Weird things with .22LR match ammo

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grauhanen

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I don't doubt that what I'm going to describe happens to just about every .22LR shooter. There may be some very good lots of .22LR match ammo, the ones that do what's expected (with a very good rifle, of course), but I've yet to shoot one.

Usually a round ought to go close to where its muzzle velocity predicts. Faster rounds have a higher POI than slower ones. That's what makes sense.

Yesterday I shot at 100 and it was quite calm -- at least until I began shooting a second 100 rounds at a second set of targets. I chronographed the rounds but was unable to get the first ten because the chrony sensors needed attention. I used two boxes of Midas + for the first ten groups.

What struck me was the MV/POI mismatch that occurred in every group. For example, the round with the lowest POI on the top right bull top right bull had an MV of 1047 fps, right in the middle of the ES range. The same kind of thing happened with every group.


 
It seems obvious that some rounds don't strike the target according to what their MV predicts.

To be sure, many rounds do have POI that match their MV, but some rounds strike high for the MV, some rounds strike low.

Below is another target that shows this impossible to anticipate behaviour. In the top right bull, for example, one of the group's fastest rounds had the lowest POI. With the bottom left bull two rounds have side-by-side POIs yet one is 25 fps faster. In the bottom right bull the same kind of thing is seen.

 
I guess this is why they would want would to shoot 'lasers' instead of real ammo at Olympic competitions... I would prefer real rimfire ammo that's actually good though.
 
These are the reasons I would love an electronic target but definitely not in my budget.

I have a few thoughts but am by no means an expert in any way shape or form.

1. What chronograph are you using ? What is the room for error ? (I know each type has a few things that can mess with it)

2. With the different velocity I wonder if it changes the barrel harmonics and the projectile leaves the barrel and a different point in its vibration ? Thus a slight shift in POI ?

Those are the two thoughts I have for now.

Either way this is very interesting info and I really want to repeat this process myself and see what my results are but that wont be for a while. Very interested to see what others say :)

B
 
you're acting as if every soft, bare-lead nose of every round is the same as well. Just because it gets launched at 1047fps doesn't mean it will slow down at the same rate as the next projectile. The iMV is more about mass weight then aerodynamics. It won't effect the bullet much after 18" of acceleration, but it sure will on the 3600" it has to travel to the target.
 
Here's one more example. This group, shot with Center X, has a very wide extreme spread of 1030 - 1069 fps. It might be expected that the fastest or slowest round could be an issue.

As it turned out, both the fastest and the slowest rounds were somewhere in the middle. The lone high flyer was 1040 fps.



I recently got a video camera so I'm trying to learn how to use it. As a result the groups were recorded on video. (Editing videos is more challenging than shooting them or the targets.)

 
Jahnj0584 said:
you're acting as if every soft, bare-lead nose of every round is the same as well. Just because it gets launched at 1047fps doesn't mean it will slow down at the same rate as the next projectile. The iMV is more about mass weight then aerodynamics. It won't effect the bullet much after 18" of acceleration, but it sure will on the 3600" it has to travel to the target.
Click to expand...

You should be aware that the behaviour of rounds that are "perfect" is predictable by means of ballistics calculators. The rates at which they slow down, drop, drift etc. are calculable. If these things were unpredictable, no one could shoot much of anything with accuracy.

Of course shooting outdoors is never completely predictable. Yesterday, while shooting the targets shown, the conditions were as calm as I've seen them.
 
grauhanen said:
You should be aware that the behaviour of rounds that are "perfect" is predictable by means of ballistics calculators. The rates at which they slow down, drop, drift etc. are calculable. If these things were unpredictable, no one could shoot much of anything with accuracy.

Of course shooting outdoors is never completely predictable. Yesterday, while shooting the targets shown, the conditions were as calm as I've seen them.
Click to expand...

Sure, but you just ignored my point. Not every round is going to be made to a perfect parabolic nose, and you're going to believe there is ZERO deformation or variance between rounds? How easy is it to mushroom the tip just by loading the mag slightly-wrong?
 
Jahnj0584 said:
How easy is it to mushroom the tip just by loading the mag slightly-wrong?
Click to expand...

