trickled vs. thrown - data?

[murf]

the bullet going down the barrel changes the frequency of the barrel vibration, like a finger on a guitar fret changes the pitch of the guitar string.

the shoulder is the pivot point regarding rifle recoil and muzzle rise. change the point, change the rise.

just trying to use analogy and a bit of science to understand the discussion. how did I do?

murf

 

[spitballer]

Actually makes more immediate sense but probably make much difference with my 22 caliber rig. Walkalong's advice probably more applicable.

 

[ASCTLC]

Interesting discussion here! I'm back after a couple years falling on hard times and setting up a new rifle (30-06).

Shooting Federal Premium 180gr Partition is minute of cereal box. Not confidence inspiring to say the least. This sets a mind set I don't need when I put an elk in my scope.

So far, I found a sweet spot at 56gr I4350 pushing a Nosler Partition Protected Point. Significantly better than 55.5gr and 56.5gr.

I'm measuring each round all the way to the last tiny pellet of powder just to ensure nothing is left to assumption.

So my interpretation here is an effort of mine to load 55.7, 56, and 56.3 gr test rounds are likely to be a waste of time. I'm at 3/4 MOA and that's considering I'm not a very good shot. Good enough for elk but I still have my nit picky side to know I've done the best I could with the load I settle on for that bullet.

Am I getting this right?

Thanks,
Andy

 

[Walkalong]

Some people sight in on a bench with different shoulder pressure/location than they will use hunting and then wonder why the POI is different.

 

[Bart B.]

murf,

Bolt action rifle barrels are typically fixed at their breech end only. They vibrate and whip exactly like a fishing rod held in ones hand.

Guitar strings are fixed at both ends. When one's pressed between the frets, there's now two guitar strings; one from each end to where the finger's pressed it against the neck. One vibrates a lot at one frequency as it's plucked. The other doesn't vibrate at all.

A rifle barrel weighs several hundred times more than the bullet does. That part of a vibrating guitar string weighs several hundred times less than the force of the finger on it.

Two completely different vibration shapes and frequencies. That of the barrel is well shown in posts 45 and 47 where links to them are shown. A free floating barrel vibrates at the same frequency and various harmonics thereof every time its fired. Here's the resonant frequency of a standard weight 2.8 pound sporter 30 caliber barrel, 24 inches long with a 1.1" diameter, 1" long reinforce shank, then a reinforce taper for 3" down to .9" diameter, then tapering 19" to a .6" diameter muzzle. It extends 23" out from the receiver:

Breech end fixed, 74 Hz. Breech and muzzle end fixed, 278.7 Hz.

Barrels with pressure points anywhere on them from any external item (bedding pad between barrel and fore end or barrel clamp) will vibrate differently depending on the amount of pressure at that point. If the barrel bounces free from that point, it will change its vibrating shape and often its frequencies, too. Which is why bedding pads degrade overall accuracy and a totally free floating barrel vibrates the same for every shot.

 

[243winxb]

just trying to use analogy and a bit of science to understand the discussion. how did I do?*

Off key.

 

[Bart B.]

ASCTLC,

For ranges up to 300 yards used to develop a load, I think whole grain increments are small enough. Fractional parts of a grain for charge weight increments don't change group sizes enough to not be masked by the shooter's abilities and that of a hand held rifle. If one can shoot their stuff no worse than 1 MOA (that's the size of the biggest groups shot) with at least 10 rounds per group, then they can try half grain increments.

I've wore out several 30 caliber barrels and shot a lot of reduced loads for short range matches. Charge weights in even grain increments from 41 to 43 grains of IMR4064 under Sierra 168's or 40 to 42 grains of it under Sierra 180's showed the same good accuracy through 300 yards shooting many 10-shot strings in matches; both slow fire once a minute and rapid fire with 10 shots in one minute.

If your barrel starts waking shots away from point of aim as it heats up, you need the patience to let it cool down between shots so enough can be fired to realistically show its accuracy with any load.

