Neck tension issue? - 1,000 yard F/TR

[Tempest]

I think I have a sporadic neck tension issue and would love some input.

Last season on 2 different occasions at 1,000 yard F/TR match, shot would be in the 10 ring and next shot an 8. In one match it was a 7 after a 10. Chalked it up to a missed wind change. Looking back at it, both were high shots.

At the range, I typically chrono some loads and then shoot. So yesterday did a string of 20+ rounds just like a match at 1,000 yards. 1st 5 or so rounds were great, FPS around 2990, ES under 10. Around shot 11 or 12, shot was high and was 3013 FPS. Kept shooting and was normal again. Then later a 3013, few later a 3019 again. So the overall ES from high to low was 50, where in testing earlier in the year I was seeing under 10 with new brass.

So looking at the math for the drop vs. the high to low and avg velocities, looks like that was likely the problem. It would have turned a 10 into a 8 or 7.

Also interesting that if I took out the high rounds, the rounds were very consistent. As such, I'm pretty certain it's not powder weight or bullet weight. I’m very anal about powder weighing. So I’m thinking this is a neck tension issue. The last part of the season I started annealing the cases as they had 5 or more loads on them. So I have a problem with annealing, did not heat enough or something? I was using the drill and torch method. I’m pretty methodical and was not convinced at the time this was a very specific method of annealing?

Looking back at last season, I find that the best score of the year was using new brass. As the components have bearing on this, here is what I’m using:

Lapua large primer brass
Lapua 155 Scenar (used to weigh them but did not appear it was needed)
45.5g Varget
CCI 200 primers

The annealing is the only change/variable since having much better results earlier in the year. Am I on the right track this is a problem with neck tension and possible annealing issue/method?

 

[dkhunt14]

When brass is new it shoots as good as it gets. People think they can't fireform and shoot accurately. Some of the best BR groups at 1000 have been fireforming. Especially if you are shooting the bullets in the rifling. When it is new it is soft and consistent. Annealing if you get it right will help a lot especially with high and low shots. It is not all about the bullet tension either. Annealing helps the chamber seal off. Matt

 

[Turbulent Turtle]

It just sounds to me like you're not annealing consistently from case to case. Also, annealing after 5 loads is a very long time; I anneal after every firing using a Giraud. The cases look all the same and then I F/L size them and the coloring diminishes. But they are all the same.

So, in your story, it's as if the 3 cases with the high MV were not annealed properly and never reached the proper temperature and retained the tension generated over 5 loadings. That's a big step.

 

[Dos XX]

Have you measured loaded neck diameter to see how much neck clearance you have? If you have the cases identified that shot high, see if you can tell a difference in neck thickness / loaded round diameter.

I anneal more often than 5 firings as well.

 

[jlow]

I would also guess it is an annealing problem although if you don’t weight sort your brass or neck turn them, those could also compound your problem.

The problem with the drill and torch approach is you have to keep so many things under control at the same time. This includes the distance between the flame and the brass, how fast you are turning the brass, the exact spot you are aiming at, and of course the duration of the anneal. All of these are under controlled with an automated annealer but all of them are under your control if you use the drill and torch approach. I personally are pretty good with my hands but would never tell you I could achieve consistency using that method. I think it is a perfectly good approach if you are annealing to soften the brass to prevent splits, but to achieve consistent annealing no.

I was going to ask you to measure case neck OD after case prep but if you don’t weight sort and neck turn, that won’t tell you anything i.e. it will be different. Another way you can check is to use the seating force machine put out by K&M to measure your product as you seat your bullets. That is the more precise way to do it but frankly if you have a neck tension problem, it should be pretty obvious when you seat your bullets as the seating force will be significantly different between rounds.

 

[mysticplayer]

Consider checking - neck thickness. Brass flows and necks thicken irregularly. I now outside neck turn EVERY firing and alot of tuning issues have been resolved. If you use bushing neck dies to size the neck, outside neck turn every firing

I have also found thinner necks work better for me.

