From: bercov@bevb.bev.lbl.gov (John Bercovitz)
Newsgroups: rec.guns
Subject: Re: Removing firing pin plunger from 1911A1
Keywords: handgun, 1911A1
Date: 22 Aug 90 00:12:10 GMT

RE: Gayman's question about removing firing pin block from gov't mod
    One isolated experience:

I took the firing pin blocking plunger out of my Delta Elite because
over time it began to hang down below the slide and jam the gun.  Previous-
ly it had  occasionally blocked the firing pin for no apparent reason.  The
only disadvantage I see is that a lot of unburned powder finds its way
through the plunger's hole into the firing pin's hole.  My load is 11 gn
of AA#7 behind the Hornady 170 gn bullet.  The AA#7 residue hasn't caused
any problem yet after around 500 rounds without cleaning the firing pin's
hole.  This is not to be construed as a recommendation of the practice,
however; it's merely an observation.  I think there's a lot of potential
here for causing an inopportune reduction in the firing pin's impulse.

I don't consider the job complete because I haven't thought of a convenient
method of blocking the hole.  I did turn a couple of brass spacers to take
the places of the parts I removed from the frame.  All in all, the trigger
pull is much improved: again, just an observation, not a recommendation.

Legally, I'm sure the removal of the firing pin block is a hanging offence.

From: bercov@bevsun.bev.lbl.gov (John Bercovitz)
Subject: Unsafe mode; was: Re: Concealability ?
Organization: Lawrence Berkeley Laboratory

In article <36436@mimsy.umd.edu> decwrl!well.sf.ca.us!well!rsl@uunet.UU.NET 
(Roy Stuart Levin) writes:

#I never could see the problem with carrying the new series Colt .45acps with
#hammer down since their new fireing pin design is safe in that mode.  It is
#then a matter of drawing and cocking which to my mind is only slightly slower
#than cocked and locked and having to slip off the safety.
#Any feedback?

You betchum, Red Ryder. 8-{)}.  Pulling the trigger on a Series 80 moves
the firing pin block out of the way, as one would expect.  If the hammer
then contacts the firing pin and moves it forward a small fraction of an
inch, the block can no longer rise and re-engage the firing pin.  So the
firing pin is no longer blocked when the hammer is lowered.

The gun is _NOT_ safe in this mode.  

In this mode, the Series 80 is no different from the Series 70 and its 
predecessors: under certain conditions it will fire if dropped on its 
muzzle.  In the cases of the series 70 and its predecessors, the firing 
pin tip is now closer to the primer, and, much as one would naively
expect, calculation shows that the gun can be dropped on its muzzle from 
an incrementally lower height and go off.

I guess we could argue about the half-cock notch - its use might achieve
your goal, if I read you right.  However, I have strong reservations about 
using the half-cock notch for anything other than as a "my thumbed slipped 
when I was decocking" safety.  Cocked and locked is the onlyest way to go. 
Cocked and locked gives you grip safety, manual safety, and firing pin
safety; what more could you want?
        
        JHBercovitz@lbl.gov    (John Bercovitz)

From: bercov@bevsun.bev.lbl.gov (John Bercovitz)
Subject: Re: Unsafe mode - erratum & apologia
Organization: Lawrence Berkeley Laboratory

In article <36518@mimsy.umd.edu> bercov@bevsun.bev.lbl.gov 
(John Bercovitz) writes:

#Pulling the trigger on a Series 80 moves
#the firing pin block out of the way, as one would expect.  If the hammer
#then contacts the firing pin and moves it forward a small fraction of an
#inch, the block can no longer rise and re-engage the firing pin.  So the
#firing pin is no longer blocked when the hammer is lowered.

#The gun is _NOT_ safe in this mode.  

I was discussing some of the above further with another member of this
group when it suddenly dawned on me that I had very consistently
used the word "block" every place I meant "lock".  I apologize for any
confusion I may have created.  

Clarification: A firing pin block is a device which can be moved into place
to prevent the hammer from contacting the firing pin.  A firing pin lock is
a device which prevents the firing pin from moving even if it is hit by the
hammer.  So a firing pin block cannot prevent the AD of a firearm with a 
floating or inertial firing pin when said firearm is dropped from a sufficient
height muzzle-first onto a hard surface.  A Walther PPK is a good example
of a firearm which has a firing pin block but no firing pin lock.  A Colt
Series 80 is a good example of the converse.

Well, you see, I was thinking of the part which locks the firing pin of the
Colt as a little block which rides up and down in the slide and well...
Well, I'm so deeply ashamed..  And, and...  I can't continue. Sob. Meep meep.
   
