doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Sticky opening gun

Any ideas on what the issue might be and what you would do to correct it would be greatly appreciated. I dropped this gun off at a local gunsmith nine months ago but he never got around to taking a look at it. Today I decided that for the small amount of money I have in the thing I can take a chance by attempting to fix it myself.

The primers show drag marks from the pins as well as the shape of the striker disks. There have been a couple of suggestions that there is a pressure issue but I am convinced that pressure is not the problem. This has happened with two relatively mild loads (9000 psi or less) and one factory load. The two reloads are standards in any manual and I have used them in different guns for almost thirty years without any problem in any other gun. I'm more inclined to believe that it is a problem with one or more of either the firing pins, chambers, or headspace.

Here are some dimensions. When seated in the chambers the rims of the shells are recessed by between .018" and .025" depending on brand of shell. I don't know if that by itself is excessive and the only other gun I checked gave numbers that weren't much different. Breaking it open after a shot has never been a problem. I only hunted with this gun on two different days but sometimes it was sticky after only one barrel had been fired, sometimes after both, and sometimes it opened without any difficulty at all regardless of whether one or both barrels has been fired.

After firing the pins protrude from the breech by .048" (R) and .058" (L). Both are pointed to some extent but the longer one has no radius at all. After firing the pins remain fully forward. If I remove the forend and break the gun open (or dry fire it without the forend on the gun) the pins stay in the fired position when the toplever is pushed to open the gun. If the forend is on the gun when the toplever is moved the pins rebound or retract, at least I noticed tonight that they do when the gun is either dry fired or fired with snap caps.

I don't have pictures of the chambers but I can take some if necessary. They are rough and they might be tight. Using a dial caliper case length gauge I am getting a chamber diameter of .67" in both barrels. That is as small or smaller than the outside diameter of either the comp-formed or HS Winchesters or the Fiocchis I measured. By saying the chambers are rough I don't mean from corrosion but they have tooling marks that give the appearance that there was not enough polishing after reaming. Both chambers have shallow spiral marks in a similar pattern to threads for a screw.

Thanks for any help. It looks like I will be tackling this issue myself.

Skip

I would say the primers are not seated far enough. On the edges you can see where they rub the gun when it is being closed. You can also see on the gun where they are rubbing when it is closed. I would correct that situation before anything else.

A 20ga chamber should taper from about .700" just ahead of the rim down to about .685" just where the forcing cone begins. I don't know how you are measuring but somehow doubt your caliper readings. If the chambers are indeed .670" they weren't finished, & I'm surprised you can even get a shell in. The pins look too pointed & perhaps too long as well, primer indents are certainly deep enough. I also suspect the timing of your cocking levers is off & hammers are not beginning to cock on initial opening of the gun.

2-Piper, you are correct. I posted the wrong number for the chamber diameters. They are indeed .70", the .67" was an average diameter of the Winchester shells I measured. The hammers do cock as soon as I move the toplever with the forend on the gun. In the picture below I tried to show how rough the chambers are. Sorry for all the glare.

Skip

In just two words: Espaniol clunkerisis quite endemic I might add.

Skip;
The chamber roughness could indeed be adding to hard extraction. However I tend to think your main problem is from the shape of the pins themselves. Even with perfectly timed cocking levers a slight movement of the bbls is necessary to start the hammers back. With non-rebounding hammers in then becomes necessary the shape of the pin nose allows it to cam back slightly with that first motion, & not tend to "Lock into" the indent. This is usually best accomplished by a full hemi-spherical shape to the nose.

Is there a number range that the pin should penetrate the primer? Since I already know how far the pins extend, and the gun is tight on face. Now I can take the barrels off and with unfired shells of different make and with different primers dropped in the chambers I can get a depth range. Then by knowing the answer to the first question I will know how much needs to be taken off each striker. It seems like I can touch them up with a file without removing them from the gun. That way every pass or two I can verify the length against the breech face. I am going to shoot it today with Fiocchi hulls and Fiocchi primers. They are quite low (6100 lup) and I'd like to see how they do. When I get home I will get some additional measurements. I appreciate the advise.



Jager, there's no doubt about it that a 70's Spanish gun is a crap shoot. I wasn't overly surprised but the problem wasn't serious enough that I considered sending it back and getting my three hundred bucks refunded. I got it to hunt with when the weather was at its worst and it has been raining here since Thursday night. Today I will take that gun to the marsh without any concern. It feels nice and aside from having to put my foot under the bottom of the receiver while pulling down on the barrels and stock to open it (well, maybe it isn't quite that bad) I am very happy with it. The proof is always in the pudding and once I get this bug worked out I know I will have a light little shooter.

Skip

Snipe Hunter:

Very nice pic. One of my favorite quarrys as it seems to be a cross between upland and waterfowl hunting. I use to have an English pointer gyp that would point them religiouly. I for one wouldn't mill any off the primer end of the strickers. Does it have striker springs? If so, add a little to the length or diameter. If not, get a spanner wrench and add a spring. Does the hammer rest on the striker out of battery?

Kind Regards,

Raimey
rse

Skip, I had the exact same problem with a recently built (2003 I think) Garbi model 101 sidelock; a pretty expensive gun, if Spanish (nothing wrong with most Spanish guns). Shortening the firing pins solved it. There is nothing wrong with your shells, new or reloads, or your chambers. If you can place fired shells in and remove them from the chambers easily, forget about the chambers. The problem is the firing pins; they are too long and need to have a hemispherical radius, not conical. I suggest you stop shooting the gun until you fix them or you will sooner or later break a firing pin. A fairly recent post discussed how far firing pins should protrude. Salopian suggested .055" but I think that may be too far. I measured 3 of my guns and all are in the .030"-.038" range. None have ever failed to fire a shell.
Joe

Skip,

I concur with the shape of the firing pins. I would bring a small stone with me to the field or range, and round the pins a little and try it to see if it improved, and you should be able to tell about how much more rounding will be needed after the initial test.

binko