Locktime Theory

[EricW]

(Inspired, by a parallel thread - not that I think locktime reduction will help much at my skill level.)

What factors / fixes do the most to reduce lock time in a 19/2011? Hammer mass? Hammer composition - (eg. Ti versus tool steel)? Mainspring weight?

What's the best combination for most people? Past what point does the law of diminishing returns kick in? What's the lowest mainspring weight one should generally no go below to ensure reliable ignition?

Does the hammer need a minimum amount of mass for reliable ignition? (I've seen one GM with a totally spurless hammer on his open gun, but I don't know how common that is.)

Just curious what the pros think.

[ErikW]

I'm going to answer only one:

What's the lowest mainspring weight one should generally no go below to ensure reliable ignition?

17# seems to be the consensus, though some will say 15#. I dropped 17s into all my 2011s and it improved the trigger pull on a couple of them, without affecting ignition. They all still light off Win. small rifle primers, even slightly high ones.

And I don't care about lock time; I care about trigger pull quality.

[Loves2Shoot]

They all lock faster than mere mortals can work them. I've been told that the most basic 1911 will cycle in .05 or so (and I believe it from seeing a basic one go full auto from a homeade trigger job.) So, I think all the trick stuff may be fun, but doesn't really make as much a difference. I do know the mainspring makes a noticeable difference and is the cheapest to try I like the 15 but it isn't as reliable so 17's for me.

[mcoliver]

I think the shape of the firing pin stop also has a lot to do with lock time.

I remember putting in a square egw fp stop with my 13# recoil and 16# mainspring. the gun seemed to go bang, wait a little before the slide starts moving. When I tried the 19# with the same square fp stop, the "delay" seemed even more. It seemed the bang and slide action isn't instantaneous relative to the old rounded fp stop I had before.

And on the other end, I also had an aggresively rounded fp stop. My smith made the start of the radius very close to the fp stop hole. I had fp drag marks in my primers (early unlocking?) which went away only when I dropped in a "normal" fp stop.

[Flexmoney]

I thought "lock-time" was how long it took from trigger break until the round ignited?

It seems some are talking about slide cycle time?

[EricW]

I thought "lock-time" was how long it took from trigger break until the round ignited?

It seems some are talking about slide cycle time?

Flex, we're on the same wavelength.

============================================

I know this thread is really picking at straws, but all the same I'd like to hear the take on the subject from Bob, Benny, Dr. Sweeney, Brian et. al.

[shred]

Using the formula in Hatcher's notebook:

Appx Lock Time = Sqrt( 2 ms / f )

Where s is the distance travelled, m is the mass of the firing pin + 1/2 the mass of the spring, and f is the average spring weight

This formula was designed for rifles with straight firing pins, and is given without units so..

Plugging in some junkbox parts-weighings and approximations on the 1911 and possibly inappropriate guesses as to what odd units Hatcher may have been working in gives me about 0.008 seconds for the time-from-sear-release-to-hammer-smacking-firing-pin, which is similar to, but slightly on the high-side of an '03 Springfield (he measured that at around 0.005 sec using a cool low-tech but accurate timing device I may have to copy..)

Cutting the weight of the hammer 100 grains drops that lock time SWAG to 0.006 sec

Throw in a few more miliseconds for the firing pin to hit the primer, another 0.001 or so for the powder to burn and bullet to leave the barrel and that leaves 0.05 or so to clunk the slide back and forth (which would properly be called 'Cycle time')

[mcoliver]

I thought you guys were talking about this LOCK TIME?

[benny hill]

In years past we thought locktime was very important. We used titanium hammers, 23# mainsprings, titanium mainspring cap's. We figured we could get a hit on paper instead of a miss if the locktime was super fast. Did'nt work worth a damn, still had misses. Went back w/ light set-up.

[shred]

OK locktime junkies, check this out: 1000 frames per second video of a race gun cycling (sorry, a TZ was the best I could do). Count the frames from trigger-jerk to hammer fall.

The rest of the site has a ton of cool videos on it too.

If only 1K fps cameras didn't cost more than an Open gun...

[DogmaDog]

You would get a shorter lock time (time between trigger break and primer ignition) by using a heavier mainspring and a lower mass strut and firing pin, weaker firing pin spring, and a hammer with a low moment of angular momentum. EDIT: Oh yeah, I guess you could use a longer firing pin, too, to shorten the distance the firing pin has to travel to strike the primer, as in another recent post /EDIT

Most of the ultralight hammers I see look like regular "light" or "skeletonized" hammers with even more material removed near the base of the hammer, where such lightening has the least effect on moment of angular momentum...think about spinning on a barstool--you have the same mass regardless, but spin faster with your legs and arms in than out--removing mass far away from the pivot point is what will speed up a hammer the most.

Heavier mainsprings also make for heavier trigger pulls, so most seem to go with a light mainspring (17# for me).

Titanium parts are brittle, and I've heard some bad things about Ti hammers and firing pins breaking. I don't know about Ti hammer struts.

A weak firing pin spring just doesn't sound like a good idea at all, to me.

So my take would be: try a Ti strut, and use a light hammer (but don't agonize over getting the lightest). Leave the firing pin and spring alone, or maybe try a long steel FP. Use a light mainspring because a good trigger pull is more important than the lock time.

Actually, it would be interesting to see if you could modify the system so the hammer doesn't have to rotate as far to hit the firing pin...maybe one could relieve the bottom of the slide and change the hammer geometry so the hammer could sit higher in it's cocked position. Probably wouldn't notice the difference, though.

DogmaDog

[Detlef]

shred,

yeah, those Germans make cool movies, jawoll? The other ones (you can also go directly to www.kurzzeit.de ) are worth watching, too. I always point to those when someone tells me that the recoil movement begins with ignition (the movies show it begins when the bullet leaves the barrel and is most pronounced when the slide hits its rearward stop), and on other occasions...

--Detlef

[shred]

Yeah.. I really want a 1000-frame-per-second digital camera for my own nefarious purposes... too bad they still start at $6K.

In theory, recoil does begin with ignition (stuff starts going one way, which our bud Newton says means an equal & opposite force in the other direction), but in a locked-breech 1911 design, it's imperceptible until the projectile leaves the barrel and unlocking begins (plus there's some inertia to overcome)

[mpolans]

For me, a quick locktime just feels better. Theory says, the shorter the lock time, the less time you have to pull the gun off target. I can buy that.

My preferred set up is:

Titanium: trigger bow (this doesn't really matter much), mainspring cap, hammer strut, and hammer.

Steel: firing pin.

Springs: stock firing pin spring, #17 mainspring.

Yeah, titanium hammers wear quicker; big deal...to me, that's just the cost of playing the game. I've never heard of any titanium parts breaking before.