Seeking input on shotgun barrel liners.

[KeithB]

A while back my BIL restored an L C Smith 10 ga shotgun that had been owned by some distant family member of mine. The action is tight and seems strong, but the barrels appear to be some type of twist/laminate composition. I will never take the chance of blowing up a twist barrel intended for black powder by firing modern loads in it. But I have considered making a full length barrel liner that would be strong enough to withstand the pressure without transferring any of it to the outer barrel. Then the only limit would be action strength.

Any thoughts, comments, or experiences you care to share about using sub-gauge liners in shotguns? My plan would be to make a 20 or 28 gauge liner for a 10 gauge break action.

 

[Ian]

Just make chamber inserts, held in with O-rings in the same manner as any "normal" sub-caliber insert. The pressure is negligible after the first few inches of shot column travel.

28-gauge is a great caliber. I have set of inserts that my FIL loaned me before he died so I could run a sub-gauge bonus round at a sporting clays match, they worked great and patterned wonderfully from my 28" 12-gauge O/U.

 

[300BLK]

Gauge Mate's site doesn't seem to be working properly, but they do list 10ga to 12, 16, and 20ga adaptors. As the gauge gets smaller, pressures go up.....
http://gaugemate.com/adapters/gaugemate-gold

Their "Gold" line stayed in the barrels and worked in conjunction with the actions extractors to remove fired hulls.

 

[Ian]

As the gauge gets smaller, pressures go up....

But but total back-thrust force goes down as case head size is reduced. This is a good thing for a weak action, and the insert should take 100% of the radial force without any support from the barrel or action. Once the shot exits the adapter, pressure drops dramatically.

 

[300BLK]

I had considered subgauge inserts for my 12ga double, but it doesn't make much sense in that I can download 12ga down to 7/8oz.

Short Lane makes adaptors as well, and the 8" 12ga to rifled 45ACP has me thinking.
http://www.gunadapters.com/pathfinder-line-with-dave-canterbury/

 

[gman]

I have 20 ga, 28 ga & 410 sub gauge tubes for my 687 Beretta. In my opinion full length tubes are much better than the chamber inserts. Having said that if you want to shoot the old 10 gauge inserts would probably be the easiest and least expensive option. Only thing is if they are compatible with your shotgun. Briley Mfg. fitted my sub gauge tubes.

 

[300BLK]

It looks like Gunparts Corp has 26" 16boreand 28bore blanks in stock for not much $$. A guy that was handy with a lathe could work these over.

https://www.gunpartscorp.com/ad/584990.htm

 

[fiver]

those sound like Damascus Barrels.
BLACK POWDER ONLY.
Damascus was made by winding thin ribbons of metal around a mandrel.

if I were going to try anything except black powder and fiber base wads, I would make a phone call to someone like Briley before I done anything.

 

[Ian]

I have two L.C. Smith doubles, of later manufacture. According to my books, they quit making the Damascus barrels in 1919. The markings may help here, if it is marked "L. C. Smith, Syracuse, N.Y. it was made in the 1880s. If marked "Hunter Arms Co." that would be 1890-1912. If marked "Hunter Arms Co., Inc" it would be 1913-1919. I found a note about the unique action lock that all the models used, apparently it is a self-compensating system which adjusts for wear and the guns were well-known for never shooting loose.

 

[KeithB]

Wow, I appreciate all the input! As soon as my knee feels a little better I will go downstairs to my gun room and take a closer look at the old girl. I also have two Hunter arms doubles, in 20 and 12 gauge. My father let me buy the 20 gauge when I was barely a teenager from a neighbor, picked up the 12 gauge at a gun show some years later. The 20 made a superb rabbit, quail, and pheasant gun. I have shot traps with the 12.

