is 2500 fps a no go zone.

[Will]

I don’t recall me saying that it was right.

What I’m trying to do is actually get out there and put rounds down range to come to conclusions.

And I disagree about the velocity being irrelevant. Most of the prs shooters out there today have went to doing a 10 shot load development and use nothing but velocity.

What they look for is those plateaus in velocity where you can load within a half grain of powder and the velocity stays the same.

I have no doubt there are ways to tune a barrel but I believe when shooting cast bullets alloy,engraving pressure, case fill, and and bullet fit outweigh anything else you can do. And the only way to draw these conclusions is to get out there and try different stuff. If I wasn’t stuck at work every day I would be shooting 100’s of rounds a week to acquire more knowledge.

 

[VZerone]

I don’t recall me saying that it was right.

What I’m trying to do is actually get out there and put rounds down range to come to conclusions.

And I disagree about the velocity being irrelevant. Most of the prs shooters out there today have went to doing a 10 shot load development and use nothing but velocity.

What they look for is those plateaus in velocity where you can load within a half grain of powder and the velocity stays the same.

I have no doubt there are ways to tune a barrel but I believe when shooting cast bullets alloy,engraving pressure, case fill, and and bullet fit outweigh anything else you can do. And the only way to draw these conclusions is to get out there and try different stuff. If I wasn’t stuck at work every day I would be shooting 100’s of rounds a week to acquire more knowledge.

Who said velocity is irrelevant? Not me. All I said is it's harmonics for one thing. Do you think that one bullet doing 2200 fps gives the same barrel vibrations as one doing 2600 fps? I think not! There is another vibration called "swell". That is the swell a barrel gets as the bullet passed through it. That too has it's own vibration.

I totally disagree with harmonics tuning not being a vital factor because if your bullets exit the muzzle in the wrong point of the sine wave of vibrations you're never going to get that extreme accuracy!

 

[Ian]

"swell" isn't quite right, either. There is a vibration which travels longitudinally, effectively creating an enlargement of the bore at its peak which affects muzzle diameter, but it isn't created by the bullet....it's created by the initial pressure wave inside the chamber. This wave usually hits the muzzle and goes back to the front receiver ring several times before the bullet exits the crown. You can nitpick any statement to death or find/create exceptions, but simple observations note general trends, and it happens that a lot of us don't generally find happy nodes around 2500 fps, for whatever reason.

 

[VZerone]

"swell" isn't quite right, either. There is a vibration which travels longitudinally, effectively creating an enlargement of the bore at its peak which affects muzzle diameter, but it isn't created by the bullet....it's created by the initial pressure wave inside the chamber. This wave usually hits the muzzle and goes back to the front receiver ring several times before the bullet exits the crown. You can nitpick any statement to death or find/create exceptions, but simple observations note general trends, and it happens that a lot of us don't generally find happy nodes around 2500 fps, for whatever reason.

I'm not going to argue if the bullet swells or bulges the barrel, but the fact that a tuner can tune a 2500 fps load cancels your theory about it being an inherently inaccurate velocity.

 

[VZerone]

I was reading an article about a very knowledgeable man on benchrest shooting. It started about about stiff bolt actions and progressed to benefits, if any, of sleeving an action. He then stumbles upon this thinking about rifle vibrations. He wondered if drilling a hole 180 degree opposition of the front action anchoring hole would change anything. The hole was a threaded 1/4x28 so he drilled the hole atop the action and threaded it. Went out and tested the rifle and there was a mark improvement in the base accuracy. Then he looked further. The rifle had a gas port on the left side of the action. So he drilled the same size hole on the right side. He again tested and found an accuracy improvement. Point being many things affect the vibrations of a action/rifle. They come from many places too, like firing pin strike, trigger sear release, primer detonation, etc.. Made me realize why Remington tried that electronic primer. At any rate the idea is to get the bullet to exit the crown where all the vibrations are as close to the centerline.

 

[Ian]

I'm not going to argue if the bullet swells or bulges the barrel, but the fact that a tuner can tune a 2500 fps load cancels your theory about it being an inherently inaccurate velocity.

I think the fact that it may require a tuner to fix indicates that it is.

 

[Will]

Maybe my goal is different than other but to me I’m not looking to pay for barrel tuning or go to a slow twist barrrel for that matter. I am trying to wring all I can out of a factory 1-10” rifle not buy or tune my way out of a problem. I truthfully believe all of this can be overcome with proper loading techniques, load development, and alloy/bullet selection.