 

[murf]

thx for the detailed explanation, bart b.. i'll only fret the pressure points from now on!

walkalong, what about the shape of the bottom of the stock resting on the rear bag? most stocks are angled with respect to the bore axis. won't this have a negative affect on accuracy due to the back of the rifle dropping (and, therefore, the muzzle rising)under recoil? won't different velocities (and, therefore, varying amounts of recoil) enhance vertical stringing in this case?

murf

 

[ASCTLC]

Thank you Bart. That saves me a ton of work that I don't have time for. I'll fire off my rounds already made up and simply run with the one I find most accurate.

I quickly found 1/2 MOA for my 150 gr Nosler Ballistic Point (green tip) for pronghorn at 58gr I4350.

Interesting thing is, both these loads are right at .5 gr down from max listed in the Nosler reloading manual.

Andy

 

[W.E.G.]

Many thanks to those who have participated in this thread.

Especially to Bart.

I opened this thread because I am in the process of deciding whether to use Varget or TAC for a new White Oak Armament upper.

My concerns came from some data I collected that showed a pretty sizable Extreme Spread (especially with TAC).
I fired all rounds over a Chrony Beta Master.
Rifle was fired from benchrest position with forearm resting on a towel atop an ammo can, butt seated snugly (no sling used) in shoulder of Creedmoor shooting jacket.

I was going to crunch all the numbers, and put the data in a neat, easily-readable spreadsheet. But, about an hour into the data-input (using Excel) I got pretty frustrated with what I was seeing (large E.S. and S.D.) and kind of threw up my hands.
With 115 FPS extreme spread (TAC), that will get me considerably more vertical dispersion than the width of the X-ring at 600 yards.
2739 to 2854.



Below is the full set of "raw" data.

My scribble may be more legible than intelligible.

"WOA2" is a used White Oak upper with probably around 2800 rounds down the pipe.
Assume it has the Wylde chamber.
Bought it used on the USrifleteams forum.

"WOA3" is a brand SPANKING new upper from White Oak.
I'm sure it has the Wylde chamber.

Tested Sierra 77's and 80's.
As a reference, I also shot just a few rounds of Black Hills "Blue Box" 77-grain factory loads.
Indicated as "BHBB" on the scribble.

The used upper shot significantly slower than the new upper.
Don't know whether velocity of the new upper will drop off with age.

TAC DATA



VARGET data



Charges all thrown (not trickled) with Redding Competion Model BR-30 measure.

 

[Bart B.]

ASCTLC,

If you quickly found 1/2 MOA for your 150 gr Nosler Ballistic Point with 58gr I4350, was that just one group shot with that charge weight? Or what several groups all shot inside of? Any load recipe has the potential to shoot a very tiny group; once, but all the others will be larger. Statistically speaking, the worst thing one can do testing loads is picking the one that shoots one group of a few shots smaller than all the other loads tested with one few-shot group. You're rolling dice and basing their usefulness in shooting craps with one roll of them that just happened to end up snake eyes. Doesn't matter that the odds are in favor of getting seven the most often and getting box cars just as often as snake eyes.

When the .30-06 was "the" round for high power match rifle competition, IMR4350 powder only gave best accuracy with 190 or 200 grain bullets. Winners and record setters using 150-gr. bullets for short range matches used IMR4064 or IMR4895. They picked their powder choice based first on what produced the best accuracy. That's the opposite of how most people pick their powder; they want the stuff that produces the highest muzzle velocity and that's what they test with. I don't know of any cartridge that shoots most accurate with the powder that shoots a given bullet the fastest.

At .30-06 velocities in a hunting environment, is an extra 50 to 100 fps in bullet speed more important than a half MOA of accuracy?

W.E.G.,

If your 22 caliber barrel had 2800 rounds through it when you got it, that's about the round count that similar size 22 caliber cartridges' barrels used in benchrest rifles get replaced. Their accuracy has worsened by about 50% and no longer competitive. For hunting rifle accuracy, that barrel's only about half worn out; one third worn out for military service/combat use.

 

[Walkalong]

walkalong, what about the shape of the bottom of the stock resting on the rear bag? most stocks are angled with respect to the bore axis. won't this have a negative affect on accuracy due to the back of the rifle dropping (and, therefore, the muzzle rising)under recoil? won't different velocities (and, therefore, varying amounts of recoil) enhance vertical stringing in this case?

