View Full Version : Case trimming technique

05-07-2011, 06:38 PM
Hi need a bit of advice here about case trimming

I purchased a Wilson case trimmer system

If I take one particular caliber I look after 6.5 x 55 sweede

the SAMMI published length is 2.165 inches

I tried to use a Sinclair chamber length gauge (gage - as printed)

used a fired case, partially neck size it and insert the gauge into this case

however I have a break open hunting blaser K95 rifle so that's where my first difficulty comes I cannot push the adapted cartridge into this chamber slowly with a bolt

Anyway I turn to another rifle 6 x 47 lapua

I shoot only lapua brass

and on first fired cases they vary at most 0.004 in extreme spread ES

At this point in time they are all below the measured chamber dimension less shall we say 0.04 as my datum point

However I can see with my naked eye that quite a few cases are NOT squared ?

Question one what do I do about that with the Wilson case trimmer at this stage
I would love to square them but the Wilson is not really the best tool since I have to adjust each screw for length individually - any suggestion for a faster way to square things off without trimming it much ? I DON'T really want to lose neck length for accuracy sake - am I correct ?

So my decision now is to monitor the length after each firing until cases surpass my chosen datum - question 02 - is this correct ?

Thanks for any input

Please criticize so I can learn from you folks

Boyd Allen
05-07-2011, 07:39 PM
The lost length will not hurt your accuracy. Find your shortest case, not counting some oddball that is way short. Trim it enough to make a cut on the whole end of the neck, and then trim them all to that length. The only exception is if you are on the edge of having enough bullet engagement to securely hold the bullet in the case neck. At to those Sinclair chamber length gauges, there is no way that I would use one on any good barrel. They are made of mild steel , and you wouldn't catch me forcing one into a partially sized neck, by closing a bolt or action. Jack Neary has half a dozen segments on loading for benchrest on YouTube. If you watch them about three times and take notes, I think that it would be a good use of your time. It was for me. Good Luck

05-07-2011, 07:50 PM
Thank you for sharing your experience
I will return the gauges to the reloading shop next week

Roy Allain
05-08-2011, 10:53 AM
Is the shell holder for new brass or fired brass? The cartridge holder and the brass both have different dimensions and could be where you're having problems if you're mixing them together.

First, make sure you have the proper cartridge holder. Next, full length resize your brass. Then select the shortest piece (as Boyd stated above) and use that to set your trimmer. Should be good to go after that.

If you want a chamber length gauge, buy a Wilson or Forster or PTG.


Bob Kingsbury
05-08-2011, 11:11 AM
Boyd is right about not using steel case length gages. If you have access to a lathe, they can easily be made of brass.
Correctly the gage should be a thou or two under neck dia. at its largest point. Do not put a large chamfer on the end,
just break the edge. You must also shorten the case, so the total length is less than the chamber. If you have a borescope,
you can also drill out the primer pocket, allowing the borescope to pass thru it. This works great with wildcats. Be sure the
case is fully seated in the chamber. The end clearance will be very visible.