Trimming brass to same length?

[Richard Coody]

personally over time i have found that my best results with neck turning and trimming after my cases are fully fireformed. i will turn new cases but not trim. you can be suprised how much shorter necks can get after fireforming.

After the cases are fully fireformed i anneal, neck turn again and then trim. you have a consistent shoulder at this point. for neck turning fireformed brass i use a tight bushing and then run the expander through for a tight fit.

 

[Brians356]

Doesn't running the virgin brass through a sizer die prior to trimming solve this?

Size, trim, then neck turn. That's how I was taught to do it.

There's more potential variation creeping in from shoulder springback. By indexing the trimmer off the shoulder you eliminate needing the shoulder-to-base datum length being perfectly consistent. There is little or no brass compression involved. You index the trimmer off the shoulder with no stress, then index the turner off the fresh case mouth, also with no stress. The length of the neck is relatively short. Seems to me there's a lot less chance for more than a small fraction of a thousandth of accumulated variance to creep in when making that cut into the shoulder with the turner.
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[Dusty Stevens]

I'm with you, but for that to work well your neck trimmer must index off the shoulder. Does yours?
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mine does. every one worth having does.
giraud- best but $$$
PMA- very good and easy
little crow- works good
various homemade type quick trimmers with the end mill in the barstock- low money but very effective.

these all index off the shoulder properly.

 

[Bart B.]

No question lower ES will shoot tighter groups at 600 yards and beyond.

Why wouldn't lower ES numbers shrink groups at all ranges?

Vertical shot stringing in MOA increases with range for a given muzzle velocity spread. Assuming they all leave at the same angle above the LOS.

If the barrel has positive compensation for bullets' muzzle velocity spread (they exit on the muzzle axis up swing), long range groups will have smaller MOA numbers than short range groups.

Moving a tuning weight on the muzzle changes its vibration frequency so bullets leave at the best place compensating for drop at target range.

 

[jimmymac]

There's more potential variation creeping in from shoulder springback. By indexing the trimmer off the shoulder you eliminate needing the shoulder-to-base datum length being perfectly consistent. There is little or no brass compression involved. You index the trimmer off the shoulder with no stress, then index the turner off the fresh case mouth, also with no stress. The length of the neck is relatively short. Seems to me there's a lot less chance for more than a small fraction of a thousandth of accumulated variance to creep in when making that cut into the shoulder with the turner.
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Yet, I've had no consistency issues doing it the way I was instructed. The brass turned out great.

 

[Brians356]

Yet, I've had no consistency issues doing it the way I was instructed. The brass turned out great.

I don't doubt you, and so have I. There's just more that needs to go right. If you have quality virgin brass (consistently annealed), you make sure all shoulders get pushed back a bit, and trim to dead equal case lengths, there's no reason you can't get shoulder cuts that appear equal. I just like removing the case OAL and shoulder position from consideration in the neck turning process.

Plus, I feel indexing the trimmer off the shoulder produces more consistent neck lengths than indexing off the base (full case length), and more quickly. Inserting a case into a Little Crow or Giraud is not unlike using an electric desk pencil sharpener - you push it until you feel and hear it stop cutting. I hate conventional lathe-style trimmers.
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[ClassCat]

Food for thought Brian. If you cut Virgin brass and fire form, is your first cut and prep on a false dimension no matter where you index from ?

 

[muleman69]

What is the take on Wilson type trimmers?

 

[Brians356]

Food for thought Brian. If you cut Virgin brass and fire form, is your first cut and prep on a false dimension no matter where you index from ?

What do you mean by "cut"? Trim? Neck turn? I need to fully understand your hypothetical before responding.

But, personally, I fireform before doing any trimming or turning.
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[LHSmith]

What is the take on Wilson type trimmers?

My preference for competition prep.

 

[jimmymac]

^^^^
Consistent results. A little slow but worth it to me. I like my Wilson.

