You think shoot sub-moa all day long huh

[tangolima]

When come to think about it more, there seems to be different probable causes of cold bore shift.

Thermal expansion of metal changes action bedding condition. However, it takes time to take effects, in terms of tens of seconds or minutes. Good rifles, like the one Panther shot, cold bore shift only happens for the very first shot. Unless he waited long before he fired the subsequent shots, it doesn't fit the thermal expansion scenario.

Another factor I can think of is the bore condition. When discussing carbon deposit with Unclenick in other thread, he brought up a vary valid point. Carbon deposit hardens when left cold. I concur that observation. Given enough time, say left over night, possibly carbon deposit in the bore absorb water in air, and turns itself like cement and hardens. Its thickness and roughness may also change. That would affect the 1st cold bore shot. Afterwards the surface is warmed and flattened by the passing cold bore shot bullet and the rifle shoots normal again. By the same token, such kind of cold bore shift applies to rim fired bore, where thermal effects to bedding should be less significant.

Cold bore zero versus warm bore zero. It depends on the "mission". Sniper and hunter needs to take effect within the first 2 or 3 shots from cold bore. It makes sense to zero cold bore. But for normal target shooters, warm bore zero is probably better. I choose the latter. But I would hold slightly differently for the first 5-10 shots if I absolutely have to start from cold bore cold bore. I choose not to dial but to hold with reticle subtensions.

Wait time for cold bore is unbearably long based what I read and was told. 15 min at the least, and even hours.

-TL

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[davidsog]

I made headshots at 1000 meters with a .308

I did not mean for that to sound like bragging.

Tangolima,

We always used the first shot of the day as the cold bore. You are right. It only matters if your cold bore shot has to be on and precise. Most rifles Cold Bore is "good enough" without the need for a seperate zero.

 

[stagpanther]

I was about to head out this evening with my 338 LM when I noticed the winds had dropped to light variable around 4 to 5 mph. That's pretty rare here, so I decided to grab the CZ 457 instead for some 22lr fun.

Shot 4 ten shot groups @ 155 yards. After "prepping" the barrel with some foulers, first up was tenex which I knew could group very small in these conditions, but for some reason instead they spread to about 3". Next was Lapua X-act--which also can group very small in light conditions--but it too grouped very wide like tenex did.

R-100 was next--over the years it has proven to be my "workhorse" long distance 22lr ammo of choice, generally turning in reliably tight groups all the way out to 250+ yds. It grouped pretty tight as usual, and juuuuust missed getting MOA.

Next up was Norma's new Extreme 22lr. The first time I tried it I didn't get very impressive results and pretty much dismissed it as marketing hype. Today was quite different; it too came very close to turning in a sub-MOA group--if you exclude that bottom shot it would have been well under MOA. About that bottom shot--I did not pull it which is what I normally do when I cause a flier to wing off and ruin a group. In this case I did not load the stock equally from front to back. It's kinda hard to explain--it's the difference between the rifle floating lightly in the sight picture even if the reticle is dead-on on the POA and having a solid "posi-lock" when squeezing the trigger. For my CZ sitting on a KRG Bravo chassis; a light contact will almost always result in the impact moving wide in relation to the other shots in the group. Like a flier, I knew it the moment I squeezed the trigger.

A couple of other notable things worth mentioning about the Extreme 22lr. Norma likes to wax poetic about its "rocket tail" and improved aerodynamic bullet design. Whatever the reason, it's true that the shot impacts are significantly above --by many inches--over other ammos which are close to its muzzle velocity. I'm thinking that is a good sign you'll likely get better performance at longer ranges with not as much elevation dial-up needed. I'll be doing more with this for sure; based on these results I feel assured it can shoot under MOA out to longer ranges.

 

[stagpanther]

Upon examining the Norma ammo I noticed that it is head-stamped by RWS; according to Josh in this utube video RWS actually makes the Extreme 22lr. What's interesting about his video is the apparent "declining BC" as the range gets longer; I suspect that is an anomaly of how the instrument records to the shots.

 

[davidsog]

"declining BC"

I suspect that is an anomaly of how the instrument records to the shots.

You are absolutely right.