RE potential for bullet deformation:

With my single shot Anschutz 54 action, I have learned to be cautious in working the bolt to make sure the bullet entry into the chamber is smooth, and the bullet nose does not slam into the chamber edge and scrape its way into the chamber. That said, I still see fliers, although I have not done the chrono tests on these like Grauhanen has to examine POI issues.

I know that with my magazine-fed CZ's, the angle of the cartridge feed can sometimes get tilted and the bullet nose slams into the barrel, or edge of the chamber, requiring a manual poking of the round to re-align and enter the chamber properly, but after it has been dented by the process.

This issue with magazine mis-feeds in my CZ'z is common with CCI ammo. My CZ's do not like CCI. My CZ's feed much better (with very few mis-feeds) with European ammo (Lapua, SK, Eley. I have not yet tried RWS, so cannot comment on RWS feed-ability in my CZ's). I do have the single-shot adapter for my CZ's, which feed usually flawlessly with the Euro ammo, but I still need to be careful with the bolt.

Long story short, yes there is the potential for denting the bullet when feeding into a chamber. That said, I am sure Grauhanen is well aware of this, and guessing he is single feeding the rounds with alot of care in working the bolt to avoid bullet denting.
 
bdb.hunting said:
2. With the different velocity I wonder if it changes the barrel harmonics and the projectile leaves the barrel and a different point in its vibration ? Thus a slight shift in POI ?
:)

B
Click to expand...

I'd spin this a little differently. With a different velocity there will be a different exit time which finds the barrel in a different point in its vibration.
 
Jahnj0584 said:
you're acting as if every soft, bare-lead nose of every round is the same as well. Just because it gets launched at 1047fps doesn't mean it will slow down at the same rate as the next projectile.
Click to expand...

I think you have identified a very significant factor ... variations in BC. Shorty recently posted a bit of data that is worth reviewing. And Eric C just interviewed Chase Stroud who has studied this a bit. He quoted some numbers for BC SD that he felt had a very significant but widely disregarded effect on results on target.
 
RE chronograph accuracy:

I suspect (although I have no evidence), that chronographs in the consumer grade (of whatever design) are not as accurate as they claim to be.

I would like to see a chronograph show-down event of several models measuring the same series of shots all at once from the same rifle, and a statistical analysis of the variance among and between them. Perhaps this has been done - please point me to a source of info if it has.

For example a show-down of chronograph devices: optical, Labradar, Magnetospeed, and the new Garmin.

I would expect that the absolute MV value per shot would differ between the devices. Its not the absolute value that is important. The important thing would be the consistency of the variance among and between.

For example, if a shot registered on one chrono as higher MV than the one before, and the other chrono registered the same shot as lower MV than the one before, you know you have a problem.

Another example would be if the MV of the next shot registered as 10 fps different from the last one on unit A, and the other chrono unit B registered as 20 fps different than the last one.

One statistical test that might work is a histogram plot comparison. Histograms plot the proportion of MV's in bins that can be standardized, e.g. ten 10% bins of MV across the ES. In theory these histograms between chronographs should be nearly identical if the chronographs are recording the same relatively even detection of MV's across the ES, regardless of the absolute value of the MV's for individual devices.
 
Jahnj0584 said:
you're acting as if every soft, bare-lead nose of every round is the same as well. Just because it gets launched at 1047fps doesn't mean it will slow down at the same rate as the next projectile. The iMV is more about mass weight then aerodynamics. It won't effect the bullet much after 18" of acceleration, but it sure will on the 3600" it has to travel to the target.
Click to expand...

Jahnj0584 said:
Sure, but you just ignored my point. Not every round is going to be made to a perfect parabolic nose, and you're going to believe there is ZERO deformation or variance between rounds? How easy is it to mushroom the tip just by loading the mag slightly-wrong?
Click to expand...

The point I was making is that ballistics calculators can show the performance of the ideal bullet, the one that is perfect in shape, symmetry, and balance. Of course .22LR bullets are often imperfect. That's one of the key reasons why these bullets don't go where MV predicts.

