2 from LEFT FIELD

[John T]

Hello.

I have 2 questions that are so far left they are out of the ball park.

1. Has anyone tried a two-powder load to enhance ignition? The concept is that the case would firstly be loaded with a fast powder, followed by a slow powder. It could be, 1/3 of a normal 2209 load, topped with a 2/3 normal 2217 load. The test case is the 7 RSAUM. The powders are not mixed (except partially at their interface) and are loaded in runs. The 2209 would be an after-burner for the slow 2217.

2. Has anyone altered flash holes to make them conical? There was a myth that the small holes in small primer pockets had a venturi effect, made them "spit holes". A myth long busted. If the flash hole was reamed to be conical, with the wide aperture (0.125) in the pocket and the narrow aperture (0.080) inside the case, the funnel would create a venturi-like effect.

John T.

[AlanF]

John,

In relation to Q1, I believe this has been practiced in the match rifle ranks. They call them "duplex" loads.

[PeteFox]

Hello.

I have 2 questions that are so far left they are out of the ball park.

1. Has anyone tried a two-powder load to enhance ignition? The concept is that the case would firstly be loaded with a fast powder, followed by a slow powder. It could be, 1/3 of a normal 2209 load, topped with a 2/3 normal 2217 load. The test case is the 7 RSAUM. The powders are not mixed (except partially at their interface) and are loaded in runs. The 2209 would be an after-burner for the slow 2217.John T.

John,
This should answer all your questions

bulletin.accurateshooter.com/2011/04/duplex-powder-loading-causes-catastrophic-ar15-kaboom/

However if you want to persist I would suggest rifle mounted in a vice and a long string on the trigger
Pete

[John T]

Hello Pete.

You forgot to mention that the idiot used PISTOL and rifle powder! Only in America.

It seems that duplex loading has little application outside black powder shooting. Alan, I will take your suggestion and contact John Kielly.

John T.

[pjifl]

I know that experiments have been done to use a small tube leading from primer hole to a position well up the powder column. The objective was to achieve better or more uniform ignition. Cigarette paper has been used as the tube. Some artillery does use something like a perforated stalk leading from primer perhaps half way up the propellant column. Not to be confused with the initiation of shaped charges which usually use a stand-off tube to convey initiation to the ideal spot in the explosive.

I imagine if one used two powders not too dissimilar in burning rate it could be a bit safer than the referenced incident. But I reckon the repeatability of the zone where they meet would always make it less accurate even apart from safety issues. Imagine the interface after vibration during transport in a vehicle.

I don't think it is a very good idea in a small arms cartridge - especially with a partially mobile grainy propellant.

Peter Smith.

[Gyro]

Hello.

I have 2 questions that are so far left they are out of the ball park.

1. Has anyone tried a two-powder load to enhance ignition? The concept is that the case would firstly be loaded with a fast powder, followed by a slow powder. It could be, 1/3 of a normal 2209 load, topped with a 2/3 normal 2217 load. The test case is the 7 RSAUM. The powders are not mixed (except partially at their interface) and are loaded in runs. The 2209 would be an after-burner for the slow 2217.John T.

John,
This should answer all your questions

bulletin.accurateshooter.com/2011/04/duplex-powder-loading-causes-catastrophic-ar15-kaboom/

However if you want to persist I would suggest rifle mounted in a vice and a long string on the trigger
Pete

I'm with u Pete ... don't go there !

If ya really bored maybe de-cap live primers without eye protection on ? That might be safer.

[Tim L]

2. Has anyone altered flash holes to make them conical? There was a myth that the small holes in small primer pockets had a venturi effect, made them "spit holes". A myth long busted. If the flash hole was reamed to be conical, with the wide aperture (0.125) in the pocket and the narrow aperture (0.080) inside the case, the funnel would create a venturi-like effect.

John T.

I hope to catch evidence of modifications to flash holes with the high speed cam.
I have already compared a standard (parallel) small hole to one chamfered in the powder side (supposed to mimic a rocket nozzel).
I will try chamfering the pocket side and see what I see.
I'll also be turning a small hole into a big one and see what effect that has.

