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Cold Weather Trials

MP7A1 LM4 KM4A1 GBB AEG

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#1 Chuck S

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Posted 06 January 2013 - 11:26 AM

As we all know, gas guns don't like cold weather!  Just ran some simple non-scientific tests on my gas guns in 30°F North Coast weather.

The guns:
KWA MP7A1
KWA LM4-PTR
KWA KM4-CQB  Yeah, I threw an AEG into the mix because it was handy.

I cold-soaked all the guns, BBs, magazines, etc for several hours outdoors on my back porch.  Gas was topped off before shooting.

The gas guns were painful to watch and hear as they choked and struggled.  Cold soaked I rate both the GBBs as unserviceable.  The AEG was much better.

The MP7A1 struggled to load and fire and chronographed at about 250fps (0.25gr BBs) when she did shoot.  Pretty consistent muzzle velocity but she didn't get thru 20 rounds before completely shutting down and venting the remaining gas.  This gun shoots in the 400fps+ range (with 0.20gr BBs) in normal conditions so she was down at least 100fps from normal.

The LM4 was only a little better as she struggled valiantly to get thru a magazine finally choking on AUTO and venting all the gas before the mag was empty.  Muzzle velocity dropped from the 390fps + range to under 350fps (both chronographed with 0.32gr BBs).  Still useable velocity but she was unable to get thru a magazine.

Since I had the AEG handy I tested here too.  A little sluggish and the muzzle velocity was 90fps slower but increased as the gun warmed up.  The heavy gearbox grease was no doubt slowing the operation.  This was with a fresh 7.4v LiPO that was cold soaked in the gun.  I'll retest this gun later  with a fresh 11.1v LiPO.  While the velocity was in the 250fps range (rather than 340+) she was still hitting the little steel targets I keep in the back ground.

I edited this as I was accidentally mixing my muzzle velocity for 0.20 and 0.28 BBs.  :(  The AEG shot about 250 fps with the 7.4v battery earlier today and 270fps a few minutes ago with the 11.1v.  I also fired a magazine of BBs to warm the gear box in the second, higher voltage trial so the two MVs are NOT directly comparable.  No time for more scientific results but the AEG seems to run pretty close to normal once the gearbox warms up a little.

Simple shooting tests.  No playing with the hop up or anything, mainly just function checks.

-- Chuck

Edited by Chuck S, 06 January 2013 - 02:56 PM.


#2 kwaispro727

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Posted 06 January 2013 - 11:52 AM

I'm surprised they even shot to begin with, just because of the compression of the gas.  I actually read about something with the LM4 which I found rather funny but interesting, someone in a more northern part of Alaska bought one.  I don't remember exactly where, not as far as Barrow but close.  They warmed it up inside at about 80-90 degrees and ran outside to shoot it in sub-zero temperatures.  The gun actually managed to get through the whole magazine.  Obviously it wasn't cold enough for the gas to freeze but they were saying how after the first few shots it's just so cold it almost instantly begins to compress.  Definitely a very expensive experiment though lol.  They must play indoors, or June-August.

Edited by kwaispro727, 06 January 2013 - 11:52 AM.


#3 Chuck S

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Posted 06 January 2013 - 02:59 PM

I can step out of my warm family room and chase deer away away from my Dachshunds easily in this same weather with either the MP7A1 or LM4.  I was curious how the guns would perform cold.  They don't!  ;)

But the KM4-CQB seems little effected by the cold after the first few shots.  I'm still searching for my 0.28gr standard temperature data to make a direct comparison.

Chase deer away from dogs?  The dogs are inside an Invisible Fence that the deer ignore.

-- Chuck

#4 Theshank

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Posted 08 January 2013 - 09:33 PM

I talked to a player who keeps hand Warmers in his mag pouch, for cold games and claims it works. ( for reference I'm in CA low temps in the am low 40's ), anyone try this yet?

#5 ATOMANT

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Posted 09 January 2013 - 07:28 AM

I was thinking exactly the same thing. I bought a big box of heat pouches at Costco one time. You just knead the contents of the package and it throws lots of heat. Would be perfect to add to a mag pouch to keep the gas temp up.

#6 kwaispro727

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Posted 09 January 2013 - 03:12 PM

I suppose you could also wedge them in between the pouches with a little tape if there is no room like for an MP7 or pistol mag.

#7 redwingii

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Posted 09 January 2013 - 08:56 PM

First post...

