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Posted: 8/31/2026 9:53:32 AM EDT
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I'm putting together a truck gun setup. What my question is. I live in the south with high humidity and big temperature swings. When leaving loaded magazines with my truck gun what can I expect time wise before I will start having reliability issues with the ammo. I'm thinking of using the Black Hills water resistant 50gr Barnes tsx as I believe that it will hold up better to the high humidity here? For those of you who do have a truck gun with loaded magazines. How often do you just go ahead and shoot that ammo, and then replace it with new ammo? |
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OP: You are WAY over thinking this. The ammo will be fine, I had a truck gun for a decade? or so. Never an issue- it all went bang. I'm not sure if I ever replaced all of it, I would shoot a group every now again to confirm zero. But since you are worried about it, visually check it every few months. |
| Earlier this summer, I discovered a 20 round AR mag behind the back seat of my 04 F350. I put it there in Jan of 04 and forgot about it until I found it this last July. It was loaded with 19 rounds of HANDLOADED .223. I shot the ammo agains the massed formations of prairie dogs infiltrating my south west pasture. All fired and functioned as normal. As far as accuracy goes, they were at least minute of prairie dog. |
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Originally Posted By fxntime: You'll probably die of old age before the ammo goes bad. This, I had old ammo rolling around in my patrol car for years. All summer approaching, sometimes near 100° outdoors so certainly well over in the car. Then all winter sometimes approaching -30. Even the pistol ammo that was on my belt that got rained on, splashed on, and sometimes dunked in a stream or river all went bang. Although any ammo that actually got dunked got replaced for duty. The dunked ammo then shot for training with zero failures. I once lost a .260 reload out of my stock cheekpad’s loops and it sat in the snow and rain until I saw it laying in the trail the next season. It was right in the area that stayed flooded for several days at a time after storms. Lord knows how many storms it sat through submerged. No primer sealant, H4350 in a RP case with a Sierra 140 Game king, no bullet sealant. I shot that round as a fouler on my next sight in. It was in the group with all the others with no difference in velocity beyond the usual span. Would I recommend that? of course not. My biggest worry with car ammo storage is how hot the ammo is at the time of firing and more importantly is the barrel already hot from car storage. That barrel heat has more effect than the cartridge heat from real testing. The only blown primers I had in an AR were a load I made for a rifle then used in my carbine in a stupid hot and humid day in the sun. CCI400 with BLC2. A combo that isn’t that good for baking in the sun. BLC2 is temp sensitive. |
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My ammo's always been good reguardless of time carried. but out of habit I replace the ammo in my edc/mags every 3 or 4 months. My truck gun ammo/mags/bag goes into house with me at end of day, I'll rotate ammo out once or twice a year. All ammo that gets rotated out goes into the practice ammo can. |
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Originally Posted By fulautotank: I'm putting together a truck gun setup. What my question is. I live in the south with high humidity and big temperature swings. When leaving loaded magazines with my truck gun what can I expect time wise before I will start having reliability issues with the ammo. I'm thinking of using the Black Hills water resistant 50gr Barnes tsx as I believe that it will hold up better to the high humidity here? For those of you who do have a truck gun with loaded magazines. How often do you just go ahead and shoot that ammo, and then replace it with new ammo? My wife carries a 45 acp with Barnes 185gr copper hp's. I am carrying a 9mm with hornady critical duty 135gr hp's. Both have sealed primers and nickle cases. I normally replace the ammo yearly and shoot the old ammo. Haven't had the old ammo malfunction yet. My rifle is loaded with Barnes 62 gr. Txs with nickle cases. I live in E TX. It's high humidity and heat normally from April thru September. No malfunctions thus far. Heat does tend to make powder deteriorate over time. I don't know a time frame for that. You might contact the manufacturer of the ammo you are going to use and see if they might have that information. |
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Originally Posted By fulautotank: Well, I guess I won't worry about it too much. It's good to know that it won't really effect the ammo much, if at all. I will periodically check it by firing some it just be be safe though. Thanks for the replies. Supposedly some of the 50cal ammo for the GWOT was made in WW2. |
| Been in LE for 27 years. Been carrying some rifle and pistol ammo in the back of a police vehicle for years. Now I cycle through it but it goes bang all the time. I also have loaded spare mags that I rotate every five years. It always goes bang. Like another has said. You're over thinking it. It will be fine. |
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Originally Posted By trails-end: I have wondered how that military surplus ammo we used to buy was stored before we got it. I doubt it was kept in a climate controlled warehouse. Attached File Actually, it was… well, kept in climate controlled (NOT AC) earthen concrete magazines and regularly inspected until such time as it was surplused…. That said any well mfg’ed ammo w/o signs of moisture damage such as corrosion should be good to go INDEF within a few human lifespans… the biggest issue with carry ammo is setback if repeatedly chambering the same round and corrosion from sweat. I just shoot what I carry first when I go to the range and reload before I leave the range and it takes care of both. |
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