Powder Coating and gas checks...

[Idaho Sharpshooter]

Another question for the Masters of PC.

Okay, two.

1. For those of you who PC gas check boolits and shoot them at higher (1600+fps) velocities. Have you done any testing to see if the gas check is necessary?
I ask because, if the coating prevents leading, would you suggest the GC is necessary? The burn time on the base of the boolit is measured in nano-seconds before it obdurates and seals
the bore.

2. I have some NOE molds that I ordered with both GC and plain base cavities. Anyone done the PC and seen any difference is leading?
If not, it would be a savings not using the GC. I try to get a boolit that I need not size before loading

Thanks to all in advance, and I await your experiences.


Rich

[Smoke4320]

I have posted targets of at least 5 different calibers that were between 1500 and 1600 that shot very well pc'ed base bullets. IIRC 6.5x55, 308, 358 win, 45-70 and 458 socom
Was able to to push 95/5 308 to 1900 before I needed gas checks to keep accuracy (no leading accuracy went to pot) and got to 2100-2200 fps on the 358 JES rebore before gc was needed.

[popper]

You didn't state cal. or mould. Fit, a GOOD base and alloy are the key. PC isn't a GC, as a coating (lube replacement), it's gone past 3k without leading. 1600 is pretty easy, above that not so much.

[Motor]

I haven't had the opportunity to experiment with it yet. I typically shoot @16bhn alloy gas checked with tumble lube. In an attempt to maybe get some expantion, after I started powder coating I dropped the alloy hardness to 12bhn but am still using the gas checks. The load has maintained it's accuracy.

A better test may be the 12bhn .501" 440gr that I shoot from a 500 Smith&Wesson. The load is 27.5gr Lil Gun. I use these with PC and no gas check. So far I have only got to shoot 5 of them which may be too small of number to judge but they were accurate and did not leave anything in the bore.

Don't get confused about what the gas checks job is. It dosn't protect the base of the boolit. Think of it as a piston ring. It prevents blow by. The only reason it covers the base is for ease of use and manufacturing.

Motor

[Tracy]

The burn time on the base of the boolit is measured in nano-seconds before it obdurates and seals
the bore.

Yep. Also, long range target shooting distances are measured in microns.

[Beagle333]

Don't get confused about what the gas checks job is. It dosn't protect the base of the boolit. Think of it as a piston ring. It prevents blow by. The only reason it covers the base is for ease of use and manufacturing.

Motor

^^^This is a shooter who knows how things work.
+1!!

[williamwaco]

I load most handguns up to .44 Mag, .30-30 and .38-55 with cast bullets. I have never found gas checks to offer any advantage in any loadings I have used up to 2100 to 2200 fps.

Obviously I can't get there with handguns but I can get the .357 up to 1700 in my Win. 92 carbine.

[Markbo]

....It prevents blow by. The only reason it covers the base is for ease of use and manufacturing. Motor

And what is the danger (downside might be a better word) to blow by?

[P Flados]

Gas checks are proven to "extend the envelope".

They are however, just one "tool" on the shelf.

The best of today's Bullet lubes are probably able to support a good portion of the "full power" loads for magnum pistols and for rifles when everything else is perfect.

However, PC can probably support high pressure / high velocity cast boolit applications better than any traditional lube.

For me, PC was a "quick fix". It eliminated leading on lots of my loads.

Of course, the leading is just part of the story.

If the gun can take it, a given boolit can be pushed too hard even with PC. First, accuracy is compromised. Toss in another grain or so after you reach the edge of the useful envelope and boolits start to tumble.

This same progression occurs with traditional lubes. I think it is very likely that the "edge" is a function of both pressure and velocity. Go with a slower burning powder and you can have more velocity.

If the alloy is not right, this is part of what limits performance. I feel this is an area ripe for better understanding.

I have several gas check molds (Lee C309-150-F, C309-170-F, C358-200-RF). I made & used some checks for the 30s and then gave up on them. Since then I have been shooting all three without checks.

The C358-200-RF was able to handle full power 357 max ok without a check with straight COWW.

On the other hand, I have been able to push the 30s "over the edge" in my 30 Herrett with straight COWW.

I am trying other alloys to see if I can "extend the envelope" while staying checkless.

[Beagle333]

And what is the danger (downside might be a better word) to blow by?

As the hot gases jet along any gap between the boolit and barrel, they cause gas cutting. This superheated jet melts some lead and deposits a fine mist of molten lead on the barrel walls ahead of the boolit, which then irons the lead into the grooves and onto the walls of the barrel as the boolit passes.

