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Pressure Signs

Old 02-08-2004, 05:48 PM
  #1  
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Default Pressure Signs

I have read alot about people seeing pressure signs. What are these so I will know when I start handloading.
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Old 02-08-2004, 06:36 PM
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Nontypical Buck
 
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Default RE: Pressure Signs

Two common signs are the flatness of the fired primers and growth of the case diameter just ahead of the extractor cut. The case can be measured with a precise blade micrometer and even .0005 growth is too much...back off!!!

Re: primer flatness:..look for loss of the radius in the corner of the primer. A newly installed primer had a generous radiun in the edge where it is in contact with the primer pocket.....if the pressure is high that radius disappears making the primer look very flat.

Another sign is a chronograph reading.....if you are shooting faster than factory loads you might want to rethink your load. Most factory loads are near maxed out and it can be unwise trying to improve on some of them unless you know that the factory loads are tamed......such as the 7MM Mauser and other cartridges.

After all this you still could be over max and not know it but these things will go a long way towards safe load development.

Read your loading manual carefully...some loads are specific for a particular gun and not to be used in other guns.....

This applies only to modern boltaction guns where the cartridge case is the weak link....It absolutely don't apply to leveraction guns such as the M94 winchester and Marlin 336 and a lot of other guns
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Old 02-08-2004, 08:33 PM
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Default RE: Pressure Signs

Most factory loads are near maxed out and it can be unwise trying to improve on some of them unless you know that the factory loads are tamed......such as the 7MM Mauser and other cartridges.
Many modern rounds such as the 7mmstw,and 300ultramag are loaded very mild by remington.Even 300wby rounds loaded by remington are loaded much milder than the norma loadings.

By the way I have measured many belts on factory belted magnum loads and several of them expanded by more than .0005" after one firing.I have seen 300wby factory loads that expanded .002" at the belt after one firing in a factory mark V rifle.
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Old 02-08-2004, 10:40 PM
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Default RE: Pressure Signs

I generally agree with vapordog. However, I have noticed that some primer cup runs tend to be of different hardness and tend to react differently to the same load(using same primers but a different batch) Similarly, some brands of primers are notably more likely to flatten than others at the same pressure. Measuring cases with a micrometer is pretty reliable and is what I primarily rely on for high intensity cartridges like wbys. With most standard rounds, ejector marks are a reliable sign. I will note that most of the different weatherby factory ammo I have shot in weatherby guns leaves a modest ejector mark. Also watch your grouping. Many guns will shoot best near maximum loads. However, clear overloads usually do not shoot as well. Always back off on your loads anytime you change components. Different brass, a different bullet even in the same weight, a different batch of powder and a different gun in the same chambering have all affected pressure. An author by the name of Bob Hagel wrote a couple books about big game loads (it's a good read) several years back. He actually encouraged reloaders to slowly work up loads to the point where they could actually see the signs of increased pressure. I believe his idea was it is quite educational, if done carefully. Hope this helps
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Old 02-09-2004, 11:44 AM
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Default RE: Pressure Signs

I found that while I'm reloading for my 300 Win Mag, that Federal primers will flatten out quite a bit, but Win, CCI and Remington primers don't at all.

This is with 200 grain bullets and exactly mid point between minimum and maximum powder load of IMR-4350.

After telling this to a local gunsmith, he commented that he liked Federal primers because they were very "soft." He said that because he thinks they just "fit" better in the pocket because of the softness.

(edited to add this question) Has anybody else found this to be true? The softness?
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Old 02-09-2004, 07:47 PM
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Default RE: Pressure Signs

I too love Federal primers, particularly 215s. They do appear to me to be softer and more prone to flatten under modest pressures. Weatherby factory ammo, which I understands uses federal 215, routinely are flattened to an extent that most reloading manuals would suggest is high pressure.
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Old 02-09-2004, 08:38 PM
  #7  
Nontypical Buck
 
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Default RE: Pressure Signs

I'll copy this direct from the Hornady Reloading manual:

SIGNS OF LOADS BECOMING EXCESSIVE:
1An increase in case head expansion as measured by a very accurate micrometer.

2. hard or sticky extraction from the chamber of the firearm.

3. Flattened primers (the rounded edges of the primer are now flattened, filling the gap between the primer and case head.

4. Cratered primers (primer cup material flowing into the firing pin hole)

5. Ejector marks on the case head.

6. Sooty gas leakage around the primer.

7. Enlarged primer pockets-in the worst cases with the primer blown loose.
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Old 02-10-2004, 08:36 AM
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Default RE: Pressure Signs

Vapodog,
Out of your 7 points copied out of the manual, only the flattened primer shows; IF I use Federal primers. NONE of the other signs (1,2,4,5,6,7) are there.

Now, if I use ANY other primer than a Federal, I don't get any signs flattening. So if the Federals flatten out, in your opinion, does that mean that my reloads are creating too much pressure?
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Old 02-10-2004, 09:54 AM
  #9  
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Default RE: Pressure Signs

Mainehunt.....all these indicators are simply that.....INDICATORS!!!
IMO the best indicator is to use a micrometer on the case immediately ahead of the extractor groove. Further if you are only seeing flattened primers and none of the other symptoms I'd venture a guess that you're all right. These are the signs folks have used for years short of pressure barrel equipment.

Further these signs don't necessarily mean the ammo is too hot...it could mean a flaw in the barrel or too long cases... Experience helps!!!
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Old 02-10-2004, 10:22 AM
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Default RE: Pressure Signs

deerhunter,
The primer is not a reliable means to indicate pressure.

Start 3 grains below the max in your reloading book.

Start you loads appx. .03 of the lands or if you have no way to measure just make sure they are not too close to the lands or your pressures will increase.
You can always tweak your loads for OAL later if necessary to improve accuracy. I have always been able to get excellent accuracy from loads well off the lands.

Work up .5 grains at a time, shooting 3 shot groups. Start by shooting the 3 loads with the least powder and progress to the loads with the most powder.

You will probably notice the recoil increasing as you go up.

Keep a close eye on the base of the brass after each shot.

As soon as you see a shiny spot on the bottom of the brass where the label is that is the extractor mark. Once you notice an extractor mark stop shooting, you have found your max.

Back off one full grain on your next reloads and you have a max load.
If you do this you should never get to the point that your bolt is sticky to open, but if you do you went way over and you are at dangerous pressure levels.
Keep the brass organized by how they were loaded.
If you notice any of the primer pockets are noticeable looser on your heavier loads you may want to reduce your loads another grain to get more reloads out of your brass.

If you change any of the components of your load start over.

Most of my reloads are up to 100 to 200fps faster than factory ammo.
Kind of the point of reloading.

I have used this method for 20 years, it is simple and it works.
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