View Full Version : Understanding Gas Checks
05-22-2008, 12:25 PM
I did a search, but. if you don't know what your looking for its realy hard to find it.
i am trying to understand gas checks? i know they are made of copper. i know it helps reduce fouling. can it help a soft bullet go out the barrel? with a gas check does the bullet need to have a high brinn test? lets say if all things were equal except the bullet hardness and you were shoot oh say a realy thick skinned huge hog. what would be the difference between a gas checked bullet and one that wasn't?
lee says something like: a bullet has to be so hard to go so fast. they even give the speed to match the hardness.
PLEASE any and all info would be great!
i want to learn as much as i can about them
THANK YOU VERY MUCH
05-22-2008, 01:06 PM
Given the same distance to target, same bullet diameter and nose shape, same bullet placement and same velocity, the hog will never know the difference between a plain based and a gas checked bullet.
Personally, I don't see any need for them for handgun cartridges up through .44 Magnum or hot loaded .45 Colt rounds. Lead alloy boolits subjected to heat treating or water quenching during the casting process will be plenty hard for those cartridges. Mixing WW (wheel weights) with linotype will also create boolits that are plenty hard. When properly sized and lubed, even relatively soft lead alloys will work well at 1200 - 1400 fps without gas checks. For my handguns (no Super Magnums), plain-based boolits are all that's required. Gas checks are merely an added expense.
Others here can give you a better idea of what velocity level in rifles dictates the need for gas checks. I use them for all my rifle boolits except for a couple of plain-based plinker-type boolits I cast for loads that won't exceed 1500 fps or so.
05-22-2008, 01:09 PM
Oh man, CB. You're asking a lot here and much of it is controversial at best....in other words, we don't all agree precisely how a GC works.
A gas check as you say is copper, can be brass and of lately, due to the copper prices, guys are making them at home out of aluminum pop cans.
The GC protects the base of the bullet. That's it's purpose in life. After the bullet exits the muzzle, it serves no useful function. When the cartridge is fired, powder/hot gasses hit the base of an unprotected bullet and an examination of recovered PB bullets will show the indentations of the powder granules and sometimes heat scoring depending on the burn rate of the powder being used. The GC prevents this and gives you a smooth, even base which leads to better accuracy.
When the ignited powder starts to move the bullet and the bullet encounters an obstruction either the bore or rifling, the bullet stops for an infinitesimal period of time. The base of the bullet is slightly deformed (bumped) and is upset to (hopefully) fill the bore and rifling and cause a tight gas seal. In the short time this is happening, propellant gasses blow by the base of the bullet and very small particles of lead are actually melted off of a PB bullet. This along with improper lubing, lead too soft and undersized bullets which preclude a tight seal cause leading. The copper GC provides a barrier between the bore and the bullet base and these particles don't come off the base. You still get some blowby the copper GC but any leading comes lead being eroded from the side of the bullet. The GC takes the form of the rifling and if you examine GCs that have come from bullets that have hit steel plates, you'll see the rifling imprint on the check and also the corner portion will be blackened by the gas blow by.
On a soft bullet, the GC's function is to merely protect the base of a bullet while in the barrel. It may act as a scraper somewhat and remove light leading but that's not its primary purpose.
GCs can be used with a bullet of any hardness of alloy.
Other than the improved accuracy caused by a GC, a hog wouldn't know the difference between a PB and a GC'd bullet.
The required alloy for any bullet will be dependent on the speed you desire to fire it at. Fairly soft alloy is good up to say 1200 FPS, WWs up to probably 1900 FPS and after that, you're looking at hard lino and other types of special alloys.
I've tried to answer your questions to the best of my abilities. Some of these other guys will weigh in here with additional information./beagle
05-22-2008, 02:18 PM
I've been trying to ween off of gas checks, they cost has increased tremendously in the last few years. Still, there are some cartridges that simply can't be fired without them. Yes, reduce the pressure and velocity and a plain base boolit will work, but if you want full cartridge potential, you need the check. I'm thinking here of my .454 Casull cast loads at over 1500 fps and 55K to 60K pressure, and some .224 cast fired at 2400 fps.
I've seen the proof that gas checks remove leading, but as Beagle said, that's only one of their functions.
05-22-2008, 03:14 PM
1. can it help a soft bullet go out the barrel?
2. with a gas check does the bullet need to have a high brinn test?
3. lets say if all things were equal except the bullet hardness and you were shoot oh say a realy thick skinned huge hog.
4. what would be the difference between a gas checked bullet and one that wasn't?
5. lee says something like: a bullet has to be so hard to go so fast. they even give the speed to match the hardness.
1. Absolutely it can. Or it can have no effect. Depends on the load, the gun, and if any problems result from the two variables. A GC can actually minimize barrel wear. Or not.
2. No, it doesn't. The advantage of the check is to allow softer (cheaper) mixes for the same velocity / pressure level. If you utilize it to do this, then you pay for the check. If you don't and you are properly matching the hardness to the pressure, you don't see any advantage to the check. If you gun is new and not broken in, a check minimises barrel wear and improves barrel dimensions at first, where a PB will alter dimensions for the negative.
3. It does if you load your bullets backwards for a really wide meplat. Otherwise, na.
4. Load consistency. I measured a plain based load I have with a 625 that is giving me headaches waiting for it to break in. Quickload predicted the velocity of the first shot at 746 fps at 16,000 psi. 746 fps was exactly what I got on the chrono. The 250th shot was chrono'ed again. Velocity was now 987 fps that Quickload predicted took 26,000 psi to achieve. This is over the maximum for this cartridge. That doesn't happen as often with a GC which allows longer use before cleaning. So if you don't like to clean your gun, and you don't have a chronograph to monitor what is going on, you can be constantly perplexed at the least or reaching a dangerous condition. (only minor leading was visible in the cone area.) So a GC can actually lower pressure for the long haul if gun strength or caliber is an issue.
05-22-2008, 07:45 PM
wow, this stuff is great!
i guess i should of told you guys i will be loading up a marlin 45/70, 350 grain and higher weights. i used a hog so alot of people could relate. where i live lead is scarce.
the closest metal yard is 90 miles. ww's are long gone. the best place i have found lead is at ace hardware. they sell 50/50 solder and the rest i either get from midway or on line. i have a chrono, i am saving up for a saeco brinn tester.
i like a full flavor ( haul'en butt) load. when i havest an animal i like to think i did all i can. to do make it a clean fast kill. cuts down on tracking
05-23-2008, 07:40 AM
Cold Bore, Suggest you consider Beagle & Bass to be as experianced as you could ask for, and that their words of wisdom are invaluable. That said, if you are shooting gas checked 457's it is my less than humble opinion that you are wasteing your time and money. Plain base, cast at about 18BH will stand up to just about anything you want in a 45-70. I took a very nice 250 lb. hog in Tex a few years back with a 405 Ohas PB and Lars White Lube over 26 gr. of 2400 in a #1 Ruger, at about 70 yds. 4 feet in the air and not even a snort. Big flat nosed blts. don't need to be driven like race cars. On the other hand, in all of the cals up to and including 30, I want a gas check for anything out of a rifle at much over 1200 regardless of blt. weight. Good luck!
05-23-2008, 08:17 AM
quite a lot of it has to do with the boolit design also.
flat base vs bevel.
there are alot of bevel base boolit molds that simply would be much better as either
a p/b or g/c design.
and a few that are fine the way they are, h&g #68.
the way i think of a g/c is that it protects the base of the boolit, i also like g/c
if the bbl has some porting.
and you are putting some oomph in there.
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