Yes, for most stock designs getting back on target vertically was accomplished by pushing the gun back forward bringing the cross hairs back down. Many shot free recoil to eliminate shoulder & gun holding error. Bags were slick and we used baby powder to helps things slide even better. Light slick resistance is easier to duplicate with a smaller error/spread than heavy, same for light vs heavy neck tension. Very light neck tension was 90% of the reason the bullets were generally loaded slightly into the lands, to get that good start pressure/burn you need. I used my shoulder and very light contact with the stock with my trigger hand. This all has to be replicated almost exactly each time, especially the resistance to rearward movement under recoil, but side to side pressure with the shooting hand as well. Even as light as it was it could cause error. Recoil did not lift the rifle, but did slide it back raising the muzzle due to stock design. There are now BR stocks with basically flat stocks and getting back vertically on target if needed is accomplished other ways. Most also had fine screw adjustment on the rear leg of the rest. I fine tuned vertical with mine after pushing the gun back forward to hopefully the same exact spot each time. You could put forward stops on the front rest to help with this.

When it comes to precision shooting, there is no one answer for accuracy. It is always a combination of things that must mesh together.

 

[Bart B.]

murf,

walkalong's right about stock shape effecting where the barrel points as the rifle recoils. But it's very repeatable from shot to shot.

Different loads do the same thing but only put group center higher or lower relative to the aiming point. Their size often doesn't change as long as muzzle velocity spread's the same. Muzzle velocity spread's always smallest with free recoiling (or fixed mount barreled actions). Only when one holds the rifle against their shoulder does that spread get bigger. None of us humans are all that repeatable doing that.

Sierra Bullets uses the same charge weight for a given powder and bullet testing their stuff for accuracy. Even when changing lots; they don't work up test loads for any component change. That's about the same difference a half grain or more powder does within the same lot of powder.

One other thing that helps a load shoot tiny groups at any range. If the bullets exit on the muzzle upswing at the right place that the angle compensates for velocity (slower ones leaving at a higher angle so their greater drop puts them on top of faster ones leaving at a lower angle), best accuracy happens. When that happens at longer ranges, accuracy a medium ranges isn't quite as good. The difference at short ranges may not be seen.

 

[Walkalong]

. But it's very repeatable from shot to shot.

Yep, or they would never be able to shoot those tiny groups. The shoulder is a prime suspect anytime there is vertical stringing, but it can also cause side to side error.

 

[W.E.G.]

Tested the three lots yesterday.

600 yards at Cumberland.

Virtually NO WIND.

As I would have expected, each load "shoots better than I can hold" (with iron sights).
So much for fretting over differences in "extreme spread" and such.
I know "physics is phsics" and all that, but shooting is shooting too.

80SMK fired out of nearly brand-new Holliger (Wilson barrel) service rifle upper.
All seated to 2.400"

First string
Varget 24.4 grains - score 187

Second string
TAC 24.2 grains - score 191

Third string
R15 24.4 grains - score 191



The 7's were all out in the same place - wide right.
I shot 'em there.
Not as many as I used to though.
Still working on the cure.

 

[Lee S. Forsberg]

If trickling to an exact charge builds more confidence in the handload cartridge then do it.

 

[wanderinwalker]

The 7's were all out in the same place - wide right.
I shot 'em there.
Not as many as I used to though.
Still working on the cure.

In my experience the solution to those fliers is a winter of 50-foot smallbore prone. Followed up with some sessions at the 100-yard line with the same smallbore rifle when the snow thaws. After that, 600 with a Service Rifle is easy if there's no wind.

Back to the trickled versus thrown, I don't believe it makes enough of an impact with a Service Rifle to be worth the time spent trickling. But I also refuse to countenance a load that is so finicky is has to be at an exact tenth of a grain to shoot well. A good performing bullet/powder combination should shoot well within a window of charge weight, just as a good barrel should perform with a number of combinations .

 

[GBExpat]

Currently, and for the last ~6 months, I have only been loading handgun cartridges, so I will confine my response to those.

I only trickle when crafting Load Test Strings and early in a new setup for testing when making a QTY of rounds (LCT + Auto-Disk/ChargeBar & 2cellphone vibrators attached to the powder reservoir).

One thing that I noticed long ago was that, with the handguns at relatively short range (~7yds), whether the MV varies due to the changes being slightly inconsistent and/or propellant positional sensitivity, it doesn't seem to have any real effect on the POI.