How tight are GCs supposed to be?

[Gunslinger]

I ask because I cast some boolits yesterday from my new LBT - .357 180gr gas check. I use Hornady gas checks. After being sized the checks are still not tightly installed and I am able to take them of with my fingernails?!?

[badgeredd]

I ask because I cast some boolits yesterday from my new LBT - .357 180gr gas check. I use Hornady gas checks. After being sized the checks are still not tightly installed and I am able to take them of with my fingernails?!?

It sounds like you shank is just a little small. There are 2 things you can do to correct this. The first if to change alloy to get a bigger shank. (NOT my prefered solution) The second would be to carefully lapp JUST the gas check shank to in the mold to produce a larger shank. Since I like the alloy I use, I change the mold to make a shank large enough to fit my GCs. Most of the comments I've seen from members were to the effect that they preferred a tightly fit gas check.

Edd

[RayinNH]

You could try annealing a few to see if that helps. They may just have enough spring back to make them loose as they are...Ray

[hornady]

Not a lot of info on your lube /seizer. I use a Lyman 450 and Hornady checks The hornady check are a crimp on. And I have had great results with them. If its not the shank or a nub on the bullet base, I would look at what you are crimping them on with.

[Leftoverdj]

I ask because I cast some boolits yesterday from my new LBT - .357 180gr gas check. I use Hornady gas checks. After being sized the checks are still not tightly installed and I am able to take them of with my fingernails?!?

GCs can vary a little from batch to batch. Even half a thou in wall thickness can cause what you describe. I don't worry about it unless they come off very easily. Even the old slip fit Lyman GCs stayed on most of the time with nothing holding them.

If you do wish to enlarge the shank, the simple way is to chuck a bullet nose first in a spare drill chuck and coat the shank with fine valve grinding compound. Turn by hand while applying light pressure to the mould handles. Doesn't take much turning because the reduction in diameter is twice the thickness of the metal removed.

[Bret4207]

They don't need a death grip. When the powder hits the GC and the boolits starts moving everything changes anyway. As long as they don;t fall off in loading, start there. If they seem to be falling off in flight (something claimed by many, but I've never seen) and causing big groups then you have a problem.

[Shiloh]

You could try annealing a few to see if that helps. They may just have enough spring back to make them loose as they are...Ray

I anneal my gaschecks. There is some springback in them. After annealing, no more spring back issues.

Shiloh

[anachronism]

You could also send the mould back to Veral with a sample of your gaschecks & he'll make any adjustments necessary. Personally, I'd try annealing them first, it makes gaschecks fit like they were molded to the bullet.

[Char-Gar]

I really don't think you have a problem.

I anneal all gas checks as a matter of principal and that takes all of the fight out of them. All sort of benefits. Like Bret said, once the round lights off and the pressure smacks the bullet base that gas check is not going anywhere but down the barrel on the base of the bullet.

My advice is to anneal your checks and firgit the rest.

[Jumptrap]

I really don't think you have a problem.

I anneal all gas checks as a matter of principal and that takes all of the fight out of them. All sort of benefits. Like Bret said, once the round lights off and the pressure smacks the bullet base that gas check is not going anywhere but down the barrel on the base of the bullet.

My advice is to anneal your checks and firgit the rest.

I am onboard with Charger all the way. In fact, I'll go on to say that I have often thought about what happens after the powder is ignited and the pressure builds.....an how it affects the whole trip down the barrel.

Many have postulated on the effects of pressure and without belaboring the audience further with my humble opinions on the subject, I would ask you to consider a few things:

Pressure of any sort...water, air, hydraulic, atmospheric, etc., etc, increases it's effects by the area upon which it is imparted. Our resident professor, Felix, can expound on this phenomena in scientific terms with which, I am unversed. However, in layman's terms, the bigger the surface acted upon, the greater the relative force applied. So....if the hull of a submarine is exposed to 200 (two hundred) PSI....the effects are vastly different than when applied to a one inch piston. Also, when an air compressor tank is filled to a pressure of 200 psi......we consider that is pretty high pressure inside that tank.....and when the compressed air is released through a blow gun nozzle......it really comes out with some force! Next, consider the thrust of a jet engine; it is measured in pounds of thrust.....the fuel/air mixture being compressed inside the jet turbine and allowed to exhaust out the rear at unrestricted, high velocity. The tremendous volume of hot exhaust gases at say 25,000 pounds of thrust....will propel a jet fighter in excess of Mach 1....and that brother, is hauling donkey!

