Do long RFBR barrels shoot better?

Bill,
As you have so often mentioned, gas pressure significantly deforms the projectile (particularly its base) during its first few inches of travel. I think we can safely assume that this deformation does not improve the uniformity of the base nor it's perpendicularity to the axis of the bore. As far back as the early 1900s, Dr Mann (in his book, The Bullet's Flight) demonstrated the deleterious effects of nonuniform, oblique bullet bases on accuracy. Inasmuch as longer barrels mean lower muzzle pressure, I always suspected that the lower muzzle pressure meant less gas blast disturbance on the deformed/imperfect base of the bullet as it exited the muzzle. I believe that this effect may be, at least in part, the cause of the better accuracy shown by longer barrels.
Hawkeye Wizard

Friend HW

Hawkeye Wizard said:

Bill,
As you have so often mentioned, gas pressure significantly deforms the projectile (particularly its base) during its first few inches of travel. I think we can safely assume that this deformation does not improve the uniformity of the base nor it's perpendicularity to the axis of the bore. As far back as the early 1900s, Dr Mann (in his book, The Bullet's Flight) demonstrated the deleterious effects of nonuniform, oblique bullet bases on accuracy. Inasmuch as longer barrels mean lower muzzle pressure, I always suspected that the lower muzzle pressure meant less gas blast disturbance on the deformed/imperfect base of the bullet as it exited the muzzle. I believe that this effect may be, at least in part, the cause of the better accuracy shown by longer barrels.
Hawkeye Wizard

Click to expand...

Friend HW:

Why did I know that you would respond to this thread?

Cause you're just like me, you're curious and you want to know..........

You just may have found something............your statement in orange...

Let me ask you this:

What about the velocity difference I spoke of...............will 20 FPS difference at about 18 inches, remain 20FPS at the muzzle of about a 27 inch or so barrel?

Once again, your comment in orange is most thought provoking...

Your buddy, BC

Hi Bill!

Intresting thread.

I have old Valmet prone rf.Made 1959.Barrel lenght 27,75 ".I am pretty sure that it is one of the most accuracy rf in our little country if we take rf:s without tuners.

It weight goes over HV class and I have shooted with it only one I.R.50/50 competition,result 750 / 43 X.

When I have excellent lot Center X to it I shoot outside range to 1 card first 22 shots to 53 m (58 yd) and there was 21 X and 1 ten.

It is difficult to find bad lot to it,but because it not have tuner,excellent lot to it,needs that speed variation must be < 4 m/s (<13 feet/s) and thisway lots are near "mission impossible".
(Our accuracy team tests hundreds of lots per year and it is possible that nobody finds thisway lot in one year).


Ok.Before I get chrono I believed to "urban legend" that longer barrel gives smaller speed variation.Chrono didnt confirm this when comparing same lots also in shorter barrels.

Then I thought why this long barrel "eats everything" ok ? It must be barrel muzzles vibration "speed"?...Is muzzle vibration "speed" slower on longer barrel?
And thats why it gives smaller vertical dispersion?

This smaller muzzle pressure is not bad idea.Sometimes I thought Mc Coy tests to wind drifting and bullets speed.Slower bullets wind drift is smaller in 22 LR ofcourse.

Smaller speed bullet has also smaller muzzle pressure...Bigger bullets vibration makes bigger "wind area" to it and then we get bigger wind drift.

BR, Timo

Friend Timo

Timo said:

Hi Bill!

Intresting thread.

I have old Valmet prone rf.Made 1959.Barrel lenght 27,75 ".I am pretty sure that it is one of the most accuracy rf in our little country if we take rf:s without tuners.

It weight goes over HV class and I have shooted with it only one I.R.50/50 competition,result 750 / 43 X.

When I have excellent lot Center X to it I shoot outside range to 1 card first 22 shots to 53 m (58 yd) and there was 21 X and 1 ten.

It is difficult to find bad lot to it,but because it not have tuner,excellent lot to it,needs that speed variation must be < 4 m/s (<13 feet/s) and thisway lots are near "mission impossible".
(Our accuracy team tests hundreds of lots per year and it is possible that nobody finds thisway lot in one year).


Ok.Before I get chrono I believed to "urban legend" that longer barrel gives smaller speed variation.Chrono didnt confirm this when comparing same lots also in shorter barrels.

Then I thought why this long barrel "eats everything" ok ? It must be barrel muzzles vibration "speed"?...Is muzzle vibration "speed" slower on longer barrel?
And thats why it gives smaller vertical dispersion?

