Some Thoughts and Questions on Dropping the Slide

[Bergeron]

As I haven't been shooting my 1911 since early September, I've been doing some thinking about the practice of dropping the slide under full spring pressure and an empty magazine/no magazine. I've read in manuals and heard in the internet that such a practice is not only sloppy gunhandling, but can damage the firing mechanism of the pistol, and that 1911s with trigger jobs are especially succeptible to damage.

Seeing how my baby has a really nice trigger, I'm not gonna tempt screwing that up by acting like an idiot with one of my pistols, but I was hoping that I could encourage a techinical discussion of the physics involved.

Let's start by assuming that we are using a .45 1911 with a trigger job that has a ~17lb. recoil spring and that we are using Chip McCormick 10 round magazines.

(Note: I am interpreting a "17lb recoil spring" as a spring that requires 17lbs of force to be completetly compressed)

By earlier statements of manuals and the internet, we know that we are NOT hurting the trigger job by firing the pistol with ammunition in the magazine.

The final velocity of the slide will be dependant on the weight of the recoil spring, the length of the slide stroke (BTW, does anyone know that number?), and the force required to strip the round out of the magazine. I will assume that the energy required to move the barrel back into battery and lock the pistol is negligible, or at the very least, it will not change whether or not we have an empty chamber, and can be discounted.

Okay, so the most force required to strip the round will be when it is loaded to maximum capacity, the least force will be the last round. Again, we will assume that stripping the last round absorbs enough spring energy to not damage the trigger job.

This is where we are going to have a little fun. I don't have anyway to measure how much force that is, though I imagine that I could measure it with a trigger pull device. How much force does THR think it would take to strip the 1st round and then the 10th?

Now that we have the spring weight, slide stroke length, and force required to strip the round, we can calculate final slide velocity and compare it to the slide velocity when we drop the slide on an empty chamber.

What I am getting around to, is, does the board think that the final slide velocity of a ~17lb recoil spring 1911 stripping a round will be compared to say, a ~11lb sprung bullseye wadcutter gun dropped on an empty mag?

I've read about folks with 20-26 lb sprung 10mm and .45 Super pistols, and I personally doubt that those guns have slide velocities when fired with loaded magazines that are less than, say, a 14lb USPSA Limted pistol dropped on an empty magazine. BUT, I do know that the slide velocity IS less when the gun has to strip a loaded round. If anyone can come up with the numbers I would need, we can run through some calculations. I am more than willing to accept the viewpoints contrary to my own.

If anyone is very curious, and has a high-speed camera, we could do some really cool experiments and help to settle the argument.

What does everyone else think?

I'm still not gonna drop MY slide on an empty chamber.

 

[Jammer Six]

I'm still not gonna drop MY slide on an empty chamber.

You will if you want to shoot in a league that uses a cold line.

In our plate league, when you finish your run of plates, you drop the magazine, clear the weapon, show the range safety guy that it's clear, then drop the slide, point it downrange, and dryfire.

Then you can leave the line.

You need to drop the slide just as if there was a magazine in the weapon, so that if there is a magazine in the weapon, it will chamber a round.

If you don't, the range officer will stop you, and ask you to do it according to the rules.

Go ahead, ask me how I know that.

There are a few other factors that affect how fast the slide goes home, mainspring, leaf spring and disconnector/disconnector channel, to name a few of them.

 

[Bergeron]

Huh. Seems that dropping the slide slow would chamber a round same as if you let it down slow, but, their rules, and if ya wanna play...

Guess I should reconsider that last statement:

"I would PREFER NOT to let my slide slam on an empty chamber."

I appreciate your comments on how mainspring, leaf spring and disconnector/disconnector channel affect slide velocity. I had considered them to be negligible, or at least constant in the same gun, and not worthy of consideration. How much effect do you think that they have?

Like I said, I really need to get my hands on a high-speed camera. Or even better, a winnng lottery ticket .

 

[Jammer Six]

I think that of the three, the mainspring would be the most significant- the hammer actually has quite a bit of surface area in contact with the bottom of the slide. I also think that it has more of an effect on the slide recoiling, (that and the firing pin stop) but it does have an effect on the slide dropping. I noticed it when I changed mainsprings, but didn't realize why until John explained it to me.

That said, I'll tell you the guy to ask- 1911 Tuner.

He taught me everything I know, and he'll be happy to help you.

Good luck!

 

[Ivy Mike]

so its not the best idea to drop the slide on a 1911.

What about better designed pistols?

 

[Bergeron]

Yes, he is the man. I really wanna get some numbers to crunch.

I'd like to stay focused on the 1911, before moving to other designs. BTW, I read that the original 1911, with it's 6-8lb trigger pull, was pretty much immune to slide dropping. It's really only those guns with nice trigger jobs that are succeptible. I think.

 

[MoNsTeR]

What about better designed pistols?

In any hammer-fired auto where the fully-open slide holds the hammer in an "overcocked" position (which, I'll bet, is any hammer-fired auto), letting the slide close rapidly will allow the hammer hooks to contact the sear face with some vigor.

