Barrel flexion (in a Colt Monitor)

[AJMD429]

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Sometimes it amazes me how accurate guns can be, yet how much the barrel wobbles if you look at high-speed film.

This BAR wouldn't be a 'match rifle' I know, but with that much wobble you'd expect ten-foot groups at 100 yards, and I'm sure it's better than that - https://youtu.be/Jb6C9ASylmQ?t=845

[Ray]

Deleted.

[AJMD429]

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...supposedly most of the motion we see is after the bullet has exited, and I guess that must be the case, given how accurate most guns actually are.

https://www.youtube.com/watch?v=fbuaH6D2Qgc

[AJMD429]

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Just had to toss this video in even though it is at the other end of bullet travel:

https://www.youtube.com/watch?v=QfDoQwIAaXg

[Sixgun]

Doc,
I don't know what that flexing is but it makes no sense. The BAR WAS noted for its accuracy and they are....my semi auto version is all GI except the receiver which makes it suitable for semi auto only.

I had a gunsmith installed custom scope mount put on mine and it is a match rifle and I have used it as such....it's a solid MOA rifle out to 547 yards or 500 meters. With 150' gr match Sierra's it will group 3/4 at 100 and 1.5 or less at 200 meters. At 300 meters the 168's do their work and keep them MOA.

I've used mine in half scale silhouette matches ou

[AJMD429]

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I'm thinking maybe that the guy I linked to above is right - that most of the really-floppy vibration happens AFTER the bullet has exited. It would be interesting (and I think easy enough) to put a close-up camera to the barrel and see what amount of vibration happens BEFORE bullet exit. 'They' say that as long as the vibration is THE SAME EACH TIME it doesn't matter much, as well.

Maybe that SmarterEveryDay guy could do a video on the topic. He likes guns (he's the one who built a huge cannon just to shoot a softball at supersonic speeds).

[JimT]

I'm thinking maybe that the guy I linked to above is right - that most of the really-floppy vibration happens AFTER the bullet has exited.

I am of the opinion that he is correct. On the Colt Monitor video it appears that the Cutts Compensator directs gas upward which would result in the barrel being pushed downward. The flexing is the result of the barrel being forced downward as the gas escapes. After that the barrel would spring back, resulting in the up and down movement. All this would happen after the bullet exits.

At this point in time that is my guess.

[Sixgun]

OK Jim....while doing somewhat "hobbyist" load development for the BAR for our long range half scale matches these are my results...it's very expensive to play with match 30 cal. bullets so once I reached MOA, I quit...

Forget all of the loads and what I used.....immaterial here

.......it's WHAT I kept on the gun and it makes no sense....the floppy GI issue bipod.......common sense would say to take it off so that's what I did.....the gun was an honest 3 MOA gun after approx. 300 carefully shot rounds using match bullets seated out and loaded one at a time and that's what I figured it to be and decided it would be of no use as a match rifle......(keep in mind there's very little 100 meter shooting tests.....near anything shoots good at 100 meters and my testing was done at 2,3,4, and 500 meters.

For the hell of it I put the bipod back on in the flipped up position and tightened the adjusting wing screws....instant MOA....

Even when the screws loosened it stayed on target and accurate.

All stories have 2 sides and yes, if I shot fast to heat it up, didn't hold properly, watch the wind, trigger control, the bullets would not go where I thought they would go but if all conditions were adhered to, it was a match rifle....WITH the bipod on.

Kind of messes with that "flexing issue" don't it?

I used to get la

[JimT]

I was referring to the video on the "Forgotten Weapons" segment ... you can see the barrel moving on that one and I am of the opinion it's the Compensator that's doing it. It may not hurt the accuracy a bit.

I am not really all that surprised that yours shot better with the bipod. I have seen similar things with the Russian Mosin Nagant. Take off the attached bayonet and accuracy goes in the crapper. It might just be that the guys who designed 'em knew what they were doing.

[GunnyMack]

You guys forget, this topic has been discussed and solved around every campfire, hunt club and boardroom. Short & fat= stiff, long & skinny = bull whip. That being said steel is going to move no matter what.
Remember the Pachymer 'barrel de-resonator' ? It was that doughnut thing ya slid down the barrel to the forend tip. It worked and well ! I saw it with my own .
Whilst at skool we had a copy of a video from S&W, it was high speed film of I believe a 1059 in a machine rest. Frame by frame you could see the slide flex, the barrel moving. Heck even the slide stop lever appeared to be having a caffeine induced seizure! Eye opening to be sure.
So yeah Six the bipod took vibration away from the barrel, not surprised by it.

[Sixgun]

Yes Jim...I know that ......on your observations with the Cutts...... the slow mo video is extremely exaggerated.....it's not going to flex an inch. Remember that thing Browning had on their rifles...BOSS...I still don't and never will understand it all as I've been to countless matches with some of the best long range shooters in the country. At the Ridgway Rifle Club they do the 850, 900, 950, and 1000 yard "benchrest varmint silhouette shooting". The targets are very hard to see with the naked eye and unless you have a $1500 or more scope you will not be competitive. The rifles used are top of the line bolt guns usually with 30" barrels and I saw ZERO muzzle devices other than an occasional brake. So...if muzzle devices work, why don't these guys use em? There is a weight limit...I think 12 pounds....you won't see no rail guns.

We both know every rifle is a mystery to itself.

My Colt AR with it's free floated factory 16" barrel is stiff and outshoots every 30" .223 bolt gun other guys use....

I don't know, my head hurts....I'm gonna go down and play with something I know...single action Colts.....with cast bullets!---006

[JimT]

I don't know much about rifles so I'm just guessing.
BUT .. we had a Colt SAA .45 that flexed!
Once.
One way.
Somehow it got dropped and a horse stepped on it. From then on it hit 4 or 5 feet to the left at about a hundred yards.
I could break gallon glass jugs at a hundred yards .... if I had some extra shells so as to get the proper windage.