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Thread: Tumbler?

  1. #1
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    Question Bullets Tumbling in flight??

    Got started patterning 200gr. Partitions for my 8x57JS today. Gonna need to adjust the scope before I go any further.

    Here's what's weird, though.

    I got some tight little groups, and some outrageous flyers.

    I'm wondering if my barrel is too short to reliably stabilize the bullet? That strikes me as unlikely, especially since it's an heirloom rifle and I don't know the twist rate.

    Here are the details:
    8x57 JS
    19 inch barrel
    New RP brass
    Fed 210 primers
    IMR 4350
    200 grain Nosler Partitions
    100 yards.

    One of these shows two of the three bullets in a group.
    The other either shows all three bullets through the same jagged hole, or a tumbling bullet.

    So two questions:
    1) Does anybody know the twist rate on a pre-WWII mauser with the serial number in Arabic?

    2) Can anyone read the first photo for what might be going on?
    Attached Thumbnails Attached Thumbnails SSCN4190.jpg   SSCN4189.jpg  

  2. #2
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    Shoot some more let me see a five shot group fired slowly. Shoot them in the center of the target. I don't know if the one pic is of two shots and torn paper between or one boni fide keyhole. How many did you shoot and did you find enough holes?

    It's not likely that two went in one hole and one was a keyholer, but I guess it could happen. Were all of the bullets .323" diameter?

    I think the twist was changed when Mauser went to the .323" spitzer bullets (8X57S) and I think that twist rate is 1 in 10". It would take a pretty bad barrel not to stabilize a bullet at 100 yards, or a grossly under sized bullet.

    You didn't give the powder charge but velocity could be so low as to not stabilize the bullet. What velocity are you expecting? The max load with the 200 grain partition with IMR4350 is 52.0 grains and would be about 2700 fps with a 24" barrel. I think the load would have to be compressed to get 52 grains in the case. I have shot that bullet with 50 grains at 2612 fps from a 22" barreled rifle. Why 19"? Somebody had a hack saw they weren't using?

    Your Arabic rifle may be Iranian or Egyptian. I think Ludwig Olsen explans all of that in his book. Good luck with the tumbler.
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    Quote Originally Posted by Murphy View Post
    How many did you shoot and did you find enough holes?
    5-shot groups. Holding on the center of the target put my groups at the bottom of the paper. I didn't adjust the scope because the first group (48 grains) printed a little higher than the subsequent groups. Not sure why that would be...

    Quote Originally Posted by Murphy View Post
    Were all of the bullets .323" diameter?
    Well, they all came out of the same box of Nosler Partitions. I didn't take the caliper to each bullet before loading it, but there were no weird wrinkles, creases or extra shoulders on the case necks, which I would think might happen if a .318 or .308 round somehow made it into Nosler's box.

    Quote Originally Posted by Murphy View Post
    I think the twist was changed when Mauser went to the .323" spitzer bullets (8X57S) and I think that twist rate is 1 in 10". It would take a pretty bad barrel not to stabilize a bullet at 100 yards...
    Yeah, the Greenhill formula gives a slower twist than that - roughly 12" - as acceptable. On the other hand, I've read where this one guy recommends a constant of 100 (rather than Greenhill's 150) to properly stabilize a hunting bullet. With these Nosler .323s, that constant would call for an 8 1/2" twist. Still, as I understood it, that guy was talking about terminal performance, not printing on paper. Could it be that the barrel is too darn short to stabilize it? How many revolutions of the bullet does one need to really get it spinning?

    Quote Originally Posted by Murphy View Post
    You didn't give the powder charge but velocity could be so low as to not stabilize the bullet.
    I wondered about that. But the first load was 48.0 grains, and had only one flier. The second was 49.0, and had two. The third load was 50.0, and got that weird keyhole/tumbler.

    I'll try this all again the next time I get to the range - and I'll let the barrel cool between each and every shot, instead of cooling and cleaning just between groups.

    Quote Originally Posted by Murphy View Post
    Why 19"? Somebody had a hack saw they weren't using?
    As I said, it's an heirloom rifle. The distant cousin who brought it back from some war or other 'sporterized' it short. Very short. It might be 19.5", but you get the idea. It's got a full-length Mannlicher stock, a target trigger, and a Weaver K-4. He could nail a house together with it shooting 175 grain spitzers over IMR 3031. (I know, I know, it's a faster powder.)

    Anyway, it shoots Norma's 196 grain round nose bullets very nicely - originally their SP Alaska bullet, and now the Oryx. I'm hoping to at least match those groups from Norma factory fodder. Ideally I'll beat them at longer ranges. Beating the box - every handloader's dream, right?

