I want consistent neck tension

[skankpile]

I’ve got a load of cases that have been “bubba-annealed” by my trusty propane torch and hot fingers about 4-5 firings ago, and they have never been neck-turned.

Thanks to billmo, I’ve finally found my correct charge, and OAL.. and me thinks I have a cartridge that should be performing much better than it is.

Here is my catch.. the last rounds that shot really well I pulled from previously loaded cartridges and when I reset new bullets for a different OAL the tension was near perfect between then.. AND THEY SHOT GREAT!!... Now that same load in a other brass is performing sup-par.. I’m thinking its got to be the neck tension.

What should I be doing.. turning necks, or is the Ken Light annealing machine the clincher to get me the best neck tension? I foresee another $500 flying out the door in this never-ending quest . I’m also finding that when I seat bullets the depth/OAL is varying because of the tension… is this the culprit of work-hardened brass?

here is what I'm thinking:
1) buy box of fresh laupa brass
2) neck turn them
3) put them through a ken light annealer

If I've done this will my seating, and sizing pulls be right-on consistent?

 

[nonliberal]

The first thing I would do is buy a fresh box of Lapua, run them up an expandron mandrel, turn the necks so it at least cleans them up all the way around, then fireform and resize with a good die. Thats going to tell you if it was your brass causing the problem. It wont be a waste of money since you will use the brass one of these days anyway and it probably wont get any cheaper.

PS. Take a look inside the flash hole of the new case, lately I have been finding brass flakes blocking part of the hole. I use a K&M uniformer to clean it up.

 

[Forum Boss]

PS. Take a look inside the flash hole of the new case, lately I have been finding brass flakes blocking part of the hole. I use a K&M uniformer to clean it up.

This is an important observation. We've seen the same thing. One thing to note, however, with the small flash hole Lapua brass: the flash hole is spec'd to be 1.5mm, or .059. Most flash hole tools, including the K&M are supposed to ream the hole to .0625. However, we've found variance in the tool cutter tip diameters so they can enlarge the hole to as much as .067. An inexpensive pin vise can be used to knock out the brass flakes without enlarging the hole.

 

[nonliberal]

Good tip!! I was using the one for ppc but your way looks to simple to pass up. Thanks.

 

[rstreich]

There are a lot of things that could be contributing to the different results. Is this other batch of brass the same manufacturer and lot? Was it sized with the same bushing/die? Etc. The question to ask is: What things were different between them?

nonliberal made some good suggestions. Sometimes it's good to just start from scratch. It can save a lot of headaches. The Moderator has a good tip also.,I think I disagree with his base premise that you shouldn't enlarge Lapua flash holes. I've seen some significant variations on flash hole sizes in some lots of brass, as well as the annoying flakes. I just don't have any test results to argue one way or the other.)

One point, however, is that you should not re-anneal new Lapua brass, or any other for that matter. New brass is already annealed.

 

[CPorter]

It could be that the brass went through different guns and was worked differently. A loose neck work hardens the brass faster than a tight neck sized to the same dimension. If it has all been annealed though... I've used a version of bubba anneal for years and have had good results. An annealing machine would be nice but I can't justify the cost yet. You can double anneal the brass, let it cool and redo the process to reduce variations. Brass strength will only go down so far with proper annealling.

Seating depth variations could be caused by seating the bullets into a donut in the neck. Are the necks the same thickness? .001" difference in brass thickness should cause a significant change in clamping force.

I have also found burrs and rings around the primer flash hole. Burrs in the brass that manufacturers use a punch to form the hole, rings in Lapua where it looks the the drill bit got dull and was pushed through instead of cutting.


New brass has it's advantages.