Cutting The World's Longest Rifle To Find The Perfect Barrel Length 

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Joining two barrels together so that the rifling matches perfectly at the correct torque setting is NOT a trivial job. Very well done to the machining guys

Love the folding stock at 01:41 for better storage LOL 😂

6:15 this shift in point of impact is because of the barrel crown. when you cut the barrel crudely like that the crown isn't going to be perfect so it throws the shot off.

There are very few videos on RU-vid that I wish were longer and more in depth. But I felt myself wanting more data, group sizes, shot placements, etc. Great video and cool concept.

Appreciate all the time and effort you guys spend doing these crazy experiments most of us can only dream of!

Hey folks, I did the same thing for 45acp . My results mimic yours except we did see a slow down. This is likely due to scale. Turns out even at that length, for that caliber you were still too short for the friction to slow the bullet. Theoretically as barrel length increases we expect the velocity to climb, then stabilize for a good bit before declining. Good stuff

Very interesting. Reading the chart, the sweet spot without the rifle being ungainly is about 24.5 inches - exactly where CZ has their 550 Varmint barrel in .308 You have to go approximately 40 inches to get any practical increase in velocity, using the same ammo. Perhaps CZ knows what they're doing. ; )

This is awesome, great job. And kudos for teaming up with Bob Jury, he’s a great guy. I’d love to see this test done again with a cartridge with a lot more powder behind it, like a 300 Norma, 30 Nosler, or 30-378 Wby. Would be really curious to see what the graph looks like when there’s a lot more ooompf behind it than a 308 Win. Totally understand why you chose the 308, though. Far more relevant test to what larger numbers of shooters are actually shooting.

1:41 - The irony of a folding stock on a gun with a 6 foot barrel. lol

I would venture to guess that the left-right deviation you saw as you cut it might have been due to the crown not being perfectly square with a bandsaw finish. I have seen rifles with less than ideal crowns do some wild stuff. Great video!

The results would have looked much different if a much slower powder had been used. The factory 308 ammo likely uses IMR 4064 or RL15 or something in that burn rate. If you handloaded ammo and used a much slower burning powder, like RL22 or Retumbo, then the slower burn would perform much better in the super long barrel, as the pressure would stay higher for longer, thereby increasing the acceleration time for the bullet.

Died laughing at the 3 bipods and then the immediate cut to him folding the stock to stow it 😂

The bullet groups shifting left and right each time you cut off more barrel is from the crown not being perpendicular to the bore

Now the question remains, how ludicrously long does the barrel have to be for friction to begin to have a noticeably negative effect on performance? Obviously you don't gain much after 40 inches, but what does it take to actively hinder performance?

These experiments are fun to watch.

You tailor the handload to the barrel length available, picking a slower powder for a longer barrel. The same load will perform differently in a 20" vs a 30" barrel. 9mm handgun vs 9mm carbine is a good example how different the same calibre can perform. If handloaded properly.

Hey MDT, I love how you put out these awesome videos and actually prove what would happen if. Can you please make a video proving if there are any accuracy differences between a prefit shouldered barrel and a barrel installed with a barrel nut. Use the same manufacture, same barrel profile and twist rate. Make it a five shot group instead of a three shot group. And shoot out a little further to really show if there is any difference like 300 metres or 500 metres. BTW have your XRS chassis and love it. Please make one for a Remington 700 long action footprint. $$$ waiting ;)

I'm wondering if custom loads with a VERY slow burning powder would have performed better in the longer barrels. Factory ammo isn't optimized for a 40+ inch barrel.

The production value on these is insanely good.

I'd love to see how different powders, play into this experiment.

With a 308 win. I think 24-26 inch max, beyond that the amount of barrel needed for an increase is not worth the weight , and length of the rifle, I know on a 243 Win. 26 inches is the sweet spot. beyond that my fps. got slower. I think with your test you had to go to 45 inches just to get to a plateau. Now had that been a 50 BMG or a 30-378 Wolfe then you would have seen a serious increase, but only to the point of how slow burning your powder/case capacity. Great Show.

Buddy, 6 feet long? That barrely enough

Precision rifle Punt gun. Great data, but to achieve the fastest speed from a cartage you'll need at least 44" barrel... looks like

Personally I am a fan of 15.9 inch barrels.

I've been using your stuff for years, and it's worth it. As a former barrel maker myself, it's nice to see how you guys actuality understand what's going on. And the data to back it up.

With those results, I would go with 36.5" for maximum fps.

being a physics guy... I think whats happening here is that the powder burn/ barrel pressure starts leveling off at around the 46 inch mark. one has to remember that the more barrel that the bullet travels through, the bearing surface of the bullet is also wearing away so the resistance is also dropping more and more as it travels down towards the muzzle.

Really love that the MDT team put so much back in to the sport not only in R&D, Sponsorship, but like this vid testing thought and ideas that shooters have Top work team.