All that’s been said here is that a lot of people notice certain anomalies in the 2500 FPS area that they don’t encounter at 2400 and 2600. Not that you can’t shoot good groups in the 2500 FPS range.

 

[Ian]

You may not be able to easily hit an exactly pre-determined velocity with cast in normal barrels. With me it's more like see what I can get and take what's best in the general area I want.

The take-away from all this is should be that just because you do well at 2400 and push on up to 2500 and see things fall apart doesn't mean that it won't come together again at near 2600 if you have the pressure headroom and the other components are up to the task. I think too many people quit too soon, thinking they have alloy failures or RPM monster is eating them or whatever when it may only be a process of working through a bad place in the harmonics of the particular rifle/load combination. Harmonics is just one thing of many to consider, but it may be a new concept to consider for many who haven't spent much time yet playing in the velocity region where it really matters.......well, it matters at really low speeds, too, actually, but on the discussion boards is often attributed to other things and conceptualized as "finding just the right powder charge" without doing a deeper examination of what that means.

 

[VZerone]

Ian why move on when you can solve for 2500 fps. I'll give you a tip. You can change the bullet weight, understand that?

 

[John]

Back in the previous century I remember Felix Robbins offering the opinion that barrel accuracy nodes ran at 800 fps intervals in most cases with half nodes 400 fps also working, That would leave it over the 2400 fps ideal.

 

[Ian]

Felix offered many useful opinions, including a 22-1/4" barrel length.

 

[fiver]

21-1/4"
I looked through the warehouse story again just this afternoon and seen the barrel length mentioned as 21-3/4"
but that was also second hand reporting, and I brought it up with the O.P. of the thread asking about the tests.

anyway:
much of that test was done with skinny barrel hunting type rifles also, but that information got bogged over by the .00 type numbers from the BR rifles.

 

[popper]

Chronyd that load at 2548 avg. from AR carbine, 168gr cast GC, PC.
Aslo does well @ 200 yds.

 

[Intheshop]

There's a cpl reasons slow twist barrels work with cast..... and thin jacket varmint JB's for that matter..... that prefaces any RPM thing.

First,generally a slow for calibre twist "should" have a shorter throat,making it easier ( more important with cast) to either A- modify bullet nose for a perfect fit...... and B- run a throating reamer in as an alternative(or adjunct)to "A".

Next is the actual leade section of lands,the slower the twist the easier it is on cast at launch...... irrespective of velocity,later in the cycle. Further,even though I firmly load for .000 runout,with ANY twist..... the slower the twist the more runout you can "get away with".

All of the above is like banking money.... you're gonna need that cash back when going after HV. And in some ways,CB's have a slight advantage OVER JB's going after HV from an accuracy "potential". They're easier to get perfectly balanced..... because of 1/2 as many "parts".

 

[Ian]

Interesting that powder coating instantly boosts the accurate velocity potential by a bunch. Even with soft alloys, like 10.4 BHN, I can shoot decent groups at full-power copper jax speeds in .308 and .223. The question is....why?

 

[fiver]

IMO it's in the bullet set back [and probably most of the riveting as a result] being avoided.
look how many of us immediately go to about 2 steps slower powders when wanting to up the speed.
part of it is to help with barrel timing but a bigger part is to give the bullet time to get into the barrel before putting the pressure behind it.

 

[Ian]

I've had an idea for a test rolling around in the back of my head for a while, just haven't figure out the best way to do it yet. Basically it's firing a series of squib loads with and without coating and seeing how far up the bore they each go. Somehow, the idea of hammering 20 or more stuck bullets out of a barrel is highly unappealing to me, but it might confirm suspicions about the coating lowering engraving resistance.

 

[RBHarter]

I think that the problem with that isn't getting the bullet into the barrel , it's letting it stop on purpose . Especially with any kind of a powder charge . 2-3 gr of Unique gets a 62 gr bullet 1200+ out of a 223 and over 900 with a 150 out of a 6.8 .
Maybe a test like this one is a good place for a slick WC .

 

[Eutectic]

Help me out here........ I'm having a heck of a time with 2500fps being an evil number. I see much precise talk on nodes, waves, vibrations, favorite barrel lengths. Yet the criteria is vague as to exactly what fits into this "2500 syndrome"? Are you talking anything and everything is bad at 2500fps? Because if you are you are wrong! I might buy a certain similar group of attributes reacting similar; even twist problems rearing their head. But what exactly reacts bad in specifics? So who is the "causer" of the "2500 syndrome" and what is the "causee" ??

Pete

 

[waco]

Not the best group in the word and there are a couple flyers but this is 10 shots at 100 just 11fps shy of 2500.