Page 1 of 1
Neck thickness
Posted: Wed Oct 04, 2017 10:17 am
by MISSED
The reamer that was used for my 20 BR has a .235 neck.
Which is a no turn for Remington Brass
But This meant I had to turn the necks as the lapua brass when loaded has a neck dimension of .235.
No biggie I just sat down and did a few cases while I waited for the barreled action to be returned.
I turned the necks to .14 (.14+.14+.204 = .232)which should give have given me 3 thou clearance.
The neck thickness after the first firing gave me .15.
(.15+.15+.204=.234)
Back out with the K+N took another half thou (.5+.5=1 which gave me .232 loaded
Where did the brass come from ?
I have not experienced this with the 17 mach1V or Vartarg.
The only explanation I can come up with is the Brass in the Donut had flowed forward.
Is this possible ?
You would have thought the expander mandrel would have pushed the donut out and then would have been cut of on the first neck turn
Maybe the K+N mandrel with the with donut cutter may cure this.
More things to think about.
Re: Neck thickness
Posted: Wed Oct 04, 2017 12:49 pm
by Seddo
I have a few of the cutting mandrels and i dont like them, they mark the inside of the necks on their way down.
You wouldnt have to turn them if they were Norma cases either, they are thinner than Lapua.
Re: Neck thickness
Posted: Wed Oct 04, 2017 1:17 pm
by macca
I have found most cases need to be neck turned twice. If you don't cut into the shoulders quite deep enough brass flows forward. I always turn them again after first firing. Usually only a smidegon but sometimes 1 thou comes off.
Cheers.
Re: Neck thickness
Posted: Wed Oct 04, 2017 2:25 pm
by MISSED
Seddo I bought 200 lapua cases and the reamer that was ordered was the 20 BR Lapua reamer to suit the brass.But they sent a 22BR reamer instead
then I borrowed a 20 BR reamer that was set up for Remington ,Norma brass.
Macca thanks for the reply used the K+N 30 degree cutter and went into the shoulder for what I thought was far enough but obviously not far enough.It just surprised me how far and by how much the Brass flowed.
live and learn I suppose
Re: Neck thickness
Posted: Wed Oct 04, 2017 7:31 pm
by Camel
Re: Neck thickness
Posted: Thu Oct 05, 2017 5:10 am
by Rabbitz
How did I know this would degenerate to this, just from reading the thread title?
Re: Neck thickness
Posted: Thu Oct 05, 2017 1:13 pm
by Glenn
Seddo wrote: ↑Wed Oct 04, 2017 12:49 pm
I have a few of the cutting mandrels and i dont like them, they mark the inside of the necks on their way down.
You wouldn't have to turn them if they were Norma cases either, they are thinner than Lapua.
Norma's good but if you can use Lapua why wouldn't you!
I was sent this picture because I was the first person they thought of when they seen it!
All I need is the Monocle and a top hat!
As Macca said a bit of movement after is expected.
Bit more powder in a 20BR than the 17 Mach IV and Vartarg which could explain the brass flowing forward!
Glenn
Re: Neck thickness
Posted: Thu Oct 05, 2017 8:13 pm
by Seddo
Glenn wrote: ↑Thu Oct 05, 2017 1:13 pm
Norma's good but if you can use Lapua why wouldn't you!
Glenn
Because I'm lazy and done want to neck turn if I done want to!
That's why I use Norma 22PPC cases to form 20ppc, one or two pushes through the sizer and you can shoot them.
Re: Neck thickness
Posted: Sat Oct 14, 2017 6:16 am
by RDavies
MISSED wrote: ↑Wed Oct 04, 2017 10:17 am
The reamer that was used for my 20 BR has a .235 neck.
Which is a no turn for Remington Brass
But This meant I had to turn the necks as the lapua brass when loaded has a neck dimension of .235.
No biggie I just sat down and did a few cases while I waited for the barreled action to be returned.
I turned the necks to .14 (.14+.14+.204 = .232)which should give have given me 3 thou clearance.
The neck thickness after the first firing gave me .15.
(.15+.15+.204=.234)
Back out with the K+N took another half thou (.5+.5=1 which gave me .232 loaded
Where did the brass come from ?
I have not experienced this with the 17 mach1V or Vartarg.
The only explanation I can come up with is the Brass in the Donut had flowed forward.
Is this possible ?
