Pressure measurements for 577 450 Martini cartridge?

[Idz]

Has anybody done pressure measurements on the martini henry? A kind of standard load people seem to using is a PP .459 bullet weighing 400 grains, 70 grains of Fg or FFg, cotton or dacron or kapok filler, and grease wads. Anybody have any pressure data on that or any other MH loading?
My internet searches reveal a lot of talk and opinions but almost zero blackpowder data.

thanks

[Tackleberry41]

I saw some somewhere in a forum somebody posted. But its BP so dont think its really going to be any different than say a 45-70.

[martinibelgian]

Looks like you have your info wrong - usually, the bullet is a 480 grains at .470, 80-85 Fg - and that would be about 12,000 psi

[Tackleberry41]

Theres not really a set load for those things. The British made ones usually require bigger than .459, while the Nepalese guns are are tighter bored, and vary alot. The original charge is about 80-85gr, while the converted 24ga cases are closer to 110gr. Unless you use some sort of spacers to bring the capacity down.

I have used 500gr and 405gr in mine.

[Idz]

Folks complain of shoulder bruises when they use the military loading of 85gr with 480 gr boolit so most folks have settled on a 'standard' load of about 70 gr and about 400gr boolit. The fluffed cotton acts as a filler to take up the extra space in the cartridge. Some claim the cotton launches fireballs but I've seen no evidence of that in 25 shots.

Where did the 12000psi number for the 85gr/480gr load come from? Blackpowder is tricky stuff to calculate. I do know that the burn rate as a function of pressure has a crossover point at about 4000psi. Below that BP burns faster than bullseye, above that bullseye burns faster.

[sthwestvictoria]

Has anybody done pressure measurements on the martini henry?
thanks
Yes:
http://castboolits.gunloads.com/showthread.php?243222-Loading-Question-MH-577-450/page2
(not me, just linking to some data I found)

[Idz]

Yes, I think I saw those plots on another forum. They used FFg which presumably burns faster (more surface area) and has higher pressure than Fg. They measured around 18000psi and martinibelgian quotes about 12000psi for Fg same loading. The Lyman BP handbook shows pressures but they vary a lot with granulation, or powder brand, or cartridge (only cup no psi data) in odd ways and they have nothing on the 577/450. Throw in fillers and there is even more confusion. I haven't seen any program like QuickLoad for BP so maybe nobody understands BP very well.

[Tackleberry41]

Issue with the 577/450 is it being so old, when did they even invent pressure testing? One could imagine if the British did do any testing it would be in some odd antiquated measurement system only they understand.

Is there some reason for this info?

[Outpost75]

Issue with the 577/450 is it being so old, when did they even invent pressure testing? One could imagine if the British did do any testing it would be in some odd antiquated measurement system only they understand.
Is there some reason for this info?

The British measured pressure by a different method which used an oiled case and measured the breech backthrust in tons compressing a lead or copper crusher, rather than the American radial copper Rodman system, which came into use in the 1880s. In US practice use of lead crushers was only for shotgun rounds and some rimfire types, whereas two sizes of copper crusher were used a .146x.400 for pistol and .225x.400 for military rifle and .225x.500 for sporting rifle, until piezoelectric transducer methods were adopted in the late 1980s.

The only sized copper being produced anymore is the government .225x.400" size "C," which is still used for measuring striker indent.

[Tackleberry41]

The British measured pressure by a different method which used an oiled case and measured the breech backthrust in tons compressing a lead or copper crusher, rather than the American radial copper Rodman system, which came into use in the 1880s. In US practice use of lead crushers was only for shotgun rounds and some rimfire types, whereas two sizes of copper crusher were used a .146x.400 for pistol and .225x.400 for military rifle and .225x.500 for sporting rifle, until piezoelectric transducer methods were adopted in the late 1980s.

The only sized copper being produced anymore is the government .225x.400" size "C," which is still used for measuring striker indent.

Well there you go, the British did probably do such testing, but wouldn't make sense. Its horribly obsolete, and nobody has used it but the British, they havent used it since WW1. So nobody would have taken the effort to conduct such tests. It wasnt that long ago that ammo pretty much didnt exist for the martinis, and what did exist was ancient. Seem to remember some Kynoch or how ever its spelled from the early 50s, but usually was sold as 'may not work'.

I looked the Martinis long ago, no ammo, brass really didnt exist, or dies to load it with, not much use. Then I saw you could get brass (tho $5 ea), and dies (that would be reasonably priced ones). RCBS still gets $468 for a set of dies, they need to be match grade for these weapons dont you know and made of gold or your wasting your time. Fortunately Lee didnt use gold so their only $84.

I bought 2 off sportsmans guide 'may be missing parts' figured 2 would get me 1. One was missing the rotting sling. I have never seen any sort of load information in a book. But their BP so not any different than anything else using the holy black. Tho has expanded my knowledge quite a bit messing with them. If you can make brass for these from 24ga shells, you probably wont find anything else much of a challenge. The tricks come in not in following established military loads, but trying reduce the amount of powder these things can consume, that and being less abusive on the shoulder. Being bottle necked alot of tricks used in straight walled wont work. Now when I mess with 45-70, well thats childs play. I did buy 2 of the McAce chamber converters so can use 45-70 in them.

[Idz]

As I understand the crusher tests they are an integrated measurement dependent upon the shape of the pressure curve. They only worked because most smokeless powder pressure curves for usable loads are very similar. I can calculate the thick walled pressure vessel stresses (Lame stress) if the pressure is known and then see how the calculations compare with material strength. If calculated stresses are far lower than strength then the gun is probably safe with that load. Wrinkles come from poor fabrication with bad lap welds or material inclusions. However corrosion tends to follow the bad weld seams so if no signs of corrosion lines are seen the welding was probably good. Likewise with inclusions. Most likely the inclusions would be spread throughout the metal so if you don't see surface inclusions there probably aren't significant hidden ones.

Life is a calculated risk. It easier if you have data to do the calculation.

[EDG]

There is no way to predict a defect in an old gun. That is why they proofed them.
On the net there is a long winded discussion that predicts very few unreported accidents with low numbered Springfields. Yet I have seen a photo of a cigar box full of low number 1903 receivers that broke apart with just a one hand whack with a hand tool.

Do the calculations for a modern barrel and see what the safety factor is.

There are engineering tests that are designed to confirm engineering calculations.
The problem is that

In theory
Theory and practice are the same

In practice
They are NOT

Here is a little about black powder pressures.
It is very general but Pedersoli says 25,000 PSI is about the limit for BP in the cartridges they chamber.

http://www.bpcr.net/site_docs-results_schedules/documents/pedersoli_proof_rules_and_allowable_limits_09-04.htm



It easier if you have data to do the calculation.