Barrel Contour vs Accuracy

[gunsandgunsmithing]

THIS from the guy who, on my first post ever on this board answered "We don't like nor want your BRC type over here... please leave"


seriously Alex?

You "want to discuss" with people who'll agree with you and stroke your ego..... that's not "discussion" ...... that's a group of like-minded people gethered together for some barbeque and beer.....

Al, you're one of my all time favorite posters, both here and on BRC. We may not agree all the time but that's ok. We do much more often than not and I like reading your posts anyway. Frankly, this place needs more BRC folks and vice versa. The number one thing about BRC is BS won't fly there. I like that. It's THE main reason I did vibration analysis testing when all that really matters(erd) is the target...cuz I knew you can't get anything by on there without scrutiny. So, I prepared myself for the scrutiny...at least where tuners are concerned. I still get some scrutiny over here from a few doubters but with very few exceptions, I don't post theory when it comes to tuners...I've done it and tested it both, or I try to be very clear if I haven't physically tested it. I don't know everything about anything but I do know that if you're gonna make some of the claims that I DO about tuners, yaz gotta be able to back it up over there!

 

[Bart B.]

The barrel is already deflecting downward before a shot is even fired, due to gravity, though. So, it's first movement is downward as the bullet begins it's travel down the bore. Because the barrel is pre loaded by gravity, it will come up and ultimately, the travel be larger..due to the energy held with the material.

The muzzle axis can point further down when the bullet starts out of the case. Then lower from the recoil axis being above the rifle center of mass as the bullet goes several inches into the bore. Then it starts its upswing towards its peak pointing above the LOS. Agree?

 

[gunsandgunsmithing]

The muzzle axis can point further down when the bullet starts out of the case. Then lower from the recoil axis being above the rifle center of mass as the bullet goes several inches into the bore. Then it starts its upswing towards its peak pointing above the LOS. Agree?

Sounds plausible but the bullet is only in the bore for maybe .030-.050 of gun travel...fwiw.

 

[Bart B.]

Sounds plausible but the bullet is only in the bore for maybe .030-.050 of gun travel...fwiw.

What units? Seconds? Inches?

 

[gunsandgunsmithing]

What units? Seconds? Inches?

.030"-.050"...inches of gun travel while the bullet is still in the barrel. Not sure it matters to your point though.

 

[Bart B.]

According to the computer modeling I've seen, its several hundredths inches.

Corrected my error.

 

[gunsandgunsmithing]

According to the computer modeling I've seen, its several inches.

If they're saying that the gun moves"several inches" during the roughly 1.5 milliseconds that the bullet is traveling down the barrel, you should find different models, seriously. Think about that!

 

[Toby Bradshaw]

This is a high school physics "third law of motion" problem. Just to make the arithmetic easy, assume a 70gr bullet + powder (=0.01 pounds), a 10-pound rifle, a 3000 ft/sec muzzle velocity, and a barrel length that has the bullet traveling 24" (2 feet) to the muzzle. At the muzzle the bullet's momentum is 0.01*3000=30lb-ft/sec. The rifle has the same momentum but in the opposite direction, so a 10-pound rifle (if unrestrained) is moving at 3 ft/sec. The average velocity of the bullet during its trip down the barrel is 1500 ft/sec, so the bullet spends 2/1500 sec (=0.0013 sec) in the barrel. The rifle travels 3 ft/sec * 0.0013 sec = 0.0039 feet (=0.048 inches) while the bullet is in the barrel.

 

[LA50SHOOTER]

This is a high school physics "third law of motion" problem. Just to make the arithmetic easy, assume a 70gr bullet (=0.01 pounds), a 10-pound rifle, a 3000 ft/sec muzzle velocity, and a barrel length that has the bullet traveling 24" (2 feet) to the muzzle. At the muzzle the bullet's momentum is 0.01*3000=30lb-ft/sec. The rifle has the same momentum but in the opposite direction, so a 10-pound rifle (if unrestrained) is moving at 3 ft/sec. The average velocity of the bullet during its trip down the barrel is 1500 ft/sec, so the bullet spends 2/1500 sec (=0.0013 sec) in the barrel. The rifle travels 3 ft/sec * 0.0013 sec = 0.0039 feet (=0.048 inches) while the bullet is in the barrel.

