Primer cratering in a Panda

82boy

82boy

Patrick Kennedy
I put together a panda over the winter, and I having an interesting problem. The action is new and been sitting in a box since 1994. I find that my primers have craters or flow back when fire with an average load. (6PPC with 68 gr bullet and 29.2gr of n133.) I believe I am a bit short on firing pin travel, and that is causing my problem. I have measure the pin travel at .227 from cocked to fired. I am measuring my firing pin protrusion at .063 so If I subtract the pin protrusion from the travel I get .164 of actual travel. What should minimum travel be? How do I determin which trigger hanger I need? Thanks
 
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You probably have the .075" fireing pin hole. Take the fireing pin out and measure the tip, my guess is that your action have the bigger hole. Nowadays, you can specify if you want .062", .068", or .075". Back then, they probably only had .075".

Anyways, as long as they don´t break, it´s a no issue.

//Peter
 
One thing, re-measure your travel. I have never seen a Panda with less than .220 or so. They are known for having the correct, (as in a lot) of travel.

The culprit is probably the firing pin hole diameter. keep in mind, that 'moderate load' that you are referring too is still over 50,000 psi. ........jackie
 
The firing pin, is correct for the bolt head, the pin fits tight in the hole.

I did call Kelbys and the Agreed that the firing pin travel is more than likly the culprip, There only answer they gave me was ship the entire rifle to them. Not something I want to do, if i dont have to. Espicaly if the answer is a quick fix, like changing a hanger, as they acted that was all they was going to do.

I have measured the firing pin travevel well over a dozen times, and I keep getting the same numbers.
 
82boy said:
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I did call Kelbly's and the Agreed that the firing pin travel is more than likely the culprit, There only answer they gave me was ship the entire rifle to them. Not something I want to do, if i don't have to. Espicaly if the answer is a quick fix, like changing a hanger, as they acted that was all they was going to do.

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Kelbly's offer trigger hangars that have different offsets to change the trigger fall amount. I think they are about $20 or so. If you only have 0.220 fall, I'd suggest getting a +0.030 or 0.040 offset hangar. PM me for more info if you wish.

If I remember correctly they recommend 0.245-0.255 TOTAL travel.

If you do send the action to Kelblys I suggest you also have them change the firing pin spring. An action that old the spring is setting shorter. I have mine changed every 4 years while I am at the Super Shoot.
 
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82 I had one like that. It did the same thing. I could never get more than about 28gr of 133 without cratering or even having the primer pierce.
It was as Jackie said the hole diameter.
In my case they were saying the firing pin and hole together were too large and that I should have the hole bushed smaller with a smaller firing pin.
I could be mistaken but I think this is what Jackie is referring to not that the hole bigger than the firing pin but I could be wrong.
 
My buddy has an older Panda from early 90's that does this too. His firing pin is the .075" and it fits snugly to the pin hole. I think the only way to stop it is to bush the hole and order a smaller pin from Kelbly's. Or use a primer with a harder cup than the 205.
 
Insufficient FP travel

82boy said:
..... as they acted that was all they was going to do.

[snip]
Click to expand...

That is not what I said. I said that a common problem is insufficient fall; and a new trigger hanger with the appropriate hole spacing to match your trigger may or may not fix the problem. I also said that the firing pin spring may be weak and would need to be replaced if so.

Common causes are:

1. Hot loads
2. Short fall (<0.250"). Typically under 0.220" is when createring occurs.
3. Weak firing pin spring (<22 lbs.)
4. Deformed firing pin tip
5. Excessive FL resizing - shoulder setback (>0.001")
6. Eroded firing pin hole in the face of the bolt

On many occasions I've shot 30.0g of N-133 in a 6mm PPC with 66g FB bullets in a 0.2370"/0.2430" cut rifled barrel and a similiar sized button rifled barrel using a 0.074" firing pin tip and Fed 205M primers with no createring problems.

We sent you a trigger hanger today free of charge that will give you the appropriate amount of fall for your trigger. The only other option if you are unable to solve the problem is to have us check the bolt and firing pin assembly. This is what we would have to examine...not the whole rifle (provided your firing pin travel and resizing measurements are as stated).

Best regards,
Greg Walley
Kelbly's Inc.
 
