Delayed fire

[Bigguy1951]

Ok, went to work on the gun earlier and I found some clues. First off I will say that I think that Dusty Stevens was probably on the right track. I won't know for sure till I can get the gun back on the range next week. I started off with Larry's suggestion and took the same twelve shells fired yesterday and primed them with the Tulammo primers in exactly the same way that I had originally loaded them. Not one of the primers had a delayed fire. This is not conclusive though as I had taken the gun apart yesterday and I didn't torque everything down as I expected to take it apart again. Took the bolt apart and it was actually very clean, maybe too clean as it is fairly dry. There was some surface rust at the bottom of the threads where the bolt shroud screwed into the bolt body and under the firing pin nut on the firing pin. The inside of the bolt was clean as well. None the less I cleaned all thoroughly and lightly oiled the firing pin spring and body as well as the threads under the firing pin nut and where the bolt shroud screwed into the bolt body. Dusty seemed concerned that I had gotten some epoxy around the trigger, but I had packed the trigger inlet with clay before bedding and I had filed the little bits of bedding overflow around the inlet to assure clearance. The rear receiver screw however was still a little proud of the top of the tang. The Weatherby firing pin nut has a long tang on it that slides back in forth in a slot just above the rear receiver screw. A close examination of the tang shows drag marks. I did shorten the screw when initially reassembling the gun after bedding, apparently I didn't shorten it enough to allow for the higher torque of final assembly.

I want to thank everyone that has helped with this so far. This forum is a true fountain of knowledge .

 

[Dusty Stevens]

Let us know how it goes. Sharpie marks work to find drags and the best clue was to go back to what you did before it stopped working- in this case screws too long or bedding in a bad spot. Sounds like youre on the right track. 10 less lbs of torque you'd have never known

 

[Zero333]

Any time you have a case that has large case capacity and is filled with slow burning powder . Basic 101 in reloading always use mag primer . Has been that for ever.
When seating primers they must be seated firm at the bottom or you get delayed ignition. That hasn't changed from the 50 tys when I started loading. Larry

You are correct but I have something to add.

Magnum primers were made for the 378weatherby. Before the 378, magnum primers did not exist.

 

[Bigguy1951]

Took it to the range today and I still am having the delayed fire. It is definitely not the hard seating. I did all the primers with very hard seating. There are only a couple of options left I think. It is possible that there may be some dragging of the firing pin. I will check it this afternoon. I really think that the firing pin spring is weak. I have hand compressed a lot of different firing pin springs and this one seems weak to me. This is purely subjective though but still a possibility. I forgot to add that the firing pin imprint on the cases that delay fired were easy to pick out, a much shallower impact.

 

[Dusty Stevens]

Check your spring on a bathroom scale. Does it sound different each shot while dry firing?

 

[Bigguy1951]

Not sure exactly how to test it on the bathroom scale Dusty, removed and compressed on a straight rod? It does not sound different when dry firing. How far should the pin protrude from the bolt face?

 

[Dusty Stevens]

Put the tip into a deep well socket and push down on the scale to see how many lbs it takes to compress. Not sure on a savage fp protrusion but somebody will stop by with those specs soon

 

[Bigguy1951]

This is a Weatherby Dusty.

 

[Bigguy1951]

It took 24lbs to nearly complete compression. My bathroom scale is digital/load cell and only gives a final weight. Had to play with it some to get that number. At about 3/4 compressed the weight is 14lbs and it goes up quickly from there.

 

[243winxb]

http://thefiringline.com/forums/showthread.php?p=4928827#post4928827 Like this?

If the bullet moves to soon from light neck tension, pressure will not build correctly. A long OAL when trying to get close to the rifling may be a problem also.

Good info at the link, if your read it. This problem is nothing new. First try a different brand of magnum primer. IMR4350 is not hard to light, but a starting powder charge may produce a secondary pressure spike, caused by the bullet moving to soon. This acts like a plugged bore, raising pressure. Neck tension- Measure the case neck diameter before and after seating a bullet. After seating, the neck should expand a minimum of .002" or more for good neck tension. The bullets bearing surface should be in full contact with the case neck. A OAL that is to long, with little bullet shank in the case neck, will let the bullets move too soon. Last, get a case gage and full length size the brass with minimum shoulder set back.

