Ker-Plunk Vs. Whoosh


The effect of bullet push-back due to improper feed angle. This raises pressures to dangerous levels.

For the custom pistolsmith it’s not always about cosmetics, the pistol has to function and be accurate. Function is kind of “job one” in my shop. If it doesn’t run it just won’t do.

Recently a client was in the shop for some new sights and spied a project I was working on the “Caliber Project” — more on that later. On the bench was a .30 Luger barreled 1911 Colt. He said this was his favorite caliber and wanted one. He had a 9mm Colt that would be the basis for the conversion; a 9mm breech face is the same as the bottlenecked .30 Luger.

I ordered a 5″ .30 Luger barrel from Bar-Sto Barrels, who had made the Commander-length barrel I was already using. I ordered it semi-fit, meaning the chamber is close to final cut. This allowed me to fit hood length and width and the lower lugs of the barrel, then finish ream the barrel with my Clymer reamer.

Now comes the fun part. Since this Colt 9mm frame was fitted with a conventional barrel (non-ramped), the Bar-Sto was made the same so the owner could swap back and forth. Function testing starts on the workbench. One note of caution, in my shop we never bench test with live ammo in a working gun. I usually have a number of non-primed, powerless cases for testing on the bench, but in this case I did not so I removed the firing pin from the pistol. This allows me to test feeding without the risk of firing a shot inside.

A new slide holding fixture from HS-Custom (red arrow) allowing full access to the slide for hand work.

Funny Sounds

The first test is just to see if the rounds will feed. The owner supplied a pair of magazines from an unknown maker. In a 1911 the rounds have a distinctive “whoosh” when being stripped from the magazine during feeding into the chamber. The first rounds fed in this case, have a two-part “ker-plunk” indicative of the bullet nose skipping off the feed ramp then into the barrel chamber. Not what we want. Hitting the feed ramp or barrel ramp can cause malfunctions and in some cases dangerous ammo issues — which it did in this case.

The bullet nose hit the ramp hard and the bullet pushed back into the cartridge case about 0.080″. This results in a “compression load” for the round, increasing pressure, and could result in a ruptured case during firing.

There are a number of causes for “bullet skip” so I need to find the cause and a correction. One trick I do to see where the bullet nose is impacting the ramp is to coat a number of rounds with layout fluid. The fluid is like a temporary paint used in machining. As the coated rounds are stripped from the magazine on chambering, the blue coating rubs off the nose of the bullet, leaving a trace on the area it impacted. Now I can see the spot the bullet is skipping off of.

In this case it was the barrel throat area, about midway up from the bottom of the barrel. On this barrel the ramp has a very steep angle, allowing more case support on the necked cartridge. I really don’t want to modify that too much. The next thing to check was the magazine feed angle. Is it too low to allow for proper feeding? In my shop I supply Tripp or Wilson magazines with custom builds so I next tried one of them. Still hitting a little low. Next test was the actual position of the magazine. I noticed, when seated, the magazines were a little loose and had some vertical movement. I measured the movement and they had about 0.070″ of vertical play. This was almost identical to the amount the bullet nose was hitting low on the barrel throat.

Layout fluid provides evidence of the area a bullet impacts on feeding — in this case too low.


To solve this, Evolution Gun Works (EGW) offers a 1911 mag catch seating magazines higher. As the magazine is seated higher it allows the bullet to enter the barrel without impacting the barrel ramp too low. Now the rounds feed smoothly and I’m ready for live firing at the range. Almost victory!
Speaking of victory, Dustin Housel of HS-Custom has come up with a great slide fixture. It makes handwork on a slide much easier. The jig holds the slide from the muzzle end and locks it securely with two setscrews. The long shaft is faceted to hold the slide in a number of angles in a vise, with full access to all sides of the slide. I used it and realized it saved a lot of clamping and adjusting of the slide — the way I’d been doing it for years. Thanks, Dusty!

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