Home Forums Hunting & Shooting AR and Tactical Rifles AR bolt sticks in cold weather

Thought maybe some of you could help me with malfunctions that sometimes crop up with my AR (technically, an Olympic Arms UMAR in .22-250) in cold (20F and below) weather. It sometimes fails to completely feed a follow-up round, but the last time I went out (15F), the BCG locked back after the first shot and I had to hit the mag release.

I don’t think ammo’s an issue, because they check out fine in my case gauge, plus shells fall into the chamber fine if I point the rifle barrel down and drop them in.

Freeze-up due to condensation isn’t an issue because I keep the rifle in an unheated garage and it rides in the back of a truck on the way to the field.
Someone said to lube with FP-10 because it’s rated to -49F, but the problem still persisted, so I wiped down the bolt and inside of the upper and now run everything “dry.” (Because I only shoot the rifle a few dozen times a year, I’ve been told that “running it dry” won’t be a problem.)

Have any of you dealt with this issue? Anyone can chime in, of course, but I’d especially like to hear from those who hunt in seriously cold climates. (Sometime it gets down to -40F here.)

Don't run these dry, that can definitely cause issues. You'll need to figure out an oil that works in the temps you're shooting in.

Also, you won't get a lot of positive feedback on an Olympic Arms; it's likely that at least part of your issues are due to something out of spec and poorly made.

I hunt in the same weather you do. I only oil the gas rings and put a thin coat of grease on the bottom of the bolt where it slides over the hammer. I do not oil any other part. I do take the bolt apart and keep it clean every now and then. I have not had a single issue this way in 20 years of using ar15s.

How much oil or grease is on your buffer tube ?? Something is slowing the speed of the BCG down. A friend over greased the spring in the buffer tube and when it was cold it really slowed the speed of the buffer down. He was using grease to reduce the sound of the spring in the tube. Another issue might be the powder you are using. Is it cold sensitive and delivers less performance ?

kwg

Actually, other than very light, high quality oil, on the carrier, trigger, and buffer spring, I don’t run much of anything....even then, they’re almost completely ‘dry’. .....stuff sticking to wet oil causes more issues (IME) than most things. Coldest I ever ran one was single digits to zero. Militec dry film or eezox on the trigger/carrier, generally keeps them going for low volume, hunting purposes. There’s hunting AR use, then there’s M4 uses.....different requirements.

This.

As for it not being ammo, you loose pressure in cold weather. This is especially true for older ball powders such as H335, Bl(c)2, and W748, which are all common powders for AR's.

Thanks for the feedback, gents!

Powder is Varget (36 grains under 55-grain Ballistic Tips).

As far a the buffer tube, I haven't touched it in the three years I've owned the rifle (bought it new). Only 200 rounds in that time.

I've always been a bolt gunner before getting into ARs a few years ago, so a lot of this is new to me. Any suggestions as to fixing possible buffer tube issues? (Take it apart and clean/lube, or what?)

FWIW yesterday I scrubbed everything with Q-Tips and wiped down with a VERY light film of FP-10 and left it outside overnight. Awoke to -2F weather and manually cycled five shells with no hang-ups. It's supposed to stay around zero for the next few days, so I'll head to the range soon and see how the UMAR performs.

Question Gentlemen. Can you use CLP or Hornady one shot for the AR? I used it in mine and had no problems in cold weather.

CLP was made for the AR.

Then I doubt that's your problem. Vargets on the temp stable side, but you will still get some variance.

Since it's been a while, and you haven't shot it much, I'd do a quick check of your gas system to make sure everything is tight and properly aligned, especially the gas block.

I will give you the "Readers Digest" version, rather than write out the dissertation.

Go to the auto store and get some 0W-20 motor oil.

Clean all the other stuff of your bolt carrier group, and lightly lube with the 0W-20, or equivalent. You will be good to go. I have run my ARs in 20 below using this, along with bolt guns to mid -30s.

If you haven't taken the spring and buffer out of the tube now would be the time to pull it out and look it over. If it's greasy or gritty clean it and only some light oil back in.

kwg

Might want to check you buffer retaining pin as this was happening to my AR off and on. Noticed it when it happened and took it apart carefully and saw the pin dragging on the bottom of the bolt.

I got this tip from a member of the local sheriff’s sniper team. He says he needs his AR to function at seriously sub-zero temps, and this works for him:

http://www.slip2000.com/slip2000_ewl.php

I ran Eezox down to -30's with no problems when living in AK. It probably would have been good with even colder temps, but my fingers weren't.

I am using automatic trans fluid in my ARs 223s ,6.8s and 308. No problems at any temp so far.

(yeah it does get cold here doesn't it!?)

Pull it down and disassemble bolt and clean carbon out. Lube with Ed's Red (make;it yourself)

Get a 2 gal plastic gas can: Mix as follows:
1/3rd Mercon Dexron Transmission Fluid
1/3rd K1 Kerosene
1/3rd Mineral Spirits (paint thinner).

This should take you to about 50 below zero.

I was a Small Arms and Ammo Test Director at Aberdeen Proving Ground and we found CLP gummed up at about 20 below zero. We tested at 60 below.

For general overall use I use Mobil 1 above.

You may have to soak the bolt and carrier in ER to loosen up carbon deposit on bolt.

UNDER NO CIRCUMSTANCES USE GRAPHITE ! ! !

Amsoil cleanse and oil. It smells great and it’s a great lubricant. I had the same issue with my 7.62x39 AR. Haven’t since.

UNDER NO CIRCUMSTANCES USE GRAPHITE ! ! !

Curious what is the issue with graphite???

It's an Olympic Arms.....I found the issue.