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Old June 20, 2011, 11:49 PM   #1
krmcne
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Too Much Pressure?

No matter how much powder I put in these .243 cartridges, I always get flattened primers. I have a Remington 700 with a 26" bull barrel and I'm shooting 75 grain VMAX bullets, WLR primers and using IMR 4895 or 4350 powders. I've seated my bullets so the overall length is .015 from touching the lands. I just shot the minimum load recommended in my reloading manual today using both of the above powders and still got flattened primers. Am I missing something important here?
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Old June 21, 2011, 12:02 AM   #2
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Got pix?

Headspace correct?
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Old June 21, 2011, 12:37 AM   #3
Jim243
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Quote:
Am I missing something important here?
Jimbob86 is right check your rifle's headspace.

Jim
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Old June 21, 2011, 01:11 AM   #4
HiBC
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I'll expand a bit on the headspace suggestion.When the firing pin hits the primer,the cartridge is driven forward.If there is space between the case head and the bolt face,the priomer will back out of the primer pocket till it hits the bolt.You might be able to see that by popping a prmed empty case in your rifle.When the powder ignites,and pressure goes up,the cartridge case head stretches back to the bolt face,and at this point,the primer gets flattened.
Now,sometimes a rifle has excessive headspace,which can cause all this.Real often,a reloader,in good faith,reads the die instructions that say to bump the shellholder against the base of the die.That is often not a good idea,as the tolerances of everything work out.The die will often set the shoulder back too far,creating a condition that resembles a rifle with excessive headspace.Its just a die adjustment problem.In a bolt gun,I like to get .002 shoulder setback from a case fired in that rifle.
There are tools and methods to measure this.There is a Hornady caliper attachment,there is an RCBS precision mic,and there are bushing case gages that can be used with calipers.Good luck!
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Old June 21, 2011, 04:04 AM   #5
mehavey
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Minimally resize a set of a half-dozen cases to where they just allow the bolt to close.

Tell us how the primers appear after firing those loads....
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Old June 21, 2011, 04:53 AM   #6
t3tikka250
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Im not as experienced as some of the guys on here but when i had flattened primer issues i bought a new batch of the same primers and the problem was solved.

Could just be a bad batch of primers.

Just my 2 cents.
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Old June 21, 2011, 06:14 AM   #7
mehavey
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Protruding primers after firing a low-pressure (minimal) load is a classic sign of excessive headspace. They then get hammered flat by case stretch.
It's easily solved by adjusting the amount of sizing to just fit the chamber dimensions.
(Thereby also dramatically extending brass life.)

Last edited by mehavey; June 21, 2011 at 07:39 AM.
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Old June 21, 2011, 07:26 AM   #8
Jim243
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The easiest way to check a rifle for headspace is with a no-go gauge and a go gauge. I you don't want to buy the gauges then take it to your gunsmith, it is a 30 second process. If the rifle is OK then it is where you are setting your die and buy one of these:





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Old June 21, 2011, 03:58 PM   #9
TXJohn
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How many times has this brass been fired? Take one of your fired cases and see if the bullet will slide into neck easy if not case necks are to thick. I have had a problem with my 243 necks getting thick after several firing. Just my opinion.

John
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Old June 21, 2011, 04:36 PM   #10
Zildjian
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Too much pressure

Being re-loads and having problems , have you tried firing factory ammo and tried to see if you get the same results as your re-loads. Might try that
and see what happens before shelling out more money. Once fired in your rifle
you will not need to FL resize again being fireformed to your chamber. Stay off the shoulder. I would try factory ammo 1st and then go from there. Just
my 2 ยข
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Old June 21, 2011, 05:09 PM   #11
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Neither of the Powders that you're using are optimol for the 75 Gr. A-Max . 4350 is too slow and 4895 is too fast IMO ! I have gotten great accuracy with that Bullet and IMR-4064 . Are you using Federal Brass by any chance ? You may very well have a Headspace issue as others suggest .
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Old June 21, 2011, 06:27 PM   #12
mehavey
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The following powders give you best potential combination of velocity/fill/burn w/ the .243Win/75gr A-Max for max working (55,000psi) pressure in a 24" barrel:

