T-C Trigger Job...again

[gregg]

Hello All,
My first post and I'm happy to say, that after spending a few hours on this web site, I think I have a pretty good understanding of what needs to be done on my trigger.  First off, I just purchased a used, very good condition, T-C Pennsylvania Hunter (1:66), with single trigger, that I want to use for offhand matches at my local area shooting clubs.  For these matches, I just fit a Parker-Hale globe on the front and P-H tang sight, with adjustable windage on the rear.  I very much like the way this rifle feels but the trigger has a consistent, fairly crisp, 8# pull that must be reduced, ideally to 12 ~ 18 ounces.  My local B.P. Gun Shop has the parts, but advised that fitting a Renegade DST (T-C or aftermarket) & Renegade trigger guard that it would not be a drop-in affair; and that portions of the original trigger guard stock inletting would need to be filled and that the LOP would be longer than I prefer.
After having spent quality time on this site, I believe that the best course of action would be to drill and tap the tumbler for a #4x40 set screw to limit sear travel/engagement. My question is whether the tumbler is heat treated and if folks have had success in tapping this part.  I do have a small mill in which I plan on using for this operation. 
One other option that I found here (and thought intriguing) is where someone had mentioned another method of limiting sear travel.  This method was used on an original long rifle and can be seen in the Virtual Museum>Rifles>Unknown Maker>Brass> JW-1008221-1.  The picture shows the inside side surface of the lock where a screw with a cone tip engages the underside of the sear, limiting sear rotation around it's pivot and thus full engagement with tumbler.  The beauty in this scheme lies in it's simplicity and the fact that I won't have to worry about breaking a small diameter tap in a hardened part (?) where the threaded hole in the tumbler will need to be 0.5" deep.  With this other method, I'll also be able to adjust sear engagement w/o having to take the lock off.  I'm thinking a #8x40 screw might be appropriate.
At any rate, I'd love to hear from anyone who has performed this operation, has any suggestions OR can let me know if the tumbler heat treated.
I did go to my local True Value Hardware store and found a sear spring made from .014" diameter wire instead of the OEM .023" diameter which, if it works, may help a bit.  If anyone is interested, it is Century Spring Corp. #C-570.
Thanks to all that waded thru all of the above, to all those that responded to a similar post a while ago.  Also, thanks in advance to those available to help with my dilemma.
gregg

[D. Taylor Sapergia]

Gregg:  first, welcome to this site.  There is a wealth of information here from a vast assortment of some builders and shooters who have been there and done that.
I saw the lock plate adjustment screw fix on an original lock once upon a time, and thought how clever that was.  So when I built my Hawken pistol, using a Pete Allen lock, I added the tapered screw through the plate.  I used a 6 x 48 tpi scope mounting screw from Brownell's.  They are hardened and the finer threads give more precise adjustment.  Your lock should have a fly or detent in the tumbler for best results here, if you are going to shoot for ~ one pound break.  Once the screw is installed in the lock plate, further adjustment can be achieved by cutting a tapered concave in the contact point on the bottom of the screw arm.
Once you have achieved the trigger weight you seek, cut the screw off on the outside so it is almost flush with the plate, and cut a fine screw driver slot in it.  Add a little LocTight to set the screw so it doesn't back out or worse, wind it's way in making your lock unsafe.
Good luck.
Oh, by the way, you would have to completely anneal the tumbler to drill and tap for an adjustment screw in the tumbler, and then re-harden and temper to the correct point...It's do-able but not necessary.

[gregg]

Hi Taylor,
I got the trigger pull on the Pennsylvania Hunter down to 18 ounces  by attaching a shim/block to the underside of the tumbler, to limit shear engagement.  I cut a wedge, filed it to shape, bonded it to the tumbler with Devcon metal filled epoxy and then stoned the contact surface until I got it up to 1 pound.  I also replaced the sear spring with the hardware store spring mentioned in my first post.  With the lock assembled, I estimated shear engagement was about .025" at full cock.  Upon assembly, I found the rifle to be somewhat sensitive to sudden impact.  I then stoned the block until where it is now.  First off-hand match was last weekend and the rifle performed very well.
As such, I decided to do something similar on a T-C Grey Hawk as this rifle has the same lock as the Penna Hunter.  This time I cleaned and greased the lock and just installed the lighter sear spring.  Trigger pull was reduced from just over 5 pounds to an even 3, which really surprised me.  If anyone has a single trigger T-C New Englander or Renegade with an overly heavy trigger pull, the replacement of the sear spring could reduce the effort by a pound or two.   Happy New Year to All!!
gregg