Lite primer strikes - Charles Daly 12Ga pump

[JIMinPHX]

I'm having a problem with lite primer strikes on a Charles Daley 12 Ga pump gun (made in Turkey). Has anyone else run into something like this???

[JIMinPHX]

I took it apart & cleaned everything up real well. I found that the part of the trigger housing (plastic) that holds the hammer & the hammer spring plunger were pinching the hammer & the plunger which added some drag. I put a spacer tube in there to hold the plastic rails open with about .003-.005" of clearance. That helped some, but the strikes are still not that robust. What is the best way to increase the authority of an inertial firing pin system? Would adding weight to the hammer help? I don't have room for a heavier spring.

[JIMinPHX]

Now with everything clean & moving freely, most of the strikes look more or less OK, but every once in a while, I get one that barely marks the primer. I hear the hammer go "click" loud enough, but no boom. Has anyone ever had a pump shotgun do that before?

[John Taylor]

Could be the bolt is not all the way into battery ( closed and locked ) when the trigger is pulled. This will cause a partial block of the hammer and not have a good strike. Make sure the whole action is clean and the bolt goes into full lock.

[JIMinPHX]

Thank you for responding John. That was one of the first two things that I checked this afternoon. I tried a softer firing pin recoil spring, then I put a piece of masking tape on the area of the hammer where it would hit the slide block safety tang if it wasn't fully locked in battery. The tape didn't get a mark on it, so I don't think that was the problem.

I just now noticed that the marks in the hammer where it hits the firing pin are off center. They are not off center far enough for the hammer to hit outside of the clearance cut in the bolt, but they are off center none the less. I'm thinking that maybe if the hammer is hitting the pin far enough off center, that maybe that makes the pin bind a little. I'm thinking about making up an offset hammer to try. Boy, I wish that I could just buy a spare hammer for this thing & bend it a little. I don't want to do that to the original, because if I break it, then I'm completely out of luck.

[Mk42gunner]

Could be excessive headspace too. I have seen a well used 870 that needed a new locking block to move the bolt far enough forward to reliably fire.

Really off the wall suggestion-- make a titanium firing pin.


Robert

[JIMinPHX]

Do you think that a firing pin that weighs less would work better??? That's counter intuitive to me. I would expect a pin with less weight to move faster, but carry less energy. I would expect that it would give less of a dent to the primer. Then again, I used to think that lead boolits could not be shot over 1,000fps without terrible leading & I now know that's not true. Intuitive doesn't always equal true.

Back to the headspace issue - How do you measure headspace on one of them & how much is acceptable? The bolt to barrel lockup looks to leave about .015-.020" of space between the rear of the shell & bolt face when everything is locked up. That doesn't seem excessive to me, but I really don't know how much is too much on one of those. I think that I could probably machine out a small section of the (looks like aluminum) barrel tang & bolt in a steel spacer to shorten up the headspace if I had to.

[Mk42gunner]

I don't know for sure about the firing pin. When I went to Armorers school, the instructor told us not to use all titanium ignition parts in 1911's. He said that a firing pin or a hammer was okay, but not all. When I hear inertia firing pin system, I think of a 1911, where the firing pin isfree to protrude as much as it wants to. Like I said in the first post, it was an off the wall suggestion.

As far as measuring the headspace, I have an adjustable headspace gauge for 12 gauges. Iwill dig it out tomorrow and measure a couple of Remington 870's. That will give you an idea of how much space should be between the rim recess and the bolt face. I just have to remember which tool box it is in.

.015-.020" sounds like a lot of space to me. A K-frame S&W is supposed to have between .004 an .010" space between the head of the cartrige and the recoil shield, according to the guage I have. I do realize these are different types of guns, but....


Robert.

[JIMinPHX]

Thanks,
I'd appreciate knowing what headspace your 870s measure.

Jim

[Mk42gunner]

Jim,

I measured my Grandpa's duck gun; a field grade 870, 28" Modified choke that was bought new in 1955. It closed on .010", would not lockup on .011".

The other one was an 870 TB that I have no clue how old it is, I bought it as a riot gun that "had the hunting stock and barrel, too." This gun had the flex-tab conversion done when it was a riot gun, and I think a new bolt, the one in it is blued, not chromed. It would close on .008", but not on .009."

The head of the guage is marked 0=065 so I am guessing that from rim recess to bolt face should be from .065-.075". Body dia is .800" Rim dia is .879". No other markings on the guage itself, except for the micrometer scale, no manufacturer's name at all.

My camera is broken or I would send you a picture of it.

Robert

[JIMinPHX]

Thank you for posting that Robert. That helps me a lot. I had searched the internet looking for 12 ga chamber dimensions but didn't find any. Eventually, I went down to Sportsman's Warehouse & bought a copy of the Lyman Shotshell Reloading Handbook(which I really should have anyway). That had some slightly blurry drawings that gave a minimum dimension, but not the max. Your numbers gave me some useful perspective.

