Question about channels in face of 1906 20ga VH
 

This is #140131 20 ga VH whose letter says it was ordered and sent to Los Angeles with 26" barrels, straight grip and choked full and full. There are no repair records. From the pictures you'll see it's now got a "higher grade" replaced pistol grip stock (with a Remington grip cap) and re-blued barrels that are choked RH/IM and LH/F. Originally weighed 6lbs and remains the same although the wrist of the stock is about 1/2" thicker by comparison to a 0 frame 1903 16ga (assuming the same frame size warrants the same stock dimensions). All serial numbers match but the safety slide is not original; it's from a later production period.
Please look at the breech face grooves - can anyone explain why they were filed there? Locks up on face and shoots well (at least when someone who knows how to handle it shoots it..:)

Pierced primer gas escape channels.

Otherwise, a pierced primer can blow gas into the action and crack the stock head or worse under extreme circumstances.

I am not aware that Parker ever cut these channels ,so I assume Parker did not consider that a pierced primer possibility warranted the channels in their guns. Obviously an owner could have this done in an abundance of caution.

Nice looking modified Parker.

Thanks, Bruce - never heard of that. Would the pierced primer be associated with a mis-fire? I didn't realize primers had that much explosive force but now wonder if that's the reason the stock was replaced.
Thanks also for the compliment; I call her my Hollywood gun since she was shippped to LA originally....she's been stepped on a bit - replaced a cracked and crumbling Jostam Hy-Gun pad with the Hawkins, rechecked the forend and refinished the entire stock so the wood matched. The forend was visibly years older, darker and worn than the stock.

Jim, Nice gun! That would be my guess too.

Jim, I have seen one pierced primer incident, without ill effects at all. It was a semi auto of some type, don't recall. It did nothing.

The idea is that the firing pin ( or Parker hammer nose) pierces the primer because the primer is not seated deep enough or the strike is too deep. The primer ignites but because there is a hole through it, gunpowder gases backflow through the primer hole and into the gun. Within the confined space of the action body, the gases can fracture the wood joining and or escape through the trigger slots, so the concern goes.

I have never seen this happen but I am aware that the gun club experts say that it can.

I wonder if anybody here has seen this happen with bad results? Again, it must be infrequent because the manufacturers do not put the grooves in . There are a few vintgage guns with gas grooves but I've forgotten which makers.

Primer Strength
 

I have seen a number of hand loaded shells, some of them my own, where powder does not get loaded into the shell for one reason or another. The primer explosion will eject 1 1/8 ounce of shot about 50 or so yards and sometimes also ejects the wad but usually the wad stays in the barrel. It's very critical that the wad, if still in the barrel, be removed before firing the next shell or you will blow the barrel. I've seen blown barrels but I've never witnessed one. And I don't really want to. Cheers, Tom

I agree with Bruce. The gas relief grooves were milled or filed by someone who was trying to solve a problem that did not exist. Gas relief grooves are part of the original equipment of some guns, but not to solve a problem that normally exists in shotguns. Platinum plugged gas relief valves are a standard piece of equipment on high grade muzzle loading fowlers, but I have never seen such a gun with a missing platinum plug.

i have personally seen a hammer double that pierced the primer it will about blinded the person who fired it....the escaping gases willcome by the firing pin and do damage....but i personally have never seen a hammerless gun do anything...charlie

I experienced a blowback through the firing pin hole from a pierced primer in my G
HE 16 gauge about 10 years ago, which I sent to Turnbull for repair afterwards and let him talk me into a complete metal restoration as well. I have posted pictures of the gun on this site several years ago. The shell was a friend's handload, one of those red all plastic hulls, and it felt a little hot when fired, both by noise and by increased recoil, and the case mouth was ragged when extracted (Turnbull did it--I could not open the gun more than a crack after firing) as if cut by the shot charge entering the forcing cone. Chambers had been lengthened to 2 3/4 by a prior owner and the shell was 2 3/4, but it was about 1/8 inch longer when fired than other fired cases from remington and winchester. Bottom line is I think the shell was hot to begin with, and think that the excess pressure must have pushed the primer back on ignition so as to cause it to pierce. Anyway, the gas blew back through the firing pin hole and knocked a 1" long by 1/2 inch deep chunk out of the stock head on the upper left side, which for some reason didnt strike me as it passed by my cheek and eye on the way out. I was wearing glasses, and felt the gas pressure, but no wood. Turnbull patched in a new piece and finished it so it was almost invisible. Thats all I know, but I don't shoot anybody's reloads any more, and have not experienced another hot shell or pierced primer since that one. I think I recall someone else posting a picture of a repaired stock with just the same sort of chunk knocked out of it. Looks like it may be a relatively rare occurrence, but with a consistent mode of failure when it occurs. Be careful out there.

