"Most Accurate Powder" notes in reloading manuals vs. BOSS

[PipesMac]

Just a topic for discussion I've been thinking on.
Is the "most accurate powder" notation in reloading manuals meaningful, or is it just a reflection of THAT particular test barrel's resonance nodes?

The concept of tuning a barrel to the ammo vs. what we normally do in reloading (tuning ammo to the barrel) has been amply proven and documented by the Browning BOSS, as well as gunsmith's work. The basis of the BOSS is a moveable weight at the end of the barrel that changes the length of the vibrating barrel. When the cartridge is fired, it sends a wave propagating down the barrel at the transmission speed of steel, which reflects back and forth from end to end as well as continues to be generated by the expanding gas in the tube, continuing burn, and travel of the bullet down the tube. The net effect of all these vibrations makes the barrel oscillate in a sine wave, or actually several wavelengths apparently, in a "standing wave" pattern.
If we can get the bullet to exit the barrel just as the vibrating barrel passes through the "zero axis" then we get better accuracy. If we can control the standing wave and make the exit point of the barrel be a "node" that stands still while the barrel behind it flexes up and down, we get better accuracy as the error-angle of a flexing barrel is minimized at the nodes. By changing the position of the BOSS end weight, the wavelength of the standing wave can be moved for a particular load, to the end of the barrel.
This is analogous to what we do in handloading--changing the powder charge, and burn-rate (via different primers for ignition and powders for burn-rate), to make the vibrating barrel hit a "zero node" as our bullet exits. Same physics, just using one of the different variables to effect the barrel vibrations.

All that being said, it is immediately obvious to anyone watching a particular load get "dialed in" via the BOSS system that with a consistent powder giving repeatably small velocity errors from standard, a load/barrel combo CAN be "tuned". Just as we KNOW as handloaders that we can tune a particular bullet/powder combo to our rifle.

So.... since the test rifles used in reloading manuals, say Nosler's for instance, are just one barrel for all the loads, it is my opinion that the "Most Accurate Powder" is a meaningless or at best MOSTLY meaningless datum, reflecting ONLY what powder gave a nice barrel oscillation in THAT (usually looong) test barrel. While it's possible the test barrel was constructed like a target gun to minimize vibrations, we don't know that info, or how much of the remaining error is due to vibration vs. velocity change. But we DO know we can tune away much of the vibration...

What would be MUCH more valuable IMO would be a measurement of muzzle velocity standard deviation, or max deviation, and max spread. This would give a better measure of that powder's REPEATABILITY regardless of whether it was a good match for the test barrel.

Thoughts?

 

[DrMike]

Interesting track. However, when a manufacturer lists a powder (or powders) as "most accurate," it is not directly correlated to accuracy as measured on target; it is a statement arising from the lowest standard deviation for velocity, which is a measure of consistency of pressure generation. Hence, the more correct designation would speak of accuracy potential. A lower standard deviation for velocity is almost always guaranteed to permit building an accurate load as measured by bullet impact. This is done through adjusting bullet seating depth to discover the node in a given platform.

 

[RiverRider]

Whether or not load data publishers' recommended "most accurate" selections are reliable, I dunno. But I have spent a bit of time pondering this whole subject.

At my club, there are a few benchresters including Mike Stinnet, who recently shot the smallest 100-yard group on record, and Ralph Stewart, who also competes and built Mike's rifle. I talk to Ralph quite a bit, and he's told me lots of interesting things about which I won't go into in detail, but that's where some of my insights have originated.

I have not read gun rags is a while, but when I did Rick Jamison was one of my favorites. I think he was the first one to go into bullet seating depth to any extent. At least, I don't recall any of his predecessors writing about it.

I am beginning to think there's more going on than just the vibration of the rifle barrel. That's obviously an important component or the benchresters wouldn't be using barrel tuners which work on the same principle as the BOSS system. There's also the optimal barrel time concept which I think is also viable.

Some who have explored Secondary Explosion Effect have found that the pressure trace actually shows two peaks, one of which is believed to be registered when the bullet engages the lands. The valley between the two peaks has to be detrimental to consistency.

All this taken together leads me to believe that seating depth actually influences the pressure curve such that we can smooth it out and obtain a much more consistent burn, which in turn will augment barrel time consistency and velocity consistency which are essential to tuning a load to the barrel.

I'm not an authority or a ballistician but I've been intrigued by the things I've learned over the years. I am convinced there's a lot more to this stuff than we realize and I find it extremely interesting.

 

[JD338]

As Mike mentioned, "Most Accurate" is the most "consistent" powder.
I can tell you that I have used these powder choices as a starting point and have have much success
in finding an accurate load fairly quickly.

JD338

 

[longrangehunter]

Sierra states that certain powders have been shown to be more accurate over many years of testing in a particular cartridge with a specific bullet weight. I tend to look over the various reloading manuals suggestions and pick something to start with, quickly see if it show promise and if not move on.

