.22 LR Accuracy

[steve b.]

ajj..,

at this time, i'd be guessing as to the why, but there are some conflicting results on paper in terms of velocity consistency.

I have been setting up the chrony at the target, about 2' infront of the paper at 50 yards. When shooting groups, i track every speed and point of impact. What strikes me so odd is that quite a few times, the bullets will strike the target at a fps variation of 10 to 15 fps, yet go in the same hole. now keep in mind that what i consider a tiny group from this rifle is a single hole. not a clover leaf or something the size of a fingernail, i'm talking about a tiny bughole for 10 shots.

what's so weird is that ammunition with a deviation of 10 to 15 fps will drop them all right in the hole, lets say with an average of 995 fps at the target, but then at times, a round at 997 or 994 fps will strike 1/2" low or high, in a verticle line.

it's not wind or conditions, i have enough wind flags out there and probes to have a macy's day parade, and the last time i did this there was just enough breeze to keep the mirage from buggering up the scope.

the conditions were 45 degrees, sunny. 1-2mph breeze that was consisent at full value from left to right.

the rifle is as solid and consistent as it gets, and the ammunition was Eley Tenex, about 3 different lots, and the new Lapua Master.

the question is relating the velocity to the point of impact. these odd shots are not frequent, but they tend to pop up in the middle of a target and never a sighter.

considering this and rolling out the drop to 100 meters, it's a miss on the ram.

hmmm...

[ajj]

That is most interesting and the explanation could be really important informatiion!
Do you use a second chrony at the muzzle?
Perhaps most interesting, at least to me, is that a rimfire railgun is substantially more accurate than a good target rifle. I would have assumed that the ammunition was the limiting factor.
Exciting stuff.

[steve b.]

I guess what would be thing thing to figure out is what exactly makes killer so good? Wha measurable characteristics, other than groups / targets, can we look for and measure.

I'm gonna setup two chronys next time. One at the muzzle, one on the target and see if the numbers jive. We all assume they do, but what if they don't..?

I was thinking that the one with the lowest velocity deviation, but what is lowest, and what deviation is acceptable / possible / actually makes a difference?

The search continues.........

[shakes]

I wanted to say hello and thanks for all the info to Steve B. I've been reading what he has to say and its almost like we have our own Calfee for the silhouette world at the moment. I like others cant wait to read all the results from Steve's testing.

[steve b.]

aah... : "we have our own Calfee "

easy with this..! calfee and i don't play well together, and I got less time on the planet than he does behind a rifle. i got some catching up to do.

i do appreciate the support and promise to never type: "folks"



I got a neat test in the works, i'll post some info when i get a chance.

thanks again..!

s.

[chickenchoker]

Steve, one other consideration when you test ammo next time. I pulled bullets on rounds a couple of times (some times a round gets dropped in the dirt and folks don't want to put it down that nice custom barrel). There seemed to be some extra space in the case not occupied by powder. When we shot reduced loads in our pistols, with relatively fast burning powder, we got increased velocity variations because of powder position in the case. This problem was solved by always having the ammo oriented the same way prior to firing, such as, ammo placed bullet down in the ammo box and when rounds were loaded one at a time in the gun with the muzzle pointed at the ground, breech closed and brought up to target and fired. If you shot a revolver then between shots you would point the muzzle at the sky and then bring the gun down to the target and fire. Which ever method you used you just tried to be consistent in how you oriented the powder in the case.I know that the velocities are not that extreme but it has to do with how the powder is ignited and how fast or slow that pressure is applied to the base of the bullet. The powder that is used in lapua/sk/wolf is vihta vuori N105 which is very fast rifle powder. Most of the push on the bullet is used up in about 17-18" of barrel and the bullet is starting to slow before it leaves the muzzle. That's why the velocities are so close and still you have a "flier" out of your bughole group. It's just something else to look at next time your at the range.

[steve b.]

CC,

I have observed the same issue, most cases are about 1/3 full, and the rounds like CCI Velocitor are about 1/2 full.

But, keep in mind the fundamental difference between CF and RF. In CF, the primer sends it hot jet of flame though the primer hole into the case, causing an ignition of the powder. Where as the rimfire primer material detonates like an explosive charge, slamming the powder into the back of the bullet with the force of the explosion prior (we are talking an extremely short time frame) to the combustion process of the powder.

