Bucks13 wrote:Also glad I found this thread as I am having the same exact problem. Question, is overgassed defined by powder or pressure? I ask b/c I am getting failures of 110s, 155s and even on some 220s! 8.1" barrel, I reamed the barrel to 0.098", I've run it with standard buffer, Spike's T2 buffer and with the SpringCo White Hot spring...still no luck. And, I even get that same failure trying to chamber the first round of 110s (Varmageddon). As the OP, I was thinking magazine, but who knows. Thoughts?
Are you using a suppressor? .098" on a 8.1" barrel is actually pretty good, and that should cycle pretty much everything, except subs unsuppressed. At least according to MicroMOA's website: http://micromoa.com/300-blk-port-size-testing/ .... I tried different magazines with my problem, P-Mags, GI mags, Lancer, and nothing changed. It will run everything from 120 to 220, just not 110's. Your problem doesn't sound like an over-gassing problem. Is your gas block secured properly? Also, in my thinking, for whatever it's worth, I would think over-gassed is pressure. I reloaded some 110's with minimum charge and maximum charge with the same failure to feed problem, but I'm not an "expert" haha.
ascendancy2010 wrote:
See, that's unusual if the gas port is so small. I just ordered the Baby Govnah since they can drill a custom sized gas hole in it, and you don't need to worry about an adjustable gas block. My gas port is .125" and the Baby Govnah will be .096". This should cycle pretty much everything for me. My buddy also has a Daniel Defense and I believe his gas port hole is .098" on a 10.3" barrel. I feel like if your port hole is .078" it has to be something else.
Yeah, so I verified that the gas port is indeed 0.078"
In that case, and because apparently pistols should have heavier buffers than regular carbine weight, I need to increase reciprocating mass.
I was wondering, though, if just reducing gas with an adjustable block without adding weight would make it cycle reliably in all modes and reduce gas in the face. I have an adjustable gas block to use with it, so it's worth trying.
If you already have an adjustable gas block, it won't hurt to try. Just let us know what happens!
Ok, so I have ordered a Baby Govnah with a gas port hole of .096" compared to my barrels .125" gas port hole. It shipped today, so I will let everyone know how well it works and if it fixes my problems. The regular Govnah is too large to fit under my Daniel Defense Lite Rail III, unfortunately. I was really looking forward to getting it.
ascendancy2010 wrote:Ok, so I have ordered a Baby Govnah with a gas port hole of .096" compared to my barrels .125" gas port hole. It shipped today, so I will let everyone know how well it works and if it fixes my problems. The regular Govnah is too large to fit under my Daniel Defense Lite Rail III, unfortunately. I was really looking forward to getting it.
Stop thinking in thousandths .001, start thinking in percentages.
The jump from .067(what Micro says is minimum for suppressed supers) to .078 is around 40% (area of a circle). The jump from .067 to .125 is more than 300%. So you will have that much more gas volume. Take a look at the math and see how far you are reducing your port by volume, you will be surprised.
A carbine buffer at 3.8 oz is only 80% of the weight of an H2 at 4.6 oz.
A grain of powder in a super load is more than 5%.
If you look at Attila's build he has a port that is 40% more than needed, pushing only 80% of the weight.
Think his carrier might be running a little fast and out running the magazine?
ascendancy2010 wrote:Ok, so I have ordered a Baby Govnah with a gas port hole of .096" compared to my barrels .125" gas port hole. It shipped today, so I will let everyone know how well it works and if it fixes my problems. The regular Govnah is too large to fit under my Daniel Defense Lite Rail III, unfortunately. I was really looking forward to getting it.
Stop thinking in thousandths .001, start thinking in percentages.
The jump from .067(what Micro says is minimum for suppressed supers) to .078 is around 40% (area of a circle). The jump from .067 to .125 is more than 300%. So you will have that much more gas volume. Take a look at the math and see how far you are reducing your port by volume, you will be surprised.
A carbine buffer at 3.8 oz is only 80% of the weight of an H2 at 4.6 oz.
A grain of powder in a super load is more than 5%.
If you look at Attila's build he has a port that is 40% more than needed, pushing only 80% of the weight.
Think his carrier might be running a little fast and out running the magazine?
