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Vertical stringing. What causes it?

M

mattp8893

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Minuteman
Feb 16, 2017
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26
#1
I'm having problems with vertical strings with my new build I'd still consider myself relative novice at reloading so what should I look at first. At 100 a 10 shot group was just over 1 moa in height but width was barley more than one bullet. Same at 1000 width wise they were perfect but height on it they spread to probably 4 moa. My load data is 6.5 creedmoor out of a 26 inch medium Palma bartlein. 140eld-m 42.8 grains of h4350. In prime brass


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#2
Do they trend upwards with heat? Or randomly up and down? And your stock/bedding situation? Does it shift up and down too much as you tighten and release the action screws?

Are you sure that you're in your node? You did a proper load work up? Have you chronoed them?
 
#3
It's torques to the specs listed in an mpa chassis it jumps back and forth. And yes I've done ladder tests and the current load is on the high end of the node but was still in there. Chronoded like 2820 with an sd of 15.7 can't remember the es. For reference shots 16-20 in the match were at a 1000 yard 45 inch gong with 1moa 10 ring 2 moa 5 ring. First shot in the 10 almost dead center 2-3 dropped about 12 inches strait under first shot. Come up 1 moa 4th in the black again and 5th drops right back in the group with 2-3


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#4
mattp8893 said:
It's torques to the specs listed in an mpa chassis it jumps back and forth. And yes I've done ladder tests and the current load is on the high end of the node but was still in there. Chronoded like 2820 with an sd of 15.7 can't remember the es. For reference shots 16-20 in the match were at a 1000 yard 45 inch gong with 1moa 10 ring 2 moa 5 ring. First shot in the 10 almost dead center 2-3 dropped about 12 inches strait under first shot. Come up 1 moa 4th in the black again and 5th drops right back in the group with 2-3


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Click to expand...


An SD of 15.7 is pretty high for 1000 yard shooting. If you know that everything on the rifle is good, I'd say that your vertical stringing is coming from variations in velocity.
 
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#5
The SD was my concern reading this as well. Now 15fps wouldn't account for an inch of movement at 100yds, but at 1000yds 15fps with my pet load according to ballistic AE works out to a 5" difference drop
 
#6
things ive seen for vertical...assuming the rifle is A+ and good to go
breathing (mainly if prone)
inconsistent loading of the bipod or shoulder pressure into the rifle
if using a rear bag, giving up on the shot...basically relaxing the rear bag hand at the same time the trigger is pressed (if its this you should be able to see it on recoil...your rifle will be pointed high after the recoil impulse)

if its the load velocity deviations, it would show at distance...not 100 yds like you have it...if its at 100 its either the rifle itself or the shooter...check to make sure nothing is binding or making contact where it shouldnt be
 
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#7
I wondered if it might be neck tension helping cause some of the sd problems. Long story short I set up my own bench finally instead of loading on my dads and bought cheaper dies. The bullets felt much harder to seat than they normally do. Also it's off a bench so not loading the bipod and bag was completely relaxed before even shot.


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#8
The best way to get the sd down? I'm running a charge master currently. This gun was really built to be my first prs gun but the bench rest match I've always shot came up before my first prs I'm signed up for did so I figured it would be a good time to get some good dope


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#9
morganlamprecht said:
things ive seen for vertical...assuming the rifle is A+ and good to go
breathing (mainly if prone)
inconsistent loading of the bipod or shoulder pressure into the rifle
if using a rear bag, giving up on the shot...basically relaxing the rear bag hand at the same time the trigger is pressed (if its this you should be able to see it on recoil...your rifle will be pointed high after the recoil impulse)

if its the load velocity deviations, it would show at distance...not 100 yds like you have it...if its at 100 its either the rifle itself or the shooter...check to make sure nothing is binding or making contact where it shouldnt be
Click to expand...

Spot on! that was my thought exactly. its an NPA issue.
 
#10
NY700 said:
The SD was my concern reading this as well. Now 15fps wouldn't account for an inch of movement at 100yds, but at 1000yds 15fps with my pet load according to ballistic AE works out to a 5" difference drop
Click to expand...

That would be 30 fps, wouldn't it? +/- 15?
 
#11
vh20 said:
That would be 30 fps, wouldn't it? +/- 15?
Click to expand...

close but thats not exactly how standard deviation works...