When the BOSS first came out my brother bought one from Browning in 270 Win., I later bought a Winchester M70 338 WM with one. I worked with both of those guns and found you'll be tuning another variable rather then just the load, in the end I think I was burning through even more ammo and ditched the whole concept.

I'd rather not have to play with another variable and just develop an accurate load.

 

[RiverRider]

Browning and Winchester published settings for the BOSS system based on bullet weights and factory loads. I know of the difficulties encountered when trying to develop handloads for them, and especially when working with a bullet weight for which no BOSS data exists. For me it the Model 70 in .25-06, shooting 75-grain V-Max and 85-grain Ballistic Tips. I got so frustrated I put the rifle up for sale and set my sights on a new 70 Classic in .25-06, but until the rifle sold I continued to play with it. On the day I finally got it to shoot sub-half inch groups I was offered my asking price. I often wonder how it would have all worked out had I held on to that rifle, but I wanted the new 70 Classic very badly by that time so I let it go. My new one has performed well and likes 85 BTs, so I lose no sleep over it.

Now my neighbor...this guy could fall into a cesspool and climb out smelling like a rose. He bought a used 70 with BOSS in .30-06, and it seems to shoot everything very, very well. I can't say whether or not he consulted BOSS data or not. I think he told me he just set the BOSS to a recommended setting for 180-grain ammo and then went to town. The heck of it is, it was first real handloading project and it all just fell in his lap and now he thinks he's a handloading master. The fact of the matter is he couldn't tell you whether or not Bullseye is faster burning than Re22.

I think the BOSS was a great concept, but it detracts from a rifle's appearance and it DOES add another variable that complicates the load development process tremendously. I guess a tuner of that nature just isn't practical for a sporting rifle.

 

[SJB358]

As Mike mentioned, "Most Accurate" is the most "consistent" powder.
I can tell you that I have used these powder choices as a starting point and have have much success
in finding an accurate load fairly quickly.

JD338

Just did the same with my brother's 257 Wby.. Their most accurate was real close to mine. Luck? Maybe, but they listed it as the most accurate powder, with that bullet as well, I was pretty impressed. There has to be something to it..

It is impressive to see groups like this out of a rifle with only 20 rounds through it and these are the 1st handloads.

 

[SJB358]

I think the BOSS was a great concept, but it detracts from a rifle's appearance and it DOES add another variable that complicates the load development process tremendously. I guess a tuner of that nature just isn't practical for a sporting rifle.

My current 35 Newton was a 338 Win Mag, with a BOSS. It was insanely accurate, just took a little tuning after I developed a safe load at the speed I wanted. Here is one example with 250 PT's

5.2



5.1



5.0



It worked that way with everything. When I first got it, I had the 225 TBBC's as loaded by Federal. I turned it to whatever the recommended setting was for 225's, I remembered it was around 2-2.5". As I turned it, and reshot, it kept getting smaller and smaller, till it started opening up again. Really a neat system. If it didn't look so horrible, I wouldn't have minded it, but they did shoot real nice once you got them sorted out. Really didn't take too much to get them tuned either, no more than a decent handload takes to fine tune.

 

[tim629]

i'm still young & uneducated but with my limited experience the nosler Data has been very good to me both with most accurate powder & most accurate load

with that being said it has only been with one 243 bullet and 2 bullets in the 280ai with probably 2 powders/bullet to choose from so not a huge test group but enough for a new loader like myself to put some faith into the information in the future too

 

[PipesMac]

Interesting points. DrMike hit on my main concern, that the "most accurate powder" should be a measure of smallest velocity deviations, and not results on a target from a particular test barrel. My comments on the BOSS were really just there to illustrate that a particular load DOES interact with a particular barrel/barrel-length in a huge way, and thus "accuracy" of a test load from a test barrel measured from "smallest group" on a target was not meaningful.
If in fact the "most accurate powder" designations I see in the manuals are intended to mean, "most consistent velocity and pressure", then that's exactly what I was wishing would be published. I just haven't run across anything in the manuals that made me think that's what they meant--hope I'm wrong!

DrMike and riverrider both touched on seating depth as a critical element in tuning the load. This is very interesting to me, as I had previously considered this a very small variable and not messed with it much. You guys seem to indicate it has a large impact on tuning the load. The comments on a double spike in pressure and the results of that on consistency are interesting. It gets me thinking, I can see that effectively increasing the barrel length by increasing the distance the bullet has to travel may have the same effect as increasing the barrel length by screwing a BOSS in and out. Previously I thought the distance was so small it would have a negligible effect, but if bullet seating depth is a sizable portion of barrel vibration wavelength then it would have a big effect. Also supporting that is the fact BOSS length changes are very small and on the same order.
I haven't played with seating depth much at all due to being "magazine limited". The .284 Win has a COAL of 2.8", and my Browning Abolt magazine will let me only go to 2.93" and still fit in the mag. The rifle action and chamber would let me go longer. When I first started reloading, I read that putting the bullet close to the lands generally resulted in more accuracy, and it would also allow full powder charges in my short case, so I just went with 2.92" COAL and haven't changed it.
Has your experience been that bullet seating depth is a variable worth playing with? And do you do this AFTER finding a good powder charge that your barrel likes, as a "final" tweak to the load?
Like RiverRider, I love reading and thinking on this... thanks for any more thoughts on the topic!

