Cratered Primer

[Curmudgeon]

All things considered is a cratered primer an indicator of a dangerous overload? If this is the only indication where should this load go? 6.5x47 moly Berger 140 target hybrid, 39.5 H 4350. CCI BR primer. Think I will try the CCI 41. I have been shooting 130 vld but wanted to try the new Bergers. No chrony yet and no quick load. .005 off the lands. Shot 1/2 min at 400. Will load 39 grains and run through chronograph.Thanks

 

[XBBR Shooter]

"[...] All things considered is a cratered primer an indicator of a dangerous overload? If this is the only indication where should this load go?"

No... safe loads can have cratering. But it IS a sign that you are getting close to a place where you need to pay attention.

Cratering can be caused by:
1 - Weak firing pin spring.
2 - Thin or weak cup (CCI 400, Federal 200, and Rem # 6-1/2)
3 - Over sized firing pin hole in the bolt
4 - High pressure.

If you have cratering, you need to find out why.

 

[K22]

No... safe loads can have cratering. But it IS a sign thata you are getting close to a place where you need to pay attention.
Cratering can be caused by:
1 - Weak firing pin spring.
2 - Thin or weak cup (CCI 400, Federal 200, and Rem # 6-1/2)
3 - over sized pin hole in the bolt
4 - High pressure.

If you have cratering, you need to find out why.

Yep - couldn't agree more - lot of reloaders are not aware of item 2 above - these have thinner cups than Federal 205M and Remington 7 1/2.

 

[Curmudgeon]

This bolt has been bushed by Greg. Also recently replaced firing pin and spring with Tannel fluted firing pin and spring. No heavy lift. No extractor mark. Have seen through experience some cups are soft. Tried Wolf and CCI and have used 41's with success before. Just shoot local matches so don't get to serious competitions. Will continue to work up 140's since we have confusing wind. Thanks.

 

[danny]

No... safe loads can have cratering. But it IS a sign that you are getting close to a place where you need to pay attention.

Cratering can be caused by:
1 - Weak firing pin spring.
2 - Thin or weak cup (CCI 400, Federal 200, and Rem # 6-1/2)
3 - Over sized firing pin hole in the bolt
4 - High pressure.

If you have cratering, you need to find out why.

I have also seen normal loads cratering when the firing pin hole has a chamfer at the bolt face.

Danny

Added info edit: This is what I have seen with a recent manufacture Remington 700. All loads have cratered primers in this rifle.

 

[NC308]

IMO. Primers are a poor source to watch for pressure signs. I have a Remington 700 action that craters everything you shoot in it. Even factory loads. So for the most part I don't look at primers for pressure.

 

[M-61]

I won't say I don't look for the craters but I consider them as XBBR said an indicator to be noted. I would be aware of a stiff bolt lift, then note the primer, and certainly pay attention to that piece of brass when seating a new primer. BUT it is the stiff bolt lift that would have alerted me. Without that lift the cratered primer does not tell me much. I get them in many rifles and I view them as maybe approaching a higher level of pressure but that's a big maybe. And what exactly does someone call a 'crater'? A slight ring around the indentation or a real ragged ridge? Like stated a "sign". I consider a stiff bolt lift as a real attention getter.

 

[Curmudgeon]

Thanks will take a picture of primer. No heavy lift. I have primers with other calibers that show crater but like you say craters happen.

 

[amlevin]

IMO. Primers are a poor source to watch for pressure signs. I have a Remington 700 action that craters everything you shoot in it. Even factory loads. So for the most part I don't look at primers for pressure.

Remington apparently uses the chamfer on their bolts to prevent "blanking". If the bolt is a stock Remington cratering is perfectly normal although extreme pressures will add a sharp edge at the perimeter of the "crater"

 

[Shynloco]

No... safe loads can have cratering. But it IS a sign that you are getting close to a place where you need to pay attention.

Cratering can be caused by:
1 - Weak firing pin spring.
2 - Thin or weak cup (CCI 400, Federal 200, and Rem # 6-1/2)
3 - Over sized firing pin hole in the bolt
4 - High pressure.

If you have cratering, you need to find out why.

I have to agree with all the above. But I'd also add one other thing to the list that is possibly a bi-product of pressure. And that is if 1-3 check out as good, the you probably need to look at the powder you are using and see if the same conditions arise when switching to another powder that creates the same velocity.

Alex

 

[XBBR Shooter]

I have to agree with all the above. But I'd also add one other thing to the list that is possibly a bi-product of pressure. And that is if 1-3 check out as good, the you probably need to look at the powder you are using and see if the same conditions arise when switching to another powder that creates the same velocity.

Alex

If you use another powder to get the same velocity, it will not do so at the same peak pressure - so that doesn't count.