Greg Walley said:
That is not what I said. QUOTE]

Let me set things straight.

Greg, if you look at the date on this post you will see that it was posted before we talked today, when I talked to someone last week. I cant remember the guys name but he is the one I was refering to as per conversation. As I told you before we got into our conversation, as I explained what he had told me. This is the reason why I wanted a second opinion, and called you today. I could not update this post because I had to go to work shortly after I talked to you.

So with that said, yes I did call Kelbys a second time, and talked to Greg. I desided to talk to Greg, becuse I did not like the first answer I got, and I was not getting any soild answers to this post. I also talked to Greg because I have shot with him before, and I should have talked to him the fisrt time. Yes Greg was more insiteful that the first person I talked to, and he did help me out.

Thank you Greg.
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Greg Walley said:
Common causes are:

1. Hot loads
2. Short fall (<0.250"). Typically under 0.220" is when createring occurs.
3. Weak firing pin spring (<22 lbs.)
4. Deformed firing pin tip
5. Excessive FL resizing - shoulder setback (>0.001")
6. Eroded firing pin hole in the face of the bolt
Click to expand...

I wonder what may be wrong with my buddy's action then? He doesn't shoot hot loads all the time (usually around 28.9 N133 works well in his barrel), his fall is .230", he's got two new springs, his tip appears to be undamaged and shaped like my Panda that doesn't ever crater, no excessive setback, and he doesn't appear to have any erosion around the pin hole. The only difference between our two actions is my pin is .062" and his is .075". Maybe he's got a full case of really soft-cupped fed 205's?
 
goodgrouper said:
I wonder what may be wrong with my buddy's action then....his fall is .230"...
Click to expand...

Fall under a quarter-inch could be the reason. My rifles are set up with 0.270" to 0.280" of fall.

It's possible to see a little createring with a 0.075" pin using warmer loads. It's nothing to worry about unless you are piercing primers. In fact, it's a good indicator that you might be too hot for the conditions anyway.

I've shot entire weekend matches createring primers. I also noticed (after the fact) that I had a hard time shooting aggregates with those loads - although I got a few little bughole groups. Too bad I was too dumb at the time to back the load off.

Greg Walley
Kelbly's Inc.
 
On cratering..every Remington varmint caliber that I have owned, all of which were loaded hot, had significant cratering, and never pierced a primer. My Viper, that has a .062 pin tip came with a 19# spring and a total fall of .200 has never had any ignition problems, including the appearance of fired primers. I reversed the trigger hanger and and the fall is now at .220. The spring was changet to one that is supposed to be 25#. I can't see any difference, except the dents in fired primers look more "normal" (are deeper). The larger pin tip has a little over 30% more metal to stretch in order to make a dent in the primer, with the same weight spring and pin, perhaps the extra energy of a longer fall is more important.
 
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Vern said:
How do you measure the "fall"?
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Its kind of a two step process the way I do it. The firing pin head extends out of the bolt shroud about 1/16" or so. With the bolt inserted into the action and cocked, measure the distance the pin head sticks from the back of the shroud. Now, drop the firing pin on an empty chamber. Then measure from the back of the shroud to the firing pin head. Now add those two numbers together and you have the total amount of fall.
 
I thought I would put out an update, I got the hanger today. (Again thank you Greg.) It was a .030 hanger, and to my suprise it changed the firing pin travel exactly .030. I now have .2575 of travel. (Travel before was .227 so I gained .0305 travel.) Now all I have to do is find time to go out to the range and see if it corrected the problem.
 
Well back to the old drawling board, still getting createred primers.
I pulled the fireing pin assembly and checked my cases, and they are fitting fine. The bolt drops anout a 1/4 way down, and there is resistance as I close the bolt the rest of the way down. My bolt is a .072 diameter.
 
Patrick, you need a smaller diameter firing pin to run those high pressure loads. There's no other 'fix' IMO, no mystery involved :) it's simply that your .072 hole offers too large an unsupported area for the pressure you're wanting to run....."new" and "spring weight" and "fit" and "fall" don't approach the problem which is too big a hole.

I guess a heavier pin might would do the trick, like 6-8 ounces heavier.....LOL. I wonder if anyone's ever measured the locktime of a half pound firing pin.

Get'cherbolt bushed


opinionby




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