Monday, January 18, 2021

Pro-tip of the day

Permatex 81730 sealer flows well when the nozzle is cut small and the sealer is applied to one side of the cavity to allow the air a path to flow out. Over-flow peels off easily.

Elastomer tipped bullets are all the fashion in some circles.

Ballistic engineers figured that one work-around for the standard FBI test involving four layers of denim involves pre-filling the hollowpoint with a soft, rubbery material.

The problem with denim (and cardboard) is that it packs into the hollowpoint on impact. When compressed from the tip, the column of fibrous material does not bulge outward.

We are all familiar with how rubber bands get thinner when they are stretched. Rubber cylinders or plugs also get thicker as they are compressed. For the amount of strain involved, the volume of the rubber shape does not change and the rubber behaves much like hydraulic fluid when trapped.

Consequently, when a hollowpoint bullet has the hollow filled with a rubbery material (but not foam rubber), then when the bullet hits a target the bulging rubber plug exerts outward forces on the sides of the hollow and assist in the initiation of the expansion.

And while I would never encourage anybody to experiment, I will note that a flowable, soft, rubbery sealer might make an acceptable substitute. Further, I might note that the 3mm diameter by 6mm deep hole shown on these Zero 158 grain, genuine pewter medallions would only add about 0.8 grains of mass and a 1.5 ounce tube would be sufficient for over 800 such bullets.


  1. Science experiment!

    I have a half-finished similar experiment- use a small lathe to drill an HP cavity into the front end of a 158 LSWC cast bullet. Homemade hollowpoints!
    I doubt they work as well as other projectiles but it's a start.

  2. When I read this it reminded me of a story told by a non blood relative who happens to be a bit of a "gun guy". Someone asked him a question regarding 9mm. As the story goes this person had bought a small amount of ammo but most of it was fmj. There was an even smaller amount of hollow point (well less than 10% of total) which prompted this person to ask if they had screwed up. My semi-relative said that was no problem. Because of circumstances beyond my control I didn't get to ask exactly why it was ok. I was unable to ask if that was because he thought the mix was alright(practice vs practical)or if he planned to "modify" the fmj for him,or if the threat of getting shot was deterrent enough, or if he thought the person was just so inept that they would be toast at the end of the day if push came to... It didn't seem that drilling a hole would solve the problem until you told this story. But now I wonder if this is what he had in mind.

    1. The tough thing about drilling hollowpoints is that the bullets go flying off in unpredictable directions if the hole is not on-center. There is also the issue of how do you clamp the case without distorting it.

      My guess is that he was going to have the new guy use the FMJ for practice.

    2. To show how little I know,in my head I saw a cast or drilled aluminum or wood block the size of the drill press table that could be clamped(quick clamp) that had a hole in it the same diameter as the case. Lift it up place the cartridge in clamp it down. Starting real small and shallow do each, then when done with a batch increase the diameter of the bit. Enough of the top of the cartridge would protrude through the template to allow you to use mechanics gloves to keep the cartridge from spinning as you drill. That's how I saw it in my head, but I use the handle that I do for a darn good reason.

    3. A standard 5C collet in a lathe would hold the round sufficiently without undue brass distortion. That being said, not sure using modified rounds for self defense would be a wise route to go, should one find themselves in court.

    4. In the mid '60s surplus 30-06 was really cheap so I and a couple buddies would buy it and make hollow points. Make a clamp from oak slightly thinner than the overall length of the cartridge, drilling from the bottom with a drill the size of the case up to near the top then finish with a drill the size of the bullet. Plane the clamp so that about 3/8s inch [can't remember exactly] of the bullet tip is sticking out. Carefully grind and finish file the point down to the clamp so they are all exactly the same length. Then in a drill press drill the bullet with the press set for depth. It worked quite well and we shot several deer and varmints with them. ---ken

  3. Great information as always, thanks!

  4. If this were 2019 I'd say just buy a bunch of Hornady Critical Duty rounds. I don't know if they make just the bullets. That's what they were designed for. Today, I'm in total conservation mode.


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