Case Stretch Question

[Ray]

Two weeks ago I used my new 223 load at a HP Service Rifle competition, Hornady 68 HPBT, Varget 24.0g, LC brass and WSR. I also shot a 600 yd load I used last year Hornady 75 HPBT, Varget 23.5g, LC brass and WSR or Remington 61/2.

After polishing the brass I checked them in a Dillon case length gage and found they were 0.008 longer than the gage. Primers are slightly flattened. Is this an indication there is a problem with the rifle or the load?

I also checked the fired shells from my son's rifle and found them to fit the case gage at maximum length. He used a different load, Hornady 68 HPBT, WCC844 (H335) 22.7g, LC and WSR. 600 yd load Hornady 75 HPBT, surplus 4895 23.2g, LC and WSR.

Thanks in advance for sharing your wisdom.

 

[ocabj]

I think the brass just needs to be trimmed. Did you measure the brass with a caliper? What's the length right now? What was the length of your brass before you loaded them and fired them?

Also, brass stretching is different from rifle to rifle.

 

[molonlabe]

During the firing process the case is pressed against the chamber walls. Since the brass has no place to go (it is stopped by the breech face) it will flow forward. If the case mouth contacts the front of the chamber (the point before the rifling starts, brass can be crimped harder on the bullet when the action is closed. (in the case of a bolt action this can be substantial) or the brass can flow during ignition. Either case will cause a spike in pressure to a dangerous level hence this is probably why your primers are flattened. There are no shortcuts to trimming, you need a trimmer and calipers. For me it’s one of the POA’s of reloading. I hear some good reviews on RCBS’s X sizer dies to keep the trimming down. If I can do it once it will save wear and tear on the brass.

 

[Jon Coppenbarger]

First if you are shooting that load and they are not close to being too hot from what you gave . What chamber do you have.
If it is a gi type chamber they are a little looser so you will get more expansion.
Now as far as the primer goes we do not recomend using 6 1/2 rem. as alot of folks have a problem with them flowing, blowing and causing jams and detroyed firing pins.
The most common primer used with 223 highpower loads is the remington 7 1/2 followed by CCI br4's or the winchester bench rest primers. and most folks are staying clear of the new winchester primers as they seem to sensitive and we are starting to see more slam fires using these primers. saw 3 slam firers over the last month and they all had the new winchester primers.

I am in the process of prepping my brass for the remainder of the season (I hope).
Here is what I do all my brass goes into the tumbler.
After it comes out of the tumbler and that was four large tumbler loads I set down and look at every single one. what I am doing is sorting my brass and it this time went into 4 different piles.
#1 bad piece like obvious damage or someone else brass
#2 winchester brass that was used at 600 yards and was new before it was fired
#3 winchester brass that was used for NTIT matches and practices.
#4 the rest of them which acounts for 90% of whats left goes into one pile and these were all lake city brass from 1994 up and did find about 10 were before that and knew they were not mine.

I worked on the winchester brass for long range first.
They got run threw the sizing and depriming die and set the shoulder back to my diminsions for my rifle.
Then ran them all threw my giraurd trimmer set to my specs that trims, inside and out chamfers at the same time, took about 15 minutes to run the 150 pieces threw.
Then put them on the rcbs case prep center and ONLY ran the primer pocket uniformer and then the flash hole deburrer.
After than they all got hand primed with CCI br4 bench rest primers.
Next week they will get hand weighed with my load of vithivouri n140 powder and set up for the camp perry and put away with smk 80's on top of them.

What I do on the bulk lake city cases is use my case trimmer on each one of them as it helps me locate some that do not seem right and either could be a problem or were not mine.
since there will way over 1,000 of them I will run threw , First they all get run threw the die and set them all up the same way with the shoulder set back to my match specs.
Then they are run threw the giraud trimmer, It is very fast and with gloves on 500 a hour is taking it easy and since I do this every time most all of them need very little trimming and if I find one that takes alot of trimming I toss it out because it was not mine.
I also know that I do the flash holes on all of my rounds with the exception of new brass that I fire once in rattle battle so I will also check that as it should not cut any brass out in this process and if it does then it was not my round either.
Does all this sound crazy, maybe but at the reional, states and nationals I always use the best I can within reson.

 

[Grump]

Are we all talking case OAL base-to-mouth, or headspace length as shown with a Wilson gage? Case mouths too long, crimped, and then chambered to extend a tiny bit into the throat will pinch the bullet on firing and boost pressures dramatically.

Long case headspace after firing min-headspace ammo in a longer chamber can result in what looks like pressure-flattened primers because they back out on firing, then get slammed flat & mushroomed when the case stretches/slides back to the boltface. not-so- , but case life can be as low as 2 reloadings before separations start happening.