At first I did a quick farmer's headspace measurement, by putting a wad of boolit lube on the back of a spent shell, chambering it & then measuring the thickness of the lube pancake after it got ejected. The pancake was nearly .030" thick, which seemed pretty darn bad. But then I got motivated & turned down a plug gauge on my lathe. The Lyman drawing seemed to indicate that the chamber to breech face distance should be measured at a contact diameter of .8500". From the Lyman drawing, it looks to me like your diameter of .879" is the outside of the chamfer. I made my body diameter .7985" & my rim .8501" with a sharp edge. I didn't have the nerve to go after that last .0001" to make it perfect. The rim measured .0711" thick.

When I chambered the gauge, it seemed pretty snug, but the gun locked up normally & my slide came all the way forward to the mark I had made for it's normal closed position. When I put a piece of .004" thick masking tape on the end of the plug, I could no longer get the action to lock up. I don't think that the headspace is too big after all. Your numbers & mine were much closer than I expected. I had thought that a firearm design with so much inherent slop in the mechanisms would have much greater tolerances than we are seeing. I guess that I was wrong on that count. I guess that they made them good where they needed to be good after all.

Unfortunately, something that my wife said to me the other day is starting to ring in my head. She said "you don't think that your bullets could be the problem...do you?". Since .030" of wax fit on the back of a spent shell, I may have a rim problem or two to look at. It's going to be really embarrassing if I have to admit to my wife that she caught a problem that I missed...on a gun.

The Lyman drawing is below

[JIMinPHX]

After looking at that Lyman drawing some more, I realize that I had been misreading something. I had thought that the .0716" dimension was the minimum headspace length. I now realize that it was the minimum length from the base of the rim recess to the bolt face. The headspace length at .8500" diameter should be .0576-.0716" according to this drawing. That means that my chamber just about makes it on the very high end of the headspace range. I might need to look around for a new bolt latch.

[JIMinPHX]

New bolt latches or "locking blocks" as Charles Daly calls them, are like hens teeth. Numrich is out of them & I don't know where else to look. A local gunsmith can insert a ring into the rear part of the chamber & then recut the rim recess to move it back a little. That's one way to close up the headspace. If anyone has a better suggestion, I'm all ears.

Thanks,
Jim

[Mk42gunner]

Jim,

Your headspace sounds okay to me. I tried to find an online picture of your gun, but dialup is being a pain today.

I'm really not familiar with the Charles Daly shotguns, so bear with me on these questions.

1. Did this gun ever fire reliably for you?

2. You said this is an inertia firing pin system: is the pin straight, or does it have a leg on the back? It isn't binding in the hole, is it?

3. If you push the firing pin into the recess from the rear of the bolt, how far does the tip protrude?

4. Is there anyway the hammer could be dragging on the bolt before it hits the firing pin? The offcenter marks on the hammer don't sound right.

5. There's nothing like doing diagnostics on an unfamiliar mechanism that is 1000 miles from home. Could you post a picture of the trigger mechanism, bolt, and firing pin?

There's not much that ismore frustrating than a shotgun that won't reliably fire. I had a 16 guage Iver Johnson that was like that, the dang barrel would work on three different frames; just not the one it was suppossed to.

Robert

[JIMinPHX]

the gun was reliable for the first 50 rounds with AA shells. I'm now using reloaded Universal hulls. I'll try some better ammo either today or tomorrow.

The pin is straight. If I take the spring off of it, gravity is enough to move it through it's entire range of motion as I turn the bolt 180 degrees. It moves freely 100%.

The firing pin protrudes .105" past the front of the bolt face when pushed fully forward.

The mark on the hammer is off center, but not off the edge. I measured the hammer width & the width of the clearance cut in the bolt. The hammer still has clearance. I don't see any hit marks on the rear of the bolt. The hammer is off center in the frame by .005". The firing pin & bolt assembly are off center by .050". The total mismatch is .055". The hammer is .143" wide. The clearance cut in the bolt where the hammer hits is .312" wide.

Pictures coming shortly

[JIMinPHX]

Pictures below

[JIMinPHX]

Here's a kick in the head. I managed to get out into the desert tonight just before sun down & pop off a few rounds. I started with a box of Universal factory loads. No problems there, but they patterned terribly. Then I tried 20 of the same handloads I have been using. They were flawless too & patterned much better. I'm not sure what is different now, but I had no misfires tonight. I would have run more shells through it, but the light started to fade. I'll try a bunch more next time.

[John Taylor]

Sounds like you fixed it.

[flounderman]

check the fireing pin protrusion. you could have cup shaped heads on the reloads and if the pin has a short protusion, it may not be reaching far enough. you should be able to shim the spring. too light a hammer could be the problem, but shimming the spring will help. faster lock time, also

[JIMinPHX]

I checked all the spent shells that I shot tonight. The primer indentations all look pretty similar. There are a few that look maybe 10% different, but that's at the outside & just 2 or 3 are like that. I don't know what might have changed since the last time I shot it. I've had the gun apart & back together again about 25 times now. I thought that I did it the same every time. I'm going to have to go back & reinspect the spent shells from the last time I went shooting. Something must have changed since then. I just don't know what it is. Not knowing, really bugs me.