Idea - variable length barrels

[ahhshoot]

I know Frank from Bartlein visits this site-maybe he can help.. has this been done before?

Variable length barrel-hear me out...

Cut a barrel as you normally would... 33" blank or whatever. But at a certain point, cut it again and thread both pieces.

Shooting ELR? no problem, let me screw on my barrel extension, I get another 200 FPS.

Backpacking? Meh, let me take this extra weight off and throw the cap on and run it at 18".

Or, cut a few times for short, medium and long.

Could marvels of modern machining pull this off while keeping the bore smooth enough to not shred a jacket? If we can make suppressors and muzzle brakes in completely different states and screw them together, why couldn't we cut one piece of stock and make it work in this fashion?

If I start seeing these things pop up on the Hide I will be coming after you for royalties!!!

thoughts...

 

[strike33]

the muzzle brakes and suppressors don't have to deal with the friction of the bullet, as you know there's no contact. its an interesting concept but I wouldn't trust it with my face behind the gun

 

[ahhshoot]

the muzzle brakes and suppressors don't have to deal with the friction of the bullet, as you know there's no contact. its an interesting concept but I wouldn't trust it with my face behind the gun

I feel the same way about bullpups... But really, some of the machining is done so well these days... Maybe the best way to 'attempt' it would be to make the blank, cut it and thread it, check run out, then cut the bore and rifling with it all screwed and torqued together. Then very carefully test fire it with a machine haha. But the payoff if it worked out would be tremendous.

 

[Maelstrom]

My concern would be the rifling in the barrel not matching up exactly every time you screw the barrel pieces back together. I may be wrong but I would think that would cause major problems.

 

[ahhshoot]

My concern would be the rifling in the barrel not matching up exactly every time you screw the barrel pieces back together. I may be wrong but I would think that would cause major problems.

I would have the same concerns. To mitigate that, I feel cutting the bore and rifling after the blank and threading was done, with all pieces assembled, would help. In addition you could add a notch that would line up when the rifling was in tact. Im not saying it is a sure thing and I appreciate the ideas. Im just thinking that if try it out if I had the tools and testing equipment to see if it was feasible. With technology new ideas can be turned into realities and make the world a better place

 

[biffj]

My concern would be the rifling in the barrel not matching up exactly every time you screw the barrel pieces back together. I may be wrong but I would think that would cause major problems.

Having seen a number of barrels made in sections where the rifling doesn't line up at all I don't think it makes as much difference as you might expect. Engraving a bullet at speed vs from a full stop at firing requires a lot less energy so pressure spikes would not be an issue. A number of guns out there (mostly military) use a separate chamber threaded into or onto the rifled barrel so joints if well designed , aren't a safety issue. I'd not have any issues shooting a barrel that was threaded together as the original poster suggested. I'm not sure how accuracy would be affected but I'm guessing probably wouldn't be great. For my money I'd swap the whole barrel for length changes if that were an issue. Change barrels are much more common now and techniques are out there to do it with extreme accuracy. The DT SRS is a good example. You do end up with a heavier setup as full length barrels are heavier than short sections but you're sure of accuracy....or more sure.

Frank

 

[PinesAndProjectiles]

What about a "quick disconnect" barrel? Something that uses a can lock mechanism to join the barrel with the action. Yeah, you'd have to buy multiple barrels do not as convenient, but it's harder to lose a barrel than a piece of barrel.

 

[Walsh]

What if you didn't rifle the "extensions", but make it a smoothbore. Accuracy would be minimal as we all know the accuracy from a short barrel is technically better than a longer barrel. The only problem I could see from this would be a tight gas seal, which could affect velocity. I'm sure a more intelligent one could figure out a way around this.

Interesting concept if you could do it for even the price of another barrel. For us that do not have a switch barrel action (190A3), this could be nice to have.

 

[Rhyno]

I have two immediate questions that came to mind.

1, what if the bore of the barrel was off center.

2. What do you do about the crown? Carbon and heat, as well as brass shavings could collect in the crown and damage it In the area where you screw on the second barrel.

