Vetrical stringing

[TerryPohl]

Could to light of neck tension cause vetical stringing? I shot a couple of groups with virgin brass that shoot great, but after resizing and shooting the same load with less neck tention I got about 2'' vertical, Every thing else was the same, horizontal was great, shooting at 400 yards over flags. Shooting a 6.5x284 Shehane.
Thanks for any help on this.
Terry Pohl

 

[TonyR]

Terry. I don't think that the exact neck tension as much effect on vertical as long as the neck tension is the same for all rounds in the string. I have accidentally loaded cases with no neck tension and they shot great soft seated as did the same cases with the same load sized with a bushing 0.002 less than the loaded neck diameter.

I have observed differences in the performance of the same load in new cases versus fired cases but it didn't appear related to neck tension. In the extreme, it takes almost 1.5 more grains of powder for the velocity from a fired case to equal the velocity of a fireforming case with my 284 Shehane. This difference is enough to move the velocity out of the node with that gun. I guess it would depend on how much bigger you chamber is than the virgin brass; but it might be something to consider.

 

[TerryPohl]

Thanks Tony, the neck tenchion was all the same as far as I could tell by feel. I will shoot a group of vergin brass and some once fired through my crono and check the difference.
Terry Pohl

 

[BulletShooter]

Terry,
I have had two rifles that did have the vertical string, two 338 . I think it all has to do with barrel harmonics.
One 338 win was on a Thompson, 29 inch barrel 226 gr bullets with a brake. The forend came lose it was held together with screws one screw came out. I was getting 11 o'clock strings that were 4 inch's at 100 yards , once I found the problem the string closed up, to a nice group.
The other was a 338 rem ultra with a brake 1-9 twist as long as I shot 245 grain bullets they shot very well no string's .
But soon as I went to shooting 300 gr bullets they were making a string at 100 about 4-5 inch's. What I had on that rifle is a complete free floating barrel, The action was glassed bedded all ready. I glass bedded one inch in front of the barrel lug and the groups came in and it made no differences with the 245 grain bullets

 

[Raptor]

I don't know if this will be the same with yours but I had a 260 and it would string the rounds vertically and I asked the same question and one of the replys was to change the seating deapth so I did and it quit.

All my other 260s seemed to like some jump but this one would only shoot with the bullet at the lands. If I backed it off I got some vertical stringing. You might give it a try if you haven't already.

 

[Heavies]

+1 on the other suggestion.

I'm thinking you have to tweak the load a little due to more volume in the FF'ed cases.

 

[BoydAllen]

Neck tension, brass fit to a chamber, seating depth, and powder charge, are all tuning variables. I would say that if you are getting good groups when fire forming new brass, then you have your load for that set of conditions. Having a fire formed case, and neck tension has put you out of tune with that seating depth and/or powder charge. Take your reloading to the range, and spend some time tweaking the load. It should come back.

 

[bugsplat]

Yes, you will need to find a new charge weight and seating depth. I never group with new brass. Always fire-form it first and run it through the reloading dies you will be using for the life of that barrel. From here you can develop a load. 99% of shooters cant tell the difference between them but for the elite group who call 1 MOA "too big" every little thing makes a difference. Its all about consistency.