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Help with seating depth

 
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  #8  
Old 10-18-2012, 05:42 AM
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Re: Help with seating depth

There's more than one way to skin a cat and this one calls out all the knives.

First of all, the optimum OAL with your bullet in your rifle with your load is subjective. NOT Absolute. Meaning we have to experiment and find the best combination for our individual circumstance and component selection.

OAL tools and comparators and precision mics are great tools, but not absolutely necessary to find the best OAL..........there's that absolute word again.

Those tools will sure help us reload ammo at a later date with different bullet lots to the same specs though.

We can:

Soot the bullet or mark the bullet with sharpie and seat deeper until barely noticable rifling marks show from chambering a previously fired dummy cartridge/case.......when satisfied, measure the OAL and call that "Jam".

Split the neck of a previously fired case and chamber the dummy round. measure just as above.....accomplishes the same thing but the bullet will move in/out of the case easier.

Barely resize the neck of a fired case (just enough to resist bullet movement by finger pressure) chamber and measure.......again, just like before, and easier than splitting a perfectly good case neck.

Using a once fired/fully neck sized case, seat the bullet deeper and deeper (gradually) untill you just, I mean just faintly see rifling marks (polishing bullet with fine steel wool each attempt obviously)........at whatever seating depth you only faintly see marks, measure and call that "Jam".

Get a comparator, OAL tool, precision mic, use the cleaning rod method or any of the above methods and you'll get to the same place.........just use the same method every time you do it if you want repeatable results.

Start at point X and proceed to point Z; somewhere along the way, we'll find the optimum seating depth for that bullet/powder and charge/primer combo in that particular rifle.

Just remember, after a few hundred rounds fired; that relationship will change due to throat erosion of the lands. Then we gotta re-figure and adjust accordingly. This is obviously where the tools come in, cause we gotta measure and record all that again as the throat changes.....and again, and again, and again.........chase the lands, because they like to run from us.
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  #9  
Old 10-19-2012, 10:14 AM
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Re: Help with seating depth

Thanks for all the great advice. Ill likely be trying one of those methods over the weekend. Ill pick up an OAL tool as soon as I can after that. How much jam should I account for using one or any of those methods?
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  #10  
Old 10-19-2012, 10:45 AM
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Re: Help with seating depth

Quote:
Originally Posted by XILoveGunsX View Post
Thanks for all the great advice. Ill likely be trying one of those methods over the weekend. Ill pick up an OAL tool as soon as I can after that. How much jam should I account for using one or any of those methods?
Lots of folks start load development with OAL just barely kissin the lands or .010-.020" back off them. Some guns wont let us seat bullets out that far due to magazine size. Each rifle will genrally require a different "setting".
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  #11  
Old 10-19-2012, 10:51 AM
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Re: Help with seating depth

When I push a round into the lands during this process should I assume that I'm. 010, .020 etc INTO the lands? How much should I compensate for to get the bullet. 010 ish OFF the lands
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  #12  
Old 10-19-2012, 11:16 AM
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Re: Help with seating depth

Quote:
Originally Posted by XILoveGunsX View Post
When I push a round into the lands during this process should I assume that I'm. 010, .020 etc INTO the lands? How much should I compensate for to get the bullet. 010 ish OFF the lands
If you're seeing definitive riflling marks on the bullet, then I'd say that's .020 jam. But again it's relative, so you can call it whatever you want and use that as your baseline. From there, back off .015 and back off again another .015 and once more another .015.......shoot all 4 lengths and stick with what the gun likes after that.

If you're using one of the fired case and real bullet methods, dont fully FL size the case. Just size enough to grip the bullet or use a neck size only die. Fully FL sizing will sometimes give a false measurement because the ejector plunger will push the case further into the chamber. Generally, a case that's been fired once works best. It shouldn't be tight and wont be loose either.
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  #13  
Old 10-19-2012, 11:20 AM
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Re: Help with seating depth

Just what I was looking for thanks!
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  #14  
Old 10-19-2012, 02:18 PM
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Re: Help with seating depth

Should I do this before or after an OCW test?
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