625-8 heavy primer strikes

[GCF]

I hear a lot about light primer strikes (especially w/ reduced power springs), but I've got a situation that's a bit different.

My plain vanilla 625-8 has always seemed to hit the primers a little harder then necessary. Never had one actually pierced, but I wouldn't mind lightening up on them - just a little.

Cylinder gap & head space are both minimal. No noticable end shake. I use WW, & Federal LP primers. WW & RP brass.

Installed a Brownells reduced power spring kit, & although the action is now lighter & smoother then ever (wasn't bad before), the lighter main spring didn't seem to reduce the primer strike appreciably.

With or w/ out moon clips, primers are about the same - & operation is 100%.

I've heard that frame mounted firing pins, have had some variation in length over the years, w/ the biggest related problem being a pin that was too short.

Have not pulled my pin for a measurement yet, but was thinking about it. I'm the second owner, & don't think the pin has been replaced.

Wondering if any one else has run into this, & if so, what was the resolution? Any comments would be appreciated...

 

[scooter123]

What leads you to think you're having heavy primer strikes?

BTW, I've been there and seen the effects, however in my case it was due installing a Cylinder & Slide firing pin in a 610-3 and leaving the mainspring at full factory power. After shooting 100 rounds with it I went home and started unloading the moon clips and putting the fired casings primer up in the plastic trays that came in the ammo box. A full 30% of those casings showed darkened primers. Further examination using a 10 power magnifier showed that there were microscopic cracks in the firing pin dimples. Cracks and darkened primers meant there was some gas leakage and it was likely borderline for a pierced primer, so I immediately re-installed the factory firing pin when I got home and that problem went away.

However, a bit later I tuned the 610 to a lighter DA trigger and have since re-installed that C&S firing pin. Currently the DA trigger pull is 8 lbs. 5 ounces and I have not seen one single darkened primer. Conclusion, it's suitable and safe for use with a lightened trigger but not a good idea with the mainspring at full power.

Now to my original question. I would suggest that you do as I did and line up your fired casings in a tray. If every single casing shows a nice clean primer, I really wouldn't worry about those "hard" strikes. However, if you see some darkened primers I suspect that the first owner has installed a C&S firing pin. The answer for this is to reduce your DA trigger to between 8 and 9 lbs. or order up a factory firing pin and install that. BTW, the factory firing pin in my new 625 JM measure at 0.488 inch in length when I pulled it. The factory pins in my older 620 and the 610 measured at 0.478 and 0.481 inch, so I would conclude the factory has lengthened the firing pins by about 0.010 inch in the past 2 years.

BTW, concerning the C&S firing pin. Overall length should be between 0.500 and 0.510 inch, my first 2 came in at 0.500 inch and the last two were 0.510 inch. In addition the travel slot in this firing pin is about 0.045 inch longer than the factory firing pin. This means that the C&S firing pin can project much further through the recoil shield than the factory firing pin. Because of this extended travel feature it is a MUST that you ALWAYS use snap caps, otherwise you can wad up the firing pin return spring.

If you have 2 S&W revolvers with frame mounted firing pins you can test for the C&S firing pin very easily. Open the cylinder, pull the release to the rear, then cock the hammer. Then take a ballpoint pen and push the firing pin forward. With the C&S firing pin you'll see that it can project out of the recoil shield by the thickness of a penny. With the factory firing pin it won't project by the thickness of a dime.

BTW, my 625 JM (a -8) has a 0.510 inch C&S firing pin with the DA trigger set to 8 lbs. I have not seen one single dark primer and I have looked for them. I've also tested for ignition reliability with Speer Lawman WITHOUT moon clips and ignition is 100% perfect. I believe this is due to that extended travel feature because unclipped casings sit 0.018 inch deeper in the cylinder. One plus is I don't have to rely on moon clips, last time at the range I only had 16 clips loaded up and didn't want to stop, so I shot 50 without clips.

 

[GCF]

What leads you to think you're having heavy primer strikes?

Well Sir, you appear to have hit the proverbial nail (firing pin?) on the head - w/ your assessment. Your input is greatly appreciated.

To answer your question, fired primers have a noticably deeper / wider indentation. It is obvious at first glance, that they are being hammered excessively. No gas leakage as described, but I could see it happening (easily) w/ a shallow primer pocket.

Checked last night, & the pin protrudes through the bushing a bit further then the width of a penny.

Pulled the pin this morning, & took a few measurements:
OAL 0.5065" / Striker Only 0.216" / Travel Slot 0.131"

The return spring appears to be OK, & the pin does not hang or stick.

Can't say for sure that it's an aftermarket kit, but at this point it sure looks like it - regardless of the original owner's statement. I wonder if S&W might have used C&S pins at one point? Also wondering how long the travel slots on your factory pins are?

It is interesting that although I'm using a Wolff RP (Type 2) MS, I'm still getting grief from the longer pin, where as your problems went away - w/ the RP MS. Each gun an entity unto itself, I suppose...

Apex offers a "Comp" FP, that is spec'ed at 0.495" OAL, which from what I'm seeing, is about the longest pin I would want to order - at this point. I'm thinking that length would still allow me to shoot "clipless" if desired. Be iteresting to see what a factory 0.490" +/- pin would do, but I'm not sure I want to order both.


