Brass Trim Length

[biged85]

Hi All,

Quick question i was hoping someone could help me with. 

Starline 6.5 CM brass brand new, seems to be slightly short and varies from 1.904 - 1.912 in length.  I haven't had any problems running it and have avoided trimming it as it is already short.

My question is, for consistency etc would you trim it all to the shortest length i.e. 1.904? My extreme spread on the chrono is not great so looking for improvement. 

The few I have fired do not seem to have grown much at all.

I use a factory rifle.

 

Cheers

 

Ed

[The Gun Pimp]

Trim after first firing.  But, with a factory rifle, there will be lots of room for the brass to grow.  But, does no harm to trim to same length.

[Andrew]

I FL resize all new brass in my FL die and then trim all cases to the exact same length - the length of the shortest case. In this way, the second time I load the brass is will be as close as possible, dimension-wise, to the brass on the first loading.  Too many people tend to take the 'first firing' of brass as a throw away session. My method lets you pretty much know -good or bad- what to expect on the second loading.~Andrew

[biged85]

On 3/2/2019 at 12:16 AM, Andrew said:

I FL resize all new brass in my FL die and then trim all cases to the exact same length - the length of the shortest case. In this way, the second time I load the brass is will be as close as possible, dimension-wise, to the brass on the first loading.  Too many people tend to take the 'first firing' of brass as a throw away session. My method lets you pretty much know -good or bad- what to expect on the second loading.~Andrew

Firstly, thank you both for your replies.

Andrew, so when you say you trim to the shortest length do you still do that if it means the brass is then shorter than minimum book length?

Essentially, for 6.5cm would you be happy trimming down new brass to 1.904? (book minimum 1.910)

 

Many Thanks

 

Ed 

[Popsbengo]

Six thou under size isn't important. You may find after the first firing that the length is within spec.

[Andrew]

9 hours ago, biged85 said:

Firstly, thank you both for your replies.

Andrew, so when you say you trim to the shortest length do you still do that if it means the brass is then shorter than minimum book length?

Essentially, for 6.5cm would you be happy trimming down new brass to 1.904? (book minimum 1.910)

 

Many Thanks

 

Ed 

Yes. I trim to the shortest case in the LOT. But only after I FL resize.~Andrew

[biged85]

9 hours ago, Andrew said:

Yes. I trim to the shortest case in the LOT. But only after I FL resize.~Andrew

Thanks Andrew, i always FLR new brass, especially the starline. 

 

15 hours ago, Popsbengo said:

Six thou under size isn't important. You may find after the first firing that the length is within spec.

Well the strange thing is Popsbengo is I have some twice fired Starline that has barely grown an all, literally no growth. 

Very strange indeed when compared to Hornady brass that went from 1.910 to 1.918 after one firing!

[Popsbengo]

3 hours ago, biged85 said:

Thanks Andrew, i always FLR new brass, especially the starline. 

 

Well the strange thing is Popsbengo is I have some twice fired Starline that has barely grown an all, literally no growth. 

Very strange indeed when compared to Hornady brass that went from 1.910 to 1.918 after one firing!

It's possible your chamber is quite tight, ie towards the minimum tolerance and the Starline cases are towards the larger end of tolerance so the brass doesn't have space to stretch when fired. The neck itself doesn't change much during firing.  This isn't a bad thing, less working of the brass.

It's really the length of headroom that's important here not the overall case length including the neck.  The neck has one job to do, hold the bullet in the correct position.  The shoulder of the case sets the headspace and is really important.  A Hornady gauge would be a useful tool to compare the different manufacturers brass,  it's not practical to try to measure without some form of annular gauge to reference to.

If the rounds chamber ok and accuracy is acceptable I wouldn't worry about a few thou on neck length.

 

[biged85]

On 3/5/2019 at 1:18 PM, Popsbengo said:

It's possible your chamber is quite tight, ie towards the minimum tolerance and the Starline cases are towards the larger end of tolerance so the brass doesn't have space to stretch when fired. The neck itself doesn't change much during firing.  This isn't a bad thing, less working of the brass.

It's really the length of headroom that's important here not the overall case length including the neck.  The neck has one job to do, hold the bullet in the correct position.  The shoulder of the case sets the headspace and is really important.  A Hornady gauge would be a useful tool to compare the different manufacturers brass,  it's not practical to try to measure without some form of annular gauge to reference to.

If the rounds chamber ok and accuracy is acceptable I wouldn't worry about a few thou on neck length.

 

Many thanks for your advice, I am going to have a go at trimming some down. I then shoot some 5 round groups and chrono them at the same time. see what happens. 

 

ATB

 

Ed

[jcampbellsmith]

Trim length results depend on what kind of trimmer you are using. 

• With a Wilson trimmer I'm getting consistent case lengths as the trimmer indexes on the case head.
• With my Little Crow trimmer I'm getting consistent neck lengths as the trimmer indexes on the case shoulder.

I prefer consistent neck lengths.

Regards

JCS

[Popsbengo]

1 hour ago, jcampbellsmith said:

Trim length results depend on what kind of trimmer you are using. 

• With a Wilson trimmer I'm getting consistent case lengths as the trimmer indexes on the case head.
• With my Little Crow trimmer I'm getting consistent neck lengths as the trimmer indexes on the case shoulder.

I prefer consistent neck lengths.

Regards

JCS

Interesting.  If the case is sized the shoulder profile should be consistent so if head to shoulder is set prior to trimming what's the difference between either method?

I would have thought that indexing off the shoulder was prone to exaggerate errors in neck length ??  Am I missing something here?

[jcampbellsmith]

 

 

Regards 

JCS

[Popsbengo]

JCS:  That explains how they differ but not if one method is superior to another. My Lyman trimmer is manual, infinitely adjustable and turns out trimmed cases to less than a thou tolerance.  Does me just fine but I can see if you were doing hundreds of cases regularly then a power system would help.  Then there's the depth of internal chamfer to consider...

[jcampbellsmith]

56 minutes ago, Popsbengo said:

JCS:  That explains how they differ but not if one method is superior to another. My Lyman trimmer is manual, infinitely adjustable and turns out trimmed cases to less than a thou tolerance.  Does me just fine but I can see if you were doing hundreds of cases regularly then a power system would help.  Then there's the depth of internal chamfer to consider...

I've used both methods. Being lazy I favour the Little Crow Trimmer and I feel it will give me more consistent case neck lengths.

Regards

JCS

[JabaliHunter]

On 3/7/2019 at 11:51 AM, Popsbengo said:

Interesting.  If the case is sized the shoulder profile should be consistent so if head to shoulder is set prior to trimming what's the difference between either method?

Nothing, but one is a lot quicker...

[Popsbengo]

On 3/13/2019 at 11:53 AM, JabaliHunter said:

Nothing, but one is a lot quicker...

What might I do with those extra seconds?  OK, I can hear that 😂