Cause of random cratered primers???

[Subwrx300]

I've recently started getting random cratered primers. It's about 50/50 normal vs cratered. Here is background info:

• Howa 1500 action with 4500 rounds.
• Original firing pin, spring and shroud
• 26" Criterion barrel with Bighorn nut headspace set tight (just close on go gauge)
• Barrel has 750 rounds through it and I'd still clean and nearly new looking.
• Hornady and Starline brass, batches between 2 and 7+ firings.
• Brass bumped .0015-.002
• two known loads developed specifically for each type of brass: 41gr for Starline, and 42 grain for Hornady (Starline has lower H20 capacity and needed to reduce charge to stay at same velocity as Hornady)
• Primer pockets are tight and very consistent feeling on seating
• BR4 primers, H4350 and 140ELDMs
• Primers are NOT flattening; simply showing flow into firing pin hole on breach.
• No issues with cratering or any other pressure signs for first 500+ rounds with same loads and powder lots.
• Even now, zero other pressure signs (no ejector marks, no shiny spots, no sticky extraction, etc).
• Doesn't matter whether barrel is scrubbed clean off all carbon/copper or super fouled. Still have crater on 50%.
• Velocity has not changed at all after noticing cratering.
• 2760-2770 for both loads, SDs are still in the 7-10 range which is where they have been since barrel was new.
• Groups are showing more vertical spread than I've seen in the past.

I'm not super concerned that there are any major pressure increases because it seems like I would also be seeing a major velocity increase (20-30fps or more). But I am curious if anyone else has had this happen and if you found a way to fix it.

Could it be that primer pockets are letting primer slip rearward on some and not others?

I noticed this when temps dropped into 10-20 deg range; could be coincidence but also could be that primer cups are shrinking slightly and letting them slip during firing.

Haven't run into this before so I'm curious and hopefully can find a fix.

 

[AIAW]

Looks like a good description of what you know about the rifle and loads. I didn't see anything about primer pocket depths though.

Perhaps try uniforming your primer pockets to ensure that all primers are seating at exactly the same depth. For your test lot of brass, if the uniformer won't cut a piece of brass then don't use it (too deep). Load and fire that lot like you normally would.

This test would at least rule primer depth as a variable.

Does it do this only with "fired" brass or new brass also?

 

[Subwrx300]

Looks like a good description of what you know about the rifle and loads. I didn't see anything about primer pocket depths though.

Perhaps try uniforming your primer pockets to ensure that all primers are seating at exactly the same depth. For your test lot of brass, if the uniformer won't cut a piece of brass then don't use it (too deep). Load and fire that lot like you normally would.

This test would at least rule primer depth as a variable.

Does it do this only with "fired" brass or new brass also?

I haven't fired new brass in a long time. I've got 1200+ pieces split into 5 lots. Ran a match today and had similar results. Shot well but still want to isolate the cause to see if it's something I've created or just brass issue.

I'll measure some pocket depths to see if they are different between the cratered and non cratered pieces.

 

[AIAW]

Cool, sounds good. Outside of doing that, as long as the brass is all uniformly clean (lube, etc.) on some versus others (affecting bolt-thrust) then you might just find your issue there with the pocket depths perhaps.

 

[Subwrx300]

Cool, sounds good. Outside of doing that, as long as the brass is all uniformly clean (lube, etc.) on some versus others (affecting bolt-thrust) then you might just find your issue there with the pocket depths perhaps.

You just reminded me that I've started using spare amounts of Imperial for wax. I dab my finger top of rubber gloves on can every 5 rounds or so. I wonder if it's that the first two have more residual lube and perhaps have more thrust!

I'm going to check that this week. Glad you mentioned lube. I clean lube off brass but it's possible that since using imperial, a bit more is staying on case.

Will check pocket depth and test going back to house l Hornady one shot only; i have never had issues with cratering when using only Hornady spray lube.

 

[AIAW]

I think we may have just found the culprit perhaps! Still measure those pockets just for curiosity sake.

Clean that chamber real good too of course

 

[Bandit320]

I had a similar problems with my 243 when I switched sizing lube to a spray lube. When is switched back the problem went away. I’d change back to you’re original procedure.

