Put the original hammer spring back and see if the problem goes away!

 

Put the original hammer spring back and see if the problem goes away!

Ill definitely do that but the problem only shows up every 100 rounds or less so I was hoping somebody might have had the same problem

 

I had a similar problem with my Mossberg 500. A new hammer spring fixed the problem. Haven't had a light strike since

 

I wanted to put the Mcarbo kit in, because the trigger pull was too heavy, in an M500 that I got not too long ago. I was only going to put the trigger spring in because, I figured the hammer spring was strong enough, but after shooting it a bit with the standard springs, I got a light hammer fall about 1 in 50 with the standard springs, so when I installed the Mcarbo kit, I put both hammer and trigger springs in. The replacement seems to be better, but I still have got an occasional light hammer fall even with the new Mcarbo spring which is obviously heavier than the standard.

My read on the situation is you are better off with the replacement spring, but the problem can still appear at times, and my guess is that it is not an optimal design of hammer. That is not too unusual, quite a few shotguns have less than a perfect design of hammer, like for example the Winchester SX1, and some Browning O/U seem to have a light fall on the hammer of one of its barrels, bottom was it?

My Remington V3 gets an occasional light fall, maybe one in 200. One of the better designs in my opinion is the Rem 1100 and 870 triggers, but I have even managed an occasional light fall on one of these, like maybe one in a thousand.

Then also it is possible that something other than the spring is the culprit, like maybe a shell not fully seating in chamber, or maybe a loose barrel that leaves the barrel slightly forward of optimum position, all in all if it only screws up one in a 100, I would just live with it, while trying to see that everything is clean and in position, and let more time pass. It might even be inconsistently made primers, who knows? It is not a perfect world.

 

If a hull has a thin rim like many WWAA hulls you can get failures to fire.

 

As Curly said, it could be ammo related, but my guess is that it's the hammer spring. I would suggest you put the original back in (as Curly also suggested).

What puzzles me is why Mcarbo (or whomever) would suggest replacing the HAMMER spring in the first place. While the hammer spring might have some very small influence on the weight of the trigger pull, the overwhelming factor is the trigger spring.

 

Putting the original back in does not make sense to me. My original had more failures than the Mcarbo replacement. The Mcarbo replacement hammer spring is stronger, giving heavier hammer fall.
If it misfires with the Mcarbo, it is even more likely to do so with the original. Of course I could be missing something, but like I said it does not make sense to me.

 

If a hull has a thin rim like many WWAA hulls you can get failures to fire.

That makes sense to me, I think my failures what very few I had with the Mcarbo spring was with Winchester ammo. Also I suspect that a slightly deep rim cut in the chamber could cause the same problem, and possibly a slightly deep primer seating, also a slightly short firing pin. Like I said, its not a perfect world.

 

You can't go by comparing a dimple in a primer/shell that doesn't fire with a shell that does fire. The reason the fired shells have a deep dent is due primarily to the setback force that occurs when the shell fires. A shell that does not fire obviously will not experience any setback force.

The problem could also be a dirty trigger assembly, especially around the hammer and hammer spring. Also, you said that the gun is 7 years old. If you've used the Mcarbo spring in the gun for 7 years, that may have weakened the spring enough to cause the occasional misfire.

The problem also might be an eroded tip on the firing pin. In short, it could be due to MANY different things. Since you've still got the original hammer spring, it costs you nothing to put it in the gun and see what happens. In my experience, not only with my personal guns but also from reading and participating on this board for 16 years, the most likely suspect for misfires from semi-autos and pump guns is a weakened hammer spring. Suggest you replace the hammer spring and clean/lubricate the trigger assembly and then let us know what happens.

 

Hi everyone I have an intermittent issue with my Maverick 88. I've had it for 7 years and it's always functioned properly until recently. Once in a while it will have a light primer strike where the primer is slightly dented but not enough to set it off. But then the next shot will go off with a deeply dented primer so it's not as if it's just a weak primer strike all the time, it's only occasionally.
I've cleaned out the bolt and firing pin channel and the only thing I can think of is that I replaced the hammer and trigger return springs with the Mcarbo set in order to lighten the trigger pull. I've read through tons of reviews on that spring kit and never came across one that mentioned the new springs causing this problem.
Have any of you guys had an issue with the mcarbo springs? Like I said I would think that if it were a weak hammer spring that all the primers would have a weak dent. Is there anything else that could be causing this intermittent problem? Thanks in advance!

