Case trimming

[Funky Bunch]

how important is this regarding accuarcy ??

Do we need to trim out cases to gain accuarcy or what tolerence is acceptable

opinions please

[Ronin]

Personally (and its just my opinion) I trim all my cases in a Wilson trimmer (no matter what calibre) and all to exactly the same size. That way the pressure should be all equal when the powder is ignited (I think)

 

 

Anyway, it seems to work for me, its an extra few mins work just to check on fired cases and the Wilson is easy to ajust to whicever calibre your'e loading.

 

Would be interested if anyone who doesn't trim but has chrony has experienced low ES....

 

 

Not sure at what point case lengths start to matter though (.001" / .003" / .005") differences in batches.

[Alycidon]

I also trim mine so that they all start the same length but I have to confess to not checking any for at least 4 or 5 loads each so I probably ought to again.

 

A

[onehole]

I think its just as important as every other little thing we do to our cases and our reloading prep /regime etc and to endeavour to get every reloaded round exactly the same as another and thats the best we can do.After that its down to the man and his gun.Personally on this particular question I work with plus or minus a thou and find I only have to keep an eye on things every half dozen or so firings with the cals I shoot however the first couple of firings need checking the most.onehole.

[Andrew]

The real reason you trim cases? SAFETY! A few thousandths of an inch difference between lengths of individual cases is nothing to worry about but a case that is a few thousandths too long can cause dangerous pressure spikes. Cases should be trimmed after every reloading without exception. That's why I like the Lee case trimmers. Once set, they are impossible to get out of wack and it only takes a light swipe after each reloading to assure they are the same length.

 

Of course, if you crimp your loads, trimming becomes more important with regard to accuracy due to crimping pressure/ location. Keep safe and trim often! ~Andrew

[Guest rogern]

Even if you are not interested in tack driving, you should ALWAYS trim, or at least check, your fired case length.

If the neck gets too long, and we are only talking thou's, you will effectivly pinch the neck onto the bullet, if you are loading to near max and that bullet is held back a millisecond too long you can end up with a very big bang, the consequences of which can be lethal !!!

 

If you are in any doubt look at the pressures for different loads in your manual, a millisecond or two could double them, BOOM!

 

Always check case length

[Alycidon]

I have now checked about 60 cases that I have ready for loading in 6mmPPC. Most are 1.503/1.504 but a few are shorter down to 1.497 amd about 8 or 10 are longer up to 1.508.

 

My Vit manual says a trim to length of 1.510 yet Speer show a trim to length of 1.493. I have asked another member who's chamber has probably been cut with the same reamer what he trims to, he will be back shortly no doubt. Anybody else any ideas?. I cannot remember trimming them in the past at all.

 

 

Here's another point, whilst having a look today at my RCBS Trimmer admitted it is a few years old I found it did not do any .20 cal cases. I see that RCBS now show a .20 pilot as a spare in the states though.

 

A

[Vermincinerator]

I trim all my cases to the same length as the shortest case out of the batch.

 

Ian.

[325WSM]

One normally trims to SAAMI spec less 10thou but 15 or even 20 thou will not be particularly detrimental for most applications. Uniformity is important and neck length in relation to the bullet being used is also a deciding factor in trimming. This may mean with a BT bullet that is extended well towards the lands the case will be trimmed after each firing but only back to max length to constantly provide the longest neck length for holding the bullet.

 

All new cases should be neck sized and then trimmed.

 

CHECK case length after every firing and trim regularly.

 

Over long cases cause more accidents and damaged rifles than every other aspect of home loading put together.

 

Case length is the single MOST IMPORTANT aspect of reloading so do not neglect it.

 

There are NO exceptions.