Help: Enfield No. 4 breaks firing pin, punctures primers
Mark J. Blair
I have an Enfield Number 4 Mk I/II rifle, manufactured in 1942 and
FTR'ed in 1956. I brought it to a local gunsmith for a safety
inspection and test firing. He said the gun was fine and had good
headspacing. He gave me the shell casing from the test firing, and it
looked fine (no bulges or punctures). I measured the firing pin
protrusion myself with a caliper, and it appears to be within the
correct range (between 0.04 and 0.05 inches). My rifle has a #1 bolt
head. This is my first high-powered rifle, so I don't have any prior
experience shooting rifles like this one.
I took the rifle to the range and fired it for the first time, using
Winchester 174 gr. FMJ factory ammo. The second shot broke the firing
pin at the notched flange which presses against the spring. I
inspected the shell casings and found that both had punctured primers
(they were punctured cleanly where the firing pin hit them). The
primers had backed out slightly to become flush with the back surface
of the casing, but didn't look like they backed out excessively to my
inexperienced eyes. The shape of the shoulder of the casing changed
very slightly, but I have to hold an unfired round right next to the
casing to tell the difference.
To the rifle's credit, it contained the devastation so effectively
that, aside from a mild sunburn, I was uninjured. In fact, I didn't
know anything was wrong until the third shot made a lot less noise and
recoil than I expected ("click" instead of "BOOM!").
At this point, I don't have much faith in the gunsmith who inspected
my rifle, so I'd like to repair and inspect it myself and make sure
it's done right (after all, it's my face pressed against the
cheekpiece!). Assuming I can find one at a gun show, I can easily
replace the firing pin (luckily, there was just enough of the flange
left on the broken pin for my home-made firing pin wrench to be able
to turn it!). However, if the rifle has any more serious problems, I
will need to take care of those, too. Here are my questions:
1. What causes punctured primers? Is the pin punching through from
the back, or is the primer being blown out from the inside due to
excessive chamber pressure?
2. How can I fix whatever causes the punctured primers?
3. Do you think the gases escaping from the punctured primer caused
the firing pin to break, or is that probably an unrelated
coincidence?
4. How do I inspect the rest of the rifle for invisible cracks or
fatigue which could make it unsafe to shoot?
5. Finally, what special-purpose tools and supplies should I consider
essential for inspecting my firearms (especially the old surplus
ones!) for problems that could make them dangerous to shoot?
Thanks for any advice! I'd prefer an email response, because I don't
read this newsgroup very often. I'll summarize in a later followup if
requested.
--
Mark J. Blair KE6MYK
e-mail: mbl...@gruumsh.irv.ca.us
Mark J. Blair
Sorry, the headers were messed up in my previous posting. This article
should have correct From and Reply-To fields.
In article <5fvp0q$p...@xring.cs.umd.edu>, Mark J. Blair <mbl...@gruumsh.irv.ca.us> wrote:
#
#I have an Enfield Number 4 Mk I/II rifle, manufactured in 1942 and
#FTR'ed in 1956. I brought it to a local gunsmith for a safety
[...]
Mr. Ronald C. Bloom ii
If the firing pin is backing out, you have bad headspace, and need to
buy a bigger bolt head, they go up to #4 I believe. Is your firing pin
jagged?? The firing pin breaking might be a coincidence.
Ron Bloom
Gun Owners Action League of New York
Mark J. Blair
In article <5g40h8$4...@xring.cs.umd.edu>,
Mr. Ronald C. Bloom ii <TDW...@prodigy.com> wrote:
#If the firing pin is backing out, you have bad headspace, and need to
#buy a bigger bolt head, they go up to #4 I believe. Is your firing pin
#jagged?? The firing pin breaking might be a coincidence.
It is only jagged where it broke; it previously appeared smooth to my
eye all over. It broke diagonally through the flange against which the
spring presses, and it looks like the crack may have started in one of
the notches that the spanner wrench grabs on the flange.
My gunsmith said the headspace was good, but if I can find the
appropriate headspace gauges at a reasonable cost, I'll re-check it
myself to set my mind at ease. I know about the different available
bolt face sizes that I can use to remedy headspace problems; I
wouldn't consider trying to fix a headspace problem myself otherwise!
Another response that was relayed to me via email from somebody's
gunsmith suggested that I probably do not have an overpressure
problem, and that it is likely that the firing pin was OK when my
gunsmith checked it, but broke either on my first shot or on a
previous dry-firing. He suggested that the punctured primer may have
been caused by the broken firing pin, because there was nothing to
stop it from protruding too far from the bolt face, and that there
typically isn't any visible sign of fatigue before the pin breaks.