 

[SJB358]

Has your experience been that bullet seating depth is a variable worth playing with? And do you do this AFTER finding a good powder charge that your barrel likes, as a "final" tweak to the load?
Like RiverRider, I love reading and thinking on this... thanks for any more thoughts on the topic!

Without a doubt! I will find the most accurate charge, then tweak seating depth, others do just the opposite, but finding the most accurate and consistent charge first, seems to make finding the most accurate seating depth easier, at least for me.

Mike taught me long ago (along with many others but he drilled it into my head first I think), that you find the load that is most consistent and your likely very close to finding a load, with very little tweaking to seating depth.

I have found more often than not, seating depth matters a bunch. With a few of the common bullets on my shelf, some don't look very hot till they are backed up off the rifling a bunch, very few like to be snugged up close. This is AB's and the ABLR's. The BT's and PT's seem to like being closer to the rifling, but none of my loads are within .025" of the rifling, most run around .040" or so away.

If your mag doesn't allow much movement, you'll just have to "tune" the powder charge, but an accurate node is there. The trick to find that load that doesn't care if your couple of 1/10's off to either side. If you can get right in there, you'll see the rifle will shoot well all the time.

 

[RiverRider]

Like RiverRider, I love reading and thinking on this... thanks for any more thoughts on the topic!

Excellent, Pipes. It seems not many are willing to step out on the thin ice of speculation where speculation is just about all there is to discuss. I'm willing to kick just about any old tin can around if there's someone else who'll kick it back my way now and then.

 

[Oldtrader3]

There has been a lot of negative pushback against BOSS over the 17 years that it has been commercialized. Like most technical subjects, once a person has formed an opinion, considered, tested the theory or not, they are not likely to change their opinion any time in the future. My own feeling is that the scientists at Browning and Winchester who did the work to develop the patent (#5,698,810) and prove their thesis were correct. If you read the patent, there is a determinant length of barrel where a distinct improvement of that rifle's accuracy can be statistically proven and be repeated with the same results using the BOSS to optimize accuracy by controlling the length of vibration node as written. Usually there is only one optimal node per load. All of my BOSS equipped rifles were 1/2 MOA rifles with my tested and optimized loading for that rifle.

I have owned (2) Winchester and (3) Browning BOSS equipped rifles and still own a Sporter, .30-06, Model 70 produced and bought by me in 1996. In developing load for these rifles, I normally used a well proven and accepted load for that caliber which was published and widely accepted by shooters historically to be an accurate load. I usually only tested two or three powders and maybe two bullet weights to develop a working accuracy load for my BOSS rifles. These rifles were in calibers: .243 Win Browning A-Bolt, (2).280 Rem's, Browning A-Bolt & Win Mod 70, .30-06, Win 70 and .338 WM, Mod 70.

I still have the .30-06 Win Model 70 and my grandson the 280 Rem, Browning A-Bolt, both of which will shoot 1/2 MOA, 5-shot groups to 300 yards with the correct setting and load.

 

[elkeater2]

One of the things I don't savvy is why several of the component producers, including Nosler, still publish data for W760 and H414 which is considerably different for the same cartridge and bullet. Hodgdon insists the powders are identical. It should be no more than lot to lot differences, but a guy doesn't know what data to trust.
EE2

 

[RiverRider]

That's interesting, Charlie. I've never been a BOSS skeptic, but I did discover that finding a setting for the device on your own could be nigh impossible. I kinda wish I had kept mine because I'll always wonder if I really DID hit the jackpot on that last day I owned it.

 

[Oldtrader3]

RR, I used the BOSS caliber tables from Browning to find a starting point for each rifle. Then I would run up and down in .3 increments on the BOSS scale to see what direction my 3-shot groups were going. Usually within 3-4 increments on the scale, I would find a node that pulled the group in dramatically. You can optimize from there by going up and down another 3 single hash marks and usually hit the mark where you want to be. The rifle will give you some hints as well. It has never taken me mo-re than 2 range sessions to optimize any particular BOSS rifle. Once you find the spot, you are there.

 

[RiverRider]

Yes, I realize the charts are there and provide a guideline that should simify the process, but in my case I was wanting to shoot 75-grain bullets in a .25-06. The charts are different between the A-Bolt and the 70, I believe, and the Model 70 chart contained only two bullet weights (117- and 100-grain, I think)...at least, that's all I could locate on line.

I may have recorded that setting I used on the last day I owned my 70 BOSS, just in case someone wants that info.