 

[Bigguy1951]

Well, sometimes I do things the wrong way, but I can usually work out the right way, I hope. Anyway the spring preload is 19+/- 0.5 lbs. Still hard to get accurately on a load cell bathroom scale. The spring weight in the cocked position is 23 lbs. I couldn't find any info for this gun for the proper weight. I did check the firing pin protrusion, proper range is .058-.069 inch, and mine was .062. I did find a wear spot on the firing pin about 3/16" in front of the pin stop. I chucked the pin in a drill and very carefully lightly filed this area with a small fine file. I reduced the diameter by .002", polished it with 400 grit emery and re-blacked the pin. I have found a case on the net where an owner of a mid 70's Mark V did have to replace his spring because of weak strikes. This is a single event of course but does show it can happen. I'm not satisfied with the results so far and keep searching for the link between removing the trigger assembly for bedding and these delayed firings. I noticed yesterday that the trigger assembly, even though located by a screw through the receiver and a fairly large protruding pin at the front of the assembly, can be set in place so that the trigger sear rubs on the side of the receiver. I removed the assembly, and moved it around getting it to touch on both the left and right side of the receiver when it was fully tightened in place. It is possible that I had it lightly rubbing the receiver as I felt that the locating system would not have allowed that much movement and did not take precautions to prevent it. So much to check for such a simple thing.

 

[savagedasher]

Well, sometimes I do things the wrong way, but I can usually work out the right way, I hope. Anyway the spring preload is 19+/- 0.5 lbs. Still hard to get accurately on a load cell bathroom scale. The spring weight in the cocked position is 23 lbs. I couldn't find any info for this gun for the proper weight. I did check the firing pin protrusion, proper range is .058-.069 inch, and mine was .062. I did find a wear spot on the firing pin about 3/16" in front of the pin stop. I chucked the pin in a drill and very carefully lightly filed this area with a small fine file. I reduced the diameter by .002", polished it with 400 grit emery and re-blacked the pin. I have found a case on the net where an owner of a mid 70's Mark V did have to replace his spring because of weak strikes. This is a single event of course but does show it can happen. I'm not satisfied with the results so far and keep searching for the link between removing the trigger assembly for bedding and these delayed firings. I noticed yesterday that the trigger assembly, even though located by a screw through the receiver and a fairly large protruding pin at the front of the assembly, can be set in place so that the trigger sear rubs on the side of the receiver. I removed the assembly, and moved it around getting it to touch on both the left and right side of the receiver when it was fully tightened in place. It is possible that I had it lightly rubbing the receiver as I felt that the locating system would not have allowed that much movement and did not take precautions to prevent it. So much to check for such a simple thing.

With it being a belted case . I would check the case Belt area . Distance from the top of the belt to base. Also the diameter of the belt.
Larry

 

[Shaggy357]

I am going to bet you have bad primers......here is the thinking process from reading all of the posts: One round fired fine. Primers alone fired fine. You have checked bolt, firing spring, bedding etc. The only time you seem to get the hang-fire is with loaded ammo. A bad primer may go "bang" in an empty brass....but may not be firing as hot a flame as is should. Now throw in a load of powder, add a bullet, and you stifle the noise and amount of flame being created. Consider a cool flame going into the powder, slowly igniting the powder, and just starting the pressure to build. Bullet is likely part way out of the case before enough pressure builds and the remaining powder in the front of the case ignites. In addition to the dent in the case...likely sooty residue on the case, and likely unburned powder in the barrel.

I had a similar experience in 1986. Remember the year because it was at my very first silhouette match. Practice ammo had all fired fine. Sighting in ammo fired fine. When I started shooting I was good for first twenty shots. Then I was into the second box of 50. This ammo used a different box of BR4s...several hang fires and several did not go off. My first competition match, people helping me, and my gun wont fire...felt like a fool, until I confirmed the primers were bad. I tossed out the rest of those primers and never had the problem again....

Sounds like what you have....but you will have to confirm....

Hope this helps.

Steve

 

[Bigguy1951]

I have certainly considered that Steve and I believe it to be high on the list. But until I check everything I won't be comfortable.