Ballistic Coefficient is just an expression of the bullets ability to overcome drag. It is an attempt to account for the changing forces of drag over the flight of an object.

It is a very simplified expression of what is actually going in flight.

It is essentially the form drag of the bullet and equivalent to what is called the "Flat Plate Area" used in more sophisticated expressions of aerodynamic behavior.

Flat Plate Area is used to drive the coefficient of all drag not due to lift which is termed "Parasitic Drag".

Coefficients in aerodynamics are nothing more that a ratio of Dynamic Pressure to Ambient Pressure. It is the pressure of all drag not due to lift to the static pressure of the atmosphere.

In other words, atmospheric conditions, velocity changes, and normal variations in bullet manufacturing will vary the BC when you work the math backwards under actual conditions which is it appears that equipment is doing.

Instrumentation errors are definitely a factor too. At the muzzle you have those colliding shock that create some issues measuring velocity because the velocity of the flow moves back and forth from subsonic to Mach 1 or faster depending on the which type of shock is being formed. Complicating measurement is the fact the wave changes direction of propagation such that the bullet does not feel any of these shock collisions just like any body in flight does not feel the movement of that airmass. The bullet is essentially "cocooned" by normal shock. That is why we can have accurate rifles.

All that gobbledygook means it is hard to measure accurately at the muzzle.

Sierra explains all this here:

https://www.sierrabullets.com/exter...stic-coefficient-is-measured-by-firing-tests/

 

[stagpanther]

I've seen this in action from actual shooting, though I haven't recorded it on my labradar. It's really just a simple observation of how the extreme 22lr consistently impacts much higher than the other ammo that is not really all that much slower. That alone tells me something isn't right in how the BC is calculated and declining.

I've long held the theory (based on thousands of shots with both super and subsonic 22lr ammo)--and you may want to comment on this--that "at the muzzle supersonic" that goes transonic very soon after exiting the muzzle stands a much better chance of stabilizing for accuracy at longer ranges than other ammo that encounters the transonic transition further away--say a 1250 fps or faster bullet. My experience has been the kind of ammo that hovers in the "low mach" has always outperformed the stuff that stays supersonic well down range . A big part of this is the RN 4 bullet profile that most really good 22lr ammo uses, which has proven to be exceedingly resistant to velocity decay (drag) in the subsonic regime of its flight.

 

[stagpanther]

Winds dropped late this afternoon and I decided to give it another go with the CZ jaguar and was able to move a bit further out to 176 yards. I shot all the premium ammo types I have and they all did rather mediocre in 3" average (really scratching my head over that since tenex used to do so well out of my CZ), except for, once again, R100 and the new Extreme 22lr. They group almost identically IMO; except that the Extreme has a bit more velocity. I only had enough R100 for one 10 shot string and that was it--but I got lucky and squeezed them in under MOA.

Sun was shining right into my eyes at 10:30 so I had to set up an improvised sun screen.

 

[davidsog]

A big part of this is the RN 4 bullet profile that most really good 22lr ammo uses, which has proven to be exceedingly resistant to velocity decay (drag) in the subsonic regime of its flight.

I would think Lower drag would tend to have a flatter trajectory and retain energy downrange. Lower drag = more inertia = more resistance to change.

My experience has been the kind of ammo that hovers in the "low mach" has always outperformed the stuff that stays supersonic well down range .

That's an interesting observation and problem to ponder. They more accurate, I assume?

The characteristics of the air change based upon velocity between subsonic incompressible to compressible. It's counterintuitive but the bullet does not have to be traveling at supersonic speeds to form a normal shock, it just goes from being a bow wave and trailing wave to just attached to the bullet.

In history, we lost a few test pilots doing dive testing on the P38 Lightning. They never broke the sound barrier but it was formation and characteristics of normal shock that killed them. It introduced a stability and control problem that was fatal.

We start counting the effects of compressibility at sea level on a standard day at ~230mph. It would depend on the Reynolds Number which is a an expression of "Springiness" of the air exactly when that changeover occurs. No matter how fast your bullet travels, there is a subsonic airflow around it. How much depends on the form of the bullet which dictates the formation of expansion wave.

That incompressible flow at subsonic velocity could be lending more stability to the bullet in flight.

