Neck tension - searching for flyer causes

[RustyRick]

When a 5 shot group has 4 under .5 min and one wanders an inch away. Shooting at 100 yrds with a 24 X scope, sand bagged, 1.5 lb trigger.

After all else fails - examining neck tension. Neck sizing.

Thinking of bushing dies, outer case trimming. But that doesn't compute with me.

1. I was taught that its the expander plug that sets the final neck diameter.

So why don't I hear discussion on expander plugs when ? And the chamber limits how much expansion the case can go to.

 

[drbill]

I have had success stopping flyers by measuring the bearing surface of each bullet and sorting them. I consider and evaluate other reasons for flyers as well.

 

[RustyRick]

I check concentricity and have that pretty well in hand. Using match primers, very accurate scale......
Heading for range we'll see what happens to day. They all seated with very similar leverage.

 

[BountyHunter]

mark the case and see if it repeats.

 

[Rich Coyle]

How much runout do you accept?

 

[RustyRick]

Good idea BH. I'll try to keep track of that. Run out? I don't know but if she'll shoot < .5 for 4 shoots. There must be a fix for 1 at 1.5? I don't think it's the nut behind the wheel. With 24X I can see how much movement I have.

One of my questions still remain - If the expander plug is the last influencer on the neck diameter, something tells me it's critical to neck tension.

 

[RustyRick]

I have had success stopping flyers by measuring the bearing surface of each bullet and sorting them. I consider and evaluate other reasons for flyers as well.

Are you measuring diameter at the OGIVE, or closer to the base?

 

[drbill]

I use the JB Bullet Ogive Comparator and stand to measure the bearing surface of each bullet. Each caliber has its own set of bushings.

Mark King Rifles

You can get a similar stand from Grizzly.com.

https://www.grizzly.com/products/Granite-Comparator-Stand-Frame/G9628

Harbor Freight has digital indicators and with coupons get them cheaper.

1" SAE/Metric Digital Indicator

One would still need to buy the bushings from Mark King.

jb bullet comparator - Google Search

Some people measure bearing surface this way.

jb bullet comparator - Google Search

 

[LoneTraveler]

Are you shooting through a chronograph? I have traced many fliers to inconstant primers. Many times a the velocity will change enough to make it drop out of the group. Good Luck in finding the cause and remedy.

 

[918v]

You're probably on the verge of a scatter node. Change your charge weight or OAL or both.

 

[rcoody]

You're probably on the verge of a scatter node. Change your charge weight or OAL or both.

Eliminate the variables one at a time to find the cause.

A lot of people want to ignore flyers but they are representative of what the real group is. Try a 20 shot group and see if the flyers are an anomaly or are really representative of the actual group.

You should be able to find a powder charge that has consistent POI for at least 0.3 gr. Find that accurate load and then check above and below in 0.1gr increments. You would be surprised what a tenth of a grain can do to a group

neck tension is very important. I recommend only neck sizing. I use the lee collet neck sizer because I don't like donuts. I neck size rotate the case and neck size again. Have really good luck with runout

I only use CCI benchrest primers, I weigh my powder charges to 0.02 gr., when I am seating bullets if one doesn't feel quite right it goes in the cull pile, after loading I check all finished rounds for runout. If it is more than 0.002 then it goes in the cull pile.