Cold Ammo

[gerritm]

Tuned my 3-gun AR with adjustable gas key with cheap standard velocity ammo at 75-80 degrees so that it would lock back and then gave it a 1/2 turn more to make sure it would run.

 

Shot local 3-gun match Saturday and it ran like a top with Federal AE @ about 40-50 degrees. Gun has never had an issue in all temps down to about 30. I know not really cold compared to up north.

 

We are re-barreling my son's rifle, so for the match Sunday he borrows it. He is first up first stage, shooting my rifle with his ammo. Now we have shot several hundred rounds of this ammo before thru both our rifles with no problems during warmer weather. Shoots well, very accurate. Smaller supplier. Reman type. We use it for hoser & paper stages. Today temp is between 30-40 degrees. First shot single shot, racks next one in single, tries one more time, single, will not cycle. Dumps it and finishes with pistol and tanks the stage.

 

Course I get the what the heck look. Took the gun to an empty bay, tested it with my Federal and all good. Shot that rest of match. Check your ammo in all temps or don't buy it cause it is cheap.

 

gerritm

 

 

[flynbenny]

Shot a multigun match that was partially at night last month, I bailed after my hands went numb shooting a stage. It was very cold all day, and got worse at night (surprise!). Quite a few rifles turned into straight pulls instead of semi-autos. A few pistols did it too, and a handful of shotguns.

 

I have looked at ammo velocity numbers with a big temperature delta, not sure it's enough to make most guns stop running (edit: unless the ammo was loaded exceptionally soft).

 

So that makes me wonder if the lubricants a lot of people are using are too temperature sensitive, as in the viscosity increases when the ambient temperature goes down. That extra drag coupled with a little less "oomph" from the cartridge might be enough to add up to cause a malfunction.

 

The product I use is supposed to be good from -65 C to 230 C, I've had no issues with any of my guns even in very cold weather, or a gun that has been sitting overnight in cold car. 

Edited January 16, 2018 by flynbenny

[Steve RA]

So, what product do you use ??

[flynbenny]

Mil-Comm TW25B, I started when I used to shoot Sigs years ago and that is what they were suggesting I use. Never had an issue with it except the cost. Prior to that I used Rem Oil or whatever light oil/grease I had laying around.

 

I saw a version of it being used in aircraft cannon at my job. I didn't know about using it in small arms until the Sig rep handed me a syringe of it.

[flynbenny]

I didn't mean to hijack the OP's thread with lubricants, just suggesting that as an additional problem when dealing with cold temps.

 

No doubt certain powders are more sensitive to it than others, noticed several comments about that in reading some threads on load development. When someone has sat down and tested it though, they usually get a pretty small change over the chronograph, anecdotally 40-80 fps seems to be normal.

 

My general knowledge of chemistry and physics (Electrical Engineer not Chemical) makes me also wonder if certain primer compounds may be less energetic in cold.

 

I am still mining the search function here and at some other sites, but I feel like some better testing may be in order. It just stinks that there are so many variables in ammunition, makes doing a very thorough test quite challenging.

[gerritm]

After sending an email to the manufacturer, he responded with a phone call. Admitted they load their ammo at a lower FPS than some commercial loads, but got into the we have shot it in all temps and their engineers said there would have to be a large temp difference for it not to work. All kinds of excuses.

 

Understand  how my gas system was tuned with cheap .223 ammo so it would run with just about anything. Have shot lots of different ammo in all temps down to roughly 25 degrees with no problem. It is a small company that made the ammo. I just explained to him politely that his ammo didn't work and Federal along with several others we tried did. 

 

Did check the gas key and it was still solidly loctited with the jam set screw still in place, so no movement.

 

I will save ti for warmer weather.

 

As far as lubricant. Never use any grease, only use Mobil 1 & CLP. Run the gun wet.

 

gerritm

[flynbenny]

Did they say what powder they used, and around how much or how many FPS?

 

That is a good lube combo, Safariland's stated temperature range for CLP is -53 C to around 245 C, the range Mobil claims for 5W30 is very close to that too. 

 

I am going to run a test on some ammo over the next couple months to find out how temperature effects ammunition. I needed a project for my probability and statistics class this semester, professor gave me his approval on it today. I'll probably end up doing it with a pistol,  I would do it with a rifle but my only .223 is a bolt gun and I don't have glass for it at the moment, and the stock is still being made. Perhaps I can test that in the fall. 

 

I will start another thread here in Enos-verse asking for people to tell me what powders they suspect are most and least sensitive to temperature extremes.

[gerritm]

They said around 2600 -- 2700 FPS and would not say what powder. Claimed it was not temp sensitive.

 

Would be an interesting thread especially with the global warming going on thru the country right now.

 

 

gerritm

[flynbenny]

My research from searching this forum and some others yesterday indicates all powder but especially rifle powder is temp sensitive. Some quite a bit and others hardly at all. 

 

N320 seems to be the least sensitive pistol powder, and Varget is the least sensitive rifle powder in wide use.

 

What bullet weight was the rifle load? If much under 77 grains 2600-2700 is a bit slow.

[gerritm]

55 gr.

 

The 75-77gr we use for long range chronoed at around 2700fps. More concerned with long range for Strelok calculations.

 

It has been awhile since I chronoed our hoser rifles loads. Been running that rifle for several years with no issues. Just started lately with this ammo and cooler weather. I blamed the mags, bought some new ones. Still had problems. Never thought about the ammo until it got cold by our standards and would not cycle. 

 

JP lite BCG, RCA gas key, with JP captured buffer in a Seekins billet upper and lower with a Faxon 16" mid gas barrel. 

 

gerritm

[MikeBurgess]

Something else to keep in mind with tuned gas systems. not all ammo, even if it has the same muzzle velocity, has the same pressure at the gas port, every powder will have a different pressure curve and will operate the action differently.