Overgassing in hot weather temperatures?

[ta0117]

When I competed in High Power, increased temperatures raised the POI significantly for me at 600 yards. When I reloaded with Varget, I noticed temperature had less affect on POI shift. In temperatures above 80 degrees, I kept my ammunition and loaded magazines in a cooler with a towel draped over it.

I shot my carbine this afternoon with Federal M193 and iron sights. The temperature was 90 degrees at the range and the POI was 1-1/4" higher at 100 yards than the entry in my logbook on a 40 degree day. From 0 degrees to 104 degrees I have not noticed any reliability issues. That is why I asked the OP if he was concerned about reliability or accuracy.

I re-zeroed my optic just a month ago, so I can't tell you if there was a POI shift from cold weather shooting. There isn't reliability issue right now, but I still don't like how my rifle has sharper bounce even though on paper it shouldn't, especially compared to a friend's rifle with a larger gas port and lighter buffer. He hasn't had issue with reliability in hot or cold weather either. There's also the issue of premature parts wear from potential overgassing.

[T2C]

I re-zeroed my optic just a month ago, so I can't tell you if there was a POI shift from cold weather shooting. There isn't reliability issue right now, but I still don't like how my rifle has sharper bounce even though on paper it shouldn't, especially compared to a friend's rifle with a larger gas port and lighter buffer. He hasn't had issue with reliability in hot or cold weather either. There's also the issue of premature parts wear from potential overgassing.

It does not hurt to keep a simple rifle log. A small spiral notebook or steno pad would be good enough. POI shifts at different temperatures, say 40 degrees and 90 degrees would be valuable information. You can also keep track of sight adjustments made when switching between brands of ammunition and different bullet weights. You don't have to keep meticulous records like a High Power competition shooter, but collecting and keeping good information can save you a lot of time in the future.

[ta0117]

I’ll note that the stuff I stocked up and shoot isn’t anything special, just Wolf Gold M193.

[Spooky1]

It does not hurt to keep a simple rifle log. A small spiral notebook or steno pad would be good enough. POI shifts at different temperatures, say 40 degrees and 90 degrees would be valuable information. You can also keep track of sight adjustments made when switching between brands of ammunition and different bullet weights. You don't have to keep meticulous records like a High Power competition shooter, but collecting and keeping good information can save you a lot of time in the future.

I second this ^^^^^^^

Notes have saved me some time and a bit of $ on ammo over 23 years.

[opngrnd]

I second this ^^^^^^^

Notes have saved me some time and a bit of $ on ammo over 23 years.

^what they said. Even the basics, like general round counts and when you did maintenance is great to know.

[mRad]

I think you’re probably over-concerned about “feel”.

Muzzle devices the same?

Ammo the same?

Was his a home build? Perhaps some gas block misalignment?


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[MistWolf]

I’ll try to install a H2 buffer to see what happens. I wasn’t aware that powders can be so temperature sensitive.

I must say I’m surprised that this DDM4 feels overgassed. It’s a V9, so it has 16” barrel with midlength gas system and 0.073” gas port according to DD, and H buffer. This is actually a bit smaller than the standard 0.076” midlength gas port on BCM and the likes, but when firing 5.56 ammo, it’s got a pretty solid kick, not unmanageable but noticeably more than my friend’s rifle firing the same ammo when I shot this weekend. His upper has a BA barrel with 0.078” gas port, and he’s using a carbine buffer. And his gun ejects at consistent 3 o’clock, while mine is 2 o’clock.

I’m pretty baffled, to tell you the truth. On paper my rifle should shoot softer, but it doesn’t, and feels overpassed.

EDIT: Just to clarify, his barrel is also 16" like mine.

A couple of observations-
-What a maker claims a port diameter to be and what it actually measures out to be don’t always match.
-A buffer that’s too light will give sharper recoil and the AR will feel like it’s over gassed. Recoil with an H buffer should not feel real sharp. However, do try the H2.
-Recoil with a weak action spring will feel the same way.
-The 2 o’clock ejection angle does not indicate the AR is over gassed. It indicates the extractor spring is failing and needs to be replaced. Install a new Colt extractor spring. No O ring.

[ta0117]

A couple of observations-
-What a maker claims a port diameter to be and what it actually measures out to be don’t always match.
-A buffer that’s too light will give sharper recoil and the AR will feel like it’s over gassed. Recoil with an H buffer should not feel real sharp. However, do try the H2.
-Recoil with a weak action spring will feel the same way.
-The 2 o’clock ejection angle does not indicate the AR is over gassed. It indicates the extractor spring is failing and needs to be replaced. Install a new Colt extractor spring. No O ring.

I don't think the extractor spring is failing, it's still throwing brass a good distance away, enough to annoy nearby shooters. I can check the spring too, but I don't think any part should be worn out yet, I'm not yet at 1,500 rounds.

[1168]

Military M4’s, including brand new ones, will commonly yeet brass to the 2 o’ clock on a nice warm day, so that is indicative of….. nothing at all.

People mess with buffers entirely too much, in my opinion, and seem to expect that life changing results will occur with every .8 oz increment. Sometimes such a change is noticeable, sometimes it isn’t.

A log is a good thing to do. Ammo is, in fact, temp sensitive.

[ta0117]

I think you’re probably over-concerned about “feel”.

Muzzle devices the same?

Ammo the same?

Was his a home build? Perhaps some gas block misalignment?


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His is a BA 16" midlength upper with an Aero BCG and Spikes lower. We both have flash hider muzzle devices. Normally I know "feel" can be subjective but I shot these rifles back to back and the difference was noticeable.