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Post by redfish on Jan 31, 2012 19:59:53 GMT -5
when a 5 shot group prints a near perfect verticle line of holes does that mean
that the barrel is at the top or bottom of its harmonic cycle?
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Post by ricksalisbury01 on Feb 1, 2012 14:40:03 GMT -5
It does not mean either.......I assume that this "stringing" is with all the same powder, powder weight, bullet, etc.,
I THINK you are trying to identify the harmonic position of the barrel by what is generally called a "ladder test." The ladder test requires a variation of powder loads that are shot at longer distances (say 300-600 yards) and one looks for a "group" that tightens up around a fairly narrow range of grain weight of powder. This accuracy node is commonly associated with the barrel in the "top" or "bottom" of the harmonic cycle when the bullet exits the barrel. The grain weight range of the node is then fine tuned for the greatest accuracy.
More than likely the vertical disposition that you are seeing is caused by the barrel heating up as you shoot. If you are shooting fast, take more time between shots to let the barrel cool down.
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Post by cuda on Feb 1, 2012 22:07:52 GMT -5
What gun what barrel what cal what speed of the load? There is more you could tell use. Are you shooting a 22 or a 50 cal or what?
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Post by redfish on Feb 2, 2012 9:41:59 GMT -5
rifle is 03 springfield completely overhauled. krieger 26" heavy varmint barrel action blueprinted by krieger
timney trigger (6 oz) leupold bases/mounts glass bedded in elk ridge stock (two inches of barrel also bedded).
have been shootin this rifle for two years now. have tried bullet weights from 40g to 64g with h380 varget benchmark imr 4007 ssc. seating bullets from .025 out .015 in. beginning to think it needs checked out by a good smith cause has never been consistent with any load.
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Post by youp50 on Feb 2, 2012 19:04:49 GMT -5
Barrel floating free? Put a little pressure on it with a matchbook. Not free? Try free floating it.
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Post by slugger on Feb 8, 2012 11:51:38 GMT -5
sounds more like an ignition or temp thing to me. Shoot it once let the gun cool to cold and shoot again, 5 times you will see if it is from temp.The same goes for the primer, I'll bet if you shot 5 times across the crono you will see a lot of speed difference.
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Post by rossman40 on Feb 9, 2012 0:07:28 GMT -5
I have to agree with Slugger to start off. Vertical stringing is usually a sign of erratic muzzle velocities. A chrono would show it if that is the problem. I've seen light primer hits from a weak firing pin spring cause that (still using the original spring?). What brass are you using? Look at getting the primer pockets and flash holes uniform. What caliber is this in? 22-250 or 220 Swift (if your shooting those light bullets)? I would say if you were still in 30-06 try a box of Federal Gold Medal match ammo and see how that shoots.
Flat bottom actions like the 1903, 98 Mauser, Winchester M70 and Ruger M77 can be a bear to get bedded. Since they are all based on the 98 they have the big lugs plus the huge extractor which tends to allow a lot of flex on the right rail
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Post by mike3132 on Feb 10, 2012 10:31:00 GMT -5
There are two things that generally cause vertical stringing and they are inconsistent ignition and stock bedding issues. Mike
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Post by olsmokey on Feb 10, 2012 22:06:40 GMT -5
It could also be caused by recoil. Free recoil and bag placement can cause vertical stringing. Try moving bags or using free hand on forearm.
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Post by rossman40 on Feb 11, 2012 15:53:52 GMT -5
I seen in your other post it is a 22-250. I would still look at your velocities thru a chrono. I would guess off hand a firing pin spring or firing pin issue. I see them all the time that still have the original spring (or at least the same one it left the service with) and some even that have never had the bolt tore down since it left the service. When looking one over I shoot some WD-40 in the firing pin hole and if it comes out red I warn the guy it might get expensive. The firing pin spring is actually pretty weak to start with, IIRC 15lb. If there is any gunk in the bolt it can slow the firing pin down. Then again you can have a spring that has been in the rifle for over 60 years.
If not that you may be looking at how you handling recoil, shooting style and then even stock geometry and balance. A real heavy barrel will mess you up when it kicks CG way forward, that is why benchrest stocks have longer forends. If you looking at a perfect vertical string I doubt if the bedding job is totally junk and your not shooting a heavy recoiler.
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Post by redfish on Feb 11, 2012 20:48:41 GMT -5
Firing pin spring and firing pin was replaced when rebuilt. The only visible problem is the firing pin hole in the bolt face is slightly off centered (not sure if that's a fixable problem).
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Post by Deleted on Mar 10, 2012 0:15:14 GMT -5
I have to agree with Slugger to start off. Vertical stringing is usually a sign of erratic muzzle velocities. A chrono would show it if that is the problem. I've seen light primer hits from a weak firing pin spring cause that (still using the original spring?). What brass are you using? Look at getting the primer pockets and flash holes uniform. What caliber is this in? 22-250 or 220 Swift (if your shooting those light bullets)? I would say if you were still in 30-06 try a box of Federal Gold Medal match ammo and see how that shoots. Flat bottom actions like the 1903, 98 Mauser, Winchester M70 and Ruger M77 can be a bear to get bedded. Since they are all based on the 98 they have the big lugs plus the huge extractor which tends to allow a lot of flex on the right rail rossman, when talking about erratic velocities, at what difference in velocity do you starting vertical stringing? 30 fps? 50 fps? is each gun effected differently from velocity variances? Thanks |
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Post by rossman40 on Mar 10, 2012 10:18:18 GMT -5
You get a SD up in 3 digits that will flat mess you up. But you also have to go back to the ignition start. Inconsistent ignition effects the pressure curve so the timing is off then that effects barrel harmonics. The thing is to shoot a string over a chrono to see if that is the problem. You could have firing pin problems, scale problems or even neck tension inconsistencies. If it is not a velocity problem then look for form or mechanical problems.
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Post by smokepoler on Jul 14, 2012 17:51:02 GMT -5
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Post by rossman40 on Jul 15, 2012 12:20:08 GMT -5
Redfish,, you ever find out what the problem was? Curious minds are dieing to know....
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