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There is a special rotating star shaped crimping head that's used to crimp the blank. It starts and as it rotates it closes up until the crimp is tight. If it came straight down it'd bell out the lower part of the neck. If you think that .303 crimp is pretty slick, you should see .50 Browning. It's a mean machine that does that, believe me!
The trouble with blank is that it makes a one way trip
Here's the type of star die a poster on the other board recommended to use, http://www.ch4d.com/catalog/?p=19. That's a little too much money for me just for the few cartridges I would need so I'm going to make regular blanks with the straight necks with the disk type seal and not the crimp type seal.
I can punch out perfect size card board disks with my gas check making dies. They look just like gas checks and are the perfect neck size dia. A little red lacquer applied on the disk after it's in place and they will look just like the real thing, :clap: At least like the 30-06 ones that I shot hundreds of when I was in the army. Ray
Blanks for simulating firing, whether in military training or in "show-biz" are generally lower-powered than grenade-launching cartridges.
Part of your problem is the issue of burning rate and residual pressure. Even very fast-burning smokeless propellants like "Bullseye" require a certain amount of pressure containment to facilitate complete ignition. For example, take a primed .38 Special cartridge case and tip in 5 grains of Bullseye. If you then fire that open-ended cartridge (vertically), the primer will certainly go off, but there will be a gentle shower of unburnt flakes of "Bullseye" all around you. The tiny blast from the primer simply chucks it all out of the barrel without any significant ignition.
The presence of a bullet is usually more than enough to ensure that the powder stays put as the "brissance" of the struck primer churns up the powder and commences ignition. This can sometimes get out of hand. There are a number of examples of .38 Special revolver cylinders exploding, apparently because a small charge of very fast powder behind a wadcutter effectively ignited almost simultaneously, causing a massive pressure spike. A very small amount of powder forms a flat "film" on the bottom of the case. It seems that the primer flash effectively ignites the whole lot in one go, thus drastically "spiking" the pressure curve.
With your grenade launcher, it is designed to project a reasonable mass downrange. It is this mass "occluding" the bore that allows the propellant to ignite fully. Maybe you could inject your tennis balls with water. A good seal at the base of the "grenade" will help a lot. Remember that the classic "Mills" bomb had a threaded hole in the base plug. This was used for either a rod which extended down the barrel or, later, for a plate which acted as a seal in the cup-type "Discharger, Grenade, Rifle, No2.
Interesting side-note:
I have never heard of a No4 series rifle configured like the "EY" SMLEs. There are probably several reasons for this:
Doctrinal changes that drastically reduced rifle grenade deployment.
Slightly heavier barrel profile on the No4,
Deletion of "rodded" grenades from the inventory.
I suspect that the last reason is more important. Note also that the spindly barrel on the L1A1 was expected to hold together whilst heaving Energa grenades around the countryside.
Regarding "rolling your own" discharger blanks: The ideal seal is the "petal" type as per the real thing. The CH dies have been raised previously; I have used them and, if you have to make a lot of blanks, they are excellent. Avoid using "dacron" fibre wadding as a filler; it melts and makes a mess of the barrel: in fact, avoid any filler material or wadding.
Happy hurling!!
That's interesting Bruce in Oz and food for some thought especially in a no too technical way for an 'avoid-ammo-like-the-plague' person like me! There was a cup discharger for the No4 rifle but it didn't get far. The reason, I can only presume, was that there were still thousands (?) of No1 EY rifles and cup dischargers in the Ordnance system. Indeed, we were still FTR'ing the EY rifles for mobilisation stores into the early 70's and I commented on this fact in an article '.....wot I rote...' a couple of years ago.
On a similar note, a UK supplier recently had to supply a sizeable order to the Navy for 7.62mm line throwing cartridges, used on suitably modified L1A1 rifles. Subsequently, a further order went to a foreign navy too. These were all full length, star crimped blank. I seem to recall that as these things were going to have a long shelf life, they were sealed at the end with a dob of red nail varnish. MOST suitable for the Navy I thought at the time!