You can't go by comparing a dimple in a primer/shell that doesn't fire with a shell that does fire. The reason the fired shells have a deep dent is due primarily to the setback force that occurs when the shell fires. A shell that does not fire obviously will not experience any setback force.

The problem could also be a dirty trigger assembly, especially around the hammer and hammer spring. Also, you said that the gun is 7 years old. If you've used the Mcarbo spring in the gun for 7 years, that may have weakened the spring enough to cause the occasional misfire.

The problem also might be an eroded tip on the firing pin. In short, it could be due to MANY different things. Since you've still got the original hammer spring, it costs you nothing to put it in the gun and see what happens. In my experience, not only with my personal guns but also from reading and participating on this board for 16 years, the most likely suspect for misfires from semi-autos and pump guns is a weakened hammer spring. Suggest you replace the hammer spring and clean/lubricate the trigger assembly and then let us know what happens.

OK yeah I'll definitely put the old spring back in and see if that fixes it. I'm just surprised that all the reviews on the mcarbo kit are so good without anyone reporting the same problem. An a related note, is it remington primers that are known to be the hardest? I think it was remington loads that I had the trouble with but can't remember for sure.

 

One thing nice about changing the hammer spring back in, is that it is easy. While you have both springs out, you might try compressing them. When you do, I suspect you will find the Mcarbo hammer spring is stronger, which means it is going to hit harder. Generally speaking when you have light hammer falls, making them hit harder is the solution, so you may or may not decide to put the original back in at this point. It would be interesting to me to know which one is stronger. In my case, the Mcarbo hammer spring was stronger. The Mcarbo trigger spring is weaker, in order to give a lighter hammer fall. Changing the trigger spring can be a real bugger, if you let things come apart, but at least you won't have that problem with the hammer spring if the procedures are similar to the M500.

The Mossberg trigger is a pretty good simple design, but it does have the shortcoming that it has that long tang on the rear and this makes you have to use a stock that allows that long tang clearance in order to remove trigger group for cleaning. Other than that they did a pretty good job on the design. At least this is true on the M500. I assume the M88 is pretty much the same except for the safety.

Also, Mcarbo says they have a lifetime warranty on this trigger kit, so if your present spring has got weaker, I suppose they will replace it.

 

One thing nice about changing the hammer spring back in, is that it is easy. While you have both springs out, you might try compressing them. When you do, I suspect you will find the Mcarbo hammer spring is stronger, which means it is going to hit harder. Generally speaking when you have light hammer falls, making them hit harder is the solution, so you may or may not decide to put the original back in at this point. It would be interesting to me to know which one is stronger. In my case, the Mcarbo hammer spring was stronger. The Mcarbo trigger spring is weaker, in order to give a lighter hammer fall. Changing the trigger spring can be a real bugger, if you let things come apart, but at least you won't have that problem with the hammer spring if the procedures are similar to the M500.

The Mossberg trigger is a pretty good simple design, but it does have the shortcoming that it has that long tang on the rear and this makes you have to use a stock that allows that long tang clearance in order to remove trigger group for cleaning. Other than that they did a pretty good job on the design. At least this is true on the M500. I assume the M88 is pretty much the same except for the safety.

Also, Mcarbo says they have a lifetime warranty on this trigger kit, so if your present spring has got weaker, I suppose they will replace it.

I should clarify, I've had the gun for around 7 years but only had the mcarbo springs for a couple years and probably only has <100 rounds through it with the mcarbo springs.
Today I put the original hammer spring back in. While both the oem and mcarbo springs were out, I squeezed them and noticed that the mcarbo spring is slightly longer and very slightly easier to compress than the oem spring. So I put the oem spring back in and I'll try to get out some time soon and see if any light primer strikes happen.
On a related note, when I was researching I found out that the 590a1 has a dual hammer spring whereas all the other mossberg pumps use a single spring. Does anyone know if this is because the seals had issues with malfunctions during their trials? It seems like the mossberg pump guns have a bit of a history of light primer strikes. I know they specified a metal safety button among other things. Anyway thanks for everyone's help so far!

 

I would suspect the ammo since it happens so rarely-hard primers.

