Gas check below neck/shoulder junction ok ?

[Swamplord]

I have used cast bullets with gas checks in my revolvers for many years but have limited experience running them in bottle neck rifle cartridges..... now I have decided to use them in a .500 cal wildcat rifle cartridge i am designing, have .50 cal mold on order with max shank of bullets .500" from base to crimp groove....
I don't want an excessively long neck on my wildcat but am concerned about the gas check hanging below the neck/shoulder junction..... is it a valid concern or is a normal loading procedure and I shouldn't worry about it ?

My worry is the gas check may get peeled off as the bullet is released from the case neck ,

[Smokin7mm]

I always try to keep the gas check within the neck on bottleneck cartridges.

Bret

[badgeredd]

I have used cast bullets with gas checks in my revolvers for many years but have limited experience running them in bottle neck rifle cartridges..... now I have decided to use them in a .500 cal wildcat rifle cartridge i am designing, have .50 cal mold on order with max shank of bullets .500" from base to crimp groove....
I don't want an excessively long neck on my wildcat but am concerned about the gas check hanging below the neck/shoulder junction..... is it a valid concern or is a normal loading procedure and I shouldn't worry about it ?

My worry is the gas check may get peeled off as the bullet is released from the case neck ,

IMHO, with crimp on gas checks that fit, there is less likelihood the gas check will separate from the bullet in the case. That being said, it is generally accepted it is a good practice to keep the check contained in the neck. I always make sure at least the top of the check is contained by the neck. Is it necessary? I don't know positively that it is, but I figure that there are enough experienced members here on the board that recommend keeping the check in the neck that I feel it is probably a good idea.

Define "excessively long neck." The primary attribute of a neck one caliber long is bullet support with cast bullets. My experience has shown me that a short neck with cast bullets is more often a detriment that having a longer neck to support the bullet in fixed ammo better. Cartridges like the 35 Remington have a shorter neck and can be made to shoot fine, but if I were designing a wildcat, I'd do as I always have in the past and use a neck one caliber long. I'd also keep the throat/free bore to a minimum and tailor the area to fit the primary bullet I intend to use.

My thoughts which can be flawed.

Edd

[RickinTN]

This is my theory, and I may be all wet, but here goes. Upon firing the check is not likely to separate from the bullet because it has the pressure of the burning gases pushing it into the bullet. After it leaves the bore and the pressure is no longer acting on it is a different story. The issue, as I see it, with having the check and part of the bullet below the neck is this; As we all know cast bullets can and will obturate. If some of this obturation takes place on the base of the bullet and the gas check while it is un-supported by the case neck (and it is not likely to be symmetrical) the bullet must be re-swaged to size when entering the case neck and passing through. As we all would agree the base of the bullet being square and perpendicular to the bore is one of if not the most important aspects of cast bullet accuracy. Because of the inertia of the bullet obturation takes place from the rear of the bullet forward. We all would agree that static and dynamic fit of the bullet to the throat and leade is paramount to best accuracy and I would contend that static and dynamic fit in the case neck is just as important. With the few custom molds I have and the production molds I use as well I strive to keep at least the front edge of the gas check in the neck and consider the complete check being contained in the neck being even better.
Just one guys thoughts here.
Good luck with your new cartridge!
Rick

[gtgeorge]

Doesn't the case neck expand before the bullet clears the case? That is my understanding because if it didn't you would have serious blowby around the case like shooting a very light load does that doesn't sufficiently expand the case.

As for the gas check issue, I am knew to the gas check world and just recently started loading rifle cartridges with them and have been watching these discussions. I will do some testing for myself with bullet recovery for examination since I worry about the powder being on the sides of the bullet and maybe even pressed into the lube as it travels out of the case.

I do not see the check coming off or causing any trouble if it did but I know there are some very experienced members here that know more from first hand experience without speculation. I haven't found that information yet myself and getting ready to load in a 7mm mag that seems to require the check to be inside the case.

[RickinTN]

In some instances such as the 7mm Magnum and the 300 Savage comes to mind as well it is difficult to keep the gas-check in the neck depending on the throat and leade of the rifle. In the case of the OP if I read it correctly he is designing his own cartridge and can take such things into account and therefore accomodate them. Sometimes you just have to do what you have to do.
Take care,
Rick

[RickinTN]

Doesn't the case neck expand before the bullet clears the case?

