Does anyone NOT bump shoulders on FL resizing after initial firing on virgin brass?

[Winny94]

Got to measuring and asking some questions from more experienced guys. I always assumed in normal circumstances (ie. not fireforming a wildcat, in spec chamber, etc.) the brass filled the entire dimension after the first firing. Now im seeing some info that says that may not be true. So with that in mind, my logic is saying if im basing my shoulder bump off of the first firing measure, I may be oversizing.

 

[Rocketvapor]

Over thinking?
Virgin brass is often short to fit in everything. .003"?
Once fired will expand but may still be a tad short. .001"?
Second fired will be closer, but still a little short due to shrinkage.

Take second fired, size but don't bump, check in chamber. If tight Bump back .001" check in chamber.
Don't bump more than virgin brass.

 

[Walt Krafft]

What kind of rifle and what purpose? Boltgun would be different than an AR. Target rifle different than hunting rifle. Rapid fire or slow fire?

 

[T-shooter]

On a bolt gun I use a fired stretched case and bump it back just enough so it chambers without much extra force, and use that for my baseline. Usually none will go back over .001".

 

[Rocketvapor]

Decide what headspace/bump you want based on your usage.
But base the bump on the headspace of the 2nd fired brass.

 

[D-4297]

I tend to agree with Rocketvapor regarding new brass for the reasons given . SAAMI chambers are cut all over the place , and precision chambers tend to be specific , towards the tight side . You may even find three firings are necessary to get full "expansion" , to be able to obtain correct bump-back . Check some fired cases after second firing , and see if they will go in the chamber and have normal , or minimum pressure on bolt closure . No pressure on closing , with slight pressure on bolt lift is the general goal .

 

[CharlieNC]

Partially insert a primer in your new brass and chamber it, letting the bolt insertion complete seating the primer. Measure to find your zero headspace to determine your sizing target, .002 shorter as desired.

 

[JMayo]

After reloading them a few times you'll come to know the size of your chamber.

 

[Longtrain]

Since my main two rifles are a Dasher and a 223AI, they both need fire forming, so I guess my situation is a bit different then a standard cartridge.
That being said after FFing I still measure them and run them through my dies. My chambers are cut with my reamers, so I know what they should measure after firing and resizing. I just measure them and check my notes. If they are a bit under, maybe .001 or .002 at most, I’ll just adjust the die to skip the shoulder and basically just do the necks.
After a second firing they need a small bump, minimal .001 or .0015.

 

[K22]

Very interesting question and answers. I always assumed after the first firing that the case would expand to fill the chamber. I bump back .001" after first firing but I may do some more measuring and testing after reading these posts.

That's what's great about this Forum - always something new to learn.

 

[jepp2]

the brass filled the entire dimension after the first firing

Only if they are significantly overpressured. I try to bump the shoulder FORWARD after the first firing. I'm trying to get my datum to case head the same as soon as I can, and they are all over the place (usually). After a few firings of moving some forward, and leaving others alone, they become more consistent. BUT, you need to know the datum to case head where you can start to feel the bolt close on the brass.

 

[JEFFPPC]

Got to measuring and asking some questions from more experienced guys. I always assumed in normal circumstances (ie. not fireforming a wildcat, in spec chamber, etc.) the brass filled the entire dimension after the first firing. Now im seeing some info that says that may not be true. So with that in mind, my logic is saying if im basing my shoulder bump off of the first firing measure, I may be oversizing.

Pm sent

 

[Richard Coody]

Got to measuring and asking some questions from more experienced guys. I always assumed in normal circumstances (ie. not fireforming a wildcat, in spec chamber, etc.) the brass filled the entire dimension after the first firing. Now im seeing some info that says that may not be true. So with that in mind, my logic is saying if im basing my shoulder bump off of the first firing measure, I may be oversizing.

Never

I just.neck size until a piece of fired and unresized brass chambers tight. Then i set up the shoulder bump on my die just enough that it chambers easily.i lock that die down and we are ready to size the rest.

 

[Rdlningcltchdmpr]

Got to measuring and asking some questions from more experienced guys. I always assumed in normal circumstances (ie. not fireforming a wildcat, in spec chamber, etc.) the brass filled the entire dimension after the first firing. Now im seeing some info that says that may not be true. So with that in mind, my logic is saying if im basing my shoulder bump off of the first firing measure, I may be oversizing.

Yes your right, you really need to use a virgin brass as a guide. As in never size cases below virgin brass dimensions. I ussually bump shoulder after two firings.

 

[NorCalMikie]

If the fired brass will rechamber with little effort on bolt closing, loads it up and shoot it again.
If the bolt is tight, check full length resize and see if it fits.
Still snug? Bump and reload.
DON'T resize any more than needed.

 

[BoydAllen]

Generally, first firings do not take a case out to its maximum shoulder to head dimension. For that reason, if a shooter does not load at the range or have a neck die, so that he can produce a tight case before proceeding, I recommend setting the FL die to give the same measurement as the fired case, and then trying it in the rifle. If if fits you should be good to go. Just remember that you either want to remove the primer before you measure the fired case, or use your priming tool to shove it down out of the way.

 

[JSH]

Running on “feel” I see no mention of over coming ejector and extractor giving a false feel.

 

[338 dude]

Got to measuring and asking some questions from more experienced guys. I always assumed in normal circumstances (ie. not fireforming a wildcat, in spec chamber, etc.) the brass filled the entire dimension after the first firing. Now im seeing some info that says that may not be true. So with that in mind, my logic is saying if im basing my shoulder bump off of the first firing measure, I may be oversizing.

I believe you would be oversizing usually takes 2 firings and sometimes 3 to need to bump

 

[Chuckhunter]

Running on “feel” I see no mention of over coming ejector and extractor giving a false feel.

JSH, I can only speak to what I do. My Borden BRM is a bottom eject so therefore no ejector and the bolt has a sako style extractor, so I slip the case head under the extractor, again pressure is eliminated. When I had a side eject, I removed the ejector and spring and slipped the case head under the extractor. This procedure gives me exceptional feel and repeatable measurements.

 

[golong]

I always check, but it is extremely rare that the shoulder needs to be bumped after the first firing. I had a conversation with someone at Redding maybe 18 months ago about how I could go about eliminating an inconsistency I was seeing somewhere. During that conversation I was told that it is not terribly uncommon to take more than 2 firings to fully expand brass.