Low Velocity Barrel

[Rsadams]

Another newbe for the ignore list....

 

[Hi-NV Shooter]

Another newbe for the ignore list....

doclu60 is an experience RFBR shooter. what he is saying is that if a .157 gain is not chased, you will not do very well in RFBR. to shoot at the National level your rifle better average under 0.200 for minimum of 5 consecutive 5-shot groups, minimum that is and you may finish middle of the pack.
so if you can cut out a 0.157 difference in hold-off in the wind from one lot to another, you better hope you have that lot on the bench next to your rifle. because if the guy next to you has a lot that he can switch to that will under the same conditions, close his hold by .157 his 100 or X hold, may be your 50 or 10

Lee

 

[orkan]

At no point was I saying .157" should not be chased. I was pointing out that its not as if you gain the full difference just by switching to 980fps ammo. You'll still have to read wind 95-98% as good as you did before, just to shoot as good as you did before. ... and I'm not saying THAT shouldn't be chased either. If we could get 980fps ammo, as suggested, then we could pick it up and it would be nice. However, it isn't as if someone is going to automatically see a .157" reduction in horizontal spread by switching to 980fps ammo. The enhanced flight path will certainly help, but it likely isn't going to be to the tune of .157" in actual shooting.

 

[linebaugh]

Alright, I will bite.

Is the 1080fps vs 980fps GAIN of wind drift (BC) attributed to a SLOWER projectile a real thing and if so can somebody explain why? Also if there is a GAIN in wind drift (BC) at 980fps then there must also be a gained vertical BC to match it. What's the phenomena that is happening here to create such an instance?

I am delving into the 22LR game now and have never heard of this concept. Can't wrap my head around it due to time of flight and both being under the speed of sound considering both bullets to be identical in form. If some of you are shooting RFBR then I would expect you to be knowledgeable and the concept to be correct or else I am not reading it correctly.

Thanks for any input.

 

[Hi-NV Shooter]

At no point was I saying .157" should not be chased. I was pointing out that its not as if you gain the full difference just by switching to 980fps ammo. You'll still have to read wind 95-98% as good as you did before, just to shoot as good as you did before. ... and I'm not saying THAT shouldn't be chased either. If we could get 980fps ammo, as suggested, then we could pick it up and it would be nice. However, it isn't as if someone is going to automatically see a .157" reduction in horizontal spread by switching to 980fps ammo. The enhanced flight path will certainly help, but it likely isn't going to be to the tune of .157" in actual shooting.

orkan,

I was not referencing anything you may or may not have said. and I understand what you are saying here.
what I think is getting lost, is the fact in RFBR even a gain of 0.100 or less by a simple switch to a known lot that shoots well in the wind regardless of it being 980-1000 or whatever a RFBR shooter will do so if they want to compete at the level doclu60 is competing at.

for me I don' get wrapped up on the numbers, I just lot test and shoot what works best at the time. I have never chrono any rim-rife ammo as IMO it is a waste of time, as you still have to test it. I know Lapua doesn't even show the velocity on the test reports.

Lee

 

[ratguner]

It has been known for many years that slower ammo (rimfire ammo) is less affected by the wind, so top shooters have always tried pistol ammo to see if there was a good batch that was accurate in their rifle.

It might sound counter-intuitive that slower ammo is less affected by the wind, but that is because the bullet drag goes as the square of the velocity (in the sub-sonic velocity region). So the higher the velocity, the greater the drag and so the more the wind will affect the bullet. It is possible to calculate an optimum muzzle velocity to minimise wind deflection and from memory it is about 980 ft/sec for 50 metres ranges.

My daughters Anschütz had the best results with pistol ammo.
Albet she was shooting 50 yards, 100 yards, 50 meters

 

[USMCDOC]

my Suhl with the Octagon barrel has shot some great scores in practice with Pistol Match

 

[seymour fish]

It has been known for many years that slower ammo (rimfire ammo) is less affected by the wind, so top shooters have always tried pistol ammo to see if there was a good batch that was accurate in their rifle.

