MDT builds 6 foot barrel for .308

[davidjoe]

New on YouTube. Connecting two .30 caliber barrels, for a six foot long .308 barrel, MDT tests factory match ammo and then cuts down the barrel(s), progressively.

The gun’s velocity is never higher than at the longest length, it progressively decreases from near(ish) magnum velocity, and it actually shot well considering the bullet has to leave one barrel and enter a second.

This is remarkable in not only pulling off the junction, but also surprising the shooting public about the effect of extra barrel length. Too bad that gun is gone now!

Link: World's Longest Rifle Barrel Velocity Test by MDT

 

[ronsatspokane]

Link?

Forum Boss: I just embedded the video I think David referenced.

Here is the link you can bookmark:

MDT Ultra-Long Rifle Barrel Velocity Test

 

[davidjoe]

Thanks guys!!

 

[Ray123]

Interesting experiment, but I found no surprises. About what I would have expected...sounds like some wild off the wall experiment I'd try... except this would be too expensive for the expected outcome...I'm glad they did it. Thanks for sharing.

 

[rijndael]

When they mated the two barrels, I wonder if they indexed the lands/grooves, so they were somewhat aligned and had a smoother transition.

 

[whatsupdoc]

When they mated the two barrels, I wonder if they indexed the lands/grooves, so they were somewhat aligned and had a smoother transition.

According to the video they did time the rifling where the the barrels are joined.

 

[M-61]

The best by far was Jerry Bull.
He thought so far out there that no box existed.
A real tragedy his politics resulted in his being assassinated. He really just cared about ballistics.
The politics were the money source.
One gun had a 156 foot long barrel

 

[rijndael]

According to the video they did time the rifling where the the barrels are joined.

Thx. I must have missed that part ... I was multitasking.

 

[ronsatspokane]

That does not surprise me. The question would be, how much interrior volume would be needed to dissipate the pressure to the point that the friction of the bullet against the barrel overcame the pressure pushing the bullet forward. I think it would take a lot.

 

[davidjoe]

Friction negating any velocity gain is usually thought or said to occur in a .308 at under about 32 inches, with something like the range of 29-32 inches being relatively flat. I’ve been doubtful about that myself with using .22 LR match rifles burning a mere 2.0 grains of powder or less, as a frame of reference, but who was ever going to be able to test it.

His muzzle at full length still vented forcefully. My understanding is that powder expands to roughly 300 times its size in gaseous form, and a .308 is not exactly a huge case, but how strong the later stages of expansion is, when friction is also working all the time, suggests the max length remains to be seen.

 

[Straightshooter1]

New on YouTube. Connecting two .30 caliber barrels, for a six foot long .308 barrel, MDT tests factory match ammo and then cuts down the barrel(s), progressively.

The gun’s velocity is never higher than at the longest length, it progressively decreases from near(ish) magnum velocity, and it actually shot well considering the bullet has to leave one barrel and enter a second.

This is remarkable in not only pulling off the junction, but also surprising the shooting public about the effect of extra barrel length. Too bad that gun is gone now!

Link: World's Longest Rifle Barrel Velocity Test by MDT

Really long barrels are nothing new.

 

[Dusty Stevens]

They found out why rimfire match barrels are longer than normal

 

[RegionRat]

He did a torture test not long ago that was also fun to watch.

It is interesting data and might be fun to try and map it into QL or GRT and see what backs out.

 

[Ranger188]

Does this mean everyone is going to run 40 inch barrels? lol
Guess how much barrels would cost and weigh.
How about the accuracy. Their has to be more barrel harmonics
to deal with.

 

[Emmett Dibble]

I was honestly surprised they were still getting roughly MOA out of a 6’ long barrel… I would have thought harmonics or even keeping the thing straight under it’s own weight would have started to be a problem. (The velocity surprised me too)

 

[davidjoe]

Does this mean everyone is going to run 40 inch barrels? lol
Guess how much barrels would cost and weigh.
How about the accuracy. Their has to be more barrel harmonics
to deal with.

No one has to worry anymore about slowing down bullets . Cost for extra length barrels is a real hurdle, there is usually a steep increase, and then after about 32”, an even steeper per inch increase, and then soon there is wall they just won’t exceed. But yes to at least 40 there is real velocity gain, and that’s not even considering the slowest burning powders and longest cases.

 

[hpshooter]

The best by far was Jerry Bull.
He thought so far out there that no box existed.
A real tragedy his politics resulted in his being assassinated. He really just cared about ballistics.
The politics were the money source.
One gun had a 156 foot long barrel

The Israels did give him a choice.
The barrel sections for the Iranian "Super Gun' were forged at a forge shop in England. A couple of us were visiting an English Ductile iron pipe foundry and the fellow transporting us pointed the forge shop out to us.


Bull was an interesting fellow.

 

[Papa Charlie]

Very interesting. I would not have expected the speed to somewhat stabilize between 44" and 69".

I run a 30" barrel on my FTR rifle shooting .308. My muzzle velocity is right at 2731 fps. I had to taper my barrel to 0.950" at the muzzle to make weight. My next barrel I would like to go a little longer but I want to add a Tuner and weight is going to be a real issue.

Thanks for sharing this. Very interesting.

 

[ronsatspokane]

I was honestly surprised they were still getting roughly MOA out of a 6’ long barrel… I would have thought harmonics or even keeping the thing straight under it’s own weight would have started to be a problem. (The velocity surprised me too)

I would think that issues associated with harmonics would decrease as the mass increased. At a given charge, a lighter mass will be moved more than a heavier mass will. It would take a heavier charge to move the heavier mass an equal amount. At some point though keeping the barrel supported under its own weight would become a problem. Regardless of the contour, a barrel is really just a "relatively" stiff noodle.

 

[M-61]

The Israels did give him a choice.
The barrel sections for the Iranian "Super Gun' were forged at a forge shop in England. A couple of us were visiting an English Ductile iron pipe foundry and the fellow transporting us pointed the forge shop out to us.


Bull was an interesting fellow.

Made allegedly for BP and called oil pipe.
Some of Bull’s designs gave new life to many artillery guns.
I would call him ‘fascinating’ at the very least.
Similar in some ways to Werner von Braun in so much as it was always the project that consumed him, and not who paid the bill nor their motives.