How common is gas blow by on steel cartridges? I was talking to a guy and he mentioned this happening. In regards to this happening me. I think it caused my chamber on a mini 14 to get dirty causing a film of carbon buildup and then making my rifle fail to extract. He also said loading a brass cartridge in 1 in 10 rounds will expand brass to full chamber sealing properly and removing carbon buildup on case extraction. I also wondered does this effect power and accuracy ? I also use lots of steel cases on my sks with zero problem. Ever. Now I know that the two are different one being made for steel and the other not, and I've made the decision to use brass only in the mini-14. I also cleaned and scrubbed the chamber and so far fired 70 rounds without any problem and am planning to keep a count of how many rounds that go through the rifle before it start acting up. Sorry to keep droning on but it gave me some food for thought.
Gas Blow-by with steel cartridges
- Thread starter vongh
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caribou
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Both the Russians and the Germans developed chambers with flutes that allowed gas to 'float' the neck and shoulders and assist in extraction, on designs that had no primary extraction, and they were designed to use Steel cartridges for every shot.The chambers were generous and had alotta room for soot and such.
Keeping a chamber clean when shooting sooty soviet milsurp steel cased ammo is a regular chore. The steel case reflexing rather faster than the softer brass and allowing soot, even protective coatings to accumulate in a chamber? just needs more cleaning.
Keeping a chamber clean when shooting sooty soviet milsurp steel cased ammo is a regular chore. The steel case reflexing rather faster than the softer brass and allowing soot, even protective coatings to accumulate in a chamber? just needs more cleaning.
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Brass has more elasticity than steel which means it has more spring back. Brass can expand to completely seal the chamber.
Steel being less elastic has less spring back. If loaded to a high enough pressure so it would seal the chamber completely, it would not spring back enough to allow for extraction. Because of this, steel cases do not seal the chamber as well and gas and carbon leak past the neck into the chamber. It's also why steel cased ammo is loaded to lower chamber pressures.
The SKS and the 7.62x39 ammo it shoots is designed to use steel cases. The case is steeply tapered to facilitate extraction
Steel being less elastic has less spring back. If loaded to a high enough pressure so it would seal the chamber completely, it would not spring back enough to allow for extraction. Because of this, steel cases do not seal the chamber as well and gas and carbon leak past the neck into the chamber. It's also why steel cased ammo is loaded to lower chamber pressures.
The SKS and the 7.62x39 ammo it shoots is designed to use steel cases. The case is steeply tapered to facilitate extraction
Swampman
Old Fart
vongh
I once saw a Colt 6920 in 5.56 mm (with a chrome lined bore & chamber) actually rip the rim off the first brass case fired after shooting a couple of hundred rounds worth of Russian steel cased factory loads. When we finally pounded the case out with a cleaning rod and hammer, the outside of it was almost completely black with carbon. After cleaning the case up with carb cleaner, we found that it had a rough texture pressed into the outer surface, it looked almost like it'd been bead blasted.
I reload a lot of Berdan primed cases, both brass and steel. My 7.62x39 bulk "blasting ammo" is usually loaded with 165 grain, powder painted hard cast bullets over various weight charges of Alliant 2400 in steel cases (I generally use the brass ones for subsonic loads). I try to use the lightest powder charge that'll reliably cycle a particular weapon or group of weapons.
SKS's will usually run well with about a grain less than AK's and VZ-58's seem to get by with about a half grain less than the Simonov's.
The point of this, is that even with low pressure loads in steel cases, non chrome lined chambers AND a powder known for burning dirty at lower pressures, I don't get enough carbon build up to cause any problems when switching over to brass cases. I can assure you that it's not because I treat these weapons gently. Before I started powder coating my cast bullets, it wasn't uncommon for me to "solder" the piston into the gas block of my AK's with lead.
I think one of the main reasons why Combloc weapons are known for their high reliability is cartridge design. A long sloping shoulder and lots of case taper, combined with lower chamber pressures (and "generously" cut chambers), are a large factor in making 7.62x39 chambered weapons so jam resistant and reliable.
The sharp shoulder, minimum case taper, high pressure and generally tighter chambers are what give 5.56x45 weapons their superior accuracy and ranging ability.
Reliability vs accuracy/range
You pay your money and take your choices...
I once saw a Colt 6920 in 5.56 mm (with a chrome lined bore & chamber) actually rip the rim off the first brass case fired after shooting a couple of hundred rounds worth of Russian steel cased factory loads. When we finally pounded the case out with a cleaning rod and hammer, the outside of it was almost completely black with carbon. After cleaning the case up with carb cleaner, we found that it had a rough texture pressed into the outer surface, it looked almost like it'd been bead blasted.
I reload a lot of Berdan primed cases, both brass and steel. My 7.62x39 bulk "blasting ammo" is usually loaded with 165 grain, powder painted hard cast bullets over various weight charges of Alliant 2400 in steel cases (I generally use the brass ones for subsonic loads). I try to use the lightest powder charge that'll reliably cycle a particular weapon or group of weapons.
SKS's will usually run well with about a grain less than AK's and VZ-58's seem to get by with about a half grain less than the Simonov's.
