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Measuring Trigger Pulls
#1
Subject: Measuring Trigger Letoff

Posted By: ML - Registered User

Posts: 272

Posted At: (4/29/02 4:02 pm)

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Measuring Trigger Pulls



Some time ago, the subject of measuring the weight of a trigger’s release came up. Of course, the correct procedure is to use a dedicated trigger-pull gauge such as sold by Lyman or RCBS.



For those Forum members who are either too thrifty to spend the $50 or so for such a device, or who only plan to use it once or twice and put it away, there is a workable alternative.



First, make sure the firearm in question is unloaded. Then take an empty gallon milk jug, and tie a short loop of string through the jug’s handle and over the trigger--the string should run in one side of the triggerguard and out the other so it pulls straight down and not to one side, and it should be short enough that the jug is suspended only a couple of inches below the trigger itself. Next, cock the action, and make sure the safety is off. Finally, begin slowly filling the jug with water until the trigger releases.



At this point, you have two options: First, you may take the jug and water to a post office and weigh them together to get the exact weight of trigger release. Second, simply pour the water into a measuring cup at home, and calculate the weight.



How to do that? "A pint’s a pound the world around," my old man used to say. He’s largely correct, too: A gallon of water (eight pints or 128 fluid ounces) weighs 8.345 pounds (8 pounds, 5.5 ounces) Every ounce of water you decant weighs 0.0652 pounds (1.043 ounces by dry weight). Remember to factor in the weight of the milk jug. (No scale? Your old Uncle ML has just measured one for you, and it came in at 2.3 ounces empty. Your milk jug’s mileage may vary, blah blah blah.)



Our metric friends have things a little easier, as one ml (milliliter) of water weighs exactly 100 grams.



If your trigger pull is more than eight pounds (one gallon), measuring its letoff is the least of your problems.



And a little piece of informational lagniappe: a gallon of gasoline weighs 6.1 pounds, and a gallon of motor oil weights 7.5 pounds.



Have fun,



--ML



29.iv.2





Edited by: ML at: 4/29/02 6:35:26 pm



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Subject: Very cool and another question

Posted By: David R - Registered User

Posts: 109

Posted At: (4/30/02 11:59 am)

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So, i have just finished two books from STTU (hope i said that right :-) on marksmenship and tactical stuff. I am reading everything that I can get my hands on ...



my question is.. so a person finds out that the trigger has an 8lb pull. Now what? How do I get to a 3.5lb trigger pull? That seems to be the number that I have seen floating around. What is the right trigger weight?



Thanks,



David



P.S. Thanks to Bill Hay and ML earlier for your answers on why Glass Bedding. You guys have really been helping me a lot!



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Subject: Triggers

Posted By: ML - Registered User

Posts: 273

Posted At: (4/30/02 1:07 pm)

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There’s nothing "magic" or absolute about 3.5 pounds per se, although for many rifles it’s a worthy goal. When the trigger pull is greater than the weight of the rifle, life becomes more difficult, but many rifles weigh in excess of seven or eight pounds.



Some rifles--especially autoloaders--really need heavier trigger pulls. The M1 Garand, for example, is seldom safely reduced below 4.5 or 5 pounds, so this 3.5 goal is really for bolt guns and single shots.



No less an authority than the great Jeff Cooper has gone on record as saying that trigger-release weight alone is not the primary concern--a trigger’s crispness, lack of creep, and lack of overtravel is. From the Guru himself:



"The most essential element of the ‘shootability’ of rifle or pistol is its trigger action. The ideal trigger breaks clean without telling the shooter that it is about to do so. This quality is generally referred to as ‘crispness’ and does not refer to trigger weight. A two-stage trigger, which is what I prefer, moves slightly and smoothly before it reaches ignition pressure. With a single-stage action, the trigger does not move perceptibly without ignition pressure. In either case, there appears to be a consensus that 3.5 to 4 pounds pressure is the correct weight. Actually weight is a good deal less important than crispness. A trigger may be quite light, but still ‘mushy’ in the sense that it moves perceptibly when activated. Such movement is called creep, but it is not ‘take-up,’ which occurs before the trigger has reached the point of ignition pressure.



"Superior trigger action is more of a help to the shooter in snapshooting than in slow-fire, but a really good trigger is the first thing to look for in the selection of any rifle. When people ask what rifle they should bring to class here at school, my answer has always been, ‘bring the one with the best trigger.’"1



That noted, we come to the second part of your question: "What can I do about it?" Some rifles (notably Remington 700s) permit trigger adjustment simply by turning screws. On other non-adjustable designs, lightening the trigger and cleaning up its action is achieved by altering the trigger and sear surfaces with a sharpening stone, and through alterations to the trigger spring(s). This course typically requires some skill, and the results--good or bad--are generally irreversible without purchasing new parts. It’s tempting to take your stone work just a little too far and produce an unsafe trigger. In addition, some triggers/sears are case-hardened, and stoning through the thin case treatment exposes the soft metal, which wears quickly and returns a poor trigger with use.



Perhaps the best solution of all is the purchase of an aftermarket trigger. Thankfully, there are several really excellent designs around: Timney, Dayton, Kepplinger, Bold, and Shilen all produce outstanding aftermarket triggers for a variety of modern and vintage rifles. (God bless these folks for keeping the faith in such a litigious product-liability atmosphere!) Prices generally range from $40 to $100 or so. Often a little additional inletting is required, but not much more. The specifics, of course, vary from brand to brand and rifle to rifle.



Recently I installed a Timney trigger ($37.99 from Cabela’s--see link below) in one of my Swedish M96 Mausers. Excellent results--I didn’t even bother re-adjusting the unit from the Timney factory specifications. I did have to relieve some metal in the triggerguard and some wood in the stock--maybe an hour’s fine work with a die grinder and a file. Of course, a good gunsmith could do this for you as well.



(Cabela’s Link)



[url="http://www.cabelas.com/cabelas/en/templates/pod/standard-pod-wrapped.jhtml?id=0012728&navAction=jump"]http://www.cabelas.com/cabelas/en/template...&navAction=jump[/url]



Hope that helps!



Good shooting,



--ML



1 Jeff Cooper’s Commentaries, Volume Nine, Number 14; December, 2001.



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