Strain screw specs?

[robertrwalsh]

I have a 625-2. Recently I figured I would change out the obviously wrong strain screw and put in a Wolff reduced power leaf spring while I was at it. The reason I figured the strain screw was wrong is the head protruded significantly outside of the strap, to the point the Pachmayers had been relieved for it. I got a supposedly stock round-butt strain screw from Midway. The weapon is a round butt. I assume it came that way but since I bought it used I can not swear to it. The strain screw I took out had a relatively thick head and was 0.464 inches long overall. It is noticeably mushroomed on the tip. The stock strain screw is 0.418 inches long and has a relatively thin head. It does not fire reliably with the new screw and new spring. (Yes, I know, I should replace one piece at a time and then check.)

Does anybody have the specs for the correct screw handy? I can't find my bloody book. Thanks.

 

[RGPM1A]

I always replace my strain screws with 1/2" long 8-32 set screws. I put a small amount of blue Loctite on them before use and they will not loosen but are still adjustable to dial in the desired DA trigger pull for reliability

 

[series guy]

McMaster has a set screw with locking compound that is the ticket for power rib springs in round butt guns. Part number 95235A507. The rib causes the strain screw to be too short with the accompanying failure to fire. I have done at least 30 S&Ws with the power rib main spring, 13 or 14 pound rebound spring and this set screw. I set the S/A pullet 2.5lbs and the D/A pull at 8 lbs. If D/A ignition isn't 100% then I give the set screw 1/4 turn in.

 

[Jason Demond]

McMaster has a set screw with locking compound that is the ticket for power rib springs in round butt guns. The rib causes the strain screw to be too short with the accompanying failure to fire.

A light weight mainspring alone can be cause for light primer strikes.

 

[Borderboss]

Wolff sells an extended strain screw that you can grind down to the exact length you want. When I called them about it, the guy just sent me a couple, no charge. I used one on my 617 and it worked out perfectly.

 

[stang1911]

I have a 625-2. Recently I figured I would change out the obviously wrong strain screw and put in a Wolff reduced power leaf spring while I was at it. The reason I figured the strain screw was wrong is the head protruded significantly outside of the strap, to the point the Pachmayers had been relieved for it. I got a supposedly stock round-butt strain screw from Midway. The weapon is a round butt. I assume it came that way but since I bought it used I can not swear to it. The strain screw I took out had a relatively thick head and was 0.464 inches long overall. It is noticeably mushroomed on the tip. The stock strain screw is 0.418 inches long and has a relatively thin head. It does not fire reliably with the new screw and new spring. (Yes, I know, I should replace one piece at a time and then check.)

Does anybody have the specs for the correct screw handy? I can't find my bloody book. Thanks.

.505" OAL and .380" under the head

 

[steelslaver]

My method. Get a screw with the right head. Round butt screws have a thinner head. Screw it in until gun functions, then make some primed cases for it. Place them in gun one at a time and fire double action. If it don't fire tighten screw 1/2 turn. Once I have it so it fires 5 in a row, I take it to the range. I fire a box of ammo through it. Any misfire it gets another 1/2 turn and 50 more rounds. Then I turn the screw in tight counting the 1/4 turns it takes to get tight. Remove screw and measure length. It is a 32 to the inch screw so each turn is .03125 and every 1/4 turn is .0078. Take number of 1/4 needed to tighten times .0078. Subtract that from total length of screw. Make screw correct length or slightly longer leaving end slightly rounded. Install tight.

 

[robertrwalsh]

Thanks guy. Appreciate the numbers. Still can't find my book.

 

[fleabus101]

FYI to replace the screw w a strain screw
go to gungaragestore website and search
smith wesson screw for many types of screws
blue or stainless finish available..
These are mostly for post 1950 dimension Smith Screws..
I usually lay in a supply to allow for adjustment
if desired...