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6.5 Creedmoor Primers Burning Through

treillw

Hello,

I'm wondering what the thickest primer is to use for a 6.5 Creedmoor with Lapua Brass using small rifle primers?

I'm shooting 147 eldms with varget. I did some pressure testing and got a max powder charge of 38.5 grains.

39 grains gave me 2729 fps
40 grains gave me 2817 fps

During testing, I saw no pressure signs on the primers, only had a mild extractor mark, and no hard bolt lift. So I backed off to 38.5 as a safe max, based strictly on velocity.

I shot a bunch of rounds with 38 grains of powder, giving me a little over a quarter minute at 400 yards. Tickled. I used up all those primers and went and bought 1500 more of the same kind- CCI #450. I loaded up some more bullets.

Before hunting season I had the gun out for a bit of practice with my golden 38 grain load. As I was shooting through the 10 or 15 that I had loaded up, I noticed that a couple of the primers were burning through. Well I guess I must be over pressure I thought and headed home.

So I loaded up some with 37 grains of varget and took them out to the range a couple of days ago. The are burning through as well. What the heck?

The only thing I can think of is that the new batch of primers aren't as strong as the old ones I had, even though they are both CCI 450. Anybody else run into this?

Are there any primers out there that are thicker than the CCI 450?

I also need to break out the chronograph again and check my velocities.

Thanks!
 
450’s are pretty tough primers! Somehow I doubt they’re where your problem is.

I’d take a real careful, close look at the working end of your firing pin. See if you can see any pitting or burr, something that’s causing your primers to pierce.

If you can post a pic or two here, show us what you’re seeing, we might be able to help you suss out a cure.
 
spclark said:
450’s are pretty tough primers! Somehow I doubt they’re where your problem is.

I’d take a real careful, close look at the working end of your firing pin. See if you can see any pitting or burr, something that’s causing your primers to pierce.

If you can post a pic or two here, show us what you’re seeing, we might be able to help you suss out a cure.
Click to expand...

Will do. Do you think the loads I have are way too hot? I know they are up there, but all signs were good previously.......

26" Kreiger barrel
 
When you say 'burning through', do you mean like the one in the centre of the pic below? If so, that's not pressure burning through, it's what's called 'blanking' and usually results from an over-large firing pin tip allied to a poor fit in the bolt-face allied to a Small Rifle type primer (srp).

So, the second question is what action are you using? Some factory actions blank every srp primer going when you get much above starting load pressures. The one that produced this blanked primer is an FN SPR (Winchester Model 70 action) that had been rebarreled to 6.5X47 Lapua and did just this. It was promptly rechambered to 260 Rem whose Large Rifle (lrp) size primers solved the problem.

So why srp problems and not in lrp? I can't tell you why, but that's the way things pan out. There are three possible answers to your problem if it has bolt/firing pin causation: 1) use a harder primer with a thicker cup - but that's not much help here as the CCI-450 SRM primer has the heavier 0.025" cup and is about as tough a small primer as you'll get; 2) send your bolt off to Gre-Tan Engineering or one of the other gunsmiths who turn the pin down and fit a bushing with smaller diameter hole intro the bolt-face; 3) in your case as you're3 loading 6.5mm Creedmoor you have the choice of brass with both primer sizes. So put the Lapua srp stuff to one side and get Hornady, Starline, Norma, Peterson or whoever lrp cases.

07.jpg
 
Is it dangerous to shoot the gun with loads that are doing this? Any danger of the gas blowing into your eyes?

The rifle is a ruger precision. A new firing pin wouldn't help things? Think ruger will do anything about it?
 
It isn't dangerous but your problem will get worse. Especially since your firing pin is off center (like yours). The crater pokes into the firing pin hole and prevents the bolt from rotating freely. It will open up the firing pin hole even more.

If you're on a tight schedule I can give you 2 day turnaround.

--Jerry
 
Every gun is a bit different, but IMO your loads are probably pretty hot, and so is Varget for the 147 class of 6.5 bullets. Hodgdon's site isn't showing a Varget load for the 147's. Their data does however show a 142gr MK load with Varget with a max of 36.3 using Hornady brass....and your Lapua brass also has less capacity than the Hornady brass.
 
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You certainly don't want to continue as is for the reasons others give in earlier posts. The direct risks to you are usually very small as the volume of escaping gas is limited, initially directed into the bolt body past the firing pin, and while I can't speak for the RPR design, any decent action design from the Model 1898 Mauser onwards sees gas directed sideways or downwards out of the action through gas escape holes in the bolt body. All you see / feel when this happens in most rifles is small wisp of smoke coming from places where there shouldn't be any, and in some designs a small kick on the trigger.