  4. #4

    Cool Bullets

    While it doesn't sound possible try loading a bullet the same weight which is a solid lead core, instead of the H type core of the Partition. The partition makes this flat base bullet longer than a regular style flat base bullet. Also try some ammo loaded with 180 grain bullets. If that is a key-hole the bullet length may make a difference. While you are at the range you can shoot a couple of groups and see if this problem recurs. This rifle may have a non-standard twist, even tho it is only 19 or so inches it should stabilize a projectile. You could even go so far as to check the twist with a cleaning rod and see if it is standard or a ******* twist.
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    Default keyhole

    Thats a keyholer for sure.


    I would try a 10 shot target....or at least 2 more 5 shot groups.


    If no more tumble then it was a fluke sub-caliber bullet in the box.


    Maybe a .311 or .313 or .308.


    just my $0.02


    jedi.

  6. #6

    Default Maybe not

    If the bullet in question had been sub-caliber (smaller than .323) the next smaller bullet manufactured by this bullet company would not have stayed in the neck. Providing you were using the proper set of dies. Nosler's next smaller bullet would be a .311 and wouldn't stay in the neck. So don't dwell on that fact too long. Check the rifleing twist and be sure your bullets are the proper length. In a barrell which is in good shape, twist would lend itself to this problem.
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    Default twist or land dia?

    Twist is the same for every round......so wouldnt they all tumble?

    Bullets are the only variable that day.
    ( If it were 2 different days with extreme temp differences then air density could change things)(colder air needs more twist)

    So I wouldnt dwell on twist too long either.

    Only other thing would be if it was the rifling was worn or if it was larger than standard land diameter. Like some1 over did it fire lapping.

    Then maybe it gets way out of spec as it heats and throws later shots in the string.

    jedi

  8. #8

    Default Bullets

    If this rifle shoots 175 grn spitzers and 196 grn RN very well as you say. The only variable is bullet length. 175 grn spitzers and 196 grn RN bullets are both shorter than the 200 grn partitions you are now working with. Longer bullets take a faster twist. While all bullets that come from this rifle may not keyhole at 100 yds. they may have begun to yaw, and at another 30-60 yds may be keyholing as well. This rifle may not have a military barrel, it may well be a civilian firearm; a lot of civilian firearms were pressed into service by local militias during the war.
    " Americans will never need the 2nd Amendment, until the government tries to take it away."

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    Why don'tcha just check the twist, with your cleaning rod, jag, and patch etc.? It's easy. I checked the twist on a rifle just the other night.

    Probably, it's easily enough, to stabilize the heaviest bullet that would be used. 1-10 should be plenty, and your rifle could have a faster twist than that, especially if it's a Military rifle. Maybe, 1-9 .

    The bullet length is the biggest factor in determining needed twist. Velocity is a smaller factor, but not your barrel length.
    Smitty of the North

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    Quote Originally Posted by brav01 View Post
    This rifle may not have a military barrel, it may well be a civilian firearm; a lot of civilian firearms were pressed into service by local militias during the war.
    I'm pretty sure it's a military barrel. It steps down in (outside) diameter twice between the action and the muzzle - I understand that's pretty typical of military Mausers of the day.

    Quote Originally Posted by Smitty of the North View Post
    Why don'tcha just check the twist, with your cleaning rod, jag, and patch etc.? It's easy. I checked the twist on a rifle just the other night.

    Probably, it's easily enough, to stabilize the heaviest bullet that would be used. 1-10 should be plenty, and your rifle could have a faster twist than that, especially if it's a Military rifle. Maybe, 1-9 .
    Smitty, what's your method? If I were to try it on my own, I'd probably tighten up the cleaning jag, then run it through while holding the rod tightly. Then I'd count how many revolutions it takes to re-tighten the jag. Anybody got a better method?

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    Default twist

    Place a tight patch on a jag and snug it in the bore. Push it in a ways and back out to just into rifling a little to insure good grip on patch.

    Place masking tape on the shaft and get it where you can mark the top dead center as close to the back of the rod as you can.

    Mark the rod at a specific point that you see with a reference.(even with back of reciever, tang screw,etc..)I use the back of a chamber guide but everyone dosent have one.(use tape or marker or both)

    Push the rod in carefully and wait till the top dead center mark comes back to top dead center and stop.

    Now mark the reference point again at the exact same place as before.

    Now remove rod and measure distance between both marks.That is your twist. 1 in (whatever the measure in inches is)

    jedi

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    8x57 Mauser:
    Specifically, this is how I did it the other night.

    I put the jag on the rod, and the patch on the jag, and pushed it into the barrel, from the breech end, all the way down pretty close to coming out the end of the barrel.

    I folded a piece of masking tape on the rod right at where it came out of the action so it was sticking straight up.

    I slowly pulled the rod back out until the tape did one complete turn and marked it again in the same way at the same place coming out of the action.

