Famous 'PEEP & GLOBE' at 50 yards Savage MKII is on my bench!

[Bigslug]

Brass variability, bullet variability, alloy variability, lube variability, rifle variability, temperature variability, weather variability, rate of fire variability. . .

"John. . .the kind of control you're attempting simply is. . .it's not possible" - Dr. Ian Malcolm (Jeff Goldblum) - Jurassic Park

The things we learn from these exercises ARE highly valuable, however, I would suggest - for our own sanity - that we keep a second, cheap beater .22 next to the bench and a row of water bottles alongside the "record" target for those moments when the rotor wash from our propeller beanies starts to cloud our "visibility".

[OS OK]

Where the timid & faint of heart dare not tread...

[/CENTER]

[Harry Tobin]

Anyone?


I’m still curious why the Tenex bullet shape is better than say a round nose profile for accuracy. I understand the hollow point theory when it has a bubble of air trapped at the tip and air on air has less friction and possibly better accuracy?

[OS OK]

The only article I could find is this one from this link > http://www.geoffrey-kolbe.com/22LR-projectile.htm ...although I'm not sure I understand what they're saying?

22LR PROJECTILE

The .22 Long Rifle rimfire cartridge was (probably) developed by the J Stevens Arms and Tool Company in the United States and introduced in 1887. It is probably the most widely used small game and varmint cartridge in the world and is certainly the most popular target cartridge of all time. Annual worldwide production of the .22LR cartridge runs into the billions!



This popularity and widespread use justifies a section of this program devoted to this bullet alone. The standard diameter of 0.222" and standard weight of 40 grains are fixed and cannot be changed. However, you can vary the muzzle velocity and choose a zero range and a custom range.

In the late 1980's Robert L. McCoy performed a comprehensive set of ballistic measurements on the .22LR bullet at the Aberdeen Proving Ground (Memorandum Report BRL-MR-3877, November 1990). This program uses a third order polynomial drag function to fit McCoy's data for Eley Tenex between 960 and 1050 ft/sec. For velocities less than 960 ft/sec., drag is assumed to vary as the square of the velocity, with a drag coefficient of 0.24.

For velocities above 1050 ft/sec., McCoy did experiments at slightly higher velocities using a projectile having an Eley Tenex shape. The drag for this projectile was slightly higher than the Eley Tenex bullet due it being made of harder lead and so the sharp corner junction from the ogive to the cylindrical part of the bullet did not 'slump' to a smoother shape in the way the soft leaded bullet did. However, a straight line function having the same slope as this data is extrapolated from the Eley Tenex data at 1050 ft/sec. and is assumed to be valid up to 1100 ft/sec. or Mach 1. The various drag functions are as follows:

Drag equation





"OOP's, Posted too soon" .... just came across this (too large to reprint so I'll just add the link). THIS LOOKS TO BE THE ANSWER YOU WANT HARRY...

https://patents.google.com/patent/US4517898A/en

FROM THE ARTICLE JUST POSTED...THIS MAY SUM IT UP?

The projectile of this invention relies, for its construction, in the utilization of three factors, that is, (1) the in-bore yaw, the angle between the geometric axis of the projectile and the bore axis; (2) the first maximum yaw, the maximum misalignment between the projectile axis and the nominal trajectory; and (3) the damping characteristics, the aerodynamic and mass properties which reduce this yaw in flight. By the proper analysis of these factors it has been determined that in order to make a highly accurate projectile for small arms, the cylindrical body portion of the projectile must be as long as practical while the entire projectile length must be as short and stubby as practical. This configuration is designed with an additional factor of importance being that the center of pressure (drag) of the projectile must be as far forward of the center of gravity as possible. This is accomplished by a nose being in the shape of a truncated cone, that is having a flat front. A truncated cone is used for simplicity, however, any reasonably smooth transition between the flat nose and cylindrical body will suffice. A high drag coefficient is beneficial, especially if it acts well forward.

[Harry Tobin]

The only article I could find is this one from this link > http://www.geoffrey-kolbe.com/22LR-projectile.htm ...although I'm not sure I understand what they're saying?