Toby, - I like your post because you showed a mathematical solution to a circumstance. - Question if I may ? - You mentioned "unrestrained" (which to me equates to free-recoil) - Can you tell us what happens when we apply certain amounts of shoulder pressure ? - Or is that basically "negligible" / unchanging to the outcome you provided ?

Thanks, - Ron -

 

[LCazador]

View attachment 1083629


Thank you. You said, "The last thing you want is for it to be off to one side or crooked to the barrel". It already is, from the factory. A barreled action does not sit straight in the barrel channel. And the stock wall thickness at the forend barrel channel is thicker on the right vs left (from shooter's perspective). See photo...looks more obvious in person. Enlarging the channel will require removing more from the right vs the left while also making sure barrel sits straight. As an aside, if it looks like the bipod stud holes are also off to the right a bit, they are (mostly rear one). They are not directly in line with the stock centerline (slightly crooked). The entire front end of the stock all seems slightly "off" somewhat in how things line up. I have reservations about trying to work with an already misaligned barrel channel and enlarging at same time.

Try a sanding drum with a drill extension on your drill. I have different diameters of sanding drums that I use for barrel channels. Works quick and accurately. Mask off the stock around the barrel channel to prevent sanding damage. In case your sanding drum gets away from youl

 

[Bart B.]

If they're saying that the gun moves"several inches" during the roughly 1.5 milliseconds that the bullet is traveling down the barrel, you should find different models, seriously. Think about that!

I did and realized my error, then possibly fixed it.

JBM recoil computer modeling software says a 44.0 gr charge weight producing a muzzle Velocity of 2700 ft/s with a firearm weight of 10 pounds shooting a 168 grain bullet has a recoil velocity of 9.4 ft/s. A 1.1 millisecond barrel time calculates the rifle should move .01316 inch. I think.

Corrections welcomed.

 

[gunsandgunsmithing]

I did and realized my error,me then fixed it.

I think Toby did a wonderful job of explaining it.

 

[Toby Bradshaw]

You mentioned "unrestrained" (which to me equates to free-recoil)

Technically, free recoil without friction.

- Can you tell us what happens when we apply certain amounts of shoulder pressure ? - Or is that basically "negligible" / unchanging to the outcome you provided ?

The extreme case would be a rigid fixture that prevents the rifle from traveling backward under recoil (neglecting the effect of the recoil on deforming the fixture or changing the rotation of the Earth ). So the movement of the rifle I described can vary between ~0.050" and zero depending on how "freely" the rifle is allowed to recoil.

If you are holding the rifle such that your weight is added to the rifle's weight, the rifle will move backwards less while the bullet is in the barrel than if the rifle were recoiling freely/frictionless. How much less depends on your mass and the rigidity of the connection between you and the rifle.

 

[Toby Bradshaw]

Toby, - I like your post because you showed a mathematical solution to a circumstance.

Just a cautionary note -- like many physics "calculations" this is more of an estimate than a to-the-millisecond take-it-to-the-bank number. I assumed that the gas escaping from the muzzle is traveling at the same velocity as the bullet (gas is really traveling faster), that the bullet accelerates uniformly in the bore, that the rifle recoils without friction, etc.

At any rate, with typical bullet weights, powder charges, rifle weights, barrel lengths, and resistance to recoil (friction, shouldering, etc.) the rifle is moving a small fraction of an inch (not multiple inches) while the bullet is in the barrel.

 

[LA50SHOOTER]

Technically, free recoil without friction.



The extreme case would be a rigid fixture that prevents the rifle from traveling backward under recoil (neglecting the effect of the recoil on deforming the fixture or changing the rotation of the Earth ). So the movement of the rifle I described can vary between ~0.050" and zero depending on how "freely" the rifle is allowed to recoil.