You would have thought the expander mandrel would have pushed the donut out and then would have been cut of on the first neck turn
Maybe the K+N mandrel with the with donut cutter may cure this.
More things to think about.
My thoughts are this. When you originally cut the brass, it might not have been exactly .014", it could have been .0144" but your digital verniers rounded it down (or just weren't super super accurate). The bullet might have been a few tenths of a thou oversized which is pretty common. Lets say they were .2043" diameter, not all that rare. So with tolerance stacking you easily have another 1.1 thou, possibly more.
Then after you fire the case, the powder residue build up in the neck will usually add another .001" or so.
So now you easily have an extra .0021" in diameter from what you thought your brass was.
Re: Neck thickness
Posted: Sat Oct 14, 2017 7:55 am
by kickinback
RDavies wrote:MISSED wrote: ↑Wed Oct 04, 2017 10:17 am
The reamer that was used for my 20 BR has a .235 neck.
Which is a no turn for Remington Brass
But This meant I had to turn the necks as the lapua brass when loaded has a neck dimension of .235.
No biggie I just sat down and did a few cases while I waited for the barreled action to be returned.
I turned the necks to .14 (.14+.14+.204 = .232)which should give have given me 3 thou clearance.
The neck thickness after the first firing gave me .15.
(.15+.15+.204=.234)
Back out with the K+N took another half thou (.5+.5=1 which gave me .232 loaded
Where did the brass come from ?
I have not experienced this with the 17 mach1V or Vartarg.
The only explanation I can come up with is the Brass in the Donut had flowed forward.
Is this possible ?
You would have thought the expander mandrel would have pushed the donut out and then would have been cut of on the first neck turn
Maybe the K+N mandrel with the with donut cutter may cure this.
More things to think about.
My thoughts are this. When you originally cut the brass, it might not have been exactly .014", it could have been .0144" but your digital verniers rounded it down (or just weren't super super accurate). The bullet might have been a few tenths of a thou oversized which is pretty common. Lets say they were .2043" diameter, not all that rare. So with tolerance stacking you easily have another 1.1 thou, possibly more.
Then after you fire the case, the powder residue build up in the neck will usually add another .001" or so.
So now you easily have an extra .0021" in diameter from what you thought your brass was.
I can't believe anyone actually uses vernier calipers for definition beyond 1mm.
Sent from my iPhone using Tapatalk Pro
Neck thickness
Posted: Sat Oct 14, 2017 7:57 am
by kickinback
RDavies wrote:MISSED wrote: ↑Wed Oct 04, 2017 10:17 am
The reamer that was used for my 20 BR has a .235 neck.
Which is a no turn for Remington Brass
But This meant I had to turn the necks as the lapua brass when loaded has a neck dimension of .235.
No biggie I just sat down and did a few cases while I waited for the barreled action to be returned.
I turned the necks to .14 (.14+.14+.204 = .232)which should give have given me 3 thou clearance.
The neck thickness after the first firing gave me .15.
(.15+.15+.204=.234)
Back out with the K+N took another half thou (.5+.5=1 which gave me .232 loaded
Where did the brass come from ?
I have not experienced this with the 17 mach1V or Vartarg.
The only explanation I can come up with is the Brass in the Donut had flowed forward.
Is this possible ?
You would have thought the expander mandrel would have pushed the donut out and then would have been cut of on the first neck turn
Maybe the K+N mandrel with the with donut cutter may cure this.
More things to think about.
My thoughts are this. When you originally cut the brass, it might not have been exactly .014", it could have been .0144" but your digital verniers rounded it down (or just weren't super super accurate). The bullet might have been a few tenths of a thou oversized which is pretty common. Lets say they were .2043" diameter, not all that rare. So with tolerance stacking you easily have another 1.1 thou, possibly more.
Then after you fire the case, the powder residue build up in the neck will usually add another .001" or so.
So now you easily have an extra .0021" in diameter from what you thought your brass was.
I can't believe anyone actually uses vernier calipers for definition beyond .1mm.
Sent from my iPhone using Tapatalk Pro
Re: Neck thickness
Posted: Sat Oct 14, 2017 10:55 am
by MISSED
No Vernier Calipers here
Gunn and Moore micrometer
Dial indicator on Turner
Re: Neck thickness
Posted: Sat Oct 14, 2017 8:44 pm
by DSD
How does the Gunn and moore(don’t they make cricket bats) compare to a mitutoyo?
Sent from my iPad using Tapatalk