The escaping gas erodes the pin tip and its hole in the bolt as others point out. It's unlikely to damage the trigger mechanism, but any escape through there is most undesirable as it will at the least deposit fragments and carbon fouling into a component that needs to be as clean as possible.

The other important side-effect that often applies is that the missing bit of primer cup, hasn't vapourised somehow, it still exists somewhere as a small brass disk. More often than not, the 'somewhere' is inside the front end of the bolt body having been blown past the pin tip. Get a few of them inside the bolt, sometimes it only needs one, and sooner or later you'll suffer ignition problems caused by this contamination affecting firing pin fall. This can be complete misfires or weak strikes that produce erratic cartridge performance, worse the potentially dangerous hangfire condition.
 
I've received bolts to bush that were covered with soot inside and it may have been the soot that caused poor function that caused the owner to decide to fix it. I've received a few that needed a new firing pin. Remington firing pins are not expensive.

So long as the leakage is from firing pins the damage is easily repaired by bushing. When you get deep pitting from primer leakage, then the damage is outside a normal bushing and I need to put in a larger bushing that gets into the ejector hole. I have to charge extra for this extra work.

--Jerry
 
treillw said:
Hello,

I'm wondering what the thickest primer is to use for a 6.5 Creedmoor with Lapua Brass using small rifle primers?

I'm shooting 147 eldms with varget. I did some pressure testing and got a max powder charge of 38.5 grains.

39 grains gave me 2729 fps
40 grains gave me 2817 fps

During testing, I saw no pressure signs on the primers, only had a mild extractor mark, and no hard bolt lift. So I backed off to 38.5 as a safe max, based strictly on velocity.

I shot a bunch of rounds with 38 grains of powder, giving me a little over a quarter minute at 400 yards. Tickled. I used up all those primers and went and bought 1500 more of the same kind- CCI #450. I loaded up some more bullets.

Before hunting season I had the gun out for a bit of practice with my golden 38 grain load. As I was shooting through the 10 or 15 that I had loaded up, I noticed that a couple of the primers were burning through. Well I guess I must be over pressure I thought and headed home.

So I loaded up some with 37 grains of varget and took them out to the range a couple of days ago. The are burning through as well. What the heck?

The only thing I can think of is that the new batch of primers aren't as strong as the old ones I had, even though they are both CCI 450. Anybody else run into this?

Are there any primers out there that are thicker than the CCI 450?

I also need to break out the chronograph again and check my velocities.

Thanks!
Click to expand...

A lot of good advice above. There are other things that would also be good to check.

Did you also change lots of Varget. If you did, you may have a faster lot.

Check for a carbon ring at the throat of your chamber. If you don't have a bore scope, you can drop a bullet into the chamber and force it into the lands with a wooden dowel. Bump it back out with a cleaning rod. If you have a ring of scratches around the bullet, you are building up a carbon ring there. That will cause high pressures and blown primers.
 
carlsbad said:
I've received bolts to bush that were covered with soot inside and it may have been the soot that caused poor function that caused the owner to decide to fix it. I've received a few that needed a new firing pin. Remington firing pins are not expensive.

So long as the leakage is from firing pins the damage is easily repaired by bushing. When you get deep pitting from primer leakage, then the damage is outside a normal bushing and I need to put in a larger bushing that gets into the ejector hole. I have to charge extra for this extra work.

--Jerry
Click to expand...
Jerry, I may have missed this. Do you change the firing pin to the smaller size when you bush the factory 700 bolt for the 6.5 Creedmoor SRP brass? Thanks!
 
"Bushing the firing pin" is a process to make the firing pin hole smaller. It isn't the clearance between the firing pin and the hole in the boltface that is the problem, it is the diameter of the hole. The force causing the primers to extrude is the pressure inside the case times the area of the circular hole. If you reduce the hole diameter, the force decreases by the square of the diameter. Experience has shown that the .080-.085" diameter holes in common OEM bolts crater badly, .070 used in a lot of customs is usually acceptable, and .060-.062 used in bushing almost always totally eliminates the problem.

To bush a bolt the center of the bolt is drilled out and an insert permanently installed. It is precision bored to a new, smaller diameter, usually around .062". Then the firing pin is turned or ground to a new diameter that allows for .001 to .002" clearance.

--Jerry
 
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