bbncu Posted May 6, 2011 Share Posted May 6, 2011 Hello Guys, Help me diagnose the problem I'm having with my open gun. I'm baffled why my bullets tumble when I shoot beyond 10 yards...@ 20 yards, I have a sideways hole on my target...BTW, my gun had no problems with 115 grainers Montana Golds FMJs and JHPs I used before but now, I'm trying to make a recipe for my 124 MGs FMJs and I have the same setup for everything except for the bullet weight and this problem came up... Gun: STI/SV 2011 38 super with Barsto Barrel; 3 popple holes; 3 port/4 small ports on the side aluminum comp. Powder: Accurate# 7 (this has always been the powder I'm using) Primers: Winchesters small rifle Brass: mixed headstamp +P 38 super OAL: 1.255 Crimp:.378-.379 Reloader: SDB Load: 10.5 grains of AA#7 chronoed @ 159 PF (need to bump up) Bullets: Montana Golds 124 gr. FMJ .355 diameter So what you guys think..I checked my compensator and see if my bullet is hitting the baffles but it is not...I'm just looking around on my reloading stuff and see if I can find some more 115 grainers to check if it really has something to do with the bullet weight... Link to comment Share on other sites More sharing options...
whistlepig Posted May 6, 2011 Share Posted May 6, 2011 Have you actually mic'd the bullets? It is rare, but the wrong size has been sold before. (my first thought was a comp problem, but you beat me to it.) Link to comment Share on other sites More sharing options...
bbncu Posted May 6, 2011 Author Share Posted May 6, 2011 Have you actually mic'd the bullets? It is rare, but the wrong size has been sold before. (my first thought was a comp problem, but you beat me to it.) Yup, measured the bullets, .355 Link to comment Share on other sites More sharing options...
hoserdude Posted May 6, 2011 Share Posted May 6, 2011 Did you change your crimp? Over crimped rounds will also tumble. Link to comment Share on other sites More sharing options...
bbncu Posted May 6, 2011 Author Share Posted May 6, 2011 Did you change your crimp? Over crimped rounds will also tumble. I haven't changed anything as to OAL and crimp settings... Link to comment Share on other sites More sharing options...
TMC Posted May 6, 2011 Share Posted May 6, 2011 Check the holes in your comp's plates for strikes, it could be that the heavier bullet isn't fully stabilized as its leaving the barrel or your aluminum comp is flexing from the increased torque of the heavier bullet and they are hitting the plates in the comp. When I built my gun it would group just fine but the bullets impacts on the targets looked like they were tumbling. Turns out they were was just barely nicking the middle plate in the comp. It was leaving the smallest mark on the plate. As soon as I ground that area the weird impacts stopped and now it leaves nice round holes. Link to comment Share on other sites More sharing options...
bbncu Posted May 6, 2011 Author Share Posted May 6, 2011 Check the holes in your comp's plates for strikes, it could be that the heavier bullet isn't fully stabilized as its leaving the barrel or your aluminum comp is flexing from the increased torque of the heavier bullet and they are hitting the plates in the comp. When I built my gun it would group just fine but the bullets impacts on the targets looked like they were tumbling. Turns out they were was just barely nicking the middle plate in the comp. It was leaving the smallest mark on the plate. As soon as I ground that area the weird impacts stopped and now it leaves nice round holes. Checked the holes and I think this might be it, there is a little golden stain @ 6 o' clock on the 3 baffle holes of the comp...I didn't notice it until I bore snaked the barrel and comp. I ground it down a bit with a dremel and I'll shoot it again tomorrow... I'm also going to bump the charge and will also load some 115's that I found and see if how it will turn out... Thanks for the ideas guys.. Link to comment Share on other sites More sharing options...
Powder Finger Posted May 6, 2011 Share Posted May 6, 2011 Check the holes in your comp's plates for strikes, it could be that the heavier bullet isn't fully stabilized as its leaving the barrel or your aluminum comp is flexing from the increased torque of the heavier bullet and they are hitting the plates in the comp. When I built my gun it would group just fine but the bullets impacts on the targets looked like they were tumbling. Turns out they were was just barely nicking the middle plate in the comp. It was leaving the smallest mark on the plate. As soon as I ground that area the weird impacts stopped and now it leaves nice round holes. Checked the holes and I think this might be it, there is a little golden stain @ 6 o' clock on the 3 baffle holes of the comp...I didn't notice it until I bore snaked the barrel and comp. I ground it down a bit with a dremel and I'll shoot it again tomorrow... I'm also going to bump the charge and will also load some 115's that I found and see if how it will turn out... Thanks for the ideas guys.. EGW comp reamer Link to comment Share on other sites More sharing options...
JerryShoots Posted May 7, 2011 Share Posted May 7, 2011 Great catch on the comp! I just looked at one of my single stacks for steel shooting and low and behold my comp has marks too. I have a few questions that may help... What is the twist rate of your barrel? I've seen some that do not recommend exceeding certain weights. Can you repeat the problem or has it only happened on one range visit? Was there anything between you and the target? Is there a difference in plating thickness between the 115's and 124's? Have you recovered any fired bullets to see if they melted partially in the comp? Any primer flow of the casings or any indicators of high or low pressures? You stated mixed headstamp. Did any of the casings have a military type headstamp? Cut down .223's do funny funny things. Maybe you shot through a passing bird like the Seattle Mariners pitcher! Link to comment Share on other sites More sharing options...
bbncu Posted May 7, 2011 Author Share Posted May 7, 2011 Great catch on the comp! I just looked at one of my single stacks for steel shooting and low and behold my comp has marks too. I have a few questions that may help... What is the twist rate of your barrel? I've seen some that do not recommend exceeding certain weights. Can you repeat the problem or has it only happened on one range visit? Was there anything between you and the target? Is there a difference in plating thickness between the 115's and 124's? Have you recovered any fired bullets to see if they melted partially in the comp? Any primer flow of the casings or any indicators of high or low pressures? You stated mixed headstamp. Did any of the casings have a military type headstamp? Cut down .223's do funny funny things. Maybe you shot through a passing bird like the Seattle Mariners pitcher! It was definitely the comp..shot it today with the same ammo from yesterday and no more tumbling...and accuracy back to normal... Link to comment Share on other sites More sharing options...
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