22LR PROJECTILE

The .22 Long Rifle rimfire cartridge was (probably) developed by the J Stevens Arms and Tool Company in the United States and introduced in 1887. It is probably the most widely used small game and varmint cartridge in the world and is certainly the most popular target cartridge of all time. Annual worldwide production of the .22LR cartridge runs into the billions!



This popularity and widespread use justifies a section of this program devoted to this bullet alone. The standard diameter of 0.222" and standard weight of 40 grains are fixed and cannot be changed. However, you can vary the muzzle velocity and choose a zero range and a custom range.

In the late 1980's Robert L. McCoy performed a comprehensive set of ballistic measurements on the .22LR bullet at the Aberdeen Proving Ground (Memorandum Report BRL-MR-3877, November 1990). This program uses a third order polynomial drag function to fit McCoy's data for Eley Tenex between 960 and 1050 ft/sec. For velocities less than 960 ft/sec., drag is assumed to vary as the square of the velocity, with a drag coefficient of 0.24.

For velocities above 1050 ft/sec., McCoy did experiments at slightly higher velocities using a projectile having an Eley Tenex shape. The drag for this projectile was slightly higher than the Eley Tenex bullet due it being made of harder lead and so the sharp corner junction from the ogive to the cylindrical part of the bullet did not 'slump' to a smoother shape in the way the soft leaded bullet did. However, a straight line function having the same slope as this data is extrapolated from the Eley Tenex data at 1050 ft/sec. and is assumed to be valid up to 1100 ft/sec. or Mach 1. The various drag functions are as follows:

Drag equation





"OOP's, Posted too soon" .... just came across this (too large to reprint so I'll just add the link). THIS LOOKS TO BE THE ANSWER YOU WANT HARRY...

https://patents.google.com/patent/US4517898A/en

FROM THE ARTICLE JUST POSTED...THIS MAY SUM IT UP?

The projectile of this invention relies, for its construction, in the utilization of three factors, that is, (1) the in-bore yaw, the angle between the geometric axis of the projectile and the bore axis; (2) the first maximum yaw, the maximum misalignment between the projectile axis and the nominal trajectory; and (3) the damping characteristics, the aerodynamic and mass properties which reduce this yaw in flight. By the proper analysis of these factors it has been determined that in order to make a highly accurate projectile for small arms, the cylindrical body portion of the projectile must be as long as practical while the entire projectile length must be as short and stubby as practical. This configuration is designed with an additional factor of importance being that the center of pressure (drag) of the projectile must be as far forward of the center of gravity as possible. This is accomplished by a nose being in the shape of a truncated cone, that is having a flat front. A truncated cone is used for simplicity, however, any reasonably smooth transition between the flat nose and cylindrical body will suffice. A high drag coefficient is beneficial, especially if it acts well forward.

Thanks Charlie, so what I get from this if you’re running a Tenex style at 1080 you’re close to the limits of that design?

[OS OK]

Thanks Charlie, so what I get from this if you’re running a Tenex style at 1080 you’re close to the (SPEED) limits of that design?

Yup...Mach 1 is tops but I'd rather be under that if I had my rathers.
I order the Eley Match @1055fps but it comes out of my match chamber at 1080fps avg. ...oh well, that's what I'm stuck with but it works pretty good.

@Don & tazman...The timing of that first test had me a little concerned so I ordered another 5 round magazine. I can get my brother to load for me so I can make a target change within that 30 second shooting pace timing.
Since the weather has oficially gone to bunkers out here, I think I'll search around and see if I can find an indoor 100 yard range so I can get some tuning done and have some exact zero scope settings that aren't influenced at all by the wind. This would be a good winter task to do, if I can find such an animal?

[tazman]

Back when I still had five target grade 22 rifles, I ran some tests over the chronograph with Eley ammunition and a couple of other brands of "match" ammo. The velocities were different in each rifle.
That said, they weren't much different from each other in the rifles that did not have MATCH chambers. They were also very near the advertised velocity for the various lots as listed on the Eley box and web site.
The two rifles I own that have MATCH chambers always get substantially higher velocities than the other rifles. Both these rifles are CZ and have similar length barrels.
My tests indicated the match chamber fitted the case tightly and pushed the bullet into the rifling such that the lands engraved the sides of the bullet.
I suspect these two factors increase the pressure inside the chamber at firing causing the extra velocity.

