I'm using an Arsenal Line partially completed frame and one of PvtRyan's 1911 parts kits. I used the Marvel sear jig to stone the primary and relief angles on my sear. I also filed down the hammer hook to .020" and polished the disconnector in the areas described on Brownells "GunTech" web site.
The problem I'm finding is that the first part of the trigger travel also moves the hammer *back* towards the cocked position before falling. This slight movement adds a lot to the trigger pull since it's pushing against the mainspring. The only thing that I might have missed is the "slight 45-degree bevel" on the hammer notch that is mentioned in the Marvel instructions. In any case, I'm almost sure it has something to do with my hammer/sear engagement but I'm not sure what is causing this problem. Any suggestions?
Yep you have the dreaded anglerongonsear syndrome.
Your sear primary angle has everything to do with this dreaded problem. First thing I do is take a Brownells hammer squaring file and ensure the hammer hooks are 90degrees. Thats a good start next I use a Wilson or Brown sear jig as it allows me to adjust the primary angle with a set screw. Once adjusted to my liking I have never had to move it but once.
Having the angle wrong in one direction allows the sear to cam the hammer to the rear when pulling trigger, going in the other direction allows a easier rolling trigger. Most shoot for a neutral angle, which took me awhile to find with my sear jigs, but with the outside the frame pins from brownells and a optivisor and trial and error I finally found it.
PS You also need to get the pins if you do not have them to ensure your sear is not only engaging one hammer hook.
Don't bother with another jig. What matters is how the sear and hammer engage on YOUR frame. Many frames, especially 80% frames, the pin holes are NOT straight (much less properly postioned in the frame) Remove the right sight stock panel, install your own pins, and see how the sear and hammer engage on YOUR frame.
The adjusting screw for the sear angles did come pre-set from Marvel to duplicate the original angle on a factory sear. This angle can be adjusted, but they do NOT recommend changing this angle so I've left it "as is." I have a sear block and pins that I used to observe the hammer/sear engagement. Here is a picture I took using an 8x loupe:
As you suspected, I did not dress the 90-degree angle of the hammer notch, and looking closely at this picture seems to show a positive angle where it should be square. I don't have a hammer squaring file but I do have a couple different sized Swiss files which should do the same thing. I'm also going to measure the height of my sear just to rule out any other problems.
What I like about the brownells hammer squaring file is it has two safe sides which allows you to square the hammer hooks without marring the surface that is guiding the file. If you have some needle files maybe you can make two sides safe yourself with a diamond file or carefully with a sanding machine. Dont be afraid to mess with your fixture, just remember how much you turned in on the fixture, IE 1/4 turn in etc. and lots of trial and error.
Just like the Brownells hammer squaring file, the Swiss file has two "safe" edges. I'll keep the safe side against the flats and the cutting edge against the hooks. I have some AL stock that I squared up to help keep the file perpendicular to the flats. I think this setup should work fine.
No two smiffs do things the same.
I'd like to offer an alternative method.
I'd first start with a known geometry quality hammer.
Wilson's 337 is excellent and comes pre-cut to .021" hook height.
Start prepping the hammer with a brown ceramic stone. Lay the stone on a block approx. 1" tall on your bench. Hold the stone in place with your left hand, and move the hammer with your right. Approx. 3" strokes, being careful to maintain a square cut.
It's a 'feel' thing. You can certainly feel a nice, square drag along the corner of the stone. 20 strokes should be sufficient to remove any radius in the corner of the hooks, and to polish the faces mirror bright. Of course you can then give it more with a white ceramic.
Now using a fine india or a brown ceramic, cut a radius on the top of those hooks. Be careful, use both magnification and feel to insure an equal radius on both.
The radius should be big enough to see. Maybe involving
.003" or 15% of the hook height.
Then set your jig to duplicate the angle of a recent Colt MIM sear. I ink the sear angle and adjust until the ink removes in a stroke or two.
You will now have what I find to be the correct geometry for a 3-5lb.crisp pull.
The breakaway angle on the sear will determine ultimate crispness and the sear spring will determine pull weight.
I like about 30% of pull weight from pre-travel sear spring loading.
A 60oz trigger will have 20oz of pre-travel load.
Once you succeed with known geometries, you can experiment with parts from other companies.
Modern Colt hammers have essentially the same geometry as the Wilson 337. Differences are hook height and strut hole location.
The sear angle used is the same.
Always test for hammer follow and only load a couple of rds. until the job is 'proven'.
If your needle file has two safe sides I think it should work fine. What I try to do is ensure the hammer hooks is a crisp 90 to the floor. You will notice the hammer hook many times is very rough, if you only take a stroke or two you will see you need to take several more strokes before all finish has been removed and many times it is not 90 degrees.
Thanks for adding another perspective to this delicate procedure!
I have both a fine India stone and Arkansas (white) polishing stone, but hesitated to use these in consideration that I might be removing material from both the flats as well as the hook. I suppose I could apply more pressure along the horizontal axis and use the flats as a guide to keep everything square.
I'll have to borrow a 1911 or buy a Colt MIM sear if I'm going to set my jig to the correct angle geometry. Either way, that's a great method for calibrating the angles. I'll start on the hammer notch and see how it feels first.
I'd suggest holding off until you get the ceramic stones from brownells.
Those other stones are infrequently truly square.
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I'd suggest holding off until you get the ceramic stones from brownells.
Those other stones are infrequently truly square.
Opps... too late! :D Fortunately, I was using a brand new Arkansas stone with real sharp edges AND IT WORKED GREAT!
No more hammer movement and it really breaks cleanly now. There is still some creep in the take-up, though...
Most of the time I find creep its because of the sear favoring one hammer hook over the other. While you can remove all oil from the sear and hammer and dry fire a bunch of times to see, I find it easier to use the outside the frame pins brownells sells. I start on one side of the frame and hit the hammer hook that looks shy with black marker and then try the other side of the frame. Most of the time it is appearant on both sides of the frame so out comes the hammer squaring file to remove a few thou from the offendingly proud hook. Next file both hooks to ensure they are in line with each other and check again with the pins. When they look right hit them with the Ceramic stones from Brownells, Walla hopefully the creep is gone now.
PS don't use your sear or hammer pins to try this as they are way to short to go through component and both sides of the frame, only going through one side of the frame is not telling you anything as that pin will wobble so much the parts will be capable of lining up on each other which is not helpling you at all.