Stringing

I searched the topic and tried some of the suggestions but I don't seem to be getting anyhwere.

My VLP…..once a consistently sub-3/4” rifle…..is now suffering from chronic vertical stringing. Round count is just under 700.

I’ve shot it clean and dirty. I’ve switched the ammo I was using when I noticed it, the old ammo still shoots well from the AR and this ammo shoots sub-moa from my son's 110 all day long……..and was my 2010 PD load for this rifle.

The action is bedded, the barrel and tang are free floated. I double checked the screws on the base and the rings as well as the action screws.

I shot this target below just a few minutes after shooting a few other rifles, same conditions and from the same rest. Everything else shoots fine.

I noticed this happening this past July. It was not doing it when I confirmed my loads for our 2012 PD venture.

I’ve been reading about vertical stringing and I’m trying to eliminate all possibilities. It’s a heavy barrel, heavy laminate stock, I haven’t made any changes to it. I bedded it after the problem started.

The only thing I haven’t done is change the scope (It’s a 6.5-20 Zeiss). I guess it’s possible that something could have happened to it on the flight out or back but, it was packed in a Pelican case for the ride….but it’s possible.

I’ve read that firing pin tension (spring) could cause it ?? The primers are well-struck, if anything maybe a little hard. But I’d think it would gradually get a weaker strike, not a harder one. This a pretty much a stock 12VLP.

Again, it hasn't always done this but, I'm darned if I can figure out what's causing it now. What the heck am I missing ??

http://i227.photobucket.com/albums/d...224_113539.jpg

Check the shooter.

How are shooting? Bench, prone, etc.

Make sure you're consistent with posture, grip, etc.

What caliber is it?

Quote:

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Again, it hasn't always done this but, I'm darned if I can figure out what's causing it now. What the heck am I missing ??

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Switch the scope even if you don't think that is what the problem is. If you have another stock that will work, try that one. If you have not already done so, play with the torque on the front and rear receiver bolts.

If all else fails, cuss it!

Shovelhead,
If you're sure its not the load (tested in other rifles) and the scope checks out OK, I'm guessing one of two things is happening:
1. you've gotten to the stage in life of that barrel where it's running alot faster than it was when you developed the load and that load is not in tune for your barrel anymore, or
2. you have some hard carbon accumulation in the throat, immediately in front of the case neck that's playing havoc on pressures.

I've had both happen before with identical results. Changing the load to keep in tune with the barrel life is relatively easy. I wish the same was true for removing the hard carbon - it's a chore to take out. You can loosen it up by soaking with Kroil, then using brush and abrasives (like JB Bore Paste) just in the throat, but you really have to work at it to get it out. I think I had some luck with Seafoam Deep Creep (kind of the marine equivalent of GM TEC), but was doing a bunch of things to remove it and can't be sure which worked the best - some of them were pretty aggressive....
Elkbane


How many rounds you have down that tube? What cartridge?

It's a .223

From the bench, front rest, rear bag. I had a few other rifles with me yesterday and they were all shooting well.

This is a 4.40" CF.....it's the only stock I don't have an extra of.

I'm going to swap out the scope and hit the range Sat.

Again, this just started a few months ago, at the PA Shootout as a matter of fact. That's where I first noriced it anyway. It was right after getting back from CO.

Prior to that it always shot very well.

Let us know how the scope change works. If scope is fine, I'd look for some factor that has changed PROGRESSIVELY through use, which is why I mentioned what I did.......the first time I noticed this was with a 7mm-08 with about 400 rounds through it, and I just had to retune the load. The second time was a 22-250 (hard carbon) and it soon got extreme enough to start dropping primers and blowing up bullets, but the first symptom (which I missed) was vertical stringing.

I've also seen it happen (vertical) from donut formation, which causes differential neck tension case to case (resulting in different pressure), but you said the ammo works fine in other rifles so we'll leave that one alone for now....
Elkbane

Have you tried it with commercial ammo to rule out any reloading issues?

No commercial ammo but both of the loads I run through this still shoot the same in the other rifles I use it in.

I took both out last week and picked them randomly out of the ammo box to rule out a progressive problem with my ammo.

Both my son's 110 and my varmint AR stil shoot the ammo normally.

OK, no ammo issues then. I would look at your scope and mounts. Try another scope on this rifle and that scope on another rifle.

Ahhggg.......banging head on desk......I did change the ammo (slightly)

This barrel likes them loaded long and I had my 2010 ammo loaded that way.

When I switched over to the 55gr I shortened up the 50gr stuff because it would drag in the blind mag of my son's 110.

The 55gr is loaded mag-length for the AR so those are short too. Thank God I keep good notes !!!

I'm going to load a few rounds long per my earlier data and see what that yeilds.

Thank you for kick-starting my brain.

I was going to say, its got to be something simple, that thing was shooting great for you out in CO.

Checked all my data.....this current load is seated .040 shorter than my 2010 load. Yikes.

Loaded up ten last night.

Let's try this again.

I agree with boots. Most problems are simple things, but we always try to make them difficult by chasing the tough fixes.

Vertical stringing is almost always a load issue. Good luck with it.

I followed my data and loaded a few long......no difference.

Double checked the base screws and swapped the scope.

I'm hitting the range with some 52gr SMKs from my Service Rifle.

Find a way to turn your case necks;trim your brass. Keep the sun off of your gun and ammo. Space your shots to two minuts; don't leave a rond in a warm chamber longer than 30 seconds without firing. If that doesn't help, check bedding screw torque. Map where each shot lands in a string. Don't I've up.

Gave it a good soaking with Wipe Out overnight. Got a tiny bit of blue but, very little, nothing that should effect accuracy.

Hitting the range tomorrow with a different scope and my Match Ammo.

Use a chonograph to check your velocity for spread.

I was clocking my loads that were stringing last week...6 shots, 56 fps spread.

A little windy today but, wanted to get back at it.

I gave it a REALLY good cleaning and also swapped out the scope and rings.

This is a 8 shot group with the same ammo I had been using.

I'm going to put the original scope and rings back on tomorrow and see if the stringing returns, just to confirm that was the problem.

http://i227.photobucket.com/albums/d...467a964edb.jpg

Glad there is a happy ending.

Sean

Put the original scope back on......stringing came back.

Absolutely the scope.

Glad you figured it out! FYI-off the bench your front rest and or rear bag(too hard, too tight etc.) can induce vertical stringing as can your hold. Try gripping the forend and then shoot a free recoil!

I'll be watching for the scope on classifieds....lol.

Glad you got that figured out. Too bad it was the scope and not just a simple load problem though.

It's on it's way back to Zeiss this morning.

They were way cool.