Case trimming and caliper questions by a novice

torquimata

January 17, 2006 13:16

Thanks for all the wonderful feedback on my first reloading setup for my son and me. I am unclear about how,why, when I need to "trim" cases and what the calipers are used for. I imagine the calipers tell me overall length? How many times can we reload a single case or how do I know when it needs to be trimmed and how far to trim it?

Sorry if these questions seem so basic but I'm trying to get it right the first time around. I also heard that Remington brass is preferable to Winchester brass.

Thanks for any and all input, I don't know who's going to be more excited starting to reload-my son or me!

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  B17-P51

  January 17, 2006 14:23

  As the brass is used each time the cases tend to get bigger or stretch. Unfortunatly the brass that causes the cases to get longer comes from somewhere, usually the area just forward of the web or the part of the case just in front of the flash hole,about 3/16" from the rim. How much depends on the load you shoot and how much you size the case, Full length or just neck size. Usually neck sizing fired cases is ok as long as they are going back into the same rifle, preferably a bolt action. Eventually these will have to be full length sized and trimmed to the proper length. Example .243 Winchester---- Max length 2.045- Trim to length 2.035. Hence the calipers are needed to measure this.. dont worry too much about trimming just yet. if you keep the loads mild, probably about the 3rd or 4th time they may be ready.EVENTUALLY THEY WILL BE JUNK AND MUST BE DISCARDED! They will seperate and become dangerous to shoot! This is exlained very well in any of the loading manuals. Keep asking questions!! Hope this helps. Jake

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  Pinhead

  January 17, 2006 14:32

  torquimata, first thing you need to do is buy a good manual and do some reading. Hornady, Speer, Lyman, Nosler, Speer are all good ones to start you reloading. All the abovce manual will tell you the maximum and minimum lengths of the different cartridges and the trim to length. A caliper will tell you the length of the cases you are going to load. Measure each case individually as each will lengthen at different rates. This(when checked against the info in the manual) will tell you when each case needs to be trimmed. There are too many variable to be able to set a rule as to how many times a case can be reloaded or how many times it can be fired before trimming. By the way, welcome to the forum. I consider reloading every bit as much of a hobby as shooting. Jim

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  JustC

  January 18, 2006 07:17

  "The Quick and Dirty"
  - the chamber has an overall length before the start of the rifling
  - the case also has an overall length
  - if the case grows too long, it will contact the front of the chamber (leade) and a crimp will occur at the case-mouth when closing the bolt
  - this crimp can cause excessive pressure spikes and damage can result to gun and shooter
  
  - as a side note, the amount of growth also allows you to keep track of when to discard the cases due to an impending case-head seperation from the growth thinning the case walls.
  
  the books will go into more detail, but that is the "Q&D"[;)]
  
  and YES, the calipers measure from casehead to case mouth overall length. It will grow by .001"s each firing and excessive growth needs to be kept an eye on, as seperation will occur in much fewer rounds.

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