90g Berger VLD's tumbling in a 6.5 twist barrel after some time ????

[r bose]

First the background. 30" Pac Nor 3 grove barrel. For several years I've been shooting 90's with success. Then last weekend shooting 600 yds I was told by my pit puller I had 2 bullets come in sideways along with some other oblong holes(3rd string) (very off call shots). This was after shooting a 199-9x prone my first string. Perplexed, (only about 2000 rounds thru barrel) I went home, scrubbed the barrel, used JB bore paste to remove any possible carbon, and cleaned as good as I could thinking a dirty bore/carbon ring might have caused this.

Shot yesterday at 600 and same thing first string. My 2 sighters and the first 5 shots were off call but I thought I needed to "season" the bore. But the next 15 shots were not good with 2 obvious sideways bullets and a few oblong "yalling" bullet holes BUT....most went in straight???. I knew the barrel would give up accuracy but didn't think it would destabilize the bullet??

Now the questions.....

Why not all bullets destabilizing??

Why not just a loss in accuracy with straight bullet holes in the target??

My load is a bit warm but never dangerously hot but I has several issues trying to open the bolt and getting the spent case out???

Appreciate any help or suggestions or answers to an obvious problem.

 

[Eddie Harren]

I would try a new crown.

 

[mikecr]

My guess is bullet jacket damage from the barrel.

 

[r bose]

Eddie, first thing I did was examine the crown. No damage at all.

I was thinking about opening a new box (lot#) of bullets and try loading 22 of them to shoot at 600 to see if it made a difference.

 

[Scott Harris]

Have you verified the barrel twist rate?

 

[yukonal]

He's been shooting the same barrel for years, without de-stabilization...

 

[Bulletman]

The part about a warm load combined with having problems getting the fired cases out of the gun is suspect if I read him right.

 

[daniel brothers]

has the velocity changed....?

 

[r bose]

Remeasured the throat today, bullet OAL. It hasn't moved much at all. Maybe 10 thou in the last 300 rounds. No noticeable change in velocity ...... 600 yard zero was about right where I've always set my sights.

Warm load yes. To the point where I had trouble opening the bolt, never before.

 

[r bose]

Any other thoughts about bullets tumbling as the barrel wears?????

 

[pacificman]

I had a rifle that shot great and when I bought same powder with different lot number... things changed. Also found throat wear at the same time. I changed to a different powder with a bit slower speed and this rifle shoots good again but not at the same speed. It also sounds like you may have been on the edge of bullet stability all along. You probably don't want to hear all of this but you might want to try a bit lighter bullet and/or powder. Just giving you some thoughts to ponder.

 

[r bose]

First thanks for all the suggestions. I'm not convinced the barrel is worn out but I don't have access to a borescope. Afterall, why isn't every bullet coming in sideways at 600 yards if it is completely worn?? Went back to examine my load. Took some fired lapua cases (from this rifle) and after full length sizing, Hitting the shell holder and slight camming over, I'm bumping the shoulder back about 3 thousands. I fully trimmed, chamfered and used a VLD reamer in the neck giving me 1.749" cases. Here's the issue, with these completely worked over cases, I can close the bolt but get a hard bolt lift to extract the empty, unfired case and a "CLICK" sound from the bolt on the top of the extraction motion. I'm guessing some of my cases have lost their ability to "spring back" into shape???

Any of this make sense to anyone?? Possibly need to anneal "I've never done this" ??

 

[jsthntn247]

Yep, once a case gets the clicks it will never go away. Loads must be on the warm side.

 

[cmillard]

is there still some resistance when you seat your primers? I would back off your charge or try another powder. I would think that you are stressing the bullet jackets a bit. your 6.5 twist is pretty quick--if you ever have a chance to read Laurie Holland's article on the 90 grain bullets, do so. IIRC, he settled on 7.2" twist for 90 grainers in FT/R out to 1200 yards. you might want to give some Lake City brass a try as well and sort by case volume. I have never shot Lapua brass in my .223 (shoot Lapual exclusively in my 6BR) and only shoot LC--as I have had issues with other brass, namely Federal, in my gas guns.

 

[XTR]

The click at the top of the bolt is usually because the base of the bullets has been expanded and the die won't go all the way to the bottom to resize. As for "once it clicks it always clicks", I'm glad that's not the case or I'd have a whole lot of clicky 308 brass. I've FL sized a lot of ammo and gotten rid of the clicks; however, in your case I think only a small base die will fix you clicks.

As for your tumblers, I doubt that it's the brass. You may have damage to a land that is damaging some jackets and not others, who knows. I think a bore scope may be the only way to figure this out.

 

[r bose]

I just seated some BR-4's into the brass and all had good resistance going in. Primer pockets are not blown out at all. Been using R-15 since day one from the same 10 pounds I bought. I'm gonna back off my charge and shoot 3 10 shot groups (3 different charges) tomorrow to see if anything helps. I only have access to 200 yards tomorrow so we'll see.

I'm trying to eliminate any other possible cause of the problem before I pull the barrel. I do not have a borescope to help "SEE" the problem but, I have a new barrel, 7 twist bartlein on the way if all else fails.

 

[XTR]

I just seated some BR-4's into the brass and all had good resistance going in. Primer pockets are not blown out at all. Been using R-15 since day one from the same 10 pounds I bought. I'm gonna back off my charge and shoot 3 10 shot groups (3 different charges) tomorrow to see if anything helps. I only have access to 200 yards tomorrow so we'll see.

I'm trying to eliminate any other possible cause of the problem before I pull the barrel. I do not have a borescope to help "SEE" the problem but, I have a new barrel, 7 twist bartlein on the way if all else fails.

I have a hard time believing that tumbling is caused by your reloading. Loss of accuracy and precision, sure, but tumbling indicates to me a problem with the barrel or the bullets, not what is behind them.

 

[r bose]

XTR, thanks for your comments. I'll add, I've shot 80 sierra's very accurately from this rifle. With those bullets being thicker in the jacket, I'm hoping they will still shoot OK. We'll see, but after exhausting all other possibilities, I think somewhere in the barrel, the 90's thin jacket is getting "skinned" from normal wear, and creating the problem. But, if the 80 sierra's still shoot well, I have enought loaded to shoot a couple more matches.

I've had AR's barrels quit shooting 80-82g bullets but continue to shoot 68-75g mag length stuff for many more rounds.

 

[Turbulent Turtle]

A damaged jacket should not cause a statically stable bullet to tumble; what it would do is induce a dynamic instability issue that would cause the bullet to veer off course or at the very least, enlarge the groups.

My hypothesis is you may have some lands that have eroded and so your bullet is actually not spinning as fast as it used to and so bullets are now on the verge of instability. You would get more of these keyholes in cooler temps and less in warmer temps.

Short of a borescope you should use the cleaning rod with tight patch method and see if there are areas in the barrel where you have more or less resistance pushing the rod through. You should also measure the twist, foot by foot in the barrel.

If you can shoot 80gr bullets with no stability issues, it's definitely somewhere in the barrel.

 

[akajun]

Robert, IIRC you have a good bit of rounds down that barrel. Dan Z used to shoot 90's out of his service gun, said it had signifigantly less life in it that barrells used with 80's and such. Said John Holinger borescoped his barrel and had no rifling for about 1/3 of the way down.
Just pull the barrel and replace it, or have it set back and re crowned.