Inconsistent trim length

[Chernobyl]

Hand loading some 3x fired Hornady brass and after trimming with Wilson ultimate trimmer with micrometer, I am getting trim lengths varying as much as .005. The micrometer trimmer is set at fixed position so that is not cause. I’m applying same amount of pressure to handle so eliminated that possibility. Mitutoyo digital has been triple checked so that’s not the issue. This has never happened with 1x or even 2x fireformed brass. I am knew to handloading so wondering if anyone else has had this problem and knows a fix?

I’m probably wrong but have narrowed it down to two possibilities.

1) case heads are not square due to firing and ejecting from rpr 6.5

2) work hardened brass is causing inconsistent trims.

Could either be the cause? Thanks in advance

 

[Rocketvapor]

1) dull cutter
2) Stopping before it stops cutting.

Pressure on the neck edge will deflect the brass. Spin until it completely stops.

 

[Chernobyl]

Trimming unit is like brand new (trimmed maybe 150 cases with it) and I make sure I’m spinning until cutting is complete. Also if your familiar with the Wilson ultimate case trimmer there is no way misalignment or deflection of brass can be caused by pressure.

 

[RTH1800]

Inconsistent pressure on the cutting crank will cause this. Also if you cut too fast brass gets hot and expands. Then cools and shrinks.

 

[crunchy]

I have had the same issue with my RCBS trimmer. Would be nice to be able to trim all the brass to the same exact length without having to think about too much pressure or how fast you are trimming.

 

[Threadcutter308]

Hmmm ..........I have a 20 year old manual Wilson trimmer and have never had any problems. Thousands of rounds through it. I lean in the direction of the post(s) above about inconsistent pressure and stopping the cutting action too soon.

 

[Evintos]

What is the case length you're trying to achieve?
What is the shortest case you've measured after trimming?
What is the longest case you've measured after trimming?
What were your pre-trim lengths?

Just want to rule out the possibility that the pre-trim length for your shortest fired cases were shorter than your set case trim length.

 

[Chernobyl]

Case length trying to achieve is 1.915
Shortest after trimming is 1.908
Longest case after is 1.916
Pre trim length avg was 1.9185

 

[Chernobyl]

If you guys don’t think it could be unsquare case heads then I guess it must be inconsistent pressure and speed. I did have a few beers and was getting frustrated with different trim lengths. I’ll try again this afternoon.

 

[Threadcutter308]

If you guys don’t think it could be unsquare case heads then I guess it must be inconsistent pressure and speed. I did have a few beers and was getting frustrated with different trim lengths. I’ll try again this afternoon.

If you have “un-square” case heads, that is the fault of your bolt face, not your trimmer. I doubt that is what is going on though.....

 

[Rocketvapor]

Considering the length to diameter ratio of a 6.5 case you would be able to see an unsquare head by standing them on the kitchen counter.
Google leaning tower of Pisa which is now at 4 degrees tilt.

 

[Chernobyl]

So I’m currently doing load developement with this brass. What variation in length ( ie .001, .002, .003 etc ) should I allow before cullingand using as sighters.

 

[Threadcutter308]

So I’m currently doing load developement with this brass. What variation in length ( ie .001, .002, .003 etc ) should I allow before cullingand using as sighters.

I think the max variation I’ve ever seen in one lot has been .0015”, maybe less. At those kinds of numbers, I consider the trimmed brass good to go.

 

[Chernobyl]

Well I cleaned everything to make sure there were no shavings getting in way, slowed turning of crank, and also held minimal pressure while making certain I trimmed until complete. Trim lengths are consistently hitting desired length of 1.915. Thanks for everything guys. Just goes to show shit doesn’t work as desired once you get pissed. Glad I quit and asked y’all rather than throwing trimmer across garage like I wanted to.

 

[Bradu]

I had that issue when I put the drill adapter on mine. Said fuck it and went back to trimming by hand before I got a Giraud.

 

[DownhillFromHere]

I use a 40-year-old Forster trimmer equipped with a new 3-in-1 trim/chamfer head, powered by a cordless drill. It took some practice but I can now get most - not all but most - of my cases within 0.0005 of desired length. Consistent rpm, pressure and sensitivity to sound and feel of the cutter head are the secret. I can do one case every 15 seconds or so. It took "experimenting" with a couple dozen cases to get to that point.