This smaller muzzle pressure is not bad idea.Sometimes I thought Mc Coy tests to wind drifting and bullets speed.Slower bullets wind drift is smaller in 22 LR ofcourse.

Smaller speed bullet has also smaller muzzle pressure...Bigger bullets vibration makes bigger "wind area" to it and then we get bigger wind drift.

BR, Timo

Click to expand...

Friend Timo:

Common sense, whatever that is, would tell one that the bullet that was 20FPS slower at 18 inches would be even slower than the faster bullet by the time it drug down to 27 inches......

So, if that were the case, then a long barrel would actually be a handicap to increased accuracy....

__________________________


I've now worked with barrels up to 32 inches long......all were approx .900" in diameter....

I've found that about 27-28 inches is as long as one can make the barrel if one uses a MD...........

When I've tried MD's on barrels longer than 28", they will shoot, but, you can't shoot them fast.......

There is a vibration, tuning fork effect, that takes place with a MD is hung off of extremely long barrels...

Jeff Paterson and I spearmented with a 32" barrel with a MD, and as long as you waited 20 seconds, or so, between rounds, and you refrained from toughing the gun while you fired the next round, save for the trigger, it shot good...

But if you tried to shoot it fast, it was all over the paper....

_______________________________


Hawkeye Wizard may be on to something.........

I still, for the life of me, don't understand how these lead bullets shoot as good as they do, cause they get jack up all out of shape when shot...

I've picked them up about 20 yards behind my target, which is low to the ground with grass behind, which leaves a long strip cut through the soft ground and grass, and surprisingly, keeps a lot of the bullets pristine.............

And those bullets are bull butted, all jacked up, no sign of the crimp indentation left......

So Hawkeye's theory, that the less pressure on those jacked up bullets as they exit the muzzle of longer barrels, may provide less side kick to those disturbed heels may have merit.......................maybe.

Your friend, BC

PS: Your comment in orange:

I don't believe so..........the exact center of the parallel node on say a 32 inch barrel, compared to a 24 inch barrel, is further back from the exit of the crown, so the arc of muzzle oscillations is greater on the long barrel, ie., more potential vertical from odd velocity rounds, not less.
( I'm talking about a naked 32 inch barrel of course)

Bill,
This is in response to your question “…will 20 FPS difference at about 18 inches, remain 20FPS at the muzzle of about a 27 inch or so barrel?”

It’s not a trivial question. It took me a while to develop a reasonable response. First, let me say that I have NO DIRECT DATA on which to base an answer to your question. I’ve searched the internet for applicable data, but so far, I can’t find any.

Without data, we’re left in the realm of hypothesis. So, what you’re going to get is only hypothesis…. opinion…. Hopefully, it will be a hypothesis that supported by some logic.

My first answer to your question is …. “It depends.” It depends on what caused the 20 fps difference at 18 inches. Many things can cause such a difference in velocities. (Actually, 20 fps isn’t very much. It’s only a 2% difference.)

If we clarify/limit the question, we can reduce the number of potential causes of the velocity variation. Then, we may be able to provide a more definitive response. Let’s specify that the two cartridges were the same brand and lot number, fired consecutively from the same properly warmed rifle, and that they had the same physical and ignition characteristics. With those limitations, it's reasonable to assume that the velocity variation was caused by variation in the amount of propellant. Under that assumption, the SHAPE of the Pressure-Time Curve should be similar for both cartridges.

Now let’s take a look at this typical Pressure-Time Curve for .22LR. (I tried to paste the graph here, but it won't paste into this thread. So, I've pasted the link. If the link doesn't work, you'll have to Google ".22LR Pressure Time Curve" to see what I'm trying to explain.)



https://www.google.com/search?q=.22...XKQ17bAQM:&usg=__2fUiUV3jwrNPgLhQPWKKNp07U9A=


Note that even at the muzzle, there is still significant pressure ( approximately 500 psi) behind the bullet. The bullet really isn’t “coasting”. It’s still being pushed by gas pressure. The pressure simply isn’t enough to compensate for the frictional forces that are slowing the bullet down.

The graph shows pressure-time curves for two .22LR cartridges with 40 fps difference in muzzle velocities (twice the difference in your question), so what we see on that graph should be applicable to our question too.