I remain uncertain about what is meant by "iMV". The MV data I have shown is ostensibly the muzzle velocity of the bullets very soon after they've left the muzzle. I don't pretend to know what the MV is at any point beyond the point where the chronograph takes its reading.

I don't pretend that there's no change to the bullet as it passes from the leade through the bore to the muzzle. I also don't pretend that I know how my barrel, or any other one for that matter, uniquely obturates the bullet itself. That's not possible for anyone. If you are aware of how this can be done, please let readers know. Additionally, if you can elaborate why the MV/POI matches or mismatches shown here are invalid, that, too should be shared.

In any case, no two rounds are likely to be exactly alike and will behave dissimilarly to some degree. It's worth considering that this contributes more to what's seen in the examples shown above than to what you may be alluding. The bullets are different for each shot taken; the barrel remained the same.

Williwaw said:
I think you have identified a very significant factor ... variations in BC. Shorty recently posted a bit of data that is worth reviewing. And Eric C just interviewed Chase Stroud who has studied this a bit. He quoted some numbers for BC SD that he felt had a very significant but widely disregarded effect on results on target.
Click to expand...

It's not clear that this is what Jahn is getting at, but BC is indeed a variable with .22LR. It's not necessarily the same from one round to the next. The problem is that without the right equipment, it's not easy to calculate.

In any case, the BC variation that may be expected with .22LR match ammo will not significantly affect results at distances up to 100 yards. To quote someone with whose work on .22LR ballistics you may be familiar, "It really won't make a hill of beans difference what BC you use for distances less than 100 yds, but if you're playing some game where first hits may be required at long distance (100 to 200+) it may be helpful." (Landy on RFC post #18 https://www.rimfirecentral.com/threads/bryan-litzs-ballistic-performance-of-rifle-bullets.601764/#nested_reply_top_post)

Do you have information that BC variation between the bullets -- as small as they may be -- would significantly affect their POI at 100 yards?
 
bdb.hunting said:
2. With the different velocity I wonder if it changes the barrel harmonics and the projectile leaves the barrel and a different point in its vibration ? Thus a slight shift in POI ?
Click to expand...

Williwaw said:
I'd spin this a little differently. With a different velocity there will be a different exit time which finds the barrel in a different point in its vibration.
Click to expand...

I'd spin it differently too, but not this way because the idea itself isn't sound.

The suggestion of bdb.hunting and Williwaw is that the "weird" or unpredicted POI occurs because different MVs result in different exit times at different points in muzzle vibration. If this was correct, then all rounds with the same MV should have similar POI (disregarding wind, of course). In short, same MV = same barrel vibration = same exit time (or exit angle).

The basic tenet of shooting for consistent results is consistent behaviour in all things involved, rifle, ammo, and shooter (wind taken out of the equation for simplicity). This means consistent behaviour in barrel vibration. At the simplest level, barrel vibration should be expected to be the same for each round with the same MV. In other words, if there are two rounds at 1050 fps, the barrel can be expected to "vibrate" the same way for each with the same or similar results on target.

This is exactly what is not occurring. Rounds with different MV's sometimes have an expected POI but sometimes they don't. If barrel vibration explained this, then the explanation is valid only some of the time. An explanation that works only some of the time is itself not valid. Barrel vibration doesn't change arbitrarily. If it did, all bets must be off and consistent results never expected.

What is occurring is that at times there's a MV/POI mismatch. At it's worst, slower rounds may strike higher than faster ones and faster rounds strike lower than slower ones. The barrel doesn't change its vibration pattern at random. There must be something that varies from round-to-round.
 
I've often characterized shooting a .22 at 100 yds as like throwing rocks.
I do any serious testing at 50 yds or meters, and 100 is somewhat unpredictable.
 
grauhanen, Were your shots at 100 done with 'cooling time' between shots ? I noted in the first set of groups a couple with 'same mv' hitting at opposing heights, with 10 or 20 rounds (depending on your target sequence) between them. Short time gaps causing a warmer barrel effect due to diff viscosity or moistness of lube or thermal expansion of the barrel ? jaia has at one time suggested that 'moisture effect' as a possible variable . I don't recall if he had substantiated that or just posited it.
 
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