68% of shots would fall into +/- 1SD (so +/- 15 fps)
95% into +/- 2SD (so +/- 30 fps)
and 99.7% into +/- 3SD (+/- 45 fps)

needless to say an SD of 15 is a little much for what i like...i like to keep it between 5-10
 
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#12
mattp8893 said:
The best way to get the sd down? I'm running a charge master currently. This gun was really built to be my first prs gun but the bench rest match I've always shot came up before my first prs I'm signed up for did so I figured it would be a good time to get some good dope


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Click to expand...

neck tension could be the issue if you changed dies...bullets shouldnt be hard to seat at all...they should slide in nice and smooth with not much effort
 
#13
thats how they have always been. what im running forster non bushing dies now but was running bushing dies. whats the best way to fix neck tension? turn the necks or go back to bushing dies and find my correct bushing? for the time being and probably a while in the future this will be the only gun loaded for with these dies. this may be nothing but just my guess on checking neck tension but i measured the inside of the neck at .260 so shooting a .264 bullet wouldnt that mean i had .004 of neck tension?
 
#14
Actually went back and just looked at some I primed and never loaded from
The same batch I had he problems with and the inside of the neck on them measure .254-.255 I would think that much difference could definitely affect it


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#15
To find the right bushing you would first want to know how much tension you desire to run. Most people choose .002. So you would measure a loaded rounds neck outside dimension and subtract .002 from it and then select that bushing. If you like .004 then thats your prerogative.

While the difference will be correct for identifying how much tension youre running measuring the inside diameter its not going to provide the actual number you want for bushing selection which interacts with the outside of the brass. Im going to guess that your brass is .015 thick so your outside number of a loaded round would be .264+(.015*2) for an outside dimension of .294. This is all speculative though and it depends on your particular components. With these estimates for brass thickness I would select a .288 bushing to achieve the .002 goal neck tension I referred to earlier. If your outside actual brass thickness is .012 then it would be .264+(.012*2) for a measure of .288 then I would select a bushing of .286.

I think your brass measuring .254 compared to a .260 will be too much neck tension but hey, if you developed a load at that level and they shot great at that amount of tension then hell, go for it. I suspect that the difference in your neck materials hardness and elasticity would be too variable expanding that much around the bullet though to provide you with consistent tension round to round (especially since theres no annealing) which could vary well be contributing to your velocity dispersion. The less size induced tension the more consistent your results will be as the margins the material would have to over come are mitigated.

I still dont think that the neck tension would cause a vertical trend at all distances, I figure it would have a more horizontal component to it as well. But maybe thats just how that particular load combo and your rifle behave. Measure your outsides, select the appropriate bushing and then take those loads out again on a nice morning without too much wind and without too much coffee that brings out the shakes and focus on getting the rifle in the bags and on the bipod. Or stick with the Forster and send it in to get reamed to the appropriate diameter for your brass along with the correct expander ball.
Turning necks would be the last thing I resorted to as a fix for the die in a no turn chamber, it will just expand upon firing however much more you took off necessitating that much more working of the brass to get it back down to size.
 
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#16
Thank you for all the help! I think I'll definitely pick up a bushing die. I measure one loaded round a day or two ago and believe it was either .291 or .292 so looks like I'll be having to find a bushing die and the appropriate bushing now.


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#18
mattp8893 said:
thats how they have always been. what im running forster non bushing dies now but was running bushing dies. whats the best way to fix neck tension? turn the necks or go back to bushing dies and find my correct bushing? for the time being and probably a while in the future this will be the only gun loaded for with these dies. this may be nothing but just my guess on checking neck tension but i measured the inside of the neck at .260 so shooting a .264 bullet wouldnt that mean i had .004 of neck tension?
Click to expand...

You can't accurately measure the inside of the neck using a dial caliper. You should measure your sized unloaded neck and compare it to your loaded neck.

.004" tension can be excessive depending on the condition of the neck's inner surface. These two variables control seating pressure together. The higher the tension the higher the seating pressure. The rougher the neck, the higher the seating pressure. You could lube the neck or decrease tension, or both.

Turning the neck isn't going to work. A FL die sizes the neck way too much for neck wall thickness to affect seating pressure. A bushing die is a better solution. An even better solution is a Lee collet neck die with several different diameter mandrels.
 
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#21
morganlamprecht said:
close but thats not exactly how standard deviation works...

