Results 1 to 7 of 7

Thread: How little jump can you get away with?

  1. #1

    How little jump can you get away with?

    Been working up some loads in my 243. Measured the chamber and found that the the rifle likes very little or no jump onto the lands, to the point where when an unfired round is extracted there is very fine scoring on the bullet from the lands.

    I understand some of the BR boys actually load onto the lands but does this not unduly increase pressures?

    Accuracy is in the 0.2"s for a 3 shot group. Pull the bullet back to 10 - 20 thou jump and the groups open up to nearer the inch mark.

  2. #2
    If you have the chance of chronoghraphing your load, & you have no other visual pressure signs, I would go with it!.
    (The Unspeakable In Pursuit Of The Uneatable.) " If I can help, I will help!." Former S.A.C.S. member!

  3. #3
    No visual signs, but not got access to a chrono at the minute - next on the list!

    Was a bit concerned about pressure spike and whether a chrono would show this? Would velocity increase in the same way as an increase in powder would give greater velocity? My understanding is that the pressure spike would be just that, a "spike" and would occur immediately before the bullet left the case as it was up against the lands, thus causing more pressure to build up in the case than if there was a small jump for the bullet to "ease" into before it made contact with lands.

    Or am I just over complicating all this??

    Just didn't look right extracting a round and seeing tiny marks left from the lands, but it is soooo accurate

  4. #4
    Quote Originally Posted by 75 View Post
    No visual signs, but not got access to a chrono at the minute - next on the list!

    Was a bit concerned about pressure spike and whether a chrono would show this? Would velocity increase in the same way as an increase in powder would give greater velocity? My understanding is that the pressure spike would be just that, a "spike" and would occur immediately before the bullet left the case as it was up against the lands, thus causing more pressure to build up in the case than if there was a small jump for the bullet to "ease" into before it made contact with lands.

    Or am I just over complicating all this??

    Just didn't look right extracting a round and seeing tiny marks left from the lands, but it is soooo accurate
    Accuracy is great but if you are seating bullets that tight into the rifleing then make sure you always have a cleaning rod with you (not a pull through unless it has a very heavy end) as, sooner or later you will pull a bullet in the chamber when unloading an unfired round. Not much fun as powder get everywhere and you look pretty stupid if you are in company. JC

  5. #5
    Don't worry about it. If it continues to bother you, try seating the bullet progressively deeper and see how the accuracy fares. I have seen loads tighten groups as the bullet is seated progressively deeper.~Muir

  6. #6
    Thanks all - your comments/reassurances are appreciated

  7. #7
    75. Most of my current loads are out of the lands, but I did use a 129SST load in the past that went 9 thou into the lands. How far into the lands do you think you are seating your bullets? I measure my seating using a process similar to the one outlined below.
    http://riflemansjournal.blogspot.com...ing-depth.html
    Secondly, are you using a bushing die to achieve a specific neck tension or not? I am using a bushing die and aiming to get at least 2 thou of neck tension. Rgds JCS

Similar Threads

  1. Throat erosion versus bullet jump?
    By Monkey Spanker in forum Ammunition, Reloading & Ballistics
    Replies: 10
    Last Post: 20-02-2010, 09:13
  2. The future Shooter & the hoops to jump through?
    By finnbear270 in forum Deer Stalking General
    Replies: 10
    Last Post: 20-12-2009, 11:58

Posting Permissions

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