Blaserman Posted January 24, 2014 Report Share Posted January 24, 2014 Hi all, me again, I always run my cartridges through a Hornady Concentricity tool to achieve zero to half a thou runout, it takes me all afternoon to craft fifty rounds, I'm not complaining, I really enjoy it, but I'm sure a lot of you gents may not do this and achieve superb groups. My question is, does a bullet stabilise in flight, at what kind of distance if it does, and is the "bullet truing" worth it? As an aside, I don't actually seem to get any fliers, but that may be because I'm lucky. By the way Scotch Egg, liking my previous posts and posting nice smileys will not futher your request for a Tikka Unimount... Link to comment Share on other sites More sharing options...
Jagged 77 Posted January 25, 2014 Report Share Posted January 25, 2014 Hi Blazerman, stability is determined by the length and weight of the projectile, the twist of the barrel it's being fired though and also the velocity. There are calculations on JBM which you can use to determine if a bullet is going to be stable. I'm not sure if you're referring to this or the myth of the bullet 'going to sleep' in flight. Lots of debates on this but as far as I'm concerned if a bullet is stable in flight after 300 yards it has to start off stable to begin with, therefore bullets going to sleep is a myth. I don't point any of my bullets but I've heard of others doing it to good affect - either or buy the new Lapua L bullets which are more uniform supposedly around the hollow point area. Link to comment Share on other sites More sharing options...
DaveT Posted January 25, 2014 Report Share Posted January 25, 2014 I don't see that bullet truing can do anything but good provided you don't have to 'graunch' it too far to correct any iffy concentricity produced by your dies. If I was unhappy about concentricity straight from my dies though I would address possibly causes there first off. A bullet will have a certain minor wobble (precession) as it leaves the barrel induced by instabilities in the bullet itself, the rifling twist, wind effects as it leaves the muzzle etc.....and it will stabilise just like a spinning top does if the twist is enough for the bullet length/weight....how far away from the muzzle that happens I have no specific idea.......probably depends on the bullet weight, design & speed etc......consult Brian Litz book. Link to comment Share on other sites More sharing options...
srvet Posted February 2, 2014 Report Share Posted February 2, 2014 Does the act of trueing a wonky bullet alter neck tension? Has anyone compared the accuracy of those that have been straightened with those that were concentric in the first place? Link to comment Share on other sites More sharing options...
brown dog Posted February 2, 2014 Report Share Posted February 2, 2014 Lots of debates on this but as far as I'm concerned if a bullet is stable in flight after 300 yards it has to start off stable to begin with, therefore bullets going to sleep is a myth. Ever seen a child's spinning top (or a spinning top out of a Christmas cracker) get spun up and then bounce on to the ground/table wobbling wildly and then become less wobbly? Link to comment Share on other sites More sharing options...
Hatzi Posted February 2, 2014 Report Share Posted February 2, 2014 Im looking forward to seeing the debate on this one! Link to comment Share on other sites More sharing options...
Blaserman Posted February 2, 2014 Author Report Share Posted February 2, 2014 Hi all, so if my bullet has 3-4 thou of runout, will it stabilise in flight, or will it have a certain degree of yaw? Cheers Link to comment Share on other sites More sharing options...
Scotch_egg Posted February 2, 2014 Report Share Posted February 2, 2014 By the way Scotch Egg, liking my previous posts and posting nice smileys will not futher your request for a Tikka Unimount... It can't be said I didn't try lol Best get the order in for an AXMC. Regarding the topic of conversation I am of the opinion that bullets stabilise in flight. But every little helps. The forster co-ax press certainly helps. Link to comment Share on other sites More sharing options...
shuggie Posted February 2, 2014 Report Share Posted February 2, 2014 I don't see that bullet truing can do anything but good provided you don't have to 'graunch' it too far to correct any iffy concentricity produced by your dies. If I was unhappy about concentricity straight from my dies though I would address possibly causes there first off. A bullet will have a certain minor wobble (precession) as it leaves the barrel induced by instabilities in the bullet itself, the rifling twist, wind effects as it leaves the muzzle etc.....and it will stabilise just like a spinning top does if the twist is enough for the bullet length/weight....how far away from the muzzle that happens I have no specific idea.......probably depends on the bullet weight, design & speed etc......consult Brian Litz book. Hi Dave same view as you the less run out the better,years ago i was told if a bullet that was fired off the lands that had a run out of say 2or more run out when it entered the lands it stayed out then occuring a bullet to exit the barrel not being concentric ,i dont know if this is true or not all i can say if its not true then run out would never be a problem as the bullet would true its self as it entered the lands Link to comment Share on other sites More sharing options...
DaveT Posted February 2, 2014 Report Share Posted February 2, 2014 I think that trying to get the bullet to enter the lands as straight as possible is really about getting it to engrave into the rifling equally all around so as to get minimal in-barrel bullet deformation and therefore the greatest possible degree of stability as it leaves the barrel (all other things like an appropriate rifling twist being equal) ....therefore minimal yaw / dynamic instability induced by any weight imbalances along its spin axis in flight. Litz book goes into detail on this ...V.Good read. Link to comment Share on other sites More sharing options...
DaveT Posted February 2, 2014 Report Share Posted February 2, 2014 Hi all, so if my bullet has 3-4 thou of runout, will it stabilise in flight, or will it have a certain degree of yaw? Cheers The bullet will always have a certain amount of yaw as it exits the muzzle.......spin drift is one example / result of yaw induced by he rifling .......the wind will also induce yaw which can result in vertical deflection as well as the horizontal effect. Significant runout will effect the bullets stability if it engraves into the rifling off-centre and is 'deformed' by some degree.....I have no idea of the magnitude of the effect.......just know its not a plus point! Link to comment Share on other sites More sharing options...
brown dog Posted February 2, 2014 Report Share Posted February 2, 2014 The bullet will always have a certain amount of yaw as it exits the muzzle.......spin drift is one example / result of yaw induced by he rifling . Not really, drift is induced by the fact that the bullet is slightly nose-up to the trajectory (because the trajectory drops) and the resultant upward air pressure on the bullet's nose causes it to point slightly high-right to the trajectory. The up/down effect of wind is usually ascribed to magnus (ie lift) rather than yaw. Link to comment Share on other sites More sharing options...
DaveT Posted February 2, 2014 Report Share Posted February 2, 2014 Thanks for the clarification BD........I confess to being a bit free with the term 'yaw'......just trying to say that there are a number of forces that put a bullet off of the expected track besides an off-centre entry into the lands Link to comment Share on other sites More sharing options...
nowler Posted February 3, 2014 Report Share Posted February 3, 2014 you ideally need the bullet to engage the rifling straight and true to the bore. i'd argue that if it engages with yaw, it will exit with yaw as once the first part is engaged, the rifling will hold it in that position and it won't straighten out. others may argue differently? how squint it can be when it engages will depend a lot on both your ammo and your chamber freebore dimensions. i'd always shoot for ammo with as close to zero runout as possible, and cases that have been sized to suit the chamber so that they are not sloppy. custom made dies are the obvious choice to help with this, redding comp dies being a next best option.... try shooting some groups with zero runout and a lot of runout and comparing the 2. you might be surprised by the results. happy shooting derek Link to comment Share on other sites More sharing options...
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