Getting the Best Precision and Accuracy from Berger VLD bullets in Your Rifle

L.Sherm

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Results are what matters and by saying thers only one way is wrong.
The guys who are showing how they " tune" there rifles are very good, there results speak for there accomplishments are they telling you everything they do H$$$ no but there giving people the basics and by me listening and learning and watching what they do has helped me tremendously. People need to do more testing for themselves instead of asking for all the answers because what works for somebody certainly hasn't worked for me all the time.
Its why I hate posting groups im really never satisfied im always trying to learn to shoot better, reload better. etc.
Theres a few things I know for a fact tuning at 100-300 is different than 500 and beyond occasionally a 300 yard load will shoot good at 500 and beyond but not very often. Ive had to many 100 yard. very good groups fall apart at 500.
 

Mikecr

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@Mikecr -- is it worth trying a few powder charges before doing a seating depth test to make sure I'm not at a powder tune sweet spot?
I believe the most important part of this is that you are not attempting large/coarse seating adjustments from a powder node.
You can use any powder/load that will send the bullets.
Ideally you would be at a bad powder load, throwing big ~1" groups. Then large seating changes may open up 2" or close to 1/2" etc.
I adjust a charge to cause ~100fps below an expected node..

I can back off like this and do coarse seating testing anytime I want. So if powder development brings me to suspect my bullet seating charge was not ideal, then I can go back to a different charge and reconfirm full seating testing. Then go right back to my good powder node and tweak seating for tightest group shaping again. This is what I would do with a bullet change/new lot of the same weight.
 

Unclenick

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A couple of points. One is that the Berger paper is about the original secant ogive VLDs. The newer hybrid ogive bullets start out tangent and switch to secant. This provides the more forgiving tangent contact point, which is less choosy about seating depth, and the higher BC secant ogive over most of the rest. It should be expected that your tests may be harder to get a good indication from with the hybrids.

Second, if you look at the 1965 published research by Dr. Lloyd Brownell and funded by DuPont at the U of M, you see his measurements on the effect of bullet seating depth on pressure has a peak when the bullet contacts the lands and that this backs off as you seat deeper, then starts to rise again as you go deeper still. The pressure value is dominated by the amount of gas bypass around the bullet until it is so deep no further space between the bullet and throat allows significantly more bypass. Seating deeper starts raising pressure again by taking away from the powder space in the case. So when you seat bullets to different depths, you are not only changing the bullet's experience getting down the bore and how it aligns and how much of a gas cushion it has around it, but you are also changing peak pressure, and with it, barrel time.

That all means, when you adjust seating depth, you are not only adjusting pressure and jump, which affects where a velocity ladder flat spot might lie, but you are also are adjusting the timing of the bullet exit which will affect whether the bullet exits at a favorable phase in the whip of the muzzle from recoil moment and pressure distortion effects (see Varmint Al's analysis work on Esten's barrel tuner.

The bottom line is, by changing seating depth you are changing two and possibly three variables at a time, hoping to run into a place where you achieve a coincidence of velocity and muzzle whip flat spots as well as of what tends to make the bullet feed into the throat with best alignment and consistency. The trick to sorting that out requires firing a matrix of at least two variables, and possibly three. The bottom line is, shoot a powder charge ladder at each of the seating depths suggested by Berger (closer spacing for shorter ogives, greater for longer ones, as the long ones have to move more to yield the same change in the size of the annular gap between bullet and bore that determines gas bypass), looking for a velocity flat spot. Then shoot groups from the middle of the velocity flat spots for each loading depth. See which one shoots the smallest groups. It will be the one closest to the optimum muzzle whip barrel time. Then you can look at tweaking either side of the best point or between the two best if they match and are adjacent. And good luck. It's a lot of work.
 

Mikecr

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It is not a lot of work. Seating testing is not tuning.
Optimum seating, and tuning, must be separated as independent and different.

If you attempt full seating testing from a powder and barrel node -your test is failed for the reasons stated.
That's what most did before this Berger recommended testing..
 

Unclenick

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You lost me, Mike. Why are we testing seating depth if not as a step in helping to tune or match loads for the rifle?
 

Mikecr

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In a general sense;
While off-the-lands(OTL), best seating depth is about best bullet-bore interface.
It's a coarse prerequisite, similar to best primer, that has nothing to do with tune.

Powder is your tuning adjustment, and it's fine right to the kernel.
That's not to say that you won't collapse a tuned powder load with a bunch of seating changes. You will.
You need to steer clear of that with seating testing, so that seating (itself) is more purely in view.

