Would you trim this brass?

[Jody Simcox]

2x fired Lapua brass in 270 WSM...68 gr MagPro (max is 69-69.5) and 140 gr Accubond...sized brass now measures 2.075-2.091...SAAMI max says 2.100”...trim? To what length? Thanks

hunting rifle, but I also shoot steel to 800- certainly competing with the guys I shoot with

 

[rsmithsr50]

no, but get a Sinclair tool and you will know your chambers actual neck length and know when to trim

 

[gunsandgunsmithing]

First, know the actual length of YOUR chamber. This is a good and inexpensive way to measure it.

https://www.sinclairintl.com/reload...s/sinclair-chamber-length-gage-prod32925.aspx

Once you know this length, a good rule of thumb is never let your brass get within .010 of that length. So, if your ACTUAL chamber length is 2.100, max case length would be 2.090 and trim to length 2.080.

You can crowd those numbers a bit but there's no real advantage and the downside is huge, ie, dangerously high pressures. Just knowing the actual chamber length will let you know your trim to and your max lengths...rather than trusting a nominal spec or even a reamer print. If you look at a print, most have a .005" tolerance for length. Most chambers will fudge to the long side for safety reasons so, while a .020 short of actual may sound like too much clearance to some, it may well be much better than what you have now and you'll know.

FWIW, your variation in measured brass is pretty wide. Based solely on your stated saami spec, I'd at least uniform them to .005 shorter than your shortest case. But once you know the actual length, you may decide to adjust that a few thou either way. Likely toward the longer end of the spectrum.

The key is to know the actual chamber length. I don't want to let it get within .005 of that, at absolute max. Again, knowing the actual number will allow you to judge how close you are willing to let it get to that length rather than any nominal dimension stated in a book or even a print.

 

[gunsandgunsmithing]

no, but get a Sinclair tool and you will know your chambers actual neck length and know when to trim

Yep...Ya beat me to it. I posted a link. It's amazing how many people are unaware of such a critical little tool.

 

[ShootDots]

I shoot a .300 WSM and I trim my brass to 2.090. I will let it grow to about 2.093-4>>>>then it gets trimmed back. The .270 and .300 WSMs are the same case outside of the caliber.

 

[T-shooter]

I use the Lee trimmer and check every cases after it's been resized and before loading. If the case grew any, it will be trimmed off to the correct length.

 

[rsmithsr50]

no reason to trim "just because"
find YOUR neck length,
AND TRIM FOR YOUR CHAMBER

 

[243winxb]

SAAMI max says 2.100”

And SAAM I says minimum brass length is 2.080"

I would go with the standard trim to length of 2.090" Let the short ones grow.

Make sure all brass was fl sized first.

 

[Jody Simcox]

I’ve got the Sinclair tool to measure chamber length...I’m right at .020” short of chamber length with my longest case, so no worries there....

 

[Jody Simcox]

no reason to trim "just because"
find YOUR neck length,
AND TRIM FOR YOUR CHAMBER

I believe I’m well within the margin of safety, based on the length of my chamber...please explain what you mean by my neck length...thanks

 

[6MMsteve]

if you have a borescope you can drill a case and scope the nk end and see the area between the mouth and throat..it sure does make you feel better seeing the distance between the case and throat or bore...or you may see something you don't want to see

 

[gunsandgunsmithing]

I believe I’m well within the margin of safety, based on the length of my chamber...please explain what you mean by my neck length...thanks

Pretty sure he and I are talking about the same thing...actual chamber length of the neck portion. Since you say you have the tool, you likely know the actual length so I'm a little confused as to why you referenced the saami length earlier. Regardless, ideally, I'd let it grow since you have that much clearance. When it gets closer, I'd uniform it to .015 shorter than actual chamber and use .005 shorter as my max.

 

[Jody Simcox]

Pretty sure he and I are talking about the same thing...actual chamber length of the neck portion. Since you say you have the tool, you likely know the actual length so I'm a little confused as to why you referenced the saami length earlier. Regardless, ideally, I'd let it grow since you have that much clearance. When it gets closer, I'd uniform it to .015 shorter than actual chamber and use .005 shorter as my max.

now I’m confused...chamber length vs neck length? The link you provided (which is the tool I have) describes a way to measure distance from bolt face to end of chamber...I’m nowhere near the end of my chamber...my question remains...given the measurements I provided for my brass (.016 spread), would you recommend that I trim brass, and if so, to what length. Also, I simply referenced SAAMI for completeness for those who may not be familiar with the specs for this cartridge.

 

[Bill K]

Most every reloading manual will give you a case length measurement and a trim length measurement.
But you can order tools, find your chamber length and trim approx. ten thousands shorter.

 

[Jody Simcox]

I guess a more specific question would be...would I be better off if I trimmed everything to, say, 2.080”? Thus, greater consistency among all cases (.005” spread as opposed to current .016”).

 

[Straightshooter1]

I guess a more specific question would be...would I be better off if I trimmed everything to, say, 2.080”? Thus, greater consistency among all cases (.005” spread as opposed to current .016”).

I like to trim every time to the same length for the consistency and don't have to think about a longer case engaging the carbon ring. So, for me, the answer to the question would be "yes."

 

[rsmithsr50]

ok , why are you wasting brass ?
.010 is plenty of clearance.
if you know the length of your chamber( to the end of the neck of the chamber) then trim based on THAT number, not some generic number.
-0.010 from YOUR chamber neck length( that is what the tool measures..NECK LENGTH OF THE CHAMBER).

I’ve got the Sinclair tool to measure chamber length...I’m right at .020” short of chamber length with my longest case, so no worries there....

 

[gunsandgunsmithing]

now I’m confused...chamber length vs neck length? The link you provided (which is the tool I have) describes a way to measure distance from bolt face to end of chamber...I’m nowhere near the end of my chamber...my question remains...given the measurements I provided for my brass (.016 spread), would you recommend that I trim brass, and if so, to what length. Also, I simply referenced SAAMI for completeness for those who may not be familiar with the specs for this cartridge.

I did answer that question, in how I would do it if it were mine. Your brass is short as compared to the saami number you gave and you have a wide variation in lengths. First, establish your actual chamber length using the aforementioned tool. Once you know the real length, not just a spec, you can trim accordingly OR, as I would do it it were mine..shoot it another time or two to get the length closer to your actual chamber length as measured with the tool.
I'm curious how/why you're getting such a wide spread. How many firings are on it and were the loads relatively close pressure wise?

I would prefer the length be more consistent but moreso, I'd rather not have that much clearance in order to help prevent getting the dreaded carbon ring as bad.

Sorry if I wasn't clear before.

 

[Straightshooter1]

. . . and if you'd like to actually see that space at the case mouth, simply chamber a fired case then take a look with your trusty inexpensive Teslong bore scope.

 

[NorCalMikie]

no, but get a Sinclair tool and you will know your chambers actual neck (OAL) length and know when to trim

And most chambers are cut about .020 longer than the max trim length. Measure it, write it down, refer to it before you even think about trimming.
And bushing bump dies won't pull the neck longer on the upstroke.