Consequences of seating a bullet too deeply

Discussion in 'Reloading' started by wct097, Apr 22, 2013.

  1. The first round I made tonight is way too short. I didn't back the seating die's setting out far enough before making the first round and I seated it about 2/10" too deep. My first reaction is to toss it into my pile of screwups, but I'm curious... what are the consequences of seating a bullet too deeply? Failure to feed would seem obvious, but what about pressure? Can a bullet seated too deeply cause an overpressure problem?

    In this case, I'm loading 208gn poly tipped bullets with 7.3gn of H110 in an attempt to go subsonic with my 300BLK loads. I got this recipe from my Hornady manual. I'm thinking about tossing that round in the mag and firing it off. With 7.3gn of powder, I'm thinking that pressure wouldn't be an issue.

    Thoughts? Comments? Predictions?

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  3. shortening the overall length can increase your pressures. I am not sure how much, but its enough to where I wouldn't be trying to experiment. it's not worth the risk

  4. Taterhead

    Taterhead Counting Beans

    I think your instincts are pulling you in the proper direction. I would pull that round and start over. Seating deeper causes a smaller volume in the case, and therefore can cause greater pressures. With rifles, usually we are worried about being too long and having the bullet jammed into the lands. That can increase pressures. In your example, you are going the other way... but 2/10 is quite a bit, so certainly pressures can be in play.

    Pull that sucker and start over. You'll want to re-size. Remove the de-capping pin (if your setup allows that) first so that you don't de-prime.
    #3 Taterhead, Apr 22, 2013
    Last edited: Apr 22, 2013
  5. I'm not familiar with your particular load ,as a rule seating deeper in a case will increase pressure. You can always pull the bullet and start over,just to be on the safe side. SJ 40
  6. rednoved

    rednoved NRA Member

    I'd pull it.
  7. PCJim

    PCJim Senior Member

    I'll agree with Taterhead that you're thinking in the right direction. I just went and checked my 8th Edition Hornady book. The 300 Blackout isn't listed, so I'll defer back to you for additional information.

    In your Hornady load listing, what is the charge range given for using H110 powder? Let us know and a better reply can be given. If you're at a starting load and there is a significant charge range with the H110 powder (say, 7.3 - 8.1gr?), one could rationalize the shooting of the one round. If the charge range is rather tight, say 7.0 - 7.4, and you're already at 7.3, its a no brainer unless you like tempting Darwin.

    I might also suggest you invest in a bullet puller. They don't cost that much, and do save a lot of time in correcting errors.
  8. PCJim

    PCJim Senior Member

    I'll also add that H110 is a slow burning pistol powder, but considered on the fast side for rifle loads. It also carries a warning not to reduce loads by more than 3% in pistol loadings, which would indicate a relatively narrow charge weight.

    You also didn't mention the COL stated by Hornady. It too could be helpful.
    #7 PCJim, Apr 22, 2013
    Last edited: Apr 22, 2013
  9. In handguns, deeper seating, w/ faster powders, raises pressures. In rifle rounds, deeper seating often LOWERS pressures. The slower rifle powders don't get as excited about deep seating, but the closer you put the bullet to the rifling, the faster pressures rise. SO it's sort of inverted cause & effect. It's not uncommon to compress slow powders in hadgun or most rifle rounds.
    0.20" is quite a bit, so bullet length & powder charge come into play, I have just never seen deeper seating in traditional rifle rounds causing any serious pressure issues. The long 200gr+ bullets in the 300BO is a tweener, not really traditional rifle ballistics, not a handgun round either.
    #8 fredj338, Apr 23, 2013
    Last edited: Apr 23, 2013
  10. As Fred has pointed out, seating deeper in straight walled pistol rounds will increase pressure, but seating deeper in a bottle necked rifle round decreases pressure. You are somewhere in between with a rifle round with pistol powder.

    No need to "pull" the bullet, just place the round in your Kinetic puller and give it a few wacks increasing OAL without removing the bullet completely, then reseat the bullet to the proper depth.
  11. I think it's the 9th edition. Just got it last week.

    I don't have it in front of me, but I think that the range is 7.3gn for 1000fps up to 14.1gn for 1500fps.

    I'm going to order one of the RCBS collet pullers. My kinetic puller didn't seem to do much with this particular round, though I did get it from under 2" up to 2.15" after about 10 whacks (should be 2.20", I think).
  12. Boxerglocker

    Boxerglocker Jacks #1 Fan

    This is good info to share Fred. I learned this developing my rifle loads for my .223 R700.
    I would first load everything out of max OAL, try several groups for the approximate powder charge. Then fine tune the charge weight and OAL seating deeper to get the best groups.
  13. At that low end, I wouldn't bother. Besides, semi pulling bullets after seating is also problematic, it can reduce neck tension. Never good for consistent ammo. :dunno:
  14. Shot this batch today at the range. Stayed close to the bullseye with all 10 rounds at 25 yards, standing, open sights. Wouldn't cycle, however. Rounds would eject but with the exception of the last round, wouldn't chamber the next round. Pretty sure they were subsonic, but it's hard to tell at an indoor range.

    Will up the load and try again.

    Shooting from my 8.2" Noveske SBR w/ AAC 762-SDN-6:


    #14 wct097, Apr 23, 2013
    Last edited: Apr 23, 2013
  15. I am not sure 25yds is a fair test for any rifle round, but if it is all you have, then there you are. Starting loads in any semi, handgun or file, rarely give reliable results. You get better results starting with midrange loads & working up.
  16. Unfortunately, the only place I could find to shoot yesterday was an indoor range.

    As it was a new load for me, my primary objective in testing was functionality. Would it cycle in my SBR?

    My secondary objective was determining if it was subsonic or supersonic. I couldn't really tell inside the indoor range, though it was hearing safe without ear protection. I don't have a chronograph yet.

    Tertiary objective was to judge accuracy. Since it wasn't functioning, accuracy really didn't matter to me other than to make sure I was hitting what I was aiming at. I won't be loading that particular load again.

    I made two more batches of 10 each yesterday. One with 8.3gn of H110 and one with 9.2gn of H110. Will try to shoot outside today. Again, just looking for function and subsonic speed. Assuming I can get a functioning subsonic load with this bullet, powder, and rifle, I'll spend some time dialing it in to see what my range and accuracy looks like.

    edit: This is also a relatively new gun as well. I've only had the stamp back for a month and prior to that, I'd only put 20 factory rounds through it as a pistol. Since the stamp came back, I'd probably put 60 rounds through it. I'm thinking less than 100 in all. Once I get my loads figured out, it'll be interesting to see what it's capable of.
    #16 wct097, Apr 24, 2013
    Last edited: Apr 24, 2013
  17. njl


    If you feel it's too short, put it in your impact bullet puller, give it a whack or two, just to lengthen it, and then reseat it. If you're careful/lucky, you'll lengthen it without separating the bullet/case, and won't have to recover/recharge the powder.
  18. That's exactly what I did. Round fired fine. No signs of high pressure or a loose bullet.
  19. JBnTX

    JBnTX Texas

    When in doubt, pull it out.
    The bullet that is.
  20. Zyzogg

    Zyzogg Bartender

    If everything else is right it probably won't destroy your gun, but you wouldn't want to go there. I like to let a few "mistakes" sit around near my bench as a polite reminder...check everything...twice.

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