Seating depth question for custom chamber

6

65shooter

Member
I'm sending in seated bullets in my cases to give the barrel guy an idea of where to cut the chamber. This is my first time. SO, this is a mag fed rifle; I'm guessing I shouldn't load to max mag length to set the chamber to as when the round count jumps up the throat will start to move forward.
I will be shooting Berger 140s. in a 6.5cm. 1. How much does the jump matter on these bullets? 2. Should I seat em deep and set the throat to say 5 off the lands and start there? That way I could be seated deep, then I could play with at least a little jump, or jam, and still be inside mag legth.

What should I be doing?
 
I'd cut the chamber with a very small jump at SAAMI OAL. That'll give you room to fine tune your OAL to that particular barrel while staying within magazine length.

GsT
 
65shooter said:
I see. Is saami typically longer or shorter than match chambers?
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AFAIK, the only thing SAAMI has to do with this is that ammo at that length should fit in ALL mags but has nothing to do with the mag length of YOUR gun, nor throat length being a specific length. It could be a short action or a long action. Obviously, the same ammo should fit both mags, right?

You're on the right path. Just spec the freebore to a length that allows a bit of jam at YOUR mag length, plus about .040-.060 clearance in the mag.
Generally, we work with one or the other but not both in the accuracy game...mostly dealing with neck length and a bit of shank still in the neck. But when it has to be fed from a mag, that's the determining factor and it should be throated accordingly...if it needs to feed from a magazine. Single fed, mag length nor saami length have any bearing at all on what you need.
 
Build dummy rounds. Load into the mag. Make sure you have "extra room" and my guess is, over time you'll be going to a heavier bullet as the throat wears.
Have the chamber cut to THAT dummy round OAL.
 
Nor Cal Mikie said:
Build dummy rounds. Load into the mag. Make sure you have "extra room" and my guess is, over time you'll be going to a heavier bullet as the throat wears.
Have the chamber cut to THAT dummy round OAL.
Click to expand...
don't know about this guy but I had to remove the spacer out of my Win M70 mag well. The only sporter I have with a long freebore is my Weatherby.
 
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