Neck Trimming ?

[wkdickinson]

OK, I've been reloading and competing (various disciplines) for a long time. I totally get neck trimming to make sure your case isn't to long for the chamber. But for "accuracy" does having a consistent neck length really matter? If so, how much difference is too much and why?

 

[60723]

Inconsistent neck length means inconsistent neck tension. Probably means higher ES. Depends on how much vertical you can accept.

 

[Bill Norris]

OK, I've been reloading and competing (various disciplines) for a long time. I totally get neck trimming to make sure your case isn't to long for the chamber. But for "accuracy" does having a consistent neck length really matter? If so, how much difference is too much and why?

He did not mention accuracy but in a podcast "Believe the Target" with Erik Cortina Lou Murdica said with pressure testing in the tunnel he saw differences with only a few thousandths of neck length.

 

[SeabeeKen]

Another issue i watch for, if one side of the neck is longer than the other, the bullet can still be touching one side while the other is unsupported upon bullet exit. This can be seen after fireforming new shoulders etc. i trim enough to keep them squared up when necessary

 

[Straightshooter1]

Inconsistent neck length means inconsistent neck tension. Probably means higher ES. Depends on how much vertical you can accept.

In addition to that neck tension, there'll be a difference in the timing for the blow by effecting pressures.

 

[6BRA]

Can you accept .002 trim length variations from a henderson. Ill answer this...Wilson 99 percent are dead nuts and if there is any variation never more than .0005. Volume power tools don't give the best results. Oh wait..here comes the comment can you shoot the difference. Probably. If I was given a power tool, I would resell it myself.

 

[6BRA]

Another issue i watch for, if one side of the neck is longer than the other, the bullet can still be touching one side while the other is unsupported upon bullet exit. This can be seen after fireforming new shoulders etc. i trim enough to keep them squared up when necessary

certain collet style trimmers used to trim in this manner. The old Forster trimmer/ collet mandrel. Necks were never square. There are others as mentioned.

 

[D-4297]

I use a RCBS Trim-Pro II , with a 3 way cutter head , and yes , It is a bit of a pain doing all that cranking , but my cases finish at +.000 , -001 , and I can live with that .

Some time back ; Laurie did some testing about this issue , and I read where he "felt" that any length deviation more than .003 could have a effect on accuracy , if I read that correctly . I do understand how that can be a valid statement .

 

[qldreloader]

Slight tangent but I really wish that I could buy cases that had extra long necks so that I could trim to fit in chamber with say 5 thou clearance. I think it would cut back on carbon ring issues in factory barrels.

 

[Timon]

I have used a Wilson for a long time. You set what you want and it cuts it just about dead on every time. I’m in my 70’s, so a while back I started using the power attachment for it. Using the power attachment is much easier than turning the crank to trim the cases. I know that there are a lot of new trimmers out there, but I will stay with my Wilson one. It’s very simple, built like a tank, with heavy stainless parts, so why switch to something more complicated. Just my thoughts.

Scott

 

[JFrank]

If I had a week to think up a list of weird stuff that would affect a group at any distance. Uneven trimming the thickness of a human hair

OK, I've been reloading and competing (various disciplines) for a long time. I totally get neck trimming to make sure your case isn't too long for the chamber. But for "accuracy" does having a consistent neck length really matter? If so, how much difference is too much and why?

would likely not make the top fifty.

Regarding length, I stay back .015-.020 from the lands.

 

[D Coots]

Slight tangent but I really wish that I could buy cases that had extra long necks so that I could trim to fit in chamber with say 5 thou clearance. I think it would cut back on carbon ring issues in factory barrels.

Any idea how far the neck pushes foreward upon ignition?

Later

Dave

 

[Steve Donlon]

Slight tangent but I really wish that I could buy cases that had extra long necks so that I could trim to fit in chamber with say 5 thou clearance. I think it would cut back on carbon ring issues in factory barrels

Any idea how far the neck pushes foreward upon ignition?

Later

Dave

If I had a week to think up a list of weird stuff that would affect a group at any distance. Uneven trimming the thickness of a human

matter?

If I had a week to think up a list of weird stuff that would affect a group at any distance. Uneven trimming the thickness of a human hair


would likely not make the top fifty.

I never thought much about how far the mouth of the neck was away from the rifling but if new brass is shorter that the max length, just trim everything to the shortest length? I don't know why I was hung up on getting it to the max length if it take forever to get there. Always wanted more neck length for accuracy. So as long as they are even? Makes sense.

 

[N133]

Another issue i watch for, if one side of the neck is longer than the other, the bullet can still be touching one side while the other is unsupported upon bullet exit. This can be seen after fireforming new shoulders etc. i trim enough to keep them squared up when necessary

Can also affect bullet runout, when seating if the base of the bullet hits the high side of the case mouth it may/can tilt until it hits the low side of the case mouth and be forced into the neck a bit crooked. Worse with flat base bullets with pressure rings.

 

[TA17rem]

Sinclair makes O.A.L. case gauges to measure inside length for your brass cases. It will tell you where it stops and then just subtract .020 from that and it gives you max. case length then subtract .010-.020 from that for trim length. Many chambers give you room for case stretching but to be safe side you need to gauge them as some chambers are a little shorter at times and even a custom chamber can be off. Case mouths should always be squared up and chamfered/beveled.

 

[ELR LVR]

Any idea how far the neck pushes foreward upon ignition?

Later

Dave

The same amount the shoulder pushes forward.

 

[D Coots]

Probably How far foreward, and then how far does it spring back?

Is this another theory deal or a measurement?

Later

Dave

 

[TA17rem]

If cases is formed correctly, it shouldn't move the shoulder forward or back. Nothing should move other than neck growth/brass flow.

 

[D Coots]

Ok. So how about the neck moving?

To start it will move the same as shoulder bump, and then?

Probably trimming due to brass flow.


Why not trim less if it's not moving?