View Full Version : Overgassing in hot weather temperatures?
Something I'm noticing is that in the spring time and moderate weather, my gun eject at about 3 o'clock or so. However when it's summer and the temperature is in the 90s and my gun was sitting in the sun for a while, my ejection is now closer to 2 o'clock and also "feels" more gassy. I'm shooting the same batch of ammo. Does the temperature have effect on gas pressure and cycle of operation?
vicious_cb
07-18-21, 20:29
Yes, but its your ammo not your gun. Dont leave your ammo sitting out in the sun or in a hot car.
Most ammo is loaded with temperature sensitive powder. Ball powder is notorious for this phenomenon. One thing handloads chase is loads with powder that is temperature insensitive.
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Yes,
Hot powder burns better than cold powder.
It's just the way it works.
Muzzle velocity is also increased with hot ammo.
If you feel like doing something, go up to the next heavier buffer, which will mostly counteract the additional gassing.
I only reload pistol ammo but some powder is inverse temperature sensitive.
I only reload pistol ammo but some powder is inverse temperature sensitive.
You mean it gets milder as the temperature rises?
Yes. There were/are Pistol powders that exhibit this; 452AA was one that was used in the dark ages in IPSC.
The cooler the temp, the higher the velocities.
Rifle powders, unless temperature INsensative, run slower in cold/quicker in hot weather/temps.
I would like to understand the chemical kinetics involved. Is there a technical paper on this?
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwiHmIX274DyAhW9AZ0JHYCeBoo4ChAWMAJ6BAgEEAM&url=https%3A%2F%2Fapps.dtic.mil%2Fsti%2Fpdfs%2FADA590866.pdf&usg=AOvVaw0TyQH05rOG3yWEihG-mCDW
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjE3Pnh7oDyAhWVXc0KHcggDiwQFjAOegQIDRAD&url=https%3A%2F%2Fpdfs.semanticscholar.org%2F9b16%2F998e62b42c545c98d2d04872ed8dca701660.pdf&usg=AOvVaw38fgT1MOTnzDxKJ9Krlqqi
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjE3Pnh7oDyAhWVXc0KHcggDiwQFjAPegQICxAD&url=http%3A%2F%2Fwww.wydawnictwa.ipo.waw.pl%2Fcejem%2FVol-13-Number-4-2016%2FBoulkadid.pdf&usg=AOvVaw3ju3ew_iDo119XrBKNCv0d
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.
Next time out together, try swapping BCGs.
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.
Next time out together, try swapping BCGs.
This advice would have saved a good amount of trouble a time or two.
Next time out together, try swapping BCGs.
Do you suspect the BCG of the soft-shooting gun is leaking gas?
Next time out together, try swapping BCGs.
We both have mil-spec phosphate M16 BCGs, so it shouldn’t make a difference, but I’ll give it a try.
Does your accuracy suffer in hotter weather? I am curious why you are concerned if the ammunition feels hotter in higher temperature weather, but the carbine runs 100% and is accurate.
Not all mil-spec BCGs are created equal.
What brand is the BCG on the BA barrel?
We both have mil-spec phosphate M16 BCGs, so it shouldn’t make a difference, but I’ll give it a try.
Does your accuracy suffer in hotter weather? I am curious why you are concerned if the ammunition feels hotter in higher temperature weather, but the carbine runs 100% and is accurate.
Knew a precision shooter down in AZ. No BS, dude had a 12v ARB fridge for his ammo. Said there was significant POI shift with hot ammo, hard to be consistent.
I guess I just ain't a good enough shot to notice. :p
Not all mil-spec BCGs are created equal.
What brand is the BCG on the BA barrel?
His BCG is Aero Precision phosphate M16. His barrel is apparently midlength with 0.078” gas port and is also 16".
Knew a precision shooter down in AZ. No BS, dude had a 12v ARB fridge for his ammo. Said there was significant POI shift with hot ammo, hard to be consistent.