Striker-fired autos... don't have hammers, so the whole discussion doesn't apply. Also, I suppose DAO hammer-fired autos don't have sears, so it wouldn't apply to those either.

 

[Jammer Six]

What about better designed pistols?

If one ever shows up, you let us know.

 

[Double Naught Spy]

I have a lot of trouble believing that the presence of a round will slow the slide just enough to prevent supposed undue wear and tear, hence protecting things like the trigger job. How does that slight amount of added resistence make so much difference? If the guns were that sensitive, then things like +P ammo would be causing lots of damage.

I haven't ever had a person such as a smith be able to look at a gun and determine that the owner had been dropping the slide on an empty chamber.

 

[Ivy Mike]

If one ever shows up, you let us know.

Don't make me drop the G word...uh oh, too late.

G as in Glock.

*ducks and runs*

 

[9mmepiphany]

the 1911 platform with a "trigger job" has a more "fragile" engagement between the sear and the hammer hooks. it isn't a problem when you are actually firing the gun because you are holding the trigger back..this disengages the contact surfaces.

hence, when allowing the slide to slam onto an empty chamber, you should hold the trigger back

 

[Jammer Six]

Huh?

Can you explain that?

I thought that the sear hits the hooks even though the trigger is held back- and that that is, in fact, the purpose of the disconnector.

If the trigger actually held the sear back from the hammer hooks, you would have a full auto weapon.

The fact that the trigger being held back doesn't prevent the sear from hitting the hooks is what makes the weapon a semi automatic weapon instead of a full automatic weapon.

 

[Bergeron]

Double Naught Spy, thank you for your post.

That is esentially the question that I am posing. I don't know how much it takes (quantitatively) to feed a round from the magazine, but I suppose that it is less than the difference between a 10mm/.45 Super 1911 running a 20-26 lb recoil spring and a 14 lb sprung IPSC .40 1911. I've never heard that it would not be possible to have a heavily sprung pistol with a durable trigger job, so this is why I am supisicous when I hear that it might damage the trigger on a lightly sprung gun to drop the slide without a "cushoning" round.

I would like to go on things other than gut feeling, so if we can come up with a way to quantify the force required to strip a round out of the magazine, it should be possible to determine the final slide velocity and make some statements that can be backed up with more than "gut feeling".

9mmepiphany, I have also heard that squeezing the trigger while allowing the slide to slam on an empty chamber would avoid damaging the trigger, and have seen such an action suggested in a partial reprint of a military manual in a back issue of American Rifleman. I am ignorant, however, of exactly why this works. My knowledge of the internals of the 1911 is insufficient.

 

[enfield]

Huh. Seems that dropping the slide slow would chamber a round same as if you let it down slow, but, their rules, and if ya wanna play...

Yeah, it seems that way but it ain't so. Without the full velocity going forward, the grooves in the slide may not engage the ribs on the barrel correctly. It may look OK, but the gun is out of battery. You can get a nasty surprise when you fire it that way.

You need to let the gun operate the way it was designed to operate.

If operating the gun safely breaks it, the fault isn't yours.

 

[taliv]

IANA1911guru, but bill wilson's videos that he ships with his guns explain that what you're hurting is the barrel linkage. i don't recall him ever mentioning damage to the trigger.

 

[wally]

Compare the amount of metal in the frame that stops the slide going forward vs what stops it going backwards. No decent 1911 will quickly break from the slide slamming forward on an empty chamber -- it'll happen from time to time in normal use when you get a mag that fails to lock back. Doing it excessivily to look cool and show-off will cause excessive wear eventually.

It may not seem like much, but the resistance from chambering a round reduces the impact. I can feel & hear the difference dropping the slide on a dummy round vs. with an empty mag.

I don't see how it could affect a safe trigger.

--wally.

 

[1911Tuner]

Slam!

Will wait for a while longer...

Meanwhile, everyone may do as they wish with their own pistols...but don't
purposely do it to one of mine unless you plan on buying it...and we thank you for your support.

 

[quantico]

I would question for league shooting why dropping a 1911 slide with the slide release is safer than closing it with your hand ???? especially since you allready dropped the mag... and will shortly drop the hammer... Don't the safety guys have a clue ???

 

[mete]

Sometimes range officers DON"T have a clue !! Like the time the RA insisted I drop the hammer. He didn't seem to understand that a P7 doesn't have a hammer !!!!

 

[HankL]

I'm not sure that my method would be considered scientific by any means.
By holding the base of several 1911 magazines in a vise and stripping rounds off using a RCBS trigger pull scale I come up with an average of 4 1/2 lbs.

 

[1911Tuner]

4.5 Pounds

Hank said:

By holding the base of several 1911 magazines in a vise and stripping rounds off using a RCBS trigger pull scale I come up with an average of 4 1/2 lbs.
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That's a start. More to it than that. Consider that the round strikes the feed ramp...angles upward and strikes the throat while the rim is camming the extractor open under presssure. Friction between the case rim and breechface and between the bullet ogive and the top of the chamber.