     JHBercovitz@lbl.gov    (John Bercovitz)   8-{)} 

From: bercov@bevsun.bev.lbl.gov (John Bercovitz)
Subject: Safety & Govt Mod slide racking, was: Re: Concealability ?
Organization: Lawrence Berkeley Laboratory

In article <36591@mimsy.umd.edu> hays@ssd.intel.com (Kirk Hays) writes:

Re: Colt Government Model and similar --
#One of the gun rags had an article in the last year where a writer tried 
#to determine the relative timings of signal-to-shot for cocked-and-locked,
#loaded-with-hammer-down, and unloaded-with-hammer-down, all from leather.
#The latter two were tied for speed, and both trailed cocked-and-locked by 
#less than 1/10 second.

#The correct technique for racking the slide differs from person to person.  
#Some prefer grabbing the slide at the rear and pulling with the left hand, 
#others grab the slide at the rear with the left and push towards the target 
#with the right, and (my preference) others prefer to grab the slide with the 
#left with the barrel pointing left, and push with both hands simultaneously.
#The last method is also good for people with low upper body strength.

This is the famous "blow yer elbow off" technique, the very technique I use.
My variation is to ensure that the muzzle isn't pointing at my left elbow.
A lot of IPSC matches won't allow this technique any more because some folks
forget about where the muzzle is pointing.  It's also known as the old 
"cartridge case fragments in the hand trick" as someone (can't remember who)
pointed out here a couple of days ago.  What you do is cover the ejection port
with your left palm when you use this technique.  If you have an extended
ejector ala 9 mm or 38 Super, you may be clumsy once and bounce a live one
back into the ejection port where its primer may be struck by the ejector
as the slide continues to open.  This happened to a very good friend of mine 
a few weeks ago when he was firing a Colt 38 Super I had built some time ago.  
Fortunately for him, one of the competitors at the local IPSC-style matches
is a physician.  No nerves or tendons were hit.

Except for risking blowing off your elbow and wrecking your hand, I think this
is a darn good technique.  It allows you to maintain maximum control of the
gun.  That's why I use it.  I also keep my finger on the trigger when I rack
in a fresh one so I won't encourage hammer-follow.  The problem with this
technique is that if you have a momentary lapse of attention and loosen your
pull on the trigger and then quickly correct yourself, you blow your elbow
off again.  Oh well, crossing the street is risky, right?  Lot easier on the
elbows, though, I guess.

   JHBercovitz@lbl.gov    (John Bercovitz)   8-{)}

From: bercov@bevsun.bev.lbl.gov (John Bercovitz)
Subject: Re: Unsafe mode; was: Re: Concealability ?
Organization: Lawrence Berkeley Laboratory

In article <36718@mimsy.umd.edu> bcstec!iftccu!bressler@uunet.uu.net (Rick Bressler) writes:
#Does anybody out there know for sure?  Does the firing pin lock work
#on a model 80 when the hammer is down?  I'm curious now.  Maybe I should
#hop up to the local gun shop and check for myself.... :-). (Another
#excuse to go :-).

I have a series 80 Delta Elite.  The firing pin lock does not work on my sample 
when the hammer is down.  I do not know if this is true on all series 80 Colts.
(Though I'm mighty suspicious that it is.)

JHBercovitz@lbl.gov    (John Bercovitz)

From: bercov@bevsun.bev.lbl.gov (John Bercovitz)
Subject: Re: Concealability ?
Organization: Lawrence Berkeley Laboratory

In article <36722@mimsy.umd.edu> cash@convex.com (Peter Cash) writes:

#There has been discussion in this group recently about the danger of
#accidental discharge when dropping an autoloader that lacks a firing pin
#lock. (This device retains the firing pin and always keeps it from moving
#except when the trigger is squeezed.) Guns that lack such a lock--e.g., the
#Colt Series 70 models and the Walther PPK, are supposedly risky to carry
#with a loaded chamber and the safety off.

I have a red face: I was cleaning my PPK last night and found that at least 
mine has both a block and a lock for the firing pin.  I'm very sorry about
misleading everyone.        8-(

#I can't resist asking: Does anybody have any first-hand experience of an
#uncocked pistol going off when dropped? Do you have any second-hand
#knowledge? (Sorry--third hand knowledge is classified as urban legend.)

Second hand: A peace officer in our little police department here at the
laBORatory dropped his cocked and locked Series 70 Colt Commander muzzle-
down on concrete steps which he was going up in pursuit of a perp. It went off,
much to his embarrassment.  I examined the gun before and after the accident. 
It appeared to be just as he said - there were new scratch marks at the muzzle.
This accident happened at another site - I surely don't want to start any rumors
about what goes on at this serene site!
 