Okay, return to the bullet down the bore by expanding propellant gases for a moment. Here, we are talking about peak pressures exceeding SIXTY THOUSAND (60,000) psi in full house loads. Low pressure is JUST 15,000 psi!

Has that sunk in.....yet?

LOW PRESSURE is 15,000 psi!

That brings us back to the area acted upon by the pressure and in the case of a bullet base....it's fairly small...but the pressures are quite high! If 15,000 psi were applied to anything beyond a bathysphere or other special pressure vessel..the end results would be catastrophic collapse or....explosion. In essence, a gun barrel/chamber forms a high strength pressure vessel and how it withstands the extreme pressures are due the fact that the bullet begins to move instantly upon ignition, and constantly increases the volume of the cylinder as the gases expand and then decay rapidly at the time when the bullet exits the bore. If the bullet doesn't move...a ruptured barrel/blown action results.....pretty simple!

Before the bullet exits and while the expanding gases are exerting their force on the bullet's base, chamber walls, bore, etc., it is also working against that gascheck. That thin cup of gilding metal (an alloy of zinc and copper) literally gets the urine mashed out of it. It expands as far as the bullet base and the bore will allow it to. The soft cast bullet obturates as well, swelling to the limits of the bore walls.....and in effect, pressure welds the gascheck and bullet base together. Once free of the bore's restrictive boundaries, the gascheck might....but not always, depart from the bullet. I cannot prove, or disprove, that this affects the bullet's flight. While it can be surmised that bullets free of the gascheck will have different flight characteristics than those with the gascheck still attached.....I cannot prove it or disprove it due to the fact that I have never been able to recover intact bullets down range....at least enough to say that all arrived on target wearing or not wearing, the gascheck.

In conclusion; considering the extreme forces applied to the gaschecked bullet during the launch sequence, I doubt very damned seriously that the looseness of the attached gascheck amounts to anything worth consideration.

[StarMetal]

I am onboard with Charger all the way. In fact, I'll go on to say that I have often thought about what happens after the powder is ignited and the pressure builds.....an how it affects the whole trip down the barrel.

Many have postulated on the effects of pressure and without belaboring the audience further with my humble opinions on the subject, I would ask you to consider a few things:

Pressure of any sort...water, air, hydraulic, atmospheric, etc., etc, increases it's effects by the area upon which it is imparted. Our resident professor, Felix, can expound on this phenomena in scientific terms with which, I am unversed. However, in layman's terms, the bigger the surface acted upon, the greater the relative force applied. So....if the hull of a submarine is exposed to 200 (two hundred) PSI....the effects are vastly different than when applied to a one inch piston. Also, when an air compressor tank is filled to a pressure of 200 psi......we consider that is pretty high pressure inside that tank.....and when the compressed air is released through a blow gun nozzle......it really comes out with some force! Next, consider the thrust of a jet engine; it is measured in pounds of thrust.....the fuel/air mixture being compressed inside the jet turbine and allowed to exhaust out the rear at unrestricted, high velocity. The tremendous volume of hot exhaust gases at say 25,000 pounds of thrust....will propel a jet fighter in excess of Mach 1....and that brother, is hauling donkey!

Okay, return to the bullet down the bore by expanding propellant gases for a moment. Here, we are talking about peak pressures exceeding SIXTY THOUSAND (60,000) psi in full house loads. Low pressure is JUST 15,000 psi!

Has that sunk in.....yet?

LOW PRESSURE is 15,000 psi!

That brings us back to the area acted upon by the pressure and in the case of a bullet base....it's fairly small...but the pressures are quite high! If 15,000 psi were applied to anything beyond a bathysphere or other special pressure vessel..the end results would be catastrophic collapse or....explosion. In essence, a gun barrel/chamber forms a high strength pressure vessel and how it withstands the extreme pressures are due the fact that the bullet begins to move instantly upon ignition, and constantly increases the volume of the cylinder as the gases expand and then decay rapidly at the time when the bullet exits the bore. If the bullet doesn't move...a ruptured barrel/blown action results.....pretty simple!

