The importance of bullet-to-barrel alignment and fit: Part 2

by Tom Gaylord
Writing as B.B. Pelletier

Part 1

This report covers:

  • An opportunity arises
  • Cartridge comparisons
  • Disaster!
  • Ta-da!
  • At the range
  • The test
  • Final accuracy test
  • Discussion
  • Summary

Today is Part 2 of this report that may go one more time if I don’t cover everything today. I think I won’t, because today I am reporting on a big experiment that has taken me months to complete — plus a whole lot of money!

In Part 1 I talked about the importance of the alignment of the bullet to the bore of the gun. I hope you got something from that. Today I will begin discussing the importance of the bullet’s fit. And when I say bullet, I include pellet, though there are some things that are unique to pellets that will have to be discussed later.

An opportunity arises

Several months ago I was in a local pawn shop where I saw a Taurus revolver with two cylinders. One is chambered for .22 long rifle cartridges and the other is chambered for .22 Winchester Magnum Rimfire, or WMR. I thought, “What an ideal platform to test the importance of bullet fit for accuracy, since the .22 long rifle cartridge and the .22 Magnum cartridge do not share the same bore dimensions.” We discussed this in the 4-Part series The development of the .22 rimfire cartridge.

Taurus revolver
This Taurus .22 revolver has one cylinder for .22 long rifle and another for .22 Magnum.

Cartridge comparisons

The .22 long rifle cartridge contains a heeled bullet that’s sized 0.2225-inches in diameter for a bore that is nominally 0.223-inches. The “heel” is a cupped portion of the bullet that sits inside the cartridge case and expands when the cartridge is fired. The heel grabs the lands of the rifling in much the same manner as the skirt of a pellet.

The .22 WMR is a more powerful cartridge that contains a conventional bullet sized 0.224-inches for a bore of the same size. While that is just one thousandth of an inch larger (0.0254 mm) than the long rifle, it is big enough to matter. That is what this report is about.

22 Mag and 22 Long Rifle
The .22 long rifle on the left has a smaller diameter bullet than the more powerful .22 Winchester Magnum Rimfire.

With this gun I had the perfect testbed to test the theory that both cartridges can’t be equally accurate, because one of them has to compromise on the bore size. So I bought it and proceeded to take it to the range.

Disaster!

On March 30 of this year I shot both calibers in the gun at my rifle range. But there was a big problem. More than half of the cartridges failed to fire! That was true for both calibers. It’s probably why the gun was in the pawn shop in the first place.

And, here is the big deal. Whenever you experience unreliable ignition in a firearm, you cannot depend on the accuracy you’re getting. When the powder ignites halfheartedly, the pressure curve of the burning gunpowder is thrown off and the results are sporadic. It’s like a precharged air rifle that has a velocity spread of 300+ f.p.s. No one is going to trust what a gun like that does. I had to get the gun fixed before I could conduct the test.

Ta-da!

Fortunately I discovered a local gunsmith who is a real gunsmith — not just a parts-swapper for ARs and plastic pistols. This guy actually knows how to fix guns. How important is that? I will tell you. The local gun store allows this guy to pick up guns for repair and bring them back to the store, and they don’t charge anything for the service! You pay the gunsmith, only! But the gun store provides the drop-off and pickup place for him. That’s how important a real gunsmith is.

On top of that, the gunsmith’s services are reasonable. He examined some fired cases I gave him, plus some unfired ones where the primer wasn’t struck hard enough and determined it was either the firing pin or something in the ignition chain. Turned out to be just the pin and I got a working revolver back to test for you.

22 rims
The .22 Magnum cartridge on the left has been fired 4 times without success. The firing pin marks are very light. The case on the right fired the first time.

At the range

So, last Friday I had this revolver at my rifle range. But I was faced with another problem. Do pellet guns ever shoot better with one pellet than they do with another? Of course they do, and the same holds true for firearms. How would I know if I was testing the gun with the best ammo? The short answer is — I wouldn’t. You can never know what the best ammo is until you try it all, and I had two different calibers to try!

