Trim To Length Question

Roland Thunder · September 2, 2011, 10:28 PM

My Lyman 49th manual says that the trim to length for a .45 ACP cartridge is .888. However, the drawing shows it to be .898.

Which is correct?
I have several used cases that have been fired once that measure .885. Are these too short and need to be thrown out?

Rifletom · September 2, 2011, 10:36 PM

No. You are good to go. Just make sure that your OAL is good for your gun[for feeding].

engineermike · September 2, 2011, 10:49 PM

The .898 is the SAAMI length, and the .888 is the length that case was trimmed to when the bullet was tested for the load data and the .885 is the length of the case you picked up. I am not sure if the case shrinks when it is fired for the first time or whether the factory that made the bullet the first time trimmed the case to that length but as rifletom says "you're good to go" just keep your C.O.L. within specs. All of my 9mm, S&W 40's, and 38 specials are all shorter than the case trim length shown in the load manuals I have and they all work just fine.

Roland Thunder · September 3, 2011, 05:27 AM

How much tolerance should be allowed? That is how much is too short or how much can you deviate from the SAAMI length. Same with OAL, how close due you have to be to the OAL of 1.275 stated in the load book

Bailey Boat · September 3, 2011, 07:17 AM

Bear in mind that the 45 ACP (in a semi auto) headspaces on the case mouth. Too short and the round may misfire, too long and it won't allow the slide to fully go into battery. You need to determine what your gun "likes". The measurement from the manual is usually correct and thats what I use 99.9% of the time.
If the rounds are going into a revolver using clips then you have more leeway since the headspace is now transferred to the rim.

m&p45acp10+1 · September 3, 2011, 07:43 AM

In over a year and half, I have as of yet in well over 40k rounds of .45 acp had to trim a single piece of brass. Very few reloaders will trim pistol brass. Those that do usualy load for revolver, and trim to a uniform length for crimping purpouses.

JimPage · September 3, 2011, 08:11 AM

Staight wall cases don't lengthen like bottle neck cases do. It's unusual to have to trim straight wall cases. Bullet seating is not an issue if you taper crimp.

CherokeeT · September 3, 2011, 01:03 PM

Been reloading 45 ACP since late '50's, never had a case too long or too short in the many thousands reloaded. Never trimmed any. 45 ACP caes do not seem to grow longer with use. YMMV

rodfac · September 16, 2011, 06:32 AM

Ditto on never having had to trim .45 ACP. Seems like the long out of print NRA book, "Handloading" had a good discussion on uniform head space and its effect on accuracy in the .45 ACP. Rod

Gary Wells · September 16, 2011, 06:51 AM

In my experience, .45 auto cases will continue to shorten as they continue to go through the clean, load, & shoot cycle. If you trim them, you are just shortening your case life expectancy.

Walkalong · September 18, 2011, 08:47 AM

I have never trimmed a .45 ACP case over many years and tens of thousands of rounds.

zfk55 · September 18, 2011, 08:57 AM

Bailey Boat, how does a short case misfire?

Walkalong · September 18, 2011, 02:22 PM

If the case is too short, and the bullet does not contact the rifling holding the case back, and the extractor doesn't hold the case back, it can go forward enough that the firing pin cannot set the primer off.

September 2, 2011, 10:28 PM	#1
Roland Thunder Senior Member Join Date: December 29, 2010 Location: Gwinnett County Georgia Posts: 1,136	Trim To Length Question My Lyman 49th manual says that the trim to length for a .45 ACP cartridge is .888. However, the drawing shows it to be .898. Which is correct? I have several used cases that have been fired once that measure .885. Are these too short and need to be thrown out? __________________ Do not follow where the path may lead, go, instead where there is no path and leave a trail - Ralph Waldo Emerson

September 3, 2011, 05:27 AM	#4
Roland Thunder Senior Member Join Date: December 29, 2010 Location: Gwinnett County Georgia Posts: 1,136	How much tolerance should be allowed? That is how much is too short or how much can you deviate from the SAAMI length. Same with OAL, how close due you have to be to the OAL of 1.275 stated in the load book __________________ Do not follow where the path may lead, go, instead where there is no path and leave a trail - Ralph Waldo Emerson

September 3, 2011, 07:43 AM	#6
m&p45acp10+1 Senior Member Join Date: May 3, 2009 Location: Central Texas Posts: 3,930	In over a year and half, I have as of yet in well over 40k rounds of .45 acp had to trim a single piece of brass. Very few reloaders will trim pistol brass. Those that do usualy load for revolver, and trim to a uniform length for crimping purpouses. __________________ No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.