Well I made a few home made blanks. Used 17 grs of I-4227 and I-4064 just to see the difference. Used my gas check formed carboard cups and sealed with enamel paint on the inside neck and outside. I'm hoping that will create enought pressure to launch the T-Ball. Just curious, if these loads don't produce enough pressure, I wonder if I should try 10 or so grs of black power alone or maybe mix a few grs with the smokeless. What do ya think?
Also as suggested, I'll fill a few tennis balls with water to help provide more weight/resistance. Ray
The real loads illustrate a few grains of black to build quick pressure. It also lights easier and flares so it would consume the smokeless quicker. Don't use too much smokeless with it though.
Up date, I tried one of the 17 grs I-4227 home made blanks and it didn't even move the ball. Then I tried two of the 14 gr 4227 loads with the 3 grs of black powder added and it shot one of the balls about 25 yrds and the one filled with water about 20 yrds.
I think the black powder is the answer. I'm going to load up few more doubling the back powder to 6grs with the same load of the I-4227 powder and see what happens. If it still is not enough pressure to hurl the balls further, I might just try a straight load of maybe 10-15 grs of black powder and see how that would work. I can't see any problem with using a straight load of black powder in the rifle. It'll be like a muzzle loading cannon only the T-ball is much lighter then a canon ball. Ray
I note that one of the recommended powders is old SR-4759.
This is a Sporting Rifle powder, not an Improved Military Rifle powder of the 4198/4227/4064/3031 type. It is almost (but not quite) the very last of the old-time "Bulk" powders but it isn't quite a Bulk powder. It has a lot of uses. You can load smokeless-for-Black with SR-4759 by calculating your charge at 38% of the Black charge; it will give you same performance ad same pressure as the full charge of Black..... and you don't have to clean the rifle immediately afterwards.
It takes light very easily and works VERY well at much-less-than-full-case charge levels. It is still available from most reloading shops.
Another powder that no-one has suggested is Red Dot, a shotgun powder made by Alliant. It is quick, takes light easily and is double-based and so rather energetic, moreso than one might think.
For any application in which you are using unconfined powder, you NEED something that takes light easily.
Hmmm..... something new to try out!
Good luck!
.
Another up-date. I loaded up one of each of the following loads and tried them out.
1. 14grs, I-4227 & 6 grs black powder. (14/6)
2. 13grs, I-4227 & 7 grs black (13/7)
3. 12grs, I-4227 & 8grs black 12/8)
4. 10grs black
5. 15 grs black
6. 20 grs black
The first load with the 6grs of black and 14 grs 4227, (14/6), was the best and shot the ball, aimed level from the shoulder, about 45 yrds. If it was aimed up it probably would have gone 75yrds. This was about the 38% formula mentioned. :clap:
I was suprised that the 3 straight black powder loads didn't do as good.
Next loads I'll try will be a larger quanity of 4227 and black mix, like 15/7 black and 16/8 black and still maining the 38-40% mix to see if I can get a little more distance. Ray
Success, switched to 2400 powder and used 17 grs of 2400 and 9 grs black powder with the tennis ball patched with a thin paper napkin to give it a tight seal. The rifle at a 30% angle shot the ball over a 100 -125% yrds. When the rifle is aimed at a 45% angle or a bit more, the ball goes extremly high up and comes down about 90 yrs.
The carboard cup shot holes in the ball, front and back until I put a strip of furnace tape on the bottom of the ball which protected it.
The main thing is to get a real tight fit with the ball that's why I used the napkin. I found this out when we were using older used tennis balls that lost some of the fuzzies and then we used a new one which fit much tighter in the cup it shot a lot further. The napkin acts like a patch in a muzzle loader and made sure the balls fit tightly with no gas leak and it worked great.
It's possible that the powder charge could even be reduced now because the napkin patch wasn't tried with the lower powder loads Ray