If my chronograph is to be believed, The extra velocity was enough to cause the bullets to leave the barrel slightly faster than the speed of sound which tends to be a sub optimal condition for 22lr ammunition.
In any case, these two rifles nearly always shoot better groups across all brands and lots of ammunition than the other rifles did. I expect this is due to the match chamber and the possible extra quality of the bore. Occasionally, a single lot would shoot outstanding in one of the other rifles but you could not count on that happening.
The two match rifles I have are slightly more accurate with the great majority of ammunition I have tested and can be counted on to do well with top level "match" ammunition. They are simply more consistent.
In the testing I have done(at 50 yards) The fact that the ammo is running a little fast, doesn't seem to matter as far as accuracy is concerned. I think the issues would arise at longer distances. Definitely by 100 yards. I have not run tests at that distance(yet). There would be more time for instability and inconsistency to cause issues.
It will be interesting to see how much, if any, this changes with long term use and the associated wear on the chamber and barrel. I already have thousands of rounds through these rifles with no apparent change in accuracy.

Decades ago, we had a rifle range in the area that had a 100 yard indoor setup where centerfire rifles could be used. That would have been great for us during the winter. Unfortunately, it no longer exists.

Concerning calculating the differences of bullet drop at various distances with different nose shapes. Hornady has a ballistic calculator on their web site where you can plug in the different numbers for your ammunition with different ballistic coefficients for the bullets and get the drop information printed out at various distances. I used it a couple of times with both centerfire and rimfire numbers and found it to be very accurate.
Here is a link.
https://www.hornady.com/team-hornady...alculators/#!/

[OS OK]

I agree tazman...

Having the round engrave in the lands does a couple of things:
*it aligns the centerline of the bore and the centerline of the projectile perfectly and prevents yaw in the bore...
*it holds the projectile in the case just a few microseconds longer allowing the powder to ignite and get a good burn going before there's enough pressure to shove it out of the case into the rifling. I think that does much to improve the ES & SD's when your sampling larger strings of shots.



I wish some gunsmith could trim the rear of Harry's chamber and re-seat that tapered barrel so he could make an improved chamber in his rifle. That may seem like a 1/2 measure but it would at least hold the rounds on centerline to the bore.

[Harry Tobin]

.................................................. ...............TRIGGER JERK....................
Now with all this talk about accuracy, this all falls back to the jerk behind the trigger (ME AT TIMES). You need to be the machine that does the same thing EVERY SINGLE TIME! As I look through my targets I see moments of brilliance and then flat on my face, it was hard with the cold weather with heavy clothes hanging down. And the fact that ammo acted differently in the cold weather. And did find that as groups that started out well then went away, had to look at what just happened. Saw what I did wrong and corrected it and did a .153" personal best. Need to keep all that in my head for the spring, Charlie on the other hand is a machine all the time!

[Bigslug]

Having the round engrave in the lands does a couple of things:
*it aligns the centerline of the bore and the centerline of the projectile perfectly and prevents yaw in the bore...

. . .I wish some gunsmith could trim the rear of Harry's chamber and re-seat that tapered barrel so he could make an improved chamber in his rifle. That may seem like a 1/2 measure but it would at least hold the rounds on centerline to the bore.

I think if Harry's working on shims to tighten the headspace, that MIGHT at least solve part of the issue.

Rolling back around to my earlier mention of the dimple in the case head of the top end Federal ammo. . .my understanding is that it's done to prevent cartridge misalignment as the rim is crushed on one side by the firing pin. A tight throat that locks on to the bullet would also serve in this task, and dialing the headspace down to nothing would reduce the potential wiggle room.

I know there are a few .22's out there that crush the case rim in two spots for reliable ignition, but I wonder if symmetrical strikes would help accuracy.

[Bigslug]

.................................................. ...............TRIGGER JERK....................
Now with all this talk about accuracy, this all falls back to the jerk behind the trigger (ME AT TIMES). You need to be the machine that does the same thing EVERY SINGLE TIME!

We have a Ransom forensic firing fixture at work that we use for test firing evidence guns that are too scary to do by hand, and it uses a bicycle brake lever and cable to fire the trigger remotely. Given that this has become more about the science of the ammo and gun, it might be worth considering something similar to take even more of the "meat actuator" out of the equation.