[bsouthernau]

Alan, I will take your suggestion and contact John Kielly.

John T.

Alan is correct John. Wilf Wright was experimenting with duplex loads at some stage. He didn't persist and it didn't catch on.

Barry

[lonerider43]

2. Has anyone altered flash holes to make them conical? There was a myth that the small holes in small primer pockets had a venturi effect, made them "spit holes". A myth long busted. If the flash hole was reamed to be conical, with the wide aperture (0.125) in the pocket and the narrow aperture (0.080) inside the case, the funnel would create a venturi-like effect.

John T.

I hope to catch evidence of modifications to flash holes with the high speed cam.
I have already compared a standard (parallel) small hole to one chamfered in the powder side (supposed to mimic a rocket nozzel).
I will try chamfering the pocket side and see what I see.
I'll also be turning a small hole into a big one and see what effect that has.

i chamfer the primer side flash hole and the inner case flash hole [both slightly],i figure it must help with ignition,but i cant prove anything.

[GSells]

2. Has anyone altered flash holes to make them conical? There was a myth that the small holes in small primer pockets had a venturi effect, made them "spit holes". A myth long busted. If the flash hole was reamed to be conical, with the wide aperture (0.125) in the pocket and the narrow aperture (0.080) inside the case, the funnel would create a venturi-like effect.

John T.

I hope to catch evidence of modifications to flash holes with the high speed cam.
I have already compared a standard (parallel) small hole to one chamfered in the powder side (supposed to mimic a rocket nozzel).
I will try chamfering the pocket side and see what I see.
I'll also be turning a small hole into a big one and see what effect that has.

i chamfer the primer side flash hole and the inner case flash hole [both slightly],i figure it must help with ignition,but i cant prove anything.

Can only help !

[bruce moulds]

2. Has anyone altered flash holes to make them conical? There was a myth that the small holes in small primer pockets had a venturi effect, made them "spit holes". A myth long busted. If the flash hole was reamed to be conical, with the wide aperture (0.125) in the pocket and the narrow aperture (0.080) inside the case, the funnel would create a venturi-like effect.

John T.

I hope to catch evidence of modifications to flash holes with the high speed cam.
I have already compared a standard (parallel) small hole to one chamfered in the powder side (supposed to mimic a rocket nozzel).
I will try chamfering the pocket side and see what I see.
I'll also be turning a small hole into a big one and see what effect that has.

tim,
for a short time black powder cartridge shooters were enlarging flash holes hoping for improved accuracy.
they are now putting small wads under the primer, and or a paper wad under the charge in the bottom of the case.
one of my rifles shoots better with pistol primers over a paper wad, and the other shoots better with rifle primers and no wad.
just goes to show you have to suck it and see.
what does this have to do with smokeless?
probably nothing, as the ignition and burning characteristics of the 2 propellents are different.
however the peak pressures of black are much lower than smokeless, so experimenting in a strong action is less risky.
there was some talk that flash hole length had more effect than diameter or vice versa (can't remember)
by coning the inside the case part of the flash hole you are in effect shortening its length.
probably the main aim of this stuff is to achieve the lowest s.d. possible.
more speed can be easily achieved by a bigger case (except in match rifle.)
bruce.

[Rich4]

I think any adjustments to flasholes should be considered with regards to fluid dynamics, seems rather similar to me, Rocky Gibbs was experimenting with flash tubes and duplex loads for long range in the 50’s, mostly to maximise 30-06 cases though, I’m intrigued by the flash tubes but mostly considered to be too much trouble

[bruce moulds]

trouble with a serious flash tube is that it uses powder space.
elmer keith claimed great velocity advantages from them when developing such rounds as the 333 okh.
bruce.

[Tim L]

I've seen some very interesting outcomes with regards to point of ignition in a column of combustable material. The general outcome is that ignition at the end of the column does not provide the best burn characteristics. Igniting the centre of the column is far more desirable in terms of efficiency and even burn. Not sure it's worth the effort in our case though.