Before the bullet exits and while the expanding gases are exerting their force on the bullet's base, chamber walls, bore, etc., it is also working against that gascheck. That thin cup of gilding metal (an alloy of zinc and copper) literally gets the urine mashed out of it. It expands as far as the bullet base and the bore will allow it to. The soft cast bullet obturates as well, swelling to the limits of the bore walls.....and in effect, pressure welds the gascheck and bullet base together. Once free of the bore's restrictive boundaries, the gascheck might....but not always, depart from the bullet. I cannot prove, or disprove, that is affects the bullet's flight. While it can be surmised that bullets free of the gascheck will have different flight characteristics than those with the gascheck still attached.....I cannot prove it or disprove it due to the fact that I have never been able to recover intact bullets down range....at least enough to say that all arrived on target wearing or not wearing, the gascheck.

In conclusion; considering the extreme forces applied to the gaschecked bullet during the launch sequence, I doubt very damned seriously that the looseness of the attached gascheck amounts to anything worth consideration.

I about shed my gascheck seeing Jump posting again. I reckon you came out of that corner. Good to have you back.

Oh yeah, I agree on the gascheck theory or yours. Only thing I can add is the gas pressure centers itself on the base of the bullet. Felix will attest to that.

Joe

[Jumptrap]

Hey Joseppi!

Being ignorant of many things and not in a position to argue (discuss) the centering of a gaseous column in reference to a piston in a cylinder (bullet in the bore), I won't go out on that limb. I would tend to think, however, that a column of gas emits itself equally in all directions upon the surfaces it is in contact with.....maybe that equates to 'centering'....I just don't know.

[BruceB]

My problem with loose gaschecks mainly involves just one mould, a Lyman .45 rifle type whose number escapes me just now.

In the pious belief that pressure (my friend, right?) would eliminate any real trouble in using a loose-fitting check, I loaded and fired quite a number of these in various .45-70 loads. Obviously, they made the trip down the barrel with no problem, but IMMEDIATELY departed from their bullets once they were in the open air.

The parting-of-the-ways was so immediate that the chrono screen supports, at nine feet from the muzzle, were BADLY chopped-up by the errant gaschecks.

Since this phenomenon became evident, I've been using red loctite to secure the checks to the bullets. It seems to work, and I'm not getting all the chunks blown-off the chrono supports.

This is all just to say that we should not depend on pressure to KEEP the gascheck on the bullet after it leaves the barrel. Also, I really dislike the idea of checks departing at random once the bullet is clear of the muzzle. It's an inconsistency, and as such I prefer to avoid it like the plague.

[felix]

Yea and Nay, Jump! Centering only occurs when the piston is in motion. This is how jet/rocket engines work, by a vector force pushing the piston into the direction (centering) of movement. If no "piston", i.e., no hole in the balloon, there is only equal pressure throughout the cylinder. Years have been spent on computer programs, to move vanes for example, to keep the force vectors in line for these motor applications. ... felix

[Bass Ackward]

I ask because I cast some boolits yesterday from my new LBT - .357 180gr gas check. I use Hornady gas checks. After being sized the checks are still not tightly installed and I am able to take them of with my fingernails?!?



Much good advice already. More food for thought.

It's not really what the before is like as much as the after. So it depends on how much your ultimate sizer (barrel) is sizing and how much lead your rifling displaces.

So much can be learned by just having a bore diameter sizer in calibers where a big difference is or could be found. And recovering bullets can also shed light here. 357 is one of these bores as bullets often drop at .360 or more on many molds and may exit the tube at .355. The sizer answers many things including the check question.

Most LBT designs are greatly affected by extra sizing because of the radius lube grooves and wide bands that can drop lube capacity VERY quickly if they have to be sized too much over the diameter for which they were cut. Which is another reason his heavier designs shoot better as they usually have another lube groove to work with over his lighter designs that can become lube starved if pushed.

At least the shank is usually straight and long enough on LBT designs to allow the check to creep forward as it sizes providing more surface area contact with the shank.

[Bret4207]

My problem with loose gaschecks mainly involves just one mould, a Lyman .45 rifle type whose number escapes me just now.

In the pious belief that pressure (my friend, right?) would eliminate any real trouble in using a loose-fitting check, I loaded and fired quite a number of these in various .45-70 loads. Obviously, they made the trip down the barrel with no problem, but IMMEDIATELY departed from their bullets once they were in the open air.

The parting-of-the-ways was so immediate that the chrono screen supports, at nine feet from the muzzle, were BADLY chopped-up by the errant gaschecks.

