An Explanation for Ammo-Barrel Behaviour

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grauhanen

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Shorty, after reading some of the various posts on this topic that you've made in a couple of threads this calendar year, I am going to try to summarize your ideas in one place. I hope I'm not misrepresenting what you've said. If I have, I welcome your corrections.

I will put in a couple of posts in an effort to make it more easily digested. Below is the first part.

All .22LR barrel performance is distance-specific according to lot. This is to say that every barrel will shoot best at a certain distance and this distance can varies according to lot. The distance for any ammo lot is a product of barrel contour and length.

To elaborate, every rifle/barrel and ammo combination has a natural tuned distance – a distance at which that ammo in that barrel shoots best. This is the distance the barrel and ammo combination achieve the most positive compensation. Positive compensation is distance-specific -- good for one distance.

A natural tuned distance produces convergence or positive compensation. In other words, the barrel and ammo combination achieve convergence at a certain distance. Convergence occurs when, at a certain distance, the group MOA is smaller than at any other.
 
The next part below.

Whatever the distance at which convergence occurs, it produces the best groups in terms of MOA size. The only way to know at what distance the ammo will converge – whether it’s at 50, 100, 150, 200, or something else -- is to test by shooting at a variety of distances.

The addition of a well-adjusted tuner means that the distance at which the ammo performs best can be changed. When properly adjusted the tuner induces group convergence at the distance for which it is set.

What convergence means is that groups are best (MOA-wise) at a certain distance. They are worse at all others, both further away and closer to the shooter. An ammo that converges at, say, 100 yards will shoot best at 100 and will shoot less well at all other distances.

To illustrate with an example, if a certain lot of ammo shoots best at 50 it will not also shoot best at 100. Equally, as counter intuitive as it may seem, the lot that shoots best at 100 will shoot worse at 50 in terms of MOA.
 
The third part below.

To summarize, whatever the distance at which convergence is achieved, that is the best distance for the rifle/barrel and ammo combination. Here the group MOA is smallest.

The further the target is moved the worse the results. At the same time, the closer the target is moved the worse (MOA-wise) the results. Positive compensation can occur at one distance at a time for any lot of ammo.

The addition of a well-set tuner simply alters the distance at which convergence occurs.
 
The next part below.

How does dispersion develop?

The way dispersion develops needs to be understood. Many shooters make the erroneous assumption that dispersion increases with distance, that group size only becomes larger as distance grows. This is incorrect.

Beginning from the muzzle, dispersion increases until about halfway to the ideal distance at which convergence occurs. From about the halfway point up to the ideal distance group dispersion begins decreasing again in terms of MOA.

In other words, from about halfway to the ideal distance, group size begins to decrease until that distance is reached. At the ideal distance, dispersion in terms of MOA is at a minimum.

And once a group passes that ideal distance it begins growing again and continues to do so the further away it gets from that ideal distance. It continually gets worse only beyond that point, not from starting at the muzzle.

Whatever the distance at which maximum convergence occurs is, it’s at that distance that the best groups are produced in terms of MOA size.
 
One final bit of information. I've used Shorty's own description of testing below, beginning with the words "Take whatever"

How to test for the distance at which convergence happens?

The only way to know at what distance the ammo will converge – whether it’s at 50, 100, 150, 200, or something else -- is to test by shooting at a variety of distances.

Take whatever distance you have available and divide it into five reasonably spaced distances. Got 200 yards available? Try shooting at 40 yards, 80 yards, 120 yards, 160 yards, and 200 yards. Got 100 yards available? Try shooting at 40 yards, 55 yards, 70 yards, 85 yards, and 100 yards. Got five different ammo variants you can test? Shoot five five-shot groups at each distance, or ten five-shot groups if you really want to get good results, with each ammo variant and compare. You should see one best distance for each ammo variant. And it probably will not be the same distance for each variant. If you find one that shoots best at 120 yards it should
shoot slightly worse at 80 and 160 yards, and slightly worse again at 40 and 200 yards. Whatever the best distance is, it should shoot worse with each distance step away from it, closer or further.
If you don't mind spending a lot of ammo you could progressively shoot in smaller distance increments around each last best result until you find the natural tuned distance for that gun and ammo variant. Shot best at 120 yards, and 160 yards was the next best? The natural tuned distance likely lies somewhere in between those. Shoot some at 130, 140, and 150 yards. Now maybe the two best results are at 130 and 140, so shoot 135 next. Eventually you'll find the distance with the best groups. If you move closer and closer than that best distance the groups will get worse. If you move further and further than that best distance the groups will also get worse.
 
Daniel G. Banting said:
Tomorrow, I'm hunting bears over bait.
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We going off topic here but good luck. I just got back from our bear hunt. We got 2 this weekend so we're done for the year. Not huge bears but they'll be good eating. The one I shot had a white patch on his chest which was pretty neat.

The big guy still eludes us, 5 years now and he hasn't slipped up, if he keeps this up he'll die of old age. Looks to be about 15 years old or so, could be pushing 20 but it's hard to tell in that age range just from trail cam pictures.
 
Fairly certain you shouldn't be hunting the big brown ones with .22LR but there's always room for someone to advocate otherwise. Me, I'll be continuing in search of the elusive reason premium rimfire ammo in a quality firearm is being so bullseye-resistant.
 
Williwaw said:
Speaking of bait ...
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What is it that's being baited? That Shorty confirm the summary is fair?

What do you think? You've followed Shorty and his ideas about .22LR ammo and barrel behaviour. You've clicked "like" for just about every idea he's had on the subject, including very recently about mid-barrel tuners. Do you feel the summary of Shorty's ideas is unfair?
 
As of this time, Shorty has given no indication that this summary of his explanation of .22LR ammo and barrel behaviour is inaccurate or unfair. Nor has anyone else. Of course this doesn't mean that anyone else agrees with Shorty.
 
grauhanen said:
As of this time, Shorty has given no indication that this summary of his explanation of .22LR ammo and barrel behaviour is inaccurate or unfair. Nor has anyone else. Of course this doesn't mean that anyone else agrees with Shorty.
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Maybe he isn't playing your game or taking the bait. Where only you have the answer and no matter what anyone else says is wrong, even IF it makes sense. Then turns into many multiple beat the dead horse going back to same old same old.

*edit*
Just go out and shoot and have fun. As clearly many don't care about this trivial nonsense. As rimfire ammo is random and rolling the dice. Id go. But my keys and ammo are locked up in storage that I don't have access to.
 
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