 

[stagpanther]

The low rate of subsonic velocity decay of the RN4 profile is pretty well-known and recorded--though it's a relative thing, in essence the 22lr is sort of like launching a miniature pistol bullet and the fact that it can retain excellent accuracy to the ranges that it does (subject to heavy influence by the airmass movements it transitions through) is in the ballistics world remarkable (at least to me) in that it gives an alternate view to the common perceptions that faster velocities and higher BC's are always better.

What I've observed--and this is just subjective conjecture based on shooting boatloads of 22lr, not based on "real science"--is that most of the very best 22lr ammo is true subsonic and is sub-mach all the way from muzzle-exit to impact and in general performs exceptionally well out to about 50 to 100 yards. The next category of ammo I have observed does better in the 100+ yards regime has in my experience been ammo that leaves the muzzle (obviously this is subject to things like length of barrel, twist etc) at "just barely mach" around 1150 +/- fps. An interesting aspect to this is that it seems the velocity will go transonic almost immediately after leaving the muzzle and yet achieves better accuracy at longer ranges than the always subsonic, at least from what I've observed.

I've never shot any 22lr ammo in my experience that retains supersonic speeds and then transitions transonic significantly down range (say 1,250 fps and over) prove to have predictably better accuracy/consistency than the best ammo made in the 1,150 fps +/- velocity range; which is why I came up with my "transonic at the muzzle" theory. I even went on a "load your own" bender by purchasing a fast-twist match barrel and hand-loaded my own 22lr ammo using much higher BC solid bullets and charges that could propel them up to 1,500 fps. Needless to say, I blew up a lot of 22lr case heads in the process. Repeatable accuracy was fleeting at best--but a lot of that I attribute to the incredibly small tolerances that affect 22lr ammo from charge weights to cartridge to chamber spacing dimensions. I gave up on that jihad when I reached the conclusion that it was virtually impossible for a common home reloader like me to achieve the kind of labratory-grade precision that the best 22lr ammo makers have. This I believe is a major difference between rimfire and centerfire. In all the hand loading of 22lr ammo that I did I found that the vast majority of charge weights were only in a range of about 2.5 to 4.5 grains; and finding the accuracy node often came down to major differences in charges varying in tenths to hundredths of a grain weight.

 

[stagpanther]

failed again--but gracefully : )

I decided to revisit quarterbores--but this time I used a recent 257 wby mag build to drive the berger 135 target hybrids @ 155yds. I think it does a better job than the 25 creedmoor since it appears the berger bullet likes extra velocity. The one low shot was once again a lapse in loading the rifle properly on my part and the result was the same as the last time I did that.

I've heard it said that weatherby cartridges are inherently less accurate than most other most-popular rifle cartridges--I don't know about that. It is true that they are generally meant to be among most powerful in class--and as such they tend to be throat roasters and would not make for good target shooting choices. Still, I think there is something to be said for Roy's theory of case design.

My conclusion after these fun 10 shot challenges is that really the main limiting factor is the shooter and not the gear; probably not all that hard to figure out if the shooter just practices enough to get familiar with the weapon in question. Not all day and night proficient, but not mythical unicorn hard, either.

 

[tangolima]

You almost did it, if not for the flyer. Better yet, all shots are on target. I highly doubt I can get close with what I have.

I have been practicing. The best I could do so far is no better than 1.5moa at 150yd all 10 shots on target. That's slight bigger than 2”.

I may have better chance with PCP airgun at 50 yd. I think I have shot 1/2” groups (one nickel size hole) with 10 shot. It doesn't have cold/warm bore shift, but it sucks with the slightest breeze.

Good shooting!

-TL

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[stagpanther]

You almost did it, if not for the flyer. Better yet, all shots are on target. I highly doubt I can get close with what I have.

I have been practicing. The best I could do so far is no better than 1.5moa at 150yd all 10 shots on target. That's slight bigger than 2”.

I may have better chance with PCP airgun at 50 yd. I think I have shot 1/2” groups (one nickel size hole) with 10 shot. It doesn't have cold/warm bore shift, but it sucks with the slightest breeze.

Good shooting!