The point of this, is that even with low pressure loads in steel cases, non chrome lined chambers AND a powder known for burning dirty at lower pressures, I don't get enough carbon build up to cause any problems when switching over to brass cases. I can assure you that it's not because I treat these weapons gently. Before I started powder coating my cast bullets, it wasn't uncommon for me to "solder" the piston into the gas block of my AK's with lead.
I think one of the main reasons why Combloc weapons are known for their high reliability is cartridge design. A long sloping shoulder and lots of case taper, combined with lower chamber pressures (and "generously" cut chambers), are a large factor in making 7.62x39 chambered weapons so jam resistant and reliable.
The sharp shoulder, minimum case taper, high pressure and generally tighter chambers are what give 5.56x45 weapons their superior accuracy and ranging ability.
Reliability vs accuracy/range
You pay your money and take your choices...
carbine85
Member
I have / had several Mini 14 rifles. One of things I like about them is they shoot everything. The only problems I have experienced are FTF from a faulty mag. The oldest one started short stroking after 10K or so rounds and needed an op rod spring.
Are you saying the cases are sticking in the chamber or they don't clear the bolt?
Are you saying the cases are sticking in the chamber or they don't clear the bolt?
The typical operation of a self loading gun will cause gas to flow over the contracted brass during the extraction cycle. The barrel can't dump pressure out fast enough, and some actions are actually tuned to use that pressure to push the case out of the chamber against the bolt. It's when the action is tuned to have the bolt do it - too soon -that the extractor rips off the end because the case is still tightly stuck to the chamber wall.
Wipe off the extracted case on a white cloth and you will see gas residue on them all. Start with the .22 blowback -dirty brass. Work up thru the HK roller lock bolts - dirty brass. Next, a piston operated gun - dirty brass.
Of course when you check a DI operated gun we all know it's dumped by the gas tube blasting the case during extraction, no possible way a .223 sized bore could do more than the .070 gas port feeding a tube located two inches further "downstream" from the chamber. Or, so some would have you believe.
No, cases extracted from AR's are getting dirty just the same as any other, blowback from the barrel. Point being it's not brass or steel cases in particular, it's the dwell time that pressure exists in the barrel, and most actions extract the case while there still is some.
What kind of powder is used is MORE important, and steel cased ammo isn't known for high quality powder. In point of fact, most government issue powders aren't the leading edge clean smokeless versions, they are low bid just meets the spec bulk powders that can be made in large volumes. Not the most proficient at keeping the action clean.
So, if we observe that steel cased ammo from a second tier country seems to have a lot of residue getting trapped in the chamber, it may have less to do with the case and more what quality the powder. Of course, tho, if they were loading it with top tier powder, it would cost closer to $20 a box.
You get what you pay for.
Wipe off the extracted case on a white cloth and you will see gas residue on them all. Start with the .22 blowback -dirty brass. Work up thru the HK roller lock bolts - dirty brass. Next, a piston operated gun - dirty brass.
Of course when you check a DI operated gun we all know it's dumped by the gas tube blasting the case during extraction, no possible way a .223 sized bore could do more than the .070 gas port feeding a tube located two inches further "downstream" from the chamber. Or, so some would have you believe.
No, cases extracted from AR's are getting dirty just the same as any other, blowback from the barrel. Point being it's not brass or steel cases in particular, it's the dwell time that pressure exists in the barrel, and most actions extract the case while there still is some.
What kind of powder is used is MORE important, and steel cased ammo isn't known for high quality powder. In point of fact, most government issue powders aren't the leading edge clean smokeless versions, they are low bid just meets the spec bulk powders that can be made in large volumes. Not the most proficient at keeping the action clean.
So, if we observe that steel cased ammo from a second tier country seems to have a lot of residue getting trapped in the chamber, it may have less to do with the case and more what quality the powder. Of course, tho, if they were loading it with top tier powder, it would cost closer to $20 a box.
You get what you pay for.
jonnyc
Member
"It's also why steel cased ammo is loaded to lower chamber pressures."
I would love to see some documentation on this.
I would love to see some documentation on this.
yamahawarrior89
Member
I have loaded steel cases pretty hot without extraction issues.
I've pulled the bullets and dumped the powder from a 7.62x54 for the Mosin and pushed 150gr pills to 3000 for with steel cases. I had no split cases or extraction issues. The problem is the steel cases get work hardened much sooner than brass cases.
I only used the steel cases for its first load, then let them lay.
I've pulled the bullets and dumped the powder from a 7.62x54 for the Mosin and pushed 150gr pills to 3000 for with steel cases. I had no split cases or extraction issues. The problem is the steel cases get work hardened much sooner than brass cases.
I only used the steel cases for its first load, then let them lay.
MachIVshooter
Member
The fluted chamber of the G3/CETME and guns patterned after them was designed to prevent the brass expanding into the chamber too much by equalizing pressure inside and out because it is a delayed blowback system. They absolutely have extractors.
It is also not recommended to use steel cases in fluted chamber firearms, although I've done it for a long time with no ill effects. The alleged reason has to do with steel being harder on the flutes, but the reality is that the steel used in cartridge cases is quite soft-far, far softer than the chambers.
Brass is, generally, more malleable. Steel has more memory ("spring back"). And again, as cartridge cases are concerned, the steel used is very soft-sometimes softer than some brass cases. Definitely softer on the outside than nickel plated brass.
^^^^^This.
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