With all due respect Ian, I'm still leaning towards full length liners versus chamber inserts. I'm sure you're correct in saying that the pressure will drop rapidly after the shot column exits the chamber, but the initial momentary pressure still concerns me. (Would be interesting to instrument a 10 gauge tube with a 20 gauge liner and check the pressure/time curve at the chamber exit.)

I'm kind of a conservative, belt and suspenders guy when it comes to playing with things that can go bad faster than I can run away, and the older I get the slower I run.

 

[Brad]

I'm kind of a conservative, belt and suspenders guy when it comes to playing with things that can go bad faster than I can run away, and the older I get the slower I run.

That may be one of the best quotes I've seen in a long time

 

[gman]

I would call up the folks at Briley and tell them what you are interested in and can it be done.

 

[KeithB]

fiver, gman, that sounds like good advice.

300BLK, at less than $21 for a barrel, it might be worth buying just to see what could be done. I've got a fairly complete small machine shop at my disposal.

I've often thought about taking a double barrel with a strong action and damaged barrels and cutting off the barrels, then boring out the chambers and sweating in new tubes of a different gauge/caliber. In this case liners or inserts seem to make more sense.

 

[fiver]

I don't know if they done the Damascus barrels the same or not.
but most barrels are just that, barrels.
they are slip fit over the mono block and silver soldered in place.
many company's will put a little scroll work over that area to hide the little seam.

many of the sub-gauge tubes are stand alone type units.
they are centered with 0-rings and kind of float in the barrel and are 'held' in place at both ends.

 

[KeithB]

many of the sub-gauge tubes are stand alone type units.
they are centered with 0-rings and kind of float in the barrel and are 'held' in place at both ends.

That's what I kind of had in mind.

 

[KeithB]

The gun in question has had the barrels cut short because of muzzle damage. It now looks more like a coach gun than a duck gun. The only intended use for it would be home protection. It is an awesome, intimidating looking piece from the front. The hammers make a really solid click when they're cocked. Rapid reloading is not an issue. Even reduced to 20 gauge at across-the-room distances the damage done by an ounce of #4s is substantial. Hope it would never be used, but...

 

[300BLK]

info on L C Smith barrel types
http://www.lcsmith.org/faq/barrels.html

I think the barrels are stronger than you might think unless the bores are pitted. Initial, momentary pressure will be the same whether you use chamber inserts or full length liners. Pressure will drop more rapidly when exiting a 20ga chamber adaptor into a 10ga bore than it will with full length 20ga liners.

BTW, the highest pressure I see listed for 20ga loads in my Lyman manual is 12Kpsi.

 

[freebullet]

I love the smell of burning black powder in the morning.

 

[Pistolero]

Actually, with a full length liner, there will be no pressure loads on the barrel, assuming that the liner is capable of supporting a shotshell
firing and that it is supported on 0-rings. The liner will bulge slightly, probably under 0.001 radially under pressure, and with an o-ring, that will
not even contact the bbl most of the way. A smaller shell head means that for the same pressure, much less thrust load for the
action to take. A 20 ga shell has a diam of 0.73", 12 ga diam of 0.85". The area ratio shows that for the same shell pressure, the
20 ga will push 73.8% as much as the 12 ga. That gives a pretty good safety margin.
I tend to go with Ian, one of the short inserts will drop the pressures, but it is your gun and your decision. Briley full length tube
set is $650. Chamber inserts are far less. Appaently patterns with the 6" long type are pretty good.

Ian or Brad could run the actual pressures along the bbl for a few assumed loads in their
software. Probably find that by 4 to 6" pressure is as low as peak BP pressures.

Bill

 

[quicksylver]

Been using Briley sub gauge tubes for thirty some odd years they are great...just stay away from Green Dot...weakest part of twist barrels is at the tip of the fore arm...breaches are heavy because black powder is more of an explosive ..they thin out from there ..smokeless powder generates it's higher pressures mid barrel..weakest spot for twist barrels.

Briley sub Guage tubes brought back the use of many of those old guns...just kind of ruined their balance though.