Picture a ping-pong ball fired into a lexan bore with an airgun. Under high speed camera you could see the ball rattle around a bit on entry -for some starting distances. But for certain distances, the ball slips right into bore smooth as ice (very consistently).
That's what full seating testing finds.
Best CBTO.jpg
 

Unclenick

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I think we are discussing a terminology usage distinction. You say not tuning, I say coarse tuning. You say tuning, I say fine-tuning. As to the ball, while I am sure you will find one or more sweet spots for the air pressure and flow rate involved, I am not sanguine it will be in the same place at all pressures and flow rates, especially not if the initial gas introduction rate fails to match. But I am prepared to be proved wrong.
 
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pony doctor

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Berger Bullets' Eric Stecker has just made available a tech bulletin in Word format.

You may download it here to save it one your own computer or read it online.



Getting the Best Precision and Accuracy from VLD bullets in Your Rifle

Background

VLD bullets are designed with a secant ogive. This ogive shape allows bullets to be more efficient in flight (retain more velocity = less drop and wind deflection). While this result is desirable for many rifle shooters the secant ogive on the VLD bullets produces another result in many rifles. It can be difficult to get the VLD to group well (poor accuracy).

For years we encouraged shooters to use a base of cartridge to end of bearing surface OAL (I will use the term COAL to represent this dimension) which allows the VLD to touch the rifling or to be jammed in the rifling. This provided excellent results for many shooters but there were others who did not achieve top performance with the VLD jammed in their rifling. These shooters were left with the belief that the VLD bullets just won’t shoot in their rifle.

Other groups of shooters were discouraged by our recommendation to touch the rifling. Some of these shooters knew that at some point during a target competition they will be asked to remove a live round. With the bullet jammed in the rifling there was a good chance the bullet will stick in the barrel which could result in an action full of powder. This is hard on a shooter during a match.

Yet another group of shooters who were discouraged by our recommendation to touch the rifling are those who feed through magazines or have long throats. Magazine length rounds loaded with VLDs could not touch the lands in most rifles (this is the specific reason that for years we said VLD bullets do not work well in a magazine). When a rifle could be single fed but was chambered with a long throat a loaded round that was as long as possible still would not touch the rifling.

Until recently, shooters who suffered from these realities were believed to be unable to achieve success with VLD bullets. Admittedly, we would receive the occasional report that a rifle shot very well when jumping the VLD bullets but we discounted these reports as anomalies. It was not until the VLD became very popular as a game hunting bullet that we were then able to learn the truth about getting the VLD bullets to shoot well in a large majority of rifles.

After we proved that the Berger VLD bullets are consistently and exceptionally capable of putting game down quickly we started promoting the VLD to hunters. We were nervous at first as we believe the VLD needed to be in the rifling to shoot well and we also knew that most hunters use a magazine and SAMMI chambers. Our ears were wide open as the feedback was received. It was surprising to hear that most shooters described precision results by saying “this is the best my rifle has ever shot.”

We scratched our heads about this for awhile until we started getting feedback from hunters who were competition shooters as well. Many were the same guys who were telling us for years that the VLDs shoot great when jumped. Since a much larger number of shooters were using the VLD bullets with a jump we started comparing all the feedback and have discovered the common characteristics in successful reports which gave us the information needed to get VLD working in your rifle. We were able to relay these characteristics to several shooters who were struggling with VLD bullets. Each shooter reported success after applying our recommendation.


Getting the Best Precision and Accuracy from VLD bullets in Your Rifle

Solution

The following has been verified by numerous shooters in many rifles using bullets of different calibers and weights. It is consistent for all VLD bullets. What has been discovered is that VLD bullets shoot best when loaded to a COAL that puts the bullet in a “sweet spot”. This sweet spot is a band .030 to .040 wide and is located anywhere between jamming the bullets into the lands and .150 jump off the lands.

Note: When discussing jam and jump I am referring to the distance from the area of the bearing surface that engages the rifling and the rifling itself. There are many products that allow you to measure these critical dimensions. Some are better than others. I won’t be going into the methods of measuring jam and jump. If you are not familiar with this aspect of reloading it is critically important that you understand this concept before you attempt this test.

Many reloaders feel (and I tend to agree) that meaningful COAL adjustments are .002 to .005. Every once in a while I might adjust the COAL by .010 but this seems like I am moving the bullet the length of a football field. The only way a shooter will be able to benefit from this situation is to let go of this opinion that more than .010 change is too much (me included).

