Trim length and consistency

[michaelkirkland]

Hello,



I’m trying to understand something that I feel is not addressed very well within the reloading community, and that is trim length. I’m sure that there is going to be a LOT of varying opinion on this subject, but MY end goal is to achieve the most consistent bullets possible so that hopefully any missed shot are 100% due to my shooting abilities and not the ammo I made.



Ok, a little background on my setup. I’m using Lapua .223 brass, the SAAMI max case length is 1.760” my .223 Wylde chamber seems to be a lot longer than this. I full body size every time using Redding competition dies with a bushing. I will be the first to say, mistakes were made, but hopefully I have learned something. I foolishly trimmed my cases after the first firing, using what I thought was the correct length. It was not.



Now, here’s my question. At what length do I set my trimmer, ideally I want all my brass to be the same length, but they all seem to grow at different rates, and obviously this will effect pressure and subsequently velocities.



I currently set my trimmer to 1.760”, because after sizing, some brass grows past this spec. My concern is that some brass may never get to this length? While at the same time I want to keep my brass close to the chamber size so that it doesn’t grow to much or too fast thereby reducing it’s life span. The thinking here, is that if it doesn’t grow/stretch (much), then I’m less likely to see case head separation?

 

[secondofangle2]

Within 5 to 10,000 from book specified trim to length, it’s not gonna make a difference unless you have a real tight/short chamber. Just get a Giraud trimmer set it to trim-to length and spin them through it each time before you reload if you’re worried about it.

 

[supercorndogs]

You aren't shooting the difference between a few thousandths in trim length. Your chamber is most likely quite a bit longer than max trim length.

 

[OkieMike]

Are you shooting benchrest and chasing groups in the .1's?

If not, set your trimmer to trim at 1.760" and shoot.

You'll have a few over and a few under. As long as your chamber isn't pinching the brass and creating an unsafe condition, don't obsess over it.

You can spend hours trying to hold an insanely tight tolerance... Or you can set a reasonable amount of tolerance and spend more time shooting... I'll let you guess which one will improve your ability to shoot better.

Mike

 

[Hoser]

I trim my 223 brass to 1.745 once on my Henderson and never worry about it again.

 

[spife7980]

I trim to 1.750 every time on the giraud. Too easy not to.

 

[michaelkirkland]

Thank you everyone for all the responses!
I thought there was gonna be a lot of conflicting opinions on this, It's refreshing to see everyone agree. I've set my Giruard trimmer to 1.760, and as per my usual process I trim after every sizing. My brass will never get beyond 1.760, and I won't let the 6thou variance bother me any more. Thanks for pulling me out of the rabbit hole .

 

[supercorndogs]

I trim to 1.750 every time on the giraud. Too easy not to.

ITs not quite as easy as not trimming them every time.

 

[spife7980]

ITs not quite as easy as not trimming them every time.

Well, no, but its still easy enough that I can do a couple hundred while I already sit my ass on the couch all day anyways and not feel put out.

 

[Schütze]

I’d suggest to measure your chamber to determine if trimming is really needed.

I’m reloading only 6.5cr and 6br (started 2 years ago) and my necks haven’t grown enough to show the need for trimming.
I worry about creating a carbon ring to fast by trimming to short. But that’s just me, still learning…..
My new cheap Lyman Case Trimmer is still new in the box, purchased 2y ago.

 

[supercorndogs]

Well, no, but its still easy enough that I can do a couple hundred while I already sit my ass on the couch all day anyways and not feel put out.

True but arthritis is cumulative.

 

[OkieMike]

True but arthritis is cumulative.

15 years ago I would've laughed at that... It isn't nearly as comical now that I've got some miles on me.

Mike

 

[Frank Green]

See print attached....

From the bolt face to the end of the case mouth chamfer of the chamber it calls out 1.7726". Standard 223 Rem. is spec'd at 1.772". So basically the same.

Yes the book calls out max case length of 1.760".

Be careful if you decide to let your brass go longer...if it is getting too long you end up with the case no properly being able to release the bullet...this will cause accuracy and pressure issues. You have to have some room for expansion and things moving around. Even more so with gas/semi automatic type guns. Take M14's for example and or M1 Garands. Everytime you fire one of those guns...the case stretches like .006" to .007" to the shoulder of the case. So the case is going stretch/move on you. Bolt guns move around less but you have to factor in headspace, case stretch, brass varies from lot to lot and to maker and how much you are bumping the shoulder back each time you size the brass.