Mike

 

[Subwrx300]

10+ years of precision reloading and it's still the small stuff that shoots between the cracks! Thanks for the input and will post back if problem fixed by either of those ideas.

 

[DIBBS]

I didn't see it mentioned, any changes to Lot of powder or a new batch of primers? Lube left on the case would certainly increase bolt thrust, and I would imagine could increase extrusion around the firing pin. Let us know what you find out.

 

[Subwrx300]

I didn't see it mentioned, any changes to Lot of powder or a new batch of primers? Lube left on the case would certainly increase bolt thrust, and I would imagine could increase extrusion around the firing pin. Let us know what you find out.

Same powder lot and bullets. I recheck loads for speed with all new lots of powder, and in this case, it ran about 250 rounds with current lots without any cratering issues.

I'm going to test the lube theory by cleaning some left over rounds from my match with alcohol and compare them to the ones I shot in match today.

There is only one other possibility: I'm going to soak and clean my chamber mop to be sure it's not putting oil into chamber from recent cleanings. But will have to do that last so that I don't mix too many variables.

 

[Subwrx300]

Her is a photo showing what Im seeing:. Shot today, all loaded with RCBS 1500, SD 7-9, and random primer flow.

Pieces on left no flow; on right crater that catches fingernail. Counted 24 out of 50 had flow + firing pin dent flattening back outwards. The others look normal. They are in box in order shot and it is completely random: some on first shot others midstring and some strings had only 2-3 of 10 rounds per stage.

Just a visual. Will clean left over rounds and see if that eliminates.

 

[BLKWLFK9]

I've got the same thing going on with my BR.

 

[Deleted member 10043]

Normal

 

[nso123]

Have you considered giving the brass a quick tumble after sizing to remove any Imperial that might still be on the case?

 

[bax]

If you pierce a primer, there is a small curved disk of primer metal that is cut out of the primer cup. That little disk may find its way into the firing pin channel inside the bolt. The firing pin has a more-or-less square shoulder. If there is a little metal disk between the firing pin shoulder and the bolt channel sometimes it prevents the firing pin from dropping all the way, other times, not. The firing pin always goes far enough to fire the primer but sometimes the primer metal can flow back around the pin and sometimes not.

Remove the firing pin assembly from the bolt, clean the channel, and visually inspect it. That little disk is really small. Inspect the firing pin spring to be certain that there is no fragment of metal hiding in it that could drift toward the chamber and interfere with reliable firing pin operation.

This has happened to me so I know that it can happen. I have found the little disks in the bolt channel. I know that when I got them out, the firing pin operation was more reliable. This would explain what you see but that is no guarantee that this is the problem. Still, something to check.

 

[BLKWLFK9]

I'm getting minor cratering on a load that I know is not over pressured. I dont have a plunger ejector so I can't see swipes but I also dont have heavy bolt lift. does it with cc450's and fed 205m primers. super slow velocity too so theres no way I'm getting over pressured.

 

[Subwrx300]

I'm getting minor cratering on a load that I know is not over pressured. I dont have a plunger ejector so I can't see swipes but I also dont have heavy bolt lift. does it with cc450's and fed 205m primers. super slow velocity too so theres no way I'm getting over pressured.

This is what's making me think it has to do with lube left on cases (small amounts) or in chamber from prior shots with some lube/oil. It's possible headspace could cause this but I should see other issues like brass growth that I'm not seeing.

What lube process do you use for sizing? And do you completely remove it after loading?

I do a light wipe down but I'm sure I still have some lube on case(s).

 

[BLKWLFK9]

There is probably a little lube left on the cases but will tumble a 2nd time from now on.

 

[clcustom1911]

It's possible headspace could cause this but I should see other issues like brass growth that I'm not seeing.

If you haven't checked headspace, please do. The primer might be backing out a few thousandths at the beginning of powder ignition.

I was having the exact issue you were having and I re-checked my headspace. I had made an error when I installed my barrel on my RPR initially and accidentally set the headspace about 3-4 thousandths too long.

I re-set it correctly and the issue vanished.

 

[Subwrx300]

If you haven't checked headspace, please do. The primer might be backing out a few thousandths at the beginning of powder ignition.