There was some good general advice in the response I mentioned. I'll
repost it here if I get the go-ahead from the folks who sent it to
me.
Unless somebody else suggests otherwise, I guess I'll scrounge up a
new firing pin, make sure its protrusion is correct, and try it out. A
friend of mine suggested that I place a sandbag over the receiver when
I test-fire it until I satisfy myself that I've cured any
primer-puncturing or potential case-rupturing problems.
I should point out that I don't have any real evidence that my
gunsmith did a poor job; I just have less faith than before, and a
stronger desire to learn to do some of the basic gunsmithing tasks
myself. I won't post the name of the gunsmith or generate any bad
publicity for his shop without real proof of jokerism!
Mark J. Blair
In article <5g7d37$e...@xring.cs.umd.edu>,
Mark J. Blair <mbl...@gruumsh.irv.ca.us> wrote:
#Another response that was relayed to me via email from somebody's
#gunsmith suggested that I probably do not have an overpressure
[...]
#There was some good general advice in the response I mentioned. I'll
#repost it here if I get the go-ahead from the folks who sent it to
#me.
Here it is:
============== Forwarded message ======================================
#1. What causes punctured primers? Is the pin punching through from
# the back, or is the primer being blown out from the inside due to
# excessive chamber pressure?
No way to tell for sure as the signs are pretty much the same in either
situation; however, if the case extracts easily, the problem is probably not
pressure-related. Chances are that your firing pin was O.K. when your
gunsmith inspected the rifle but broke subsequently--either from dry-firing
or from an actual shot--either his test shot or your first shot at the
range. A broken firing pin will often pierce the primer because it no
longer has anything to stop it from going too far forward.
#2. How can I fix whatever causes the punctured primers?
The fix is almost certain to be a new firing pin. After installing it,
check to see that the protrusion is 1/2 the diameter of the firing pin, plus
or minus 0.005 inch. For example, if the pin diameter is 0.080, the
protrusion should be 0.035-0.045 inch. If you have to shorten the pin, file
it to a hemispherical shape and then polish it with emery cloth.
#3. Do you think the gasses escaping from the punctured primer caused
# the firing pin to break, or is that probably an unrelated
# coincidence?
It's not likely at all that the punctured primer caused the firing pin to
break. It's much more likely to be the other way around, as noted above.
#4. How do I inspect the rest of the rifle for invisible cracks or
# fatigue which could make it unsafe to shoot?
For the most part, you won't find any cracks on inspection (although bright
lines are always a point of interest). Generally, the metal looks fine
until it breaks. When it fails, it fails all at once. Don't be too hard on
your gunsmith, because you never know when a firing pin will break. It may
look fine and then fail the very next dry firing or line firing. Only very
rarely will you see a fatigue crack beforehand. A careful inspection of
fired cases is your best source of information on the condition of a gun.
#5. Finally, what special-purpose tools and supplies should I consider
# essential for inspecting my firearms (especially the old surplus
# ones!) for problems that could make them dangerous to shoot?
BOOKS! The correct information is a must. Good dimensional drawings of
cartridges are essential, as are a dial caliper and a micrometer to take
proper measurements. For disassembly, get a good set of hollow ground
screwdrivers and a set of pin punches. You can't buy too good a set of
punches! (I like Starrett, myself.) Head space gauges are expensive and
only fit one caliber, so let your checkbook be your guide. Finally, you
need a good place to work--a sturdy bench, a padded vise, and a good bright
light.
Then get some more books. Get some references to learn the proper way to
read the drawings and use the dial caliper and micrometer
and--especially--what to look for in reading fired cases. (Most reloading
manuals have good sections on reading fired cases--get several of them.)
Also a book or two about your rifles of interest.
I'm sure I've forgotten something, but I'll think of whatever I missed while
you're reading all those new books!
Steve Brandt
Brandt's Gun Shop
Moscow, Idaho
============== End of forwarded message ===============================
Dinosaur
Another cause of punctured primers on the Enfield is a too-weak firing
pin SPRING.
Mark J. Blair
In article <5g97k8$l...@xring.cs.umd.edu>,
Dinosaur <middl...@avalon.net> wrote:
#Another cause of punctured primers on the Enfield is a too-weak firing
#pin SPRING.
Really? Why? That sounds kind of strange to me.