-TL

Thanks--but with the right optic, the right barrel, the right trigger and the right ammo; that takes out all the variables that contribute to erratic shots out of the results other than the shooter IMO. That doesn't necessarily mean ultra-expensive gear; just a set-up that has a predictable and repeatable performance when the shooter does their part. After a while of shooting a particular set-up, I can almost tell what went wrong with a shot as it breaks and before it even impacts the target. If you can't reload your own ammo then you are at a big disadvantage, although I'm sure there are plenty of factory loads that can shoot very well.

Lest you think I'm actually a really skilled shooter--because I'm not, I just shoot a lot--I just got back from shooting a 6.8 spc AR which is amazingly accurate and wasted an entire magazine trying to bore-site a scope and only managed 2 hits on the entire target box--and have no idea where the rest of the shots went. Even though I thought for sure I properly compensated the shots; I got "lost in chasing the shots lalaland."

 

[tangolima]

Pull back your target or shoot at a berm for the initial coarse adjustment. You got to be on paper.

Calling shot accurately is still something I am learning to do. A few things I have picked up. I need to tune out the excitement associated with the gun going off, so that I can focus on every minute detail. It is no shame to abort a shot. It takes more courage not to fire.

-TL

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[stagpanther]

I need to tune out the excitement associated with the gun going off, so that I can focus on every minute detail.

I don't claim to be an expert--and what I say could be totally wrong--but I try ignore EVERYTHING and focus only on the reticle being steadily locked on the POA--it's almost a zen-like thing.

 

[tangolima]

I don't claim to be an expert--and what I say could be totally wrong--but I try ignore EVERYTHING and focus only on the reticle being steadily locked on the POA--it's almost a zen-like thing.

On top of that I try to feel any wind change, mostly on the firing line. Also keep both eye open helps. Scan the level bubble too.

-TL

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[FrankenMauser]

I filmed a video for the 1MADL challenge today.
Only had 50 yards available.

Best performance was from the 6.5-284.
1.45 MoA.
Nice group. But mirage from the suppressor had me drop three shots low, two of them way too low.

10 rounds.

 

[tangolima]

Ah, those 2 outliers! It would be much better without them. Good shooting!

Here is a video on cold bore shift. Good that I share almost the same thought with Mark. It is not about temperature. It is the condition of the bore being different after extended time of resting. The first shot of the day "shocks" everything back in place.

https://youtu.be/0FSvu9eG-fU?si=lsqH8uToctY2bLEc

-TL

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[stagpanther]

I filmed a video for the 1MADL challenge today.
Only had 50 yards available.

Best performance was from the 6.5-284.
1.45 MoA.
Nice group. But mirage from the suppressor had me drop three shots low, two of them way too low.

10 rounds.

Your group is a perfect example of why I almost never shoot at 100 yards or less if I can help it with the exception of sighting-in a scope. And I think it's why the MADL guys "suckered" everyone by explicitly suggesting 50 and 100 yards. I know it's a controversial thing which I can't prove; but I believe there are several muzzle exit disturbance phenomenons that happen to certain high SD bullets that are "self-stabilized" as the bullet gains distance such that the rate of dispersion is not purely linear or worse. So your group might have possibly scored MOA or better had you shot at 150 or more yards. Litz suggests trying to align multiple paper targets in a line to verify this; I've tried this but it's actually quite hard to do depending upon the arc trajectory path, elevation range of scope and terrain. At very close range you're up against the mathematics wall of the diameter of your bullet vs the size of MOA, too. I've shot 1 hole groups with large caliber bullets that were way bigger than MOA.

Oh--and to make matters worse; I've found that sometimes the opposite can also happen; a cartridge that groups spectacularly at close range can go to heck as the range extends.

 

[FrankenMauser]

Indeed.
I really wanted to shoot at 300-350 yards, especially given the incredible rarity of nearly zero wind. ("Only" 3-5 mph, and consistent; rather than the usual 15-30, constantly shifting and swirling.)

But, that wasn't available to me. And, only steel targets would be usable at that distance, on that part of the range; while steel is forbidden in the 1MADL rules ("conditions").
So, it wasn't in the cards.

 

[stagpanther]

I live on an island in the North Atlantic--10 mph and under is "calm" here. I know what you mean by "washing machine" winds.