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Old July 9, 2013, 10:13 PM   #1
dyl
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Technical question: over-travel

It seems like the current belief is that over travel stops improve accuracy - or that at least over-travel is a detriment to accuracy.

But is this really true? Wouldn't stopping a moving trigger and trigger finger cause a disturbance in sight alignment? The assumption of an over-travel stop is that the trigger and trigger finger will hit the stop so the barrel will stop swinging horizontally BEFORE the bullet exits. Less swing, the less your sights are off target. The trigger would have to stop before the bullet left the barrel. Does the sequence of events that occur in the firing of a round allow this assumption to work?

Bottom line question: do over travel stops truly aid accuracy when firing live rounds or are they something we appreciate more when we dry fire and see the sights move less?

I believe a trigger with a lot of over travel could be accurate: if the trigger is still moving rearward in the same place every time as the bullet exits the barrel
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Old July 10, 2013, 11:38 AM   #2
Bob Wright
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Uh, your'e not stopping a trigger that has swung through a great arc. The target trigger moves almost an inperceptable amount, which is the ideal case.

For a good example, consider electronic triggers on some free pistols, where there is no "break" between the hammer and sear.

In the case of the older Ruger Single Actions, a fairly strong trigger spring arrests further rearward movement of the trigger.

It's much like a rifle with set triggers.


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Old July 10, 2013, 12:01 PM   #3
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Over-travel stops don't have anything to do with stopping the barrel from "swinging". They keep the excess movement of the trigger finger from disturbing the aim and causing the barrel to move out of sight alignment.

They are not really necessary; a shooter familiar with his gun will be able to handle over-travel with no problem, but like many other aids to shooting accurately, they do help.

Jim
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Old July 10, 2013, 03:39 PM   #4
dyl
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I was in a hurry when posting the question: I do understand that barrels and sights do not swing by themselves but are often pushed off target laterally as we depress the trigger because the path of our trigger finger is in an arc - less so if we train for that particular trigger.

Perhaps this illustration will more clearly present my question.

Let's say we have a hypothetical pistol that has trigger over-travel of an immense 2 inches. Next to it we have another of the same type of gun that has an over-travel of 1 inch. Many would say the second gun has the better trigger. But if in live fire the bullet exits the barrel of both guns while the trigger has only travelled half an inch beyond the break point, has the over travel stop actually helped? Maybe not.

Does anyone know what the sequence of events are regarding the bullet exiting the barrel and trigger travel?

Am I missing something here? I just wonder if over travel stops are more for the shooter's perception than anything that actually help down range.

I understand that target triggers, set triggers, and single action triggers can be set up to have very little creep/travel. I can easily understand how those aid shooter accuracy. I'm wondering about over-travel.
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Old July 10, 2013, 04:12 PM   #5
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IMO, overtravel can be an issue when the trigger's got excessive let-off. Let-off is the transition in pull weight when the sear breaks. A let-off that's really abrupt and harsh can itself affect accuracy, but it exacerbates overtravel, because with little resistance, your trigger finger is suddenly pulling through the overtravel abruptly.

Limiting overtravel can help mask a harsh let-off. Overtravel can be adjusted in SA triggers, but it's tough to do on DA triggers on DA/SA guns, since the trigger has to travel further in SA. Some revolver shooters who shoot DAO revolvers report that trigger stops can hurt accuracy when shooting DA quickly because the back of the trigger slams into the stop just as the shot breaks. The best solution here is to skip the trigger stop, and tune the DA trigger so it's smooth and consistent, and doesn't stack just before the sear breaks. You still have some overtravel, but it's no biggie because the let-off is smooth.
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Old July 10, 2013, 06:21 PM   #6
dyl
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So that's what let-off is. I currently have both a Glock and an M&P pistol and I am beginning to think all striker fired designs have a good bit of let off to them.
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Old July 10, 2013, 08:24 PM   #7
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I don't think the over-travel affects the CURRENT bullet being fired. A 1000 FPS bullet is already a foot away from the breech in 1/1000 of a second. If you had a 6" barrel, that would mean that the bullet exits the muzzle in 1/2000 of a second. I doubt that your finger does anything after the trigger break within 1/2000 of a second that would disturb the current bullet in flight.

