Case trim length

[RD57]

I don't trim new brass unless they exceed the max OAL. After two firings they usually need to be trimmed, and I only take them down .003"- .005" below max. On my overbore cartridges (220 Swift) I trim to max length, let the brass take the heat during firing and not the chamber/throat juncture. I don't mind trimming after every resizing operation if required, it's just part of doing business.

 

[baldhunter]

Since I started using my Frankford Arsenal Trim and Press Center my case prep goes like this:
Full length resize
Trim to minimum length
chamfer
deburr
clean primer pockets
run brass through tumbler
I was always curious as to how much room there was in the chamber for the case necks to grow.A case cut to length,chambered and bore scoped showed me I probably would wear the case out before I reach the max chamber length.I'll still trim each time because it's so easy for me using the Frankford and just to keep things uniform.Here is a picture of the chambered brass.As you can see,plenty of room to grow.

 

[340PR]

Like others, I trim to .010" under max for my chambers. First trim is after fireform. I trim after each firing (for consistency). The process usually touches most or all of the necks Any neck that doesn't trim is measured, inspected, and grouped with other non-trimmed cases within the lot. They are usually under .001" variance, but not always.

 

[RD57]

I did the same thing with my bore scope to verify trim lengths. Nice picture!

 

[Roughwater]

It's a good idea to measure your actual chamber case length first and trim cases to .010" short of that measurement.

I've found I get more carbon ring buildup with shorter cases, so I started trimming to .005" under my measured chamber length. I do have to take care that my cases are not over that .005".

It's fine to also use .010" under your chamber, to be safe. If your chamber and resizing die don't mesh well, you will be trimming more often.

Like DOK said above.

If you measure you would likely find your TRUE max case trim length is actually much longer than the book trim length. If you're crunching your powder while loading, trimming to your actual max length can be another benefit to trimming your cases longer.

 

[DSheetz]

I'm confused I thought you trimmed the case so that you could get good neck tension without the die crimping the bullet as a lot of dies have a crimp ability built into them and you set them down to crimp or you let your brass grow to the crimp area of the die .

 

[BoomFlop]

The die won't crimp unless you allow it to crimp. Back the die off a touch and it won't crimp.

If you are crimping, then having the same length case is the only important step as once again you can adjust the die to allow as much or little crimp as you want regardless of the overall length of the case.

Steve

 

[Blackhawk]

I always take them back to trim length and call it good, they need to be done soon enough anyway.

When uniformity means everything with regards to handloading ammunition, I see no other way( UNLESS YOU MEASURE AND CULL EACH BRASS HULL ) of maintaining a constant jump setting ,which indeed may result in MV variations (ES) on a chronograph as well as (SD )vertical and or horizontal shot string placement.
JUMP DATA VARYING AS LITTLE AS .005" MAY RESULT IN A LESS THAN IDEAL BULLET PLACEMENT.
I am not saying that brass alone is the only culprit just one of many. (too many causes and effects to list here), however I would suggest that you eliminate as may variables as possible.
However if you are not into refining your loads for the most accuracy then please feel free to overlook my comments and continue to load as you see fit.
I mean only by my words to offer some line of rationale.
Remember, Your Chronograph is your best friend!

 

[BrentM]

I'm confused I thought you trimmed the case so that you could get good neck tension without the die crimping the bullet as a lot of dies have a crimp ability built into them and you set them down to crimp or you let your brass grow to the crimp area of the die .

I'd be surprised if anyone here crimps or used a die with a crimp. Most use a bushing die. On gas guns and such people are more likely to crimp. As already stated just back the die off unless it won't bump the shoulder.

 

[BoomFlop]

BrentM

Crimp is done with a Seater die and has nothing to do with a Sizing die (Bushing or not).

Steve

 

[BrentM]

BrentM

Crimp is done with a Seater die and has nothing to do with a Sizing die (Bushing or not).

Steve

Jesus I think i covid 19. My brain is not firing on all cylinders. Duh. Not even sure what I was thinking...

 

[Wy Will]

I usually get a reading for maximum length in my chamber and trim .010 under that.

 

[DSheetz]

I think that crimping the bullet and the primmer are done so that in semi auto and full auto they aren't moved and loosened or pushed back by the recoil crimping is also done on pistol rounds for the same reason .

 

[Tiny Tim]

Alot depends on your ultimate goals. If absolute precision is it, then trimming to consistent length along with many other things ought to be done. As many have stated, chambers are often longer than we think and there are definite advantages to trimming nearest the actual length of YOUR chamber. Some cartridges are also notorious for growing and if you don't like trimming every or every other firing, perhaps trimming to min spec is for you. I use different methods for different rifles depending on their purpose and my goal for it.