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Posted: 3/7/2010 3:03:00 PM EDT
http://i148.photobucket.com/albums/s30/Unionvillelacrosse10/overstab.jpg

Today I was shooting 55 grain FMJ Hornadys from a 1 in 7 twist Colt HBAR at 25 yards. I began to notice these small pinholes above some of the main bullet holes. Is this indicative of overstabilization
Link Posted: 3/7/2010 3:09:56 PM EDT
I would say either you change your sight picture or you need to watch your breathing, but that's just my opinion.
Link Posted: 3/7/2010 3:13:29 PM EDT
What is your backstop behind the target because those holes/tears look like they have the exit  in front of the target and are not entry holes.
Link Posted: 3/7/2010 3:16:15 PM EDT
I agree it looks like those small holes or tears and from the backside and not from a projectile.
Link Posted: 3/7/2010 3:17:00 PM EDT
Good point.  The backstop was plywood that was really chewed up (shot up) and rough.  But, we did notice it only happened with some shots.
Link Posted: 3/7/2010 3:18:04 PM EDT
[Last Edit: 3/7/2010 3:30:22 PM EDT by nbons]
What was behind the target?  Looks like you hit a rock or something hard behind the target and got debris flying back.  

ETA:  Little slow writing that up.  Agree with above.
Link Posted: 3/7/2010 3:20:53 PM EDT
I get that a ton when shooting with PW backing.
Link Posted: 3/7/2010 3:24:14 PM EDT
Originally Posted By msprague86:
I would say either you change your sight picture or you need to watch your breathing, but that's just my opinion.


Link Posted: 3/7/2010 3:31:43 PM EDT
[Last Edit: 3/7/2010 3:33:25 PM EDT by AK_Steve]
So they were secondary projectiles. pieces of plywood exploding off of the impact site. that would make sense.
Link Posted: 3/7/2010 3:34:29 PM EDT
Overstabilization would not manifest itself at that range.  Overspinning the bullet to the point of disintegration is another matter.

In any case, you got good answers above.
Link Posted: 3/7/2010 3:49:11 PM EDT
As I said earlier. I get that all the time where I shoot. We work a ton of construction sites and get sheets of the stuff all the time. So we usually just tack targets to the plywood and shoot it until we get too lazy picking it up. BUT the shrapnel out the back is brutal! Plus it also forces pieces out the front.
Link Posted: 3/7/2010 4:22:06 PM EDT
That is pretty common when targets are on plywood
Link Posted: 3/7/2010 4:42:52 PM EDT
I don't think you can "overstabilize" - that doesn't make sense.
Link Posted: 3/7/2010 5:38:37 PM EDT
Originally Posted By MMcfpd:
I don't think you can "overstabilize" - that doesn't make sense.


Spin it too fast, exceed the limitations of the projectile, and it will fail.  Or you can do the reverse.   Same result
458
Link Posted: 3/7/2010 5:44:08 PM EDT
I understand that, but a projectile that disintegrates is hardly "over" stabilized.
Link Posted: 3/7/2010 5:45:07 PM EDT



Originally Posted By fxntime:


What is your backstop behind the target because those holes/tears look like they have the exit  in front of the target and are not entry holes.


Agreed, looks like shrapnel blast from hitting the backstop...



 
Link Posted: 3/7/2010 7:04:34 PM EDT
I shot on plywood Saturday but taped cardboard on the front to make it easier to pull staples when I pulled targets. Just a thought for you.
Link Posted: 3/7/2010 7:12:34 PM EDT
I've shot much lighter bullets from 1/7 without ever having "overstabiliization".  It's usually something people worry about that don't have anything better to worry about.  I hear it's possible with some ballistic tip 45's but I've shot 45's before and never had a problem.  Just keep shootin!
Link Posted: 3/7/2010 7:23:37 PM EDT
If you under stabilize a bullet it will become unstable and tumble.  We all know that.  If you over stabilize a bullet it does have an affect but not until long range.  There was a long article done on this in the FCSA VHP magazine.  Let's say you are shooting at 1000 yards.  With a bullet properly stabilized the centerline of the bullet would stay in the line of travel along the arc.  Bullet nose pointing up as the bullet goes above the line of sight, then pointing down as the bullet falls back toward earth (target).  In an over stabilized bullet the bullet nose would be pointing up even though the bullet itself was traveling down.  The impact on paper would look like a keyhole or slight keyhole, depending on the angle of the bullet impacting the target.  This is really hard to type out and I cannot do drawings.  The best way I can describe it is you know that if you are shooting at very long range, you are shooting so the bullet is traveling up above the line of sight.  So as the bullet arcs up its nose is pointed up.  At the top of the arc where it flattens out a little, in a normal stabilized bullet the point of the bullet would flatten out the same as the arc, and as the arc started down the bullet point would start pointing down also.  In the over stabilized bullet the bullet tip continues to point up instead of down but it does not tumble.  
I hope I have not botched up the explanation too much but if you can find an index of back issues of VHP and find the article they do a lot better job of describing it and they have pictures.
Link Posted: 3/7/2010 7:43:30 PM EDT
[Last Edit: 3/7/2010 7:44:44 PM EDT by peligro113]
Originally Posted By Captains1911:
Originally Posted By msprague86:
I would say either you change your sight picture or you need to watch your breathing, but that's just my opinion.




