Consistency of case trimming

[marchx]

I use the Hornady trimmer and after trimming I measure the cases with my caliper. I don't get the same case length every time.
It's supposed to be a simple operation- you take a reference case, you lock it in the trimmer and set the length of trimming for the rest of the cases. then you put in the shell holder the next case and trimm it to the set length (i.e. until metal shavings stop to fly). chamfer&deburr. period. you repeat it for all other cases.
what am I doing wrong to get 1-2thau of a difference between cases? Sorry guys, I know this is trivial operation. But even a trivial operation can be performed in a wrong way. Yes, I know I can have a shitty caliper and measure the cases in a wrong way. So, what would be the correct way then.

 

[CNC-Dude]

You are probably assuming your case trimmer is an ultra precision piece of equipment and its probably performing its function within its capabilities. So a one to two thousandths variance is probably as good as it can do.

 

[Geezedtee]

Unless you are chamferring/deburring various amounts then it is probably the position of the case when you put it in the caliper. Or as the previous guy said it's the tolerance of the calipers. Either way I don't think a variation of 1 or 2 thou is going to affect anything, unless you're shooting at flies at 1000 yards ;-)

 

[Straightshooter1]

Unless you are chamferring/deburring various amounts then it is probably the position of the case when you put it in the caliper. Or as the previous guy said it's the tolerance of the calipers. Either way I don't think a variation of 1 or 2 thou is going to affect anything, unless you're shooting at flies at 1000 yards ;-)

Yeah. I like shooting at flys and try to get head shots.

 

[marchboom]

As much as I like to have my cases all turn out the same length, no matter what you do you will have some that will be off .001-.002". IMO that will not affect anything.

Sometimes you just have to know when to say, "That's good enough".

 

[Mark W]

@Straightshooter1 do you have a file to print that target, or do you order them somewhere?

 

[Retired Grunt]

I bought the Hornady, used it twice, switched to the Lyman Case Trim Express and once I set it I to length just run it.

 

[Bill Norris]

I switched to the Frankford Arsenal trimmer (the drill driven model) recently and it seems to be doing great for me.

 

[potatojudge]

I had issues with inconsistencies, out of square, or chatter with various trimmers. Back to Wilson for me- slower but perfect cuts, and I appreciate indexing off the base rather than an inconsistent shoulder (not that it really matters, I realize).

 

[tmwinds]

A sheet of notebook paper is about .004 thick. Try visualizing how small .001-.002 is and how it could possibly affect the quality of your ammo.

 

[JohnKielly]

I had issues with inconsistencies, out of square, or chatter with various trimmers. Back to Wilson for me- slower but perfect cuts, and I appreciate indexing off the base rather than an inconsistent shoulder (not that it really matters, I realize).

System Wilson because indexing off the base means:

I trim consistently​

My neck chamfer is uniform​

 

[LC Tikka]

A trimmer that rotates the case is a good start.

 

[timeout]

Wilson trimmer and hold down and rearward on the case holder with your hand. Capable of holding .0005". Using the clamp to bear down on the case holder results in trimmed length inconsistency for me.

 

[Straightshooter1]

@Straightshooter1 do you have a file to print that target, or do you order them somewhere?

I have targets I've collected in several files that has been shared on various websites. Attached is my file that has that target:

 

[Straightshooter1]

I use the Hornady trimmer and after trimming I measure the cases with my caliper. I don't get the same case length every time.
It's supposed to be a simple operation- you take a reference case, you lock it in the trimmer and set the length of trimming for the rest of the cases. then you put in the shell holder the next case and trimm it to the set length (i.e. until metal shavings stop to fly). chamfer&deburr. period. you repeat it for all other cases.
what am I doing wrong to get 1-2thau of a difference between cases? Sorry guys, I know this is trivial operation. But even a trivial operation can be performed in a wrong way. Yes, I know I can have a shitty caliper and measure the cases in a wrong way. So, what would be the correct way then.

Whether it's your calipers or you're trimming device or both, that amount of difference in the results can easily be attributed to the variance in the amount of pressure applied during the trimming process and, as I'm sure you're aware, the pressure applied to the calipers. Even a little dirt/dust accumulation can throw those thing off.

As others have mentioned, that amount of variance isn't going to have any detectable difference in your cartridge's performances. For me, the reason I like to have as consistent case lengths is so that I don't run into any issue as the carbon ring builds up. Though I removed the carbon ring every time I clean my rifles, so even this carbon ring issue isn't likely to be a problem if in rare occasions I happen to have some cases longer than normal.

 

[Mark W]

Thanks @Straightshooter1!!!!

 

[Geezedtee]

Yeah. I like shooting at flys and try to get head shots.

View attachment 1285216

No castrations then?

 

[Kracken McGraw]

System Wilson because indexing off the base means:

I trim consistently​

My neck chamfer is uniform​

In the Bulletin the Boss has a great deal on the Wilson trimmer “Deals of the Week”, in case anyone missed it.

 

[Coyotefurharvester]

Tolerance stacking, and the inside necks need equal lube for pilot style trimmers.