 

[MitchAlsup]

A) can it be done--yes

B) but the machining precision to pull it off would be "really hard". You are going to have to line up the groves of the short barrel and the barrel extension to really tight tolerances.

 

[ahhshoot]

Having seen a number of barrels made in sections where the rifling doesn't line up at all I don't think it makes as much difference as you might expect. Engraving a bullet at speed vs from a full stop at firing requires a lot less energy so pressure spikes would not be an issue. A number of guns out there (mostly military) use a separate chamber threaded into or onto the rifled barrel so joints if well designed , aren't a safety issue. I'd not have any issues shooting a barrel that was threaded together as the original poster suggested. I'm not sure how accuracy would be affected but I'm guessing probably wouldn't be great. For my money I'd swap the whole barrel for length changes if that were an issue. Change barrels are much more common now and techniques are out there to do it with extreme accuracy. The DT SRS is a good example. You do end up with a heavier setup as full length barrels are heavier than short sections but you're sure of accuracy....or more sure.

Frank

This makes sense. The bullet is already moving, it would be similar to the same reason more freebore mitigates pressure spikes. I agree that if a bullet can slam into the lands from freebore there's no reason a bullet can't slam into more lands, even if they were offset from the original lands when its' already being pushed even faster. As far as the 'quick detach' that was mentioned by another, I just don't like that idea for one reason and that is over time those devices almost always seem to wear out and the tolerances required to pull this off wouldn't be easy to retain with the QD; threads for the most part don't wear out, and if you are threading to the same place every time via a mark on the barrel to line each piece up the same way it was lined up when the bore and rifilng were cut, you should have a near perfect match. After a few shots the copper/carbon would fill in any microscopic grooves as they do in a new barrel being broken in and accuracy would likely still be very good. I wish I had the resources to make this happen, that's part of the reason for me posting here hoping one of the big boys will see it and try it out. I think it can be done and it wouldn't be as difficult as some are making it seem, and I really don't think accuracy would suffer much-maybe not benchrest results but I believe 1/2 MOA consistently would not be out of question.

 

[ahhshoot]

I have two immediate questions that came to mind.

1, what if the bore of the barrel was off center.

2. What do you do about the crown? Carbon and heat, as well as brass shavings could collect in the crown and damage it In the area where you screw on the second barrel.

The crown came to mind on my end as well. The only way to make it feasible would be to cut a reverse crown in the extension, so they matched up when screwed together. As far as the bore being off center, I don't think that would matter much because remember we are first cutting the blank as a solid piece of metal with no bore yet, cutting all the extensions and threading each piece before the bore and rifling are cut. We would take all threaded pieces, tighten them to torque specs, engrave in the barrel a notch that should line up when proper torque has been achieved, then cut the bore and rifling. This way, even if disassembled, the user can re-assemble by simply torquing the extensions until the engraving in the two pieces line up, thereby bringing the rifling to the same position it was in when cut as one piece. So, having the bore off center really wouldn't have any more of an effect on this design than it would on a traditional barrel.

 

[condomboy]

my first thought was matching rifling.

My second thought was I'd be worried about temperature differential between the pieces and trying to thread on or off

If you just want a little extra speed, maybe carry some extra ammo that's loaded a little hotter to give you that extra speed...?

 

[PinesAndProjectiles]

The crown came to mind on my end as well. The only way to make it feasible would be to cut a reverse crown in the extension, so they matched up when screwed together. As far as the bore being off center, I don't think that would matter much because remember we are first cutting the blank as a solid piece of metal with no bore yet, cutting all the extensions and threading each piece before the bore and rifling are cut. We would take all threaded pieces, tighten them to torque specs, engrave in the barrel a notch that should line up when proper torque has been achieved, then cut the bore and rifling. This way, even if disassembled, the user can re-assemble by simply torquing the extensions until the engraving in the two pieces line up, thereby bringing the rifling to the same position it was in when cut as one piece. So, having the bore off center really wouldn't have any more of an effect on this design than it would on a traditional barrel.