I guess I just ain't a good enough shot to notice. :p
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.
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.
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.
I’ll note that the stuff I stocked up and shoot isn’t anything special, just Wolf Gold M193.
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.
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.
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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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.
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.
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.
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?
Sent from my iPhone using Tapatalk
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.
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 work out yet, I'm not yet at 1,500 rounds.
You don't think so? Let's take another look-
Something I'm noticing is that in the spring time and moderate weather, my gun eject at about 3 o'clock or so. However when it's summer and the temperature is in the 90s and my gun was sitting in the sun for a while, my ejection is now closer to 2 o'clock...
...when firing 5.56 ammo...his gun ejects at consistent 3 o’clock, while mine is 2 o’clock...
I’ll note that the stuff I stocked up and shoot isn’t anything special, just Wolf Gold M193.
...I'm not yet at 1,500 rounds.
If the extractor spring is working fine, there will be little to no change in ejection angle as the carrier speed changes. You'll note your body's upper consistently ejects at 3 o'clock while yours varies from 3 o'clock to 2 o'clock depending on temperature. In this case, as the temperature goes up, so does pressure. When pressure goes up, carrier speed increases. When the extractor spring begins failing, ejection angle moves forward. When carrier speed increases, greater stress is placed on the extractor spring. When greater stress is placed on an extractor spring that's failing, ejection angle moves forward.
The only two extractor springs with the durability and reliability in uppers with barrel lengths of 16" or less is first and foremost the Colt extractor spring. The second is the Spring 5 coil spring. The only company I'm aware of using Colt springs is Colt. The only company using Sprinco springs that I'm aware of is Sionics and SOLGW. The reason Sionics and SOLGW use the Spring is because they consulted with Will Larson (IraqGunz), a very knowledgeable and experienced armorer.
In my experience with troubleshooting ARs is that other extractor springs usually start failing between 750 to 1500 rounds. Your DD upper is coming up on 1500 rounds and is showing a variation in ejection angle.
Extractor spring tension impacts ejection angle. As the tension on the extractor drops, the case isn't held against the ejector as firmly. This changes how the case is ejected and how it bounces off the case deflector. The angle moves forward until cases start bouncing back inside the ejection port. Somewhere in the process, the extractor will slip the rim completely and empties will get caught in the action and the bolt will over ride the rim of the next case in the mag. Or, the empty will be ejected and the bolt will over ride the base.
In the beginning, the empties will still be ejected a good distance. Don't let that fool you.
When I took the armorer's class taught by Will Larson, I discussed this subject with him at length. His (far greater) experience supported mine.
Taking all of this into consideration, to address your sharper recoil, try a new action spring and see if that helps.
You can either order a new Colt or Sprinco extractor spring and install it when it comes in, or you can wait until you get intermittent malfunctions and waste a box or more of ammo trying to troubleshoot the issue.
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.
I am inclined to agree. If the carbine is accurate and reliable, I would not be too concerned.
Asking questions is good and there is nothing wrong with being aware of changes in recoil, muzzle blast, changes in POI due to sunlight, etc., that means you are paying attention.
I shoot M1 Garand's and 1903 Springfield's a few times a month, so that might make me less concerned about the recoil of a .223 caliber rifle than other people.
The only two extractor springs with the durability and reliability in uppers with barrel lengths of 16" or less is first and foremost the Colt extractor spring. The second is the Spring 5 coil spring. The only company I'm aware of using Colt springs is Colt. The only company using Sprinco springs that I'm aware of is Sionics and SOLGW. The reason Sionics and SOLGW use the Spring is because they consulted with Will Larson (IraqGunz), a very knowledgeable and experienced armorer.
In my experience with troubleshooting ARs is that other extractor springs usually start failing between 750 to 1500 rounds. Your DD upper is coming up on 1500 rounds and is showing a variation in ejection angle.
