Overtravel

[schatzperson]

Hello everyone,
Allow me to say first off that I am new to International Air Pistol, so I might be asking a stupid or irrelevant question.
I am not new to pistol shooting, having done some very informal practice with all manner of calibers and handgun types.
For the past few few weeks I have taken an interest in ISSF AP and have been borrowing a friends Anschutz SAM M10. I shoot regular 520's.
I know that I have not even begun to scratch the surface of AP, but one issue is really begun to simmer in my brain.

I can call my shots about 50% of the time and I know almost everytime I have a good shot by the lack of "whipping" movement the front sight does.

Ok this is all probably due to poor trigger control, my grip etc etc.
However it seems to me that this pistol has excessive over trigger travel that is exasperating my lack of pistol craft.

The SAM M10 has no trigger overtravel adjustment I can see.
I always thought that overtravel in a trigger is critical with slow moving projectiles, so I can imagine it cant be doing an AP pellet any good at all.

Just exactly what am I missing here?
How can an Olympic class pistol NOT have trigger over travel adjustment?

Ok Ok, go ahead and laugh off my inexpertise, but please somebody put me out of my misery and tell me what is wrong with my assumption

[David Levene]

Just exactly what am I missing here?
How can an Olympic class pistol NOT have trigger over travel adjustment?

Ok Ok, go ahead and laugh off my inexpertise, but please somebody put me out of my misery and tell me what is wrong with my assumption

I would certainly expect any top class air pistol with a mechanical trigger to have some form of trigger stop (not really needed with an electronic trigger).

Are you sure the M10 hasn't got one, it's a few years years since I handled one.

[schatzperson]

Lets see....Going by the book here....First stage travel, Weight of first stage, Trigger weight.

Nope no trigger stop in the book.
I dont see anthing in the mechanism either.

By simple dryfiring and looking at the trigger movement, there is appox 2-3 mm of movement about the trigger centre.

Yes, correct at least 2 mm.

This is not right is it ?

[David Levene]

This is not right is it ?

If you say that it cannot be adjusted then it must be right, for that particular gun. Obviously all makes / models have their own design features.

Just like with anything else, the list of features will influence a gun purchasing decision.

[Tycho]

Nope, no triggerstop on the M10 - which is one of the (few) features I actually liked about that pistol. Could easily be "customized", though, same way as Matchguns did it in the MG2 (trigger rail is stopped by screw head at the front end). Personally, I think that a triggerstop on a AP is pretty much good for nothing, and reading the first post here, I don't think that a technical solution is the way to go. Actually, I think that a triggerstop might make things worse here, but that's just MHO.

[superstring]

A little bit OT, but I hope relevant nonetheless. I'm wondering what the advantages/disadvantages are of having more or less overtravel assuming, of course, the pistol allows for this adjustment? Is it just personal preference?

[GaryN]

I think it depends on the shooter and the gun.
I first shot my Walther CPM-1 w the trigger stop set to allow overtravel. But based on my shooting, Warren Potter recommended I adjust the trigger stop for minimum overtravel. That solution worked...for me, on the Walther. On the other hand, I don't think I use it on my Pardini K58.

So I think the answer is "do what works for YOU."

[william]

David, please explain:

(not really needed with an electronic trigger)

I hope you're not going to dredge up that silliness about trigger resistance going to zero or near zero after releasing the sear.

Back to the original subject. The FP's that I've owned recently (TOZ35 and Morini CM80) had no trigger stops, and the AP's (Pardini K2, Benelli Kite and SAM M10) either have none or I've adjusted it out.

[David Levene]

David, please explain:

(not really needed with an electronic trigger)

I hope you're not going to dredge up that silliness about trigger resistance going to zero or near zero after releasing the sear.

Are you trying to say that, without a trigger stop, you don't get an additional trigger movement as the trigger releases on a mechanical gun.
Trigger resistance does not need to go to near zero to get this effect, it just needs to reduce noticeably.

[Steve Swartz as Guest]

Just out of curiosity, what is the drop-off for the most popular mechanical triggers?

Assuming the resistance is "500+ grams" immediately before the break, how low *does* the resistance go immediately after the break?

Someone mentioned earlier that their pistol went from 520 grams down to the "reset spring tension" (which they didn't specify of course) and that the difference between teh reset spring tension and 520 grams was not significant.

Anyone have any actual numbers?

I mean, let's not try to play King Canute here with this. There is no "opinion" as to the physical realities . . .

[David Levene]

Just out of curiosity, what is the drop-off for the most popular mechanical triggers?

Assuming the resistance is "500+ grams" immediately before the break, how low *does* the resistance go immediately after the break?

Funnily enough I tried checking this before leaving for work this morning but, as I was doing it freehand, the results were too variable.

On the way home from work I went into our local friendly machine shop and borrowed a lathe (not turned on).

With suitable padding I fixed my Steyr LP5P into the 4-jaw chuck, firmly enough that it wouldnt move under the force I was going to apply. I then fixed my Correx gauge to the toolpost. This arrangement allowed me to move the Correx on to the trigger in a very controlled way and stop as soon as the trigger went off.

I know that my Correx is pretty accurate and consistant at 500g; I have not tested it at other weights.

I did 5 tests, all of which were consistent within the "readability" of the Correx.

