Case Trimming

[gcw6]

I'm new to reloading. I'm using a Dillon 550B to reload .223. Reloading manuals show the maximum case length. I know I need to trim my cases when they exceed the maximum case length, but can someone tell me why it is necessary to trim the case when it is only 1 or 2/1000 over the maximum length? When I seat the bullet, the oal will still be the same length whether I trim the case or not. I'm sure there must be a good reason for it, but I can't figure out what it is. Thanks for any input!

[Unclenick]

The chamber is cut out to accommodate a limited length of case neck. After that, it steps down nearer to bullet diameter. If you let the case get long enough, closing the bolt will jam the mouth against, and size it partly into that stepped down space. Then when the powder ignites it then can't open the neck up to let go of the bullet at the trapped mouth, and dangerously high pressures result.

Advice: Trim your cases to SAMMI minimum rather than maximum, then you can go through several reloads before they grow long enough to need trimming again.

Nick

[Smokey Joe]

Gcw6--Unclenick said it all. Unless you like KA-boom-ing yr favorite rifle, check yr case lengths, and shorten them down to the trim-to length when they stretch to the max length. You probably will not need to do it to any rifle case more than once in its life, if you neck-size only, and fire the case only in one rifle, and that rifle is a bolt-action.

Other than bolt guns usually require FL resizing, which works the brass more each time through, and tends to lengthen the brass quicker. (And shortens the case's life BTW.)

If you can get by with neck-sizing, yr brass lasts that much longer, and needs trimming that much less.

But when the brass needs trimming, DO IT!

[gcw6]

Thanks for the replies. That makes sense now that I think about it. I was going to resize the cases anyway, but I just didn't know the reason why, other than the reloading manuals stated to do it.
Gary

[Leftoverdj]

You can sometimes see when a case has been allowed to go untrimmed too long. It shows up as a bright spot on the case mouth where the brass has stretched enough on one side to press against the front of the chamber. It's worth keeping an eye out for during your case inspection. Some cases. even of the same lot, stretch a little faster than others, and few of us measure every case every loading. Should you spot that sign, it's time to trim that batch even if your sample cases are not at max length.

[kingudaroad]

I like to trim my rifle cartridges every time just to smooth out the case mouth. If you look real close you can find rough spots and little indentations right on the mouth.

That trimmer puts a nice shiny flat surface that with a little camfering and deburring makes it smooth again.

The extra time spent on my rifle cartridges is not that big a deal since I'm usually making 100 or less at a time.

[highrider_44s]

i was just wanderin if you can shoot the case one more time if it measures the max length after resizing it. I don't have a trimmer yet just wandering how soon i got to get one? :D

[Smokey Joe]

wanderin if you can shoot the case one more time if it measures the max length after resizing
If it's AT the max, then yes. If it's OVER the max, then, NO! That max lenght was established for a reason. That's why it's called the "MAXIMUM Case Length."

You really, really, don't want to be experimenting to see if you can get away with it in your particular rifle.

As my stockbroker would put it, that investment offers too little reward for too much risk.

[highrider_44s]

half of the cases are under but the other half measure 2.496 +/-.001 (max being 2.494 ) i'm guess that those ones might be risken it or will the be ok.

[Smokey Joe]

Highrider44s--Pls read my post above, again.

[highrider_44s]

yea sorry I get yea. I remeasured all them i think i ended up with 6 that are good guess i need a case trimmer sonner than i thought.

[grizz007]

highrider,

Being inexperienced is risky in reloading with all the doubts one is likely to encounter. You're correct by asking and not assuming and taking the high risk associated with neglect. Buy a case trimmer, there is a cheap one that Lee makes that ZIPs, heard alot of good about it if the dollars are really not handy. Someone here assuredly knows what particular model I am referring about. I trim new brass and resize and that gives about equal measurements for shooting for quite abit of reloading-on the average. If I was to do the Round Robin method as I am working to begin I am going to pay particular attention to all details. That is the fun part-grueling yes but well worth the joy of seeing your effort pay off with shots well placed. Continue in being studious. Continue in being safe. Have fun with reloading and always ask or read and reread until you get it. Most forums have a search file you can run thru, that helps alot as well. It does not stop - it is a disease and there is no cure-enjoy!:D

[Smokey Joe]

is the Lee Zip Trim, and it works slick! No motor, just pull the string like starting a lawnmower. Same kind of auto-rewind, in miniature. There are shellholders for each different size case, or if you do a lot of different sizes there is a universal holder. You also need the pilot for each cartridge that you do, also the cutter that holds the pilot; just one of those. I'd splurge and get the cutter with the wooden ball handle--it's a LOT easier to hold.

You can clamp the Zip Trimmer to yr tabletop, or there are screw slots to affix it permanently.

I got my Zip Trim @ a gun sho, that a dealer had used for a demo, so got a good deal on it. One occasionally does find such a bonanza @ a gun sho.

You can order direct from Lee Precision if you want, but I think any of the big mailorder houses, like Midway, would have a better price for you.

Lee's customer support is among the best, BTW. Doesn't matter if you bought it from them or elsewhere, contact them if you have a problem.

Look up the Zip Trim @ Lee's website, www.Leeprecision.com

Order it from Midway, www.Midwayusa.com

Oh, you'll also need an inside/outside chamfer tool for the case mouths. A handheld one isn't costly. Midway will have those too.

If you're not sure how to proceed, a FINE how-to book is The ABC's of Reloading which belongs on every reloader's bookshelf, well thumbed, IMHO. Put out by Krause Publishing, www.Krause.com if you can't find it @ yr local sptg gds sto, gun sho, or the I'net. It will cover max length, trimming, and about 8 zillion other important questions.