625-8 Strain Screw Question

[Church Key]

I picked up a mint 625-8 for use in IDPA; currently use a Ruger Match Champion and decided to go to moon clips. The trigger pull on the 625 was really poor compared to the Ruger, so got a Jerry M. mainspring and trigger return spring. Installed them and then set the DA pull to 7-12 lbs., Jerry said to set to seven. Now comes my idiot part as I followed instructions and filed down the Strain Screw so it fit snug at 7-1/2 lbs., before testing the setup. I reload and am using the recommended Federal primers. One bang and five clicks later realize I've got a big problem.

Ordered a couple of strain screws from Brownells for an N frame round butt. They came today and the thickness of the new screw heads are about 1/2 the original screw thickness. Anyhow installed a new screw and it fit OK and gave me a 8+ lb. pull (my Lyman gauge only goes up to 8). I'll check everything out with some live fire testing. Anyhow, wondering if anyone knows if S&W changed the screw head dimensions.

Church Key

 

[andyo5]

Keep the JM strain screw. Get your set of auto feeler gauges, and cut a small (1/8" square) section out of the 0.005" feeler gauge. Unscrew the strain screw a little, and slip the piece of feeler gauge under the tip of the strain screw. Tighten the strain screw. You have now effectively 'lengthened' the strain screw by 0.005". Try it. If insufficient, try a thicker piece of feeler gauge until good.

 

[BLUEDOT37]

They made them with two different head thickness. I believe it was because of the grip frame's thickness. Maybe someone can add more.

Smith & Wesson Strain Screw S&W 64 65 66 242 296 386 - MPN: 072280000

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Smith & Wesson Strain Screw S&W 625 627 629 686 Round - MPN: 210300000

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[scooter123]

This is why I do my tuning with hand made shims that fit under the head of the screw. This allows me to tune the trigger to a specific weight. BTW per my Lyman Digital trigger gage that is 9.0 lbs and I don't find that the least bit heavy. However I am used to shooting a Dan Wesson model 15-2 with it's 13.5 lbs. DA trigger pull, really does an excellent job of "pumping me up".

Note, I have found that 9 lbs. is what is needed to insure 100% reliability with Remington UMC ammunition and I like to use Remington cases for reloading. The reason for that is because the flash holes in Remington cases are consistent and large enough at 0.082 inch to insure I don't get jammed pins with my stainless steel cleaning media. Federal cases are all over the place going from 0.075 up to 0.082 and jammed pins can be a bit of a big deal, because they can cause a primer to light off during seating, something that will really make your ears ring and scare the dog into hiding for 3 hours.

 

[Church Key]

andyo5 - Excellent suggestion; I'll stop by harbor Freight and pick up a set of feeler gauges for potential future use.

BLUEDOT37 - I got the 781378 (thin head) from Midway. It works fine, except the original one in the gun appears to be the 515288 (thick head). The shanks on both appear to be the same length. I will call S&W to see what they say.

Church Key

 

[Church Key]

OK, heard back from S&W. Seems the original 625 screw # has been changed to 41574000 from 07228000 (the # listed by Midway) and is now used for both the new style 64 and model 625. The correct screw is the thick-headed one. I probably will spend $1.99 + shipping and get the correct screw.

Church Key