Yes it does. And the ideal situation here is for the case neck to expand only enough to release the bullet and no more (.0005" or so?) This situation is difficult at best to achieve and is usually only accomplished with special "tight neck" chambers and neck turning of the cases to properly fit. These are expenses and trouble that most of us won't go to but they could be done. That portion of the chamber neck that extends past the neck of the case is also a problem area because the bullet wants to obturate into this void. This can also be taken into account with longer case necks or a special chamber.
Rick
Rick

[dragon813gt]

I load them below the neck all the time for a couple 300 Savage rifles. It's pretty much impossible to keep them contained in the neck and have them feed from a magazine. I have had no issues doing this. I realize the potential problems and am willing to assume the risk. If I was designing a cartridge I would make sure the bullet would stay in the neck.

[Larry Gibson]

With GCs seated below the neck;

Gas cutting of the bullet above the GC.
Riveting of unsupported bullet base (depending on alloy hardness and load used).
Even a crimped on GC can be peeled of shank by case neck if bullet base rivets.
Deformed base (not square with axis center of bullet) possible.
Exposed lube blown/burned off bullet before the bullet enters the barrel.
Exposed lube can contaminate powder.

All the above and then some can be detrimental to accuracy if they occur. That is why most of us strive to use a cast bullet design that keeps the GC (at least the top of the GC) insider the bottom of the case neck. With some loads and some cast bullets seating the GC a minimal amount below the case neck doesn't seem to hurt accuracy much but unless the user has tried a properly fitting designed cast bullet for the cartridge used we really don't know.

Larry Gibson

[selmerfan]

I have experience with cast boolits in .260 Rem, .30-06, .308, .30-40 Krag, and .30-30 in the rifle world. The only one that keeps the gas check within the neck in my rifles is the .30-40 Krag with 311299 boolit. I routinely dig my boolits out of the sand that I shoot into and the large majority have the gas check attached. I'm using Hornady and Blammer's checks. It is a good idea? Sure. Is it required? No.

[tomme boy]

Have you ever seen a rifle blown up from a check coming off? I have not. Anyone else. I don't like to stick them into the case below the neck, but sometimes you have to.

[UBER7MM]

....I don't like to stick them into the case below the neck, but sometimes you have to.

The 8mm Karabiner mold is a big offender of this....

[head for the hills]

With GCs seated below the neck;

Gas cutting of the bullet above the GC.
Riveting of unsupported bullet base (depending on alloy hardness and load used).
Even a crimped on GC can be peeled of shank by case neck if bullet base rivets.
Deformed base (not square with axis center of bullet) possible.
Exposed lube blown/burned off bullet before the bullet enters the barrel.
Exposed lube can contaminate powder.

All the above and then some can be detrimental to accuracy if they occur. That is why most of us strive to use a cast bullet design that keeps the GC (at least the top of the GC) insider the bottom of the case neck. With some loads and some cast bullets seating the GC a minimal amount below the case neck doesn't seem to hurt accuracy much but unless the user has tried a properly fitting designed cast bullet for the cartridge used we really don't know.

Larry Gibson

Explain riveting please?

Clark

[Swamplord]

Thanks to everyone who responded, I knew I could count on you guys to help me solve this dilemma....

I appreciate the input and have decided to alter the case neck length on my wildcat from .450" to .500" in order to properly seat the bullet without hanging below the neck/shoulder junction..... the reamer has not been cut yet so I had this bit of time to verify and confirm my dimensions for reamer production, my .50 cal mold is being made to my specifications by Tom at Accurate Molds..... I used a couple of his designs and altered some dimensions to create the bullet shapes and weights I have in mind for this wildcat, Tom has added these designs to his catalog if anyone is interested........
These two cast bullets will also be used for my 500 S&W Mag revolver.........

