Long Range Hunting Online Magazine


Go Back   Long Range Hunting Online Magazine > Rifles, Reloading, Optics, Equipment > Reloading

Reloading Techniques For Reloading


Reply

Change seating depth - neck tension?

 
LinkBack Thread Tools Display Modes
  #1  
Old 11-10-2010, 10:09 PM
Junior Member
 
Join Date: Nov 2010
Posts: 3
Change seating depth - neck tension?

I have a .243 that shoots my handloads decent - about 1 MOA. I typically seat bullets for this rifle about 20 thousandths from the lands. However, some factory loads with a similar bullet shot great from the rifle. My measurements show that the bullets were seated about 100 thousandths from the lands. This shows me that a deeper seating depth for my load is definitely worth trying.

My question is this - should I just knock the bullets in my loaded rounds back (incrementally, of course), or should I just load new rounds. I have a slight concern that knocking the bullets back on loaded rounds may break the case's neck tension and therefore have different characteristics than rounds with bullets seated initially to that depth, but I have quite a few loaded and this would be a simple way to make test rounds. What do you guys think?

Thanks.
Reply With Quote
  #2  
Old 11-11-2010, 11:03 AM
Platinum Member
 
Join Date: Oct 2007
Location: Mountians of SW NC, near Asheville
Posts: 1,596
Re: Change seating depth - neck tension?

Dave, you pose a few interesting and significant points well worth discussing.


"I typically seat bullets for this rifle about 20 thousandths from the lands. However, some factory loads with a similar bullet shot great from the rifle. My measurements show that the bullets were seated about 100 thousandths from the lands. ... This shows me that a deeper seating depth for my load is definitely worth trying. "

I wonder how you got to 20 thou off; was that from tests or just picked?

It seems a LOT of people have been deluded that seating at or very close to the lands is more accurate. As your test of factory ammo at five times further off shows, that 'close to the lands' idea is nonsense more often than not. In years of loading for quite a few factory rifles I'm yet to find one that shoots best at the lands, usually off from .020" to .035" but sometimes as far off as .100".

Rules of thumb are good for measuring thumbs, only personal testing can determine what a given load needs to shoot well in a given rifle.


My question is this - should I just knock the bullets in my loaded rounds back (incrementally, of course), or should I just load new rounds. I have a slight concern that knocking the bullets back on loaded rounds may break the case's neck tension and therefore have different characteristics than rounds with bullets seated initially to that depth,.."

Use what you have. Seating them deeper will have no detectable effect on "tension".

I have no X-ray vision high speed camera so I can't say for certain what happens inside a chamber those first few nanoseconds after igniton, nor can anyone else, but many of us believe the pressure expands the case firmly against the chamber before most bullets can even clear the neck! If we are correct, fretting about "bullet tension" is basically irrelivant and all that matters is the timing of the bullet hitting the lands. Thus, if the 'neck tension' is sufficent to keep bullets from falling out during handling it's enough and the point of varing OAL is to tune the entry into the lands.


" have quite a few loaded and this would be a simple way to make test rounds. What do you guys think?"

I think you are correct.

Like powder charges, best OAL (bullet jump) is a range, not a specific point, plus/minus nothing. It's easy to load on the ragged edge of a good range so small variations can kick the bullet outta the group. Work to find the full width of the good shooting range - powder or seating - and load in the middle of it so you won't get unexplainable (?) "flyiers."

I'll make a suggestion to simplify and speed your tests; at first, just to quickly eliminate any poor OAL spots, shoot TWO SHOT groups. You know how your present load and the factory stuff shoots so what you'll be looking for is a seating range that tightens it. That closing will be gradual if your tested seating steps are small.

Seat your already loaded bullets deeper in steps of perhaps 5 thou per pair. That's close enough so that as you approach a node you should see the two rounds getting closer and as you leave the node they will get wider. (NOTE: Any two rounds that are VERY CLOSE together but don't follow the OAL pattern of getting closer and then wider are probably meaningless flukes. Again, the good seating depth is NOT a specific point.) After you have identified the OAL that seems to do best do a few more test groups at and around that to confirm or disprove it's the best you can get.