Mike, Charlie, Bill, Tom, Bruce and Dave - thanks for your replies and perspective. I shoot low pressure shells so only concerned to the extent of normal safety. Given the number of changes this gun has seen, does anyone have insight on the diameter of the Remington replacement stock versus an earlier Parker stock? Here's a photo comparing a restored 16ga 0 frame with the 20ga - there's almost a half inch difference in wrist diameter.

I think as a general rule, Rem Parker stocks are a little thicker in the wrist than say 1910 Parker Bros stocks. Whether it was done to reduce stock wrist fractures, I don't know, and it would be only speculation. I am not aware of any Parker factory or Rem notes about the increased size.

Here are a few pictures of what happens when a primer is pierced. Fulton converted to a 454. Unfortunately what was a beautiful proffesional job in all other aspects, turned into a mess because the firing pin was too long. I purchased this gun which had never been test fired evedently. I took it to a friend whom is a Gunsmith. He took it to the test tunnel down stairs and told me to wait, as the policy was others can not be down there when he did test firing. I heard the report and a few minutes later he came up and said the gun blew up. If not for him wearing glasses it would have been serious as the glasses where horribly pitted. Needless to say one call to the company I recieved it from, and my money was refunded.

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I have a Meriden/Remington transition skeet gun with a straight grip that is slim as slim can be. Maybe late Remington guns are thick wristed but this one sure ain't.I just measured the circumference of the wrist as I shot this gun today. It measures 4" in circumference.

Funny we should be talking about pierced primers....Today a my local club one of our trapshooters pireced a primer on a factory loaded Winchester AA 1 1/8oz. load of 7 1/2 shot in his Remington 1100 trap gun. Split the stock right above the wrist...Pretty bad too....:eek:

My 1887 Remington hammer 12ga pierces a lot of primers, but just barely. It has strong mainsprings and maybe someone made the firing pins a bit more pointed, tho they don't really look it. I've never had any ill effects from it other than a bit of blacking around the piercing. This blowing wood off a stock is new to me. Never heard of such a thing. It seems to me that the older paper shells, especially the ribbed Remingtons, have much heavier metal on the striking surface of the primer so maybe the older guns had strong springs for a good reason??

That .454 Fulton looks like an extreme case of long firing pins. Jeez. I bet that guy wears more than just glasses when he test fires anything from now on.

Irrefutable evidence, Phil. Thanks for the photos! This has been very instructive for me.
Jim

What are the physics of a pierced primer causing that damage? I just don't see it. I had a sixteen Flues that pierced primers but no damage. I thought the problem with a gun that pierces primer was blowing the products of primer burn (crud) into the action through the firing pin hole and gumming things up.

Not challenging, just trying to understand.

Best,

Mike

Think of it like being in your car with your bird dogs after giving them a lot of steak trimmings or they found a dead deer.


The one pierced primer I saw had a hole all the way through, so obviously the expanding powder burn gas will blow back through the hole into the action through the firing pin or hammer nose hole. Like the dog, some goes out the front, some goes out the rear. Not very scientific explanation I suppose, but if necessary, I suppose some of us, like me, Flanders or Austin could provide a formula for rate of gas expansion, Bernoulli effect, venturi effect, momentum of ejecta, and other parameters.

This is a matter of basic physics. It's just a matter of how large a hole gets pierced. If it's a large hole there's a lot of pressure from the powder ignition, 11,000psi in some shells, and hence volume of air that can backfeed through the primer into the gun. It's the combination of the primer and the powder ignition that does the damage. A tiny hole and not much happens. Remember it's ps i, as in "inches". Pounds per square inch. The more square inches of hole, the more volume of air is going to get through. The PSI remains the same regardless but the hole size controls the volume of air that can pass through. A little hole lets a little through, a large hole lets a lot through. The holes my Remington makes are pinholes of approximately .2mm so the leakage is minimal. That .454 looks like it punched the primer clean through and into the shell so it's not at all surprising the amount of damage. It probably punched the hole in the bottom of the primer pocket clean out to the diameter of the firing pin.

And, of course, once the thin metal of the primer has been breached it is only a matter of miliseconds during which time the hole becomes larger.

Roger that Dean. I'd have to wonder if the gunsmith who converted the Fulton didn't put the coil spring off the front end of a '66 GMC pickup in for a hammer spring on that thing. It looks like it might have driven the primer anvil right into the powder charge.

Richard and Roger you are both spot on.
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