It might sound counter-intuitive that slower ammo is less affected by the wind, but that is because the bullet drag goes as the square of the velocity (in the sub-sonic velocity region). So the higher the velocity, the greater the drag and so the more the wind will affect the bullet. It is possible to calculate an optimum muzzle velocity to minimise wind deflection and from memory it is about 980 ft/sec for 50 metres ranges.

Geoffrey, iirc McCoy claimed 950 fps based on 50 yds. Could have been the same Mach # as your finding, if atmospherics matched up. As to the imbalance of powder/primer vis a vis accuracy, has anyone tried sufficient bbl length to slow the usual target ammo in the 1060 fps range down to 980 ? Seymour

 

[doclu60]

orkan,

I was not referencing anything you may or may not have said. and I understand what you are saying here.
what I think is getting lost, is the fact in RFBR even a gain of 0.100 or less by a simple switch to a known lot that shoots well in the wind regardless of it being 980-1000 or whatever a RFBR shooter will do so if they want to compete at the level doclu60 is competing at.

for me I don' get wrapped up on the numbers, I just lot test and shoot what works best at the time. I have never chrono any rim-rife ammo as IMO it is a waste of time, as you still have to test it. I know Lapua doesn't even show the velocity on the test reports.

Lee

Hey Lee,
I think that perhaps I should have been more explicit instead of just grabbing the number that was thrown about and ran with. You and I know, no doubt about that, that what we do is more precise than any other form of rimfire games, if you want to do well. You also hit the nail on the head about lots. It's so important to have a 'lot de'jour' so to speak, that I never have less than 2 on the bench, and at the start of the match, usually 4. Finding the one that is flying the best THAT day is imperative. Could be temp, barometric pressure, clouds/no clouds, etc.......and yes, most definitely wind. Yesterday's lot that was a hero, could be today's zero.

Let's throw the 'velocity' issue away and put it like this. For whatever reason, minimizing hold off by finding the ammo that shoots better right now is paramount. As you said, you better have ammo on your bench that can do that because it's not a matter of 'if' someone else does. It's just a matter of which one, because someone will, considering who I have to shoot against almost every weekend.

Nice posts Lee....take care and stay safe.....Scott

To the guy that called me a newbie. I think you were just looking at my post count here. Post counts don't always tell the story.

 

[doclu60]

Alright, I will bite.

Is the 1080fps vs 980fps GAIN of wind drift (BC) attributed to a SLOWER projectile a real thing and if so can somebody explain why? Also if there is a GAIN in wind drift (BC) at 980fps then there must also be a gained vertical BC to match it. What's the phenomena that is happening here to create such an instance?

I am delving into the 22LR game now and have never heard of this concept. Can't wrap my head around it due to time of flight and both being under the speed of sound considering both bullets to be identical in form. If some of you are shooting RFBR then I would expect you to be knowledgeable and the concept to be correct or else I am not reading it correctly.

Thanks for any input.

linebaugh,

Kolbe explained the reason in wind drift variation in post #5.

To answer your other question, yes, both vertical and horizontal hold off is effected by the difference in drift. Up, down, right, left is still the same, just to a lesser severity for a lot that shoots good in the wind as opposed to one that shoots not as good in the wind. Example, I have a good flying lot and a hold of low right at 4:00 at 1/8" off the dot is putting them in the middle. Another lot, that doesn't fly good in the wind, same rifle and wind, I may have to hold clear into the 50 ring, but still at the 4:00 position.

Hope this helps.

 

[orkan]

That aspect of one lot doing well in the wind and the next lot not, makes me nuts.

 

[doclu60]

That aspect of one lot doing well in the wind and the next lot not, makes me nuts.

Me too!

 

[BP1]

Me too!

Me three now y’all are gonna make me start banging my head against the wall..