Cratering - Is this something to worry about?

[jdbell2004]

I know primer cratering isn't the best indicator of overpressure but it still gets me worried. I've been handloading for years but this is my first 6.5 creedmoor and I'm noticing this cratering on several different powder charges. This is at 41.2gn H4340 under a 140 BTHP seated to 2.810. I'm seeing cratering to a degree all the way down to 40gn H4350. Am I worrying for no reason?

This load shoots 2724fps out of a 24" barrel.

 

[David Milisock]

I know primer cratering isn't the best indicator of overpressure but it still gets me worried. I've been handloading for years but this is my first 6.5 creedmoor and I'm noticing this cratering on several different powder charges. This is at 41.2gn H4340 under a 140 BTHP seated to 2.810. I'm seeing cratering to a degree all the way down to 40gn H4350. Am I worrying for no reason?

This load shoots 2724fps out of a 24" barrel.

Here's what I see, the primer has made an impression of the firing pin hole in the bolt and that has a ridge. However, the edges of the primer near the brass edge of the pocket are not flat, they seem to still be rounded, I'm betting the bolt face is interesting more than the load being really excessive.

Is the load a hot load by your reference material?

 

[rwj]

How far does the firing pin extend from the bolt face?

 

[Ironman308]

Is this a Remington action. If so all mine do this with standard loads.

 

[Leeman]

Looks OK to me, just excessive clearance around the firing pin in the boltface

 

[jdbell2004]

Here's what I see, the primer has made an impression of the firing pin hole in the bolt and that has a ridge. However, the edges of the primer near the brass edge of the pocket are not flat, they seem to still be rounded, I'm betting the bolt face is interesting more than the load being really excessive.

Is the load a hot load by your reference material?

I'll get a photo of the bolt face today.

I'm approaching or over depending on the reference material.

Hornady shows a max load of 42gn.
Hodgdon shows a max load of 40gn.
Quickload shows a max load of 41.8gn.

 

[jdbell2004]

How far does the firing pin extend from the bolt face?

How would I measure this?

 

[jdbell2004]

Is this a Remington action. If so all mine do this with standard loads.

I should have mentioned this is in my Ruger Precision.

 

[rwj]

How would I measure this?

Remove the bolt from the action, release the cocking piece, then use a depth gauge/caliper to measure how far the pin extends from the bolt face.

 

[edwardware]

Given the nice radius around the primer edge, I'd say the (tiny) cratering has more to do with an excessively large pin hole than excessive pressure. This is unsurprising in a factory action.

 

[spudgun]

/\ /\ /\ /\ /\ /\, What he said.

My Savage model 12 was doing this to my 6.5 CM also in some cases it would pierce the primer.

I was using CCI 400 primers. Did some research and read that in some Savage's the firing pin hole is slightly too big and would allow the firing pin to wiggle when the round went off causing cratering/piercing in the primer.

I started .using CCI #41 and all problems went away. You can also have your bolt head bushed to get rid of the slop.

 

[Pawnee Bill]

Have you bolt bushed. Problem solved.

 

[jdbell2004]

Here's what I see, the primer has made an impression of the firing pin hole in the bolt and that has a ridge. However, the edges of the primer near the brass edge of the pocket are not flat, they seem to still be rounded, I'm betting the bolt face is interesting more than the load being really excessive.

Is the load a hot load by your reference material?

Firing pin hole measures about .080".

 

[Bill K]

Even tho those companies show

I'll get a photo of the bolt face today.

I'm approaching or over depending on the reference material.

Hornady shows a max load of 42gn.
Hodgdon shows a max load of 40gn.
Quickload shows a max load of 41.8gn.

a max load. You rifle and pressure signs will tell you, what YOUR rifle will handle.

 

[243winxb]

Load & primer look ok to me. Watch for hard bolt lift. Pressure signs.

 

[SKWERLZ]

Lots of factory rifles like 700’s and savages crater most everything

 

[spudgun]

I'll get a photo of the bolt face today.

I'm approaching or over depending on the reference material.

Hornady shows a max load of 42gn.
Hodgdon shows a max load of 40gn.
Quickload shows a max load of 41.8gn.

My most accurate load is; 40.5 Gr H4350, 140 Gr Hornady bthp Match, 2650 avg FPS, .03 off the lands.

Now i also know a fellow shooter that pushes his 140, with 41.5 Gr H4350.

Good luck

 

[David Milisock]

I'll get a photo of the bolt face today.

I'm approaching or over depending on the reference material.

Hornady shows a max load of 42gn.
Hodgdon shows a max load of 40gn.
Quickload shows a max load of 41.8gn.

If your bolt opening after firing is not sticky, (I like the lift it with my pinky method) I'd feel ok with the load, "if it was developed in warm to hot temperatures "!

I'd like to see a real close up of that firing pin hole with a pin light ti brighten up the hole. 8 'm betting we see the cause of that ridge on your primer.

 

[CA_Shooter]

I should have mentioned this is in my Ruger Precision.

I had the same issue with my RPR. @carlsbad needed to bush my bolt. After he did it, I also had more consistent groups at distance.

Here is a long thread trying to figure out the issue. TL;DR: it was the bolt needing to be bushed

Too little neck tension? Virgin Lapua Brass? Cratered Primers

Post #44 has an update For 6.5 creedmoor I switched brass from Hornady to Lapua. Also switched to CCI 450s With the Hornady brass, I mandrel using a .264. This gets me to PSI readings on the 21st century arbor press of about 70-90 Using Virgin Lapua brass, I mandreled it the same. But my...

forum.accurateshooter.com

 

[jdbell2004]

I reached out to @carlsbad via PM about bushing but the more closely I look at things, the tip of the firing pin is troubling me. It does not feel smooth at all. It is rounded but seems "unfinished". I have reached out to Ruger, they want the entire firearm mailed in.

Anyway, I pierced two primers yesterday. I was shooting groups, the same load for all groups. I got through 17 rounds with only minor cratering then loaded up my last 5 rounds for the day. Pulled the trigger and smoke started rolling out of the receiver. I pulled the bolt and immediately saw the hole in the primer. Pulled the magazine, pulled the bolt apart, removed all debris, scratched my head, and loaded it up again. Next trigger pull, same thing so I packed up and went home.

Why would I start piercing primers all of the sudden with no change in load?

I've attached a couple of shots of the firing pin fit and protrusion. Measured at .048".

Also, my punctured primers

On a positive note, this rifle can shoot! Only one group greater than 1moa, most around .5-.7moa with 200 rounds through it!