Now, note that the only significant difference between the two graphs occurs between 0.0004 and 0.0006 seconds after ignition. Muzzle exit is approximately 0.0026 seconds after ignition. The difference occurs very early in the bullet's travel. After that the two graphs duplicate each other. My deduction from the graphs would be that the difference in the two muzzle velocities occurs very early in the bullet's travel. After that, the difference is maintained until muzzle exit.

Soooooooooooo, in my opinion, a 20 fps differential in velocity at 18” would be approximately the same at 27”.

Does this make sense?

Hawkeye Wizard

Hi!

I have not vibration measuring device to barrel,must only try to think the reasons.

What about longer stopping time in longer barrels muzzle up and down points?

Also I try to think this: Longer barrels own mass is bending barrel muzzle more down, what is difference to muzzle movement comparing to shorter barrel when bullet goes through?

Hopely find the answer of longer barrel mystery with you.I can sleep my nights better.

BR, Timo

Bill,
Above, I had theorized that reduced muzzle blast might contribute to the accuracy of longer barrels. But, unsupported theories are merely opinions and you know what they say about opinions.
I thought I’d see if I could develop any data to support or refute the theory.

In another thread, I linked a graph which showed that pressure in the bore of a .22LR rifle was about 500 psi at bullet exit. I calculated the force that 500 psi would exert on the base of the bullet as follows:
Force = Pressure X Cross Sectional Area = Pressure X Pi X Radius squared
Force = 500 psi X Pi X 0.11” X 0.11” = 19 lbs

The weight of a .22 LR bullet in pounds is:
40 grains X 1 lb / 7000 grains = 0.006 lbs

We have a poor bullet that weighs about 0.006 lbs being pushed by a force of 19 pounds. The pushing force is more than 3000 times greater than the weight of the bullet. Imagine what that force-to-weight differential can do if it is asymmetrically released by an imperfect bullet base. And the only defense the bullet has is the stability afforded it by spinning in the rifling.

It would certainly appear that muzzle pressure is high enough to contribute to bullet instability.

In fact, it’s a wonder that we can hit anything at all!!!!!!

Hawkeye Wizard

Friends Timo and HW

Friends Timo and HW

Friend Timo:

I don't think the advantage that we "may" have in longer barrels is due to vibration issues....

One can easily over weight these long barrels with a MD and they become hard to control......

Seems like if the longer barrels possibly being more accurate was a weight issue, we could just keep adding weight and they would shoot better and better............but we can't.....

And as the entire world of rimfire accuracy knows by now, I don't subscribe to the "compensation" theory as to why a MD produces better accuracy.

No, there is something to do mechanically, physically with the way the bore handles our waxed, lead bullets.............???

Or, as HW theorizes, the further away from the peak pressure, the less and less the remaining pressure in the bore affects the stabilization of the bullet as it exits the crown.........?

I've got to do a plumb silly movie.................

I shoot groups in the shop by using only the barrel, no action and no live ammo...........and it's amazing how well the barrel will group....target is only 10 feet away.........

__________________________________________

Friend HW:

500 FT pounds still at the muzzle, at 27 inches, should most certainly affect a deformed base bullet...........

But, would it not be, that the muzzle pressure at say 22 inches, which has to be proportionally higher, would affect the deformed heel of the bullet more?

Your friend, BC

Bill,
Per your last question, yes, I agree that the higher pressure at 22 inches would affect the bullet more than the pressure at 27 inches. I think that's why 27 inch barrels are less sensitive to ammo perfection.
Hawkeye Wizard

I have been experimenting with the theory of the turbulent air in front of the bullet and the gasses tipping the bullet as it comes out the muzzle for some time now. I have made several different styles and designs of tubes that thread in the front of the Harrel tuner. I have had mixed results with some of the designs and good results with others. I'am working on and testing a new design that I came up with and I've had some really impressive results with this new design, it's a entirely different style from the others I've made in the past. I will not post any pics of it as of now, I have a couple of small modifications I need to do to it but from my testing so far I think it's going to be a real winner. Here's a couple of the other designs I've made...

Hi!

End of 80s and begin of 90s I worked in team who developed Reflex-supressors.And owned 50 % of this company since 1995.

www.guns.connect.fi/rs/

Over 90 % of cases rifles accuracy goes better with Reflex-suppressors.(Also in our Army tests).There was few theories why, barrel vibration,smaller recyl,but also this pressure turbulence on barrels muzzle.

DBlue! Maybe you can use high speed camera when you develop your product? It should be intresting to see what is changing on the muzzle when use your "turbulence control device".

www.kuulapaa.com/

But ofcourse target tells everything.

