S&W 686 Misfires

[SC Tiger]

I took my S&W 686 to the range yesterday for the first time in probably 6 years. It shot very well until near the end (about round 40-45) where it had a misfire. The primer definitely had a smaller firing pin mark than the other rounds. I retried the round and it fired fine. This happened again around round #50. Ammo was Atlanta Arms and Ammunition reloads that the range sells. The gun has a spring kit in it so here are my questions:

1) Would this be more of a mainspring issue or a hard primer? I ask because the frequency is low (4%), though too high for a defensive weapon (this is more of a range gun).
2) Is there anything that can be done to correct this that would not involve changing the mainspring? I know that is the easiest solution but the DA pull is REALLY sweet so if something else could be done I'm open to it.

I know what I'm probably going to have to do but I'm wondering if there are other options. Does Atlanta Arms and Ammunition ammo tend to have hard primers? My Kahr didn't have any problems with their 9mm but it is bone-stock (and scarily accurate BTW).

[DefensiveCarry.com]

[wmhawth]

The first thing I would do is try some different ammunition.

[shooterX]

The first thing I would do is try some different ammunition.

+1 try didferent ammo, and see if it's still an issue.

[Rcher]

I agree with what others have said about different ammunition. It's not uncommon to get a bad reload no matter who's reloads they are. Personally, I shy away from reloads in a handgun.

[tflhndn]

Check to see if the mainspring tensioning screw has begun to back out. (front of handle near butt)
As it backs out, it lightens the spring power, and might be causing intermittant light strikes.

[Black Knight]

IIRC Atlanta Arms And Ammuntion is rather dirty for reloads. The gunk from the reloads may be accumulating in the 686 and causeing a problem every so often. Also the spring kit may not be the proper one. Also check the strain screw to make sure it is all the way in and seated properly.

[Streaker]

Check to see if the mainspring tensioning screw has begun to back out. (front of handle near butt)
As it backs out, it lightens the spring power, and might be causing intermittant light strikes.

Does this occur in single action, double action, or both.

I had the same issue occur with my M65. Tightened and then no problems.

[Pioneer]

You are taking a risk when shooting someone else's reloads.

[goawayfarm]

Check to see if the mainspring tensioning screw has begun to back out. (front of handle near butt)
As it backs out, it lightens the spring power, and might be causing intermittant light strikes.

Try this FIRST!...Slightly tighten the screw....On a S&W revolver, it is located at the bottom of the front strap. Sometimes it will loosen & cause 'light' strikes. If this fixes it, use some lock tight on the screw.

[Ram Rod]

Misfire in a revolver? Can't say I've heard of that before. I don't get out much either. Sounds like some of the members know what they are talking about, and I would tend to go with them on the adjustments over the ammo being the issue. Good luck on it.