Case Trim length

257 · December 7, 2009, 02:39 AM

What happens if you trim a case too short? For example, lets say the book says OAL should be 2.5 and your trim back length would be 2.490. What happens if it is say 2.450 or 2.440? Would this cause any safety issue's? I can't see why it would be a problem? BTW, this has nothing at all to do with me operating a trimmer or screwing up somewhere along the line. The reason I ask is because I shoot a 257 weatherby and I love the round, but their brass is ridiculous

so, i ran a few 264 win mag cases through my sizing die loaded it light and shot one. No problems that i could see.

but the Win. case length is about .050 shorter than the weatherby. If it matters i chose the win mag because they are nearly the same size and my brother had a few once fired empties handy at the right price.

Randy 1911 · December 7, 2009, 02:49 AM

They would not crimp correctly, meaning no crimp. If you readjust the crimp die for what ever length the case is, all would be fine, but it would only work for that length case. You would need to readjust it again for the regular cases. Might be a PITA.

gearheadpyro · December 7, 2009, 04:06 PM

Using short cases will change where you need to set the crimp die, and in something like a Lee factory crimp die is may render a crimp impossible. Other side effects I can see is less of the bullet in the case. This will result in reduced neck tension and may change the powder charge that shoots best in your gun.

As long as there is enough bullet in the cartridge, and it seems to shoot ok, I would give it a go. It may stretch out far enough eventually to be the same length as factory brass. I would however treat that brass like a totally different lot, and would do another load development for that brass. You might come back to the same load, but I would work it up again just to be sure.

reloader28 · December 8, 2009, 10:53 AM

I wouldnt worry at all. I got a bunch of brass from a friend of mine once that he had trimmed and some were really short. They all worked perfectly fine.
I also dont crimp any rifle bullets so that wasn't a problem.
After a couple full length sizes they will be the right length.

Slamfire · December 8, 2009, 05:53 PM

Long is bad. When the neck get pinched in the throat, pressures climb.

If the case has been trimmed so short that it won't hold a bullet in the neck, that is bad.

I trim cases to minimum, or more, and never had any issues, function, accuracy or otherwise.

The back of the case provides the gas seal. The front just holds in the bullet in the chamber.

Hummer70 · December 9, 2009, 06:24 PM

The only thing I ever crimp is 357 and 44 Mag pistol bullets. I never crimp rifle bullets.
Alot of high power shooters trim their cases about .015" under spec so they can size several times before trimming again.
The stated trim lengths have a built in safety factor but I figured out a better trim gage on the barrels I fit up. I take a section of barrel about an inch long and run the finisher reamer in to where it stops about 1/8" before it comes out the other end. Then I face off the other end leaving just a bit of the throat left. Like a little shelf.
If you place a fired or sized case in this "gage" you will see exactly where your neck is in relation to the end of the chamber. I always see about .010" or more clearance of the neck in these gages trimmed to recommended length. I just toss the barrel section in the die box and I have a true trim length gage.

December 7, 2009, 02:39 AM	#1
257 Member Join Date: November 21, 2009 Location: SW PA Posts: 26	Case Trim length What happens if you trim a case too short? For example, lets say the book says OAL should be 2.5 and your trim back length would be 2.490. What happens if it is say 2.450 or 2.440? Would this cause any safety issue's? I can't see why it would be a problem? BTW, this has nothing at all to do with me operating a trimmer or screwing up somewhere along the line. The reason I ask is because I shoot a 257 weatherby and I love the round, but their brass is ridiculous so, i ran a few 264 win mag cases through my sizing die loaded it light and shot one. No problems that i could see. but the Win. case length is about .050 shorter than the weatherby. If it matters i chose the win mag because they are nearly the same size and my brother had a few once fired empties handy at the right price.

December 7, 2009, 02:49 AM	#2
Randy 1911 Senior Member Join Date: May 7, 2009 Location: Western Arkansas Posts: 273	They would not crimp correctly, meaning no crimp. If you readjust the crimp die for what ever length the case is, all would be fine, but it would only work for that length case. You would need to readjust it again for the regular cases. Might be a PITA. __________________ Been Reloading 27 Years NRA Member Member Old Fort Gun Club www.ofgc.org

December 7, 2009, 04:06 PM	#3
gearheadpyro Senior Member Join Date: September 3, 2009 Location: Charleston, SC Posts: 169	Using short cases will change where you need to set the crimp die, and in something like a Lee factory crimp die is may render a crimp impossible. Other side effects I can see is less of the bullet in the case. This will result in reduced neck tension and may change the powder charge that shoots best in your gun. As long as there is enough bullet in the cartridge, and it seems to shoot ok, I would give it a go. It may stretch out far enough eventually to be the same length as factory brass. I would however treat that brass like a totally different lot, and would do another load development for that brass. You might come back to the same load, but I would work it up again just to be sure. __________________ www.southernmarksman.com Owner of & Chief Instructor for The Southern Marksman, LLC NRA Life Member, NRA CRSO, Multi-Discipline NRA Certified Instructor

December 8, 2009, 10:53 AM	#4
reloader28 Senior Member Join Date: October 13, 2009 Location: nw wyoming Posts: 1,061	I wouldnt worry at all. I got a bunch of brass from a friend of mine once that he had trimmed and some were really short. They all worked perfectly fine. I also dont crimp any rifle bullets so that wasn't a problem. After a couple full length sizes they will be the right length.

December 8, 2009, 05:53 PM	#5
Slamfire Senior Member Join Date: May 27, 2007 Posts: 5,261	Long is bad. When the neck get pinched in the throat, pressures climb. If the case has been trimmed so short that it won't hold a bullet in the neck, that is bad. I trim cases to minimum, or more, and never had any issues, function, accuracy or otherwise. The back of the case provides the gas seal. The front just holds in the bullet in the chamber.

December 9, 2009, 06:24 PM	#6
Hummer70 Senior Member Join Date: June 22, 2009 Location: South Carolina Posts: 203	The only thing I ever crimp is 357 and 44 Mag pistol bullets. I never crimp rifle bullets. Alot of high power shooters trim their cases about .015" under spec so they can size several times before trimming again. The stated trim lengths have a built in safety factor but I figured out a better trim gage on the barrels I fit up. I take a section of barrel about an inch long and run the finisher reamer in to where it stops about 1/8" before it comes out the other end. Then I face off the other end leaving just a bit of the throat left. Like a little shelf. If you place a fired or sized case in this "gage" you will see exactly where your neck is in relation to the end of the chamber. I always see about .010" or more clearance of the neck in these gages trimmed to recommended length. I just toss the barrel section in the die box and I have a true trim length gage.