Here is what I did. I have just three different types of .22 Magnum ammo, so I tried all three in the gun. I probably have 20 different .22 long rifle cartridges, but for this test I limited myself to just three. If this business of bullet size is real, something should show up in these few trials.

three long rifle rounds
Three .22 long rifle rounds from my collection.

three Magnum rounds
The only three .22 Magnum rounds I have.

The test

I shot at 15 yards (45 feet) off a bag rest. I was seated and the butt of the revolver was rested on the sandbag. I shot five rounds of each type of ammo at a bullseye target, using a 6 o’clock hold. I used one target for .22 long rifle rounds and another for Magnum rounds. Since there were only 5 shots with each type of ammo, for a total of 15 per ammo type, it was easy to remember where each brand of ammo shot. That enabled me to select the best of the Magnum rounds and the best of the long rifle rounds. Let’s look at what I got.

22 long rifle test target
Three 5-shot groups from each of the three .22 long rifle cartridges. It was for me easy to see that the Eley Tenex rounds were the best. You can’t tell that from this target, but I could as I shot it.

22 Magnum test target
Here is the .22 Magnum test target. Again you can’t see which round was best, but I could. In this case it was the CCI TNT Green.

Let’s talk about the test targets. First, do you notice that the .22 long rifle rounds seem to be clustered a little tighter than the .22 Magnum rounds? There is no reason to measure the “groups” because each target was shot with 5 each of three different rounds, but the closeness of the holes overall suggests that .22 long rifle rounds will be more accurate than .22 Magnum rounds.

Second, I will go on record as being surprised that the .22 long rifle rounds hit very close to where the .22 Magnum rounds hit. There is a little difference, but not as much as I would have expected.

Final accuracy test

Now that we know the two most accurate rounds it’s possible to conduct an accuracy test. Five Eley Tenex .22 long rifle rounds go up against five CCI TNT Green .22 Magnum rounds.

22 long rifle group
Five Eley Tenex rounds made a 1.521-inch group at 15 yards, with 4 in 0.815-inches. I will address the one “flyer” in the report.

22 Magnum group
Five CCI TNT Green .22 Magnum rounds made this open 2.217-inch group at 15 yards. There is no semblance of grouping seen here.

Discussion

First, let’s talk about the one flyer in the .22 long rifle target. It seems obvious to me that the Eley Tenex rounds want to group tight in the Taurus revolver. So, why is that flyer there? It wasn’t a called pull, and I think you can tell from the other 4 shots that I wasn’t making aiming errors that large.

Twenty-two caliber rimfire ammo has a history of problems with priming. It isn’t as consistent as it could be. Sometimes you get a flyer just like this one. That’s why .22 rimfire was dropped from BRV competition (a benchrest competition requiring extreme accuracy) — because air rifles were beating the pants off the rimfires! Admittedly at a closer range, but that was because of the lower ballistic coefficient of the diabolo pellet.

You might also argue that this revolver has just been fixed for faulty ignition, and maybe it’s still bad. After shooting it many times on this test day I think that problem has gone away completely. I think it is now reliable. This is all just my opinion and cannot be proven without a lot more testing, but this is what my gut is telling me.

Summary

I know this is just one little test that proves nothing. But it does give us a little insight into what I am trying to show you about the bullet-to-barrel fit. If I wanted to bowl you over I could stretch the distance out to just 25 yards and the difference between the rounds would be more dramatic.

I have a lot more to say about the fit of the bullet to the bore. Today was just the start of that discussion. We had to start somewhere.

57 thoughts on “The importance of bullet-to-barrel alignment and fit: Part 2

  1. B.B.,

    Any way to measure the bore (slug it?) of the Taurus? I’m guessing it’s a little on the large side, and the heel of the .22 is expanding to fit, but the 22 WMR does not.


  2. B.B.,

    Thinking on this and the previous article the smoothtwist barrel of the FX line seems to allow gradual swaging of the pellet through the smoothbore before engaging the rifling probably is what allows the FX barrels their reported accuracy. This revolver seems to be more suted to using standard rimfire ammunition rather than .22 magnum. That would indicate that you could further tighten up the groupings and show a significant difference between the two cartridges if you are inclined to do so.