Daniel Defense uses an o-ring and silver extractor spring in their bolts as of 2020. Some say this combination has a longer life than a stronger spring alone. I would like to believe there is a reason they sell their bolts with this combination other than mere greed. Nevertheless I have Colt copper-color springs on hand for spares.
It's generally accepted that carbines need more extractor tension than the original M16, and it's also generally accepted that the o-ring and extra power extractor together are usually too much.
We use a rifle extractor and O-ring on our rifles. We believe the O-ring has a longer service life than an extractor spring alone, while giving the increased extractor tension needed.
For a duty or defensive carbine it's also important to change the extractor spring based on a round count, not failure to extract.
And this cannot be over-stated. It is not that you don't "need" an extra-power spring if you have an o-ring, but extra-power springs are actually bad because they are more likely to break. So the way to think about it is that the o-ring saves you from having to resort to a high-stressed spring.
Once you have the o-ring to add tension, the goal should be to use the lowest-stressed spring, which should give the longest life.
I just measured every extractor spring Brownell's sells. I can say there is some scary stuff there.
The USGI spring from 1971 had a stress/strain ratio under 50% when compressed to 0.112. Those can last 18,000+ rounds. True, they only have 4 lbs of force at this height, but the o-ring will add in the extractor tension without having to resort to an extra power spring.
Why is an extra power spring bad? Because more force means more stress. Some of the springs from Brownell's had stress/strain ratios above 80%! If you monkey around with extra power springs, then change them every 1500 rounds.
The new M4 spring that is Copper colored is pretty interesting. It has exactly double the force of the earlier spring but does not have a huge amount of additional stress. If I were going to run a spring without an o-ring, I would use the new Colt M4 spring.
Or use an old-style 0.022 wire diameter USGI (people call this the '4 coil') with an o-ring and it should last the life of the bolt (but since it is cheap, might as well change it at 5000 rounds).
My research shows the O ring was adopted as an interim fix until the .mil could be convinced to approve the then new Colt extractor spring to the system, something the .mil resisted because it would “add a new NSN for the same part”. Until the upgraded spring was approved, they were stuck using the rifle extractor spring which was not strong enough for full auto in the M4 and prone to early failure.
Using an O ring introduces its own set of problems. O rings wear out, dry out and deteriorate. When the O ring starts deteriorating, the pieces impede extractor function.
Once institutional inertia was overcome and the upgraded Colt spring replaced the old spring, extraction issues in military M4s have been greatly reduced, if not eliminated. Over the years, I’ve only seen one Colt extractor spring prematurely fail and that was in one of my bolts. I suspect I damaged it during install
Bottom line- You can use the upgraded Colt spring which is proven to work. Or you can take your chances with the spring that made a redesigned spring necessary.
My research shows the O ring was adopted as an interim fix until the .mil could be convinced to approve the then new Colt extractor spring to the system, something the .mil resisted because it would “add a new NSN for the same part”. Until the upgraded spring was approved, they were stuck using the rifle extractor spring which was not strong enough for full auto in the M4 and prone to early failure.
Using an O ring introduces its own set of problems. O rings wear out, dry out and deteriorate. When the O ring starts deteriorating, the pieces impede extractor function.
Once institutional inertia was overcome and the upgraded Colt spring replaced the old spring, extraction issues in military M4s have been greatly reduced, if not eliminated. Over the years, I’ve only seen one Colt extractor spring prematurely fail and that was in one of my bolts. I suspect I damaged it during install
Bottom line- You can use the upgraded Colt spring which is proven to work. Or you can take your chances with the spring that made a redesigned spring necessary.
MistWolf I would like to ask you your opinion on the Colt Gold Extractor Springs compared to the 5 Coil Springco Extractor Springs, which do you think are the best? Or are they about equal?
Whenever I acquire a new AR or new to me AR, I will replace the Extractor Spring with a 5 Coil Springco and pitch the factory spring and O-ring in the trash. I will also put a new Ejector Spring in, it's a Sprinco also. I do have 2 Colts and they have the Colt Gold Springs in them just because that is what was always in them and naturally it's the best or tied for best with the Springco. There are a couple other things I do to a newly acquired AR but that doesn't pertain to this.
