Long Range Hunting Online Magazine


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

Reloading Techniques For Reloading


Reply

Pulling bullets / Reseating / Neck Tension

 
LinkBack Thread Tools Display Modes
  #8  
Old 05-27-2013, 09:55 PM
Silver Member
 
Join Date: May 2010
Location: Central Ohio
Posts: 251
Re: Pulling bullets / Reseating / Neck Tension

Quote:
Originally Posted by woods View Post

So do you have any explanation why the cases of mine that had been fired more often did not return to a different dimension? Or is the variation in springback in work hardened brass as opposed to new soft brass negligible or so small that it doesn't exhibit itself in thousandths?
Since the chamber (specificlly around neck) restricts how far the brass can go in a outward manner when cartridge is fired coupled with the heating of brass from hot gases of powder burning then when brass cools, the cooling produces slight annealing/shrinkage of brass?
Just a thought/theory I have.
Reply With Quote
  #9  
Old 05-27-2013, 10:43 PM
Gold Member
 
Join Date: Jun 2006
Location: Shangri-La
Posts: 923
Re: Pulling bullets / Reseating / Neck Tension

Certainly the neck brass will springback some after firing. Not sure if the heat from the firing will have any annealing effect.

3 of the loads in the original post are custom tight necked chambers, the 6.5 rem mag, 338RUM & the 280AI. The 280AI is stamped ".313" neck" but the fired case OD is ~.311", so there is ~.002" springback on the neck after firing also.

The 375 Ruger was chambered with a standard reamer, at least that is what I told the smith, and the fired OD is .005" larger than the loaded round OD. Figuring a little springback, I would assume I have .007" neck clearance.

The 06 is a factory Steyr and it has a .0085" difference in OD between fired neck and loaded round, so it must be close to .010"+ neck clearance.
__________________
If you can read this, thank a teacher.......if you are reading this in English, thank a soldier.
Reply With Quote
  #10  
Old 05-28-2013, 05:47 AM
Platinum Member
 
Join Date: Aug 2003
Location: NC, oceanfront
Posts: 3,171
Re: Pulling bullets / Reseating / Neck Tension

Hardened brass springs back more.
You're not hardening brass with fired expansion, you're taking it to yield.
When brass is expanded let's say 3thou(1thou beyond springback), it yields 1thou and springs backs slightly less than expected 2thou -because it is now thinner. This action happens with each firing provided you're running high enough pressures, or with low shoulder angles/high body taper/big clearances, to cause yielding(although less & less of it). Unmanaged, it leads to extraction problems.

The answer to extraction problems is NOT loose chambers, or big sizing. It's managing load pressure for the amount of barrel steel around a given chamber area to control brass yielding. This, followed by sizing that maintains target springback, produces stable brass that works well, lasts forever, and without FL sizing(just shoulder bumps & partial neck sizing).

With a case designed with high shoulder angles, low body taper, fired in low chamber clearances at moderate pressures, it's possible to eliminate sizing in reloading all together. The brass will not yield and just spring right back to set dimensions.
I nearly managed this with my 6.5WSSM, but 35deg shoulder angles are still too shallow. Next chamber will provide 45deg shoulders. Necks are fitted, and I don't have to size them.
Reply With Quote
  #11  
Old 05-28-2013, 07:25 PM
Bronze Member
 
Join Date: Apr 2009
Posts: 90
Re: Pulling bullets / Reseating / Neck Tension

Finally a post in the reloading section with some intelligent discussion and factual data to back it up. Great info.

Just wanted to add as a side note a finding that I had a few weeks ago in regard to neck sizing.

I've got a custom chamber STW by Gre-Tan. It was cut with a .313 neck based on the dummy cartridge I sent with Remington brass. Now that there is short supply of that brass and since I had heard many good things about Norma I fire-formed some for my rifle from 300 H&H brass a while back. Once loaded up the neck diameter with the norma brass is only .310, so .003 clearance as opposed to a tight fit with the Remington.