My recent M14 build and I'll put the numbers here....my headspace is +.0015" over min. which is 1.630". So it has +.0015" headspace. My brass is coming out of the chamber with shoulders flowed forward .006"-.007". As you know those shoulders have to go back to 1.630 when you resize the brass. Otherwise this is a cause of slam fires on these guns. When you size the brass it will stretch. So you have to keep up with trimming.

From a accuracy standpoint Mark here and Jack Neary (BR shooters) found out how critical it was to accuracy on brass trim length. So Marks 6ppc reamer 1.525" is the max length on his chamber. He trims all of his brass to 1.493". He will get 3 to 4 firings out of his brass and he trims it back to 1.493". More and more guys in the BR game are trimming they're brass after every firing. Does this apply to a PRS shooter or a hi power shooter...not necessarily but brass trim length can affect things.

Later, Frank
Bartlein Barrels

 

[Schütze]

See print attached....

From the bolt face to the end of the case mouth chamfer of the chamber it calls out 1.7726". Standard 223 Rem. is spec'd at 1.772". So basically the same.

Yes the book calls out max case length of 1.760".

Be careful if you decide to let your brass go longer...if it is getting too long you end up with the case no properly being able to release the bullet...this will cause accuracy and pressure issues. You have to have some room for expansion and things moving around. Even more so with gas/semi automatic type guns. Take M14's for example and or M1 Garands. Everytime you fire one of those guns...the case stretches like .006" to .007" to the shoulder of the case. So the case is going stretch/move on you. Bolt guns move around less but you have to factor in headspace, case stretch, brass varies from lot to lot and to maker and how much you are bumping the shoulder back each time you size the brass.

My recent M14 build and I'll put the numbers here....my headspace is +.0015" over min. which is 1.630". So it has +.0015" headspace. My brass is coming out of the chamber with shoulders flowed forward .006"-.007". As you know those shoulders have to go back to 1.630 when you resize the brass. Otherwise this is a cause of slam fires on these guns. When you size the brass it will stretch. So you have to keep up with trimming.

From a accuracy standpoint Mark here and Jack Neary (BR shooters) found out how critical it was to accuracy on brass trim length. So Marks 6ppc reamer 1.525" is the max length on his chamber. He trims all of his brass to 1.493". He will get 3 to 4 firings out of his brass and he trims it back to 1.493". More and more guys in the BR game are trimming they're brass after every firing. Does this apply to a PRS shooter or a hi power shooter...not necessarily but brass trim length can affect things.

Later, Frank
Bartlein Barrels

So if I use the br as an example and push my resized case all the way forward in my chamber, .030 of clearance will be sufficient? Thanks

 

[Taylorbok]

I currently set my trimmer to 1.760”, because after sizing, some brass grows past this spec. My concern is that some brass may never get to this length? While at the same time I want to keep my brass close to the chamber size so that it doesn’t grow to much or too fast thereby reducing it’s life span. The thinking here, is that if it doesn’t grow/stretch (much), then I’m less likely to see case head separation?

Trim length won't stop a case head separation, that's due to shoulder bump. is this a bolt or gas gun? .002" for bolt or .004" bump for gas.
the way I determine trim length is put a fired case in the chamber and shove my bore scope down there to see how much room it can grow. I pick an arbitrary length close to the transition that won't allow much room for a carbon ring to form. .010" has been working well for me

 

[michaelkirkland]

Thanks, that is great advice. This is a bolt gun, and I'm bumping 2 thou.

 

[Frank Green]

So if I use the br as an example and push my resized case all the way forward in my chamber, .030 of clearance will be sufficient? Thanks

I’d have to look at a BR print. Where are you getting the .030” from?

 

[Taylorbok]

So if I use the br as an example and push my resized case all the way forward in my chamber, .030 of clearance will be sufficient? Thanks

I’d have to look at a BR print. Where are you getting the .030” from?

I’d assume he’s talking from brass to the transition. Which .030” is lots

 

[Schütze]

I’d have to look at a BR print. Where are you getting the .030” from?

The difference in the measurements of marks 6ppc you mentioned as an example in your post above.

 

[Schütze]

I’d assume he’s talking from brass to the transition. Which .030” is lots

That’s what I thought too. I haven’t found any good info what it should be so I just use my own common sense. My br chamber depth is 1.585. 5x fired cases (full length seized) are up to 1.565, give’s 20 thou. “Room” correct? So I decided not to trim yet.

 

[Frank Green]

The difference in the measurements of marks 6ppc you mentioned as an example in your post above.

Following ya!

I don't know why it wouldn't work.

Mark and guys like him in BR will run the same say 10pcs of brass for the whole match. So he will shoot the same brass 4 times in a day. He trims after the day is finished so the brass is ready for the next day.