I don't want to derail this but I also don't think its worth me starting a new post about this.
Thank you.
I never paid attention to gas port size or buffer weights on my AR's, but this thread had me wondering. I researched the 16" carbines I have in my stable and learned that all of them are considered overgassed. I do not own pin gauges that small, so I have to rely on the accuracy of internet information on gas port sizes (bonjour). All the carbines are reliable with a wide variety of ammunition from Wolf steel case 62g fmj to hot 40g hunting loads, so I won't be making any changes.
In my limited experience, I don't think gas port size is a serious issue with barrels longer than 14". Increased mechanical noise from the buffer and BCG is secondary to reliability and accuracy IMHO.
It's entirely possible to over gas any barrel, but the longer gas systems have lower port pressures and are more forgiving.
A .005" larger port on a MID-length barrel may be controllable with a heavy buffer, but .005" larger on a Carbine gas barrel may start to cause issues.
I never paid attention to gas port size or buffer weights on my AR's, but this thread had me wondering. I researched the 16" carbines I have in my stable and learned that all of them are considered overgassed. I do not own pin gauges that small, so I have to rely on the accuracy of internet information on gas port sizes (bonjour). All the carbines are reliable with a wide variety of ammunition from Wolf steel case 62g fmj to hot 40g hunting loads, so I won't be making any changes.
In my limited experience, I don't think gas port size is a serious issue with barrels longer than 14". Increased mechanical noise from the buffer and BCG is secondary to reliability and accuracy IMHO.
My research shows the O ring was adopted as an interim fix until the .mil could be convinced to approve the then new Colt extractor spring to the system, something the .mil resisted because it would “add a new NSN for the same part”. Until the upgraded spring was approved, they were stuck using the rifle extractor spring which was not strong enough for full auto in the M4 and prone to early failure.
Using an O ring introduces its own set of problems. O rings wear out, dry out and deteriorate. When the O ring starts deteriorating, the pieces impede extractor function.
Once institutional inertia was overcome and the upgraded Colt spring replaced the old spring, extraction issues in military M4s have been greatly reduced, if not eliminated. Over the years, I’ve only seen one Colt extractor spring prematurely fail and that was in one of my bolts. I suspect I damaged it during install
Bottom line- You can use the upgraded Colt spring which is proven to work. Or you can take your chances with the spring that made a redesigned spring necessary.
The "new" gold spring design was approved in December 2002, and the NSN assigned in February 2003, and incorporated into the bolt drawing in March 2003, which is around the same time as most all of the other improvements, the heavy barrel, the heavy buffer, and many other minor things.
That is a fairly timely change.
I think you'll find the delay was production and fielding. It is one thing to draw a pretty drawing and assign it a number in the catalog, it is another thing to make a millions of them and get them out to the users for replacement. Then there is the possibility that the initial fielding plan was to replace through attrition, and mandatory replacement at depot rework. This means that unless they break in the field, they are not replaced until it goes back to depot for rework.
It's entirely possible to over gas any barrel, but the longer gas systems have lower port pressures and are more forgiving.
A .005" larger port on a MID-length barrel may be controllable with a heavy buffer, but .005" larger on a Carbine gas barrel may start to cause issues.
The shortest barrels I have considerable experience with are 14.5". In your experience how many rounds would it take for a gas port to erode to .005" larger than on a new 16" barrel if shooting at a moderate pace, no magazine dumps, etc.?
MistWolf I would like to ask you your opinion on the Colt Gold Extractor Springs compared to the 5 Coil Springco Extractor Springs, which do you think are the best? Or are they about equal?
I prefer to recommend Colt extractor springs because I have first hand experience with them.
