What Causes Light Primer Strikes?

posted on October 30, 2021

Light primer strikes aren’t always indicative of faulty ammunition. Judicious troubleshooting should be applied to the gun and multiple types of ammo to isolate the culprit.

My SIG Sauer P365 has been my constant companion as my everyday carry gun up until recently. The reason is it doesn’t go bang every time I pull the trigger. I bought some frangible factory practice ammunition at a good price (by today’s standards) a few weeks back and the performance with that ammunition has me baffled. One or two rounds per magazine don’t fire because of what I perceive as light hits on the primer. The fired cartridges all seem normal as far as I can tell, but I never know when the gun will fire and when it won’t. Needless to say, I have lost confidence in the P365 and have started carrying a revolver for everyday carry because I know it will work when I need it to.

What do you suggest I do to help regain my confidence in the P365 so I can comfortably carry it once again?
Walt Aoki,Portland, OR

There are quite a few possibilities that could be causing the problem you experience. Some can be gun related and others can be ammunition related. The primary concern is to restore confidence in your P365.

I would start by isolating the problem within a reasonable doubt to either the ammunition or the firearm. If the problem persists with multiple types and brands of ammunition, I would focus my efforts on the gun. If only one brand or type of ammunition is giving you problems, changing ammunition is the obvious answer.

Often, field stripping, cleaning and lubricating according to the owner’s manual eliminates a variety of firing failures in any firearm. Ensure the chamber of the barrel and the breechface, especially under the hook of the extractor are free of any firing residue. If possible, remove the striker from the slide and clean its working area to ensure it can move through its range of motion without restriction. Lubricate all surfaces experiencing friction as evidenced by the wear patterns. Use a quality lubricant and apply before reassembly, verifying its presence visually and by touch. Perform a function check to ensure the moving parts are operating smoothly and to prove the gun is mechanically sound. It’s a good idea to perform this procedure regularly, as it will build confidence and familiarity with the gun and how it works.

Once the gun passes the function check, test fire it for function with several different types of ammunition. If the problem persists with more than one type or brand of ammunition, I would recommend contacting the factory’s customer service department for consultation, return and evaluation. Some-times it is good for confidence and peace of mind to let the professionals look it over and declare it fully functional.

Frangible ammunition will usually function fine if manufactured to SAAMI specifications. It has improved in quality dramatically since becoming popular for training during the last 25 years.

Some early-manufacture ammunition had standard lead-styphnate primers, while others were fitted with lead and heavy metal-free primers. Some of the lead-free variants had sensitivity issues in that they failed to initiate with good, solid strikes. Others were susceptible to moisture, which limited shelf life. And, some had bullet shapes that would not allow the cartridge to fully seat in the chamber, which in several ways affected the ability of the gun to fire the cartridge. The learning curve was rather steep, but today’s frangible ammunition should work in any gun that is capable of firing ammunition manufactured to SAAMI, CIP or NATO specifications.

It sounds as if your ammunition may have been some of the older generation, hence the good price that you mentioned. Keep in mind that where ammunition is concerned, you usually get what you pay for.

If your P365 functions without failure when firing your everyday carry ammunition, I see no reason not to elevate it to your constant-carry companion again.


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