primers and signs of presure how to tell

[retiredcpo]

ok more questions inmy 7mm rem mag saga
I thoguht I knew what to look for as far a signs of presure in the primers
but thought I would get the opinon of those in the know here.
I can not tell the differance between these two rows of cases
there is a full 2 gr differance between the two.
they all shot good I did not have enough loaded to get drop numbers yet I wanted to check the presure fisrt the load some more to get drop numbers latter.
What do you guys think of these primers?
Thanks Retiredcpo

 

[Chas1]

They're not looking flattened to me. Any primers loose?

 

[ICANHITHIMMAN]

Cheif

They look just like mine so if your doing it wrong then so am I.

 

[retiredcpo]

nope nothing loose strange or out of the ordanary
I had a over pressure incident with a differant load
this load is shooting good but very slow(dicussed in my other thread0
So im upping the charge slowly
I stopped at 63 gr of rl22 2 gr above where I was
I can not see any differance in the primmers
Im hopping to shot 25 more rounds tommarrow
BTW when I shot those last rounds it was over 80 deg out side and no shade.
retiredcpo

 

[Miller Outdoors]

The bottom row all look fine. The top row, the first one looks fine, but the second and third rounds appear to show cratering. As I've always understood it, that cratering is a sign of excess pressure.

 

[winmag]

The bottom row all look fine. The top row, the first one looks fine, but the second and third rounds appear to show cratering. As I've always understood it, that cratering is a sign of excess pressure.

+1 thats exactly what I saw. However the edges of the primer are still rounded, so more pressure? yes. Too much? no IMO, not yet.

My warm loads crater primers, my hot loads crater and semi-flatten primers, and my ''Hmm, I wonder how fast I can make this thing go'' loads crater and pancake primers. While doing load development, I load all of mine up to where I can see pressure signs and back off to the most accurate load. At least I know where Im at for load vs pressure that way. Just be carefull tho, cause you can go from ''semi-cratered'' primers to ''OH CRAP'' in a hurry, then again sometimes it takes a while.
Example
Load development for 270wsm/140NAB/RL-19/FED215M
Started with 60gr and went up to 64gr in .5gr incriments. 62.0gr was most accurate (.3??) so thats what I settled on. I may have been able to push them to 64.5 gr, but the pressure was excessive at 64, and the accuracy was already going (.8??) so why bother. But I did learn where my aprox pressure ceiling with that powder/bullet/primer/seating depth, and rifle combo was. All of wich is noted and archived for futre referance, So now Im back to keeping notes only on the 62gr load.

 

[retiredcpo]

Miller
Thats very interesting.
I think its a conbination of two things you are seeing
the angle and quality of the photo
the top row is the 61 grain load and the bottom row is 63 grains
so the bottom row is the hotter load.
If you look closley you can see it on all of them.
All rounds fired by this gun get that small ring around the firing pin dent.

 

[kiwi3006]

Cratering of the primer is not as good a pressure indicator as flattened primers. With a lot of rifles the firing pin fit in the "hole" is sloppy so even a lower pressure load will show cratering.

With a bolt with an ejector in the bolt face you will see a shiny mark on the case head with higher pressure loads. The brass is forced back into the ejector hole and then sheared off when the bolt is opened. This should start happening just before sticky bolts and difficult extraction.

Velocity is also a good indication of pressure. Generally equal velocity will equal pressure (with the same powder).

If a loading manual says 160 accubond, 70 gr H1000 will give 3000 fps with 60,000 psi and in your rifle160 accubond, 70 gr H1000 gives 2900 fps you will be less than 60,000 psi.


I might have opened a can of worms here, feel free to disagree.

Stu.

 

[retiredcpo]

stu
makes sense to me
I have read else where vel =pressure
but since i dont have access to a chrono I have to look at the primers then get drop numbers out to 500 0r 600 yards then check the data against a calculator to come up with the vel.

 

[Clark]

If the primer pockets get loose or the primer pierces, then there is too much pressure.

 

[Rimfire]

What brand of rifle or is it custom. Just a pin crator wont tell you much if anyting like stated a loose fire pin fit will crator on most loads. A custom rifle with min head space doesn't show much in the primer area also, other than the rounded edge going away the primers dont flow like often seen in custom rifles.

I would look at everything .

Crony
Primer flow
Primer crator
Ejector mark (depending on rifle
Measure cases just infront of the belt

Put it all togeter and you will get a much better read .

 

[retiredcpo]

Rimfire
Its a off the self remington sendero in 7mm remington mag.
I was not really looking at the pin crater I have seen that on every bullet this gun has shot so I kind of over look it now.
Im looking at the edges of the primers and the depth of the pin crater (thinking high pressure would push it back out)
have not seen any extractor marks.
What would a measurement of the case tell me?
would not all cases fired swell to the chamder the same?

 

[Rimfire]

My 300 win sendero showed false signs of high pressure with factory loads. Cratored primers with a lot of flow, no ejector marks or excessive growth in the case web. Your primers look fine just look for all the signs and put it all together. Look across the head of the case for the shine of the ejector mark.

 

[Rimfire]

I've shot a lot of R-22 mostly in 300 Win 6.5-284 and now in 338 Norma. Some thing you might find, A little dirty, temp sens, and varies lot to lot (at times) BUT accurate and gives FPS that often times others wont. I hate to love it.



I work up all loads in the summer when useing R-22. My 300 Sendero liked to run a hot load. I've seen hot loads worked up in the winter cause problems on hot summer days