 

Just speculating here, thinking out loud. If 590 has dual springs, what does that tell you? The 590 is a more robust model 500, made more for military and police, the trigger housing is aluminum, not plastic for example. So why do they put two springs on the hammer in this more robust model? First guess off the top is they probably were trying to eliminate light hammer fall more positively. If they never had light hammer falls in the M500 they probably would have stuck with just one spring in the 590 also. Case in point, the original SX1 had dual hammer springs, why, I would bet they had light hammer falls in their prototype giving fail to fire so went to dual springs in the production model. That was the stage one trigger. Later they went with a heavier spring and just used one, that was the stage two trigger. But, light hammer falls is a pretty common SX1 problem, I experienced it on about 3 out of 6 that I owned. Also there are heavier aftermarket hammer springs available for it, and I put those in mine that I owned.

Therefore it would be very easy to believe the Mossberg trigger, has experienced enough light hammer falls often enough that someone like Mcarbo made a heavier spring for the same reason. It might feel lighter, but that is because it is longer, compressed to the same cocked length you can bet that it is giving more force than the standard spring. So you got to test both springs to the cocked length and see what force is needed. Then too, you could buy two 590 springs and use those like the 590 does. It will be interesting to see how you eventually decipher the problem and how you solve it. I suppose you could test the force it takes to cock the hammer, maybe cock it by placing the hammer on a scale and push on it until it cocks, then install the other spring and make the same measure. Or you could just shoot the gun and see if it works often enough to make you happy as is.

 

Just speculating here, thinking out loud. If 590 has dual springs, what does that tell you? The 590 is a more robust model 500, made more for military and police, the trigger housing is aluminum, not plastic for example. So why do they put two springs on the hammer in this more robust model? First guess off the top is they probably were trying to eliminate light hammer fall more positively. If they never had light hammer falls in the M500 they probably would have stuck with just one spring in the 590 also. Case in point, the original SX1 had dual hammer springs, why, I would bet they had light hammer falls in their prototype giving fail to fire so went to dual springs in the production model. That was the stage one trigger. Later they went with a heavier spring and just used one, that was the stage two trigger. But, light hammer falls is a pretty common SX1 problem, I experienced it on about 3 out of 6 that I owned. Also there are heavier aftermarket hammer springs available for it, and I put those in mine that I owned.

Therefore it would be very easy to believe the Mossberg trigger, has experienced enough light hammer falls often enough that someone like Mcarbo made a heavier spring for the same reason. It might feel lighter, but that is because it is longer, compressed to the same cocked length you can bet that it is giving more force than the standard spring. So you got to test both springs to the cocked length and see what force is needed. Then too, you could buy two 590 springs and use those like the 590 does. It will be interesting to see how you eventually decipher the problem and how you solve it. I suppose you could test the force it takes to cock the hammer, maybe cock it by placing the hammer on a scale and push on it until it cocks, then install the other spring and make the same measure. Or you could just shoot the gun and see if it works often enough to make you happy as is.

You echoed my thoughts exactly. Seems to make sense. My problem is I want 100% ignition. The thing is I can't find the 590a1 dual spring anywhere for sale, nor can I find a schematic for the a1, just the regular 590 which has the single spring.
Another thing I noticed while messing around with the gun last night is that the firing pin spring is SUPER strong. I couldn't even push it enough with my thumb to make it protrude from the bolt face. I read up on it a bit and evidently mossberg originally didn't use any firing pin spring, then they went to a spring setup, then on these later guns they went to a very heavy spring. I came across that a few times in forums. It's hard for me to believe the hammer has enough force to overcome that spring EVER.

 

My problem is I want 100% ignition. The thing is I can't find the 590a1 dual spring anywhere for sale, nor can I find a schematic for the a1, just the regular 590 which has the single spring.
Another thing I noticed while messing around with the gun last night is that the firing pin spring is SUPER strong. I couldn't even push it enough with my thumb to make it protrude from the bolt face.

You impress me as excellent at diagnosing with those thoughts. The SX1 also had problems with the firing pin spring being too strong, and maybe was partially responsible for the fairly common light hammer falls on that gun. The solution on SX1 is that most gunsmiths that specialize in the SX1 routinely cut 3/8 inch off the firing pin spring when installing a new one. You may have some sort of similar problem, spring too strong, maybe a burr or dirt on firing pin or its's channel. With your skill level, I think you will run it down shortly.

