Neck turn - before or after 1st firing?

[Martin52]

A question for those who turn necks - is there a benefit in firing first then turning, or just turn straight out of the box after resizing, trimming etc ?

Martin

 

[Erik Cortina]

Most of us that turn necks have tight neck chambers so we can not chamber a piece of brass that has not been turned, so we turn first. However, I do not see a benefit in turning after first firing.
Do it from the get go and get it over with.

 

[Martin52]

I used to do just that, turn out of the box and get it over with ...but recently have been experimenting with fire first then turn. Chamber neck is 0.340 so I can use new brass without turning. Might go back to the old way !

Martin

 

[Tim Singleton]

I would full length size the new brass. Then run up on the appropriate size expander mandrel that matches the cutter mandrel then turn the necks to what ever thickness you prefer.
Size again either in full die or in a neck die with your choice of bushing

 

[jcampbellsmith]

Good question. I don't run any tight necks, so for new brass, I just run a mandrel through it, then load it and shoot it. I will then consider neck turning after the first firing.

My desire to neck turn has waxed and waned. It's waxing at the minute.

Regards

JCS

 

[Martin52]

One advantage when turning after the first firing is that all cases are likely to be longer than my trim length, 2.005" and I can also get consistent cartridge headspace after full length sizing.

New out of the box I get a few sub 2.005" and a few longer, also cases ranging from 1.628 to 1.630.

Martin.

 

[Raythemanroe]

Your not really turning if you can load them without turning. You should be just skimming to even up the brass. If you take to much brass out you will be over working it and may not get a good seal..



Ray

 

[Martin52]

Your not really turning if you can load them without turning. You should be just skimming to even up the brass. If you take to much brass out you will be over working it and may not get a good seal..



Ray

I can load without turning but this leaves me with irregular case necks and case neck clearance of about 0.002 (chamber neck 0.340, loaded round 0.338) which I thought was a bit tight.

New Lapua brass neck thickness is around 0.0150 but irregular and I turn down to 0.0140 at which point the thickness is pretty consistent. This gives me a loaded round of 0.336 at the neck and 0.004 neck clearance with a 0.340 neck. How much clearance do you reckon is needed for a good seal whilst still safe ?

Martin

 

[Raythemanroe]

If you don't have a tight neck chamber, then you want to just take the minimum to clean the brass up. The more you move the brass when you fire it, the more you will need to move it when you size it and I would assume be robbing brass life.. With your numbers I don't think you would have any issues..


Ray

 

[Joe R]

Martin in Aus. said:
A question for those who turn necks - is there a benefit in firing first then turning, or just turn straight out of the box after resizing, trimming etc ?

Martin

Hi Martin,
You're going to get different answers from people that have different calibers, chambers and tools. As Erik Cortina pointed out some have shave necks just to chamber their rounds. I have to first fire form the Lapua brass because the shoulder is a bit too low and both my Gracey neck shaver and Giraud trimmer use the case shoulder as the stop point, so if I turn necks first and trim I'm going to end up with a short case.

 

[mikecr]

I agree with Erik and Ray
I turn them right out of the box & up onto shoulders a bit to reduce donut area thickness.

I can think of no advantage to sizing or firing before turning, but I can think of disadvantages.
For one, turning mandrel fit.
New necks need only expander mandrel sizing and springback to proper fit. Once you've fired the neck, you're gonna have to restore that fit beyond the turning system design.

Also every cartridge I fireform shortens in trim length, as the shoulders slightly increase in angle to pull necks back. Never seen trim length grow on firing itself, but trim length will grow with FL sizing after firing.
Firing also moves neck-shoulder junction forward a bit(loss of neck length). If you hadn't turned before this, you missed the opportunity to mitigate some future donut thickness that will migrate with body sizing over time.

It really is best to keep turning simple.

 

[Raythemanroe]

Solid point Mike, Turning before fire forming will push the turned area into the shoulder area a bit and fight that donut..



Ray

 

[Martin52]

I'll be using a Giraud tri-way trimmer soon (when it arrives in the mail) and note, as Joe says, it indexes off the shoulder. This consideration seems to support turning after the first firing, but at the risk of the doughnut, for which turning unfired new brass is preferred !

Just on Ray's point about shaving and not taking off too much brass, I remove 0.001 (from 0.0150 to 0.0140), a few cases will have some of the original brass surface but most will be "cleaned" all the way round. This is the minimum amount of turning I do to get consistency in the case neck thickness. So, not a light turn but probably not taking off too much either.

I agree - case length grows after FLS, not so much after firing.

Martin

 

[Erik Cortina]

I'll be using a Giraud tri-way trimmer soon (when it arrives in the mail) and note, as Joe says, it indexes off the shoulder. This consideration seems to support turning after the first firing, but at the risk of the doughnut, for which turning unfired new brass is preferred !

Just on Ray's point about shaving and not taking off too much brass, I remove 0.001 (from 0.0150 to 0.0140), a few cases will have some of the original brass surface but most will be "cleaned" all the way round. This is the minimum amount of turning I do to get consistency in the case neck thickness. So, not a light turn but probably not taking off too much either.

I agree - case length grows after FLS, not so much after firing.

Martin

Trim your new brass just enough so that your trimmer makes them consistent from neck mouth to shoulder. Your neck turner headspaces on the neck mouth, so when you turn your brass your cut into the shoulder with your neck turner will be very consistent. Then clean up your brass, load it, shoot it, and trim to final dimension after first firing.

 

[dkhunt14]

I never had Lapua brass in 6BR vary that much in length. I just chamfer and turn. I don't trim to after they are a Dasher. I stop short of the shoulder junction and when formed the turn goes into the middle of the shoulder so if a case varies a few thousandths it doesn't matter. Matt

 

[Erik Cortina]

I never had Lapua brass in 6BR vary that much in length. I just chamfer and turn. I don't trim to after they are a Dasher. I stop short of the shoulder junction and when formed the turn goes into the middle of the shoulder so if a case varies a few thousandths it doesn't matter. Matt

I agree with dkhunt on 6BR brass that will be fireformed into a Dasher or BRX. But it you will not move the shoulder, then I recommend that you do as I described above.

 

[mikecr]

Yeah, there are special cases that take more planning with distance turned.
And there can be special cases where you actually would want to turn after fireforming(for extending necks). But this would not be tight neck to begin so that turning would be skim.
You can have old cases where so much brass thickness has migrated forward(through FL sizing), that eventually the necks would need re-turned.

But by far, most turning situations can & probably should be handled with new brass(initially).