Yes, but in order to cut the barrel, you would need to remove part of the rifling when you cut it. If you cut it with a .125" wide cut off tool, theoretically, you could insert .125" of shim but I doubt it would be that easy.

 

[ahhshoot]

Yes, but in order to cut the barrel, you would need to remove part of the rifling when you cut it. If you cut it with a .125" wide cut off tool, theoretically, you could insert .125" of shim but I doubt it would be that easy.

Why? If the cuts and threading and crowns/reverse crowns are all made and fit together as should BEFORE the barrel is bored and rifled, why would we need to remove any of the rifling? It would just be bored and rifled as any other barrel would, except in this case you would have three pieces threaded and torqued together. Boring/rifling and then cutting wouldn't work obviously, the cutting and threading would all need to be done with one solid piece and that would need to work before any further machining would be done.

 

[PinesAndProjectiles]

If you take a barrel that is say 20" long, and you cut it in half, you no longer have two 10" pieces. You are missing the amount of material that was removed while making the cut.

 

[ahhshoot]

If you take a barrel that is say 20" long, and you cut it in half, you no longer have two 10" pieces. You are missing the amount of material that was removed while making the cut.

Dude are you reading what I'm writing? lol. You take the 20" piece BEFORE the rifling is cut and cut your two 10" pieces, thread them, and make sure they fit without excessive runout and have a good seal between the two pieces. Then, screw them together to make it a 20" piece again, torque it to whatever spec is deemed acceptable, THEN cut the bore and rifling. No additional cuts would be needed.

 

[PinesAndProjectiles]

Well then, that makes much more sense.

 

[ahhshoot]

Well then, that makes much more sense.

Haha. Yeah it would be tough to do it the other way around

 

[Frank Green]

I know Frank from Bartlein visits this site-maybe he can help.. has this been done before?

Variable length barrel-hear me out...

Cut a barrel as you normally would... 33" blank or whatever. But at a certain point, cut it again and thread both pieces.

Shooting ELR? no problem, let me screw on my barrel extension, I get another 200 FPS.

Backpacking? Meh, let me take this extra weight off and throw the cap on and run it at 18".

Or, cut a few times for short, medium and long.

Could marvels of modern machining pull this off while keeping the bore smooth enough to not shred a jacket? If we can make suppressors and muzzle brakes in completely different states and screw them together, why couldn't we cut one piece of stock and make it work in this fashion?

If I start seeing these things pop up on the Hide I will be coming after you for royalties!!!

thoughts...

I will say stuff like this has been done but where a test barrel was needed and they needed a barrel say 60" long but they were not concerned with accuracy etc...it was mostly for velocity testing or other types of testing.

In cases like the M2 .50bmg machine gun barrels there is a chamber insert that is rifled for x amount of distance. They use special equipment to align up the rifling to get it as close as they can....again I say as close as they can. Keep in mind this is a machine gun barrel. It's designed to sling lead at airplanes, ground targets, trucks etc...it's not a 1/2moa gun and neither is the ammo. They do have a problem though and it is with the insert and it's made at one time and the barrels are made at another time and with different tooling as well as possibly by different manufacturers. The grooves have a +.010" tolerance.

Something like this is done with false muzzle barrels. Barrels used on Schuetzenfest/blackpowder type rifles where the load the bullet from the muzzle. This keeps the muzzles crown from getting damaged also besides the argument that a lead bullet being loaded from the muzzle is more accurate than a breech seated bullet or a bullet loaded into a case blah blah blah. The barrel blank gets drilled and contoured etc...then a portion of the muzzle is cut off (say about 3") but before you cut it off you have to drill 3 or 4 dowel pin holes. When you cut off the muzzle end you install the dowel pins into the false muzzle. The left over holes in the barrel itself will align up with the dowel pins in the false muzzle so it can only go on one way/time up. After you cut the piece off and do the dowel pin work then you attach the false muzzle and then you ream, prelap, rifle and finish lap the barrel with the false muzzle being held in place. This way the rifling of the false muzzle lines up perfectly with the muzzle/crown end of the barrel.