So far I've only been able to shoot at 100 yards for comparison but there is a fall off in accuracy with the Norma brass. It's not much, but it is noticeable. This gun would consistently cut one hole at that range and now its more like a clover leaf. I still need to continue with load development but so far that is what I've found. I also noticed a higher spread in velocity as well. Both probably deserve more testing at this stage but I thought it was worth sharing.

Another note...if you start out wondering what size bushing to use don't try to mic the wall thickness and double it to calculate the bushing diameter. Find a way to size it down enough to get a tight fit on the bullet and mic the neck of a loaded round. Much more accurate and gets you the correct bushing the first time. I learned the hard way, hopefully someone else reads this down the road and it saves them some hassle.
Reply With Quote
  #12  
Old 05-28-2013, 08:40 PM
Gold Member
 
Join Date: Jun 2006
Location: Shangri-La
Posts: 923
Re: Pulling bullets / Reseating / Neck Tension

Well I'm not into benchrest but do like to control things. So I outside neck turn for .003" neck clearance. That allows me to trap the neck between a Forster outside turner and an inside reamer for a very consistant neck thickness




The reamer is .003" over caliber so after fire forming it will fit if I have .003" neck clearance on the load. With springback thrown in, now I know why the reamer has always been so tight.

Mike, one thing I'm confused about

Quote:
Originally Posted by Mikecr View Post
You're not hardening brass with fired expansion, you're taking it to yield.
Does that depend upon how much it is expanded? For instance in my factory 06 the neck clearance is .010". So wouldn't that much expansion work harden brass also like sizing the neck down with a die?
__________________
If you can read this, thank a teacher.......if you are reading this in English, thank a soldier.
Reply With Quote
  #13  
Old 05-29-2013, 02:25 AM
Silver Member
 
Join Date: May 2007
Posts: 268
Re: Pulling bullets / Reseating / Neck Tension

I don't think case neck spring back has much to do with case hardness.

The reason I think this is back in the day some benchresters used to turn their brass (tight neck chamber) so they didn't have to re-size the neck until they needed to move the shoulder back. I know for a fact the case neck is a lot harder after 5 plus firings yet the neck spring back was the same.

What tends to complicate the issue is the neck thicken over several firings and this will start creating different spring back until the necks are turned back to spec. If I remember right the spec was 1-1.5 thou over all...very tight! Rifles set up this way shot well enough, but the slightest bit of carbon or whatever in the neck area caused significant fliers and pressure spikes.

I never re size brass after pulling a bullet.
Reply With Quote
  #14  
Old 05-29-2013, 01:25 PM
Platinum Member
 
Join Date: Aug 2003
Location: NC, oceanfront
Posts: 3,171
Re: Pulling bullets / Reseating / Neck Tension

Quote:
Originally Posted by woods View Post
my factory 06 the neck clearance is .010". So wouldn't that much expansion work harden brass also like sizing the neck down with a die?
Neither upsizing, nor downsizing hardens brass. It's only when BOTH actions are taken that work hardening occurs.

With this, your neck expands 10thou meeting the chamber neck and continues following chamber neck expansion, until springing back on pressure release as it would given it's new thickness and normal hardness. If the necks were truly annealed(all energy removed), they would not spring back and could be left with an interference fit with chamber neck.
Now once you size down the normal neck to ~1-2thou under cal, you have completed one hardening cycle, and the case neck should spring back outward from whatever sizing needed to leave you with ~1-2thou under. It's typical to need 3-4thou under cal worth of sizing to be left with 1-2thou under cal after springback.
If you sized down more than 3-4thou under cal, you should expand necks to cal, leaving 1-2thou under after springback(inward). No good in going overbored, and bushings can only produce predictable result with 5thou or less of sizing.
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes


Current Poll
I currently have hunting preference points in the following states

All times are GMT -5. The time now is 08:51 PM.


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