Lapua 6BR Spring Back?

T

Twud

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I just starting to work with a box of new Lapua 6BR brass for a rifle I have on order. The gun is being chambered with a .265 neck and the Lapua brass has a .268 neck. I have a Sinclair neck turner and the cases won't fit over the turning mandrel. I am not real impressed with the run out on these new cases anyway so I decided to run them over a Sinclair expanding mandrel. The cases go into the mandrel at .268 and come out of the mandrel at .268, and still won't go over the turning mandrel. The expanding mandrel is .242 and is marked E24. Could there be that much spring back in the Lapua Brass?
When the mouth first meets the mandrel there is a bit of resistance, maybe the first 1/3rd of the neck, and then goes the rest of the way by the weight of the press handle.
What am I doing wrong? It's as if the necks don't have the same inside diameter from top to bottom.
I know I'm missing something I just dont know what it is
Mark
 
Re-think this a little....

Forgive me as I take this back to basics but I think that might be where you went astray. Your numbers don't make sense to me. If I am wrong I apologize now.

You might be missing the part about how to measure neck diameter. I suspect that your 6 BR brass is not .268 with a bullet seated I think you are measuring the empty case across the neck to come up with this number. That is not what you want to measure.

You can use one of two methods to measure your loaded cartridge necks:

1) Seat a bullet (the bullet you intend to shoot) and measure the diameter of the neck of that loaded round.

or

2) Use a tubing micrometer to measure the neck wall thickness. Multiply this number by 2 and add the result to the diameter of your chosen bullet. The result is the outside diameter just as you measured in step 1 above.

In either case you want to remove enough brass when turning to make your loaded round neck diameter about .002 smaller than your rifles neck diameter. For your .265 neck chamber you'd want the loaded round to measure about .243.

The difference between your cartridge neck diameter and the chamber neck diameter is the "neck clearance" In this case that is .002 total or .001 per side. This number is not gospel but you do have to have enough clearance to keep things from crimping up.

After you expand the necks prior to turning (I assume you have an expander purpose made for use with a turning tool not just the standard reloading die expander which is too small for this job) the case should be a gentle wringing fit. When you hold the case in your case holder you should be able to twist it on normal with hand pressure. Meaning that you could turn 20 or more without needing rest or band-aids for you blisters. If you have to struggle, its too tight. If it falls on the mandrel its too loose.
 
Henrya

You might want to check your numbers also.

"For your .265 neck chamber you'd want the loaded round to measure about .243."

This should be .263. Don
 
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With a bullet loaded the neck diameter goes up to .269, or .001 grip. I know I have to turn necks, but this is going to be difficult when the case won't fit over the Sinclair turning mandrel and can't be open up with a Sinclair expander mandrel.
 
I use the Sinclair expanding mandrel and turn the necks on the Hart neck turning tool. The mandrel opens the necks up to .2405"-.241" ish and they fit the Hart tool perfect. I also use the Imperial Case Sizing Wax on all of these operations.
 
How loose or tight a fit on the turner mandrel are you after ??

I expand 220 Russian on a Sinclair expander and then use the Sinclair turner and the fit is good. They don't just slip on effortlessly but they are not supposed to.

Try turning the case under power and using some good lube on the mandrel and I bet the case slips on no problem.

If a bullet seated measures 0.269 and no bullet measures 0.268 then the 0.241 turning mandrel should slip in the case neck. Unless you have an incorrect turning mandrel. My Sinclair expander is 0.242 and the turning mandrel is 0.241. That difference works out pretty well spot on for the correct fit of neck on the turning mandrel.

Bryce
 
Thanks Don, that needed correction. I'd change my original post but I don't think I can now. I should have written:

"For your .265 neck chamber you'd want the loaded round to measure about .263."

I think Sinclair has oversize expanders for this purpose. If you can't get it on the turning mandrel now, an expander that is slightly larger than the one you have now should fix it.
 
6BR neck tension

Sorry to hear you are having problems. I am currently prepping Lapua 6mmBR brass and noticed that when I expanded the necks on the brass I wasn't met with any resistance. However, my Sinclair turning mandrel meaures .241 not .242 as you mentioned. Do you have any brass build up on your turning mandrel? I generally take off the brass build on the mandrel every 100 rounds or so with a scotch brite pad. The brass is turning out very good, but I did have a higher percentage cull rate over previous batches of Lapua brass.

Billy Campbell
 
Wildbill1 said:
Sorry to hear you are having problems. I am currently prepping Lapua 6mmBR brass and noticed that when I expanded the necks on the brass I wasn't met with any resistance. However, my Sinclair turning mandrel meaures .241 not .242 as you mentioned. Do you have any brass build up on your turning mandrel? I generally take off the brass build on the mandrel every 100 rounds or so with a scotch brite pad. The brass is turning out very good, but I did have a higher percentage cull rate over previous batches of Lapua brass.

Billy Campbell
Click to expand...

Billy,
What standard are you using for culling purposes? Weight, neck thickness, run out. With t he price of this brass there shouldn't be any.
Mark
 
I weigh all of my cases before I start prepping. Any piece of brass that is not withing 1% of the average gets set aside and used for practice, die set-up, etc. I will weigh about 20 pieces of brass out of each box of 100 and then figure the average.

This particular batch of brass from Lapua had about a 3% cull rate. My past experiences with Lapua brass have been just what you had mentioned, 0% cull rate. I ordered 1500 pieces of the .223 Lapua made, Dakota head stamp brass at a very good price last year. When I received the brass I weighed every single case. I did not have 1 case that was not within .2 of a grain of the average weight. That brass was truly remarkable.

I do like Lapua brass because it will absoluetly last forever.

Billy
 
I weigh all of my cases before I start prepping. Any piece of brass that is not withing 1% of the average gets set aside and used for practice, die set-up, etc. I will weigh about 20 pieces of brass out of each box of 100 and then figure the average.

This particular batch of brass from Lapua had about a 3% cull rate. My past experiences with Lapua brass have been just what you had mentioned, 0% cull rate. I ordered 1500 pieces of the .223 Lapua made, Dakota head stamp brass at a very good price last year. When I received the brass I weighed every single case. I did not have 1 case that was not within .2 of a grain of the average weight. That brass was truly remarkable.

I do like Lapua brass because it will absoluetly last forever.

Billy
 
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