[OS OK]

I think if Harry's working on shims to tighten the headspace, that MIGHT at least solve part of the issue.

Rolling back around to my earlier mention of the dimple in the case head of the top end Federal ammo. . .my understanding is that it's done to prevent cartridge misalignment as the rim is crushed on one side by the firing pin. A tight throat that locks on to the bullet would also serve in this task, and dialing the headspace down to nothing would reduce the potential wiggle room.

I know there are a few .22's out there that crush the case rim in two spots for reliable ignition, but I wonder if symmetrical strikes would help accuracy.

This is the first I ever heard of such a bolt/striker designed that way. It sure as heck makes sense.

[tazman]

Quote--"I know there are a few .22's out there that crush the case rim in two spots for reliable ignition, but I wonder if symmetrical strikes would help accuracy."
I did not know abut that. I would be interested to know who builds/built that action. Maybe even a link or some pictures.

Bigslug-- I remember seeing a clamp on trigger actuator that resembles a remote camera shutter release. It had a flexible cable with a push button that pushed a wire against the trigger face. Took the shake and the jerk out of the trigger movement.Somebody probably still makes that thing. Unfortunately, it would be illegal in the style I am trying to shoot. Trigger must be activated by a finger.

Details, details, details. Would still be a good thing to try out. I could find out if my trigger pull is as good as I like to pretend it is.

[Harry Tobin]

I think if Harry's working on shims to tighten the headspace, that MIGHT at least solve part of the issue.

Rolling back around to my earlier mention of the dimple in the case head of the top end Federal ammo. . .my understanding is that it's done to prevent cartridge misalignment as the rim is crushed on one side by the firing pin. A tight throat that locks on to the bullet would also serve in this task, and dialing the headspace down to nothing would reduce the potential wiggle room.

I know there are a few .22's out there that crush the case rim in two spots for reliable ignition, but I wonder if symmetrical strikes would help accuracy.

As far as the bolt shim goes, it works well. I do believe that does increase the pressure with a tighter headspace. As far as I know I’m the only one that has a durable shim for a MKII. It works so well, before the shim 50-60 rounds I would have failure to extract from carbon buildup. With bolt shim, I have shot 100 round early in the day and 100 later in the day without cleaning the chamber. So 200 rounds with no problem, cleaning the chamber with very little carbon buildup.
The bolt face is clean now after firing, I think with the better seal the case expanded better under pressure making a better seal. Plus holding the round tight to the breech face.

[Bigslug]

I could find out if my trigger pull is as good as I like to pretend it is.

I truthfully think that an actuator needs to be on Harry's list. My match grade .22 ammo pretty much sits on a shelf waiting for me to take out the heavy barrels and Unertls again. Mostly what I do now is offhand unsupported practice for field conditions on dog food cans and drinking water bottles to 100 yards, and for this, I'm bringing more human error to the party than you'll find in a box of Blazers or Golden Bullets - so that's usually what I shoot.

And really for Rabbit Hole Ballistics, at the level you're playing at, the meat interface is still the weakest link. Having gone to the trouble of barrel tuning and attaching temperature probes, to botch the shot release due to cheek pressure, fuzzing eyeball, or wearing too thick a T-shirt that day seems to go against the nature of the game. Probably save money - and certainly time - in the long run by eliminating the shots where it was the driver that failed. This would have the major advantage of freeing up your brain for shot setup and watching the conditions. If you've ever run a Sharps rifle (complicated) with a set trigger and an external adjustment scope you have to pull back (extra complicated), you'll have something of an appreciation for drowning in the steps of your operations and wishing to simplify.

Not sure what the best buttstock interface would be for such a method. Maybe drill a cross-hole through the stock for a pintle mount on some kind of bearing that rotates as you adjust elevation on your T&E? I don't think you'd need silicone or spring shock dampening on a .22, but we are dealing with extremes here.

[OS OK]

One big improvement for me was to remove my arm/hand contact from the pistol grip of the rifle.
I use a couple shot bags partially full of sand for my elbow support and now use a 'trigger pinch' method. Works like a charm with my 8 ounce trigger.