I have very little hands on experience with the Sprinco spring. However, I did have a discussion on the subject with Will Larson who had extensive experience working on ARs (along with other families of weapons) in a combat zone as well as here in the US. He thought enough of the Sprinco spring that he recommended Sionics and SOLGW use them in their ARs. Will's bona fides were good enough that I recommend the Sprinco springs based on his say so. I haven't heard any complaints from anyone using the Sprinco spring.
I see no reason to replace a Sprinco spring with a Colt spring or vice versa.
Will passed away not long after I took his armorer's course. He is missed.
The shortest barrels I have considerable experience with are 14.5". In your experience how many rounds would it take for a gas port to erode to .005" larger than on a new 16" barrel if shooting at a moderate pace, no magazine dumps, etc.?
Your gas port does not erode in diameter. If you start with a 0.062" gas port after a few thousand round you still will not be slipping a 0.065" diameter gage pin in the hole.
https://www.thefirearmblog.com/blog/wp-content/uploads/2016/10/shot-out-barrel-gas-port-e1477188776344-495x660.jpg
This quote sums it up quite well:
"People have the mistaken idea that gas port erosion is the gas port actually getting bigger.
"It ain't so.
"The erosion mechanism is a widening of the gas port on the downstream side, making the gas port a more efficient nozzle, thereby allowing increasing the maximum mass flow through the port. This makes the post-port pressure higher. If you look at a typical eroded port, gauging the hole would not reveal a significant enlargement of the port."
Your gas port does not erode in diameter. If you start with a 0.062" gas port after a few thousand round you still will not be slipping a 0.065" diameter gage pin in the hole.
https://www.thefirearmblog.com/blog/wp-content/uploads/2016/10/shot-out-barrel-gas-port-e1477188776344-495x660.jpg
This quote sums it up quite well:
"People have the mistaken idea that gas port erosion is the gas port actually getting bigger.
"It ain't so.
"The erosion mechanism is a widening of the gas port on the downstream side, making the gas port a more efficient nozzle, thereby allowing increasing the maximum mass flow through the port. This makes the post-port pressure higher. If you look at a typical eroded port, gauging the hole would not reveal a significant enlargement of the port."
Thank you, a picture is worth a thousand words.
The .005" example is not due to erosion, but due to different manufacturers various specifications.
In your experience how many rounds would it take for a gas port to erode to .005" larger than on a new 16" barrel if shooting at a moderate pace, no magazine dumps, etc.?
Bottom line- You can use the upgraded Colt spring which is proven to work. Or you can take your chances with the spring that made a redesigned spring necessary.
Why does Daniel Defense still using a silver (rifle?) spring and o-ring in 2020? Longer life than the Colt carbine spring seemed like a plausible explanation for the choice, and relevant to the claim that the DD extractor setup was likely wearing out at 1500 rounds.
I prefer to recommend Colt extractor springs because I have first hand experience with them.
I have very little hands on experience with the Sprinco spring. However, I did have a discussion on the subject with Will Larson who had extensive experience working on ARs (along with other families of weapons) in a combat zone as well as here in the US. He thought enough of the Sprinco spring that he recommended Sionics and SOLGW use them in their ARs. Will's bona fides were good enough that I recommend the Sprinco springs based on his say so. I haven't heard any complaints from anyone using the Sprinco spring.
I see no reason to replace a Sprinco spring with a Colt spring or vice versa.
Will passed away not long after I took his armorer's course. He is missed.
We were likely in the same class. Anyhow straight from the M4C archives 2019 by Will himself
[The Colt copper washed extractor spring is a good option, as is the Sprinco enhanced spring. I have also used (and still have) BCM enhanced springs as well. Any of them will work.]
Nuff said?
Your gas port does not erode in diameter. If you start with a 0.062" gas port after a few thousand round you still will not be slipping a 0.065" diameter gage pin in the hole.
https://www.thefirearmblog.com/blog/wp-content/uploads/2016/10/shot-out-barrel-gas-port-e1477188776344-495x660.jpg
This quote sums it up quite well:
"People have the mistaken idea that gas port erosion is the gas port actually getting bigger.