.502" 500 gr bullet, http://www.accuratemolds.com/bullet_...=50-500M-D.png

.502" 555 gr bullet, http://www.accuratemolds.com/bullet_...=50-555M-D.png

The wildcat I am working on is based on the 338 Norma Magnum necked up to .500", I also will be using Lapua made 423 Dakota brass necked up, & another option that I have verified... is using 338 Lapua Mag cases with the neck cut off and COW fireformed,

measured case capacity is right at 117 gr of h20 with the .450" neck and will be a few grains less with the .500" neck, will verify as soon as I can find the time to tweak the case neck down a bit....
Expect velocity with 500 gr bullets at 2400 fps and with the 555 gr bullets at 2300 fps....
I have had excellent results with my 375 cal wildcat based on the same cases, I managed to exceed 375 RUM velocities with a 300 gr Accubond with 5 gr less powder and a shorter coal that fits the AICS detachable mags, can't wait to to see what the 50 cal will do, should be nipping on the heels of the 500 Jeffery ! ( also have a 416 cal version, reamer is in my possession & waiting on a barrel)

I do have some photos of my cartridge design if anyone cares to see it, just not sure if it's ok to post on this gas check thread

[RickinTN]

Explain riveting please?

Not to put words in Larry's mouth, but it is the obturation of the base of the bullet before it enters the case neck as mentioned in post #4 above.

Rick

[Dan Cash]

I have been trying to get a 99 Sav. in .300 to shoot PP bullets at full velocity with no luck. My mould options on hand are a .31141 and a 311291, both gas checked bullets and gas checked with home manufactured copper checks. Patched bullets were fired both with and without checks with no discernable difference in performance. To get the bullets in to the magazine and in to the chamber, the base of the bullet was seated just below the juncture of shoulder and body.

Recovered bullets did not show any gas cutting but all had serious peening on the side of the bullet from the base to the line indicated by the bottom of the case neck. Bullets fired with out a gas check were peened equally on base and side. Gas checks stayed with the bullets about 95% of the time and separation, when it occured, was at the target.

Group sizes with these bullets ran 10 to 14 inches at 100 yards though one group with the 31141 ran slightly over 2 inches. I don't know why and could not repeat it. I have a .30-40 M1895 Winchester that will give 2 inches or less on demand with a 215 grain Accurate bullet where the base is contained inside the case neck.

Since the OP is building a wildcat, my advice would be build the case with enough neck to hold the heaviest bullet he wants to shoot. Life is simple that way.

[Larry Gibson]

Have you ever seen a rifle blown up from a check coming off? I have not. Anyone else. I don't like to stick them into the case below the neck, but sometimes you have to.

"blowing the rifle up" isn't the problem; p*ss poor accuracy is.

Dan Cash's example (above post) is a classic example that occurs with both PP'd and GC cast bullets. Sometimes with a certain load you can still have reasonable accuracy but many times not. His is a perfect example of the "not".

Larry Gibson

[Larry Gibson]

Explain riveting please?

Clark

The base of the bullet flattens out (swages) to a larger diameter because of the inertia of the bullet and resistance to engraving on the rifling and twisting before the bullet base enters the neck and is supported. Also happens if the case neck expands too much from too much clearance in a large chamber. After swaging out getting swaged back down is detrimental to accuracy. The GC may also get peeled of the base completely or partially in this process. GC is blown out of the barrel and having the GC stuck in the bore is not something I get concerned about. Inaccuracy does concern me.

Riveting most often can occur with fast burning powders under softer cast heavy bullets.

Larry Gibson

[abqcaster]

So, this seems to beg the question: If the case neck can "peel off" the gas check, why doesn't the chamber throat do it? Please for give my ignorance if this is obvious or well known.

[Whiterabbit]

its not obvious. Nor would riveting peel off the check. It might if the source of bullet movement was in front of the bullet, but the driving force is behind it. if the base of the bullet expands before it hits the neck, ALL the force to keep the bullet moving is behind the bullet (and the sides of whatever is exposed below the neck). Take that away and the bullet just stops moving.

SO the gas check is still being acted on. Frankly it has to be since that is the SOURCE of the riveting to begin with!

Thus, the most likely result of that is that the bullet gets sized as it passes through the neck. Throat, rifling. etc.

Which is also probably why you (the collective you) have never heard of pulling a bolt and looking down a bore, or looking into a fired case and seeing a gas check in there. Just doesn't happen.


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I make zero comments on accuracy issues. Only the idea of stripping off the checks.