There's a combination of a little pressure from the thumb on the back of the trigger guard to steady the sight picture, then when I'm good with the wind and good with the POA - it's a tiny pressure on the trigger...slow-steady & bang, she's gone.
My shoulder never puts any pressure on the butt of the stock although my shoulder feels the 'presence' of the butt. The thickest clothing I will wear is my hoodie over a t-shirt, if I go thick like a jacket, I'm screwing up.

[OS OK]

I hope this thread hasn't died!
There's so much more to talk about in this Precision Shooting thread...

[Bigslug]

I hope this thread hasn't died!
There's so much more to talk about in this Precision Shooting thread...

Speaking of "Precision Shooting". . .something that I'm dredging out of my memories of the old Precision Shooting Magazine that may prove illustrative. . .

I believe it was Middleton Tompkins captaining the U.S. Palma team when the big match was held in South Africa, who hit on the idea of weighing the loaded cartridges. The deal with Palma was that the host country provided the .308 Winchester ammo, and it was loaded with 155 grain Sierra Match Kings, but the individual shooter had no more control over the rounds than that - - Until Mid started weighing them and sorting them into batches for his team members. As I recall, butt was thoroughly kicked.

This no more than a bigger version of what we get to contend with on .22LR ammo that we aren't loading ourselves, and it was what inspired me to do the same for my Department's smallbore team. I didn't have the time or ability to do any testing - I just made sure that shooter 1 got all the .038-.039" headspaced rounds that weighed 49 to 50 grains and so on. Given the time available, and the cats to herd, it was the most control I could exercise. As I was stacking the rounds, they did form a literal representation of a "bell curve" on the table, but figuring out how each batch differed in velocity and grouping in a given rifle was beyond our resources at the time.

Harry seems to have a solid handle on headspace and how it affects performance in his rifle. Given that rim thickness and cartridge weight are probably the two easiest (ummm yeah. . .easy ) things we can check, it might be a worthwhile effort to shoot groups and chrono samplings with rounds in which the rims are the same, across batches of different weights; and also groups where the weights are the same, but the rims vary.

Weight obviously can be variation in case thickness, powder charge, consistent amount of primer, bullet mass or even lube globs - or varying combinations of them all. Rim thickness probably has an effect on cartridge alignment, chamber sealing, and quite possibly lock time.

What I hope this would tell us is to what degree each method of sorting yields results. If it's know that (for example) a .040" rim gives good results in Harry's rifle, it would be interesting to see if cartridge weight variation with that rim thickness changes either group size or location.

[OS OK]

I have spent some time with that rifle Harry has back when it was new and running 'peep & globe' for sights and working the 50 yard bench. I was new to this BR game and was open to any suggestions the boys had regarding accuracy. That whole story is in a thread I started some time ago New to using a 'PEEP & GLOBE' at 50 yards... https://castboolits.gunloads.com/sho...BE-at-50-yards

Unfortunately all this work was done a year before I had an account with Killough Shooting Sports for Eley ammo, all the ammo I sorted by rim thickness and weight was done with mediocre bulk ammo....but the exercise was done just the same.









Here are a couple sample targets I used to track the results. I had piles of targets from these exercises. The problem here is that with iron sights, I couldn't shoot well enough to really tell any great difference in all the sorting & weighing work I did. I suppose now, with a quality CZ and actual target scope I might be able to get much better empirical data that might substantiate all the work involved to get the quantity of ammo required to do serious practice.





I sent Harry the jig I made for measuring rims & the jig I made for measuring overall length from base to front of drive band...now that Harry is running the MKII and has some fairly decent Eley Benchrest ammo he might want to set up an experiment to document these things...the ball is in his court now.

[tazman]

I bought a rim thickness gauge and weighed and measure he dimensions of several lots of ammo I had on hand a year or so ago. Not sure if I ever posted any of it. In any case, with less expensive ammo, weighing and sorting ade some small differences in group size. Enough to b worth it if shooting for score.
With the good match stuff(Eley Match, Eley Tenex, and similar from other brands) measuring was a waste of time. There were no differences I could measure with he equipment at my disposal. Powder scales and micrometers are not sufficiently accurate to tell.
With the lesser batches f ammo, he differences were slight enough that, if the day had a breeze, I didn't know if the out of group shot was ammo, wind, or me.
I finally just used the good stuff and gave up on measuring.