Blind Loaded Ammunition


#1

Hallo All. While looking up some color code information on US Made 40mm Bofors rounds, I kept stumbling on a military term I never heard before. Could anyone explain to me what does the term “Blind Loaded Projectile” refers to?
I’m glad to see the IAA forum is up and running again. Keep up the good work. I truly enjoy it.
Semper Fidelis.


#2

4thForCon,

The obsolete term “Blind loaded Projectile” (BLP) means completely inert projectile and is the old name for Target Practice (TP).

Best regards,

Rob


#3

Rob

I’m not sure the term is obsolete but, regardless, Blind Loaded means the cavity has no bursting charge but is filled with a material to simulate the weight of a real charge and the nose has a fuze body without a detonator.

If it has a tracer it is a BL-T. If the tracer is omitted the hole is plugged and it becomes a BL-P.

HE and other projectiles may also be plugged. Hence a HE-P, HE-I-P, etc. Larger projectiles with VT fuzes never have a tracer or base fuze so they are either plugged or have a base plate welded in place.

Ray


#4

They were often, but not exclusively, used for compiling range/elevation/drop tables for artillery etc. Narramore in his book Principles and Practices of loading Ammunition describes using them for this purpose.

The projectiles were often painted bright colours to aid finding them again. He mentions the fact that the scratches on the paint clearly shows that at extreme ranges the projectiles had come to ground base first. This he uses to support his views on the “angle of repose” debate. This means that projectiles don’t flip over on their downward decent to come in nose first. Instead they fly the whole trajectory at the same angle relative to the ground that they were at when they left the gun.


#5

I have a recent European 30mm one-piece dummy round which is stamped “BLIND”, so it’s used to apply to more than just projectiles, and more than just to TP.

On the subject of projectiles landing base-first at long range, it depends on the relationship between the projectile and the barrel rifling, and on the angle of elevation of the barrel when the gun was fired. According to my texts, it is certainly not generally true that projectiles maintain their initial angle throughout - they usually tip over to land point-first unless they are “super-stabilised” by too tight a rifling twist, or fired at an almost vertical angle.


#6

Tony, The angle of repose issue should be a subject for a thread in its own right. Its not something I have any personal experience of except in one small aspect.
It was one of the reasons blamed for so many “dud” shells in WW1. That and the fact that they were often landing in soft mud.
Having observed a very large number of unexploded duds piled in the corners of fields in France and Belgium over the years I have to say there is usually little or no damage to the brass noses. Interesting question.


#7

Vince, I’ve just checked Brassey’s ‘Military Ballistics’, and what this says confirms my memory. The main objective is to achieve “normal stability”, in which the shell flies (more or less) point-first throughout its trajectory all the way to the ground. They have some nice little diagrams to illustrate this, and also the undesirable effects of not achieving normal stability: instability (when the shell tumbles in flight, with drastic consequences for range and accuracy) at one extreme and superstability (when it maintains the same angle it is fired at, so lands base-first) at the other.

Achieving normal stability is a matter of getting the rifling twist correct for the shell. The spin rate required for normal stability with a 105mm shell is quoted as around 25,600 rpm, for a 155mm it’s c.16,500 rpm.

So if a shell does land base first, it means that something’s gone wrong, 'cos it ain’t supposed to happen. If properly stabilised, shells will still land nose-first even when fired at high angles; the best example is probably a spin-stabilised mortar bomb fired from a rifled mortar, which has no fins but is still designed for a point-first landing when fired at 85 degree elevation.


#8

Tony, thanks for that infomation, as i said before, its not something of which I have any personal experience. I wish some of the big gun buffs would have pitched in and maybe we could have got something going on this. Its an interesting subject that really could have expanded into a full blown debate but it seems thats not to be,shame really but I do appreciate your input.


#9

Vince

I’ve studied exterior ballistics a little (very little), both in my Gunners Mate Navy days and more recently as a long range shooter. It makes my head hurt. I would not envy the guy who tried to start a new thread on just that one small part of ballistics.

Let me get the thread started and you can take it from there (with comments by Rick, of course).

The rotation downward (aerodynamic pitch) of a bullet’s nose as it flies along an arced trajectory, so that the longitudinal axis of the bullet stays almost exactly parallel to the velocity vector throughout the trajectory, is caused by a small aerodynamic side force resulting from the yaw angle known as the yaw of repose.

Tony - I recall, in my Navy days, seeing large projectiles (5" +) buried in the sand, with only the fuze sticking out, that had come back to earth, still spinning, in a base first attitude. They were, of course, from guns that were fired as near vertical as could be done but it tells me that there must be a point somewhere between 0 degrees and 180 degrees where it starts to happen.

Now, my head is starting to hurt again so I’m outta here.

RICK !!!

Ray


#10

Maybe, and I do mean maybe, because I have no experience in this field. The big guns circa WW1 were over rifled to prevent the danger of them being under rifled. Certainly if we look at the .303 at 1 in 10 it was over rifled but they didn’t have the benefit of computer modelling in those days. Perhaps we have touched on one of the enigmas of the time, Who knows?

Ray, I can see the logic in differential air pressures and yaw to stabilise the projectile in flight. that makes sense to me.

I can only offer up two pieces of information for what thet are worth.

One is the fact that in long range rifle shooting the bullets make a slightly oval hole in the paper indicating yaw to me. The other is in the memoirs of WW1 vets who describe the screech of a shell as it comes in. Does this indicate yaw- I dont know?

Its a fascinating subject but one I am well out of my depth with. Maybe I should shut up now.


#11

Vince

I know that I am over my head.

You may be right about the big guns being over rifled. I think the old 5" guns that I worked on would spin those big bullets at about 75,000 rpm. That’s a lot more than the numbers that Tony quoted.

Ray