Sized brass too short - now what?

[PedalBiker]

Using a shell holder and FL size die from different manufacturers gave me brass that's too short. I've already fired and ruined one batch (visible case stretch and a sectioned case shows unacceptable thinning above the web), so with this batch I'm wondering the best way to fireform it back to full length.

 

[Jasper1573]

How short is too short?

I have trimmed brass 6-8 thousandths short and fired them until they grew a bit; then resized and carried on.

Those weren't my brass for match shooting, but they did shoot okay...it was a .308 Winchester.

 

[Craigman]

short on shoulder or short on OAL? Rifle or pistol? what caliber.

I form .270 WBY from 7mm mag and they are way shorter and shoot fine with good case life. If its bottleneck rifle brass, measure from the shoulder... Not the top of the neck to determine if its the cause of your problem

Using a shell holder and FL size die from different manufacturers gave me brass that's too short

do a search on full length sizing or headspace. Most likely not a mismatch, but a mis-adjusted F/L die.

 

[MEHavey]

Using a shell holder and FL size die from different manufacturers gave me brass that's too short. I've already fired and ruined one batch (visible case stretch and a sectioned case shows unacceptable thinning [/PHP]above the web),

I assume you mean the shoulder has been set back too much.

If that is the case (no pun intended) see here to fireform back to chamber dimensions:
http://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/3207576/Fire_forming_brass_made_easy

By any chance do you have either an RCBS Precision Mic (or a Hornady headspace gauge set)? If so, use that to check shoulder setback in the future

 

[PedalBiker]

Yes, shoulder set too far back - 30-06. The other batch sized similarly not only stretched too far, I also had a misfire on one round.

I need to look into the "false" shoulder, but I don't have any larger size expanders. I'm leaning towards the long seated bullets method.

Thanks for the link.

 

[bigedp51]

PedalBiker

1. A full length resizing die should be capable of pushing the shoulder of a case back shorter than minimum headspace.

2. The last batch of .243 cases I purchased had new unfired cases .009 shorter than minimum headspace.

3. I seated the bullets long until they made hard contact with the rifling and fire formed them without any stretching.

4. It would help you greatly if you had the "tools" to find out how long your chamber is and how short your new cases are.



5. You also need to adjust your dies so the shoulder is only bumped back a maximum of .001 to .002 when you full length resize your cases.







6. By using the die headspace shimming washers I have below you will never push the shoulder back too far.



What type rifle do you have and how old is the rifle, you might have a headspace issue "OR" you were very unlucky and purchased some "short" cases. The SAAMI manufacturing tolerances allow the 30-06 cartridge case to be .007 shorter than minimum headspace "BUT" I have found new cases as short as .012.

 

[popper]

My understanding of the long-seated-bullet method is that the case head is closer to the bolt, so shoulder is blown out more uniformly and less case stretch. The COW method could allow the case to be seated deeper, causing more case stretch instead of blowing the shoulder forward. Not the same for rimmed cases.

 

[bigedp51]

popper

Any time you fire form cases you want the case held firmly against the bolt face. Below is an example of a commercial .303 British cartridge being fired in a "long" headspaced military Enfield chamber.



To fireform my rimmed .303 cases I slip a rubber o-ring around the case which holds the case against the bolt face and also centers the rear of the case in the larger military chamber.



As you can see below the o-ring holds the case against the bolt face and when fireforming the case can not stretch in the base web area when fired.



Below the fireformed case now headspaces on the shoulder of the case instead of the rim and is held against the bolt face by the shoulder of the case on subsequent firings.



Below a 30-06 case with a exaggerated false shoulder to show how it would be held against the bolt face while headspacing on the enlarged case neck.



The simplest method of fireforming cartridge cases is seating your bullets long and jamming them into the rifling forcing the rear of the case to be held against the bolt face when fired.

NOTE: The reason I use the rubber o-ring method on my .303 cases is because these rifles fired cordite powder and have throat erosion and have no rifling in the throat to push against the bullets. (seating the bullets long will not do anything)

 

[popper]

The 'O' ring would also save those expensive projectiles.