thoughts on gas checks... where is that line, where you need them ???

[Magnum Wheel Man]

so I load a lot of different calibers, many with cast bullets...

... right now I ramping up for a "wildcat" 45 Black powder Magnum in a strengthened gun, that can shoot smokeless loads... the case is a standard 460 S&W case, that I'm knurling the head stamps off of... the loads will be average to just over factory 45 Colt loads using bulky powders like Trailboss, maybe AA 5744, IMR 4759, or similar... while I doubt I'll need a gas check, got me thing "just where to you "need" to use a gas check???"

does it relate to pressure, burning temp of the powder, volume of powder??? or something else, or a combination of several...

I understand "why" just don't know the forsures about what changes cause you to cross that line...

[Paul B.]

If a bullet is designed to take a gas check, I use a gas check. Plain based bullets get shot at lower velocities as that is what they're intended to be used at. THat's worked for me since 1949. No use changing now.
Paul B.

[Magnum Wheel Man]

so to better explain... if you were going to shoot a 454 Casull... ( hot rodded 45 Colt ) down loading at 45 Colt levels shouldn't require a gas check, as the Casull is nearly identical to the Colt case... as we go up in grains using the same powder to 454 Casull pressures, what forces the use of the gas check 1st... just the velocity of the bullet, ( leading from forces against the rifling ) the pressure of that particular powder ( if I chose a powder with lower pressures, but the same velocity ??? ) the volume of powder & or the heat from that source of powder???

if I chose to use a 460 S&W case( just a longer 45 Colt case ), & Trailboss powder... it's likely, that even with a compressed load ( which you shouldn't do with Trailboss ) there will be other more efficient 45 Colt powders that will push higher velocities, am I likely to see leading from the actual mass of the charge ( or the energy available in the powder charge ) or from the velocity of the bullet, or ???

[loademwell]

I asked this type of question on the Cast bullet part of these forums.
In a nut shell, the advise that seemed to be said the most is 1500 fps... If its under that speed no need for gas check. If its over that speed, gas check it.
Not sure what molds you have or going to get, but when I look at Lee molds, they don't really give you a choice.
If you buy a 9mm die, its not a Gas Check, if you buy one for 30-06 they are all gas checked.

Hope that helps a bit for ya.

[Magnum Wheel Man]

thanks for the replies... I'd guess the hardness of the bullet also makes a difference... the only time I've had leading in the past, was with swedged soft lead bullets, never with a hard cast bullet... but haven't pushed a cast bullet to the hot side of the recipe without a gas check either

[adrians]

What Paul B said ,if it's designed to take a GC I use one and for shooting/ plinking below 1600 fps I will use a Plain base bullets.

Over the last few years I have leaned more and more to shooting at velocities around 1200 or below so a couple of the "custom moulds" I have I asked the maker to cut the gas check shank out making them a plain base bullet ,.

The 311407 and a 316299 are good examples and shoot/plink great....

[243winxb]

A BHN of 18 would be ok up to a pressure of about 23,000 PSI without a gas check. Then there is PLASTIC DEFORMATION to worry about. The PSI (pressure) and BHN (hardness) of the alloy is what you look at. Pressure determines what is needed. Slow burn rates of powder are better than fast. Many other factors come into play. Bullet diameter, lube, type of rifling, alloy. No one will agree on any 1 set of rules. So i suggest buying a Lyman cast bullet book.

[Magnum Wheel Man]

I may have it... will have to look & spend some time reading...

I guess I've always been confused at what actually caused the lead to deposit on a barrel...

melting lead from the base of the bullet, exposed to the heat of the powder???
friction from the sides of the bullet forced into the rifling???

melting base, seems at 1st look, like the only thing a traditional gas check would cover...
hardness of the bullet, & lube choice would seem to cover side scrubbing...

however I recovered some hard cast bullets, that were fired at lower velocities, into a snow bank this spring, from a 44 American Bulldog... I didn't crony the loads, but suspect only around 600 fps... the recovered bullets, originally flat based, showed signs of a "skirt" around the outer edge of the base... I presume this was from getting dragged into the constricted rifling of the barrel ( skirts were visible on all bullets & maybe .010" - .015" ) there was no visible leading in the barrel

so I suppose a copper gas check could also support the edges of the bullet, with the pressure of the powder behind it...

I may have to find that book, it's piqued my interest...

[243winxb]

Lee has a chart with there hardness tester, hard to see. But pressure & BHN can be seen if inlarged. Many do not agree with the chart. http://www.realguns.com/archives/118.htm

[HiBC]

This is not science,but it is experience.Super Blackhawk full power H-110 loads .

I had the Lyman 2 cavity Keith what? about 245 gr mold,gas checked..I got tired of seating checks.Set up the mold in the Bridgeport,bored out the mold to eliminate the check on 1 cavity.

The bullets were cast of wheel weight.No advantage to have a gas check.

I cut the other cavity..IMO,.checks are a waste with a 240/250 gr 44 Mag

[reloader28]

In my playing around, speed has nothing to do with it.
Its has to do with load pressure and bullet diameter.

A faster powder will make more pressure with less speed and vice versa.
If I go bigger diameter, then I can bump up the load some more and use a little softer bullet.

[Unclenick]

I'll move this thread to the cast bullet forum where it is a better fit.

Gas checks do exactly what their name implies. They stop gas from escaping forward around the bullet. This is to prevent gas cutting of the bullet base, which is one major cause of leading, as the lead blown off sprays against the bore. It happens mainly when a bore has tight spots, and the bullet fails to spring back to full diameter after passing through one. It's also possible for lead bullets to enter a bore slightly off center, but the harder gas check tends to re-center the base to avoid gas cutting around the side making poor contact. It's also possible for a rough bore to tear enough lead off a bullet to let some gas squeeze through, particularly in the corners formed where the lands meet the grooves and it requires the greatest upsetting pressure to get a good seal.

In general, if you have a smooth bore of either uniform dimensions or tapering slightly narrower toward the muzzle, you can run cast bullets into it with pretty good pressure. Elmer Keith developed the .44 Magnum with 16:1 tin-lead.

As to what velocity you can drive a cast bullet to, that can't have a fixed answer. Most of the bullet deformation and stripping happens when the pressure peaks. This is when the bullet has only moved an inch or so forward, depending on the powder. If you have a longer barrel after that point you will get more velocity without more stripping or leading unless the bore is rough and can file lead off. It's really a maximum combination of peak pressure and rifling twist that you have to mind.

The main thing for most folks is just to get their bore smooth and to make sure their revolver chamber throats are uniform and bigger than their barrel groove diameters by at least the size of the bullet to half a thousandth more.

[totaldla]

If you want to skip the hassle of load development to avoid keyholing/leading then use a gas check. The downside is the hassle of the gas check.

[salvadore]

I use GCs on three cast bullet rifles 8mm mauser, 94 32 win. spec. and a Marlin 32/20. Haven't done much with the Mauser yet but the 32 win. 1600/1700fps gives decent 50 yd groups for my poor eye sight. THe 32/20 is scoped and the 115 gr. bullet @1800fps+ can deliver remarkable groups. I shoot a 92clone .45 Colt with non GC bullets @ 1350fps and it does as well as my 32 spec. info only

[iraiam]

I gas check cast bullets for my .357 and 44 magnum, and even one bullet for 9mm. I do this so I can shoot 1 bullet/load out of multiple handguns without having to vary the diameter of the bullet for the specific gun. I did have a few minor leading issues trying to use a standard bullet diameter with multiple guns in the same caliber, gas checks was the easier fix.

I size to .356 for 9mm, .358 for 38/.357, .430 for 44 Spec/Magnum