Trimming Brass

Malazan

Malazan

New member
I'm confused about when this needs to be done.

I'm loading for a .204

I measure my once fired cases, they measure 1.850 to 1.852

In sierras loading manual it says trim-to-length 1.840

Does that mean you trim the cases to 1.840?

How do you know when cases need to be trimmed? i.e. At What Length would you trim them?
 
1.850 would be max length, using your info. I haven't checked the books myself, for this cal, but "trim to" is usually .010 under max length. Yours that measure 1.852 are .002 over max. Trim back to between 1.840 and 1.850 - after resizing (brass sometimes stretches during the re-sizing process)
Mark
 
If you let the case exceed maximum length it can spike pressure,what happens is when you close the bolt it will actually crimp the case neck causing more pressure.
 
Originally Posted By: timberwolfIf you let the case exceed maximum length it can spike pressure,what happens is when you close the bolt it will actually crimp the case neck causing more pressure.

Exactly. The neck of the brass gets "jammed" into the throat of the chamber, crimping down excessively on the bullet. The harder it is for the bullet to escape, and the longer it takes, the more pressures rise.

Keep your case lengths to within .010 of published "trim length" and you should be fine.
 
I have my .204 trimmer set for 1.838", stretching during the full length resizing is normal for me, so I won't have to worry about excessive length...This usually allows me to shoot and reload several times before there is any point where the brass exceeds the 1.85" length...

I use Forster Benchrest dies and they are made to pretty tight specifications and the expander ball on the shaft, coupled with the dimension of the external size of the neck will tend to compress the case neck to the proper size...This cuts down on the degree of runout, as well as providing a consistent neck tension for the bullet..

I load for an AR as well as a bolt action and can get by with neck sizing for the bolt action, but need to FL size every time for the AR..
 
For factory guns you shouldn't have to trim brass at all because they all have long throats. Basically to dummy-proof the gun for reloaders. As long as you keep brass .010 under throat length you will be fine. Most important thing for accuracy is to make sure that all are trimmed to same length. I have never had new brass that I could trim to the recommended length in reloading manuals because they are too short to start with.
 
There's more nonsense posted about case trimming than just about anything else. At .002" over new spec., your brass doesn't need trimming. Ignore "trim-to" length. Brass doesn't need trimming until it gets near chamber length, and your chamber is a whole bunch longer than that. Want to find out, get a chamber length plug from Sinclair's and see for yourself. What you'll find is that your chamber length is very much longer than brass. So much longer that brass will probably never need trimming before it's time for replacement.
 
Originally Posted By: AckmanThere's more nonsense posted about case trimming than just about anything else. At .002" over new spec., your brass doesn't need trimming. Ignore "trim-to" length. Brass doesn't need trimming until it gets near chamber length, and your chamber is a whole bunch longer than that. Want to find out, get a chamber length plug from Sinclair's and see for yourself. What you'll find is that your chamber length is very much longer than brass. So much longer that brass will probably never need trimming before it's time for replacement.



I beleive what you are saying Ack. This past summer I just picked up a nice custom mauser in 308. I didn't trim brass, I didn't measure brass. The brass did get so long I couldn't chamber the round. The brass is now trimmed and works just fine. Just my addition.
 
I always trim my brass after shooting them. after i resize the brass i trim them down to what the min is. sometimes the brass stretches out and sometimes it doesnt. i like to keep all my brass the same size.
 
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