How far back to you trim your cases?
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#1: How far back to you trim your cases? Author: slimjim, Location: Fort Worth TX PostPosted: Sat Jun 16, 2012 2:42 pm
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Got myself some .270 Win full-length resizing dies and case trimmer after neck sizing only for 3 years. Ran a bunch of cases through the FL die. They all "grew" to be longer than max case length which is 2.540" for the .270. So I trimmed them all back to 2.525" - an easy number for me to remember and thought I'd leave enough room so I didn't have to trim them all the time. Well, now that I have fired them, they all "shrunk" and are shorter than 2.525". Didn't see that one coming.

What dimension would you have recommended I trim my cases to?
#2: Re: How far back to you trim your cases? Author: Ominivision1, Location: Iowa PostPosted: Sat Jun 16, 2012 3:26 pm
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All my books show a trim to length at 2.530" for the 270win. When I do need to trim bottle neck cases, I try to stay in the middle between max and min.
#3: Re: How far back to you trim your cases? Author: Donut Slayer, Location: Pensacola, Florida PostPosted: Sat Jun 16, 2012 3:54 pm
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I use a Lee case trimmer, so I dont have to measure.
#4: Re: How far back to you trim your cases? Author: Gil Martin, Location: Schnecksville, PA PostPosted: Sat Jun 16, 2012 4:00 pm
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Another vote for the Lee case trimmers. I resize the cases and when the Lee trimmer stop cutting brass, I chamfer and debur the cases and load them. All the best...
Gil
#5: Re: How far back to you trim your cases? Author: Grumulkin, Location: Central Ohio PostPosted: Sat Jun 16, 2012 4:43 pm
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Fired cases will always be shorter than when they started out. When you resize them, they will lengthen again.

If you've shot these cases a number of times, be sure to check for incipient case head separations. When you have to trim cases, it means the brass is thinning above the web which, when progressed far enough, will result in a head separation.
#6: Re: How far back to you trim your cases? Author: PaulS, Location: South-Eastern Washington - the State PostPosted: Sat Jun 16, 2012 6:50 pm
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I keep mine trimmed to minimum dimensions. It is the step in the reloading process right after sizing and decapping. While I have it in my hand I can inspect it for flaws.
#7: Re: How far back to you trim your cases? Author: Pumpkinslinger, Location: NC foothills PostPosted: Sat Jun 16, 2012 7:35 pm
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The "trim to" length always works for me.
#8: Re: How far back to you trim your cases? Author: Bushmaster, Location: Ava, Missouri PostPosted: Sun Jun 17, 2012 7:16 am
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I only have .30-30 and .30-06 rifle cases to trim. I trim the .30-30 cases to insure an even crimp on all loads. The .30-06 cases to min.

All straight wall revolver cases I also trim to insure the same crimp on all. Hell...I even trim .45 ACP cases to .890" +/- .001 because my Colt 1911 prefers them at .890"
#9: Re: How far back to you trim your cases? Author: 1895ss, Location: Not Here...!! PostPosted: Sun Jun 17, 2012 10:37 am
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I always trim to minimum length when trimming is nec.
#10: Re: How far back to you trim your cases? Author: chambered221, Location: Lost for good !!! PostPosted: Sun Jun 17, 2012 10:38 am
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Standard trim length is .010 under max length !!!

You probably re-sized the case more than what was needed.

This will typically happen with excessive sizing of the body..... sometimes it's just the way the die is made other times because you've set the shoulder back more than what is need for your chamber.

Keep in mind you shrunk the diameter of the case and lengthened it with the re-sizing die, upon firing the opposite occurs !!!
#11: Re: How far back to you trim your cases? Author: Elvis, Location: south island New Zealand PostPosted: Sun Jun 17, 2012 3:51 pm
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Gil Martin wrote:
Another vote for the Lee case trimmers. I resize the cases and when the Lee trimmer stop cutting brass, I chamfer and debur the cases and load them. All the best...
Gil
me too its easy peasy to do and takes no time at all especially if you use the cordless drill Very Happy
#12: Re: How far back to you trim your cases? Author: slimjim, Location: Fort Worth TX PostPosted: Sun Jun 17, 2012 3:54 pm
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I've got a bunch of brass fired from a different rifle. I'm going to FL resize then neck size after that. Think I'll trim to 0.005" after the FL then shift back to 0.010" long term.

Thanks for the inputs!
#13: Re: How far back to you trim your cases? Author: Dawgdad, Location: On the Prairie PostPosted: Sun Jun 17, 2012 6:43 pm
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Well - now that you are into FL resizing... Look at the X-dies from RCBS. trim it once.

I can visualize what happens to brass during firing if I imagine the case as a watter balloon. When you squeeze it into the sizing die it gets longer like grabbing a water balloon in the middle. When you fire the case it expands to fill the chamber which means it has to get shorter to get fatter.

always measure for trimiing after sizing.
#14: Re: How far back to you trim your cases? Author: fnuser, Location: S.W. Missouri, U.S.A. PostPosted: Mon Jun 18, 2012 5:53 pm
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I do it like Omni does, because A, they worked at the last fired length. B, anything shorter then the trim to length leaves less neck to fill the chamber, and gives the chamber neck more opportunity to wiggle or let the bullet yaw before entering throat region.
#15: Re: How far back to you trim your cases? Author: wncchester,  PostPosted: Tue Jun 19, 2012 6:32 pm
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"Standard trim length is .010 under max length !!!" Very Happy

True. And that's just a practical arbitrary amount without any 'specification' about it. We can trim to any lenght under max we wish, nothing will blow up if we cut back 50 thou. Laughing
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