To test this, pull a bullet, dump the powder and fire off the case in a short barreled pistol, and you will see the force of the explosion. That force easily carries the 1 grain or so of powder to the bace of the bullet before it begins to combust (this, as we know, is why bullet velocities vary with barrel length).

There has been alot of talk about firing pin location in rimfire actions, but there is no existing testing that shows a preference, ( alot of self-appoined experts feel the have the answer, but cannot provide double blind test results to proove anything) and further, all the testing assumes that the force of the primer explosion causes no disturbance to the powder (which I feel is obviously incorrect).

another thing that is not being researched by the ammunition manufacturers is different (reduced) amount of priming material in the case. many manufacturers have not changed the volume of priming material in their case for over 20 years. Eley is working some with this, but pretty much no one outside the factory know the actualy details. They keep an extremely close grip on those trade secrets. outside of a handfull of people in the USA who know, the rest is pure speculation. I do feel the amount of priming material in the case is over kill, but it does result in reliable ignition.

But, good to be looking at this from every possible direction.

Also, if it does make a difference, I can't wait to see BR shooters chambering their rifles and hoisting the barrel up, all while trying not to set off a 2oz trigger.

Now for this part: "That's why the velocities are so close and still you have a "flier" out of your bughole group" If this were true, then you would not have bullets go in the same hole with a wide variation in velocity. It's not becuase of chance, it happens too much. I'm open to any ideas on this one.... I'm lost.

I'm unsure if it is a pressure / velocity issue yet, but I have not pinned down anything to prove a point either way.

As for this: "Which ever method you used you just tried to be consistent in how you oriented the powder in the case." I agree, but the ammunition goes from the box, to the feed ramp in the action. The rifle never moves more than 1" (recoil) in the 1-piece rest, and I barely move. There is no possible way that I know of to make that part of the equation more consistent. Ideas...??

[chickenchoker]

Steve, I'm curious if you have tried powder position in the case as a variable in your testing or you don't think it merits consideration? The only way to know for sure is to hook up a pressure test device to the gun and know for sure. I don't know that you need to point the barrel of the bench rifle at the sky ,but you can take the unfired round and lightly tap the base or bullet against your book or any other appropriate object. If I had a rail gun I'd give it a try cause it's pretty easy to do.

[steve b.]

no, i have not tried it.

all the cases go from the nose-down position in the box into the rifle's loading ramp.

i can easily give them a tap with the nose pointed up to see what happens, that's simple enough. would you say 50 rounds of "tapped" ammunition versus 50 rounds out of the box a good initial look?


I don't have any of this equipment: "The only way to know for sure is to hook up a pressure test device to the gun and know for sure. "

could we go a step further and make copy of this? what about a clear plastic tube, filled 1/2 way with powder collected from rimfire cases, sealed on both ends. we could move it around and see where the powder goes in the tube when it is removed from the box and loaded versus tapped.

[steve b.]

I've been discussing this with a few of the engineers i work with, and there are a hand full of issues to nail down. i'll work on it and get backto everyone.

s.

[steve b.]

Ok, here is what I have come up with for the pre-positioning of the rf case in the rifle ( pointing it up in the air to settle the powder to the rear of the case)

1. the powder is going to fall back to the bottom of the case after it is loaded into the rifle, creating a slope of powder from the back of the case to the front. there is a equation used for soils that react this way, but since the powder is in a case, there is the friction of the powder running on the sides of the case, and the force of the powder pressing back into the center of the case. in short, the powder does not flow as far forward to the bullet as if it were poured out on a plate.

2. during the firing process, the firing pin travels forward, striking the case with enough force to crush the rim and send the powder forward. this in inself has enough force to thrust all the powder to the front of the case. this thrust of force is also felt to the powder prior to the priming materials ignition.

3. when the primer material ignites, it in itself has enough force to dislodge the bullet from the case, without the aid of gun powder. this explosive force carries the powder forward (actually adds to the powder's already advanced position due to the firning pin's force).

4. this results in the powder's location to be against the heel of the bullet, prior to the combustion of the gunpowder.

5. this leads me to think that tapping the powder to the rear of the case will have no measureable influence.

Thoughts..?