"It ain't so.
"The erosion mechanism is a widening of the gas port on the downstream side, making the gas port a more efficient nozzle, thereby allowing increasing the maximum mass flow through the port. This makes the post-port pressure higher. If you look at a typical eroded port, gauging the hole would not reveal a significant enlargement of the port."
How much does the bolt speed change with a dramatic amount of erosion?
Why does Daniel Defense still using a silver (rifle?) spring and o-ring in 2020? Longer life than the Colt carbine spring seemed like a plausible explanation for the choice, and relevant to the claim that the DD extractor setup was likely wearing out at 1500 rounds.
I have no idea. But my experience is the rifle spring, with or without O ring, isn't as durable in shorter ARs. Especially when a suppressor is added.
We pin gas blocks, stake gas keys and castle nuts, lube carriers, grease and torque three times the barrel nut- all in the name of reliability and durability. But folks still cling to the problematic old style extractor spring.
We were likely in the same class.
The class was at Ready Gunner. My brother was there with me. The class was well worth it.
The class was at Ready Gunner. My brother was there with me. The class was well worth it.
Yeah, I kinda remember you guys. It's a bit fuzzy. I'm old. ;)
Yep, it sure does. That's why people think M4s and Mk18s are overgassed. They have to be able to work whether it's 130 or -40 outside. Try taking your perfectly tuned AR out on a really cold day and firing a round straight down into the ground. One thing if it's a competition gun that you can tune for the season, quite another for a nightstand gun that has to just work no matter what.
I prefer to recommend Colt extractor springs because I have first hand experience with them.
I have very little hands on experience with the Sprinco spring. However, I did have a discussion on the subject with Will Larson who had extensive experience working on ARs (along with other families of weapons) in a combat zone as well as here in the US. He thought enough of the Sprinco spring that he recommended Sionics and SOLGW use them in their ARs. Will's bona fides were good enough that I recommend the Sprinco springs based on his say so. I haven't heard any complaints from anyone using the Sprinco spring.
I see no reason to replace a Sprinco spring with a Colt spring or vice versa.
Will passed away not long after I took his armorer's course. He is missed.
Thank you. I wish I had joined instead of just nosed about while Mr Will was still with us.
We were likely in the same class. Anyhow straight from the M4C archives 2019 by Will himself
[The Colt copper washed extractor spring is a good option, as is the Sprinco enhanced spring. I have also used (and still have) BCM enhanced springs as well. Any of them will work.]
Nuff said?
Thank you also, haven't figured out how to quote two different people in the same post or I would have thanked you and MistWolf at the same time.
How much does the bolt speed change with a dramatic amount of erosion?
It not really that simple. Here is a test where the cyclic rate was recorded over an endurance test of 6,000 rounds:
(click to enlarge)
66200
As you can see, there is a lot of variation.
It not really that simple. Here is a test where the cyclic rate was recorded over an endurance test of 6,000 rounds:
(click to enlarge)
66200
As you can see, there is a lot of variation.
I did not know if bolt speed would change the accuracy of a match rifle. I changed barrels when accuracy was over .75 MOA when I competed.
I change barrels on carbines when accuracy is over 2.5 MOA at 300 yards with M193.
I did not know if bolt speed would change the accuracy of a match rifle. I changed barrels when accuracy was over .75 MOA when I competed.
I change barrels on carbines when accuracy is over 2.5 MOA at 300 yards with M193.
How many rounds did the barrels tend to last before being changed?
I did not know if bolt speed would change the accuracy of a match rifle. I changed barrels when accuracy was over .75 MOA when I competed.
I change barrels on carbines when accuracy is over 2.5 MOA at 300 yards with M193.
Throat and/or muzzle wear will degrade accuracy long before problems due to gas port erosion start to manifest themselves . . . .
How many rounds did the barrels tend to last before being changed?