I would have thought the extra long barrel would have slowed down the bullet. Thinking that after all the powder was gone that the bullet continuing down the barrel and making contact would cause drag. But I guess even after the powder is burned the gas pressure continues to accelerate the bullet down the barrel since the gas has no where else to go.

Interesting test, I bet you spent the better part of an entire day performing this cut-down barrel test!

A gym membership is only $10 a month...

Got so many people saying 30 inches in a 308 is too long. Even 40 inches works better with Federal Gold Medal Match.

Would have loved to see this test with something like a 300 RUM or 30-378 Weatherby and very slow burning powder like Retumbo or Ramshot Magnum.

Id just love to have all the brass

Great video. Quite interesting. I suspect if you went with larger magnum cartridges with slower burning powders you would see it speed up even more.

very nice experiment. however to unleash the benefit of the long barrel different gunpowder must be used. The longer the barrel the more slowly burning propellant should be. I also curious what kind of tool has been used to cut the barrel.

Doing the Lord’s science!!! Keep up the great stuff!!! This needs to be the “What if” series to keep great work like this going!!!

I've never seen an instance where you lose a significant amount of velocity from excessive barrel. VSO even did testing with a ridiculously long barrel on a 45acp and it mirrors the curve you plotted.

I always wanted a 100 yard barrel so I could hit 100 yard targets easier!

This type of testing has already been tested by militaries and there's already data available about the limits of positive gains in velocity and energy delivery in correlation to barrel length. There's also information about barrel twist ratio and how it correlates downrange with varying barrel lengths but I don't know much about that information. This test makes me wonder how much your rough crowning is affecting both your speeds and impact points.

The folding stock 🤣

good thing it has a folding stock, it'd be too cumbersome otherwise

You missed a great opportunity to check the barrel harmonic's effect on accuracy for each length. Without that, any study of the "perfect barrel length" is incomplete.

My buddies just made fun of me and my Montana musket saying somebody made something bigger. I built an AR-10 rifle length buffer Magpul rifle stock 24-in free float handguard 26-in McGowan barrel with a hybrid 46 complete with anchor break hanging off the end of it. This here rifle that you built I do have to concede is bigger lol.

mobile artillery

I’d like to see what happens with a larger volume cartridge. Something like a 300 RUM or 300 Norma. It would be interesting to see how the longer barrel effects large volumes of slow burning powder.

Amazing that 24" gave higher velocity then the 26". And higher up to roughly 30".

Bob made the 22 inch long / 1:8" twist Stainless varmint barrel on my LH Savage 243win that sits in an LSS Gen 1 chassis ! Need to get him to thread and label my barrel though... 🧐

The real question is can it CQB ?

The real key to this test is the factory powder used, which is designed for much shorter barrels. If you used reloads with a slower powder, I think you'd have seen a much greater increase in velocity in the longer barrel

Ok, who on the market is making a 45" barrel? Cause I NEEED it. 🤣🤣🤣🤣

It's so funny looking 😂 same energy as joker pulling out that really long revolver in the old Batman movie

I want to see this but with a chambering in 22 fury 22 caliber pushing 80,000 foot pounds of pressure I bet you could get some really but naked speeds out of that

Most rifle barrels burn their powders within 28" of length so, the extra length of 6 feet allowed the powder complete burning giving the bullet extra speed.

I was expecting 30-378 or 300 RUM or something, but 308 seems like 26 inches would be tops.

No quick recrown? That explains the viariation. Crowning is inder appreciated.

Looks like 45” is the point where the slope of the line changes. I’m going to stick with 20” though. Just too handy.

This is easily now going to be one of my favorite videos to show friends and family. We hunt a lot, my father's choice has been .30-06 for decades, mine has always been .308 WIN. You dedicated a whole video to an idea of "why shouldn't we" rather than "why should we". Interesting as heck, now I'm left wondering what sort of difference you'd find with newer high performance type cartridges. Hint hint, wink wink, cough cough.

I appreciate the folding stock for maneuverability and ease of carrying

What I call a fishing pole, you name it a rifle🤣

This looks like it would be an April Fools joke. Great video though. With similar studies done on 22LR and a velocity around 16", I've always wondered just how long of a barrel is needed to find max velocity in larger calibers. I'd be interested to see this repeated with 6.5 Creedmoor and 6 Creedmoor for ... science, yes for science! 😁

boooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooolt action

7:01 for full graph. Velocity increase is pretty constant until around 44 inches, after which it pretty much stops. Weird that there was such a spike at 24 inches though.

I’m 4 years into my physics bachelors and I tried to make a 150 psi air gun that was fully optimized for shooting a 15 grams projectile. When I did the math for the optimal barrel length I was surprised that it turned out to be roughly 2 meters. At first I thought I miscalculated something, but after going through it with an engineer and a mathematician friends of mine, turns out I was right. I didn’t end up building it due to legal reasons lol but I’m glad to see this video. Thanks for making something I couldn’t make myself.

