New fire-formed brass "Trim to...." question

[Jesse09]

Given: Winchester brand 30-30 Win brass fire-formed to 30-30 A.I. The "trim to" specification is 2.019" - 2.029".

I have 40 cases, same lot. After fire-forming, 20 of them fall in the specified range, so no questions. The other 20 range from 2.012" to 2.017"; so, all those are short.

What should I do? 1. Trim the longer cases to the 2.019" minimum, then hope for the best with the shorter brass mixed in? 2. Discard the short brass? (Hard choice for a lot of reasons.) 3. Trim the longer brass below the specification to 2.015" so all the brass is within, say, a .003" range. I'm leaning towards doing this, but don't know if that's too far below the specification. Note, also, that I haven't yet max loaded these newly fire-formed cases; they may be even shorter after they are fired again.

Thanks for your replies.

 

[243winxb]

Is the head to datum measurement the same on all?

Could some have not fully formed to the AI chamber?

 

[MagnumManiac]

I would not touch any of them yet.
The brass is not yet stable and will grow differently until it is stable.
All of my Improved cases shrink upon firing because brass is pulled from the neck to fill the shoulder and another firing is always needed to fully form to the chamber, only after that do I even measure the brass length. Necks do not have to be square to shoot well, it's a myth.

Cheers.

 

[waspocrew]

^^ Agreed. Don't trim them at all. Get at least another firing on them before you trim.

 

[Jesse09]

Thank you for your answers. I do know that I should do another fire-forming round; but, I have previously fire-formed this same lot of brass and components in this same firearm. That time I did do a second round and the maximum shoulder datum difference between the first and second fire-forming rounds was just .001". I was planning this time to take the chance that, given the first go-around, my present brass is fully formed.

Just for the sake of discussion, assume I do run another round of fire-forming. If, as I expect, many of the brass lengths then fall below specified minimums, what's your best advice? As I asked in my original post, should I selectively trim so that all the lengths are within about .003", even though that would be shorter than the specifications? Or, what?

 

[waspocrew]

I'd just trim them to spec - the ones below will eventually grow.

 

[Jesse09]

waspocrew, that's a tempting approach that I did consider. I'm worried, though, that the initial mixed lengths (up to a difference of .007") will give me inconsistent results on target. What do you think?

 

[Bob Wright]

If you're crimping it will make a difference on how your die is set. Most 30-30 rounds are crimped. Maybe feed them manually until you get some resizes on them and monitor OAL. AI chambering will slow the case lengthening so this will be interesting.

 

[MagnumManiac]

Having different neck length will change nothing you can see on target.
More importantly you need consistent neck tension, which will not happen until the brass is stable regardless of a few 'thou difference.
If you can see a difference on target, I bet it is neck tension differences, not neck length.

Cheers.

 

[Gorill@]

I've shot .308 way short with no issues. I'd leave it alone. Can't put it back.

 

[RD57]

Let the brass grow to fit your chamber. The SAAMI chamber length spec for the unmodified 30-30 is 2.083". The SAAMI cartridge brass max length is 2.0395" which is .0435" short already . I do not understand why there is a suggestion to trim so short to 2.019" Most of us are handloaders and not commercial ammo manufacturers required to follow SAAMI specs. If you use a Lee factory crimp die, it won't even crimp the brass at 2.019" (at least mine won't without modifying the shell holder)

I allow my brass to grow from firing and resizing to protect the chamber area from carbon build up and flame cracking. I take my longest piece of brass and chamber it in the rifle with the bolt, and then insert my Teslong borescope in the muzzle and slide it down the barrel to view the brass and chamber area to verify the brass is not too long. I have not found a factory rifle chamber yet that requires brass to be trimmed shorter than the SAAMI maximum cartridge brass length.

After two firings (assuming the loads where warm enough to expand the brass) I'll trim the brass to a uniform length for a match rifle to help with uniform neck tension.

 

[dan1953]

I am not being a smart arse, but is 30-30 and precision rifle used in the same sentence? Real question.

 

[Lenny Foffa]

Perhaps the Sinclare Chamber Gauge may be helpful. I think it will work in a Lever Gun. Take one of your short cases, Drill out the primer pocket, Cut the neck back a 10th, insert the gauge which looks like a plug, and close the action as if to fire a round. Take it out and measure it. Now that's your chamber length. So far I have used 4 of them in 5 different rifles. Two of which were chambered in 270 Win. In every case, so far, the chamber in that Rifle , was longer than the case length as shown , as max ,in the manuals . You may find yourself trimming less that you thought you had too. Just a thought Sir.

 

[RD57]

Yep Dan, you're being a smart arse, but I like smart arses! I have seen a Thompson Center 30-30 shoot smaller groups at 100 yards than most rifles on the range that day. That general info applies to all cartridge brass.
One thing I forgot to mention: If this is for a lever action and not for a single shot or bolt action then 30-30 brass will require trimming based on what bullet you plan on using. Most lever actions will not cycle a round longer than 2.560" from the magazine. It's best to keep your Over all Length (OAL)no more than 2.550". Each bullet manufacturer and different lot numbers of the same brand have their bullet crimp ring/cannelure a certain distance from the tip of the bullet. As an example my lot of Sierra 150 grain FN bullets #2000 from top of the cannelure to the tip of the bullet is .473". Your max brass length for these bullets for an loaded OAL of 2.550 would be 2.077" (2.550 - .473 - 2.077). My Hornady 170 grain FP #3060 are .499" from top of cannelure to tip of bullet, so max brass length would equal 2.051". Your brass will probably fail or get lost before it gets to be that long, but it is still a consideration especially for cast lead bullets and custom bullet moulds.

I've been handloading for 53 years and I don't know when it got started or who started it but 2.019 is really the minimum SAAMI 30-30 brass length, and probably should not be referenced as a "Trim to Length".