 

[billlarson]

All things considered is a cratered primer an indicator of a dangerous overload? If this is the only indication where should this load go? 6.5x47 moly Berger 140 target hybrid, 39.5 H 4350. CCI BR primer. Think I will try the CCI 41. I have been shooting 130 vld but wanted to try the new Bergers. No chrony yet and no quick load. .005 off the lands. Shot 1/2 min at 400. Will load 39 grains and run through chronograph.Thanks

40x,sleeved f-pin.krieger barrel........... I shoot 39.0 grs. in mine o.k.... with 142 smk`s......... However...... if your brass fits too loose in chamber and your jumping bullets this can happen..... quickest way I no of to break a jewel trigger...
bill

 

[swampthang]

Here's what I can tell you from personal experience.
I shoot a 6.5 creedmoor in ibs 1000yd in.lite gun
I use federal 210m primers. I KNOW I don't have a hot load at all but my primers have always shown to crater.I had a fellow shooter swear I had a load to hot.
I can take the exact same load of h4350 behind a 140berger vld and use a cci br2 primer and it looks perfect.
Have always been told by other competitors that FED has been notorious to have a soft cup. Hope the helps.

 

[MagnumManiac]

I, too, have newly manufactured Rem 700 rifles, in 22-250/22-250AI and 300WM. Both rifles cratered primers from the get-go. Had them bushed and the problem went away.
If you have a rifle that DOESN'T normally crater primers, then it DOES, you are into excessive pressure because the pressure is overcoming the firing pin spring. I also often find the primer will be significantly flatter/rivetted if it has cratered.
Unless you use the use the same primers every time, primer appearance is not the best indicator of excessive pressure. Some FED 215's flatten with start loads, while WLRM primers with the same loads don't flatten even with max loads, with all else identical.

Cheers.

 

[Shynloco]

If you use another powder to get the same velocity, it will not do so at the same peak pressure - so that doesn't count.

Of course it counts! Read what I wrote...if 1-3 check out.... And if you change powders, you must start all over again in testing your load and work your way up. I NEVER suggested you are trying to duplicate the same powder load to obtain the pressure peak as each powder develops it's own pressure peak. If you see cratering and your velocity is below or above the previous powder you tested, that is another way of verifying or negating the powder you initially tested. I would not arbitrarily rule out looking at or considering another powder simply because it has a different pressure peak.

Alex

 

[XBBR Shooter]

Of course it counts! Read what I wrote...if 1-3 check out.... And if you change powders, you must start all over again in testing your load and work your way up. I NEVER suggested you are trying to duplicate the same powder load to obtain the pressure peak as each powder develops it's own pressure peak. If you see cratering and your velocity is below or above the previous powder you tested, that is another way of verifying or negating the powder you initially tested. I would not arbitrarily rule out looking at or considering another powder simply because it has a different pressure peak.

Alex

Does not. If you get 3,000 fps with a fast powder, and get 3,000 with the slow powder, the slow powder will get that velocity at a lower pressure, exerted for a longer time (a longer "Burn" curve). The fast powder will get that velocity with a higher pressure, for a shorter time.

 

[JLT]

Univariate models don't work in a multivariate environment. Primer condition should not be ignored, nor should it be the only variable in consideration.

 

[jlow]

All things considered is a cratered primer an indicator of a dangerous overload? If this is the only indication where should this load go? 6.5x47 moly Berger 140 target hybrid, 39.5 H 4350. CCI BR primer. Think I will try the CCI 41. I have been shooting 130 vld but wanted to try the new Bergers. No chrony yet and no quick load. .005 off the lands. Shot 1/2 min at 400. Will load 39 grains and run through chronograph.Thanks

One thing I am always a bit suspicious of is possible unintentional jamming when someone tells me they are 5 thousands off. In my experience, there are a lot of variables like uneven bullet length and inaccurate measurements (not saying the OP is specifically inaccurate, but it's hard to be that accurate) to name a few that can land you into the lands and then...

 

[danny]

One thing I am always a bit suspicious of is possible unintentional jamming when someone tells me they are 5 thousands off. In my experience, there are a lot of variables like uneven bullet length and inaccurate measurements (not saying the OP is specifically inaccurate, but it's hard to be that accurate) to name a few that can land you into the lands and then...

Being .005" off of the lands has always made me a bit nervous as well, especially since I primarilly shoot heavy loads out of gas operated guns. I have seen loaded rounds vary by .003 or so, and there is the spectre of possible inaccurate measurements that could concieveably cut your margin down to 0 or even into the lands for only some of the loads, leading to possible errant results, pressure spiking, etc. I prefer to be well off of the lands, beyond the error limits, or if I were more experienced in this area of reloading, well into the lands (but not in a self-loading firearm), also beyond the error limits, but on the other side.

Danny