Wow, Dellet, you're the man. I've been spending the last three days trying to figure out the amount of gas, rather looking at the hole itself. This is a lot more simple. This shows that I'm 300% more than needed on gas, pushing 117% of the weight. No wonder my brass has been hitting so hard it's been removing my finish on my shell deflector (only 100 rounds of supers). I know my bolt was cycling faster than the magazine, this may be the same problem for Attila.
So if I'm pushing 117% of the mass, reducing the port by 130% to .096", now being 126% over whats necessary. This should hopefully fix the problem. The question is now, with 117% of the weight, will subs work if I'm only 103% over what's required? Hm.. I need this gas block to arrive so I can test more! Any predictions?
The system was designed to use an H2 buffer with pistol gas, some run the lighter carbine. There have not been too many post running the heavier H3. It will depend on the powder and bullet combo. 1680 is very easy to use with many bullets, H110/296 is a little tougher. That's where the gas volume and burn rates make a difference. Some powders create more gas and it seems like volume is more important than pressure in many ways.
The big thing about cycling is you had no problem with subs, low gas volume and pressure. Some success with supers until you added the suppressor. Then the failures were all the time. The more pressure you added the worse it got. That's a good indication the bolt was being pushed too hard/fast.
So the question becomes if you're driving too fast, do you leave your right foot on the gas and put your left foot on the brake (heavier buffer) to slow down. Or do you simply take your foot off the gas(close the gas port). The Blackout is all about compromise, if you want to run subs, non-suppressed, and supers suppressed. You lose a little on both ends doing that.
Rebel runs an sbr with a .120/.125 port and a carbine buffer. I think he runs some supers suppressed, but they are handloads, maybe he'll chime in and say if he has ever ran factory loads. I think you might be able have luck with the 120 UMC.
I am not a fan of large gas ports and have run most pretty small. All it has done is limit my powder choices a little bit.
Look forward to hear how it all works out, it's a lot more fun when it works as advertised.
Bucks13 wrote:Also glad I found this thread as I am having the same exact problem. Question, is overgassed defined by powder or pressure? I ask b/c I am getting failures of 110s, 155s and even on some 220s! 8.1" barrel, I reamed the barrel to 0.098", I've run it with standard buffer, Spike's T2 buffer and with the SpringCo White Hot spring...still no luck. And, I even get that same failure trying to chamber the first round of 110s (Varmageddon). As the OP, I was thinking magazine, but who knows. Thoughts?
Are you using a suppressor? .098" on a 8.1" barrel is actually pretty good, and that should cycle pretty much everything, except subs unsuppressed. At least according to MicroMOA's website: http://micromoa.com/300-blk-port-size-testing/ .... I tried different magazines with my problem, P-Mags, GI mags, Lancer, and nothing changed. It will run everything from 120 to 220, just not 110's. Your problem doesn't sound like an over-gassing problem. Is your gas block secured properly? Also, in my thinking, for whatever it's worth, I would think over-gassed is pressure. I reloaded some 110's with minimum charge and maximum charge with the same failure to feed problem, but I'm not an "expert" haha.
I am using a suppressor, and at one point, I thought supers would cycle unsuppressed and not suppressed, but that is no longer the case...additionally, my YHM Phantom 7.62 seems to slow down the velocity. Not sure of that effect on pressure and cycling though. I've taken the block and even the barrel off a few times, with no luck after going back on. The part that gets me is that I see the problem trying to chamber a round using the bolt release, with the 110 varms. 110 Barnes Black Tips (@2.25" OAL) cycle perfectly.
Oh, and I polished my feed ramps to no avail...though they look pretty now!
twcrowe12 wrote:I think mine is .125". I was having a little trouble with the bolt locking back so I drilled it out. Going nice and slow in a drill press with plenty of cutting oil is the way to go.
And you're cycling everything suppressed without issue?
Yup. Even cycling subs unsuppressed so long as I hold the rifle tight to my shoulder. I'll be replacing the gas block here in a few days with an adjustable for running supers and I'll try to remember to take calipers to the gas port while I have it apart and verify the gas port size.
ascendancy2010 wrote: No wonder my brass has been hitting so hard it's been removing my finish on my shell deflector (only 100 rounds of supers).
Just so you know, that is normal regardless of your gas issue.
^^ this.
try adding a peice of velcro to your shell deflector (the soft side), this may also help soften the D dent in the case mouth as well
Reloading info shared is based on experiences w/ my guns. Be safe and work up your loads from published data. Web data may not be accurate/safe.
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