Seating depth

Seating depth

This is a discussion on Seating depth within the Reloading forums, part of the Defensive Ammunition & Ballistics category; I reload 4 different calibers: 9mm, 45 ACP, 5.56/223 REM and 308 Win. By my way of thinking, assuming all else remains the same, the ...

Results 1 to 12 of 12
Like Tree44Likes
  • 4 Post By Chuck R.
  • 11 Post By msgt/ret
  • 7 Post By Glock2201
  • 1 Post By dangerranger
  • 7 Post By Bad Bob
  • 3 Post By krunchnik
  • 3 Post By Rob99VMI04
  • 1 Post By BlackJack
  • 5 Post By gasmitty
  • 1 Post By flintlock62
  • 1 Post By dangerranger

Thread: Seating depth

  1. #1
    Senior Member Array BlackJack's Avatar
    Join Date
    Jun 2006
    Location
    Colorado
    Posts
    821

    Seating depth

    I reload 4 different calibers: 9mm, 45 ACP, 5.56/223 REM and 308 Win.

    By my way of thinking, assuming all else remains the same, the deeper you seat your bullet, the higher the pressure will be. Leading off of that, the higher the pressure, the higher the velocity.

    Is this correct, or is my thinking just off base?

    Thanks.

  2. #2
    VIP Member Array Chuck R.'s Avatar
    Join Date
    Oct 2006
    Location
    NE, KS
    Posts
    2,968
    No and yes.

    Generally, you're correct, right up until you start seating the bullets into the lands, then pressure also increases. This is why you find longer freebores in 5.56 and also Weatherby chambers.
    msgt/ret, M1911A1, Taxman and 1 others like this.
    homo homini lupus est

  3. #3
    Moderator
    Array msgt/ret's Avatar
    Join Date
    Jun 2006
    Location
    North Carolina
    Posts
    15,893
    Seating deeper will increase pressure but if you are tippy toeing around with max pressure seating too deep may result in dangerous over pressure. It is better to stick with the recommended seating depth to insure proper feeding and keep pressures in line with recommendations.
    When you have to shoot, shoot. Don't talk.
    "Don't forget, incoming fire has the right of way."
    A 9MM MAY expand to .45 but a 45ACP will never shrink to 9MM.

  4. Remove Advertisements
    DefensiveCarry.com
    Advertisements
     

  5. #4
    VIP Member Array Glock2201's Avatar
    Join Date
    Mar 2013
    Location
    NH
    Posts
    2,768
    Personally I would not want to mess around trying to get more velocity by seating bullets deeper. I would rather find powder that creates velocity using a reloading manual. I prefer the ones put out by the bullet manufacturers. I might then work up to the max loads with that powder/ There are a lot of guys on here with way more experience than I have that might feel comfortable with doing something like that but I would not.

  6. #5
    VIP Member Array dangerranger's Avatar
    Join Date
    Sep 2012
    Location
    Exact center of CA
    Posts
    5,897
    Actually some pistol ammo has less pressure by seating the bullet down on the powder charge but not crushing the powder. We don't do that much because it causes feeding problems. The reason it lowers the pressure is there is no extra room to work as an expansion chamber. As the burning powder expands into a gas the bullet accelerates up the smooth brass case before it hits any resistance at the barrel. DR
    Chuck R. likes this.

  7. #6
    VIP Member Array Bad Bob's Avatar
    Join Date
    Feb 2012
    Location
    The BAD lands
    Posts
    12,661
    If you need to hotrod it, you need a bigger gun.
    msgt/ret, Havok, airslot and 4 others like this.
    Check out the CR-12 - wilkinsontactical.com

  8. #7
    Member
    Array krunchnik's Avatar
    Join Date
    Jun 2012
    Location
    Lakeland,TN
    Posts
    327
    I agree with the theory of using a different powder for higher velocities-I have reloaded since 1980 and have never seated deeper to get higher velocity.
    In fact I have had self defense ammo get bumped into the casing from random feeding-I will normally pull the bullet-dump the powder and reuse the casing.
    msgt/ret, airslot and M1911A1 like this.
    THE CROW

  9. #8
    VIP Member
    Array Rob99VMI04's Avatar
    Join Date
    Aug 2006
    Location
    Northern Virginia
    Posts
    5,377
    Danger Danger Will Robinson, There is no way to know what your going to spike the pressure to. As stated use a different powder or graduate to a magnum. Faster doesn't always mean more accurate. Most reloader conduct latter tests to see what the best load is.
    msgt/ret, M1911A1 and airslot like this.

  10. #9
    Senior Member Array BlackJack's Avatar
    Join Date
    Jun 2006
    Location
    Colorado
    Posts
    821
    Thanks everybody for the feedback.

    To make things a bit clearer, I am not trying to "hotrod" my loads, or to get any additional velocity as a result of adjusting the seating depth. And, my loads are well below the max for my bullets. I was just trying to get some clarity on my thoughts regarding seating depth.
    dangerranger likes this.

  11. #10
    Senior Moderator
    Array gasmitty's Avatar
    Join Date
    Jun 2007
    Location
    Gilbert, AZ
    Posts
    19,158
    For .45 and 9mm, I've played with bullet seating depth to optimize cartridge feeding in the 1911s. For any given load, plus or minus 0.050" created a barely measurable difference. These are modest-pressure cartridges and as long as you're not loading near the limits, they're very forgiving.
    Smitty
    AZCDL Life Member
    NRA Patron Member
    NROI Chief Range Officer

  12. #11
    VIP Member Array flintlock62's Avatar
    Join Date
    Nov 2013
    Location
    Arkansas
    Posts
    4,525
    If I want higher velocity, I use a powder that produces more energy. I DO NOT play around with the seating depth. Some of the newer powders develop more velocity while lowering pressures. I would take that route. I also do not shoot someone else's reloads!
    msgt/ret likes this.
    NRA lifetime member

    Flint

  13. #12
    VIP Member Array dangerranger's Avatar
    Join Date
    Sep 2012
    Location
    Exact center of CA
    Posts
    5,897
    Quote Originally Posted by BlackJack View Post
    Thanks everybody for the feedback.

    To make things a bit clearer, I am not trying to "hotrod" my loads, or to get any additional velocity as a result of adjusting the seating depth. And, my loads are well below the max for my bullets. I was just trying to get some clarity on my thoughts regarding seating depth.
    If you are well below the limits, Playing with seating depths may give you some interesting results.
    I live in CA and have to hunt with Lead Free bullets. when I first made the switch to copper bullets I could not get much accuracy from them. But after some reading I found that they needed to be 60 thou off the lands! In my gun they shot best 75 thou off the lands! My once upon a time tack driver is back to shooting sub min of squirrel brain! I guess the harder copper needs a little run up to speed before hitting the lands!

    In pistol ammo most of my seating experiments have centered around feeding issues. I have't noticed seating depth affecting accuracy much at all. Good Luck. DR
    msgt/ret likes this.

Sponsored Links

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •