I'm working up new unfired W\W 25-06 brass for an up-coming plains game trip to Namibia. After running them all through the full length sizer I miked them and found many were only 2.475" not the trim to length of 2.484" So all 60 were cut to 2.475" and there is still the required 1 caliber of neck length to grasp the Barnes X bullets---.257"

I would say as long as you have one caliber of neck length, then you're not too short. I believe that it is more important to have them all at a uniform length for consistant bullet pull than anything else. And I've got a trip of a lifetime hanging in the balance!

Better too short than too long. I have sim. problems w/ .404 brass. Norma are 0.05" longer than Bell. It's for uniformity sake, especially when crimping. Just trim all to a uniform length.

I just starting loading for a new 35 Whelen. I took 50 pcs of new RP brass and 30 once fired factory brass and trimmed them to 2.475, hopefully I'll never have to trim them again. When they grow back to 2.494, I'll buy new cases because these will probably be pretty well used by that time.Pretty hard to be too short.

The RCBS recommended case trim length for the 30-06 is 2.484". In fact all the recommended case trim lengths are typically .010" less than Max case length. I use this for all my reloading and it works just fine. The new cases will work fine since they are shorter than the max recommended case length. For consistancy in my loads I always run my cases through the trimmer after sizing and preparing the cases for reloads , this includes new cases. They can be trimmed in just about the time it takes to measure them.

Max case length for a 30-06 is 2.494 and I understand that many set trim length to about .01 shorter than max or 2.484.

I know you are supposed to trim all your cases to the shortest case length for uniformity; however, I got a batch of 100 New Remington 30-06 cases that range in length from 2.489 - 2.474.



I've looked through my reloading manuals and can't find anything on "Min" case length. Trimming these to 2.474 would be .02 short of max length. It doesn't seem to me like .02 shorter than max would be too short but just thought I'd better ask. How short is too short?



Thanks

firstshot

FS,
The length of the case is a subject that really doesn't get the attention it deserves. And Yes, you definitely can get your cases too short. I try to keep mine to somewhere between 0.005" and 0.010" shorter than the MEASURED chamber length. If the trim length as listed in the manual is 2.494", you can bet your very last dollar the chamber is quite a bit longer than 2.505" That is because almost every gunsmith, whether chambering a barrel in the factory or a custom smith, will almost always let the reamer run a little long. They do that to protect us from ourselves, and for liability reasons.

Let ne tell you why getting the case too short can be bad. And here I quote from M.L. McPherson who published an article on that very subject in the April 2004 issue of The VARMINT HUNTER Magazine. He says that if the gap between the end of the brass case and the beginning of the throat is more than about 0.020" to 0.025" the bullet can be deformed. When the hammer drops the pressure builds up pretty fast, and before the bullet can move even 0.10" the pressure is already up above 20,000 psi and that is enough pressure to deform a bullet - even a jacketed bullet. When the bullet is under this kind of pressure it will obturate (swell) to a larger diameter in the space of the gap. Then as it is pushed into the throat, the leade and the rifling it is oversize and will experience deformation which can easily lead to accuracy degredation. For those concerned about breech pressure, it will also push the pressure up higher too, just because it is oversize and is being forced into a diameter smaller that it now is.

And so, the important thing is to MEASURE the length of the chamber throat and not let your brass get to be more than 0.025" shorter than whatever length it is.

Hope this will help.

Don Shearer

Thanks a lot Don. Makes a lot of sense.

firstshot

By using a Sinclair Chamber Length Gauge one can measure the length from the bolt face to the end of the chamber neck. This will give you the Max length of a case. Any case that is longer will crimp the case neck mouth into the bullet resulting in high pressure. Without knowing the actual length of a chamber one can not determine how short is to short or when it is to long.

If you have a chamber that requires you to seat out bullets fairly far for best results, for certain cartridges with short necks (.223 Rem springs to mind) a short case neck will offer less support for the bullet. My .223 Rem throat has now receded far enough, that I can't really seat out bullets any further - at least I should not go with cases that are too short, nor should I try to use boat tail bullets. So there probably are cases where a neck can get too short. In most cases, it probably does not matter too much - other than possible accuracy effects you may see. As mentioned above, some reloaders consider this important, although most probably consider it a lesser issue.
- mike

Don thank you.
You made me think that I always trust in the Lee trimmer tools that I had always used.

I never had a doubt about that it can cut the case out of the standard measures, even if in a safety lenght.

Thanks for all the info guys. Seems like "shorter than recommended trim length" is not an issue as long as you've got enough neck to seat the bullet properly.

Question: With this batch of Remington brass, the majority of them are shorter than recommended trim length. (i.e. <2.484)

Should I just shoot them until they reach >2.484 and then trim. OR should I just trim the whole batch to the shortest case length in the batch.

If I don't trim them, and just wait for them to grow, how much will the various case lengths affect accuracy?

Thanks
firstshot