 

[ireload2]

I have several rifles in which the chamber is one millimeter .040" longer than the trim length of 2.110. When new cases are fire formed with a full power load the cases get .004 to .007 shorter. So I trim newly formed brass to the same length as the chamber (2.150) and fire them. Usually they wind up 2.145 long. If any are longer by .001 or .002 I trim the long ones and the lot is ready to be reloaded again.

 

[ClassCat]

What do you mean by "cut"? Trim? Neck turn? I need to fully understand your hypothetical before responding.

But, personally, I fireform before doing any trimming or turning.
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It's not hypothetical,everything, Neck turn, shoulder cut (SO LIGHTLY) Trim for length, Shoulder bump and neck size for fire forming.
What caliber are you shooting and what is the brass neck dimensions and chamber neck dimension ?
I shoot PPC with a 262 neck, you cannot chamber a 220 Russian without cutting first.

 

[ClassCat]

This is what 25 thousandths off in neck trim length looks like

 

[suasponte]

^^^^
Consistent results. A little slow but worth it to me. I like my Wilson.

Ditto!

 

[270WinDude]

Good thread! Is there any logic behind trimming a certain amount back or specific distance? I'm at a point where I have a ton of fire formed brass that has reached longer then the spec'ed max case length. I don't think it's hitting (the chamber, I do think it's pushing carbon forward or interacting some how) yet but I don't want to risk anything. I dug this thread up because I was seeing some things that made me wonder about case length and implications primarily pertaining to carbon build up. Might need to dig up that book that was mentioned. Trimming back from 2.54 to 2.53 seems like a lot but as far as carbon build up it might be a smoother fit to keep it all trimmed to the length of new brass but it seems like a lot of room so I'm wanting to trim just a hair back from max since I think my chamber is a hair over spec anyway.

 

[Dusty Stevens]

Good thread! Is there any logic behind trimming a certain amount back or specific distance? I'm at a point where I have a ton of fire formed brass that has reached longer then the spec'ed max case length. I don't think it's hitting (the chamber, I do think it's pushing carbon forward or interacting some how) yet but I don't want to risk anything. I dug this thread up because I was seeing some things that made me wonder about case length and implications primarily pertaining to carbon build up. Might need to dig up that book that was mentioned. Trimming back from 2.54 to 2.53 seems like a lot but as far as carbon build up it might be a smoother fit to keep it all trimmed to the length of new brass but it seems like a lot of room so I'm wanting to trim just a hair back from max since I think my chamber is a hair over spec anyway.

Unless you know your reamer trim length youre pretty much just guessing

 

[ClassCat]

Good thread! Is there any logic behind trimming a certain amount back or specific distance? I'm at a point where I have a ton of fire formed brass that has reached longer then the spec'ed max case length. I don't think it's hitting (the chamber, I do think it's pushing carbon forward or interacting some how) yet but I don't want to risk anything. I dug this thread up because I was seeing some things that made me wonder about case length and implications primarily pertaining to carbon build up. Might need to dig up that book that was mentioned. Trimming back from 2.54 to 2.53 seems like a lot but as far as carbon build up it might be a smoother fit to keep it all trimmed to the length of new brass but it seems like a lot of room so I'm wanting to trim just a hair back from max since I think my chamber is a hair over spec anyway.

If your Smith is using a certain reamer ask what the OAL is. If it is a factory chamber go with SAAMI specs. Problem solved.

 

[JMayo]

I shoot a bra. Brass doesn't grow much.
On a new 200 I measure, find the shortest and make all of them the same. Done deal.
Wilson trimmer in my bench vice.
I try to have/do everything the same in every way.
Wanting small groups in the 10 ring !

 

[mikecr]

No, don't make them all the shortest. There is absolutely no good reason to do that.
The further your case mouths are from chamber end, the faster/higher carbon rings can grow.
Some depends on your pressure, tension (grip), and neck clearance. What you can manage in trim length depends on the cartridge and your sizing of cases. Every bit of this results of your choices.

Stay within 5thou of chamber end, 10thou max, and it's less likely you'll ever need concern yourself about a carbon ring. Some might suggest this is too difficult or impossible, but it only follows bad or no planning on their part.