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pressure

So, I ran a ladder and didnt see any pressure signs. picked the tightest 3 and ran a 3 round group 41.9, 42, 42.1. These were 2706, 2712, 2723

2 fire Lapua, trimmed and full length sized
Berger 140 Hybrid seated 2.80
H4350
fed 210

Now all of a sudden my brass looks like this. There was no ejector marks when I ran these same loads through the ladder..  ?????

Is this my pressure limit, doesn't seem right to me, but being new to precision loading I could use some advice. These were my tightest groups and I sure dont want to start loading the seating depth out on these if this is the top. Just seems funny to get the marks now and not during the ladder.
Sean 
Bergara HMR, Bergara LRP

Re: pressure

Reply #1
I find it tough to believe you're pressured out. Brass oversized creating short headspace, case slamming into bolt face on firing maybe.
Dave

Re: pressure

Reply #2
H4350 is supposed to be temperature stable but was their any difference in temperature between shooting sessions?

Re: pressure

Reply #3
Hmmm.  Looks a lot like pressure.  According to Berger you are very close to max load.  According to Hodgdon and Lee's Modern Reloading you are 2 grains over max. The Hornady load data suggests you are about a grain over max.  I don't know why those pressure signs didn't show up during your ladder test.
Experience enables you to recognize a mistake every time you repeat it.

Re: pressure

Reply #4
I assume you used the same brass doing the ladder. ? How much did you push the shoulder back when you fl sized. I'm with savage guy with them speeds you shouldn't be overpressured. But it sure appears ya are.
Grant

Re: pressure

Reply #5
Before you panic, you might give your bore a good cleaning, paying close attention to any carbon buildup just ahead of the throat.

A good brushing and then wet/dry patches until clean.   Then take lightly oiled patch and insert it from the muzzle end.   Pay attention to whether or not the patch gets more difficult to push as it approaches the throat area..  If so, you have a carbon ring that's built up and you're going to need some work with Flitz or Simichrome on a tight patch to scrub it out.


As for the primer marks, what rifle are you using.   The cratering on the primer is quite common with factory bolts, especially Remingtons.  They chamfer the firing pin hole to provent "blanking" where a round bit of primer metal is literally cut out of the primer face by the sharp edges of a firing pin hole when the pressure builds behind the primer.  With most loads it's considered false cratering.    As for the ejector mark, bumping shoulders back too far can make those appear with even mild loads.

US Army 1965-1972

Re: pressure

Reply #6
You shouldn't have any pressure signs at that vel.  Your speed seems a bit slow for the powder weights.

What rifle, barrel length, how many rounds down barrel.  What brass prep did you do?  What is the length of your brass?

Re: pressure

Reply #7
That's why im so confused, I knew I was at the top of the load looking at different manuals but with my velocities down I didn't figure I was there yet. The temperature difference was 10 degrees higher today. The brass was the same brass I used in the ladder and the sizer die was set the same. I didn't actually measure the bump but was the same. Bore was fresh cleaned before each test, then fouled with 3 rounds of FGMM which shoots .5 and under in this gun. Handload groups were .6 and under with one called flyer. SDs were under 10 and ESs were 18 and under All of my brass today showed ejector marks. No stiff bolt and walls looked fine. All brass annealed before each reloading. All loads check on two different scales. 

Bergara LRP

The only difference was I fired an extra 2 fouling rounds to verify my zero on the new Viper PST.

42 rounds down the pipe not counting todays
24 inch barrel
trim  1.910

Brass prep as follows, same everytime.

decap with a Harvey
clean pockets by hand
tumble one hour
Anneal
full length Size
Trim to 1.910
chamfer/ debur,
Interior neck clean with nylon brush
Hand wipe and inspect each round.
Prime with a lee hand primer so I can feel each seating.
Each round trickled and double checked during load development.
Bullets seated to SAAMI.

Primers still looked good other than the Bergara crater. The edges are round, No blown primers, Just the ejector marks and slight swipe on the flat, if that means anything.



Sean 
Bergara HMR, Bergara LRP

Re: pressure

Reply #8
One more thing I forgot. This is a new box of Berger 140 Hybrid. I used the last one from the old box on the ladder.
Sean 
Bergara HMR, Bergara LRP

Re: pressure

Reply #9
did you find the lands with one of the new bullets to see how much jump you have with a 2.800 coal ? also its always a good idea to see how much your bumping the shoulder back...
Grant

Re: pressure

Reply #10
No, I didn't check, I just assumed they would be the same or ridiculously close due to their reputation. I dint have the exact numbers with me but there is a good jump on them if they are the same as the old box.

Is it better to fire form them and neck size after?  Im just learning this stuff so thanks for the patience.
Sean 
Bergara HMR, Bergara LRP

Re: pressure

Reply #11
first thing I would do is make sure I wasn't jamming them into the lands... if I wasn't then I would check and make sure I hadn't pushed the shoulder back too far... have you got the tools to measure this stuff ?  measure the base to shoulder on a fired round and then one you have full length sized... .002 bump is what most want... if you have it pushed back to much it may be doing what 6.5 savageguy said ...
Grant

Re: pressure

Reply #12
Sean I don’t think a variance in bullet jump could create what you are seeing. A more aggressive shoulder bump surely could. You said you didn’t change your die setting. I may have slipped when you reset it in your press. Using a different shell holder between the two batches could also create a difference in amount of bump back.

Re: pressure

Reply #13
I loaded two sets of 3 round groups so I still have 9 loaded I didn't fire after I saw the marks. Ill measure between the two when I get off duty. Is there a special tool needed to measure or just calipers.

I was just reading on shoulder set back and I think I DO NOT have them set right. I just followed the 3 line settings on the manual that came with the dies. Well, time for some more studying.
Sean 
Bergara HMR, Bergara LRP

Re: pressure

Reply #14
yeah you need a hornady headspace comparator to measure this...you can get them on amazon or midway or about any where that sells reloading supplies... comes in a set with 5 different comparators... you about need one to see how much your pushing the shoulder back..
Grant