Trimming 7mm Rem Mag cases

TheNatureBoy · July 9, 2009, 07:13 PM

I load for a 7mm rem mag sendero. My question is how far back do you trim the brass? I have a good number of cases that are stretched (necks) and I'd like to reuse them before I move on to new ones. Appreciate any assistance you can provide. Thanks

gun44 · July 9, 2009, 07:52 PM

shows a trim length of 2.490 inches.

**Unclenick** · July 9, 2009, 07:56 PM

7 mm Remington Magnum has a SAAMI case length specification of 2.500" maximum and 2.480" minimum. The conventional strategy is to aim for the middle of that range, or 2.490", then trim again when the after-sizing length is found to exceed the maximum number.

The Lee trimmer at around $10 is the least expensive but also about the most foolproof way to trim them. Size them first, then trim.

djb_249 · July 10, 2009, 02:34 AM

Unclenick is absolutely right...the easiest way to make sure you have properly sized cases is to buy a lee trimmer. At least then you know you're right 100% of the time.

Blue · July 10, 2009, 02:53 AM

A very handy tool to have for reference is the Lyman E-Zee Case Length Guage. It is made of stainless steel and machined to Max case lengths case lengths as recommended by SAAMI. Handy to have on the bench.

If you will make a habit of looking in your manuals - the max case length and the trim to lengths are clearly listed. UncleNick has a good recommendation for trim to mid point between Min/max.

The Sendero is a fine weapon.

hardhit · July 10, 2009, 06:06 AM

Iv started using these they tell you the true length of his rifle's chamber when measuring from the bolt face to the end of the chamber's neck. This measurement will tell you how much excess case length your chamber may have over published trim lengths in reloading handbooks. I have reloaded 35/ 308 lapua cases 7 times and they are no were near the chamber length of my rifle. I would say that by the time I have to trim these cases they will have passed their use by date anyway, but i will be keeping an eye on the case lengths anyhow.

ForneyRider · July 10, 2009, 04:37 PM

I use the Lee trimmer for 7mm Mag and others.

It's fixed, fast and cheap.

I've been using the Lee collet (neck sizer) die and very little to trim after the initial trim.

flashhole · July 10, 2009, 05:48 PM

I too use the Lee Trimmer for the 7mm Rem Mag. It's foolproof and 100% repeatable. I would add that not all chambers are created equal and sometimes you get one on the short side. My 221 Fireball is like that and I ended up having to trim on the short side of the SAMMI spec. Not a big deal, I just had to shorten the end of my Lee tool. Fine emory paper worked great.

dardascastbullets · July 10, 2009, 10:21 PM

Hi Nature,

Your post is somewhat misleading. You mention that your cases are stretched (necks). How did you determine that only the necks are stretched? This is not possible as the webbing at the base is stretching also which can produce some very surprising results (case head separation). I would highly suggest that you obtain a dental pick. The dental pick is used to scrape lightly on the inside of the case down near the base to feel for a 'dip'. This 'dip' is the actual stretch of the case's base and if it is severe enough it will actually display itself on the outside of the case as a bright or dull ring just above the base portion.

Once the cases have been deemed usable, then trim them to the specifications given in your reloading manual. Make sure you chamfer both the inside and the outside of the necks to eliminate the burr(s).

Matt

TheNatureBoy · July 13, 2009, 05:00 AM

Thank you all for your replies. I've only been reloading for about 8-9 months and still learning.

Blue, before posting the question I consulted two manuals. Just wanted input from those of you who have doing this for a while. Thanks again

July 9, 2009, 07:13 PM	#1
TheNatureBoy Senior Member Join Date: September 6, 2007 Posts: 1,204	Trimming 7mm Rem Mag cases I load for a 7mm rem mag sendero. My question is how far back do you trim the brass? I have a good number of cases that are stretched (necks) and I'd like to reuse them before I move on to new ones. Appreciate any assistance you can provide. Thanks

July 9, 2009, 07:52 PM	#2
gun44 Senior Member Join Date: August 17, 2007 Location: Georgia Posts: 125	RCBS and my Hodgdon manual............. shows a trim length of 2.490 inches.

July 9, 2009, 07:56 PM	#3
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,060	7 mm Remington Magnum has a SAAMI case length specification of 2.500" maximum and 2.480" minimum. The conventional strategy is to aim for the middle of that range, or 2.490", then trim again when the after-sizing length is found to exceed the maximum number. The Lee trimmer at around $10 is the least expensive but also about the most foolproof way to trim them. Size them first, then trim. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

July 10, 2009, 02:53 AM	#5
Blue Senior Member Join Date: June 6, 2009 Posts: 113	Case Length A very handy tool to have for reference is the Lyman E-Zee Case Length Guage. It is made of stainless steel and machined to Max case lengths case lengths as recommended by SAAMI. Handy to have on the bench. If you will make a habit of looking in your manuals - the max case length and the trim to lengths are clearly listed. UncleNick has a good recommendation for trim to mid point between Min/max. The Sendero is a fine weapon.

July 10, 2009, 04:37 PM	#7
ForneyRider Senior Member Join Date: December 4, 2007 Location: Forney, TX Posts: 725	I use the Lee trimmer for 7mm Mag and others. It's fixed, fast and cheap. I've been using the Lee collet (neck sizer) die and very little to trim after the initial trim. __________________ When all is said and done, there is a lot more said than done.

July 10, 2009, 02:34 AM	#4
djb_249 Member Join Date: June 10, 2009 Posts: 24	Unclenick is absolutely right...the easiest way to make sure you have properly sized cases is to buy a lee trimmer. At least then you know you're right 100% of the time.

July 10, 2009, 05:48 PM	#8
flashhole Senior Member Join Date: February 9, 2005 Location: Owego, NY Posts: 2,000	I too use the Lee Trimmer for the 7mm Rem Mag. It's foolproof and 100% repeatable. I would add that not all chambers are created equal and sometimes you get one on the short side. My 221 Fireball is like that and I ended up having to trim on the short side of the SAMMI spec. Not a big deal, I just had to shorten the end of my Lee tool. Fine emory paper worked great. __________________ ,,, stupidity comes to some people very easily. 8/22/2017 my wife in a discussion about Liberals. Are you ready for civil war?

July 10, 2009, 10:21 PM	#9
dardascastbullets Senior Member Join Date: July 20, 2008 Location: Essexville, MI Posts: 164	Hi Nature, Your post is somewhat misleading. You mention that your cases are stretched (necks). How did you determine that only the necks are stretched? This is not possible as the webbing at the base is stretching also which can produce some very surprising results (case head separation). I would highly suggest that you obtain a dental pick. The dental pick is used to scrape lightly on the inside of the case down near the base to feel for a 'dip'. This 'dip' is the actual stretch of the case's base and if it is severe enough it will actually display itself on the outside of the case as a bright or dull ring just above the base portion. Once the cases have been deemed usable, then trim them to the specifications given in your reloading manual. Make sure you chamfer both the inside and the outside of the necks to eliminate the burr(s). Matt __________________ Matt Dardas

July 13, 2009, 05:00 AM	#10
TheNatureBoy Senior Member Join Date: September 6, 2007 Posts: 1,204	Thank you all for your replies. I've only been reloading for about 8-9 months and still learning. Blue, before posting the question I consulted two manuals. Just wanted input from those of you who have doing this for a while. Thanks again