IMR 4227 vs S265?

[Ds J]

Goeiemôre mense, hoe verskil hierdie twee kruitsoorte? Hoe kan/mag/moet ek ladings aanpas?

(How do they differ, and how does one transfer a S265-load to 4227?)

[big5ifty]

By the old GS-Custom burn rate chart, they are equivalent.

For handguns, it's standard practice to reduce the charge by 5%, and work up, where load data is not available for that powder in that cartridge.

But why do you need to guess ? IMR 4227 is very well documnted in all the reloading manuals for all the calibers it's used in. Go straight to the load data for the caliber.

[Ds J]

Thanks, I am not schooled in chemistry. Please help with the following:

I am worried that equal burn rate does not necessarily means equal pressure etc, or that the density (weight) of the powders might differ. This could mean that 5gr of 4227 should be replaced by 3gr of S265 (theoretical example only!), but mankind's infinite wisdom persuades me to reload 5gr of S265, and then I have a kaboom situation.

(Loads are for the 410-2", which means everything needs to be researched, basically nothing available. General guideline is 10gr - 12gr S265; I got sufficient performance (1150-1250fps) at 12.5gr of S265.

[oafpatroll]

I'm not endorsing this in any way but some of it at least looks to make some sense.

https://castboolits.gunloads.com/showthread.php?240127-410-reloading-with-brass-shells-and-IMR4227

[big5ifty]

There is no load data for IMR4227 because it's too slow for 2" .410 shotshell.

If you have existing loads with S265, then you have proven that the slower powder is safe. Usually when something is not recommended, it's not safe.

The burn rate charts rate them as equivalent, which does not mean exactly the same, but it does mean that in the test volume, the two powders produced the similar pressure for the same mass of powder, hence reducing the charge by 5% is sensible as a start.

The test volume is usually a .308 case, which is why when the cases get bigger, the burn rate charts tend to differ markedly from actual.The burn rate is very dependant on the volume of the case.

Your .410 is miniscule, there is no danger of using equivalent mass of IMR 4227 instead of the known good load of S265.

[oafpatroll]

I've done a bunch of 12G load dev and had a bit done on my behalf by Somchem in the good old days. What stood out for me and was confirmed by the pressure results obtained by Somchem was that shotties are relatively forgiving. You'd need to colour much further outside of the lines compared to a rifle to blow a post damascus era one up.   

[Ds J]

@ oafpatrol & big5ifty:

Thanks a lot, it is comforting to know.

Loads for the .410-2" are very few and vry far between; often with powder not available in SA. The cartridge was overtaken by the 2½" shell during the 1930, and the 3" shell by the 1960's. I guess this is the main reason for so little data being available.

[Newton]

Loads for the .410-2" are very few and vry far between; often with powder not available in SA. The cartridge was overtaken by the 2½" shell during the 1930, and the 3" shell by the 1960's. I guess this is the main reason for so little data being available.

How old is the weapon ?
In what sort of condition is it ?
.410 is a straight wall cartridge ?
Is it not possible to ream the chamber to 3" and use normal .410 cartridges ? ( a fairly simple operation )
or
Is there some special reason that the shells are brass ?

IF the firearm is capable of handling modern 3" pressures then your problems are solved - just use modern cartridges.

Alternatively look at the different powders and loads for 2.5" and 3" cartridges - calculate the difference and deduct from those.

[Newton]

I've done a bunch of 12G load dev and had a bit done on my behalf by Somchem in the good old days. What stood out for me and was confirmed by the pressure results obtained by Somchem was that shotties are relatively forgiving. You'd need to colour much further outside of the lines compared to a rifle to blow a post damascus era one up. 

I would tend to disagree .. for the following reasons ...

What are the working pressures of a 3" 12 Ga shotgun ?

What are the working pressures of a .308 bottle neck rifle cartridge ?

What are the burn rate characteristics of powders used in shotguns ?

What are the burn rate characteristics of powders used in a .308 bottle neck rifle cartridge ?

Please explain how SOMCHEM calculated the pressures ? .. and what equipment was used ?

[Ds J]

How old is the weapon ?

In what sort of condition is it ?

.410 is a straight wall cartridge ?

Is it not possible to ream the chamber to 3" and use normal .410 cartridges ? ( a fairly simple operation )

or

Is there some special reason that the shells are brass ?

IF the firearm is capable of handling modern 3" pressures then your problems are solved - just use modern cartridges.

Alternatively look at the different powders and loads for 2.5" and 3" cartridges - calculate the difference and deduct from those.

The weapon is a 100-year old Belgian SxS in good to great condition with BP and nitro proof stamps. I use it to teach myself and my kids the basics.

The barrels are quite thin, and made to fire at a slightly lower pressure than modern 2½ cartridges. It is probably not wise to ream them open.

The cartridges are straight walled, or very close to it. I choose brass because it looks good Seriously though, it lasts much longer than paper or plastic shells.

I have done the calculations and need to swop powders due to availability. The best would be to test the loads in a lab - I could not get hold of Somchem's lab yet.

[big5ifty]

You can be sure that an equal mass of IMR 4227 will produce less pressure than the same mass of S121,  or whichever other fast pistol powder is normally used in shotguns.

The pressure of that load will not even expand the brass case it's in.

To test it, incrementally increase the weight of shot to the required load. Use a 1/10,000 micrometer at the base just ahead of the rim, before and after firing. There should be no case expansion at that point.

And to be extra cautious, test it in a modern .410.

[Newton]

The weapon is a 100-year old Belgian SxS in good to great condition with BP and nitro proof stamps.
The best would be to test the loads in a lab - I could not get hold of Somchem's lab yet.

Be interesting to look up those proof marks and what they actually mean - could tell you a lot ?
Does SOMCHEM's lab / s still work ?

[Newton]

And to be extra cautious, test it in a modern .410.

After Treeman's .. "Ooops" does one in fact actually still need to exercise caution ?   
It appears firearms have extra in-built safety margins ?