Just google false muzzle and you will see what I'm talking about.....

Making a barrel like this is more labor intensive and costly.

Now as I see it.....trying to do it with a hi power rifle round and jacketed bullets etc....could it be done? I'll say yes but you have obstacles to overcome and questions/concerns about safety as well. If you take it a part and put it back together and don't line it up correctly (lets say the two pieces are threaded like has been mentioned) the rifling won't line up. I see big problems with bullet failure (bullets coming a part/shredding jackets etc....), fouling issues. I cannot even start to think about pressure concerns etc..as that will vary with where the joint is made etc...

Later for now....Frank
Bartlein Barrels

 

[ahhshoot]

I will say stuff like this has been done but where a test barrel was needed and they needed a barrel say 60" long but they were not concerned with accuracy etc...it was mostly for velocity testing or other types of testing.

In cases like the M2 .50bmg machine gun barrels there is a chamber insert that is rifled for x amount of distance. They use special equipment to align up the rifling to get it as close as they can....again I say as close as they can. Keep in mind this is a machine gun barrel. It's designed to sling lead at airplanes, ground targets, trucks etc...it's not a 1/2moa gun and neither is the ammo. They do have a problem though and it is with the insert and it's made at one time and the barrels are made at another time and with different tooling as well as possibly by different manufacturers. The grooves have a +.010" tolerance.

Something like this is done with false muzzle barrels. Barrels used on Schuetzenfest/blackpowder type rifles where the load the bullet from the muzzle. This keeps the muzzles crown from getting damaged also besides the argument that a lead bullet being loaded from the muzzle is more accurate than a breech seated bullet or a bullet loaded into a case blah blah blah. The barrel blank gets drilled and contoured etc...then a portion of the muzzle is cut off (say about 3") but before you cut it off you have to drill 3 or 4 dowel pin holes. When you cut off the muzzle end you install the dowel pins into the false muzzle. The left over holes in the barrel itself will align up with the dowel pins in the false muzzle so it can only go on one way/time up. After you cut the piece off and do the dowel pin work then you attach the false muzzle and then you ream, prelap, rifle and finish lap the barrel with the false muzzle being held in place. This way the rifling of the false muzzle lines up perfectly with the muzzle/crown end of the barrel.

Just google false muzzle and you will see what I'm talking about.....

Making a barrel like this is more labor intensive and costly.

Now as I see it.....trying to do it with a hi power rifle round and jacketed bullets etc....could it be done? I'll say yes but you have obstacles to overcome and questions/concerns about safety as well. If you take it a part and put it back together and don't line it up correctly (lets say the two pieces are threaded like has been mentioned) the rifling won't line up. I see big problems with bullet failure (bullets coming a part/shredding jackets etc....), fouling issues. I cannot even start to think about pressure concerns etc..as that will vary with where the joint is made etc...

Later for now....Frank
Bartlein Barrels

Frank,

Thanks for the insight and input. My idea for helping with the alignment of the rifling after disassembly and re-assembly was to wait until all the cuts in the barrel were complete and able to be threaded/fitted precisely before the bore/rifling were cut. So if we took at blank say 30" with no bore or rifling cut yet, and cut the barrel once at 24", and again at 16", cut our crown and a 'reverse' or 'inverted' crown for each add-on piece, we would have one solid piece of metal that could be screwed and torqued together. No bore yet. Next we could screw all pieces back together and torque to a specified weight, and score a line across each junction as a reference for when the junctions are assembled again in the future. This would provide a torque reference and naturally after the bore is cut and rifled, would allow for the rifling to align exactly as when it was cut. Well, as exact as possible anyway. So next with all three pieces torqued together we throw it on the machine and cut the bore and rifling as if we were doing one solid barrel. As far as production cost and time, I can imagine something like this would come at a premium if it were to work in a precision rifle simply due to all the tooling and labor that would be involved.