Trying to find the COAL that puts you in the sweet spot by moving .002 to .010 will take so long the barrel may be worn out by the time you sort it out if you don’t give up first. Since the sweet spot is .030 to .040 wide we recommend that you conduct the following test to find your rifles VLD sweet spot.

Load 24 rounds at the following COAL if you are a target competition shooter who does not worry about jamming a bullet:
1. .010 into (touching) the lands (jam) 6 rounds
2. .040 off the lands (jump) 6 rounds
3. .080 off the lands (jump) 6 rounds
4. .120 off the lands (jump) 6 rounds

Load 24 rounds at the following COAL if you are a hunter (pulling a bullet out of the case with your rifling while in the field can be a hunt ending event which must be avoided) or a competition shooter who worries about pulling a bullet during a match:
1. .010 off the lands (jump) 6 rounds
2. .050 off the lands (jump) 6 rounds
3. .090 off the lands (jump) 6 rounds
4. .130 off the lands (jump) 6 rounds

Shoot 2 (separate) 3 shot groups in fair conditions to see how they group. The remarkable reality of this test is that one of these 4 COALs will outperform the other three by a considerable margin. Once you know which one of these 4 COAL shoots best then you can tweak the COAL +/- .002 or .005. Taking the time to set this test up will pay off when you find that your rifle is capable of shooting the VLD bullets very well (even at 100 yards).

Regards,
Eric Stecker
Master Bulletsmith
My experience is to reference Cartridge Ogive length, NOT COAL, magazine length has been my worst enemy! Once you have found the most accurate powder charge, You are looking for patterns that group horizontal, not vertical at this stage. I then suggest 15 thousandths off the lands and incrementally lengthen Ogive length out to just engaging the lands. Somewhere in this range you will find the best!
 

Unclenick

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Somewhere in this range you will find the best!

The starting premise of Stecker's paper is that this is not so, particularly not for long, secant-ogive VLD bullets. The late Dan Hackett, a benchrest competitor, wrote of an example in the 1995 Precision Shooting Reloading Guide. He had a 40X rifle in 220 Swift set up for benchrest. He had settled on seating his bullets 0.020" off the lands, which worked for his other guns, but with this rifle, he had been unable to get 5-shot groups better than 3/8" at 100 yards with the average being about 1/2". Then one day, in changing to a bullet with 0.015" lower ogival throat contact point, he accidentally turned the micrometer adjustment on his seating die the wrong way, resulting in seating the bullets 0.050" off the lands instead of 0.020" off the lands. He had 20 rounds loaded before he noticed the error. He considered pulling and reseating the bullets but decided just to use those cartridges in practice. When he did, he got two 1/4" groups and two true bugholes in the ones.

There also used to be a description online from a time when Somchem, the South African powder maker, had a service in which they developed loads for customers. They had a customer bring in an old 8mm Mauser that had belonged to his grandfather and that he wanted to hunt with again. Examination showed the throat was shot out beyond any reasonable expectation for performance, but the customer wanted to try anyway, for sentimental reasons. So they agreed to try. The procedure used by Somchem was probably the earliest example I've seen of the method used by Stecker. They got the best load they could with the bullet out in the worn throat and then started backing it deeper into the case. Every time they went deeper the group shrank. When they finally stopped way back off the throat (I don't recall a number; perhaps an eighth of an inch or so) the gun was shooting the smallest groups they'd ever had a gun shoot in the history of that load development service. Something under a third of an inch, IIRC, which is pretty good for hunting rifles.

So, seating depth has a bigger range than many suspect it can. Quite a number of folks report finding more than one sweet spot. Most of the first-located ones for conventional length tangent ogive bullets are closer to the 0.010"-0.020" range, but certainly not all, and many report finding two depths that work, one close and one far from the throat, like the old Mauser had. I don't doubt they all are tuned to the load used to find them by this method, but my unanswered question is about the absolute universality of these depths. Are they consistently the best point with that bullet for all powder burn curves and load levels, or do they shift some. I've had some examples where they appeared to shift. I just don't have enough data to present something useful about it. I'm hoping to settle it this summer.
 

Mikecr

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When someone suggests a limited seating relationship -as though a standard, they expose themselves as knowing little to nothing about seating potentials. The worst offenders I've seen in this regard (hundreds, over decades) have been competitors who have never actually done full seating testing. And it was always obvious.
 

birddog 68

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When I worked up a load for my.280 rem using 168 gr Berger bullets I used the formula as they suggested. My rifle shot horrible until I was .090 off the rifling. You can never say what one rifle likes unless you have tried it!
 

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