#I guess I'm a little skeptical about the likelihood of a firing pin
#acquiring enough inertia during a drop from shoulder height to actually set
#off a primer. Perhaps someone should do an experiment on this...somebody
#who doesn't mind dropping his gun muzzle-first repeatedly on hard surfaces.
#(Just use primer-only blanks, please.)

Excellent idea!  I'm always in favor of such things.  However, an actual
experiment may not be necessary.  As I understand it, what's required to
set off a primer is enough energy to deform the primer cup and enough
firing pin speed so that the primer pellet gets the energy input rapidly.
Looking in Hatcher's Notebook (see primer sensitivity in the index), I'll 
guess that probably .25 in-lb of energy will set off the odd pistol primer.
Since the firing pin in my Gold Cup weighs 71 gn or about .01 pounds, the
gun would only have to fall 25" onto a hard surface to set it off. 
(The appropriate formula here is: force * distance = kinetic energy. 
Weight is defined as the force gravity exerts on a mass.)

One could further refine the calculation by taking into account the energy
which the firing pin spring would absorb.  Then one must add another 5" to
the fall required to set the gun off.  However, if the gun is carried hammer 
down, part of the movement of the firing pin has already been made so one would 
only have to add 2.5" to the 25 inches.  Please don't take these figures as
exact; they are intended only to demonstrate the scale of the factors in this
problem.

      JHBercovitz@lbl.gov    (John Bercovitz)

From: bercov@bevsun.bev.lbl.gov (John Bercovitz)
Subject: Re: Unsafe mode; was: Re: Concealability ?
Organization: Lawrence Berkeley Laboratory

In article <36749@mimsy.umd.edu> bercov@bevsun.bev.lbl.gov 
(John Bercovitz) writes:
#In article <36718@mimsy.umd.edu> bcstec!iftccu!bressler@uunet.uu.net 
(Rick Bressler) writes:
##Does anybody out there know for sure?  Does the firing pin lock work
##on a model 80 when the hammer is down?  I'm curious now.  Maybe I should
##hop up to the local gun shop and check for myself.... :-). (Another
##excuse to go :-).

#I have a series 80 Delta Elite.  The firing pin lock does not work on my sample
#when the hammer is down.  I do not know if this is true on all series 80 Colts.
#(Though I'm mighty suspicious that it is.)

Anybody got a good recipe for crow?  I've been ingesting a lot of it recently.

I did a survey of various Series 80 Colts last night and found that it is 
clearly Colt's intent that the firing pin lock work with the hammer down.
The survey consisted of visiting a gun shop on the way home and calling a
few friends who have Series 80 Colts.  All of the guns examined locked the 
firing pin with the following exceptions:
1) Mine - mainly the notch in the firing pin is too far forward so it prevents
   the lock plunger from dropping when the pin is a little forward.
2) One at the gun store - the lock plunger is a little rough and sticks in
   its hole a little; it could potentially stick in the up position.
3) Another one at the store - the lock system's parts had too much clearance
   and it was possible to push on the firing pin such that its tip projected
   a very short distance from the breech face even though the lock plunger was
   engaged.
4) One belonging to a friend of mine - the lock plunger was jammed in the
   up position by an accumulation of powder residue.
This survey was a much better survey than my previous survey which consisted
of one sample.  8-)  The present survey consisted of roughly 40 guns (I didn't
count them but there were maybe 20 in the store + several from each IPSC
competitor).

This exercise did not inspire confidence in Colt's locking system.
I think it would be worth your time to check your firing pin lock if you have
a Series 80.  The test is simple to do - all you have to do is lock the
slide back and you will find easy access to all of the pertinent parts right 
there at the rear of the slide.

      JHBercovitz@lbl.gov    (John Bercovitz)

From: bercov@bevsun.bev.lbl.gov (John Bercovitz)
Subject: Re: Safety & Govt Mod slide racking, was: Re: Concealability ?
Organization: Lawrence Berkeley Laboratory

In article <36932@mimsy.umd.edu> cash@convex.com (Peter Cash) writes:

#Another point about guns going off when they're dropped: it seems to me
#that if the discharge is due to firing pin inertia, then the gun must
#strike the ground muzzle first. In this case, the bullet will go into the
#ground (well, if you're extremely unlucky, someone could be hit by a
#ricochet). True, recoil will spin the gun up in the air,and where it lands
#nobody knows. But unless it hits muzzle first again, and if the safety is
#on, you won't have a second discharge. All in all, I don't think that this
#is something that you ought to worry about a lot.