The measured weight increased to 540g, indicated by the "maximum" indicator, at which point the trigger went off. Without moving the toolpost any further the indicated weight dropped to 505g +/- 1g.

I was amazed that the reduction was so small, it feels much more when dry firing.

I then did the same thing with my Morini 162EI. The indicated weight was constant for 2mm of movement either side of the let-off point. This is exactly how it feels when dry firing.

In hindsight I wish I'd tried carrying on with the LP5P beyond the let-off point to see what happened. It didn't occur to me at the time.

[David M]

Mechanical trigger drop off weight (at release) will vary from pistol to pistol even in the same model. It is a function of friction of the sears, sear engagement, shape of sear nose and sear angle.
You can alter the feel and weight by changing the sear with some lapping and polishing, a mechanical neutral sear weight is possible but takes a lot of slow very fine work.
BUT only if you know what you are doing....
If you go too far you can end up with a sear that is unsafe and will actually kick forward (increasing trigger weight).
On airpistols with a trigger stop I normally set them to 1.2-1.5mm aftertravel (at centre of trigger).

[william]

The measured weight increased to 540g, indicated by the "maximum" indicator, at which point the trigger went off. Without moving the toolpost any further the indicated weight dropped to 505g +/- 1g.

Mr. Levene, forgive me a small gloat. For years I have been arguing that the drop in trigger force after sear release was insignificant. Thank you for providing the evidence (if one accepts that -6.5% is insignificant).

It's nice to have real numbers, but merely looking at the geometry of a well designed trigger-sear-spring system made the general conclusion inevitable.

[David Levene]

The measured weight increased to 540g, indicated by the "maximum" indicator, at which point the trigger went off. Without moving the toolpost any further the indicated weight dropped to 505g +/- 1g.

Mr. Levene, forgive me a small gloat. For years I have been arguing that the drop in trigger force after sear release was insignificant. Thank you for providing the evidence (if one accepts that -6.5% is insignificant).

On the contrary, it just proves that you do not need a great percentage drop for it to be noticeable. It also proves that such a small drop can result in the rapid movement after the trigger breaks (sometimes made less noticeable by a trigger stop). The figures and feel of my Morini electronic showed that there is no such sudden drop or movement.

It's not the percentage drop that is significant, it's the effect that sudden drop has.

[Steve Swartz as Guest]

Funny how I conversely interpreted a sharp 35 g rap in the knuckles at the instant of the shot breaking as A Bad Thing . . .

[Fred Mannis]

Funny how I conversely interpreted a sharp 35 g rap in the knuckles at the instant of the shot breaking as A Bad Thing . . .

True, but it hasn't kept people using mechanical triggers from shooting excellent scores. I am not aware of any studies/data that show that people using electronic trigger pistols shoot better scores than people using mechanical triggers. Perhaps the new Steyr LP10E will put the matter to rest.

[Steve Swartz as Guest]

Well sure Fred I never said we haven't figured out how to "deal with" the problem since firearms were invented (trigger stops and very tight grips for two oibvious examples) . . .

. . . but why "deal with" it at all if you don't have to?

As to what the net effect on "scores" would be for people who do vs. don't have to "deal with" the issue; well, you can probably guess why it would be difficult to "disprove the negative" on that one!*

Steve Swartz

*the day we cure cancer something else will become the "#1 killer" . . . there is always an extensive list of "somethings" that will prevent everyone who piocks up a gun from shooting 10.9s on every shot. Teasing out the impact of only one of those factors is somewhat problematic. But that doesn't mean we shouldn't try to reduce the number of things that stand in our way.

[schatzperson]

er....back to my original posting concerning lack of trigger stop adjustment on SAM M10 and my suspicion that this was in some way impeding my progress.
Let me say again that I am a novice ( about 5 weeks with AP).

I had a chance to do some practice with a new in the box Walther Atlanta.
I took it out of the box and adjusted the trigger stop to a "little" beyond minimum.

My M10 5 o'clock jerks were noticable after the first 10 shots. 200 shots later and target visual comparisions brought out the statistical advantage in this case of my using the Walther in this state.

Naturally there might be ( and probably is) a host of other contributing factors, but trigger overtravel seems to be the culprit.

[Steve Swartz as Guest]

Schatzperson:

Humbly submitted- these "side discussions" may actually not be "side issues" at all.

I think at least some of the posts are questioning your attribution of your observed "jerk" to the presence/absence of a trigger stop.

However, that having been said, at the end of the day *anything* that makes you "feel better" about your shooting will help.

It just might not help as much as identifying and resolving the true underlying issues.

I think what some of these "side discussions" suggest is that you may have prematurely latched onto "trigger stops" as the answer to your problem and I (and other posters) are simply not convinced that you have properly identified the source of your technique error (the trigger jerk).

Understand that the most common cause of a rapid movement at the moment of shot release might not be due to the lack of a trigger stop; that the trigger stop may be a "crutch" used to hide improper/inadequate technique.

You may be one of those people who would benefit from a design that does not require a trigger stop in the first place . . . our give and take in your thread suggests that the issue of trigger stops may be a little more subtle than you give them credit for.

Steve

[scerir]

Frankly, after many many years, I didn't realize if I shoot better with or without backlash (with or without using the trigger stop screw) on my Steyr Lp1/Lp10. I would say I prefer to shoot with a huge backlash. The shot seems to be a true "surprise shot" this way. (Are there statistics about this simple and basic topic?).