BR, Timo

Hello Timo.....I have studied hundreds of high speed photographs of .22 rifles being fired and in my opinion I think that the cloud of turbulent air that is being pushed out the barrel in front of the bullet has more effect on tipping off the bullet than the gasses. The bullet has to pass through that cloud of turbulent air, the hot gasses being behind the bullet I suspect could cause sort of a shockwave effect also. The device I have made will disperse that air and the gasses, giving the bullet a cleaner path when it exits the muzzle. The thing I have noticed the most in testing this device is that the barrel is not as ammo sensitive as it is without it. I've been testing it with a Benchmark .900 three groove barrel that I chambered and fitted to a Suhl action, the barrel is 26". I would love to find a photographer that has the equipment to do that kind of high speed photography to be able to show the effects with the device and without.

Don

Hi Don!

Keep on going your excellent work.Developing new is hard work and must go by fails & successes.

Maybe you looked also those fotos link here under.Mr Kuulapaa has take fotos with different things on barrel mouth.His camera takes 160 000 frames/s.(If he have not buy faster one).

http://kuulapaa.com/home/highspeed/rifles.html

Speculation from me,but bullets must push "un burned" powder front of it in barrel.In longer barrel there is in some cases less of it.

Maybe supressor & other devices on the muzzle takes it little off and then it not disturb bullet so much on the muzzle.

BR, Timo

Friend Timo

Timo said:

Hi!

End of 80s and begin of 90s I worked in team who developed Reflex-supressors.And owned 50 % of this company since 1995.

www.guns.connect.fi/rs/

Over 90 % of cases rifles accuracy goes better with Reflex-suppressors.(Also in our Army tests).There was few theories why, barrel vibration,smaller recyl,but also this pressure turbulence on barrels muzzle.

DBlue! Maybe you can use high speed camera when you develop your product? It should be intresting to see what is changing on the muzzle when use your "turbulence control device".

www.kuulapaa.com/

But ofcourse target tells everything.

BR, Timo

Click to expand...

Friend Timo:

Years ago I made a device that attaches to my front rest..........

The device allowed me to place bloop tubes in front of the muzzle, without the bloop tube actually being attached to the barrel.

I tried every kind of bloop tube arrangement you can imagine.........ventilated and non ventilated, in every length imaginable, even a piece of garden hose....

What I did, was to shoot some groups, then swing the bloop tube into alignment with the muzzle, then shoot some more groups.

This allowed me to see the accuracy as bullets passed through these bloop tubes, without their weight being attached directly to the barrel...

_____________________


What I learned was this:

It mattered not whether the bullets passed through these bloop tubes or not, the groups were all the same........

Therefore, I do not use bloop tubes, as they have absolutely nothing to do with rimfire accuracy..........

_________________________________


If bloop tubes, of any configuration, actually improved accuracy, then they, like my MD's, would be mandatory at the big Nationals, if one expected to win....

But the greatest accomplishments in big time RFBR were without a bloop tube hanging off of the muzzle....

The prime example being Chuck "Ragiong Inferno" Morrell's 12,050 PSL all time record score.............no bloop tubes or mid barrel weights....

__________________________________


Friend Timo, remember, bloop tubes, suppressors and recoil reducers (muzzle brakes) add weight in front of the muzzle of a barrel, just as my MD's do........

_____________________________


One last comment:

Throughout my career of building RFBR guns, I've made it a policy to use the absolute best materials and practices........

If I thought that hanging a bloop tube, of any arrangement, off of the muzzles of my guns would increase their accuracy, I'd do it in a heartbeat..

Same goes for mid-barrel weights...........

But I've thoroughly vetted both, and there is no accuracy benefit from their use.............


Your friend, Bill Calfee

Hi Bill!

As I said: There was few theories why, barrel vibration,smaller recyl,but also this pressure turbulence on barrels muzzle.

They were theories.

Only fact was that over 90 % of cases accuracy goes better with Reflex Supressors.

But we must continue searching the ultimate rf!

BR, Timo

Friend Timo

Timo said:

Hi Bill!

Only fact was that over 90 % of cases accuracy goes better with Reflex Supressors.



BR, Timo

Click to expand...

Friend Timo:

I have no doubt about it................but, the question of the hour is: Why?

You ,or anyone else who wants to know the facts, as to whether 22 RF bullets passing through bloop tubes have increased accuracy, or not, can perform a simple test.