 

Another thing I noticed while messing around with the gun last night is that the firing pin spring is SUPER strong. I couldn't even push it enough with my thumb to make it protrude from the bolt face. I read up on it a bit and evidently mossberg originally didn't use any firing pin spring, then they went to a spring setup, then on these later guns they went to a very heavy spring. I came across that a few times in forums. It's hard for me to believe the hammer has enough force to overcome that spring EVER.

The likely reason you couldn't push it forward with your thumb is because the locking block in the bolt that engages the recess in the barrel tang was blocking the movement of the firing pin. It's designed that way for safety reasons so that the gun will not fire when the bolt is not locked securely into battery.

Assuming you have the bolt assembly out of the receiver, all you have to do is turn the bolt upside down and gravity will move the locking block out of the way. Then you will find that it's easy to push the firing pin forward with your thumb. My guess is that it takes only about 1 pound of force to overcome the firing pin return spring in the bolt. At least that's the way it is on all pump and semi-auto bolts that I've examined. Don't recall how much it was on my Mossberg 500.

 

Good thoughts, Uly.

 

Another thing I noticed while messing around with the gun last night is that the firing pin spring is SUPER strong. I couldn't even push it enough with my thumb to make it protrude from the bolt face. I read up on it a bit and evidently mossberg originally didn't use any firing pin spring, then they went to a spring setup, then on these later guns they went to a very heavy spring. I came across that a few times in forums. It's hard for me to believe the hammer has enough force to overcome that spring EVER.

The likely reason you couldn't push it forward with your thumb is because the locking block in the bolt that engages the recess in the barrel tang was blocking the movement of the firing pin. It's designed that way for safety reasons so that the gun will not fire when the bolt is not locked securely into battery.

Assuming you have the bolt assembly out of the receiver, all you have to do is turn the bolt upside down and gravity will move the locking block out of the way. Then you will find that it's easy to push the firing pin forward with your thumb. My guess is that it takes only about 1 pound of force to overcome the firing pin return spring in the bolt. At least that's the way it is on all pump and semi-auto bolts that I've examined. Don't recall how much it was on my Mossberg 500.

Well on my mossberg the tension from the firing pin spring actually holds that locking lug up into place when the bolt is out of the gun. It doesn't seem to matter what position that locking lug piece is in, the firing pin is extremely difficult to push in and it doesn't seem to protrude more than 1/16 of an inch from the bolt face. I'm kind of confused by that.

 

My problem is I want 100% ignition. The thing is I can't find the 590a1 dual spring anywhere for sale, nor can I find a schematic for the a1, just the regular 590 which has the single spring.
Another thing I noticed while messing around with the gun last night is that the firing pin spring is SUPER strong. I couldn't even push it enough with my thumb to make it protrude from the bolt face.

You impress me as excellent at diagnosing with those thoughts. The SX1 also had problems with the firing pin spring being too strong, and maybe was partially responsible for the fairly common light hammer falls on that gun. The solution on SX1 is that most gunsmiths that specialize in the SX1 routinely cut 3/8 inch off the firing pin spring when installing a new one. You may have some sort of similar problem, spring too strong, maybe a burr or dirt on firing pin or its's channel. With your skill level, I think you will run it down shortly.

Thanks for the kind words, it'd funny despite having quite a few interesting guns and much more expensive guns, the old Maverick 88 is still my favorite out of all of them. That's why I'm really committed to tracking down this problem.

 

Another thing I noticed while messing around with the gun last night is that the firing pin spring is SUPER strong. I couldn't even push it enough with my thumb to make it protrude from the bolt face. I read up on it a bit and evidently mossberg originally didn't use any firing pin spring, then they went to a spring setup, then on these later guns they went to a very heavy spring. I came across that a few times in forums. It's hard for me to believe the hammer has enough force to overcome that spring EVER.

The likely reason you couldn't push it forward with your thumb is because the locking block in the bolt that engages the recess in the barrel tang was blocking the movement of the firing pin. It's designed that way for safety reasons so that the gun will not fire when the bolt is not locked securely into battery.

Assuming you have the bolt assembly out of the receiver, all you have to do is turn the bolt upside down and gravity will move the locking block out of the way. Then you will find that it's easy to push the firing pin forward with your thumb. My guess is that it takes only about 1 pound of force to overcome the firing pin return spring in the bolt. At least that's the way it is on all pump and semi-auto bolts that I've examined. Don't recall how much it was on my Mossberg 500.

