Can someone explain?

[Dave Way]

Why people clean up only part of the neck when neck turning? I hear and see it all the time. “I just did a skim cut” or “I clean them up 60-70 percent”.

If you are neck turning and only clean up 60 percent of the case, it should be pretty obvious that the neck was not uniform, so why not clean it up completely instead of leaving it non-uniform? Why not take off that last fraction of a thousandth? I always clean mine up completely. I know that I have made the neck walls as close to perfect as I can.

If someone were to say “it’s a no turn neck so I didn’t want to remove too much“, kind of defeats the purpose of having a rifle chambered for a no turn neck. I’m just curious to hear others thoughts on this.

Now I have to go mow 60-70 percent of my yard so I will check on this thread afterwards.

Thanks-Dave.

 

[bcarico]

Why people clean up only part of the neck when neck turning? I hear and see it all the time. “I just did a skim cut” or “I clean them up 60-70 percent”.

If you are neck turning and only clean up 60 percent of the case, it should be pretty obvious that the neck was not uniform, so why not clean it up completely instead of leaving it non-uniform? Why not take off that last fraction of a thousandth? I always clean mine up completely. I know that I have made the neck walls as close to perfect as I can.

If someone were to say “it’s a no turn neck so I didn’t want to remove too much“, kind of defeats the purpose of having a rifle chambered for a no turn neck. I’m just curious to hear others thoughts on this.

Now I have to go mow 60-70 percent of my yard so I will check on this thread afterwards.

Thanks-Dave.

I don't turn necks, I don't think it improves accuracy in my 1000yd rifles. But, If I were to go back to turning necks I definitely think a complete cut makes way more sense than skimming them.

 

[JimSC]

I assume some people skim cut because they want to maintain the same neck tension and have fixed diameter sizing dies. Just a guess, I just started down this rabbit hole and doing some experimenting with neck turning

remember that for every .001 the neck brass gets thinned you need to go down on your neck sizing bushing to get the same tension

example : neck brass is .015 thick and the bullet diameter is .243

to get .003 compression on the bullet seating you use a .270 neck bushing
(.015 + .015 +.243)- .003 = .270

you turn the neck and remove .001 off the neck wall thickness so now the wall thickness is .014, to get .003 compression on the bullet
(.014 + .014 + .243) - .003 = .268

this is assuming annealed brass with no springback

not a problem with bushing dies, just replace with a smaller bushing. However if your die has a fixed diameter neck you just took away .002 of neck tension by making that neck wall .001 thinner

 

[Willie]

My guess, a skim turn will reduce runout noticeably and still not increase chamber neck clearance excessively.

 

[Rick300]

My guess, a skim turn will reduce runout noticeably and still not increase chamber neck clearance excessively.

Exactly. In hunting rifles at least, I have found that an approximately 75% skim cut was one of the biggest factors in improving group sizes. In benchrest rifles, I'm not sure you would get the same amount of improvement because generally we use better components, but I still think there is a pretty good improvement. But, you couldn't tell from my scores!

 

[338 Mollett]

You owe me a computer screen, I swatted the damn bug !

 

[Dusty Stevens]

If a skim cut goes all the way around on most of the length of the neck itll be just fine

 

[searcher]

On a lot of brass - to get completely clean metal on ALL pieces of brass may entail taking off more than one wants to be left with. Super thin necks crack more easily and are more fickle to hold tension. The idea is to uniform tension and eliminating the seemingly ever-present bulge on one side which pushes concentricity way off. If I were using Federal brass, for example, I can usually turn clean and still have lots left to work with. Not so on Winchester or Remington - or even a bad lot of Lapua. Also - on semi-autos, best practice is to take off about 70% of the average case - and to leave as much material as one can, as going completely clean will most often be counterproductive due to weak necks getting tweaked in the "stripping and loading" process. When going for "60% to 75% clean", some cases may come out 40% clean and some 100%, depending on the integrity of the brass being turned. All that said - if one CAN turn 100% clean with the lot of brass they have - and it does not impair the brass for the intended use - there is nothing wrong with that either. It is just that it doesn't always work out that way.

 

[JohnKielly]

I used to skim cut after first firing of my Palma brass using a specially made mandrel because evidence was offered that the neck expanded more on one side.

Then I said what the heck, and had my barrels cut with my reamer to the same degree of crush on the shoulder & the evidence wasn't there for me any more. I hate doing anything that doesn't result in improvement on the target.

 

[searcher]

I used to skim cut after first firing of my Palma brass using a specially made mandrel because evidence was offered that the neck expanded more on one side.

I think most people turn necks to correct known deficiencies in necks that exist before they are ever fired - not to correct what a bad chamber does to their brass - as that would be an endless game, indeed.

 

[SeabeeKen]

I don't turn necks, I don't think it improves accuracy in my 1000yd rifles. But, If I were to go back to turning necks I definitely think a complete cut makes way more sense than skimming them.

I tested several of my match barrels with turned and unturned necks of the same Norma brass and found no difference at all in my groups. I did find significant improvement in groups and numbers by using light neck tension and lubing inside of necks before seating. I no longer turn necks unless tight chamber demands it