If you are holding the rifle such that your weight is added to the rifle's weight, the rifle will move backwards less while the bullet is in the barrel than if the rifle were recoiling freely/frictionless. How much less depends on your mass and the rigidity of the connection between you and the rifle.

- Understand & Agree Toby as what you stated all makes perfect sense. - What I was looking for is "barrel time" of the bullet - less OR more time when the stock is shouldered ?

 

[MikeMcCasland]

So for us mere mortals, where did we settle on this? The heavier the contour the better for accuracy?

 

[Toby Bradshaw]

What I was looking for is "barrel time" of the bullet - less OR more time when the stock is shouldered ?

If by "barrel time" you mean the total time that the bullet is in the barrel, there won't be much effect of shouldering the rifle.

 

[Bart B.]

So for us mere mortals, where did we settle on this? The heavier the contour the better for accuracy?

They do reduce muzzle axis movements during barrel time with a given hand held rifle against ones shoulder without artificial support. That makes for better results on paper.

In free recoil with consistent friction between stock and rests, I don't think they're more accurate. Well tuned load assumed. Everything is repeatable from shot to shot.

 

[LA50SHOOTER]

If by "barrel time" you mean the total time that the bullet is in the barrel, there won't be much effect of shouldering the rifle.

That's what I thought, in other words basically "negligible" / unchanged to the outcome you provided previously.

Thank You Toby !!

- Ron -

 

[alinwa]

If your going to use " " at least quote what I actually said. Heres the post your referring to http://forum.accurateshooter.com/th...recoil-reduction.3926863/page-4#post-36988050
And posting a quote that basically calls anyone who disagrees with Mike a fool sure doenst change my mind about your attitude.

I'm sorry this is hard for you Alex but here's the deal..... no "PM'ing" no behind the scenes BS.

YOU say I said "anyone who disagrees with Mike a fool" ........ what I said was "I agree with Mike here."

See a difference?

And BTW I don't ALWAYS agree with Mike, I just "agree with his stance here"..... at the time I said it. (Now that he's quoting barrel times I'm seeing some divergence Ohh Well )

And furthermore I said that Bart B was engaged in a technique I call "baffling them with bullshit" and that he was incapable of "making himself more clear" because he didn't have the facility. And furthermore that quoting Geoff Kolbe's opinions do nothing to further his agenda.....

The answer to this part is quite simple..... for BART B to step up and show me wrong. Of course he didn't and couldn't and won't....he went on to tell as how "we got to the moon via computer modeling"

again I say..... SERIOUSLY??

I'm glad you find a kindred spirit in Bart B but that just ain't what I'm about. This is a public forum. I'd rather be W R O N G and shown to be wrong than to be spewing untruth. And BTST I dislike it when opinion is sold as "truth" because I've spent tens of thousands of hard-earned dollars testing other people's opinions, believing "The Experts".... Only to find out they're just goobers like me.

I realize Alex that you value being all hooked up and linked in..... I actually know two grown up men who openly call themselves "fans of Alex Wheeler"...!!!.... but making friends on the innertube ain't my thang A'Tall. I'd much rather choke down a biggie bowl of cold crow in the interest of TRUTH and saving people money and furthering the shooting sports than to be somebody's fanboy.


sorry



differn't strokes.


And the "attitude" that bothers you so frikkin' much??? Yeahhhh, Good Luck Wi' Dat....As I told a poster in another thread about gunsafes, "no, you wouldn't like me in real life either"...... because face-to-face I'M WORSE! LOL (Altho unlike the other poster, I'll prolly meet you one of these days at a match so we'll see.....)

I have tried hard to stay out of "your discussions"..... I'll try harder in future. (dude, I din't even POST here for 18yrs! Even though....




I'll just shut up now LOL)



al-tryingnottoreplylookdumborstupid-inwa