Use you imagination and construct a simple holding fixture that attaches to your front rest.

Design your simple fixture to hold different diameter bloop tubes........very simple and easy to do....

Then, shoot some groups with your favorite RFBR gun, then attach any bloop tube, you wish, to the fixture, and position the bloop tube in front of the exit of the crown, with the end of the bloop tube extending back over the muzzle slightly........how far matters not.

You now have the bloop tube in place, but, not attached directly to the barrel....

Then shoot some more groups........

Friend Timo, anyone on the face of this earth will immediately, including you, see that there will be absolutely no difference in your guns accuracy.........

Your gun will have exactly the same accuracy level, with or without, the bullets passing through the bloop tubes....

__________________________________


If anyone is "serious" about knowing the facts about bloop tubes and accuracy, the above test will tell you.


Your friend, Bill Calfee

Mr. Calfee....I agree 100% with you about a plain hollow bloop tube vented or non vented is not going to make any difference in group size on any rifle. The tubes that I posted the pics of are not just plain tubes with slots cut in them. You can't just hold them in front or over the end of the barrel in a fixture and shoot through them. I don't even consider these being bloop tubes as they will disperse the air and gasses out that slotted section and I have several that does make a difference in the groups. The difference is not a earth shattering difference, but more like a half bullet diameter difference in the group size. To me a half bullet diameter difference in group size is a step forward. This style of tubes is what I started off experimenting with and from testing this design out I have come up with a completely different design that works on a similar principle and I have got even better results. I'm not trying to make any claims but I do know that I'm heading in the right direction with this new design I'm working on. The only reason I posted on this thread is when the subject of the gasses tipping off the bullet when it exits the muzzle were brought up. I have nothing but the upmost respect for your knowledge and years of experience and I have no motives whatsoever in making these posts.

Don Blue

Do long RFBR barrels shoot better?

CYA friends:

We've had an excellent discussion about long barrels and their possibility of providing an accuracy enhancement.

__________________________


Something interesting happened when I made the movie of me shooting the barrel in my shop, using compressed air from one bullet being pushed smartly through the bore to fire the bullet I had pushed to the muzzle.

The barrel was clean when I started......

When I pushed the first slug through the bore it felt kinda ratty.........not bad, as it is a very good barrel....

I then pushed two or three more slugs through the bore and got some wax build-up.........

Then I pushed the first slug, to fire, to the muzzle and the bore felt so smooth.....

I fired it, then pushed the second slug through the bore to the muzzle........and the bore felt silk smooth again...

I then decided to do the movie of the third round being fired........

I went to my house to get my camera...........had to pee-pee, get a drink of water, etc, so I was gone maybe 10 minutes, maybe a little less.

Anyway, I got the camera all set up, then pushed a slug to the muzzle...............

And what an interesting surprise............the bore once again felt kinda ratty................yes.

So, I went ahead and pushed that slug out the muzzle and then pushed another slug through the bore, and the bore felt smoother......

So I pushed a third slug through and the bore felt silky smooth once again...........

Soooooooooo..........................( I like doing these long soooooooooo's)

Even with me not using live ammo, I still needed to foul the bore...............wax the bore is a better term...

( My gut tells me that there's much more to learn from this incident, about the effect of wax in making lead bullet accuracy, much more.)

____________________________


OK, what's this got to do with long barrels?

Even with the most excellent discussion we've been having about long barrels and accuracy in this thread, my gut tells me we ain't figured it out, yet.............

My "gut" tells me that the possibility of an accuracy advantage with long barrels has something to do with how the longer bore handles our waxed, lead bullets, AFTER the peak pressure rise has subsided...............

I'm talking about some sort of physical action by the interior of the bore on the wax and the bullet....

Your friend, Bill Calfee

Hi!

I think we havent got yet the "patent answer" why longer rf barrel "eats near everything" comparing shorter.

What about this funny idea: Think that lead bullet is "pumps piston". Air mass is about 1,22 kg / m3.(If I didnt make mistake there is about 0,02 g air in the 30 " barrel and 0,016 g air in 22 " barrel).

Small difference in weight,but when we give to "piston" 160 m/s average speed THERE IS FORCE DIFFERENCE.

In longer barrel "lead piston" must work harder to push air off.

Is there coming better "condensation" to bullet and longer barrel "eats near everything"?

Also air weight is changing when wheather is changing.(Temperature,air pressure,humidity,)


BR, Timo