    Siraniko


    • Siraniko
      Yep with the FX smooth twist barrel.

      It sizes the pellet for you.

      I never tryed with my Monsoon’s I had with shooting different pellets. I only shot .22 caliber JSB 15.89’s and 18.13’s. both pellets were accuate.

      So maybe with the FX smooth twist barrel design they are more pellet friendly guns than others. I never tryed other brands. Maybe that would of told a story. Now I wish I would of. Just to know.


    • Siraniko,
      That bullet put in backwards in BBs previous blog. I got the idea from BB that if the base of the bullet was deformed it affected accuracy so the bullet was put in backwards. So the deeper the rifling the more deformation of the base if fired conventionally
      Fxs have micro rifling for a few inches at the front and the pellet base has already been swaged so there is little deformation on the base, perhaps?
      As with Gunfun 1 I have only used JSBs and get one hole groups at 25 yards.


      • Bobfrom Oz

        I’m thinking along those lines too. Maybe I’ll have to find a way to have a relatively tight leade to open up enough to allow the pellet in but not engage the rifling. Who knows until somebody gets it doneb if it will make a difference in accuracy?

        Siraniko


  3. Have you ever noticed when you are testing different pellets to find “the pellet” that it sometimes takes a few shots for the gun to settle into a group after switching pellets?

    Or is it just my imagination?

    Ian


    • 45Bravo
      That’s what I see happen. And sometimes it takes a good number of pellets fired before the gun starts grouping. I call that seasoning the barrel.


      • Glad it isn’t just me, it’s common to see the first shot a flier, then the next few shots migrating to a point on the target that begins to form a group.

        Then switch pellets and it does it all over again.

        Also I have another question.
        When testing shot count on a co2 gun. Does shooting a few pellets, then dryfiring for a number of shots then shooting pellets again really give you a accurate representation of shot count?

        As opposed to shooting pellets for every shot?

        I mean the pellet provides some back pressure for every shot, thereby being more efficient on gas usage.
        it would seem (to me) that there should be a cumulative difference over the course of the cartridge.

        Any experience on that side?




            • Rambler
              Don’t know. On way to find out is dry fire a complete cartridge and see how many times it shoots. Then do a cartridge shooting pellets.

              Only problem is the pellet will start shooting low or stop shooting the pellet out of the barrel but still have Co2 left.

              So a half dozen one way or the other. Who knows.


      • GF1,

        Seen that as well while looking for the golden pellet.

        When changing to a different brand (alloy) of pellets I’ll clean the barrel and season it with 10-20 shots before continuing to test. When sorting pellets for the test I keep the culls specifically for seasoning.


  4. I had a Taurus 992 in blue finish, it was much more accurate in .22 LR than in .22 mag.
    I think the bore size and twist rate may be optimized for the more popular caliber.

    I never slugged my barrel, just my observation of shooting thousands of .22 LR rounds,
    And a few hundred .22 WMR rounds.

    The extra “power” of the .22 WMR was negated by lack of accuracy and extra muzzle blast from the 4 inch barrel in that caliber in the particular pistol I owned.

    Ian


    • Ian,

      This revolver is the 992 in blue. I know the photo doesn’t look blue, but that is because I photographed it on a black background to bring out the details of the gun. The camera resolved it into a light gray, but it is really dark shiny blue.

      B.B.


  5. B.B.,

    Very interesting. Looking forwards to learning more.

    I will looking forwards to see how you tie (pellet) fit/head size in. First, what is (on) the can is often not what is (in) the can. There is variances as shown with a pellet gauge. Second, pellet weight can vary slightly within the same tin. That is just one brand, of one pellet type.

    Then, there can be 2 or more brands that may have the same head size. Verified of course. Then, even if the head size is verified among the pellet types/brands,… there will be weight and profile differences.

    Will a 14 grain pellet with an X head size shoot as well a different 18 grain pellet with the same X head size?