[lone ringer]

Steve, I had a good friend that worked as ballistics expert for Sierra bullets back in the70's and 80's and during some of our conversations he shared some of his experiences with problems that he encountered. One of them had to do with fliers he would get when trying loads for the back then new 6X47 caliber. He said three or four rounds would go into a ragged hole but never failed for a flier to spoil the nice groups. He determined that the powder quantities used to propel the bullets in that particular cartridge were not leaving enough lubrication on the barrel and periodically he would get fliers. He then started dipping the bullets in Hoppes number 9 just before shooting and the fliers went away. He told me of having done that with .22 rimfire ammunition and noticing that it helped their accuracy. I have to warn people here that may want to do the same that some lubricants if left on the ammo long enough will foul the powder.

I wanted to suggest on your experimentation to pay attention to the lubricant on the bullets and maybe remove or add some as you see fit and notice the difference it makes in your groups.

I know that some types of BR competition like ARA do not allow shooters to mess with the ammo, remove or add lubrication but I believe that is something we silhouette shooters in some cases can find that beneficial to do. A lot of us in CA and AZ bought a whole bunch of Federal 900 Match for about $3.50 a box and eventually figured out that we needed to add lubrication to the bullets if we did not want that Federal ammo to lead our barrels.

I have tried adding different kinds of lubrication to ammunition through out the years with mixed results. I one time bought several boxes of Tenex ammo at a very reasonable price but found the ammo's lubrication to be all dried out and not shooting well at all but as soon as I added lubrication to the bullets it shot extremely well. One of our favorite formulas for adding lubrication to bullets consisted in mixing Lee's Alox about 50-50 with mineral spirits and then dipping the lead and removing the excess by shacking the boxes onto some paper towels.

I have also used Pam cooking oil sprayed sparingly into a one quart plastic bag and then placed the contents of one or two boxes of ammo into the bag, shook the bag and after that put the ammo back on to their boxes.

Never found adding lubrication to adversely affect accuracy with the exception of one time when I added Slick 50 to some boxes of ammo that I did not use right away and the oil fouled the powder of some of the rounds. Now I do not use anything that can get inside the cartridge and foul the powder.

[BlauBear]

How much variation in velocity does the manufacturer expect between rounds, and what is the accuracy of your chronometer? Can you induce velocity differences by manipulating lubrication, fouling or loading technique? You're chasing a variation of what, <1%?

[steve b.]

The lubrication of the ammunition is a hot topic at the moment, and word is that Eley has changed their lubricant. The amount of lube in a barrel is anyone's guess, I do know that the current test rifle is needs at lease 20 rounds when going from a clean barrel to settle down, and it's looking like after 150 rounds, it begins to drop off.

As you stated, messing with lube is a no-no in BR, but by all means if it is legal in Sil, go for it. As to how anyone checks this in BR is beyond me, and I have never seen it checked.

I did try wiping some lube off the bullet last weekend, and this made no noticeable difference - but the barrel is a 1-16". The lube removal was popular with the Benchmark 1-17" reverse taper barrels and slow Eley ammunition is cold weather.

Accuracy in chronographs - that's a tough one. We will have a few out there next time, and will have to see if they show different numbers.

"How much variation in velocity does the manufacturer expect between rounds"

This info is not released to the public generally, and rumor mill is saying that this last batch of Eley came in much faster than what's printed on the box. I have not seen that yet, but I have not messed with any out of this shipment. I'm also not convinced this is the final point of accuracy. It seems absurd to think that less consistent ammunition in the velocity dept. could be more accurate than a more consistent ammunition, but really think there is more to it than just velocity. But, all things being equal, it should be that accuracy and consistency in anything go hand in hand. Only further testing will show the answer.

"Can you induce velocity differences by manipulating lubrication, fouling or loading technique"

I didn't see the change in velocity by messing with the lube, but like I said it needs more testing. I've got the fouling thing pretty much wired on this rifle, and I'm not sure what you mean by loading. I place the loaded round on the feed ramp, gently close the bolt by pushing the rear of the bolt body, then cam over the bolt handle. Same way every time.

As for the percent, i honestly don't know. until they all go in the same hole, or until I shoot some perfect cards, I'm still lookin for answers.

[lone ringer]

Steve, another thing that we silhouette shooters have to contend with is having to shoot for record without the benefit of firing fouling shots once the match begins. Since we shoot in relays and some times we have to wait up to an hour for our relay to come up a lot of the rifles we use send the first round to a different POI with respect to the ones that follow if they have not been fired for awhile (read cold barrel). Have you run into that problem while shooting silhouette and do you have any thoughts regarding the problem?