I found the previous thread interesting. I would like to pose the same question without the aspects of hunting and it�s requirements for impact energy and bullet performance. Let�s just cut paper for now. As I read and learn, a few things seem not to jive. Here are some basic "reloading truth�s" I have picked up along the way. #1- Accuracy is repeatability. Accuracy is effected by barrel vibration. The most accurate load is one that exits the barrel as close to center or midpoint of the muzzle swing as possible. #2-Benchrest accuracy is improved by creating loads that completely fill the cartridge with little or no space between powder and bullet. They make shorter cartridges to accomplish this. Can it be that some that load to max velocities are gaining accuracy not from the speed but because they are "filling" the case with powder just as benchrest shooters do? And that the velocity is incidental to the extra powder needed to fill a factory case? Velocity seems to be a wild card to me. It does not fit with barrel vibration or I am missing something. JB

The statement: "The most accurate load is one that exits the barrel as close to center or midpoint of the muzzle swing as possible." isn't true. What you want is for the bullet to exit the muzzle when the muzzle is relatively stable. In its centered position, it will be moving violently from one extreme of the harmonic to the other. Actually the center position is probably the worst possible place for the bullet to exit the muzzle since the muzzle is moving through that area the fastest.

Have you ever seen a diagonal string on the target? Usually that is caused by a load that is putting the bullets out the muzzle in the center of the harmonic whip cycle.

The best place for the bullet to exit the muzzle is on either end of the "ellipse" of the harmonic whip (some barrels probably don't whip in an exact ellipse or "infinity symbol" pattern, but the idea is still the same). Here is where the barrel whip slows down just before changing directions. It is during one of these moments that you want your bullet to be released from the muzzle.

What you're talking about with regard to powder filling the case is refered to as load density, and you're right, normally the higher the load density the more consistent the powder burn. The most probable reason for this is that when load density is low, the powder can "pour forward" away from the primer, and ignite in an inconsistent fashion. It is generally believed that a full powder column will burn most consistently and therefore give the best accuracy.
I think this is basically true, but you do reach a point of saturation. Where that point is depends on the cartridge, bullet, and powder being used.

If you're interested in a reliable way to create what I refer to as an "optimal charge weight" load, go to this link and read the process. Loads developed in this manner are far more likely to be universally good performers in a number of rifles. You need only to alter bullet seating depth in most cases to get onto the "harmonic node" of the barrel.

Here's the link:

http://www.loadyourown.com/ubb/Forum11/HTML/000276.html

Since you're interested in repeatable, consistent performance from your rifle, you may find this link interesting.

What you suspect about accuracy actually improving as load density and velocity are increased is true in most situations. My own experiments regarding my OCW load development method have shown me that somewhere near the maximum load density you'll find an area where a 1% increase or decrease in powder charge affects the load's performance very little if at all.

That's the kind of load you're after, and I explain why in the link I mention above.

Take care,

Dan Newberry
green 788

Dan, of course you are right about the barrel movement. My mental picture of the movement of the muzzle is more like a sloopy symbol for infinity or a flat oval than a pendulem because of the helical forces of the twisting bullet so I infered that a center point would be / would be crossed twice. I will look into the data you recomend. I am not a "max" loader and I want to develop acurate loads that match each gun and I don't think velocity is the only or main consideration. Thanks, JB

Green 788--

Read your bit about picking the optimum load. Nice piece of work!! Whether you know it or not, you've overcome a huge statistical hurdle in developing accurate loads.

Most people do not realize that a .5" and a 1.5" five shot group at 100 yards are statistically indistinguishable. Tests of variation are notoriously weak. People go to the range, shoot a good group, switch ammo, shoot a bad group, and think it is the ammo, when it could as easily be just random variation, with no real change in performance. You can't tell, until you shoot a lot of groups.

You have converted the problem to a test of means, which are statistically strong. You have also gone for a "robust design", which means that your solution is relatively immune to changes in the input variables.

From a theoretical standpoint, you've got a much better solution than what we've had. Good work!

Denton, thanks so much for the kind words. I think it's pretty hard to teach old dogs new tricks (I guess I'm in that boat as well), but folks who've tried this load development method have reported good results. The key is in being able to determine where the best load density for the powder being used will be, and trying to choose a starting and ending charge that will encompass the optimal charge.

And as mentioned in the text from the link, the best thing about such a load is it is largely resistant to component lot variations, and will also have a higher level of outdoor temperature resistance--even on powders that aren't particularly temperature stable.

Thanks again, and stay in touch,

Dan Newberry
green 788

Dan, of course you are right about the barrel movement. My mental picture of the movement of the muzzle is more like a sloopy symbol for infinity or a flat oval than a pendulem because of the helical forces of the twisting bullet so I infered that a center point would be / would be crossed twice. I will look into the data you recomend. I am not a "max" loader and I want to develop acurate loads that match each gun and I don't think velocity is the only or main consideration. Thanks, JB

JBMauser,

One thing about accuracy and that is, there are heaps of exceptions.

But these are some general things I have found.

Firstly, rifles with suspect bedding and also barrels that are nor as good as the might be, often give the best accuracy with low pressure loads and using powders that are slow for the caliber. I think this is one reason why many 416 Rigby shooters get good results as they are loading back with slow powders.

Secondly, if the bedding and barrel are spot on, calibers with big case cpacities for the bore size like 264 Win, 7mm Rem etc. retain accuracy to higher pressure levels than is the case for calibers with small case cacpaities for the bore size such as 308, 30/06 and 375 etc.

Thirdly, when using Winchester ball powders like 748 and 760, best accuracy usually comes from a load that isa full case of powder but not real high pressure. Examples being the 308 with 130 grainers and 748 and 375s with 760.

