Can brass shrink after firing, depriming, and resizing??

[jam1e]

As per the heading folks. I'm after some constructive advice concerning reloading my .223 Rem, with Remington brass for a 1 in 8 Tikka T3.

Either I'm going mad or some of my brass is shrinking!??

Is it possible for brass to shrink rather than stretch after firing, resizing and measuring again? I'm using a "Clarke" vernier, (which is accurate and consistent) with a Hornady comparator, which is accurate and consistent most of the time, if left as originally mounted for that batch of reloads. Although I appreciate their not as good as could be, but I do make sure they are flat on the vernier fingers.
Firstly, after de-priming and where possible just neck sizing, I always TRY and trim my brass back to 1.747".

However, before and after prepping, the brass always seems to vary from 1.750" down to 1.744".

Now if I just reloaded as is, with varying length brass from 1.750" to 1.744" surely this would affect pressures and distance from or to the lands???

Also would this make much of a difference in a consistent and accurate P.O.I from 100 yards, out to 250 yards?
I appreciate consistency is one of the keys to accuracy. And I've read a few posts stating that I should cut all my brass to the shortest length. But should I really be cutting them right down to 1.744"!!? Would this be a problem? Just to add that this wouldn't be a problem with powder compression, and the powder loads are the same, 25.1 grains.

As a side note, I do have around 200 pieces of once fired PPU brass, would I be better with that, as apposed to the Rem brass??)

Cheers folks.

Jamie

[Underdog]

Rem brass does seem soft and not so consistent as it use to be.

If your groups are good for you don't worry about the brass length for that small amount, if you are competing weigh each case and batch them.

 

The case length won't upset the seating depth, however and crimping if used will vary.

 

The cases may of filled out to your chamber and so shorten this time. Next time they should grow some.

 

Nowt wrong with PPU brass.

 

U.

[kent]

Just read up about what actually happens to the brass on firing in the chamber, were distance from the rifling is measured as a datum and the effects of firing an over long piece of brass. Then how brass should be correctly FL sized and all will become much clearer

[seeker]

 

1. If your measure is accurate to +/- 1 thou" them that is almost your variation accounted for...

2. Since you only trim neck length then internal powder space should not vary.

3.COL is base to tip .. or for more consistency base to ogive for distance to lands and case length is not part of this.

4. I tend not to trim new cases ... Just check tolerance and re-check in use.

5. Yes brass can shrink (or grow) if left in a dark place for a while ... its "spring back" and is one of the properties of brass that makes it suitable for the job. When its gone anneal or bin.

6.PPU is fine.

I had a batch of Rem.P cases for an x55 ... They was ( ××××), others may have better luck with it?

[jam1e]

Cheers folks.

Jamie

[jam1e]

Just read up about what actually happens to the brass on firing in the chamber, were distance from the rifling is measured as a datum and the effects of firing an over long piece of brass. Then how brass should be correctly FL sized and all will become much clearer

Kent,

Rather than me trawling sites, have you a decent link you know of that you could post up?

Jamie

[seeker]

Problem with mixing and matching info from different sources is that it can be ... Well different.

EG. I use '1 book /1 Calibre' and comparing the various manuals min trim length on an x55 varies from 2.145 to 2.157.

Being nearer to Europe than the US I just use the Lapua data and shoot ... it probably makes no difference except being the longest I throw away less brass.... bargain.

6mmbr.C is a sensible site that had plenty of links to videos of bullets, brass and itty bitty groups at the edge of the known world.

As Kent said ... If your groups are good for you then go with it and you're not introducing more variables.

Edited May 27, 2014 by seeker

[jam1e]

Kent,

Rather than me trawling sites, have you a decent link you know of that you could post up?

Jamie

Now sorted.

[Bewsher500]

simple answer ..."Yes"

 

think of the volume of brass than makes up a case as a liquid

everytime you squeeze it to size that liquid has to go somewhere...its why you are trimming. it has either flowed forward on firing (an issue with some case designs) or has been sized forward in the die)

 

your FL sized and trimmed brass is smaller than chamber, when fired in a case design like the .223 there is less flow forward and the case is expanding to fill the chamber

brass has to come from somewhere

 

 

measure then OAL of the case before and after sizing

 

or stop measuring, neck size until you find an issue and get out shooting

[Amazed]

simple answer ..."Yes"

 

think of the volume of brass than makes up a case as a liquid

everytime you squeeze it to size that liquid has to go somewhere...its why you are trimming. it has either flowed forward on firing (an issue with some case designs) or has been sized forward in the die)

 

your FL sized and trimmed brass is smaller than chamber, when fired in a case design like the .223 there is less flow forward and the case is expanding to fill the chamber

brass has to come from somewhere

 

 

measure then OAL of the case before and after sizing

 

or stop measuring, neck size until you find an issue and get out shooting

 

I like the last bit

 

Do you know how to measure your chamber length Jamie ?

[jam1e]

I like the last bit

 

Do you know how to measure your chamber length Jamie ?

I think I may have been told before, but I don't recall?

Please explain

Jamie

[Amazed]

I think I may have been told before, but I don't recall?

Please explain

Jamie

http://www.varmintal.com/arelo.htm#Chamber_Length

 

You can get the plug guage if you like.

I just did the poor mans guage.

Went for the average of 5.

some good info in there for general loading.

 

Then you can spend more time shooting and less time trimming brass

 

Karl.

Edited May 30, 2014 by Amazed

[fieldwanderer]

I had some remington brass that appeared to have been sized wrong - i.e. too short; soo many failed to fire, I binned 'em. From other people's experiences, seems it's not worth bothering with.

 

I've been using ppu and am very happy with it for the price, I'd like to move over to lapua or similar but don't really see the point - I shot two 5 shot groups earlier at 300yds, both were under 1.5" (3mph wind) and I can't see it getting better without spending big money on a scope.

 

Not sure if anyone else mentioned it but my case trimmer won't fit into a sized case, I don't know if there's a right and wrong but I assume it's considered normal to trim brass before re-sizing or they'd make the pilots smaller on trimmers

[Amazed]

I had some remington brass that appeared to have been sized wrong - i.e. too short; soo many failed to fire, I binned 'em. From other people's experiences, seems it's not worth bothering with.

 

I've been using ppu and am very happy with it for the price, I'd like to move over to lapua or similar but don't really see the point - I shot two 5 shot groups earlier at 300yds, both were under 1.5" (3mph wind) and I can't see it getting better without spending big money on a scope.

 

Not sure if anyone else mentioned it but my case trimmer won't fit into a sized case, I don't know if there's a right and wrong but I assume it's considered normal to trim brass before re-sizing or they'd make the pilots smaller on trimmers

I trim mine after I have sized if I need to

[Bewsher500]

I had some remington brass that appeared to have been sized wrong - i.e. too short; soo many failed to fire, I binned 'em. From other people's experiences, seems it's not worth bothering with.

 

I've been using ppu and am very happy with it for the price, I'd like to move over to lapua or similar but don't really see the point - I shot two 5 shot groups earlier at 300yds, both were under 1.5" (3mph wind) and I can't see it getting better without spending big money on a scope.

 

Not sure if anyone else mentioned it but my case trimmer won't fit into a sized case, I don't know if there's a right and wrong but I assume it's considered normal to trim brass before re-sizing or they'd make the pilots smaller on trimmers

 

 

bin it or get it sanded down

the whole point is to size and force the brass where it needs to go then trim

 

trim before sizing and then size and all your cases will grown/shrink etc at different lengths...may be very small but kind of makes the trimming pointless