Vertical stringing and hot barrel

[Viperdoc]

Working up some loads for my new Krieger barrelled AR using Varget and SMK 69's. Have had less that 0.25 horizontal groups, but around 1 inch vertical stringing. I was thinking this wad due to inaccuracies of the powder measure (redding BR), but a guy at the range said it was because the barrel was too hot. To me, the barrel was warm, but I could easily hold my hand on it without difficulty. Is this too hot, or could it be my reloads?(new Lapua brass, CCI primers, SMK 69s at 2.26O OAL) Barrel has around 300 rounds through it, cleaned according to Krieger break-in recommendations.

 

[Gearheadpyro]

If it is a thin barrel then getting it warm/hot could cause stringing. I would more likely go with powder charge, either that or incosistent seating depths. Try this, load a few clips with perfect ammo, measure and mic everything. Shoot it like normal. If it strings blame the barrel. If it doesn't then load up with some of your normal ammo and shoot very slowly and carefully. If it strings, tweak your loads.

 

[msnations]

That doesn't sound like a terribly hot barrel - but it might not take much; I don't have much experience with barrels that walk...

I find it hard to believe that its (only) your powder measure - a spread like that would take a powder charge spread in excess of 2 grains. I know from experience that varget doesn't like to meter well, but the worst I've encountered is a +-.2 spread (Dillon Precision progressive measure)

Make sure you're rests are in order and you're scope is alright (ring alignment and fit can be problematic on ARs)

 

[hershey]

fine tune your load or seating depth, your usually almost done when you get that condition. i'd try another couple tenths hotter.

 

[habu]

FWIW and SOMETHING TO PONDER.

you set your sights to shoot center X! your apply X amount of BODY TENSION behind the stock in the process.

IF, during firing, you have LESS than X amount of tension behind the stock, the weapon WILL RECOIL MORE and the muzzle WILL CLIMB MORE.

conversely, IF you have MORE than X tension behind the stock, the weapon WILL RECOIL LESS and the muzzle WILL CLIMB LESS.

WALA - vertical strining!

ron

OH, and than we get into bullet vel. when encountering the above! but that's for another day.

 

[jlmurphy]

I had exactly the same experience with a Krieger barrel. I used one of their barrels and our complete machine shop to make a heavy barrel ( 1") Mini 14. It shot 1/2" groups, but would string 3" vertically when warm. I tried everything, with no luck. I finally mounted the barreled action to a surface plate with a dial indicator on the muzzle. When hot water was poured through the bore, the muzzle would move .018", every time, from an 18" barrel, that extrapolates to 3" at 100 yards.
I researched Krieger, and found that they do not stress relieve their barrels like Shilen, Hart, or Douglas after rifling. I asked for a replacement barrel, received no reply. I stress relieved the barrel in our electric furnace, but it was never the same, although the vertical movement was gone, I think the bore dimensions changed. I sent the barrel to Krieger, they sent it back, said it looked good to them. I replaced the barrel with a Shilen, shoots great.
With Krieger barrels it is a crap shoot, you may get a hummer , you may get an expensive headache, either way, you are on your own.

 

[Viperdoc]

The barrel is a 26 heavy Varmatch Krieger, and when I shot it and noticed the stringing, it was warm, but I easily could hold my hand around it. Seems like Varget worked better than AA2520 in terms of group size. When shot cold, the groups weren't that tight, but thought it was my hold technique off of the rest. As I tightened my hold, the groups got better, but then noticed the vertical stringing. All of the loads were either metered +/- 0.1 or so grains, or weighed individually. Even though the Varget didn't meter that well compared to 2520, the Varget groups seemed to be better.

Really don't know what to address next- my hold technique or something else. Reloads are all new Lapua brass, CCI primers, and Sierra MK 69gr, all at the same OAL of 2.26 trying to minimize variable. Should be seeing less than 0.5in or better, but I'm still not getting less than 1" for five shot groups. What about trying some factory match ammo to see if it's my reloads?

Any ideas appreciated.

 

[jo191145]

Don't know diddly about AR's.

I would check to make sure your neck tension is sufficient. Bullets could be getting jammed deeper in the case in the magazine or during cycling. They could also be getting thrown forward by the slamming of the bolt. Saw that happen at the range to a guy with an AR-10. Gun shot fine loaded one at a time. Running through the mag the bullets got thrown into the lands by the bolt.

May want to try a different primer. I have a lot of CCI BR2 LR that vertically string every darn thing I try.
Just an idea.

 

[Obtunded]

I researched Krieger, and found that they do not stress relieve their barrels like Shilen, Hart, or Douglas after rifling. With Krieger barrels it is a crap shoot, you may get a hummer , you may get an expensive headache, either way, you are on your own.

Apparently you didn't research very well.

Krieger barrels cryo treats is bar stock. This not only stress relieves, it makes them resist sliding wear. Furthermore, they are multi-pass cut rifled, which does not produce latent stresses. In other words, stress relieving is simply not required with their cut rifled barrels.