It certainly might disturb the ability to follow up on the next shot if that finger movement was excessive and caused you to move off target more than a finger that stopped a very short distance behind the break point.


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Old July 10, 2013, 08:43 PM   #8
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That would assume that the letoff occurs at the same instant as the primer ignites. But it does not. Sear release or letoff occurs first, after which the hammer falls, after which the firing pin crushes the primer, after which the primer ignites, after which the primer ignites the powder, after which the powder burns, after which the bullet is pushed out of the case. Only after the bullet is almost all the way down the barrel does it achieve the muzzle velocity of the 1000 fps in your illustration.

The critical area for trigger letoff and overtravel is the period between letoff and primer ignition, and it is in that period that the gun can easily move off target due to overtravel, vibration from a heavy hammer fall, or simple movement of the shooting hand.

All those things wouldn't matter, or could be adjusted for, IF they were exactly the same each time. But in areas where the human anatomy is involved, things are not going to be exactly the same each time, and that is where accuracy is affected.

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Old July 10, 2013, 09:03 PM   #9
kraigwy
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Lets forget about trigger travel, trigger stop, etc.

What is critical in any shooting be it shotgun, rifle, or pistol is follow through.

With triggers we know after the trigger releases the sear, it has to be re-set prior to being able to fire the next shot.

Follow through hear means pulling the trigger, and holding it, don't allow the trigger to reset until you are totally recovered from the recoil and the sights are lined back on the target. Even if you are only firing one shot.

Don't properly it will eliminate any disturbance after you pull the trigger.
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Old July 11, 2013, 10:42 AM   #10
saleen322
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Trigger Stop

The idea behind them is it reduces barrel movement in the time before the bullet clears the barrel. Take a 1911 with a 4 lb trigger. You steadily apply pressure until it reaches 4 lbs, the sear releases, and then the trigger weight drops below 1 lb meaning now the trigger goes rearward abruptly gaining momentum the further it travels until it hits the stop. During all of that movement kinetic energy increases until it hits the stop and jars the gun. By reducing the amount of post release movement, you reduce the amount of disturbance to the pistol. This is why target pistols have trigger stops.
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Old July 12, 2013, 12:51 PM   #11
RickB
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If a gun has a somewhat slow lock time, and short trigger travel, I could imagine a trigger's abrupt stop could disturb the aim just as the gun fires. I've always liked the idea of the trigger remaining in a smooth rearward movement as the gun is firing, for that reason.
I've adjusted both pretravel and overtravel to differing degrees, and find they really only make much difference in dry-fire when I'm concentrating on almost nothing but the feel of the trigger.
The trigger overtravel screw in one of my guns was unscrewing itself as I shot, and until the gun started to malfunction as a result, I didn't notice that it had become un-adjusted from its original setting.
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Old July 23, 2013, 06:03 AM   #12
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Quote:
This is why target pistols have trigger stops.
Target pistols as in Olympic handgun competitons...where every advantage that is legal is used and nothing that is not an advantage would be added.

In the early eighties, some gun rag printed a "How-to", article on how to put a trigger stop in Ruger .22 pistols. I did both mine and my brother's. The control it gave, the difference was obvious. If I had a Ruger .22 auto today, I would make that modification again without hesitation. I like very light triggers and the trigger stop made them feel like the triggers were a couple of pounds lighter and made the Ruger's feel like they had a high-quality target trigger installed...not just when dry-firing, but when actually shooting them.
Trigger stops may not have a logical mechanical reason for increasing accuracy of shooting, but pragmatically they are an advantage.
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Last edited by dahermit; July 23, 2013 at 06:08 AM.
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Old July 23, 2013, 06:19 AM   #13
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Quote:
It seems like the current belief is that over travel stops improve accuracy - or that at least over-travel is a detriment to accuracy. But is this really true?
For those who say that it is not, consider that photographers (before digital), used cable and air releases on cameras for critical photography. Just as shooters, they did not want the action of pressing the release button (trigger), to move the camera (gun), at the critical moment when the camera "fires".
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