat treat to about 160Ksi, but with only 30 points of carbon will not get quite as high yields as 4140. But having relatively
cheap seamless tubing as a starting point may be the controlling factor.

Talk to the machinist Keith, if the engineer Keith thinks it might work.

Bill

 

[300BLK]

Keith's double is a 10ga, so liners will be thicker, stronger, and heavier.

 

[KeithB]

Bill, agree 100% with your calculations and material selection choices. I've found it's usually easier to do things to the outside of a part, so if I could find some 4130 tubing with something close to the proper bore size for a 16 or 20 gauge and enough wall thickness to match the max OD I'd probably use that. Turning the OD of long, slender parts can be tricky but since the max length would be about 20 inches I think I could chuck it in the middle, support it with a plug w/center hole for the tailstock, and turn half of it at a time. Blend the whole thing together with a lathe file. Any details on the ends (choke and chamber) can be done with the barrel inside the lathe spindle (my manual has a 2+" center hole) and the appropriate end sticking out of the chuck.

 

[fiver]

the great thing about shotgun barrels is they don't have to be exact.
even 10-K guns will quite often measure out with a couple thousands difference between the top and bottom barrels.
the trick is to get the choke constriction right as measured off the bore measurement.
in this case something like .005 near the muzzle would be more than enough to get the job done.

the test pressure for a 12ga 2-3/4 or 3" is 19,000 psi B.T.W. the max pressure for a 3-1/2" 12 ga. is 15-K but it's only tested to about 22 or 23-K psi.
so we are working under the 22lr even as the proof test.

 

[Ian]

I'm wondering if a little phosphate-based cold blue like Brownell's Oxpho paste would make the pattern of barrel steel "pop". Since the Oxpho blue does absolutely nothing to existing rust, it can make a nice contrast. I've used cold bluing to bring back faded case colors on a few occasions, and it did a really neat job bringing out the colors in a Damascus knife.

 

[Pistolero]

OK, with 10 ga, 4130 would probably be fine as it arrives, in normalized condition. Normalized 4130 has about 60KSI yield and 90+KSI
ultimate.
Yes, it does seem that long parts can be problematic. I would presume that for the limited duty and purpose, the surface finish with
a piloted drill would be acceptable for much of the interior, with a chamber reamer rented for the actual chamber.
Comparitively, the exterior would seem to be much easier. What about a follow rest? I have one, have never used it, so not too sure
if it really works well. Of course, of the clearance on the outside to the original bbls is .010 or so, with O-rings to center, exterior
taper error becomes much less critical.

Bill

 

[Pistolero]

7/8 4130 aircraft tube comes in many wall thicknesses. The 7/8 -.095 wall, is attractive. ID works out to
exactly the chamber diam of a 16 ga. May not need to do anything except clean up any ovality in the chamber
area with a light reamer pass, bore should be OK as is. That would be a huge work saving.
Exterior is .875, 10 ga chamber is .841, so only a .034 cut plus whatever clearance you decide on on the exterior.
Starting to sound too easy.

Wickes Aircraft is where I have bought 4130 tubing back in my aircraft building days.
http://aircraftproducts.wicksaircra...metal-tubes-channels-angles/4130-round-tubing

$8.15 a foot.

The next thicker wall if you don't trust their dimensions, is .120, far more interior work, price is actually lower
at $6.55 a foot. I guess rolling it thinner is harder to do. Also, a chamber diameter for full
length is not normal, so if you wanted a proper interior shape with a reduction in diam
after chamber, the thicker wall would be needed. Given the intended service, and desire
to spread max.... plus massive reduction in machine work, seems like chamber diam full length would be OK.

Bill

 

[fiver]

with the ID so close with a standard piece.
it would probably be easiest to actually measure the barrel ID then cut it with threads for a choke tube to get the constriction rather than trying to remove material from the barrel itself and leave the smaller ID behind.
which would for sure make things easier [cheaper] since you could find basically any brand then cut the threads to match.
at the worse you'd have to inside ream/polish the barrel a titch for an inch or so to match the base of the choke.

just to make things easier and for a little more info.
at 20 yds a straight barrel [with no choke at all] would still throw a pretty tight pattern with the larger shot sizes.
when I shoot steel shot [12ga.] in sizes like #1 or B or BB I use an improved cylinder to throw an actual light-full choke pattern at 40 yds.
in the smaller gauges the shot is proportional.

a 20 will throw a full pattern with #2's and an improved cylinder choke.
I wouldn't even try #1 or bigger, your payload would be about 8 pellets and you take too much of a chance of bridging the shot in any type of constriction even with a buffering agent.