Lots of work! Thanks for putting it all together 👍🇨🇦

So 44 inches optimal length and speed very informitive thanks

Give away the cut of pieces as a prize! Great and fun video. I subscribed.

Determining the "perfect" barrel length is a trivial math exercise, not a machinists job.

What cartridge are you shooting lol? I haven't seen it mentioned yet I'm 1:30 in

They actually put a folding stock on this fuckin thing 🤣🤣🤣

High quality video and editing. Nice job. Thanks.

Screw bipods, bro got the mf hexapod on that bad boy, damn 💀

Technically Brad Deberti has the longest rifle barrel on RU-vid.

*clearly* what should have been done instead was the addition of a bayonet lug

The anti SBR

Great video. I been saying longer barrel faster speed for years and it is cool to see video proof. Seen way to many people claim short barrels are faster and better when my personal experience has been the same as this video.

The ATF hates this guy for this one simple trick!

I know that everyone has different levels of experience, education and intuition about various subjects but the idea of a bullet actually starting to slow down in front of a fired cartridge, with the amount of excess blast and over pressure emanating from the vicinity of the muzzle when it exits, is UNFATHOMABLE to me. Even a cursory look would tell me that there's so much unused heat and sound energy at the point of exit, that we could possibly talk about a .308 slowing more than a few fps per inch) after multiple yards rather than feet. Now, I'm 50+ years old and have been shooting everything since childhood, hunting, shooting bench, silhouette, 3 gun, shotgun sports, etc. While I rarely think about a rifle report after decades of doing it, all you have to do is see the reaction of someone who's never been next to a relatively powerful cartridge when it's fired. They say wow! Their eyes get big! They say things like, "I felt that in my chest" or "do the earmuffs really do anything?" Even if you get to a long enough barrel where pressure actually drops, that drop so gradual in the relatively short space that the bullet is traveling down the barrel that you'd expect see very little deceleration. The pressure would need to fall below 1:1 ratio with friction for the bullet to even coast. After that it would take multiplied sums of negative pressure to slow that bullet (significantly) which doesn't exist. Once you accelerate a bullet to the speed apex, you may have the remaining energy to past through 50 yards of barrel or more. All one would need to do is calculate the coefficient of friction of a particular bullet in a particular barrel and it would tell you how far it would travel after the 1:1 ratio of force to friction. You could probably run a similar test with the .22LR and also find very little deceleration or at least a bullet coasting from 3-6 feet. It would probably be fun to try!

Awesome video, unexpected results for sure. Earned my sub.

could you try a longer barrel? and find the turning point

This is excellent. Inquiring through the scientific method.

5:20 maybe since the barrel was so long the pressure was held behind the bullet longer/better? (Instead of escaping at the muzzle sooner on a shorter barrel)

Soo 338 lapua at 6ft barrel might be good?

Those americans ... Not surprised that their country is falling apart ^^

This is really cool, I'd love to see what a subsonic caliber would do with extreme barrel length perhaps it you could achieve a hearing safe result

Now we need this for .22LR :D

If you ever feel useless, remember that this gun has a folding stock.

I’d like to see this with m193 5.56

The left and right movements, I'd suspect would be from un square cuts and no crown. Still very cool guys 👍💪

That's awesome, thank you for collecting and sharing that data. Several years ago I published the results of doing something very similar with a shotgun. I started with a barrel length at 36" and cut it every inch, measuring MV with slugs, and every 6" in group size with buckshot. We ended up with a 6.875" barrel when done. The results were surprising and I'm still contacted about it today. It was published in Small Arms Review Magazine.

I am so happy for RU-vid. I have seen this test done twice before but no one recorded it before computers. Now there is proof for all time! Great job and well done.

That was an epic test!! Thank you for the info!! I guessed 2750 at 6ft but I really thought it would speed up more to like 2900ish around 36-40 inches of barrel. Interesting find. I wonder if a larger case capacity cartridge would yield similar results across the board or if this was a function of combustion chamber size vs fuel?? 308 was a great choice though as we can all relate to it and understand it well. Love this test! Thank you!!

This is only a few meters shorter than Saddam's infamous superguns "Project Babylon".

That was an interesting spike around 25-26 inches. Any ideas on that or just an anomaly?

I’m loving these scientific yet entertaining videos

Very fun and informative test! Thank you!

Ha this looks like a cool video. Dunno why reloading books list 24 inch barrels but 6ft puts them to shame lol

that is so interesting. there's barrel harmonics at play here. to the point where cutting small bits off the front change how the barrel is moving and causes shifts to the aim.

Omg,wtf, awesome watching 👀 guys , very entertaining 👏.