Consider the point of contact between the side of the case with the top of the barrel throat as the round tries to break over to horizontal.

Consider also the inertial resistance of a cartridge that weighs close to one ounce. Little things add up. Everything means something. Anything that CAN have an effect on the slide's momentum and velocity WILL have an effect. Without ammunition present, there is only wind resistance to slow it down once the spring has overcome the slide's inertial mass.

 

[Wildalaska]

Meanwhile, everyone may do as they wish with their own pistols...but don't purposely do it to one of mine unless you plan on buying it...and we thank you for your support.

Ditto

WildandnocylinderflippinorsightinggunssidewayseitherAlaska

 

[HankL]

Going a step further. I pulled the hammer and recoil spring from a fairly stock 1911. My trigger pull scale only goes to 8 lbs and this was not enough to chamber a round. My guess would be in the 10 lb. range.
Tuner said

Without ammunition present, there is only wind resistance to slow it down once the spring has overcome the slide's inertial mass.

You are wrong my friend. The slide must overcome the small resistance of the disconnector, ammo or not.

 

[MoNsTeR]

It's one thing to worry about forward slide velocity if we're somehow worried about slide-dropping damaging the lockup. If, on the other hand, we're worried about damaging the fire control mechanism, then we're not interested in slide velocity per se but rather its effect on the velocity with which the hammer hooks contact the sear face.

Considering the extremely short distance -- between overock and full-cock -- that the hammer has to accelerate, it seems as if slide velocity would have little or no effect. In the limiting case, imagine the slide were to disappear (i.e. close with infinite speed). That would maximize the hammer's acceleration potential. In any realistic case, the slide will close with some finite speed, and the question is whether, when the radiused portion of the FP stop begins to pass the hammer, is the slide closing slow enough to reduce the hammer's acceleration from the limiting case? Obviously at some point this can be so; if you ease the slide forward very slowly then the hammer will ease into the full-cock position very slowly in turn. But, there is some finite speed such that if the slide closes with at least that speed, the FP stop will move away from the hammer face faster than the hammer face is moving toward it, so that the slide will not limit the hammer's acceleration. Call that velocity X. At a speed of X or faster, the hammer hits the sear with full force; slower than X and the slide slows the hammer, diminishing that impact force.

Ultimately then, the question with respect to slide velocity is: does the deceleration induced by stripping a round from the magazine and chambering it cause the slide velocity to drop below X?

If it is above X with no resistance, and stays above X with resistance, then we can conclude that dropping the slide on an empty chamber is safe, because the hammer moves with the same speed as if a round were being chambered.

If it is above X with no resistance, and below X with resistance, then there is some difference.

Similarly, if it is always below X, there is some difference. The question in these two cases is, how much effect is there on hammer velocity, and is it enough to cross some hypothetical damage threshold?


I don't know if I've described my thoughts clearly enough to get the full idea across. At any rate, it seems to me in light of the above, that the effect on slide velocity of chambering a round seems unlikely to have enough effect on what matters -- the force with which the hammer hooks strike the sear face -- to really worry about. On the other hand, the hardness of the hammer relative to the sear, and the strength of the mainspring would be worth worrying about, as they would more directly determine how much damage is caused. Furthermore, I feel confident in concluding that except in pathological cases (e.g. very hard hammer+very soft sear+26# mainspring) the amount of damage done per instance is very, very small, so that dropping on an empty chamber once in a while is not worth any worry at all.

 

[1911Tuner]

Wrong?

Hank said:

You are wrong my friend. The slide must overcome the small resistance of the disconnector, ammo or not.
_____________________

Yeah! I was just testin' ya...See? Yeah! That's the ticket. I was testin' ya!


Got me, Hank! I get in a hurry and have these senior moments sometimes.
______________________

Howdy MoNsTeR,

I'm gonna hafta think about all that real slow.

Sear damage doesn't occur because the slide drops the hammer back onto the hooks, so the return to battery speed won't matter...or at least not to any signifigant degree. (Everyting means something)

It's a function of inertia as the slide hits the pistol and jerks it forward violently. The gun moves forward while the hammer and trigger try to obey the law and stand still. The hammer's mass causes the mainspring to compress ever-so-slightly and the trigger nudges the disconnect. The sear rotates away from the hooks slightly and the hammer falls back to rest.
In some instances, the trigger can actually disengage the sear from the hammer and cause it to follow to the half-cock or all the way to the firing pin.
Not even an issue with ordnance spec hammer hook and sear geometry, but
in the case of match-tuned trigger group geometry, it can damage the small
sear engagement surfaces, especially when the sear grabs the half-cock notch...which is why some of the speed hammers have a modified notch that catches the sear in the middle where it doesn't engage the hooks. It gets damaged...but not in the place that touches the hooks.

When the old dictum is given to hold the trigger to the rear on a match-tuned gun whenever dropping the slide...loaded gun or not...it keeps the disconnector form bridging the gap between trigger and sear. The trigger can't nudge the disconnect and trip the sear. Stock hammer hooks are long enough to recapture the sear, and the undersquare angle works at pulling the sear back to the bottom of the hooks.