Pressure sign question

[powdergun]

I observed the following on some loads.

1) very slight cratering around the firing pin mark
2) some primer flattening as compared to an unfired round. ( I see the same thing with mild loads as well )
3) Not extraction issues. The bolt opens and ejects with no issues.



The groupings on paper for this load very very good. My question is can I go with this load without worrying or am I pushing my luck ?

 

[stubblejumper]

You haven't mentioned anything that indicates excessive chamber pressure.

 

[powdergun]

I was reading and they stated that cratering and primer flattening were signs. What are some of the key pressure signs ?

If I'm not too hot on these loads then that is good news to my ears.

 

[CanuckWR]

Post a pic or two of your primers. You might just be close to the top end but not over it.

 

[stubblejumper]

Siight primer flattening is normal, slight cratering is usually a sign of an oversized firing pin hole in the bolt.

 

[6.5x55iswonderful]

Depends on the rifle, but it could be thin primer cup (try a different brand or magnum) or an enlarged firing pin hole that sometimes happens with a military type action.

 

[Boomer]

When you get into situations where you see shiny extractor marks on the case head, or when web expansion measures .001", that’s nature's way of saying you've gone as far as is prudent and you need to back off. I consider reading pressure from primer indicators terribly unreliable.

 

[BearClan]

I would strongly recommend getting a chronograph - Velocity is the most reliable indicator of dangerous pressures after a pressure gauge. If your velocity exceeds published velocities, you are almost certainly over safe pressures. Search the 24hourcampfire site (http://www.google.com/cse/home?cx=016407629494559605640:xponie3lspc) for "pressure" and "Muledeer" (name for noted gunwriter John Barsness) - this topic has been covered extensively on that site.

 

[John Y Cannuck]

When you see a truly flattened primer, you'll know it, there will be no doubt in your mind.
Look at the edges of the primer, if they are still rounded, it's not what most of us would consider flattened.
From what you have described, it sounds like you are well within safe bounds.

As Stubblejumper pointed out above, firearm condition is a primary reason for cratering, soft primers exist too. Try the same load with another brand.

Boomer is correct as well, primer reading can be unreliable, as I mentioned above, the manufacturers are inconsistent, one brand is softer than another, results may vary.

Hard bolt lift is generally caused by case flow into the extractor groove, this leaves that shiny spot. If you see that, BACK OFF.

It's not a perfect science, reading cases. There are many variables. For example, a load that was safe when you worked it up last December might be way too hot on a summers day.

 

[stubblejumper]

Velocity is the most reliable indicator of dangerous pressures after a pressure gauge. If your velocity exceeds published velocities, you are almost certainly over safe pressures.

Whose published velocities? Two or more sets of data using identical components and the same barrel length, can have published maximum velocities that vary by 150fps or even more in some cases. In that situation, whose data do you use as a reference point? If you are exceeding all available published velocities, I would be concerned, but what if you exceed the maximum velocity published by one source, but don't exceed the maximum published velocity published by another source?

 

[dero338]

if you keep using your brass long enough, and keep the same load you will get flat( even flanged ) primers
keep paying attention to the restriction when you seat them in the pocket
with the time, primer pocket gets little bigger and primer go in very easy and comes out easy too
at this time, just get rid of the brass before you get a blown out primer

sticky bolt lift can also mean rough bolt lugs or just a lack of lubrication

most sings can have differents causes, so it is good to investigate farther than just the over charge.

 

[powdergun]

From what you fellas are saying I think I'm good. The bolt lifts smoothly with little effort after the shot and no extractor mark. The cratering and flattening on the primer was very slight. I'll be careful but the load was jus too accurate to pass up.

 

[22to45]

I was reading and they stated that cratering and primer flattening were signs. What are some of the key pressure signs ?

If I'm not too hot on these loads then that is good news to my ears.

I have seen loads that flattened the primer completely, and nothing blew up and the bolt still opened, a bit hard on brass though, your load sounds fine,

 

[KDX]

Can you still get a bit of shiny extractor mark without any hard lift on the bolt? If the primers still look fine is it OK?

 

[22to45]

Every place the rifle touches the brass you can get a mark. Someone else here will have a more detailed explaination, but if you can use a case 5 times and the primers still fit tight your loads are not hot.

 

[stubblejumper]

I have seen loads that flattened the primer completely, and nothing blew up and the bolt still opened, a bit hard on brass though,

Not just hard on brass, quite likely hard on the gun, due to the excessive pressure.

If you see shiny extrusion marks, you need to back off the load. If the cases are extruding, the primer pockets will be getting larger. They may hold a primer after five firings, but the fit will be looser.