The only problems I've heard of have to do with spalling of the concrete -
the concrete chips go flying and cause cuts about the shins.  Has anyone
heard of worse problems than this?  Certainly some potential must be there,
however minor it may be.
 
       JHBercovitz@lbl.gov    (John Bercovitz)

From: bercov@bevsun.bev.lbl.gov (John Bercovitz)
Subject: drop & fire was: a lot of things
Organization: Lawrence Berkeley Laboratory

In article <36994@mimsy.umd.edu> gmk@falstaff.mae.cwru.edu 
(Geoff Kotzar) writes:
[regarding dropping guns which don't have firing pin locks on their muzzles]
#One question: has any damage occurred to the guns in the vicinity of the
#muzzle? I would think that the ground/concrete would appear as an obstructed
#barrel of sizable proportions and could result in a bulged barrel right in 
#the region of the barrel bushing.

I've never read of damage to the gun.  It may be theoretically possible
on concrete.  If you look at the situation from a momentum standpoint,
the gun, dropped vertically onto its muzzle, will have come off the ground
less than 1/10th of an inch by the time the bullet's point hits the concrete.
Government models are pretty tough though.  Who was it, Hatcher, who had to
run the load behind a 230 gn bullet up to 12 gns of Bullseye before the gun
would wreck itself?

This is pure speculation, but what we're talking about may not be a self-
locking type of a jam.  Dirt in the muzzle is sort of self-locking in that 
the ogive of the bullet tries to jam the mud radially outward into the barrel
which greatly increases the force required to move the bullet further.  If 
you have a bullet stuck near the muzzle, the moving bullet crashes into the
base of the stationary bullet and expands it again producing a self-locking
effect.  I don't see the present situation producing a self-locking effect.
Certainly the inertial load on the gas goes up by a factor of 50 or more as 
the mass being accelerated changes from that of a bullet to that of the whole 
gun.  But the gas pressure is pretty low when the bullet gets to the muzzle so
50 times something low is still pretty low.  There's a lot more to it than 
that, of course; you've got pressure waves reflecting back and forth for 
starters.  These pressure waves can detonate any remaining unburned powder. 
But even detonated powder can only add a finite number of gas molecules at a 
finite temperature to the existing population of gas molecules in the barrel.
Like I said, though, this is pure (idle) speculation.

    JHBercovitz@lbl.gov    (John Bercovitz)

From: bercov@bevsun.bev.lbl.gov (John Bercovitz)
Subject: AD of 1911 - experiment
Organization: Lawrence Berkeley Laboratory

I did an experiment yesterday to try to determine from what height a 1911
would have to be dropped to cause it to accidentally discharge due to the
impact of its floating firing pin.  I made up a dart from a crossbow bolt,
an RCBS shell holder for the 45 ACP case, and a few machined parts includ-
ing a floating firing pin of 71 grain weight.  Using old CCI magnum large
pistol primers and Federal large pistol primers, I dropped the dart from
various heights in an attempt to set off a primer.  I tried five of each
primer at heights of 5 and 10 feet and 10 of each primer from a height of
15 feet.  None of the primers discharged although I was getting a pretty
good dent in the primers from the 15 foot drop.  The dents in the old CCI
primers were much deeper than those in the new Federal primers.  The impact
surface was concrete.  15 feet is high enough for me to feel safe.  So I
have to wonder if the Series 80 firing pin lock isn't a solution to a non-
existent problem.

If anyone would like to have the test apparatus to continue the experiment,
let me know.  I am willing to send it to a serious party for the cost of 
postage and the cost of the shell holder which the apparatus contains.

      JHBercovitz@lbl.gov    (John Bercovitz)

From: bercov@bevsun.bev.lbl.gov (John Bercovitz)
Subject: Re: AD of 1911 - experiment
Organization: Lawrence Berkeley Laboratory

In article <38993@mimsy.umd.edu> bercov@bevsun.bev.lbl.gov 
(John Bercovitz) writes:

#I did an experiment yesterday to try to determine from what height a 1911
#would have to be dropped to cause it to accidentally discharge due to the
#impact of its floating firing pin.  I made up a dart from a crossbow bolt,
# [stuff deleted]

Henry Schaffer has brought up several implications concerning the 
coefficient of restitution of my 1911-simulating primer-testing 
dart Vs. the coefficient of restitution of the barrel of a 1911 
dropped on concrete.  I can't speak for the 1911 (Does one of 
you want to volunteer yours for the experiment?), but I dropped 
a similar piece of steel on some smooth concrete from a height 
of 150 cm and, out of several trials, got a peak rebound height 
of 60 cm for a coefficient of restitution of (60/150)^0.5 = .632. 
This means the velocity of the rebound is 63.2% of the velocity 
of impact.  I also got a 60 cm rebound for a piece of 6061-T6 
aluminum, the material I used to construct the simulator dart.  
So the simulator dart and the 1911 have the same coefficients 
of restitution, at least to the first order.