I was having the exact issue you were having and I re-checked my headspace. I had made an error when I installed my barrel on my RPR initially and accidentally set the headspace about 3-4 thousandths too long.

I re-set it correctly and the issue vanished.

I was referring to the other guys rifle; I check headspace frequently. Go gauge and go gauge with Scotch tape (no go).

Plus, I've been running the barrel for 800+rounds without tinkering with headspace since I assembled rifle. This has only started happening in the last 200-250 rounds or so.

 

[clcustom1911]

I was referring to the other guys rifle; I check headspace frequently. Go gauge and go gauge with Scotch tape (no go).

Plus, I've been running the barrel for 800+rounds without tinkering with headspace since I assembled rifle. This has only started happening in the last 200-250 rounds or so

Roger. I must have missed that.

 

[Subwrx300]

Roger. I must have missed that.

No worries; didn't want that to sound snappy.

 

[BLKWLFK9]

Have u seen an increase in velocity or gotten a heavy bolt lift? you may have answered that already and I missed it.

 

[Subwrx300]

Have u seen an increase in velocity or gotten a heavy bolt lift? you may have answered that already and I missed it.

It's in the first post details, but no heavy bolt, and no velocity increase. I'm religious about chronograping every chance I can (Labradar) to confirm speed in various conditions.

Avg 2750-2770 depending on temp: 2755 in 0-10def weather and 2772 in hot weather. Right now it's close to 2755 avg.

 

[Darkhorse1]

I'm getting minor cratering on a load that I know is not over pressured. I dont have a plunger ejector so I can't see swipes but I also dont have heavy bolt lift. does it with cc450's and fed 205m primers. super slow velocity too so theres no way I'm getting over pressured.

I'm getting this out of an arc nucleus as well with cci 450. Low velocity is cratering at 2600 fps 40gn H4350. No other signs of pressure however. Factory 140 eld m has no cratering. Headspace is good to go as well. I do use imperial wax, maybe I'll wipe down the remaining cases with alcohol just in case there is some residual wax.

 

[Anderson_A]

I get cratering when I shouldn’t with my nucleus as well randomly same speeds 140eld going 2750-2760 in a hornady case cci200 primer I actually stopped using 250s because it was consistently cratering

 

[Subwrx300]

Seems like a common cause could be imperial or CCI. I never did get it figured out but it's still shooting well and craters are very small

 

[Anderson_A]

Just out of curiosity I know your using a different action but I have a defiance action that does not do it and a nucleus that does with the same box of primers but I will take a measurement of my firing pin and the firing pin hole on both bolts maybe there is some correlation between the sizes of those two and the cratering

 

[Subwrx300]

Just out of curiosity I know your using a different action but I have a defiance action that does not do it and a nucleus that does with the same box of primers but I will take a measurement of my firing pin and the firing pin hole on both bolts maybe there is some correlation between the sizes of those two and the cratering

That's a good idea. I've got a Howa that has the large pin/hole and an impact precision with the small hole. The impact has not shown any cratering with the same load. Headspace is tighter by .001 but brass is bumped accordingly.

 

[BLKWLFK9]

I think it's the size of the firing pin hole in the bolt face. Its bigger in diameter and allows the primer to flow around the pin and take shape of the hole. It's obviously not from over pressure

 

[AIAW]

From your pictures too it doesn't look bad. No ejector marking, no heavy bolt lift. I'd just run it and enjoy!

 

[Anderson_A]

Going to be hard to see but basically same story the bottom three rows are 0.1gn increments of h4350 in hornady brass 140eld cci200 starting at 41.0gn up to 43.4 to see where I hit pressure and what speeds I was getting you can probably see charge #2 from top left or 41.1 gn produced the same crater as my max charge of 43.4gn also 43.3gn which was where the bolt lift got a little heavy has none I can see or feel, it seems random

 

[Anderson_A]

So just some numbers I took off my bolts to see where they stand

Nucleus bolt face and pin
Firing pin protrusion - 0.035”
Firing pin diameter - 0.0615”
Firing pin hole diameter - 0.062”
Still using a 16lb firing pin spring which may be a possible cause in my case not sure