    We know that PCP’s can handle heavier pellets better than a springer. Where does weight and power factor in? The springer might do well with a lighter pellet shot at a lower fps and the PCP does it’s best with a heavier pellet shot at higher fps,.. or even the same fps. 2 power plants, 2 weights, 2 fps,.. (same) head size/fit.

    Generally, the heavier pellet and higher fps will equate to better downrange performance due to more retained fpe and stability in flight.

    Many, many factors as we all know,.. that in end all affect the ultimate goal,… accuracy at target. So,.. at first glance, it seems that you opened up a can of worms. It will be interesting to see how you structure the testing that involves so many variables and have it clearly illustrated into targets AND have that traceable back to projectile and barrel pairings.

    How much data collection is enough? How much is too much? 😉

    As always,.. a Good Day to you and to all,… Chris


    • Chris
      “Generally, the heavier pellet and higher fps will equate to better downrange performance due to more retained fpe and stability in flight.”

      True. But also remember that if there is more mass diameter from a bigger caliber that it will slow down quicker than a smaller diameter caliber.

      More drag trying to cut through the air if the pellet diameter is bigger. So in most cases a bigger diameter pellet will slow down sooner than a smaller diameter pellet.

      And that makes a world of difference depending on what distance the gun is accurate in and how you use it.


  6. BB,

    Back when I was in my mid teens my dad bought me a .22 WMR. My ammo choice back then was very limited. After missing quite a few groundhogs over the summer and listening to my dad say it was me, we took the rifle to the range and tried it out on the bench rest. Both my dad and I were getting +6 inch groups at 100 yards. We got rid of it.



      • BB,

        What did not occur to us at the time was it could have been the ammo, even though we reloaded our centerfires for accuracy. At that time the only .22 WMR that was available to us was Winchester and sometimes Remington. Now there are several manufacturers. Perhaps now a decent rifle and ammo combination can be found as with .22 LR.


      • BB,

        P.S.
        Two or three shots would be in a 1 inch group and then there would be a flyer. That should have clued us in to the ammo, but did not. Of course, like I said we did not have much of a choice where that was concerned.



          • BB
            I had a couple boxes of 50 out of a 500 round brick one time lately that had about 5 or so shots that would be like that.

            They were those low velocity CCI 710 fps 40 grain long rifles. I could hear a different sound when the shots went off compared to what they normally sounded like. I knew right off the bat before the shot hit the paper that it would be off from the rest of the group.

            Haven’t had anymore like that though.

            My question is what causes that. Did the pimer powder not get distributed evenly around the rim. Or maybe the powder load was different on those rounds?


            • GF1,

              As I understand it, the priming compound goes into the new case as a drop of slurry. The case is then spun to fling the slurry into the rim where it dries. I guess there can be bubbles or voids in the process when millions are made on every shift.

              B.B.


              • BB
                Ok that makes sense. Wasn’t sure how the primer got loaded.

                Then I guess a change in the amount of powder charge in the case could vary. Then that adds in another possibility that the bullet gets shot at a different velocity.

                It’s surprising to me that some .22 rimfire ammo is as accurate as it is. I got some CCI 1070 fps 40 grain long rifles that are very accurate in my Winchester semi-auto and my bolt action Savage.

                The standard velocity Remington and Federal and Winchester long rifles can’t top the CCI 1070 fps rounds even.

                But to get back on track with the report today. Maybe the fit of the bullet to the barrel is helping the 1070 fps rounds beat out the others as well as a more consistent primer and powder load.. They do say they are a target round.


              • BB
                Also since we are talking about fit to the barrel.

                I have some 1570 fps Aguilla long rifle rounds I shoot also. And no not a miss type on velocity. 1570 fps.

                And what I noticed is sometimes with my Savage bolt action the cases won’t eject. I have to pull the clip out then recocked the bolt to extract the case. Now I’m n my Winchester semi-auto they cycle fine. So power to eject the case from the semi-auto might over power the fit expansion of the case.