Shilen, Hart, and Douglas are all buttoned rifled. These MUST be stress relieved, as they drive a carbide plug down the bore with tens of thousands of pounds of force to shove material out of the way to produce the rifling. This stresses the hell out of the steel. The barrels that get bent too far out of spec in the process get sold as lower grade barrels, the ones that stay straight enough are sold as the higher grades.

Baking them does relieve most stress but not all. If you research a few of the buttoned rifle manufacturers out there (that stress relive their barrels) , they will void the warranty if you flute the barrels as it is a mechanical form of stress relieving.

It is pure coincidence if the string bends perfectly straight up on a barrel that warps with heat, as it could warp in any direction. I would blame the barrel if it went 45 degrees in one direction, but straight-up/down? Hmmm. I'm more convinced it is user input.

 

[habu]

i was wondering when someone would bring up the 'facts' about krieger bbl's as was done in the above post.

i still believe that the 'loose' nut behind the stock is what causes abunch of the 'vertical' stringing.

but. what do i know.

ron

 

[jlmurphy]

Obtunded,

You'll notice there are no more advertisements for Cryo treatment of barrels in any precision shooting magazines. Cryo treatment is insufficient to relieve 416 stainless steel, which must be heated to the 1400 degree range to relieve internal stress, which I did, and it did eliminate the movement of the barrel when warm. You are right that barrel warpage could be in any random direction, mine was up, which I duplicated on a surface plate with a precision dial indicator, hardly user input. You pointed out that button rifling induces stress, I agree, you pointed out that removing material can induces stress, I agree, but by the same logic boring, reaming, cut rifling, and profiling done by Krieger must also induce stress. If Krieger's cryo stress relieving was sufficient, then why are there stories ( mine included) of their barrels stringing when hot? I have used match grade barrels from Shilen, Hart, Douglas, Lilja, and Krieger. Kriegers were the only ones that walked.
Viperdoc's experience was exactly the same as mine, I went through every other possible explanation, it was the barrel. I was hoping to save him the trouble. By the way, I have been building rifles for 15 years and own a machinery fabrication business.

 

[Viperdoc]

I admit to being a rookie, so I am also able to admit that there might be something with my shooting technique that results in vertical stringing. However, also trying to eliminate all other variables to try to get the best results. Seems like choice of barrels is like Ford versus Chevy- it comes down to personal preference. However, I had the chance to meet the guys behind the phones when I picked up my barrel at Krieger- they were genuinely interested in helping me learn and do better. I'm still trying to sort out whether it's my reloads or my shooting technique- I will leave the barrel to one of the very last items on the list.

 

[jo191145]

Viper

Well have you tried factory or other handloads? You state you have 300rds down the tube.
Does everything string vertically or just your latest loads?

The old rule of thumb is as Hershey stated. Vertical stringing, load hotter and seat closer to the lands. You may be hampered seating longer due to mag length.

Checking your barrel should be easy enough. Cold barrel fire two foulers and a five shot group rather quickly. Check for vertical. If no vertical just keep going and see if it starts throwing rds.
If vertical does come back after the tube is warm let it cool entirely and try again.

Have you tried loading the rds singly without the mag? IMO rounds not properly constructed can get pretty beat up being fully cycled.

I'm not a metallurgist but Kreigers sure have a good name and plenty of trophys under thier belt. That said I do have only one Kreiger barrel in 308 Win. Oddly enough it does act a little funny. Usually puts four or five in one hole at 200yds then begins opening up. I've always blamed my reloads and my ability to get them tweaked just right.
I hope jlmurphy is wrong on his assertions :-\

Viper. Largest case of vertical I've ever seen was at a local range. Father and young son were trying to get a deer rifle sighted in. They had an old, possibly homemade, one piece rest. The front part was a piece of steel rod with tape on it. Not a sandbag.

At 100yds the sons groups were 18'' lower than the fathers, and much better. The Dad was getting a little angry trying to figure out why.

I wandered over and watched both shoot. The young boy was setting the forearm on the rest. The father was setting that thin sporter barrel on the rest. ;D ;D

Was pretty funny. Just one more don't ever do this story

 

[Obtunded]

Obtunded,

.... but by the same logic boring, reaming, cut rifling, and profiling done by Krieger must also induce stress. If Krieger's cryo stress relieving was sufficient, then why are there stories ( mine included) of their barrels stringing when hot? I have used match grade barrels from Shilen, Hart, Douglas, Lilja, and Krieger. Kriegers were the only ones that walked.
Viperdoc's experience was exactly the same as mine, I went through every other possible explanation, it was the barrel. I was hoping to save him the trouble. By the way, I have been building rifles for 15 years and own a machinery fabrication business.

I recognize a lost cause when I see one Nothing that I or anyone else can say will sway your opinion of Krieger, so as long as you are happy with button rifled barrels, keep building and shooting. In the last few years I've never been beaten by anything other than another Krieger, so the more people using something else, the happier I am anyway.