Lol another ARFCOM expert
Link Posted: 3/8/2010 7:32:44 AM EDT
Not over-stabilization.  
Link Posted: 3/8/2010 7:48:11 AM EDT
Originally Posted By Big-Bore:
If you under stabilize a bullet it will become unstable and tumble.  We all know that.  If you over stabilize a bullet it does have an affect but not until long range.  There was a long article done on this in the FCSA VHP magazine.  Let's say you are shooting at 1000 yards.  With a bullet properly stabilized the centerline of the bullet would stay in the line of travel along the arc.  Bullet nose pointing up as the bullet goes above the line of sight, then pointing down as the bullet falls back toward earth (target).  In an over stabilized bullet the bullet nose would be pointing up even though the bullet itself was traveling down.  The impact on paper would look like a keyhole or slight keyhole, depending on the angle of the bullet impacting the target.  This is really hard to type out and I cannot do drawings.  The best way I can describe it is you know that if you are shooting at very long range, you are shooting so the bullet is traveling up above the line of sight.  So as the bullet arcs up its nose is pointed up.  At the top of the arc where it flattens out a little, in a normal stabilized bullet the point of the bullet would flatten out the same as the arc, and as the arc started down the bullet point would start pointing down also.  In the over stabilized bullet the bullet tip continues to point up instead of down but it does not tumble.  
I hope I have not botched up the explanation too much but if you can find an index of back issues of VHP and find the article they do a lot better job of describing it and they have pictures.


Your explanation is very clear.
Link Posted: 3/8/2010 8:06:48 AM EDT
Originally Posted By 1saxman:
Originally Posted By Big-Bore:
If you under stabilize a bullet it will become unstable and tumble.  We all know that.  If you over stabilize a bullet it does have an affect but not until long range.  There was a long article done on this in the FCSA VHP magazine.  Let's say you are shooting at 1000 yards.  With a bullet properly stabilized the centerline of the bullet would stay in the line of travel along the arc.  Bullet nose pointing up as the bullet goes above the line of sight, then pointing down as the bullet falls back toward earth (target).  In an over stabilized bullet the bullet nose would be pointing up even though the bullet itself was traveling down.  The impact on paper would look like a keyhole or slight keyhole, depending on the angle of the bullet impacting the target.  This is really hard to type out and I cannot do drawings.  The best way I can describe it is you know that if you are shooting at very long range, you are shooting so the bullet is traveling up above the line of sight.  So as the bullet arcs up its nose is pointed up.  At the top of the arc where it flattens out a little, in a normal stabilized bullet the point of the bullet would flatten out the same as the arc, and as the arc started down the bullet point would start pointing down also.  In the over stabilized bullet the bullet tip continues to point up instead of down but it does not tumble.  
I hope I have not botched up the explanation too much but if you can find an index of back issues of VHP and find the article they do a lot better job of describing it and they have pictures.


Your explanation is very clear.


agreed

Although I will add this:

You can spin the jackets off shitty bullets with a 1/7 twist barrel. American ammunition brand for example. I made the sorry mistake of shooting some of this stuff through a suppressor. It really screwed it up (gilding metal separated and struck the baffles). This also resulted in really poor accuracy, of course. When it did hit the paper I didn't see any spattering like you show. I have seen spattering like that when the backstop was something that couldn't be penetrated. I get it a lot with my steel plate targets, the kind that use an electric motor to reset. I made them out of inconel plate left over from some grain handling equipment I built for the farm but I suspect anything that stops the bullet with very little penetration would do it. Bullet fragments would still have a lot of energy and have nowhere to go but back the way they came.
Link Posted: 3/8/2010 8:16:48 AM EDT
Over stabilization. Think about what you just said.

Link Posted: 3/8/2010 8:50:54 AM EDT
I agree.  Poor choice of terms.  I think most posters get what I was asking––were the marks I referenced in the photos the result of the 55 grain FMJs we were shooting coming apart and fragmenting because the 1 in 7 twist barrel was too fast.  Consensus was no, which was all I really wanted to know.
Link Posted: 3/8/2010 9:01:29 AM EDT
I'll just leave this here.  

overspin [′ō·vər‚spin]
(mechanics)
In a spin-stabilized projectile, the overstability that results when the rate of spin is too great for the particular design of projectile, so that its nose does not turn downward as it passes the summit of the trajectory and follows the descending branch. Also known as overstabilization.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

Link Posted: 3/8/2010 10:10:53 AM EDT
Originally Posted By 1saxman:
Originally Posted By Big-Bore:
If you under stabilize a bullet it will become unstable and tumble.  We all know that.  If you over stabilize a bullet it does have an affect but not until long range.  There was a long article done on this in the FCSA VHP magazine.  Let's say you are shooting at 1000 yards.  With a bullet properly stabilized the centerline of the bullet would stay in the line of travel along the arc.  Bullet nose pointing up as the bullet goes above the line of sight, then pointing down as the bullet falls back toward earth (target).  In an over stabilized bullet the bullet nose would be pointing up even though the bullet itself was traveling down.  The impact on paper would look like a keyhole or slight keyhole, depending on the angle of the bullet impacting the target.  This is really hard to type out and I cannot do drawings.  The best way I can describe it is you know that if you are shooting at very long range, you are shooting so the bullet is traveling up above the line of sight.  So as the bullet arcs up its nose is pointed up.  At the top of the arc where it flattens out a little, in a normal stabilized bullet the point of the bullet would flatten out the same as the arc, and as the arc started down the bullet point would start pointing down also.  In the over stabilized bullet the bullet tip continues to point up instead of down but it does not tumble.  
I hope I have not botched up the explanation too much but if you can find an index of back issues of VHP and find the article they do a lot better job of describing it and they have pictures.


Your explanation is very clear.


Agreed.
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