I received my LM4 PTS Magpul in the mail yesterday.  I only have 1 other gun, a KWA M9 PTS, and I like the realistic look, weight, field strip functionality that I had to go and get this one.  Im new, never played a game, I shoot 2l bottles in my back yard for fun.  I got the M9 because Im teaching my 7yr old daughter about gun safety, maintenance, shooting and didn't want to put real steel in her hands yet... after all, she's 6 ( 7 in February ).  I also live in Ann Arbor Michigan, it is cold outside.

Cold is relative,  I think its cold when its 20 deg, my dad, who grew up in MI and now lives in NC, thinks it cold at 50 deg.  If you live in Alaska your taking off your coat at 50 deg.

I have a pole barn with a small 10 x 12 office inside that I heat and cool separate.  Right now my office is a nice warm 75 deg and its 58 deg in the rest of the barn.  I bought 2 brand new cans of green gas last night and ended up leaving one in the office and one outside the office.  I also left the gun and mag in the barn.

I played with it yesterday with the last of the GG I had, ran 3 or 4 clips with no issues.  Thats the only experience I have with the way it feels.  Tonight I went to play some and the first 2 clips ( where the mag was filled yesterday  and I refresh to full after every clip) went fine, things felt like they felt yesterday.  Then on the 3rd I noticed extra smoke (gas) escaping from the ejection port.  Using the cold can I refilled again and the first 2 rounds seemed to kick harder and expel more gas.  The remaining 27 rounds fired evenly, but not as hard as normal and the last one didn't lock the bolt back. I also noticed what appeared to be condensation in the chamber.  I tried again (with the cold can) with pretty much the same result.  Filled it once agin with the brand new cold can.

Then I took the clip into the office, and for S/G I tried the warm can.  It added about %15-20 more gas.  Waited a little while for the mag to warm up and tried again, didn't sound or feel like any more gas went in it.  Then with the warm mag went back out into the barn and on full auto emptied a clip.  Fired just like yesterday but there was still what looked like condensation in the chamber.

Thats my experience but the whole reason I came to the board was to see if I could figure out for sure what that moisture is, Condensation, Propane, Silicon?

My conclusions are that the temperature of the GG is useful above about 67deg (avg 60-75)...

Does anyone have any knowledge of the exact temperature of GG liquid / solid melting / boiling point?

I wonder, the new cold GG can seems to have been used more than the warm one.  Does physically more gas/silicone mixture enter the mag the colder it gets?  Then it just spirts out waste the first two rounds until it equalizes with something?

As I tried to state at the start,  I don't know what Im talking about,  this is just data and guesses..

Edited by redwingii, 09 January 2013 - 09:37 PM.


#8 Chuck S

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Posted 10 January 2013 - 03:53 AM

Clip?  :shocked:  

Sorry, but that word is like fingernails on a chalkboard to me!  :)  

None of these guns have clips, they have magazines!

-- Chuck

#9 kwaispro727

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Posted 10 January 2013 - 03:40 PM

If you think about it logically, yes more gas can be put into the magazine in the cold because it does not expand as much.

#10 Chuck S

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Posted 10 January 2013 - 04:13 PM

Your "logic" is, unfortunately flawed.  :)

We don't put gas in airsoft magazines, we put liquid.  And the magazine will hold the same volume of liquid warm or cold. The surface of that liquid will vaporize a little and that vapor is the gas that drives the BB.  In summer temperatures this happens so fast you can consider it instant.  Shake the propane/green gas cylinder and you can feel the liquid sloshing around.  Same with the LP tank for your BBQ grill.

Propane (green gas) boils (vaporizes) at about -40°F (or -40°C, take your choice).  But it provides little pressure at that temperature and in a pressure vessel like a green gas cylinder or magazine there's little pressure at those temperatures.

As the temperature gets higher the boiling/vaporization is faster and more pressure is created.  No surprise that Gas airsoft guns shoot slow or not at all in cold weather, slow down as they get cold, and shoot "hot" is hot weather.

-- Chuck

#11 kwaispro727

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Posted 11 January 2013 - 04:21 PM

Wow duh lol.  I always forget that it really works that way.

#12 Cpapp

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Posted 19 January 2013 - 07:39 PM

On the 31st, I ran my mp7 with 2 mags and handwarmers in my pouch. It worked and it was 15degrees. Now it could get through a mag, but no more.





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