Well on my mossberg the tension from the firing pin spring actually holds that locking lug up into place when the bolt is out of the gun. It doesn't seem to matter what position that locking lug piece is in, the firing pin is extremely difficult to push in and it doesn't seem to protrude more than 1/16 of an inch from the bolt face. I'm kind of confused by that.

I thought that you couldn't push it in at all. Now you're saying you can push it in but it's difficult to do. Have you checked the spring itself? It may be broken or may have some debris in there.

 

The first time I said that I couldn't push it past the bolt face with my thumb. This time I tried by pushing on the back of the firing pin on a workbench and was able to get it to protrude but just barely. Still can't do it with only my thumb.

 

The first time I said that I couldn't push it past the bolt face with my thumb. This time I tried by pushing on the back of the firing pin on a workbench and was able to get it to protrude but just barely. Still can't do it with only my thumb.

I repeat... have you checked the spring itself to see if it's broken or if some foreign object is lodged in there? If you've got the bolt assembly out of the gun, it shouldn't take more than 5 to 10 seconds to do this.

Also I will repeat that the firing pin spring should not take more than about 1 pound of pressure to compress it. SOMETHING is stopping, blocking, or in some way impeding the movement of the spring. It's up to you to look at it and find out what this "something" is.

 

The first time I said that I couldn't push it past the bolt face with my thumb. This time I tried by pushing on the back of the firing pin on a workbench and was able to get it to protrude but just barely. Still can't do it with only my thumb.

I repeat... have you checked the spring itself to see if it's broken or if some foreign object is lodged in there? If you've got the bolt assembly out of the gun, it shouldn't take more than 5 to 10 seconds to do this.

Also I will repeat that the firing pin spring should not take more than about 1 pound of pressure to compress it. SOMETHING is stopping, blocking, or in some way impeding the movement of the spring. It's up to you to look at it and find out what this "something" is.

OK I looked at it again and it's definitely way more than 1 pound of pressure to compress the spring. Looks like I'll have to punch that pin out and take the firing pin out and see what's going on. I'll report back

 

The first time I said that I couldn't push it past the bolt face with my thumb. This time I tried by pushing on the back of the firing pin on a workbench and was able to get it to protrude but just barely. Still can't do it with only my thumb.

I repeat... have you checked the spring itself to see if it's broken or if some foreign object is lodged in there? If you've got the bolt assembly out of the gun, it shouldn't take more than 5 to 10 seconds to do this.

Also I will repeat that the firing pin spring should not take more than about 1 pound of pressure to compress it. SOMETHING is stopping, blocking, or in some way impeding the movement of the spring. It's up to you to look at it and find out what this "something" is.

So I disassembled the bolt and there is nothing that seems out of sorts. The spring is intact, washer is intact, and the channel the firing pin rides in is totally clear without any obstructions. With the spring removed, the firing pin moves freely and it's maximum protrusion from the bolt face is right around .073"
Is this a normal amount of protrusion?
However, you stated that the firing pin spring shouldn't take more than around 1 pound of pressure to compress it. I measured the entire length of travel of the firing pin which came out to .167"
Then I tried compressing the spring that distance and I'm NOWHERE NEAR able to do it with the spring placed in between the pad of my thumb and index finger. If I move the spring into position between my thumb and the first joint at the end of my index finger I can come close to closing it but I can still only get about .130" travel out of it with all the strength in my one hand. So basically I have to use two hands to close the spring enough to equal the amount that it needs to compress in order to allow the firing pin to protrude fully from the bolt face.
So I reassembled the bolt and used dumbells to see how much force it takes to compress the spring enough to allow the firing pin to protrude fully from the bolt face. It took right around 25 pounds of weight to do so. I also tested my grip strength using dumbells and a piece of cordage to see how much force I can exert between my thumb and index finger and I'm able to squeeze with around 20 pounds of force but 25 is just beyond my limit. Given these very unscientific tests I feel safe to say that this spring needs around 25 pounds (+/- 5 pounds) of force to compress the necessary distance. This figure is obviously drastically different than yours so I'd love to get your thoughts on this. Below are the measurements I took with a digital caliper that might be of interest.

Total firing pin travel- .167"
Firing pin protrusion from bolt face- .073"
Firing pin spring wire diameter- .0535"
Estimated force required to compress spring ~25 pounds

Regards,
Alex