Since this phenomenon became evident, I've been using red loctite to secure the checks to the bullets. It seems to work, and I'm not getting all the chunks blown-off the chrono supports.

This is all just to say that we should not depend on pressure to KEEP the gascheck on the bullet after it leaves the barrel. Also, I really dislike the idea of checks departing at random once the bullet is clear of the muzzle. It's an inconsistency, and as such I prefer to avoid it like the plague.

If Uncle Bruce says it can happen, I believe it. I'll consider myself lucky not to have had that happen to me!

Jump, you verbose devil you! Must be the wife got you a a dose of good humor. Well done.:drinks:

[MT Gianni]

Great thoughts. Since I have had beat into my head by a couple of instructors that pressure is resistance to flow, I think at the end of the pressure chamber [barrel] there is no more resistance. You will experience a "pressure wave" from the effects of the bbl psi, and the bullet speeds because of the momentum put into it from the psi in the bbl, but there is no significant pressure 10' from the bbl so gas checks are free to do their own thing. If the bbl has sized them to the base they may stay on but if not they can certainly leave in a random pattern. It is certainly better IMO if they stay on.

[Jumptrap]

Yea and Nay, Jump! Centering only occurs when the piston is in motion. This is how jet/rocket engines work, by a vector force pushing the piston into the direction (centering) of movement. If no "piston", i.e., no hole in the balloon, there is only equal pressure throughout the cylinder. Years have been spent on computer programs, to move vanes for example, to keep the force vectors in line for these motor applications. ... felix

Brother Felix,

I would love to hear you expound upon gas volumes and the associated plus/minus exponential effects as area increases and/or decreases within the (pressure) vessel. Interesting subject! Being physics ignorant is a sad way to live one's life...as I have done.

[felix]

Brother Felix,

I would love to hear you expound upon gas volumes and the associated plus/minus exponential effects as area increases and/or decreases within the (pressure) vessel. Interesting subject! Being physics ignorant is a sad way to live one's life...as I have done.

I wish I could, Mark, in English terms. That's why the earlier philosophers were hell bent in coming up with a universal language understood by all. They finally came up with something we call mathematics. As you know, the math constructs have been expanded gradually over centuries to better explain nature, which is math's only purpose, really. Did it start during the pyramid days? Don't know. What about the star gazers? Were they the first "inventors" of math? To me, it's a miracle that math had been expanded to manipulate DNA. Not to mention, who/what/when/where/why someone was given the idea of DNA as something to describe the content of, and evolution of, living matter?

Give me a narrowed down clue on what you are thinking and I will try and help. The above paragraph is basically BS and is used to skirt your issue which is too broad for me to explain within reason. ... felix


Mark: google "nozzle design" and you will get an idea. ... felix

[Gunslinger]

A lot of usefull advice, thank you all.

I use a RCBS sizer and RCBS dies! My Lyman dies don't perform well in the RCBS.... a phenomenon I think I've read about somewhere before.

I was given a "Lyman gas check installer" a while back, but couldn't see where it could possibly go into the RCBS sizer. And was told at the range that I don't need that strange thingy I was babbling about. So I just installed them without - maybe that's were my reloading boat started to take in water?? However I have some 158gr SWC RCBS bulllets where the same checks (from the same batch) go on tight and nicely...

To anneal them I basically I just heat them with a small blow torch untill they turn rose in color and then just let them cool off?? Don't need to dump them in water right?

[RayinNH]

Gunslinger, the gas checks or copper in general can be annealed by heating red hot and either air cooled or water cooled. I water cool and then clean the checks off in some Birchwood Casey case cleaning liquid. It removes the discoloration from the heating process and the scale that forms from heating them. Others on here I believe seal the checks in a cast iron pipe nipple or elbow with a couple end caps and a small piece of paper in with the checks. The paper burning inside eliminates the oxygen thereby preventing oxidation. I've never tried the pipe method, because the liquid method is so simple...Ray

[HORNET]

Gunslinger,
The gas check installers that I've seen are intended to set on top of the die nut on the lubrisizer and are intended to allow using the sizer's leverage to press a tight fitting check onto the shank and keep it square to the boolit's axis. Never tried one so I don't know if they actually work.
Annealling the checks might help by reducing the springback but I'm not sure you have a problem. Is the check still loose after the rifling engraves it? Betcha not. Try recovering a few and see if they stay on and if their still loose.