Apex XP 0.500"
https://apextactical.com/store/product-info.php?pid4.html

Apex Comp 0.495"
https://apextactical.com/store/product-info.php?pid2.html

C&S XL
S&W Extra Length Firing Pin for New Style J - K - L -N Revolvers

 

[scooter123]

Since a picture is worth 1000 words I've attached a PDF file of a drawing of the measurements of the firing pin that came in my 625 and a spare C&S firing pin purchased at the same time as what is now in the 625. BTW, since I don't have an optical comparitor at home, the measurements of the travel notches may be off by as much as 0.005 inch, however I think it does illustrate the differences in features. Note the big difference in the slot for the retaining pin. It's why the packaging expressly states that snap caps MUST be used for any dry firing.

Personally, if you aren't seeing any primer leakage and the dimples aren't showing cracks, I'd be inclined to leave it in place and check the weight of the DA trigger. I've found that 8 lbs. is both reliable and easy to shoot with and I'm not the least bit concerned with the dimples I'm seeing in my fired casings. In fact the dimples look nearly the same as what I see with my 40 caliber Sig Sauers.

BTW, I just happened to compare some of the 40 caliber casings from my 610 to those from the 625 and the 610 shows a distinctly deeper dimple, which is likely a result of the trigger pull running at 9 lbs. due to interference with the grip screw on the Pachmayr Decelerators with the mainspring. When I purchased the 625 I ordered 2 of the 500 Magnum monogrips and the second is now mounted on the 610 and the trigger is now down to 8.5 lbs. However, I've probably run at least 1000 rounds downrange with the 610 with that 9 lbs. trigger and never saw any issues with primers cracking or leaking once I dropped the weight down from 10.5 lbs.

Since the the 40 caliber operates at a lot higher pressure than the 45 ACP in theory it should provide a "tell" a bit more evidently than the 45 ACP. The 40 might also be a bit more prone to a pierced primer due to the higher pressure and the use of a smaller diameter primer, however that is just speculation. I don't think you really need to be concerned, however if you have an old 24 or 28mm SLR lens laying idle that do make for a superb 10X magnifier by looking though the front, so you may want to take a close look at the primer dimples just to make sure they aren't cracking. If you don't see any cracks, don't fix what aint broken.

 

[GCF]

Since a picture is worth 1000 words I've attached a PDF file of a drawing of the measurements of the firing pin that came in my 625 and a spare C&S firing pin purchased at the same time as what is now in the 625. BTW, since I don't have an optical comparitor at home, the measurements of the travel notches may be off by as much as 0.005 inch, however I think it does illustrate the differences in features. Note the big difference in the slot for the retaining pin. It's why the packaging expressly states that snap caps MUST be used for any dry firing.

Thanks for the pics, & additional input. Went back & re-examined a bunch of my unprocessed brass from this gun, & actually did find a few pieces that appeared to have a bit of primer gas leakage. As such, I don't think that I'm spinning my wheels needlessly here.

The 0.131" measurement for the travel slot on my FP, was taken at the bottom of the slot. I note that yours was taken at the top.

The slot on your C&S is clearly positioned much farther the to rear, then the slot on my pin. Although I did not take fore & aft (of the slot) measurements, mine appears more like the factory piece - except that the front of the slot is cut at 90 degrees, & only the rear at 45 degrees.

Hard to say for sure - as I'm neither an engineer or a draftsman, but it's looking like both the position & length of the travel slot, may be more critical than the OAL of the pin, or the length of the striker portion itself.

In fact, even though the Apex Comp pin shows a 0.005" shorter OAL then their XP unit, I'm wondering if the Comp might not actually extend out further... Also wondering if a verified factory pin might not be a good baseline / starting point.

I think a couple of phone calls before ordering anything, might be in order.

Also went back & checked re-checked headspace:
RP, Clipped: 0.008"
RP, Unclipped: 0.014"
WW, Clipped: 0.009"
WW, Unclipped: 0.015"

Not sure how this stacks up to other rimless cartridge S&W revolvers, but it occurs that headspace could also be a light strike / heavy strike factor. I will say that I have fired a lot of rounds unclipped, w/ zero FTF malfunctions.

Based on the "penny check" (0.060" beyond FP bushing), it wouldn't hurt to lose 0.010" FP extension.

 

[tomcatt51]

Also went back & checked re-checked headspace:
RP, Clipped: 0.008"
RP, Unclipped: 0.014"
WW, Clipped: 0.009"
WW, Unclipped: 0.015"

Check the headspace with a piece of new brass. Moonclipped and loose. You'll see a different story. 625-8 chambers run undersize and out of round and routinely get reamed (to spec) because of this. Many rounds actually headspace because the case DIAMETER "wedges" in the chamber.

Apex Tactical firing pins aren't longer because they don't need to be longer unless you want to fire loose, not moon clipped rds. A "too long" firing pin just wastes hammer energy by not allowing the hammer to use it's full arc.

The appearance of the firing pin hit is very misleading. A lot of things happen when the round ignites. The case is pushed forward by the firing pin hitting the primer, the primer is pushed back upon ignition, the case is pushed backed reseating the primer, the primer is hit again by the hammer bouncing after it's initial hit.

 

[Flork]

I'm traveling so please forgive me if this has been covered, I haven't had ther opportunity to read through the entire thread.

Heavy strikes really aren't an issue, it's light strikes to worry about. Now a strike too deep in too small an area is an issue because it will leak gas back at you as you mentioned. That's why we specify our competition firing pins not be used for a trigger pull over 6 lbs I standard size frames.

One factor of what makes a strike look deeper is case jump. All cases jump when fired, the head stamp jams against the breech face and squashes the brass just slightly. Because the hammer is down and applying mainspring force on the firing pin, the firing pin is sticking out when this happens this means the firing pin is making a deeper than otherwise would be crater in the primer. Again, this is perfectly normal and not a problem.

Feel free to call the shop and talk to Randy about it, he can gives you the low down on it.

Scott @ Apex