Shotgun has random misfires

AL45 · November 7, 2014, 09:50 PM

I have an old Westernfield pump shotgun that has random misfires. I checked the primers and ever so often it has light primer strikes. It has a free floating firing pin (no spring) that appears to be in good shape. The area where the hammer strikes the firing pin looked rough so I lightly smoothed it with a fine diamond stone and this seemed to help a little. Could it be a weak hammer spring? Any help would be appreciated.

**JohnKSa** · November 7, 2014, 11:34 PM

If the spring is weak, I'd expect it to have consistently light primer indents.

My guess is that something is hanging up. Either the firing pin is catching or dragging on something, once in awhile or the hammer is sometimes hanging up or dragging on something and not delivering a full strength strike all the time.

If the hammer rides in a channel, I'd look at the edges of the channel and the edges of the hammer to see if there's evidence of the hammer dragging or hitting. Also check to see if the fit of the hammer on the hammer pivot pin is tight or if it's loosened up allowing a lot of side to side play or tilt in the hammer. That could let it hang up or catch on a part that it normally would miss if it didn't have that play.

Check the firing pin and firing pin channel to make sure there are no burrs that could be slowing the firing pin down.

DnPRK · November 7, 2014, 11:34 PM

There were many models of Westernfield shotguns, some made by Winchester and others by Stevens or other manufacturers. Which model do you have?

AL45 · November 7, 2014, 11:52 PM

This is a model 40n.

Blindstitch · November 8, 2014, 06:51 AM

I did a search and found this.

The Western Field Model 40N was a 12ga made by Noble for Montgomery Wards between 1953 and 1971.

Dixie Gunsmithing · November 8, 2014, 08:45 AM

Since it is intermittent, it could be a few things.

It could be bad ammo. Did you try any other brand, etc, and receive the same results? If not, then:

First, the bolt and firing pin could be dirty, and that keeps the firing pin from striking the primer hard enough. Also, the hammer could be dirty.

Second, the hammer spring is getting weak.

Third, the firing pins nose might be getting worn down, and some primers might not fire if they are recessed a little lower than others. The nose on the pin should be a domed or half-hemisphere shape, with no flatness.

tangolima · November 8, 2014, 09:41 AM

The gun may have developed headspace. I will check that after checking firing pin protrusion.

-TL

AL45 · November 8, 2014, 10:49 AM

I tried different ammo with same result. The firing pin looks fine. I cleaned and lubed the bolt, firing pin and hammer.

Dixie Gunsmithing · November 8, 2014, 11:26 AM

One thing you might try, before ordering a spring, is trying to give the old hammer spring a slight stretch. That could help show whether it is the problem or not. If it does fire okay afterwards, then order a new spring.

If it was to be headspace, as mentioned above, then it will be hard to repair. The bolts top rear could be worn and cause it, or the recess in the receiver that it sets into. The only fix would be either trying a new bolt, or setting the barrel back by its threads, and the latter would cost way more than it's worth.

I think this is a Noble model 40, and a breech bolt runs $40.00. Hopefully, it's not this.

The hammer spring, 17520A, is $3.10 from Numrich.

Blindstitch · November 8, 2014, 01:08 PM

Got any pictures or info to tell if this is a pump or bolt shotgun.

James K · November 10, 2014, 02:35 PM

If it is headspace, I think a worn/battered bolt seat in the receiver is more likely than a worn bolt. Unfortunately, that would not be economically repairable.

Jim

November 7, 2014, 09:50 PM	#1
AL45 Senior Member Join Date: December 12, 2012 Posts: 754	Shotgun has random misfires I have an old Westernfield pump shotgun that has random misfires. I checked the primers and ever so often it has light primer strikes. It has a free floating firing pin (no spring) that appears to be in good shape. The area where the hammer strikes the firing pin looked rough so I lightly smoothed it with a fine diamond stone and this seemed to help a little. Could it be a weak hammer spring? Any help would be appreciated.

