The Ballista

Back in the day  (20 odd years ago) I gained a bit of experience shooting different types of bolts out of this old fellow. It was my first machine and I called it the “Gallwey” .

The bolt seen here  does not project through the opening in the box frame.   Shorter bolts like this can tend to make the shooter a tad squeamish when it comes time to pull the firing lanyard.  A machine with unbalanced thrust in the spring bundles could easily cause a short bolt to  jump it’s groove.  If it hit one of the stanchions in the box frame, parts of a shattered bolt  might bounce back in surprising and unpleasant ways. It’s all great fun ….. until somebody puts out an eye……

And so, we might coclude that conventional outswingers, of the type seen above, are not  ideal for use with shorter bolts.  Now why would the Romans be interested in shooting shorter bolts like this? Or, for that matter, really short bolts, perhaps half the length of the one seen here? (Ref: Dura Europos bolt dimensions, archives, Dec 2008)   If you are trying to develop a precision sniping weapon,  short bolts have many advantages.  With a properly designed short bolt (i.e. not a long javelin type, something maybe 18 to 36 inches long) you get the following: higher velocity, flatter trajectory, better aerodynamics, greater range, better penetration due to the reduced cross section, and because it is so stiff relative to it’s length, the issues of spine that can beset longer projectiles, are virtually eliminated.*  On this latter,  I have many times witnessed the kind of oscillation than can occur in a long and under-spined  ballista bolt/javelin. Unless they are of large enough diameter (and therefore, unduly heavy) longer style shafts tend to buckle under all that power and get a case of the wobblies.  Very underwhelming indeed.

So, all in all, my experience suggests that a relatively short bolt, of appropriate mass, is a better projectile for making picked shots.   As a work of experimental archaeology, Firefly is purpose built to explore Roman sniping capabilities.  In that role,  flat trajectory* may not be everything, but it’s pretty close in my book.

Which brings us to the virtues of inswingers.  I have done extensive shooting with both outswingers and inswingers for a couple of decades now, at power levels guaranteed to put a sizable dent in my noggin if something goes wrong.  I can only say it feels a lot safer using an inswinger when one is shooting short bolts.  There are no stanchions for a misfired bolt to crash into. Knowing any unpleasantness will be cast harmlessly out the front of an inswinger, does wonders for reducing that pesky old flinch factor that can disturb accurate shooting.

*  And let’s not forget, with short bolts the storage and transport of ammunition is more efficient.   Short bolts would probably be less expensive to produce given the smaller amount of material they use in the shaft and head. Also, there is less chance of the shafts warping.  Short bolts would be harder to see in flight and, therefore, less easy to dodge.  Short bolts rule says the quartermaster.

*  “Flat trajectory” is a relative term.  We are not talking about rifle ballistics here.  After all, Firefly is really just an overgrown crossbow, not a 30’06.

I have been asked, not for the first time, how much would I be willing to sell Firefly for?  I provide my usual response.

The purpose of today’s test was to see if we had anymore waggle tails.  Pleased to report they are gone.  Suspected cause of the two we had last trip is that the machine’s spring bundles had to settle down again after being mothballed for two years (it was the first two shots of that previous outing that were errant)

There are 4 shots visible here and they all fell into a 35 foot circle.  The center of the group is at 760 yards.  A fifth shot could be called a flyer because it ended up 40 feet to the right of the group shown.  As usual, the bolts are my 520 gram “heavies”.  Velocities in fps, as follows:  322,  error, 316, 315, 302.   I had applied a brand new serving on the string and I think that is why we were getting higher speeds at the start of this string of shots.  Once it had abraded a bit the speed came down closer to 300 fps, which is normal for the settings I am using.  These fluctuations are very minor in the overall scheme of things and clearly did not mar the group size by much.

More remarkable is that this group was shot in a relatively high head-wind (15 mph, gusting to 20).  Before today I would never have thought it possible to do this well when the wind is up that high.   That it was a head-wind rather than a side-wind must be relevant; no way it could do that with a side-wind.  I am very glad Bob and Jane Thompson were there to witness it. Otherwise it would  sound like some tall tale, and that just ain’t my thing.  Here is a video of all the high drama as seen through the eyes of Bob and Jane.  Time stands still when the bolt is in flight.  Click for vid:   00017

And not to be left out,  Princess Oona seems to be taken with the proceedings.  Fetch the bolt girl…..  yeah, it’s out there 1/2 a mile, good luck with that….  00021

Bob and Jane inspect some Dura Europas bolts.  The blue bolt can go 900 yards and the smaller orange one can hit 1000 yards when it has a light tail wind.

Today we shot Firefly for the first time in 2 years.  I was able to get good velocity readings on all 5 shots.  Those are as follows, consecutively, and in feet per second :  307, 304, 304, 313, 301.  The bolt weight was 521 grams.  These speeds are exactly the same as we were getting before she was put into storage; so it seems fair to conclude that, at least with nylon springs, there is no loss of performance due to the torsion springs being kept in an uncocked, yet pre-tensioned condition.    Sitting in storage for that long did not effect her performance at all.   Firefly’s feelin’ frisky again.

Here is a video of my dear old friend Tony Laurent, just over from New Zealand for a visit.   Click for vid:  20150708094923    I had just managed to break the cord that holds the front sight and Tony is checking to make sure his old mate has not lost all his marbles yet.  (“Yet” is a long time, right?)  And now the NZ contingent witnessing the main event:  20150708095008(1)(1)

The first 2 of these 5 shots were waggle tails, and although their muzzle velocities were consistent with the rest of the shots, the wobble in their flight clearly reduced their range by 20% or so.  In this informal test run the machine was elevated to 40 degrees rather than 45 and so, in addition to that pair of waggles, the overall range of all the shots is about 100 yards less than usual.  The two waggle tails naturally fell quite short at 559 yards and 628 yards.  The last three shots fell neatly into a 40 foot circle, the furthest making it out to a tepid 683 yards, again due to the reduced elevation (I keep saying that, don’t I?).  The wind was very mild, perhaps 1 or 2 mph.

I am anxious to to do more formal shooting for group size at 200 and 300 yards, however, until the waggle tails are eliminated there is not much point in that.   On our next outing we will see if the problem is with the projectiles themselves, or if the machine is misbehaving somehow.  I suspect the former.

Sure hope the CG’s don’t become aggrieved at the temerity of that prediction….

The brothers Laurent seemed to dig it all.   Some definite ooh’s! and ah’s! from that quarter when shooting commenced.