I have owned and shot a few of your barrels Frank, and I know if anyone could pull this off it would be you guys. Whether it would be worth it to invest in the R&D you would know far better than I would. But hell, it would make one cool project.

 

[Frank Green]

Frank,

Thanks for the insight and input. My idea for helping with the alignment of the rifling after disassembly and re-assembly was to wait until all the cuts in the barrel were complete and able to be threaded/fitted precisely before the bore/rifling were cut. So if we took at blank say 30" with no bore or rifling cut yet, and cut the barrel once at 24", and again at 16", cut our crown and a 'reverse' or 'inverted' crown for each add-on piece, we would have one solid piece of metal that could be screwed and torqued together. No bore yet. Next we could screw all pieces back together and torque to a specified weight, and score a line across each junction as a reference for when the junctions are assembled again in the future. This would provide a torque reference and naturally after the bore is cut and rifled, would allow for the rifling to align exactly as when it was cut. Well, as exact as possible anyway. So next with all three pieces torqued together we throw it on the machine and cut the bore and rifling as if we were doing one solid barrel. As far as production cost and time, I can imagine something like this would come at a premium if it were to work in a precision rifle simply due to all the tooling and labor that would be involved.

I have owned and shot a few of your barrels Frank, and I know if anyone could pull this off it would be you guys. Whether it would be worth it to invest in the R&D you would know far better than I would. But hell, it would make one cool project.

I see problems that are going to be difficult to over come. First when you cut the barrel into sections I wouldn't crown that muzzle area. I would leave it flat. No chamfer, recess crown, 11 degree etc...why? If you put a chamfer on it like doing crown work the gas is going to want to go somewhere etc...it most likely cause some abnormal erosion in that area and could get worse the more you shoot it. If you look at a vintage false muzzle when the false muzzle is removed before shooting there is no other crown type work done to the muzzle. Just me thinking out loud here.

Also putting a timing mark and trying to align up the sections etc...will be difficult at best even using a torque wrench. If the threads are dry, have any type of oil on them etc...will effect the torque etc...and trying to eyeball and alignment/timing mark.....? There will be no room for any error. Any error at all and the rifling will not line up. No way around it. If that happens again I see accuracy problems and bullet failure problems. I'm not saying I have all the answers but as of right now I see nothing but problems.

Later, Frank
Bartlein Barrels

 

[dmike]

It's an interesting idea. Wonder if there's a way to taper the rifling (width and/or depth) at the beginning of the section so it can tolerate minor timing deviations like Frank is describing

 

[ahhshoot]

It's an interesting idea. Wonder if there's a way to taper the rifling (width and/or depth) at the beginning of the section so it can tolerate minor timing deviations like Frank is describing

Are you suggesting 'thinning' the lands at the point where the bullet would pass the junction between each extension? That is a great idea... it would allow for at least a deviation amount in the neighborhood of whatever the distance across the initial lands-the width of the new lands at bullet entry... and would allow the bullet to gradually follow the track of the new lands.

Obviously we've got some challenges here. I'm not saying that if we made 100 of these things and 100 traditional barrels, and averaged the accuracy from each 100, that the variable length would be as accurate. But that doesn't mean that if they were made correctly and used correctly, that they couldn't be at least as accurate as a good traditional barrel and in some cases more-so. Frank is right about the gases naturally escaping if there was an angled crown, it might be better to reduce the crown angle or make no angle at all.. Then again how many shots would it take for the copper to foul this very miniscule space thereby stopping the gas escape issue? Making 'hotter' loads wouldn't work the same, you are still limited by how much powder you can efficiently burn in a given length of bore.

 

[dmike]

Are you suggesting 'thinning' the lands at the point where the bullet would pass the junction between each extension? That is a great idea... it would allow for at least a deviation amount in the neighborhood of whatever the distance across the initial lands-the width of the new lands at bullet entry... and would allow the bullet to gradually follow the track of the new lands.

Yeah thinning and/or tapering so it could ease into the next section at the same general twist rate. It might actually slow it down though...I'm sure you'd want completely different loads depending on which configuration you were running