JohnnyDog Posted March 5, 2019 Share Posted March 5, 2019 I work for an ammunition manufacturer, so I can't get into specifics.We recently purchased a batch of 180 gr 40 cal JHP projectiles from a new supplier. We assembled the ammo and sent it out to our customer, who is a law enforcement agency. The ammo was fired from several different weapons, and they returned the lot because of severe tumbling issues. We've produced a couple million rounds in the past and this was NEVER an issue. From all the info that I've gathered, the consensus is that the crimp is too tight for this particular suppliers projectiles. What I did today was to make certain that the crimp was not too tight, and made 10 rounds using the projectiles that we've used in the past, and 10 from the new supplier. All 20 rounds were made to the same exact specs according to our ballistic recipe. We cleaned the weapon, and then loaded each set of 10 rounds into 2 separate magazines. We warmed the barrel by firing 5 rounds from it before we conducted our test. The 10 rounds that we fired from the old supplier did not tumble, The 10 we fired from the new supplier had 4 out of 10 tumble. We are ABSOLUTELY CERTAIN that it is not a crimp issue. Any thoughts. Link to comment Share on other sites More sharing options...
Sarge Posted March 5, 2019 Share Posted March 5, 2019 Go back to the old supplier? Link to comment Share on other sites More sharing options...
RJH Posted March 5, 2019 Share Posted March 5, 2019 If the new bullets are plated, they are probably undersize. Many times plated like to be a little oversize like lead Link to comment Share on other sites More sharing options...
AdamM Posted March 5, 2019 Share Posted March 5, 2019 That is what I was going to say. They are undersized diameter. Link to comment Share on other sites More sharing options...
JohnnyDog Posted March 6, 2019 Author Share Posted March 6, 2019 Both manufacturers projectiles are the same diameter and are within SAAMI specs. Can a CG issue cause tumbling do to poor lead or jacket placement? Link to comment Share on other sites More sharing options...
Maximis228 Posted March 6, 2019 Share Posted March 6, 2019 and you came to enos to find the answer... something doesn't add up here. Link to comment Share on other sites More sharing options...
JohnnyDog Posted March 6, 2019 Author Share Posted March 6, 2019 We are a relatively new company, (in business less than 3 years), without a ballistics lab. We are learning as we go, and this is a new issue. We will go back to our old manufacturer, but we are curious as to the cause of this issue. Link to comment Share on other sites More sharing options...
GrumpyOne Posted March 6, 2019 Share Posted March 6, 2019 It could be due to the ogive of the bullet. Shorter bullets need a slower twist rate to stabilze. Link to comment Share on other sites More sharing options...
RJH Posted March 6, 2019 Share Posted March 6, 2019 1 hour ago, JohnnyDog said: We are a relatively new company, (in business less than 3 years), without a ballistics lab. We are learning as we go, and this is a new issue. We will go back to our old manufacturer, but we are curious as to the cause of this issue. Were the old bullets plated ? Are the new bullets plated? Link to comment Share on other sites More sharing options...
Jim Watson Posted March 8, 2019 Share Posted March 8, 2019 I am sorry to say I can't help. All I can say is that this happens fairly often. There is always a lot of theorizing but unless it is some gross departure from spec, usually undersize, there is never a firm conclusion. Link to comment Share on other sites More sharing options...
Solvability Posted March 8, 2019 Share Posted March 8, 2019 (edited) I speculate the new bullets are harder and are not obturating on firing and thus not getting stabilized. You could try a faster powder to see if it works but do not go overpressure as 40 is a bit tricky in hoop strength. Edited March 8, 2019 by Solvability Link to comment Share on other sites More sharing options...
Miranda Posted March 8, 2019 Share Posted March 8, 2019 It does not seem an odd place to find guidance for ballistic problems. I'd go down the list of usual causes of tumbling. leading causes are already mentioned and the firearm causes are off the list As you have a clear cause in 'new' bullets, check dimensions. as far as a "lab" goes, your company has one... miranda Link to comment Share on other sites More sharing options...
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