    Then I measured the distance between the same edges of the two tapes. It was exactly 10 inches.

    (I wanted to know because some older rifles of this kind have 1-12" twist, and the newer ones have 1-10" twist.)

    If you can give me the length of your bullet, and the approx. velocity, I'll run it through my LFD program, and tell you what the required twist is. I'd almost betcha that it's less than the standard 1-9 or 1-10" for the 8x57.
    Smitty of the North

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    Post More Data...

    Thanks for the help so far.

    Here's a little more info:

    The bullets read .3225 on my caliper. That's a little worrisome, since the TSX I load for my '06 read exactly at .308. That suggests I don't have a caliper calibration issue...

    Smitty's method for checking the rifling got me 3 measurements. Since the patch can't turn faster than the rifling, I figure the longer measurements were the patch slipping over the rifling a little bit. Thus, I'll take the shortest distance. That gives me a twist rate of 1 in 11".

    As I posted above, the Greenhill formula for these bullets (1.248 inches long) suggests that's acceptable.

    I'm gonna try to make it to the range tomorrow and shoot some more groups. Slowly.

    Oh, and the barrel (measured from the bolt face) turns out to be almost exactly 18". Gotta get a chronograph to see if I'm throwing these things fast enough to matter...

    Stay tuned, sports fans.

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    Yup:
    If your velocity was just 2240 fps, the "Load from a Disk" program calculates needed twist as 1 turn in 13 inches.

    As for the different measurements, make sure the patch is tight enough.

    Oh well. You're on the right track.
    Later
    Smitty of the North

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    Default erosion

    Quote Originally Posted by jedi rifleman View Post
    Twist is the same for every round......so wouldnt they all tumble?

    Bullets are the only variable that day.
    ( If it were 2 different days with extreme temp differences then air density could change things)(colder air needs more twist)

    So I wouldnt dwell on twist too long either.

    Only other thing would be if it was the rifling was worn or if it was larger than standard land diameter. Like some1 over did it fire lapping.

    Then maybe it gets way out of spec as it heats and throws later shots in the string.

    jedi
    like I said before, it could be disparity between lands and bore diameter.

    If your bore was chromed then a borescope can determine if this is letting go. (chrome is the best but it gives out eventually too)(usually seen as sparkles in the blast)

    Have a smith use a muzzle erosion gage and a throat erosion gage.

    Muzzle erosion can be taken care of by cutting off some more barrel length.

    (maybe thats why it was cut before and its eroded again)


    jedi.

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    Talking The Sunday Update!

    Got out this morning in the wind and sun to shoot.

    Letting the barrel cool between every shot made a big difference.

    No tumbling bullets. No unexpectedly wild flyers.

    There are three pics attached. Group 1 (49 grains of IMR 4350) was only 4 shots (I blew the first one adjusting the scope). Group 2 (50 grains) was 5 shots.

    I didn't upload the third group - it was larger, but didn't have the two distinct groupings of the others. I saw this the other day, but it was secondary to the weird flyer thing. Hard to say whether 51 grains started to open up the groups overall, or my shooting went downhill with time. Guess I'll just have to load and shoot another 5. Somebody twist my arm, ok? ;-) I'll probably do that the same day I get out and try 52 grains. (I've seen no signs of high pressure yet, but will watch carefully, of course.)

    The outstanding question now has to do with the 'double group' phenomenon in Group 2. That's probably a function of very cold fingers not adequately detecting whether the barrel was fully cooled.

    In any event, the groups are generally as good as I shoot with Norma's 196 grain factory fodder. I'll continue to fine tune this load. Next up: figuring out if the velocity is good enough to do anything but punch holes in paper. I may start a thread over on the shooting forum for that.

    Thanks a lot for all the insights, folks. Better form for load testing the old 8mm, an exact barrel length, and a good twist measurement, all from one thread. I'd call this one a success!
    Attached Thumbnails Attached Thumbnails First_Group.jpg   Second_Group.jpg  

  17. #17

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    have you checked your scope/mounts? have you tried some lighter bullets yet?

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    Thumbs up Real Progress!

    That scope hasn't budged in decades. And as I posted above, this rifle does great with lighter bullets.

    I got out today, and it did great with the 200 gr. Partitions. To be precise, see the attachment. 52.0 grains generated the smallest group to date, without signs of excess pressure - although the primer shows just a very slightly sharper edge.

    This is Nosler's max listed load, so from here I'll work on seating depth. But in all honesty, I'm not sure I can beat this group with five rounds and a 4x scope at 100 yards.

    If velocity loss from the Nosler manual is on par with the velocity loss from Norma's published data, these bullets are probably leaving the barrel just a hair under 2400fps. I've really gotta get a chronograph...
    Attached Thumbnails Attached Thumbnails SSCN4223.jpg  

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