Fourthly, when bedding and barrel are spot on and when using Dupont or the Australian made Hodgdon Extreme powders, best accuracy will often come with loads from faster powders for the caliber, such as Varget in the 270 with 100 or 110 grainers, 30/06 with 150s etc.

Lastly, some bullets just seemed to shoot. Examples would be the 130 grain Speer Hollow Point in 308, 100 grain Speer Hollow Point in 270, 300 Hornady Round Nose in 375 and 500 Hornady round nose in 458.

I don't think I can remember ever seeing an accurate 270, 308, 375 or 458 or 460 Wby that would not shoot well with those bullets and do it with lots of loads.

Mike

[ 08-19-2002, 04:20: Message edited by: Mike375 ]

Mike, so what you are saying if I can restate your information in Barrel movement is that a poorly bedded rifle which would have distorted or dampened harmonics does better with a lower pressure load which makes sense if the barrel has more bounce against the pressure point than a well bedded barrel would move about to it's own rhythm and take a higher pressure - velocity load. And what I think you are saying about bullet weight is that there are some combos of pill weight to caliber that seem to yield favorable overall results. That one I know has proof, but I don't understand it. I know some bullets just fly well like 168grbt ,30 but their path is struck by the barrel harmonics and that should vary from thin barrel to thick barrel long and short. This is my swamp. Here is where I get stuck. If every barrel is like a tuning fork so to speak, you rap it hard or soft it will vibrate with the same pattern bedded or not just a wider swing. A change in bullet would be a hard wrap or soft wrap. So each barrel should have a bullet/load combo that one can tune to exit the barrel at the same point each time (hopefully) and it should be unique to each barrel. Not each caliber. Or load to bore diameter. But it appears it does. Still a bit confused. JB

JB -- I think you have a real good picture of the accuracy of barrels. I shoot and have shot lots of barrels. The good, bad and the ugly. My experience is you have to shoot the rifle enough to find the combo of bullet-powder-primer-case-load that the barrel likes to have good accuracy. That may be easy or it may be impossible, it all depends on the barrel. The experts say the barrel is 90% of the accuracy. Starting with a good barrel you should be able to shoot it enough to find that bullet it likes. All this is assuming you reload. I shoot some rifles that like every bullet I put through it, ranging from expensive custom rifles to cheap off the shelf rifles. I have an old off the shelf post 64 model 70, push feed Winchester .300 Win mag, that likes everything I have ever shot through it. It has never seen a gunsmith and will shoot one hole groups for me and my son and grandson with a 180 gr. Nosler Partition at 3100 fps just like clock work. I also have shot some very expensive custom rifles that took much work and hundreds of bullets to achieve the same accuracy, with maybe one bullet size. My old teacher in shooting and reloading always said the barrel is the key, if it is good, then you have a chance to find the right combo that will achieve good accuracy. The bench rest boys spend big money to get that good barrel, plus all the other techniques they imploy on top of the good barrel. One last point is the shooter. I have a buddy I have shot over a dozen rifles for. He can't hit that good group for accuracy with the same rifle I handed to him that would shoot a one hole group for me, if his life depended on it. I have another buddy whose eyes are apparently the same as mine, I can zero his rifle and he will shoot the same group in the same place. The buddy that finds that elusive shooting skill a mystery is still looking for that perfect rifle that he can shoot. Good shooting.

JBMauser,

The problem dud bedding causes is that things are not the same for all shots. In other words it is like you hold the tuning fork at different points and so change its frequency.

I have no idea why a dud barrel or bedding often shoots with backed off loads.

It is not a recoil issue as a 375 or 458 with backed off loads still has far more recoil than a 270 etc.

The bad barrel seems to alter not just the amplitude or frequency of its vibration but also the pattern of the vibration.

A very good barrel or a "hummer" as we sometimes call them usually shoots quite well with bedding that is not so good and also with a large variety of loads. The biggest difference between a good match grade barrel and an ordinary barrel is not so much in the smallest group it might shoot but that with the match grade barrel the difference in accuracy between its best and worst loads is not nearly as great. Also match grade barrels in well bedded rifles are far more likely to put shots from a clean cold barrel, hot barrel or a barrel with cold hard fouling into the same group.

Mike

Mike, those are all good points. Excellent information.

I might add that some rifles presumably shoot better with lighter loads because of uneven lug engagement of the bolt. One lug bears most of the weight of the charge, and the one which isn't engaged then slams itself against the receiver. With lighter loads there isn't enough pressure to force the short lug to bang home.

The above is the contention (and a sensible one this time) of one John Barsness in Rifle Magazine.

My Remington 700 ADL (30-06) had uneven lug engagement. One lug was barely even touching. I could get decent accuracy from a light charge of IMR 4350 and 180's, but when I pumped 'em up, groups went to hell. It was then that I checked lug engagement. After lapping the lugs and getting even engagement, groups with heavier charges (some even over published maxes) are well under MOA.

Dan Newberry
green 788

Dan,

That is a good point about lug bearing, never thought of it but it could explain it.

Another issue, especially with lower velocity loads with slower powders, is slower but steadier bullet accelaration.

A example would be the 416 Rigby loaded to 2400 with 100 grains or so of Re 22 or similar and the 416 Taylor at 2400 with much higher peak pressure and perhaps 70 grains of powder.

I would bet if you chronographed both with 2 or 3 inch barrels, the 416 Rigby load would be going much slower. Kind of like reaching 200 mph at the end of the quarter mile but with even accelartion all the way down.

I definitely know that it affects scopes. For example, 458s loaded to full power with 500 grainers seem much harder on scopes and mounts than is a 460 Wby loaded around 2100 with much lower pressure loads.

Mike