Author Topic: To trim or not to trim . . . (Read 797 times)

longwinters · « **on:** April 21, 2003, 11:59:59 AM »

I am just getting into reloading but I see in my reading that sometimes brass needs to be trimmed to stay under c.o.l Can't some of this be taken care of by how deep you seat the bullet? I know this would not be a cure all, but after one shot my brass (7mm) is over the measurement given in my Spear book by something like .003. I am surprized that I would have to trim after only one shot with new ammo. (This is new factory bullets that I have shot, not just new brass).

BruceP · « **Reply #1 on:** April 21, 2003, 02:07:03 PM »

Seating the bullet deeper wont help if the case is to long. The problem with a case thats to long in not the OAL of the cartridge but the case itself. If the case is to long the case mouth will jam into the throat of your chamber. If the round will chamber at all it will run up the presures because it will not release the bullet properly. Are your once fired cases .003" longer than the listed max. length or the trim to length? If its over the trim length by .003" you will be fine. If its over the max length you need to trim the brass. If you dont want to spend the money on a case trimmer like the Forster or the RCBS then Lee makes an inexpensive trimmer that consists of a cutter, case length gage, shellholder and lock stud. This method is slower and harder on the hands but is works. You will also need a chamfer deburrng tool. You can get what you need from Midway for about $10, but they add a charge to orders under $20 so go ahead and get something else you need to top off your order. No sense in giving them free money and getting nothing in return. If you dont have one you might consider a Lee Auto Prime hand priming tool and the proper shellholder for a little over $11 and the lee primer pocket cleaner for about 2 bucks. While I do not beleive all of the Lee products are as good as some other brands I have all of these products and they do a good job. The priming tool while inexpensive is the best one on the market IMHO. I will be ordering a second one in the next week, so I wont have to change mine back and forth from small to large primers. I'll leave one set up for each.
BruceP

savageT · « **Reply #2 on:** April 21, 2003, 04:09:44 PM »

Quote from: longwinters

I am just getting into reloading but I see in my reading that sometimes brass needs to be trimmed to stay under c.o.l Can't some of this be taken care of by how deep you seat the bullet? I know this would not be a cure all, but after one shot my brass (7mm) is over the measurement given in my Spear book by something like .003. I am surprized that I would have to trim after only one shot with new ammo. (This is new factory bullets that I have shot, not just new brass).

longwinters,
The problem is not so much O.A.L. as it is the bottle-neck shoulder position. That determines head-spacing of the shell to the chamber.

Jim

sharpshooter · « **Reply #3 on:** April 21, 2003, 07:00:28 PM »

Its hard to believe that you are trimming after your first use with your new brass. I use the Winchester brass (new) and it always measures a couple of thousands short from what it should be and I usely will get a couple of rounds off before I have to trim. I also shoot a 7mm. I measure all my brass after I size it and find which case is the shortess and I will trim them all to this length and then I will remeasure them after they are shot and go from there. I hope this makes sense to you. What kind of gun are you shooting?Bolt action? Encore? or something else? :gun4:

BruceP · « **Reply #4 on:** April 22, 2003, 04:56:31 AM »

Another thought, did you resized the case before measuring it. If you did you may not have lubed the inside of the case neck. This can cause the case to drag on the expander and it can stretch the case.
BruceP

longwinters · « **Reply #5 on:** April 22, 2003, 11:42:56 AM »

I am shooting a Sako 7mm in stainless, bolt action. I did not lube the inside of the neck (only the outside of the case). I did not have any difficulty when resizing the neck. Not that I have ever felt how much pull there would be, but there was no difficulty. Now that I think of it . . . I have some other brass that I shot at the same time (same manuf. etc...) and I did not measure that brass. I will go do that and see if not lubing the inside of the neck made a difference. thanks guys.

KN · « **Reply #6 on:** April 22, 2003, 12:15:19 PM »

Most of my New brass has to be trimmed after the first firing. That is when it will probably streach the most. After that I usually get about 3 more firings before trimming. This is with full length sizing, not neck sizing. If you neck size only you will probably get more firings than that. KN

IronKnees · « **Reply #7 on:** April 23, 2003, 02:26:15 AM »

Just about everything has already been said but I do want to add just a bit. Again, the OAL (COL) is not the problem. If a case neck is too long, and not trimmed, and you chamber the round, the case mouth will jam into the throat of the rifle, and can crimp or squeeze the bullet so hard as to cause considerable pressure problems.
My personal procedure is to trim, chamfer and de-burr after every firing. I use the Lee cutter / trimmers

which work very well and are EXTREMELY accurate, and usually only shave a very small amount of metal, and sometimes none at all, but sometimes there is considerable lengthening, and by doing this, I KNOW that I will not be running into problems, and that ALL of my loads are consistent...
IMHO... go ahead and trim each time to be safe, and to have the best possible loads...

longwinters · « **Reply #8 on:** April 23, 2003, 11:41:44 AM »

Thanks for the good information guys. I did measure my non-resized brass and the measurement was identical to the brass that I neck sized. I also read in my Speer book that the OAL/COL measurement is the minumum length (to be safe for all rifles etc). They state that the brass length should be 64.52mm. Mine is 65.02.