Reading Primers???

[davkrat]

I posted some photos of my primers before with the 150gr ETip loads. I seem to get slightly cratered primers regularly at what seem like safe loads based on charge and velocities. Someone suggested I may have a worn firing pin. Rifle's a few years old with several hundred rounds through it. Here are some photos of the primers from the loads I recently shot trying to compare my standard Varget load with H4895 and CFE223. The CFE223 got higher velocity at what seems like lower pressure. The shoulder of the primers seem less flattened with the CFE223 but the cratering is more pronounced? Never had anything that looked like this with other guns and loads. I can't seem to get anywhere near the suggested loading manual velocities and the increases in velocity were pretty small as charge increased. Any help or suggestions appreciated.

 

[g0rd0]

reading those primers can be akin to Hodinie and Merlyn the majician. Not trying to be mean or arrogant but, load the same powder and primer in the same brass with differant brand of bullet with same weight. Now compare and see what you get (useing the same rifle of course), it may just be that the primers you are useing have the smallest of differance in thickness of metal. Or the primers may have been a little hot with the solution in that batch.
There are just too many varribles that we have no control of. Wich is why you always use published data, confirm and approch max loads with caution.

 

[davkrat]

Thanks. That's what has me scratching my head. The primers are not totally flat but they show that ring around the firing pin. Not sure if that is from pressure or just the gun. These are all well below max for published loads. I did a couple of the exact same mid level load with 150gr BTips and we'll see how they compare.

 

[barnesuser28]

Your cratering is coming from an undersized (in diameter) firing pin, causing some primer material to move into the space between the firing pin and the hole it comes out of. Doesnt harm anything except cosmetics.

 

[davkrat]

Thanks. I've seen some REALLY bad examples of that on semi autos. Like I said these aren't near max loads and velocities are low. Just wanted to make sure I wasn't pushing it. None of my other Remington 700's do anything like this but then again they are all older ADL and BDL's. This is from a newer SPS, maybe they have loser tolerances? Thanks for looking and offering a second opinion. The pressure concerns with monolithic bullets has me being extra careful.

 

[barnesuser28]

I shoot monolithics in almost all my guns, i dont treat them any different than lead bullets. I would be looking at ejector marks and flattened primers instead of crators.

 

[davkrat]

I shoot monolithics in almost all my guns, i dont treat them any different than lead bullets. I would be looking at ejector marks and flattened primers instead of crators.

Thanks. When the ETips first came out there was no published data, just the warning to not exceed mid loads for same weight cup and core. Hodgdon now has some ETip info on line and I am at least a grain shy of max for all of these. Wish the velocities were better with Varget. Will keep an eye out for ejector marks and flattened primers.

 

[Lefty7mmstw]

Thanks. I've seen some REALLY bad examples of that on semi autos. Like I said these aren't near max loads and velocities are low. Just wanted to make sure I wasn't pushing it. None of my other Remington 700's do anything like this but then again they are all older ADL and BDL's. This is from a newer SPS, maybe they have loser tolerances? Thanks for looking and offering a second opinion. The pressure concerns with monolithic bullets has me being extra careful.

you said it right in the middle of your statement-- remington-- any rem made in the last ten years or so is apt to have a loose firing pin hole/ firing pin matchup. I noticed the mottling on the back of the primer; is it a blued gun without a polished finish??

 

[davkrat]

you said it right in the middle of your statement-- remington-- any rem made in the last ten years or so is apt to have a loose firing pin hole/ firing pin matchup. I noticed the mottling on the back of the primer; is it a blued gun without a polished finish??

Yep. Rough bead blasted finish. I actually took very fine sandpaper and "polished" the underside of the bolt. Originally it would tear up the brass of the cartridge at top of the magazine.

 

[boomtube]

"Reading" primers is quite popular because it's easy for magazine authors to write about and sound authritive as well as easy for readers to understand. Problem is primers aren't much to read when we're trying to gage pressures because most cratering and flattening and pin hole blow-outs are due to things much different from excess pressure. I've seen a swollen rifle case head with bolt imprints but the primer itself looked normal. Reading pressure from primers is about as hopeless as a Chinese guy reading a Greek road map of Turkey.

 

[Wile E Coyote]

Every one of my factory Remingtons that is 15 years old or newer, that I haven't had work done to the bolt will crater the primer - with any load; factory or hand load. Remington's QC in this area ain't what it used to be.

 

[Reloader222]

From the photo's I do not see any "flat-hat-tops". I belief the pressure is fine. Try to keep with this brand of brass. If you change the brand of brass first compare them regarding weight and internal volume. I brass is heavier with lower internal volume, lower the load and take up slowly as you should know.