Annealing by hand or simple annealers - been there, never consistent. I now use a Bench Source annealer. anneal every 2 to 3 firings. It is not just peak temp but also duration at desired temp (dwell). There is simply no way to be consistent by hand. Lapua has a hard alloy and the annealing cycle will be very different then say with Win.

how accurate is your scale? If you have precise methods of weighing but the scale has error, all efforts are wasted. You can definitely create tuning issues with as little as 0.1gr variation in your loads.

Have you confirmed that the case volumes are the same? Don't weigh them, measure them.

Did you tune your loads at 1000yds with small accurate powder charges or did you just depend on the chronie while testing at short? My guess is that you are around 0.2gr off ideal.

Did you ever try using another match primer or even different brand? Irratic ignition leads to irratic vertical at distance.

Did you readjust your loads when your barrel went beyond 500rds of fire?

Did you do all testing from a fouled bore or from a clean?

Does the speed change occur on a consistent basis?

Did you put powder charges in all the cases before seating the bullets?

The many small steps I have reviewed for my own stuff..... Gets pretty anal but I have found several small errors in my process and it has helped my ammo shoot better.

Jerry

 

[bozo699]

Tempest,
From 600 yards on out things get really critical,...I think your on the right track in your thinking, buy yourself a good annealer to start with and I assume your seating with a arbor press if not get one, I prefer the K&M Arbor Press with Force Measurement, so I can see what is happening but any arbor press will work and take mental note on seating pressure and if one is light or heavy mark it and use as fowler or warm up rounds. After I started doing this my 1000 yard groups were considerably reduced also I agree with others,......anneal after each firing, keep cases separated so there are the same firings on each case from the same lots, you should see those 7 & 8's go back to 10's best of luck to ya sir
Wayne.

 

[CatShooter]

The problem with the drill and torch approach is you have to keep so many things under control at the same time. This includes the distance between the flame and the brass, how fast you are turning the brass, the exact spot you are aiming at, and of course the duration of the anneal. All of these are under controlled with an automated annealer but all of them are under your control if you use the drill and torch approach. I personally are pretty good with my hands but would never tell you I could achieve consistency using that method. I think it is a perfectly good approach if you are annealing to soften the brass to prevent splits, but to achieve consistent annealing no.

"This includes the distance between the flame and the brass..."

"how fast you are turning the brass"

"and of course the duration of the anneal."


I have no problems using a tourch and drill to anneal - the variables are east to control - it is easy to place the case in the same place of the flame - put the neck of the case at the tip of the flame...

"... how fast you are turning the brass"... is controlled by the drill - it turns at the same speed.

"and of course the duration of the anneal"... is controlled by... ta ta... counting seconds.

I use a Ames hardness tester (FAA Certified), and there is no more variation with this method, than with a machine.

Counting is far better than judging by colors - these two sets of case were done the same, and had the same neck softness, but look completely different - same make (Rem) but different lots made several years apart.

.

 

[Tempest]

Thanks for all the feedback.

To add, yes I sort by case weight. Only cases that are all the same for 20 shots are used. If they are different, they are used for next relay etc.

I do check for concentricity and it's typically .001" or less.

No I have not been neck turning. I've been looking into a K&M that I can use on my lathe. Looks like I need to focus on my annealing and start neck turning.

 

[jlow]

Yes, some people ;D will swear to you that they can do just as good a job using the drill and socket approach. To that, I will only swear to you that I can't! 8) Thus the advice.

 

[savagedasher]

I shoot very little neck tension at all distance. I also shoot a bullet that likes be jumped more then .020. Neck tension is required when you don't jump the bullet.
I don't work my brass more then.002 except for.120 of the neck. When I size my brass I just can push a bullet in and pullet it out with my fingers. My throat is long enough to where the boat tail is forward of where any donut the case mite get. I use two different dies when sizing .
The bushing size depends on how many times the brass has ben fired. What ever size it takes to give me 25 to 30 oz of seating tension . Larry