November 7, 2014, 11:34 PM	#2
JohnKSa Staff Join Date: February 12, 2001 Location: DFW Area Posts: 24,971	If the spring is weak, I'd expect it to have consistently light primer indents. My guess is that something is hanging up. Either the firing pin is catching or dragging on something, once in awhile or the hammer is sometimes hanging up or dragging on something and not delivering a full strength strike all the time. If the hammer rides in a channel, I'd look at the edges of the channel and the edges of the hammer to see if there's evidence of the hammer dragging or hitting. Also check to see if the fit of the hammer on the hammer pivot pin is tight or if it's loosened up allowing a lot of side to side play or tilt in the hammer. That could let it hang up or catch on a part that it normally would miss if it didn't have that play. Check the firing pin and firing pin channel to make sure there are no burrs that could be slowing the firing pin down. __________________ Do you know about the TEXAS State Rifle Association?

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November 7, 2014, 11:34 PM	#3
DnPRK Senior Member Join Date: August 24, 2001 Location: LC, Ca Posts: 1,917	There were many models of Westernfield shotguns, some made by Winchester and others by Stevens or other manufacturers. Which model do you have?

November 7, 2014, 11:52 PM	#4
AL45 Senior Member Join Date: December 12, 2012 Posts: 754	This is a model 40n.

November 8, 2014, 06:51 AM	#5
Blindstitch Senior Member Join Date: April 14, 2013 Location: Milwaukee, Wisconsin Posts: 2,691	I did a search and found this. The Western Field Model 40N was a 12ga made by Noble for Montgomery Wards between 1953 and 1971.

November 8, 2014, 08:45 AM	#6
Dixie Gunsmithing Moderator Emeritus Join Date: April 27, 2013 Location: Ohio Posts: 1,923	Since it is intermittent, it could be a few things. It could be bad ammo. Did you try any other brand, etc, and receive the same results? If not, then: First, the bolt and firing pin could be dirty, and that keeps the firing pin from striking the primer hard enough. Also, the hammer could be dirty. Second, the hammer spring is getting weak. Third, the firing pins nose might be getting worn down, and some primers might not fire if they are recessed a little lower than others. The nose on the pin should be a domed or half-hemisphere shape, with no flatness.

November 8, 2014, 09:41 AM	#7
tangolima Senior Member Join Date: September 28, 2013 Posts: 3,808	The gun may have developed headspace. I will check that after checking firing pin protrusion. -TL

November 8, 2014, 10:49 AM	#8
AL45 Senior Member Join Date: December 12, 2012 Posts: 754	I tried different ammo with same result. The firing pin looks fine. I cleaned and lubed the bolt, firing pin and hammer.

November 8, 2014, 11:26 AM	#9
Dixie Gunsmithing Moderator Emeritus Join Date: April 27, 2013 Location: Ohio Posts: 1,923	One thing you might try, before ordering a spring, is trying to give the old hammer spring a slight stretch. That could help show whether it is the problem or not. If it does fire okay afterwards, then order a new spring. If it was to be headspace, as mentioned above, then it will be hard to repair. The bolts top rear could be worn and cause it, or the recess in the receiver that it sets into. The only fix would be either trying a new bolt, or setting the barrel back by its threads, and the latter would cost way more than it's worth. I think this is a Noble model 40, and a breech bolt runs $40.00. Hopefully, it's not this. The hammer spring, 17520A, is $3.10 from Numrich.

November 8, 2014, 01:08 PM	#10
Blindstitch Senior Member Join Date: April 14, 2013 Location: Milwaukee, Wisconsin Posts: 2,691	Got any pictures or info to tell if this is a pump or bolt shotgun.

November 10, 2014, 02:35 PM	#11
James K Member In Memoriam Join Date: March 17, 1999 Posts: 24,383	If it is headspace, I think a worn/battered bolt seat in the receiver is more likely than a worn bolt. Unfortunately, that would not be economically repairable. Jim