September 3, 2011, 01:03 PM	#8
CherokeeT Senior Member Join Date: April 23, 2008 Location: Medina, Ohio Posts: 273	Been reloading 45 ACP since late '50's, never had a case too long or too short in the many thousands reloaded. Never trimmed any. 45 ACP caes do not seem to grow longer with use. YMMV __________________ God Bless America US Army, NRA Endowment TSRA Life, SASS

September 16, 2011, 06:32 AM	#9
rodfac Senior Member Join Date: January 22, 2005 Location: Kentucky Posts: 3,623	Ditto on never having had to trim .45 ACP. Seems like the long out of print NRA book, "Handloading" had a good discussion on uniform head space and its effect on accuracy in the .45 ACP. Rod __________________ Cherish our flag, honor it, defend it in word and deed, or get the hell out. Our Bill of Rights has been paid for by heros in uniform and shall not be diluted by misguided governmental social experiments. We owe this to our children, anything less is cowardice. USAF FAC, 5th Spl Forces, Vietnam Vet '69-'73.

September 2, 2011, 10:36 PM	#2
Rifletom Senior Member Join Date: February 11, 2011 Location: So-Cal Posts: 786	No. You are good to go. Just make sure that your OAL is good for your gun[for feeding].

September 2, 2011, 10:49 PM	#3
engineermike Junior member Join Date: March 14, 2010 Location: Oklahaoma City Posts: 538	The .898 is the SAAMI length, and the .888 is the length that case was trimmed to when the bullet was tested for the load data and the .885 is the length of the case you picked up. I am not sure if the case shrinks when it is fired for the first time or whether the factory that made the bullet the first time trimmed the case to that length but as rifletom says "you're good to go" just keep your C.O.L. within specs. All of my 9mm, S&W 40's, and 38 specials are all shorter than the case trim length shown in the load manuals I have and they all work just fine.

September 3, 2011, 07:17 AM	#5
Bailey Boat Junior member Join Date: December 10, 2006 Location: NC Posts: 365	Bear in mind that the 45 ACP (in a semi auto) headspaces on the case mouth. Too short and the round may misfire, too long and it won't allow the slide to fully go into battery. You need to determine what your gun "likes". The measurement from the manual is usually correct and thats what I use 99.9% of the time. If the rounds are going into a revolver using clips then you have more leeway since the headspace is now transferred to the rim.

September 3, 2011, 08:11 AM	#7
JimPage Senior Member Join Date: February 21, 2010 Location: Rome, NY Posts: 941	Staight wall cases don't lengthen like bottle neck cases do. It's unusual to have to trim straight wall cases. Bullet seating is not an issue if you taper crimp.

September 16, 2011, 06:51 AM	#10
Gary Wells Senior Member Join Date: August 22, 2009 Posts: 180	In my experience, .45 auto cases will continue to shorten as they continue to go through the clean, load, & shoot cycle. If you trim them, you are just shortening your case life expectancy.

September 18, 2011, 08:47 AM	#11
Walkalong Senior Member Join Date: May 30, 2007 Location: Al. Posts: 196	I have never trimmed a .45 ACP case over many years and tens of thousands of rounds.

September 18, 2011, 08:57 AM	#12
zfk55 Senior Member Join Date: December 24, 2009 Location: Lost Prairie Montana Posts: 391	Bailey Boat, how does a short case misfire? __________________ www.swissproductsllc.com An'' ole' Brer' Rabbit, he set in de bushes, he watch an' he wait, lay low an' he don' say nuffin'

September 18, 2011, 02:22 PM	#13
Walkalong Senior Member Join Date: May 30, 2007 Location: Al. Posts: 196	If the case is too short, and the bullet does not contact the rifling holding the case back, and the extractor doesn't hold the case back, it can go forward enough that the firing pin cannot set the primer off.