[Markbo]

As the hot gases jet along any gap between the boolit and barrel, they cause gas cutting. This superheated jet melts some lead and deposits a fine mist of molten lead on the barrel walls ahead of the boolit, which then irons the lead into the grooves and onto the walls of the barrel as the boolit passes.

And this is exactly why I am confused on the whole GCing PCd boolits issue. The PC acts as a high temp cover so that this does not occur. That worry is eliminated as is evidence by all these reports of high velocity rifle rounds without GCs. It is not a lube...it acts as more of a jacket. Would you GC jacketed bullets?

[Beagle333]

It acts more as a lube. It makes the boolit slippery. It makes it slide down the barrel, somewhat similar to how Teflon is a dry coating that makes your eggs slide out of the pan.
It is also made of melted polyester..... Melted polyester that is 1/1000 of an inch thick. That isn't a high temp cover. It is a slippery polyester cover.

But test them for yourself and maybe it will work for you. That would be great!

[Motor]

I think Beagle333 covered it pretty good. Just as powder coat is not a substitute for good alloy (it doesn't make the bullet any stronger) it doesn't protect it from high pressure, high heat gases that may escape around it.

I think there are 3 basic reasons lead fouling occurs (considering the bore is in good condition) in no particular order:
1) Lack of lube. Friction between the lead and the steel bore.
2) Allow strength to week. The boolit skids down the bore instead of riding the rifling.
3) Blow by. As described above, hot high pressure gas cuts the boolits as it leaks past leaving molten lead deposited in the bore.

There are many ways to prevent those 3 basic problems from occurring and as things like powder coating comes along the "old tried and true" rules begin to bend. So you really have to take a try it and see position.

Just keep the lead removing tools handy.

Motor

[Markbo]

Sooo... I am trying here guys, really I am... if you have blow by because of a very slightly undersized bullet, or do to a properly sized bullet, simply pushed to high velocity, do you believe the hot gas will melt through the coating and melt the lead still???

If so... why isn't that happening with the higher velocity rifle loads?

[Motor]

It does happen with higher velocity rifle bullets. If it dosn't then you must have a strong enough alloy and a good enough fit to prevent it.

You have to experiment and see basically what you can get away with. This is also why it's sometimes difficult to determine the exact cause of lead fouling. When you do have problems you often have to go by trial and error to get it correct.

This is why everyone suggests slugging the bore as a first step. Fit is #1. It very hard to rely on obsturation alone to create a good fit. Once you have good fit you only need to focus on alloy strength and lube to achieve your goals.

Motor

[flyingrhino]

I cast a Lee 312-155-2R for my 300 blackout. I put a copper check on them from day one. I'm pushing them right around 2000 fps and have excellent accuracy and no leading. I've never tried them without checks. I figure why mess with something that works so well.

[Maximumbob54]

I think this is boiling down to just try it and see if your load with your bullet in your gun works for you. I've found shooting checkless bullets with exposed shanks to be spotty once you go past plinking velocity. But then someone will say it works for them. I've had only limited success shooting coated bullets at rifle velocity without checks while some have had success. Coatings are just another facet of what works in one gun may not work in the next. For a while I was loading two different 9mm bullets in .356 and .358 to get them to fit in one chamber and get the other to not lead. Coatings are just another example of what works for one may or may not work for another. Personally I still enjoy the testing and reading about what has or hasn't worked for someone else. And I'm stubborn enough I might see if I can find a way to make it work for me.

[Markbo]

Luckily for me, my personal use is in handguns only and I simply never push any caliber extremely high. I might try it with coated bullets and see what happens. I am lucky that .480/.475L loads at 1000fps will penetrate plumb through Bison I have no need to push them - or me!- too hard. And since .45 colt will go end to end through a whitetail at the same velocity I am in pretty good shape.

[JHeath]

Just guessing, but I think the gas check on a pc boolit might be wanted for the same reason as a good barrel crown. It provides a concentricity at the boolit base as the gas explodes out the barrel around the emerging bullet. If the crown is bad, the assymetrical gas jet can tip the bullet. I suspect that a high velocity gc boolit with no gc installed could be destabilized by the gas bursting ahead of the base and past the lowest driving band, as the boolit leaves the barrel.

I.e. a gas check provides a filled-out boolit base, just like the well-filled-out corners you would want on a plain-base cast boolit.

[Eddie1971]

That guy Elvis on YouTube has been Powder Coating 300 BO and .556 for his AR using Winchester 748, and keeping the MV around 2,500 FPS and no Gas Checks. He's had no leading or accuracy issues.