Deviant bolt face and pin
Firing pin protrusion - 0.060”
Firing pin diameter - 0.0605”
Firing pin hole diameter - 0.061”
Not positive on the firing pin spring weight but I know I read it was higher than the 16lbs of the nucleus I would have to look it up but I believe 21lbs is what I remeber not even sure if it’s relevant

Only other thing that jumps out is the almost double pin protrusion beyond the face but again I’m not sure how/if that is relevant to this conversation

 

[PinesAndProjectiles]

So just some numbers I took off my bolts to see where they stand

Nucleus bolt face and pin
Firing pin protrusion - 0.035”
Firing pin diameter - 0.0615”
Firing pin hole diameter - 0.062”
Still using a 16lb firing pin spring which may be a possible cause in my case not sure


Deviant bolt face and pin
Firing pin protrusion - 0.060”
Firing pin diameter - 0.0605”
Firing pin hole diameter - 0.061”
Not positive on the firing pin spring weight but I know I read it was higher than the 16lbs of the nucleus I would have to look it up but I believe 21lbs is what I remeber not even sure if it’s relevant

Only other thing that jumps out is the almost double pin protrusion beyond the face but again I’m not sure how/if that is relevant to this conversation

I am not a gunsmith, but I would say that a .060" firing pin protrusion is rather excessive. Do you pierce any primers?

I am only basing this off of what Ted said in one of his write ups on the Nuke.

 

[Anderson_A]

Yea I did a double take when I saw the measurements but I too am I only going by what Ted has said in regards to the nucleus I do know this that deviant runs like a Swiss watch never had a single issue of any kind with anything I’ve fed it but I did just start reloading this winter so it has been on a factory ammo diet most of it’s life with me it is also a higher round count action I bought it used so the pin may have some wear I did notice a half thou of difference in pin diameter when measuring around it

 

[Darkhorse1]

Moving this to the appropriate thread...

I'm getting cratering with Lapua srp; cci 450; h4350 (all charge weights); TT Diamond. I'm going to try new brass and a new box of primers to compare. I've read some things about the fp hole being slightly larger on remy 700 bolts which can cause this, so maybe that is all it is. There doesn't seem to be any signs of excessive pressure, I've measured case heads against factory Hornady and they are the same. The factory loads aren't cratering however.

View media item 901

 

[Anderson_A]

Moving this to the appropriate thread...

I'm getting cratering with Lapua srp; cci 450; h4350 (all charge weights); TT Diamond. I'm going to try new brass and a new box of primers to compare. I've read some things about the fp hole being slightly larger on remy 700 bolts which can cause this, so maybe that is all it is. There doesn't seem to be any signs of excessive pressure, I've measured case heads against factory Hornady and they are the same. The factory loads aren't cratering however.

View media item 901

Got the Lapua brass and cci450s rolled up and tried them out had my first failure on my handloads only 1 out of 200 rounds but that’s another story wondering if your seeing anything different I loaded 40 rds with cci 450s and another 40 or so with fed 205m and it cratered everything starting loads right up to pressure limit if anything it seems more pronounced with small rifle primers

 

[Darkhorse1]

Got the Lapua brass and cci450s rolled up and tried them out had my first failure on my handloads only 1 out of 200 rounds but that’s another story wondering if your seeing anything different I loaded 40 rds with cci 450s and another 40 or so with fed 205m and it cratered everything starting loads right up to pressure limit if anything it seems more pronounced with small rifle primers

No changes on my end, tried new Lapua sp, once fired Lapua sp, once fired Starline sp, factory Hornady (only ones that didn’t crater and have lp), once fired Lapua with cci 41 (everything else was cci 450). Everything still has the cratering regardless of load. Went from 40-43.4 gn of H4350. Case heads all measure the same as the factory brass so not going to hot. Mine will prob ftf next month at my local club match lol. I haven’t had any malfunctions to date, I did strip the bolt and run it through the ultrasonic cleaner however, and put grease on the areas in the diagram arc posted.

 

[Anderson_A]

I put the 19# spring in to see if it has any effect on cratering not because of the failure but I wouldn’t think you will have the ftf issue it seems your action either works or it dosent I’ve put hundreds of large primer rounds through this action without issue and I have less firing pin travel than a lot of guys who are having issues and all that with the 16# spring one round out of 600 could be me not seating the primer properly or any number of things on my end