- June 5, 2016 at 1:25 pm #28283VelocetteParticipant
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OK, I’ve had a question for a while about criteria for TTL.
Now I will present it to the assembled mavens, wizards and pundits of this forum.
When trimming your rifle cases to length, what criteria do you use when you choose to trim or not to
trim. For example, if with a .308 case, the TTL in the load manuals is 2.008″, how much over that dimension
do you allow before you decide to trim it? Do you chuck it in your trimmer at 2.009″ or wait til it stretches to
a few thousandth more?
The reloading manuals specify a single dimension, with no + / – . What say you?
- June 5, 2016 at 1:56 pm #28284AnonymousInactive
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You need a better manual
I have one of the old free win handouts with load data and in it is most of the common pistol and rifle cases dimensions in it.
Every rifle is different — A custom tight chamber will be different from a off the rack hunting rifle
for 308 Max length is 2.015 / trim length is 2.005
What I am doing for one of my rifles is Full length size brass load and fire it 4 times (3 neck size) checking length after each firing.
By the 4 firing brass is getting a bit tight to chamber and I (aneal and) full length size it again and trim to 2.005 and repeat
I would not trim till length is over 2.010 or more (this is for a off the shelf rifle)
- June 5, 2016 at 2:46 pm #28287GhostHawkParticipant
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I’m old school and a bit lazy. “If it ain’t broke don’t fix it”
Now as soon as it starts causing problems, sure. But I don’t go through the rounds many of you do.
And much of my shooting is straight wall pistol cases which I think don’t stretch as much.
- June 5, 2016 at 4:08 pm #28290blackthornParticipant
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Each firearm is different! Knowing the maximum TTL is a safety net issue. If you really want to know the safe TTL for your firearm, you will need to make a chamber cast and measure, so you can know the absolute maximum TTL. Otherwise, just go with the manual numbers and call it good. I would be very surprised if any off the shelf firearm had a chamber that would be dangerous using the TTL specified in any published manual.
- June 6, 2016 at 3:58 am #28304GoodsteelKeymaster
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Most off the shelf firearms have a chamber so long there’s no way you’ll ever touch it. They are so long in fact that you often have .050 clearance. The only rifles I’ve run out of chamber with are some of my custom wildcats where I was intentionally making the brass fit perfect, and I underestimated how the cartridge jumps forward when firing. You need at least .010.
The main thing you are after in a normal situation is consistency. You want all those puppies to be the same length in the same condition both dynamically and at rest, and this has more to do with bullet release than it does with anything else. Therefore, you can control the hell out of your OAL but if you are not devoting equal or greater care to the hardness of the necks (how many times they have been fired) and the surface condition of the necks (how clean they are) and the thickness of the necks (turn your necks), you’re just spinning your wheels.
You’ve got to think of the necks of each piece of brass as a rifle barrel in and of itself. Its the thing that transfers the bullet into the barrel, so just like the barrel, you need consistent diameter and stiffness, a square mouth, and a smooth and concentric diameter.
Just think of it from the bullets point of view: What would your barrel look like if it had as much inconsistency as your brass necks? One shot would be through a barrel with a bad crown, the next would be through a rotted out mil-surp, the next would be through a barrel with a degree of hook, the next would be through a barrel that had rifling twice as deep on one side as it is on the other etc etc etc etc.
The earlier in the process a situation manifests itself, the more effect a small change can have on down the pipeline, and there’s only so many things that have any effect on accuracy that happen behind the neck of the brass.
Consider the whole enchilada and give it due diligence. The chain if accuracy and precision is only as strong as it’s weakest link, so focusing like mad on one detail without paying any attention to the things surrounding and wrapped up around it, is a fools errand, and you might as well just let it all flop.
Its an all or nothing situation.
- June 7, 2016 at 6:04 pm #28324uber7mmParticipant
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Same as building a house. If the foundation is not square and level, cuttin’ in the roof is pain. Nothing lines up like it should. Roofers have to fudge the single rows to get things to look right. The project ends costing more and nobody’s happy.
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