Flattened Primer Question

[Jtreb]

Can a loose primer pocket result in flattened and dimpled primers even if the load is not over pressured.
I recently cleaned and prepped all my .223 and .308 lapua brass including reaming all the pockets (cold winter day fun). Then loaded a bunch of rounds that had worked for me in the past. 25.3gr vht540 behind 69gr smk for the 223 and 44.5 gr varget behind 175gr SMS for the 308. I wouldn't expect either of these loads to be hot.

After shooting these rounds, both had the classic signs of overpressure in the primers.
I did not notice any other signs of over pressure but I am relatively new to this.
Both rifles are Rem700 5r.
So could my K&M pocket reamer have opened up the pockets a little too much allowing them to push back and flatten under normal pressure? or have I been running hot for a while and just not reading the signs

 

[stubblejumper]

I have never found it necessary to ream primer pockets in Lapua cases, but loose primer pockets generally don"t result in flattened primers. Were you previously using Lapua cases, or a different brand?

 

[yomomma]

Flattened primers "could be a sign" of over pressure. Sloppy headspace/loose primers could also flatten primers. IIRC people say measuring the base of the brass by the web is the best indicator of over pressure...also that piece of the bolt in your forhead

 

[r204]

What brand of primers are you using? Federal primers are softer and say cci and and ussually flatten slighly even very safe loads.

 

[bigedp51]

If your cases were full length resized and the shoulder was bumped back too far this would allow the primer to back out and flatten more than normal.

Below the amount of shoulder bump or shoulder setback during sizing is head clearance when the cartridge is chambered. When fired the primer backs out of the primer pocket and can be flattened more when fired.

I have also seen Remington bolt faces with a beveled firing pin hole that allowed the primer to flow into it giving a false sign of over pressure.

Below the .223 and .308 bolts have a beveled firing pin hole that the primer can flow into.

 

[camster]

http://www.hodgdonreloading.com/rel...-trick-monitoring-pressure-your-rifle-reloads

Primers can be an indicator of pressure, but they can also indicate something else going on too...alleviate pressure concerns with above link. Seems if the loads are tried, tested, and true something else may be awry.

I have a fav swede mauser that makes the ugliest of primers (o'er sized firing pin hole) well in the safe zone.

 

[lclund1946]

The K&M tools have an adjustable/replaceable carbide cutter that is adjusted by K&M to .122" for Small Rifle primer pockets and .131" for the large. If they are cutting too deep your primers could be seated too deep which would cause a situation similar to a Head Space Problem. Measure your primer pocket depth and the thickness of the primers. The CCI Primers I have measure about 0.004" under the preset depth of the cutter so would be seated about that depth unless you crush them when seating. The Remington 7 1/2 are a bit thicker than the preset depth so need a bit of a crush fit if your pockets are cut to .122".

http://kmshooting.com/kmshooting/media/pdf/32.pdf

 

[c-fbmi]

I can tell you for certain that oversize primer pockets do not cause primers to flatten............I'm in total agreement with Yomomma and bigedp51 and have experienced this several times when fireforming wildcats with even low to moderate pressure but excess headspace. Stop full length sizing your cases that have already been fired in your rifle, I suspect this is where you are going awry. Flattened primers are not really an issue, but when the head separations start you will have issues..........

 

[Jtreb]

Thank you for your input. I am using CCI primers in both. Neither of the bolts seem to have a bevel around the firing pin hole.
I think I have headspace gauges so I can recheck my die setup. Auberge my loads are just hot for these guns

 

[Jtreb]

Wow, some weird auto correcting there, and not sure why my photo is upside down but the don't look as bad in the picture.

 

[yomomma]

Although there is flow into the firing pin hole, these are not flattened. Firing pin hole might be oversized.


These are flattened

 

[Seeker2]

Hi Jtreb, I had the exact same question when I started loaded for my Remington rifles. I have a 700 CDL .260, 5R 300Win and a 783 in .223. All 3 of them will produce cratering where the firing pin hits the primer. Experience has shown that for my rifles it doesn't matter if it is a mild load starting load or one at max, the crater appears. The picture yomomma posted is a perfect example of a truly flattened primer. In addition to flat primers watch for sticky ejection of the empty and extractor marks as signs of high pressure.

 

[Jtreb]

Thanks for all your input. I dug out some old factory brass I had from before I started reloading and they had the same crater flow into the pin hole. I am now comfortable that my loads are not overpressure. I re-checked my headspace and my dies are dialed in with about .001 on both calibers. I just ordered neck sizing dies to extend brass life and increase safety and accuracy. Now back to the range to continue my quest for 5 - half moa groups with these factory-ish rifles.