                And here is the thing. Those cases are swollen by about a .001″ or more compared to standard velocity cases and even the low velocity CCI ‘s. And they are almost as accurate as the CCI 1070 fps target rounds.

                So maybe case fit plays a role also in rimfire guns. I would of thought that the higher velocity rounds wouldn’t be as accurate as they were.

                And I know for sure pellet fit to barrel is definitely a big thing for air guns. I do know from recovering pellets from my steel spinners. That the pellets fired from a given air gun that have deeper witness marks from the rifling in the head and skirt of the pellet is my more accurate shooting air guns.


  7. I also had a 9 inch barrel revolver with a long rifle and magnum cylinder. It was significantly more accurate shooting .22 long rifle. I finnaly wore it out.

    Don


    • Don
      Seen you posted the other day that your dragon fly multi-pump wasn’t as accurate as you like.

      I was going to reply and some how let it slip by.

      And I’m not bringing this up right now to put the gun down in accuracy. But what I’m wondering especially in relation to today’s blog is about fit.

      Do you think you just maybe haven’t found the right pellet for it yet?


  8. A friend of mine is into serious target shooting with the .22 rimfire an we were discussing the merits of the expensive target ammunition. Out of curiosity, I did some testing and found that the .22 rimfire has quite a spread in velocity.

    Just checked my notes…
    (Same rifle (Browning T-Bolt) used for all strings)

    Remington Subsonic, 3 strings: ES 71.4; 127.6; 102.0

    Remington Thunderbolt, 2 strings: ES 61.8; 84.1

    Federal, 1 string: ES 62.2

    CIL Imperial, 1 string: ES 51.0

    …with results like this it’s not surprising that a good AR can shoot the pants off of a rimfire within its effective range.


    • Hank
      Wow that big of spread. I’ll tell you the truth. I can’t remember ever chronying my .22 rimfire guns for spread. I have for velocity to see iff me and Buldawgs chrony read .22 rimfire the same. The CCI 710’s to be exact is what we tryed. Now it makes me try to remember if we checked the velocity spread.



  9. B.B.
    Have you considered testing this in your AR? I have heard that .223 rounds are less accurate in a rifle chambered for 5.56. I have no personal experience with this as I have not shot an AR in many years.
    Gerald


    • Gerald
      That’s a difference of close to .004″ with the 5.56 round being smaller.

      There’s probably even a difference in case size too I bet without having both in front of me.

      But that was a interesting thought. Maybe it might work the other way around. A 5.56 in a .223 barrel. ???

      I’m surprised a .223 would load in a 5.56. Not sure. But would be something interesting to find out if it can be done.


      • I very well could have said it backward. What I know in my very limited AR knowledge is that one of the chambering’s will load either size. The smaller over all length of the other size will cause it to be less accurate because the bullet has to travel a short distance in the chamber before it reaches the rifling. At least that is the theory.
        Gerald


    • Gerald,

      I sort of did test it when I worked up a load for the rifle. I had been told that a certain 77-grain spitzer bullet was the most accurate, but I discovered that a different 69-grain spitzer was superior. I have tried scads of 53 and 55-grain bullets to no avail. Even military 5.56 mm bullets which are identical to Remington .223 bullets, since the .223 was derived from the 5.56 mm round.

      It isn’t the fit of the bullet to the bore in this case — it’s the twist. My 1:8 barrel needs a heavier bullet to stabilize. It was length and weight I was adjusting, not the fit of the bullet.

      B.B.


      • BB
        So if you had a better fitting bullet diameter wise. You may of ended up with good results?

        And then there we go. Spin rate.

        As it’s been until recently. Spin rate was what we was stuck with.

        So what makes a for a better result. Fit of the projectile or velocity of the projectile?

        Or so do both need to be in a given range of fit and velocity to achieve accuracy at a given distance?


  10. I do a lot of target shooting and reloading as my primary hobby. When I go to the range, I notice that the first round or two are off target but as the barrel warms up and gets seasoned (I like that term!), the rifle becomes settled in and more accurate. So my question is this: when you are hunting with a cold (unseasoned) firearm or airgun, are you forever cursed with that first shot or two being off target? A philosophical question or a technical question? Is there even a correct answer?

