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Making dummy cartridges

10K views 16 replies 9 participants last post by  MGMike 
#1 ·
I find these to be very useful to diagnose malfunctions in all types of firearms, especially semiautomatic pistols. If one first removes the recoil spring, the slide can be manipulated very precisely so you can watch what is going on in slow motion.

Most gunsmiths I know make them as follows. It should not require mention (but I'll mention it anyway) that it should be an ironclad, strictly observed rule that NO live ammo is ever permitted on a bench where guns are being worked on.

First, do not use fired cases. They are swollen oversized and are unsatisfactory. Make dummies from live, unfired rounds, of a good standard U.S.-made ammo of reliable dimensional conformity, if available in that caliber. Read that Remington, Winchester, Federal or military. For normal testing use FMJ, unless you intend to test functioning with some other specific type of bullet.

Pull the bullet with an inertia puller, dump the powder, chamber the case in a gun and fire it. DO NOT RELY on killing primers with WD40 and the like. They are harder to kill than a vampire, and I have seen them fire after a 24-hour saturation. (A primer alone will develop enough energy to drive a bullet several inches down a pistol barrel, and just possibly clear the muzzle. It can hurt you or at least give you a brief case of uncontrolled excretion. ) So: after you have killed the primer BY FIRING IT, carefully re-seat the bullet in the cartridge case to its original depth, secured with a drop of epoxy or crazy glue. Make sure the bullet went in straight, without burring the case mouth or bulging the case wall. (If it did not, it will not make a good dummy; throw it away and start over.)

Finally, hold the cartridge in a V-block and drill a 1/8" or 3/16" hole through the side of the case; drill carefully and gently so as not to distort the case with drill pressure (the previously seated bullet will help). Deburr the hole. The hole instantly distinguishes the dummy from live ammo or a dud.

There. You now have one dummy. For a semi-auto pistol, two should be enough to replicate most malfunctions, one feeding and one in the mag directly below.

M
 
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#4 ·
The idea is to replicate as closely as possible the ammo that you shoot with. Unless that ammo has painted bullets, I would not trust paint. The coating adds something to the diameter of the bullet, and --more important--changes its surface texture (as against the feed ramp or against the front wall of the magazine, let's say). Also paint comes off with handling and after a while it becomes difficult to distinguish the dummy from a live round without close examination.

A hole drilled in the case takes care of all that.

M
 
#5 ·
Just wondering - is it OK to dry-fire your pistol with such dummies? I don't believe in snap-caps because their dimensions are imprecise and they're usually made of plastic which will quickly fail under the grip of the extractor. A fired casing will have a peen in the primer which will allow the firing pin to move that much more forward. Is that a bad thing?

I never, ever dry-fire any of my pistols except my Ruger MKII (it's OK to dry-fire that gun and beside it's the only way to de-cock it.) But for the sake of conversation, would it be safe to dry fire on one of these types of dummy shells?

-Pilotsteve
 
#7 · (Edited)
Steve: Sorry, I just saw your question, to which there is no single answer.

The whole point of a snap cap is to cushion the fall of the firing pin, which --if no cartridge at all is in the chamber-- will eventually halt by impacting something else. After a few impacts from the firing pin, a spent primer is permanently deformed and has very little, if any, cushioning capability left. Whether the firing pin is then stopping against that primer or against some part of its mechanism (which is best avoided) depends entirely on the type and design of the firing pin. Either way, it may be beneficial to punch out the primer and substitute a small disc of rubber or a drop of silicone caulk.

Rimfires present a different problem because it's almost impossible to avoid steel-on-steel contact when dry firing them. With semi-autos I have used two methods, depending on how convenient it is. The first is to slightly retract the bolt or slide, but not enough to trip the disconnector, and pull the trigger; that cushions the forward impact of the hammer or striker. The other is to momentarily insert a thin piece of plastic (a bread-bag seal works) between the slide and the barrel, and let the firing pin fall on that.

M
 
#9 ·
I work for a custom rifle maker. You can dry fire any modern center fire pistol or rifle with no worries. The firing pin will hit it's internal stop every time you fire a weapon. The pin protrudes just enough to detonate the primer. If one relied on the primer to stop the movement of the pin, you would have a pierced primer every time. The exact reason for having a dimensional spec for firing pin protrusion from the breach face (varies slightly weapon to weapon).
 
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#11 ·
I needed a quantity of dummy rounds for work and none of the usual suspects had any available. I took a box of factory ammo, pulled the bullets, dumped the powder, fired the primer and deprimed.

Then I reseated the bullets to factory spec and drilled the flash hole out. I obtained some bright orange paint from an auto paint store, some slow (45 minute) setting epoxy from a hobby store and a syringe from the vet. I set the casings bullet down in a loading block, mixed several CCs of the epoxy with a couple drops of the paint, sucked it up in the syringe and injected it into the case thru the primer pocket, filling till it was even with the base of the case.

Voila! Dummy rounds that resist bullet set back and have a soft material that cushions the firing pin. The red "primers" are clearly visible but these can be used for "ball and dummy" drills while training.
 
#16 ·
That's a fair question.

Snap caps are basically just good for dry fire practice. They are rarely, if ever, a precise duplicate of any particular cartridge, let alone the particular brand and bullet shape you are using. Real ammunition itself varies considerably from one brand and style to another.

Dummy cartridges, on the other hand, can be used for function-testing and diagnosis. If you make them from the same type cartridges that you shoot, the dummies will exactly duplicate their weight and dimensions-- in particular the more subtle differences such as bullet ogive, extractor groove depth, etc.

M
 
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