I changed stainless match barrels between 3000 and 4000 rounds. The barrels were still serviceable and I sold them to people who shot at distances of 300 yards and closer and could not tell the difference between one of my used barrels and a new barrel. I sold the bolt that was used with the barrel.
I change carbine barrels between 8,000 and 10,000 rounds to maintain sub 2-1/2 MOA accuracy at 300 yards with 55g FMJ. A stripped bolt will not close on a field gauge when I scrap them. If I push a barrel until a stripped bolt will close on a Field gauge, I usually see 12,000 rounds of service life.
An interesting thing about the AR-15 platform is that I did not notice a marked difference in accuracy between serviceable magazines like I did with the M1A.
I changed stainless match barrels between 3000 and 4000 rounds. The barrels were still serviceable and I sold them to people who shot at distances of 300 yards and closer and could not tell the difference between one of my used barrels and a new barrel. I sold the bolt that was used with the barrel.
I change carbine barrels between 8,000 and 10,000 rounds to maintain sub 2-1/2 MOA accuracy at 300 yards with 55g FMJ. A stripped bolt will not close on a field gauge when I scrap them. If I push a barrel until a stripped bolt will close on a Field gauge, I usually see 12,000 rounds of service life.
An interesting thing about the AR-15 platform is that I did not notice a marked difference in accuracy between serviceable magazines like I did with the M1A.
Were your Carbine Barrels Stainless Steel also?
bulletproofwelding_1
07-30-21, 21:08
Why worry about it do you think are boys over in the sand box care were they brass hits.
Were your Carbine Barrels Stainless Steel also?
No. The Colt barrels, and others, were chrome lined. The carbines get run hard for about half of the barrel life. Heat is an issue.
No. The Colt barrels, and others, were chrome lined. The carbines get run hard for about half of the barrel life. Heat is an issue.
Oh ok, now I understand. Thank you.
SPECIAL FEATURES
Our 5.56 mm F1 ball ammunition is manufactured at
Australian Munitions’ Benalla munitions facility and is
currently in use with the Australian Defence Force (ADF) in
the Austeyr individual weapon and F89 Minimi light support
weapon.
Australian Munitions’ 5.56 mm F1 ball ammunition employs
a specifically designed single base propellant with very low
temperature coefficient of ballistics to ensure velocities and
pressures remain consistent within variations in ammunition
te
That briefs well, but even military ammo suffers from temperature changes. https://www.psmagazine.army.mil/News/Article/2653340/ammunition-how-heat-affects-ammo/
I should have posted this "mate"=http://www.australian-munitions.com.au/wp-content/uploads/2019/08/ARM_AM_5.56-F1-A4-2pp_web.pdf
Mostly marketing. Notice they don’t go into specifics. The Australian powder marketed by Alliant here in the US that is said to be temp stable has more than double the temperature sensitivity of Hogdon Extreme series, but it is wolds better than any ball powder.
So at the end of the day, “temperature stable” compared to what?
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So I shot with my friend again today, and though he let me shoot his rifle he doesn't want to switch BCGs, thinks there's some kind of risk of not headspaced together or something. Either way, I loaded the usual Wolf Gold WM193 and shot my rifle and his rifle back to back. Again I can notice a difference, with his feeling softer, despite also being midlength 16", with larger 0.078" gas port, and carbine buffer. The DD's 0.073" gas port and H buffer feels harsher, I'm throwing brass at about 2 o'clock, his gun throws brass at 3-4 o'clock. In fact his rifle firing WM193 feels like my rifle when firing PMC Bronze .223.
I'm not complaining because I think it's some unmanageable recoil. I'm more confused and annoyed why my rifle feels more gassy even though the paper specs should say otherwise. Could it be that his BCG is not as gas efficient? Are 16" midlength DDs known for being overgassed? I've searched around, but as far as I know their 10.3" were overgassed, but nothing on the 16" midlengths.
So at the end of the day, “temperature stable” compared to what?
When a military contractor states their propellants are “temperature stable”, it means the military finds the "instability" within acceptable limits.
