What should I turn my Lapua 223 necks to?

[jlow]

Getting ready to neck turn this 2x fired brass. Using a Redding case neck gage, I find their average neck thickness to be 13 thousands with some varying down to 12.5 thousands and some up to 13.5 thousands. So the question is what should I turn them to be it 12.5 or 13 thousands ? Please give rationale with your suggestion.

 

[JRS]

What is the neck diameter of your chamber?

 

[jlow]

Don’t know, but it’s a Kreiger min-spec 223 chamber barrel. Finding some fliers with some of the thicker neck stuff so hoping a more consistent neck thickness might help.

 

[JRS]

You would be wise to find out the neck diameter before you start removing brass.

 

[stacy]

+1 FOR JRS YOU GOT TO KNOW WHERE TO START

 

[jlow]

I understand where you are coming from but I am not turning to clear a tight custom chamber but only to normalize neck tension which is a different rationale. FWIW, I can see a consistent 20% higher seating force with the thicker stuff using a K&M seating force gauge thus the desire to normalize this.

 

[tenring]

Measure neck diameter on a fired case. That will give you approx diameter of your chamber at neck. Turn about .001" from either side of the neck and you should be OK. That should give you .002" clearance, which is minimal.

I skim turned necks on twice fired .223 Lapua brass yesterday. They measure .00120 on each side now. In my factory chamber they will have .005" clearance less than a loaded round.

 

[JohnHenry]

As others have mentioned, it is always desireable to know the chamber neck diameter. Assuming a total .001 "spring back", the neck OD of your fired case will be approximately .001 less than you chamber neck diameter. Based on what your have presented, I would turn the necks on a number of cases to neck wall thickness of .0125 and see if that gives you the results you are looking for.

If your chamber neck diameter is also minimum SAAMI, it will be .255. If chamber is a "minimum" no-turn neck diameter for Lapua brass, it is probably a .252 or .253.

 

[jlow]

Again, I don’t think the Kreiger is a tight custom chamber so the idea of 0.002” clearance does not apply. Regardless, I have a call to Kreiger to try to get the specs.

So yea, thinking of skim turning to normalize neck tension. What is the rationale for going down to 0.0012”, perhaps you mean 0.012”? Seems a bit much since my thinnest neck is 0.0125” so even skimming down to this everything would be normalized.

 

[Laurie]

Assuming your chamber is 'minimum SAAMI' or similar, turn the brass as little as possible to get even results. (As JohnHenry says, it's easy to get the chamber dia, value from your fired brass. Measure a selection of cases fired with full-pressure loads and add 0.001" to the dia. of the largest examples.)

With brass that produces readings between 0.0125 and 0.0135", but mostly ~0.0130", you have several options:

a) turn everything to the smallest diameter found. But that means you will run at larger clearances than needed or is desirable with most cases.

b) measure cases at three points around the neck to not only get indidvidual readings, but to identify those with larger than normal variations. (Usually, such wall thickness variations aren't just confined to the neck but run down through the body walls.) Batch those within a 0.0005" on the individual case-neck range and batch again across cases, so you have a collection of cases between say 0.0127" and 0.0133". A lot of work! Use those outside of the chosen range as is for practice, load development, short-range matches.

c) do a batching job plus turning. That is segregate out the very poor examples that are well outside the norms and then turn. Depending what the batching produces and how many cases you start with, that could be to 0.0125" for the thinner examples, and 0.0130" for the fatter ones.

d) weigh turned and otherwise prepped cases and batch again.

There is also an a) minus 1 step - buy good brass. I've used Lapua Match for all my 223 Rem FTR L-R ammo over the years and nothing this (eastern) side of the Atlantic touches it. (Also very strong.) If the brass isn't very good to start with, you simply waste a great deal of time putting effort into substandard cases.

There is also an e) step. Get rid of the 223 and start again with 308 assuming this is for a discipline where it's limited to this pair. 223 Rem can be a fantastic performer, but it's is a LOT of work getting there, and sometimes a lot of heartache! Everything starting with the brass has to be perfect for longer ranges with the little cartridge.