68% of shots would fall into +/- 1SD (so +/- 15 fps)
95% into +/- 2SD (so +/- 30 fps)
and 99.7% into +/- 3SD (+/- 45 fps)

needless to say an SD of 15 is a little much for what i like...i like to keep it between 5-10
Click to expand...

Yeah, I know what the 3-sigma rule is. My point was that (keeping it simple and staying out of the weeds) the ES would be at least double the SD, not the same-as, which would mean that the amount of vertical stringing attributable to velocity deltas would be much more than he was figuring.
 
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#22
Once I get this insane amount of neck tension figured out I'm hoping to check and see how it does and if I'm still having problems that'll be my next check for sure but since I found out that I had .009-.010 of neck tension on the brass I shot in the match I figure it has to have something to do with it


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#23
Thought I would share my findings from this whole ordeal and my lessons learned which I'm sure most of y'all already knew but maybe it'll help some of the newer guys like me here. I decided to do a little test since I already had 5 loaded from the load with the huge neck tension (.010) 5 after I reset the die which was still giving me about .004 neck tension and then loaded 5 with 002 neck tension that I fixed with an expander since the correct die and bushing isn't here yet. All other load specs are identical besides neck tension. I shot all these under a magnetospeed..010 neck tension shot a 5 shot group of roughly 1 inch and had an sd of 19. The group of .004 neck tension shot just under 3/4 of an inch with an sd of 11 and while fighting a cold today with the load with .002 neck tension two different groups both were right at 1/4 of an inch both with sd's in single digits I believe 6 and 8 were the numbers on them. Overall I learned a huge lesson on correct neck tension and how much it can affect a group even at just 100 yards.


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#24
918v said:
An even better solution is a Lee collet neck die with several different diameter mandrels.
Click to expand...

+1 on the Lee collet die. Most Lee collet die mandrels as shipped only provide for about .001" neck tension. I have mine lighty sanded down to provide about .0015-.002" tension. Any more neck tension than this and SDs go up and bullet tip runout after seating increases.

I started out with a bushing die, but no matter what I did, I always ended up with excessive runout at the bullet tip. Runout practically disappeared with the collet die.
 
#25
Is that lee collet die available in 6.5 creedmoor? You'd think so but I'm not seeing it offered on midway or sinclair's website. All kinds of random calibers and all the ones you would expect except for the 6.5 creedmoor


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#26
mattp8893 said:
Is that lee collet die available in 6.5 creedmoor? You'd think so but I'm not seeing it offered on midway or sinclair's website. All kinds of random calibers and all the ones you would expect except for the 6.5 creedmoor
Click to expand...

The only place I've seen it available for purchase by itself is on the Lee Precision website.

I contacted Midway months ago about carrying it and they said they'd look into it. I think they just blew me off with a form-letter email. :rolleyes:

Here is a direct link. I could not find it searching from my phone.

Lee collet dies: http://leeprecision.com/reloading-di...zing-die-only/
 
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#27
mattp8893 said:
I'm having problems with vertical strings with my new build I'd still consider myself relative novice at reloading so what should I look at first. At 100 a 10 shot group was just over 1 moa in height but width was barley more than one bullet. Same at 1000 width wise they were perfect but height on it they spread to probably 4 moa. My load data is 6.5 creedmoor out of a 26 inch medium Palma bartlein. 140eld-m 42.8 grains of h4350. In prime brass


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Click to expand...

Personally, I would never accept a 1 moa group in load development and NEVER with a vertical shape like you're describing. I'd accept a horizontal dispersion before vertical, and chalk it up to shooter error or wind; but never horizontal. I hunt for a cloverleaf type of dispersion. I don't care how 'narrow' the group, if the holes are stacked on top of each other, why would you not expect similar results at distance, only amplified? My suggestion is to go back to development. I'd look back in your notes and look for your best groups with a cloverleaf or more rounded grouping and start there. Or, possibly, play with your seating depth. Make sure you're meticulous in you're brass prep.

Good luck! More work with load development and I'll bet you can get it shooting well under 1moa.


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#32
MachoKing said:
I'm going to suggest a Whidden die. It uses a bushing but also has an expander ball and they are very nice dies.
Click to expand...

Sorry here, but most Whidden expander balls are over size, so why not just set neck tension with the bushing and be done. They also sell a high priced expander ball kit for a premium price, see the picture.
 
