View Full Version : Trigger boosting and pretravel
April 13, 2009, 09:52 PM
1. I have a bit a creep, it was always there, but lately, either I have become more sensitive to it (or like an idiot, rested the sear nose just past half cock and dropped the hammer roughing the edge of the sear). I'm going to do a disassembly and inspect hammer hooks and sear engagement surfaces for damage and polish up the disconnector. If all looks well, since I do not own a sear tool kit to stone the sear and make it nice nice, I was going to try boosting the trigger. I'll go easy - I was wondering if this really works, as I never heard of this before. Do you pull the trigger while pushing up on the hammer, or push, release, then fire?
2. Also, I took out all the pretravel I could without disabling my half cock safety notch. If I take out anymore, my half cock probably won't work. I believe I have .025" clearance before the trigger bow will contact the sear. I will measure again, but, still feels like a lot of pretravel compared to those Kimbers that have none. Is it possible that some guns just need a certain amount of pretravel while others don't? How do kimbers get away with no pretravel, is it the cut of the hammer hooks?
3. Lastly, the tabs on the trigger - when bending those for pretravel adjustment, if you don't bend one as far as the other, will this have any effect? I know we are adjusting both visually, but if they are not bent evenly, will that cause the trigger to have side to side play?
April 14, 2009, 11:46 AM
Boosting does work. It's generally advised to only boost the hammer a few times (e.g. less than 10). If it's going to have an affect, you'll notice by then.
You need pretravel to reset the sear. The number I've seen frequently is 0.06".
April 14, 2009, 01:54 PM
I assume this is a 1911 and that by "tabs", you mean the leaf spring fingers? The leaf spring can be used to adjust the ratio of the first stage take-up to the let off to some extent. However, if you lighten the fingers too much, you become vulnerable to hammer following and disconnector malfunction. The right leaf affects the grip safety, but over or under-tensioning it will be felt on the other fingers.
Removing too much travel in the first stage of the trigger by flexing the trigger bow also increases the gun's vulnerability to hammer following, and should not be tried with a steel trigger stirrup or a wide, Goldcup style trigger. They have too much mass for best safety doing that. Besides, the first stage take up lets you gage your trigger tension. Overtravel is much more disturbing to me.
Boosting can settle a sear engagement in, but it has the most effect when there are still machining marks or is grinding surface roughness on the hammer hooks and sear to be worn in to self-fit. The pressure from boosting causes them to wear against each other, flattening the areas of high contact and kissing the areas of lower contact, thereby tending to spread contact out more evenly. Uneven engagement promotes creep.
You should test for hammer following after messing with a trigger. Remove the magazine from the gun. Lock the slide back. Pinch your right thumb and index finger over the ends of the pin at the bottom rear of the grip frame that holds the mainspring housing in place. Hold the gun balanced upright by that index finger and thumb. The muzzle will be angled up. Use the thumb and index finger of your left hand to depress the slide release. The slide should slap into battery without the hammer falling out of full cock.
April 14, 2009, 03:17 PM
By the tabs, I mean the little tabs on the trigger bow to adjust for pretravel.
April 14, 2009, 05:44 PM
I must be getting old. I've never had one of those triggers in my hands. I still advise doing the hammer following test, though, whatever trigger you are using.
April 14, 2009, 07:17 PM
Just a warning, do not try to remove ALL of the takeup, it is necessary in a 1911 design. Unless you want to fire doubles and triples.
April 14, 2009, 07:54 PM
This is what he's referring to..
* the tabs, below the front end of the trigger bow, can be extended to take-up the play in the trigger.
April 19, 2009, 08:56 PM
I think I understand why you test at the half-cock notch log, but check me on this. The key lies in the fact that the sear feet are farther to the rear when the gun’s at half cock than they are when the gun’s at full cock. That means that if you have zero pre-travel at half-cock, you will have exactly enough pre-travel at full-cock, which will probably be somewhere from .040” to .060”.
If the trigger has pre-travel at half-cock, then that amount of pre-travel (what you have at half-cock, not full-cock) is excess and can be safely removed. To figure out how much to remove, cock the gun to half-cock, and with the trigger all the way out, scribe a pencil line on the trigger up against the frame. Then, depress the trigger to take out all the pre-travel at half-cock, and then scribe another line. The distance between the two lines is the amount of pre-travel that you can safely remove by cutting and bending tabs in the bow, etc.
I followed this method, figuring this out myself by using my eyeball and brain as I had the gun apart. When I measure my pretravel, it's somewhere around .035"
April 20, 2009, 04:58 PM
I've never heard of "boosting" a 1911 "trigger." Don't do it! If the trigger bow, disconnector, sear and hammer hooks are set right "boosting" misn't necessary! By "boosting" if it means putting pressure on the hammer and pulling the trigger to "weear in the job" then you shouldn't be fooling with your trigger - trigger jobs aren't done like that!
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