 

[sparky123321]

I hear what your saying. Consistency is the most important thing when it comes to accuracy.

+1 to:

a) turn everything to the smallest diameter found

 

[jlow]

Talked to the tech at Kreiger and he said they cut to SAAMI spec which would be 0.253. So assuming 224 for bullet and either 0.0125”, 0.0127” or 0.013”, clearance would be 0.004”, 0.0036”, or 0.003”.

So going by Laurie’s recommendations, I already brought Lapua brass but even with that, there are variations. What I think I will do is to dial in the neck turner to give 0.0127” and see what percentage comes out with a complete clean neck turn on all surface. If I get enough good ones, will use the ones that have partial as foulers. If not.....

I agree with the 223 vs. the 308 but I am using the 223 to learn so…

 

[Tzed250]

I turned my Lapua .223 brass to a .0125 neck thickness. That took .0005 off of the thickest part of the cases.

 

[Laurie]

What I think I will do is to dial in the neck turner to give 0.0127” and see what percentage comes out with a complete clean neck turn on all surface. [jlow]

Don't worry about cases that have a small amount of untouched neck left - it's a clean-up you're doing here. If worried, remeasure and the chances are those sections will only be marginally thinner than the turned areas. With this kind of turning, you often get a thin untouched band around the case-neck usually just above the neck to shoulder junction.

Good luck with the 223. I say use 308, but still have two match 223s I won't part with, so I'm not really one to quote!

I turned my Lapua .223 brass to a .0125 neck thickness. That took .0005 off of the thickest part of the cases. [Tzed250]

Unlike turning for undersize chambers, the exact value to turn to in no-turn chamber brass preparation depends absolutely on what you find in the production lot. Over recent years I've found Lapua .223R brass lots that mostly ran a little above 0.012" to a full thou' more. Most of my brass currently in use is close to Jlow's example and are therefore turned to somewhere around the 0.0127" mark he's selected. But, it's never a matter of there being a set value to be adopted for every lot of cases.

 

[jlow]

What I think I will do is to dial in the neck turner to give 0.0127” and see what percentage comes out with a complete clean neck turn on all surface. [jlow]

Don't worry about cases that have a small amount of untouched neck left - it's a clean-up you're doing here. If worried, remeasure and the chances are those sections will only be marginally thinner than the turned areas. With this kind of turning, you often get a thin untouched band around the case-neck usually just above the neck to shoulder junction.

Good luck with the 223. I say use 308, but still have two match 223s I won't part with, so I'm not really one to quote!

Thanks! Good advice

 

[jlow]

Just finished turning about 100 pieces of brass and must say that the 0.0127” cut is a very good suggestion! Not one piece got a complete cut with that setting, and most had an average skim of about 80% of the neck surface with variance of +/- 10% more or less. Highs measure in at 0.01275” but the lows were at usually 0.0001” to 0.0002” less. So pretty pleased with the results – thank you Laurie!

 

[Travelor]

If you have not yet done this, try using a 22 caliber nylon brush on the inside the the case necks before loading. Really helps me with neck tension uniformity. Just run it in and back out and it seems to "uniform" the carbon and helps the loading to be much smoother.

 

[LHSmith]

FWIW I only turn necks on unfired brass.......once fired, the brass springback in not uniform.... not even if from the same lot......and doing so yielded inconsistent results for me ...both in measurement and target.

 

[Lazer]

Jlow, I am also working a kreiger 223 right now. Could you please post some picktures of a few 5 shot groups w neck turn and a few 5 shot groups without, all w your best load as I am very interested to see the results.

 

[jlow]

Travelor – yes, it’s good advice but I already do this with the nylon brush.

LHSmith – agreed about the potential problem with work hardenings/springback difference. I own a BenchSource and so I am one of those that anneal after every firing so my hope is that this will overcome this potential problem. My turning has been very consistent so hopefully no problem.

Lazer – Unfortunately no 5 round groups to post as this is a new barrel and I am currently just stated to do a work-up using OCW. You can contact me off line if you want to talk more about this.