WC846 and WC844 are “temperature stable” as far as the US military is concerned, some civilians might disagree.
When a military contractor states their propellants are “temperature stable”, it means the military finds the "instability" within acceptable limits.
WC846 and WC844 are “temperature stable” as far as the US military is concerned, some civilians might disagree.
Yes, I understand what military considers acceptable. And it isn’t very stable. Which is why I said, “compared to what”. The claim in the link is meaningless.
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Yes, I understand what military considers acceptable. And it isn’t very stable. Which is why I said, “compared to what”. The claim in the link is meaningless.
“Compared to what”?
The Australian Defense Minitsry's requirements for propellant stability, obviously. ;)
And, "the claim in the link is meaningless," is incorrect, it means that the Australian Defense Ministry finds their propellant temperature insensitive.
BTW, they are using IMR 8208 XBR, which is a very stable propellant.
“Compared to what”?
The Australian Defense Minitsry's requirements for propellant stability, obviously. ;)
And, "the claim in the link is meaningless," is incorrect, it means that the Australian Defense Ministry finds their propellant temperature insensitive.
BTW, they are using IMR 8208 XBR, which is a very stable propellant.
It doesn’t actually give us data. It’s a claim.
8208 is fairly stable, but there is far better powder for temp stability. I find it strange they aren’t running a true ball powder.
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It doesn’t actually give us data. It’s a claim.
8208 is fairly stable, but there is far better powder for temp stability. I find it strange they aren’t running a true ball powder.
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Which powders are more stable? I've always thought of XBR as one of the best off the shelf options commonly available. (Not that it's common anymore.)
Which powders are more stable? I've always thought of XBR as one of the best off the shelf options commonly available. (Not that it's common anymore.)
The lower the number the less change in velocity per degree change in temperature, i.e., the lower the better.
https://www.predatormastersforums.com/forums/gallery/80/full/2352.png
Which powders are more stable? I've always thought of XBR as one of the best off the shelf options commonly available. (Not that it's common anymore.)
In my experience from using them, Varget, H4350, H4831SC, H1000, etc. basically every powder in the Extreme line of powders is as good as you can get.
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Good information Lysander. From this point forward I am going to take a surface thermometer, in addition to a regular thermometer, with me to the range when I collect data.
Good information Lysander. From this point forward I am going to take a surface thermometer, in addition to a regular thermometer, with me to the range when I collect data.
One thing you can do to experiment is take a cooler on a hot day. Also be sure not to let a round bake in the chamber of a hot barrel.
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Good information Lysander. From this point forward I am going to take a surface thermometer, in addition to a regular thermometer, with me to the range when I collect data.
The artillery guys always had a little thermometer in with the propelling charges. The fire direction center would use that information to fine tune the firing elevation.
There is also a misconception that the barrel temperature is the only important factor, or that hot ammunition in a cold barrel will not be effected.
When propellant burns, it releases energy inside the grains of powder, if the grains are hot, they have, in addition to the stored chemical energy, thermal energy. So, hot propellant will produce higher pressures and velocities.
A hot barrel may warp, or droop, or may experience some other phenomenon that changes the point of impact or accuracy, as well.
The artillery guys always had a little thermometer in with the propelling charges. The fire direction center would use that information to fine tune the firing elevation.
There is also a misconception that the barrel temperature is the only important factor, or that hot ammunition in a cold barrel will not be effected.
When propellant burns, it releases energy inside the grains of powder, if the grains are hot, they have, in addition to the stored chemical energy, thermal energy. So, hot propellant will produce higher pressures and velocities.
A hot barrel may warp, or droop, or may experience some other phenomenon that changes the point of impact or accuracy, as well.
Good description. I would add that with small arms, as the barrel heats and molecules expand, the bore is tighter and created more pressure and thus the increased velocity is amplified.
When testing ammunition, the time between shots needs to allow the bore to cool. When testing barrels, it’s good to know what it and the ammunition does with increased rate of fire.
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