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Old 08-18-2010, 02:09   #1
Join Date: Jun 2010
Location: TX
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Seating Depth Variation

So after loading several hundred rounds now, I've noticed that no matter how hard I try, I end up with some variation in regards to OAL. Some rounds will come out right at 1.260 while others are high or low.

How much variation is acceptable, if any? So far I have gone back and corrected every round that was off. Im not talking a huge degree of variation, maybe .0015 thousands at the most.

Is this a common occurrence, if not how can I correct this. I haven't seen any information about this so any help is greatly appreciated.
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Old 08-18-2010, 04:04   #2
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I reload 40 S&W and have this happen sometimes.
Usually cleaning the seating die helps.
.0015 should not hurt as long as it still fits the mag and chambers correctly but may affect accuracy.
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Old 08-19-2010, 13:23   #3
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Other than function, changing the seating depth + or - .050" has no significant impact on pressure or velocity. Have you ever put your calipers on a box of "good" factory ammo. The seating depths vary more than this and they work fine. Your variations are most likely coming from variations in the shape of the bullets. They are not perfect either.

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Old 08-19-2010, 15:42   #4
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You don't mention what type press and or dies you are using...but some have had issues with the indexing plates of the progressives having some play and this has caused some variations in seating depth.

Compressed loads have sometimes allowed the bullet to be pushed outward slightly on rounds with less neck tension.

The seating die may have a seater plug thay is not totally secure.
The Single Stage press does offer a little more control with dies using a seater plug that is locked in place.

I load most of my 10mm stuff to 1.260" that are at maximum loads, other loads in the standar range, I use 1.250"...these fit and function form the magazines of my various 10mm guns some using aftermarket barrels.

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Last edited by _The_Shadow; 08-19-2010 at 15:42..
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Old 08-19-2010, 23:09   #5
Join Date: Jun 2010
Location: TX
Posts: 68
Thanks for all the information so far.

I did forget to mention that I'm using an RCBS Rock Chucker, as well as RCBS Dies. I also always tighten the seating plug. After the first response I went back and thoroughly cleaned all my dies, they were quite clean. I have not had a chance to load any rounds yet to see if this remedies the problem.

I have been loading Hornady Bulk 180gr FMJ bullets, at an attempted depth of 1.260. Like I mentioned some have come out right at 1.260 others 1.2585 etc.

I was mainly concerned if this would adversely affect pressure. My loads so far have only been what is written in the manuals that I have. I have not tried to load any hot stuff yet as I am still new and trying to learn as much as possible.

Again thanks for all the help, hopefully this additional information will help as well.
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Old 08-27-2010, 15:25   #6
Join Date: Jun 2010
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Just a small update, as well as to say thanks. I cleaned up all my dies like was suggested. I thought they were rather clean, however, now my seating depth is almost exact every time. So far it has only varied by .0005 which is more than acceptable. Thanks
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