Since I dropped the simulator from a height of 15 feet, its 
impact velocity must have been (2*32.174*15)^0.5 = 31.1 fps.  
The firing pin of the simulator was up against the primer so 
31.1 fps was the speed at which the firing pin struck the 
primer.  Now if the firing pin had been far enough away from 
the primer for the rest of the device to rebound before the 
firing pin hit the primer, the closing velocity of firing pin 
and primer would have been increased by 63% to 50.7 fps.  It 
all really depends on how long the rebound process takes 
compared to the time it takes the firing pin in the 1911, 
traveling at 31.1 fps, to cover the distance to the primer from 
its initial, spring-retracted, position.  Certainly a very hard 
impact surface will decrease this rebound time if my intuition 
is correct.  So a hard impact surface will more likely cause an 
accidental discharge (AD) due to this effect as well as the
expected effect.

Supposing the worst case, that the 1911 has enough gap between 
firing pin and primer to allow the rebound to occur before the 
firing pin hits the primer, I should have dropped my simulator 
from a height of (50.7^2)/(2*32.174)= 40 feet to simulate a 
1911 drop from 15 feet.  Conversely, my test from 15 foot 
height simulated (in the worst case) a 1911 drop from a height 
of only 5.6 feet.

If this worst-case rebound scenario is true, then a 1911 would 
be safer hammer-down than cocked-and-locked since the firing pin
would have less far to travel until impact and hence would be
unlikely to get this velocity-increasing effect on softer impact 
surfaces.

I guess the cure here is going to be for me to spring load the 
firing pin off the primer the correct distance so as to better 
simulate the drop of a 1911.  Thank you so much for suggesting
I look into this, Henry, you dog you.  8-)

     JHBercovitz@lbl.gov    (John Bercovitz)

From: bercov@bevsun.bev.lbl.gov (John Bercovitz)
Subject: success: 1911 drop test, or H.S. was right
Organization: Lawrence Berkeley Laboratory

For those who didn't see the previous post, I made a pre-
Series '80 1911 simulator to see what height a 1911 had to be 
dropped from to cause an accidental discharge due to the 
unrestrained firing pin.  The simulator had a firing pin with 
71 grains of mass just as the 1911 has, but it did not have a 
retractor spring so the firing pin of the simulator rested 
right on the test primer.  I did not get an "accidental 
discharge" even when dropping the simulator from a height of 15 
feet onto the concrete.  Henry Schaffer pointed out that this 
was an optimistic test since, if the firing pin were backed 
off of the primer at the time the body of the simulator hit, 
the body of the simulator would have time to rebound before 
the firing pin hit the primer thereby nearly doubling the
relative velocity of firing pin and primer.  

The new simulator design incorporates a retractor spring and 
has a firing pin travel of .075 inches just as the cocked and 
locked 1911 does.  The firing pin tip is an .060 inch diameter 
hemisphere as with the 10 mm version of the 1911 rather than 
an .090 diameter hemisphere as with the 45 ACP 1911.  I 
figured this would be a tougher test since a smaller pin has 
less metal to displace and so would have an easier time of 
setting off the primer's pellet.  Below are the results of the 
tests with this simulator.  The results are in the form: how 
many fired/how many were dropped (five of each primer were 
dropped from each height).  Thank you, Henry, for pushing me a 
little further down this road.

   drop      velocity    CCI magnum   Federal standard
  (feet)    (feet/sec)   large pistol  large pistol
    15         31.1          5/5            5/5
    10         25.4          5/5            5/5
     9         24.1          5/5            5/5
     8         22.7          5/5            5/5
     7         21.2          0/5            1/5
     6         19.6          1/5            0/5
     5         17.9          0/5            0/5

At a drop distance of 5 feet, the mark of the firing pin on 
the primer was very weak leading me to believe lower height 
tests would be unproductive.  These results are only an 
indication; note that sample sizes are _extremely_ small so
one would expect some very few discharges at the 5 foot height 
and below if a Gaussian curve holds for this situation.

Anybody for putting a rubber bumper on the muzzle of the 1911 
to gently slow the gun down while the firing pin lands on the 
primer?  8-{)}

        JHBercovitz@lbl.gov    (John Bercovitz)