trimming length or tolerance?

dfraser

dfraser

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Hi all,

I am starting to work on my first reload. It is for my rem700 308. My Lyman book and the Hodgdon reloading website shows that the trim length is at 2.005". I am using new Federal stuff that I just fired last weekend. The lengths of the Federal stuff is way over that trim length.

My question is: shouldn't there be a trim length tolerance instead, with 2.005" being at the smallest end, and whatever at the top end?

Regards
 
That is max overall length. Just like max overall length for the finished cartridge is max. The bullet can be seated lower or even longer in some cases but won't fit in a mag.

Just keep your brass trimmed to under this lenght and most importantly exactly the same lenght.
 
frigpig said:
That is max overall length. Just like max overall length for the finished cartridge is max. The bullet can be seated lower or even longer in some cases but won't fit in a mag.

Just keep your brass trimmed to under this lenght and most importantly exactly the same lenght.
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No it is not the max overall length. The trim length is the length that you normally trim the case to when it requires trimming. The trim length is often .010" shorter than the nominal case length for the cartridge, which for the 308win is 2.015". If the cases measure between the trim length, and the nominal length, no trimming is necessary. That is the recommended tolerance range. As for the overall cartridge length, you can often exceed the number in the manual, and still have the cartridge fit the magazine.

To the OP, ignore post #3, because it is totally false.
 
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stubblejumper said:
No it is not the max overall length. The trim length is the length that you normally trim the case to when it requires trimming. The trim length is often .010" shorter than the nominal case length for the cartridge, which for the 308win is 2.015". If the cases measure between the trim length, and the nominal length, no trimming is necessary. That is the recommended tolerance range. As for the overall cartridge length, you can often exceed the number in the manual, and still have the cartridge fit the magazine.

To the OP, ignore post #3, because it is totally false.
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Thanks Stubblejumper

To me, that sounds like pretty dangerous advice to go by for a brand new reloader like me.

And thanks for your reply, that is what I was looking for with all these federal 1x brass, that I fired myself.
 
In reality the chamber length is always longer than what the reloading manuals say they are for SAAMI chambers. Sinclair sells a nifty tool that aids in measuring the actual chamber length of a particular rifle in a particular caliber. When I started using this tool what I found was that I was trimming cases way shorter (up to .040" in some examples) than needed when following the recommended trim length in the manual. I'm not saying you should let your cases grow and grow in length or spend money on this tool. I'm only offering some insight.
 
hend238 said:
In reality the chamber length is always longer than what the reloading manuals say they are for SAAMI chambers. Sinclair sells a nifty tool that aids in measuring the actual chamber length of a particular rifle in a particular caliber. When I started using this tool what I found was that I was trimming cases way shorter (up to .040" in some examples) than needed when following the recommended trim length in the manual. I'm not saying you should let your cases grow and grow in length or spend money on this tool. I'm only offering some insight.
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Where do I find this tool. I am trying to learn everything about this and do it properly.

Thanks
 
A chamber cast can provide you with that information, but rather than trying to maximize neck length, you're better off with having consistent neck lengths.
 
Such tools are available, but they are hardly required to load safe, consistent ammunition. If you stick with case lengths between the trim length, and the nominal length, you will be just fine.
 
cosmic said:
Well - Does your rifle chamber the brass at its current spec? That's the acid test... It also tells you if you've not sized it properly.
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Improperly trimmed brass will still chamber, specially in a bolt action. Your bullets will be crimped hard and possibly cause pressure problems depending how hot the load is. Of course I would agree there would be a point where too long of a case will not chamber. Your suggestion has merit providing one removes the firing pin assembly from the bolt so when you chamber a case the only resistance felt will be that of the case and not the main spring. That goes for resizing properly as well.
 
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stubblejumper said:
Such tools are available, but they are hardly required to load safe, consistent ammunition. If you stick with case lengths between the trim length, and the nominal length, you will be just fine.
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I couldn't agree more and is very good advice. I personally like having that kind of info in my reloading notes though for various reasons.
 
Just a note in case you didn't know you trim after you full lenght size or neck size .

I trim each time when loading for accuracy (consistency is the key)and when necessary when loading for hunting
 
dfraser said:
Thanks, never realized that was the brownells sister site. I am always in brownells too, that one is dangerous as well, spent many a dollar in there at 1am in front of my laptop.
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Sinclair used to be on its own. Too bad Brownells purchased it 'cause Sinclair's customer service, inventory and back order wait times sucks now in comparison.
 
I use a Hornady overall case length gauge and it works well, you really find the C.O.L to actually touch the lands, then you can back off .20 thou or whatever your rifle likes. I only reload .308, and I try to start with a 2.005" case, although I'm sometimes off a little, I always try to stay in the 2.004-2.009 range as the the more consistent, the better as you go through the rest of the process.
 
What are you using to trim your cases? I also found that federal gold medal match cases were on the long side (0.005" over 2.015" vs 2.010" the lapua came as). I used the Lee trimmer and pilot that cut to 2.007". Also maximum length is 2.010", so I'd say between 2.005-2.010 will be safe. I also just bought a headspace gauge from Amazon.ca best 30 I spent yesterday, I recommend that you get one aswell.
 
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