Trim length question

[Bassman1957]

Been reloading for a short time and have a question on trim length for 223. I have my trimmer set to 1.750 in. and 90% of my cases are coming out dead on but my question relates to some of my cases that are shorter than 1.750. How short is too short? Some of my cases are not even touching the cutter and are measuring anywhere from 1.740 to 1.748. All cases have been run through full length sizing die before trimming.

Thanks for the responses

 

[Fine Figure of a Man]

I don't know how short is too short but I wouldn't worry about 1.740. If you're worried about accuracy you may want to sort out the short ones. If they are for an AR I doubt it will make a difference.

 

[Walkalong]

1.740 is just fine. Anything under 1.760 is OK assuming a proper chamber, but most trim anything over 1.750 back to 1.750. Some wait until they hit 1.760 though. I trim them all every time, back to 1.750. I don't worry about the short ones that don't get touched by the trimmer, and they will stretch a bit closer after each firing.

 

[rfwobbly]

I don't worry about the short ones that don't get touched by the trimmer, and they will stretch a bit closer after each firing.

Exactly the way I do it too. Your job, should you chose to accept it, is to make those cases grow !

 

[bbqreloader]

I trim to 1.745 and so far no issues.

 

[pert near]

From a pressure perspective, being too short is not a problem, but being too long is. Loading ammo that you need to crimp makes length important for consistency.

 

[Hondo 60]

Just anudder voice in the wind.
For me, anything over 1.755 gets trimmed to 1.750.
I've never had a problem with too short - but I think I might pitch anything under 1.740

 

[JimKirk]

The shorter length will cause no problems for you ...

MY question for you is why are you getting the various lengths ...

Are you using a trimmer with a collet to hold the brass ... if so the varying diameter of the rims of the brass control how far the collet is drawn into the trimmer body ...unless you are using a Forster trimmer ...it uses a slightly different collet ... if the rim is smaller in diameter the brass will be drawn farther into the trimmer and the length will be longer than say a larger diameter rim ... the larger the diameter the shorter the brass ... measure the rim diameter of a few brass and you'll see how much they vary ....

This is my solution .... I made a pilot that fits into the collet both small primer size & large .... the brass is held "dead center" of the pilot and the cutter stop ... I do have to use a rubber tipped glove to hold the brass from turning ... and you learn how much force to apply so the brass does not spin ... this method cuts the length from the actual bottom face of the brass to the cutter face .... it would never change unless you change it ... as I said "Dead Center" just like a lathe ...which that is what this type trimmer is a brass lathe ...

Here are a couple of photos ...
Here is the pilot ....



Here is how it works ...

 

[macgrumpy]

Short cases reduce neck tension which reduces max pressure and results in lower muzzle velocities.

 

[Bassman1957]

The shorter length will cause no problems for you ...

MY question for you is why are you getting the various lengths ...

Are you using a trimmer with a collet to hold the brass ... if so the varying diameter of the rims of the brass control how far the collet is drawn into the trimmer body ...unless you are using a Forster trimmer ...it uses a slightly different collet ... if the rim is smaller in diameter the brass will be drawn farther into the trimmer and the length will be longer than say a larger diameter rim ... the larger the diameter the shorter the brass ... measure the rim diameter of a few brass and you'll see how much they vary ....

This is my solution .... I made a pilot that fits into the collet both small primer size & large .... the brass is held "dead center" of the pilot and the cutter stop ... I do have to use a rubber tipped glove to hold the brass from turning ... and you learn how much force to apply so the brass does not spin ... this method cuts the length from the actual bottom face of the brass to the cutter face .... it would never change unless you change it ... as I said "Dead Center" just like a lathe ...which that is what this type trimmer is a brass lathe ...

Here are a couple of photos ...
Here is the pilot ....



Here is how it works ...

Jim, my brass that is short is short on initial measurement after sizing before I trim. This is once fired Wolf brass that was shot by myself and a friend not range pick up. This is the first time I've encountered this situation and was concerned that I might have to pitch a bunch of casings. I haven't had any that were shorter than 1.740 so based on the replies to my original post I guess I'm all right. Thanks to all for the replies!

 

[JimKirk]

Bassman .... The shorter brass is no problem ... You may sort of out so you have "like" brass in the same when shooting ... Don't think I've ever seen a FC brass that was not "short"... So if it is factory short and did not give a problem ....it probably not going to be a problem for you ....

Thing is it will grow in the next three shootings and you'll have to trim ....then you can cut them to the length you want ....

 

[Bart B.]

A 10% spread in case neck length (.010" for a .100" length) it grips 22 caliber bullet jackets will cause a 10% spread in bullet release force needed to get the bullet out of the case neck. That's assuming the case neck tension on the bullets and their friction index has zero spread.

Do you measure loaded round's bullet release (not seating) force across several to see how many pounds average and spread is? A 20% spread is common in the most accurate ammo. But the average is in the single digit range.

I cannot discriminate a .010" to .015" spread in 30 caliber case length having any significant impact on accuracy. There are bigger fish to fry. You'll be much better off ensuring the barrel's groove diameter is at least .0003" smaller than your bullet diameter. And the barrel's bore and groove diameters' spread is .0001" or less.

Some dimensions are critical. Others can be sloppy.