Good luck, and let us know how it goes!

Last edited by boomtube; 11-11-2010 at 05:14 PM.
Reply With Quote
  #3  
Old 11-14-2010, 10:32 AM
Silver Member
 
Join Date: Dec 2007
Posts: 297
Re: Change seating depth - neck tension?

Hay guys I can realy use some help here. I just started hand loading last year so bear with me. I got my 7mm R M shooting great but my .06 is another story. It shoots factroy win 150 gr great sub MOA. So I took one of them apart trying to get close to the same powder it looks like double base spherical. I bought one of them RCBS precision mic's so I could find out exact seating depth. When I conpair the rifle to the round it is 0.080 jump but it dont shoot to good. The magor question I got is it seating depth or powder HELP.
Reply With Quote
  #4  
Old 11-14-2010, 02:39 PM
Platinum Member
 
Join Date: Oct 2007
Location: Mountians of SW NC, near Asheville
Posts: 1,596
Re: Change seating depth - neck tension?

"The magor question I got is it seating depth or powder HELP. "

Probably.

Sorry, we really can't be more precise than that.
Reply With Quote
  #5  
Old 11-14-2010, 02:50 PM
Platinum Member
 
Join Date: Aug 2003
Location: NC, oceanfront
Posts: 3,328
Re: Change seating depth - neck tension?

cva54, it is considered rude to hijack a thread. You should start another with YOUR question..

dave115, I don't see a reason that you couldn't re-seat bullets a little deeper. But there are some things to consider;
If the load is already compressed, you might not be able to hold deeper seating.
Depending on the cartridge volume, seating deeper can increase pressure due to greater bullet displacement(less effective case volume).
I'm very sure that necks open to release a bullet before it actually moves. But even a small tension change can affect early powder burn. Depending on the powder burn rate/load this may or may not affect your tune. So seating loaded rounds deeper to match other great shooting ammo, might be self defeating from another loading attribute.

I would not attempt to find 'optimum' seating depth through re-seating loaded ammo(beyond your experiment). Only during traditional load development -as reloaded.
Reply With Quote
  #6  
Old 11-15-2010, 01:03 PM
Junior Member
 
Join Date: Nov 2010
Posts: 3
Re: Change seating depth - neck tension?

Thanks for the input. Those numbers were measured using an OAL gauge and a comparator, so I am pretty comfortable with them. Also, no issue with compressed loads.

I will try knocking the bullets back 5 thousandths at a time and see what I come up with. Thanks again.
Reply With Quote
  #7  
Old 11-15-2010, 01:08 PM
Junior Member
 
Join Date: Nov 2010
Posts: 3
Re: Change seating depth - neck tension?

"I wonder how you got to 20 thou off; was that from tests or just picked?"

Sorry Boomtube, misunderstood the question - I thought you meant how did I measure the distance from the lands.

As far as the 20 thou off, it was just a number I picked as being as close as I would want to seat bullets for a hunting rifle that may get knocked around a bit.

Anyway, thanks again for the advice and I will follow it.
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes


Similar Threads for: Change seating depth - neck tension?
Thread Thread Starter Forum Replies Last Post
Neck Tension 7mm Eclipse Reloading 6 09-06-2010 06:22 PM
Volocity change vrs. seating depth. 400bull Reloading 1 02-05-2009 02:45 PM
neck tension rufous Reloading 3 08-24-2007 08:57 PM
neck tension col48 Reloading 0 08-06-2006 02:28 AM
.223 Neck Tension JWH Clark Reloading 5 04-02-2006 02:49 AM


All times are GMT -5. The time now is 06:56 PM.


Powered by vBulletin ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Management Powered by vBadvanced CMPS
All content ©2010-2014 Long Range Hunting, LLC