#33
SouthTXBowhunter said:
Personally, I would never accept a 1 moa group in load development and NEVER with a vertical shape like you're describing. I'd accept a horizontal dispersion before vertical, and chalk it up to shooter error or wind; but never horizontal. I hunt for a cloverleaf type of dispersion. I don't care how 'narrow' the group, if the holes are stacked on top of each other, why would you not expect similar results at distance, only amplified? My suggestion is to go back to development. I'd look back in your notes and look for your best groups with a cloverleaf or more rounded grouping and start there. Or, possibly, play with your seating depth. Make sure you're meticulous in you're brass prep.

Good luck! More work with load development and I'll bet you can get it shooting well under 1moa.


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Click to expand...

These were the groups from yesterday with the proper neck tension the three shot was touching the lands and the 5 shot was .005 off on the three shot I made a stupid mistake and wasted the first two forgetting I had taken my gun out of the chassis and had to get it back close I believe they'll tighten up alittle more than that as I've been fighting a cold the last half of the week
a08cdb9e438426a8cda93d998ae60969.jpg
f01deac8c5035ff658d839d9fd943018.jpg



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#35
ar223 said:
Looks like you got it figured out. Now to stretch it out to see for sure
Click to expand...

I shot it twice at 500 on an 8 inch circle plate. First shot dead center. Second shot apparently hit the pistol lock where it goes through the hole in the top that holds the plate up cause it did a couple back flips and hit the ground so that ended my shooting for the day


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#37
morganlamprecht said:
things ive seen for vertical...assuming the rifle is A+ and good to go
breathing (mainly if prone)
inconsistent loading of the bipod or shoulder pressure into the rifle
if using a rear bag, giving up on the shot...basically relaxing the rear bag hand at the same time the trigger is pressed (if its this you should be able to see it on recoil...your rifle will be pointed high after the recoil impulse)

if its the load velocity deviations, it would show at distance...not 100 yds like you have it...if its at 100 its either the rifle itself or the shooter...check to make sure nothing is binding or making contact where it shouldnt be
Click to expand...

This ^^^^^

.


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#38
Necro thread. But I have been fighting vertical lately. I raised my bipod to get more of my chest off the ground. I then wrapped my thumb around the pistol grip. I found when putting my thumb on the shelf I was pushing forward with my thumb while squeezing the trigger.
 
#44
morganlamprecht said:
things ive seen for vertical...assuming the rifle is A+ and good to go
breathing (mainly if prone)
inconsistent loading of the bipod or shoulder pressure into the rifle
if using a rear bag, giving up on the shot...basically relaxing the rear bag hand at the same time the trigger is pressed (if its this you should be able to see it on recoil...your rifle will be pointed high after the recoil impulse)

if its the load velocity deviations, it would show at distance...not 100 yds like you have it...if its at 100 its either the rifle itself or the shooter...check to make sure nothing is binding or making contact where it shouldnt be
Click to expand...

Since people bringing it back up, this answer is still the way to go.
 
#46
Dthomas3523 said:
Since people bringing it back up, this answer is still the way to go.
Click to expand...
I am pretty sure I have a problem with " if using a rear bag, giving up on the shot...basically relaxing the rear bag hand at the same time the trigger is pressed (if its this you should be able to see it on recoil...your rifle will be pointed high after the recoil impulse)"

Either that or the butt stock is too low on my body and recoil is pushing it down, but it happens with a heavy 22lr so... probably not that? I think I am going to set up a gopro to be pointed at my support hand the next time I go out and see if it catches me in the act. (It does not happen during dry fire practice).
 
#47
Dry fire your mind knows what is going on. Get the rear supported really good. So that you are not using your rear hand. Try it. That is what I had to do. Good luck!
 
#49
_Raining said:
I am pretty sure I have a problem with " if using a rear bag, giving up on the shot...basically relaxing the rear bag hand at the same time the trigger is pressed (if its this you should be able to see it on recoil...your rifle will be pointed high after the recoil impulse)"

Either that or the butt stock is too low on my body and recoil is pushing it down, but it happens with a heavy 22lr so... probably not that? I think I am going to set up a gopro to be pointed at my support hand the next time I go out and see if it catches me in the act. (It does not happen during dry fire practice).
Click to expand...
I like to envision myself holding the trigger pull and hold as the bullet is flying to the target till impact.
like I’m guiding a missile.
 
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