    Just wondering.
    Bob in Texas


    • B-I-L
      I got to answer. Yes that curse is there on some guns.

      It’s when you shoot a gun enough every day is when you learn what guns do or don’t have that problem.



    • B-I-L,

      As an answer to the Cold Shot issue ink of the sniper who normally gets but one shot with no possibility of “seasonings” in the Lodge CAST iron pan. I have always quietly laughed at the hnters sight in ranges when shooters blast away with plentiful drifts of brass around their shooting position and then call themselves sighted in for the entire season. The next shot is from a COLD barrel and all too often a miss! So what good is sighting in? It takes at least a minimum of three shots which = a no longer cold barrel to adjust the scope!
      And what do we call that? Certainly not a rifle sighted in for a COLD shot; great for target shooting since most folks have posts today that the shoot multiple shots to SEASON the barrel. At least in a powder burner after he Cold Barrel round the bore beomes tighter as it continues to heat causing the next round to have a higher velocity (up to a point) so your internal balistics have a profound effect n your exernal balistics. U.S. Navy SEAL that go through sniper school get to do cold bore shots every morning and most find it the hardest shot possible. I’m not certain about cold bore and airguns because my experience with Springer is limited to 10M. With PCP it is mostly with Big Bore and if I have sighted in with my 1st shot results from multiple targets then my first shot is invariably to POA (Point Of Aim.) B.B. helped me get much improved accuracy with my DAQ BIG BORES with his advice about shooting mutiple targets to get a handle on POI (Point Of Impact) for each Number shot as a result of pressure tube flex. For the first shot at a given range I use POA then hold over/under for other distances from a Dope Card and on to 2nd, 3rd and Nth shot Dope. I haven’t found any Cold Bore issues once the rifle, and more probably hammer/valve are broken in. I think B.B. has the real issue in his cross hairs with his needing time to settle in comments. I find the process that I dutifully train all the time speeds me to get set for the first Shot. I think when B.B. did those one shot a day testing he learned more than most shooters about himself ( even than he has admitted to!)

      Patience and process are truly virtues a shooter needs to enhance to the utmost to ever be more than just a good shot. That will be a great way to ward off the Cold Bore Curse…or whatever it is!

      shootski


      • Shootski
        Plain and simple like I have said many times.

        Shoot your gun and get to know it. Then you can make that one shot one kill.

        I have hunted and pested for most of my life. The shots that I do decide to take I want them to hit. So you have to know how that gun shoots if you pick it up 2 days later and haven’t made a shot with it in that time period.

        Practice with the gun your going to use. Plain and simple learn how it shoots. Then the next step is for the shooter to learn how to shoot it.


  11. I’ve seen a Ruger Blackhawk in 9mm/.357 mag and both gave good groups. Not sure how, but it did none the less. I don’t own one, but I’d like one.

    Doc


    • Doc,

      I owned one of those convertible Blackhawks and yes, both cylinders were accurate. I think it’s the only time I have seen a convertible gun do that. I’m guessing Ruger went tight on the .357 barrel and just accomodated the smaller 9mm round.

      B.B.


      • B.B.

        Ever shoot a Ruger in .30 carbine ? My brother had one and I shot it with some of his hot half jacket loads .
        Not much recoil at all, but that noise !!!! Beyond painful .

        tt


        • Twotalon,
          Yes! My brother had several. They were fun and accurate. As with noise, I always wear ear protection with any centerfire and with pistols in rimfire so I the noise didn’t bother me so much.

          Doc


      • B.B.,
        what I haven’t seen first hand is a BlackHawk in 45lc/ 45acp or a 10mm/ 40 S&W. I wonder if those also were accurate as the 9mm/357 set up.

        Doc


        • Doc,

          I have seen the .45 Colt and ACP. As I recall, the Colt is more accurate than the ACP, though thye difference is small. There you are talking about 2 or three thousandths difference.

          Don’t know about the .40/10mm. Didn’t even know there was one.

          B.B.


Leave a Reply