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Thoughts on the Neck Carbon Ring ?

I don't have any testing pictures of anything.
Just providing my inputs with WHYs.

'Pull force' and friction in general is irrelevant to neck tension and internal ballistics.
If you'd like to test that take two necks, one squeaky cleaned inside, and one dry film burnished with tungsten disulfide(WS2). This will produce way different seating/pull forces.
Shoot them across a chrono and note zero difference in MV. Tune does not change here either.
But like I said in contrast, and anyone here can test it: change neck sizing LENGTH, and MV & tune will change.

The reason is that bullets are not pushed from necks. If they were, everything would be different.
Bullets are released -from neck expansion.
And a neck only needs to barely expand to fully release a bullet, so necks barely need clearance to perform their function just the same. Doesn't matter if 1/10thou or 5thou of neck clearance.

Now someone will say that they need more neck clearance to shoot well,, but they never say WHY.
They never say WHY about anything..
The reason for the clearance/result disparity is chambered tensions, from TIR, from FL sizing of thickness variance.
There is of coarse a test for this as well: stop FL sizing to see ammo straight enough to fire well with tight neck clearance. I know you don't want to do that, it's just another test to prove my point.
Then you can go back to what you do, but I doubt that's more important than the learning in this.

The anecdotal 'when things work well this is what I see', doesn't actually help someone with completely different circumstances to solve their problem. For instance, nobody has declared how to get a sine wave neck sooting, -because 'this is what is happening'. So is it really helpful? Would it apply to 300WSM as it apparently applies to 6PPC? Could it be implied that you MUST have a sine wave to shoot well?
If not, then when & why a difference?
 
As far as the neck carbon sine wave- tony boyer speaks about it in his book and i know when my gun is shooting its smallest it will have the sine wave. It will even have 3 waves on a 3lug action. Neck clearance, tension and load is perfect or real close when you see it. Any slower or faster powder than the case wants it goes away too
I see a lot here talk about that you want a bullet to fall through a fired case, but don’t you need neck clearance tighter than that for a good sine wave pattern?
 
I don't have any testing pictures of anything.
Just providing my inputs with WHYs.

'Pull force' and friction in general is irrelevant to neck tension and internal ballistics.
If you'd like to test that take two necks, one squeaky cleaned inside, and one dry film burnished with tungsten disulfide(WS2). This will produce way different seating/pull forces.
Shoot them across a chrono and note zero difference in MV. Tune does not change here either.
But like I said in contrast, and anyone here can test it: change neck sizing LENGTH, and MV & tune will change.

The reason is that bullets are not pushed from necks. If they were, everything would be different.
Bullets are released -from neck expansion.
And a neck only needs to barely expand to fully release a bullet, so necks barely need clearance to perform their function just the same. Doesn't matter if 1/10thou or 5thou of neck clearance.

Now someone will say that they need more neck clearance to shoot well,, but they never say WHY.
They never say WHY about anything..
The reason for the clearance/result disparity is chambered tensions, from TIR, from FL sizing of thickness variance.
There is of coarse a test for this as well: stop FL sizing to see ammo straight enough to fire well with tight neck clearance. I know you don't want to do that, it's just another test to prove my point.
Then you can go back to what you do, but I doubt that's more important than the learning in this.

The anecdotal 'when things work well this is what I see', doesn't actually help someone with completely different circumstances to solve their problem. For instance, nobody has declared how to get a sine wave neck sooting, -because 'this is what is happening'. So is it really helpful? Would it apply to 300WSM as it apparently applies to 6PPC? Could it be implied that you MUST have a sine wave to shoot well?
If not, then when & why a difference?
I have done actual testing (and so have others) that showed without a doubt that changes in neck tension significantly affect tune, and with that group size. Short version: BS!
 
I do not know of any competitive shooter that views elimination of neck sooting as a goal. All of their goals relate to what happens at the target. Generally in short range group, many people consider that one sign of a well tuned load is a thin soot line on the neck that takes the shape of a rather coarse sine wave. Here is a picture that Jackie Schmidt posted on the subject.
That same sine wave was referred to in Tony Boyers book but I think he talked to Speedy about it.
 
With respect, I disagree about the clearances. I know a couple of short range group record holders, and additionally I would refer you to the series of videos on Youtube by Jack Neary. All say that for best results they want more than .002 clearance, up to .003 and that the larger clearances show up as better accuracy at 200 yards. On the end clearance, I have never seen or heard of anyone improving performance by running it that tight, a lot of theorizing, but no actual test results. In one of his videos Jack, who has been on the USA World Benchrest Championship team, said that for a PPC chamber with a maximum case length of 1.515 he trims to 1.490.
Boyd, is that 25 thousandth off maximum case length a good rule of thumb for most cases?
 
Boyd, is that 25 thousandth off maximum case length a good rule of thumb for most cases?
What I got from Jack's videos was that trimming often helps and that being close to the end of the chamber neck is not important. Beyond that I cannot say. As a little background, for 6PPCs the trim length of 1.490 is common because you kind of have to go that short to get the necks to clean up after fire forming from a .220 Russian cases. I don't think that there is any advantage to that much gap. My point was that there does not seem to be any advantage to being close. Back in the late 90s Tony Boyer tried a PPC reamer with a max of 1.5. I think that he fire formed with a chamber that was longer to make room for the .220 Russian case. The idea was to see if a closer fit gave an advantage. He said that it didn't. I tend to take his word for those sorts of things. Have you watched the Videos? I would recommend them to anyone interested in accuracy, even if they are not in benchrest.
 
What I got from Jack's videos was that trimming often helps and that being close to the end of the chamber neck is not important. Beyond that I cannot say. As a little background, for 6PPCs the trim length of 1.490 is common because you kind of have to go that short to get the necks to clean up after fire forming from a .220 Russian cases. I don't think that there is any advantage to that much gap. My point was that there does not seem to be any advantage to being close. Back in the late 90s Tony Boyer tried a PPC reamer with a max of 1.5. I think that he fire formed with a chamber that was longer to make room for the .220 Russian case. The idea was to see if a closer fit gave an advantage. He said that it didn't. I tend to take his word for those sorts of things. Have you watched the Videos? I would recommend them to anyone interested in accuracy, even if they are not in benchrest.
Thanks Boyd, as always very informative!
I have watched one of Jack’s videos where he would bounce different case preparation ideas off the techs at Lapua. I need to watch more.
 
Proper bushing down sizing makes no more difference to neck tension
Walking a tightrope there... Outside neck measurements can be the same after extracting bullets from cases sized with various bushings - and even a non-bushing factory die - but the amount of tension on the bullet IS affected by those bushings- and therefor the tune. If you see no difference in your accuracy using different sized bushings, you would be the only guy I have ever heard of having such results. Doesn't work for me. If it did, I'd just go .008" under loaded neck size and call it good on everything. Come to think of it - that is pretty much what I did back when I used factory full-length sizing dies.
 

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