3,418 Norma MRP
3,412 Alliant Reloder-25
3,347 Ramshot Hunter
3,339 Accurate 4350
3,321 IMR 4831
3,311 Hodgdon Hybrid 100V
3,291 Accurate 3100

YMMV of course.
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Old June 23, 2011, 06:57 PM   #13
krmcne
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I know exactly what is happening. I've got my resizing die screwed in too far as suggested above. I did notice that the primers were backed out of the pockets slightly. So does this actually mean that I'm getting too much pressure or am I just flattening primers? And is it safe to shoot the brass that I have already sized this way? You guys are great. Thanks for your help!
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Old June 23, 2011, 08:07 PM   #14
mehavey
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What powder/bullet loads are you running?
(Minimum loads per the manuals usually mean anywhere from low 30's to mid 40s Kpsi -- low/moderate pressures)

Combine that w/ a case that's sized too short and you have protruding primers when they don't stretch (as w/ sizing lube left on case), and flattened primers when they do (dry case locks into chamber walls up front and the rear then stretches to meet the bolt).
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Old June 23, 2011, 09:37 PM   #15
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I have been developing loads with lubricated cases for at least a decade now.

I noticed that when I shot lubricated cases in my M1a's, I got rounded primers. Dry cases gave me flattened primers. Obviously combustion pressure is the same, so I figured out that with lubricated cases, the case and the primer slide back to the bolt face at the same time.

So, I started using lubricated cases in load development. When primers start flattening for real, I know pressure is going up.

Primer flattening is just one indication of pressure and unfortunately it is an unreliable indicator.

Positive indications of too much pressure are leaking primers, blown primers, sticky bolt lift, and brass flow into the bolt face. If you get these signs you have exceeded safe operating pressures. Brass flow around the firing pin is not always a positive indication as one manufacturer has redesigned their rifle to do this. Apparently it provides a better gas seal around the firing pin. Since I also use a chronograph in developing loads, I believe that if my loads exceed published velocity values, regardless of primer or bolt lift, then I am exceeding reasonable pressures.

If your brass ever looks like this, it is way too hot!

These rounds were fired in .223 service rifles at Camp Perry. They have all the indications of excessive pressures. Except for bolt lift. AR's extract ammo without any assistance from the operator.

AMU long range brass.


USMC Rifle Team long range brass

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Old June 24, 2011, 02:39 PM   #16
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krmcne: I can't tell you whether it is safe to shoot your loads.There are too many variables.And,I'm not THE guy to tell you.
Here is something more to work with.
As the powder ignites,and pressure goes up,The case expands and it grips the chamber wall.The forward part of the case does not slide back.What happens is your case stetches back to the bolt face.Unfortunately,it does not pull the stretch from the full length of the brass.The stretch occurs at approximately the chamber mouth.As the brass is pulled longer,it gets thinner.
The visual part of the thinning occurs inside the cartridge case.Some reloading manuals discuss case stretch and stretch rings.Look.Even if you have only loaded this brass a couple of times,hacksaw one lengthwise and you will likely see the brass has thinned in a ring about 3/8 to 1/2 in fwd of the base of the case.
There is a way to use a bent paper clip to feel for stretch rings as a brass inspection procedure.
A noticable stretch ring is a weak spot in a bad place.The brass is all that keeps the 50,000psi hot gas where it belongs.
The shoulder of a 243 establishes the headspace.You do want your die to set back the shoulder of a round fired in your rifle about .002.That will allow you to easily close the bolt,yet minimize case stretch.
Once you start that,then your primers speak a different language.Then you can get a little nervous about flattened primers.
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