My apologies for intruding into this hallowed place. It is possible that in my eagerness to get to know fellow enthusiasts, that I have dropped myself into the wrong area. If this is so, then please forgive me.

When we consider the Crossbow as a weapon, we often talk about the ammunition used, which obviously varied immensely depending on the bowman's objectives, from killing adversaries or obtaining food supplies, as Bolts or Arrows. I have had many discussions about the merits of various Crossbows from different era's, but no one has ever gone (in depth) into the why's and wherefores of Crossbow ammunition. What I am trying to find out, is what determines the weight and length of any particular Crossbow's arrows or bolts (Sorry, but in my mind, I differentiate between the two designations,arrows being longer than bolts and bolts being shorter and heavier)and what determined their length and weight for any given situation.

Does any member have details of any discussions that have taken place on this subject? In particular, does anyone know the shortest useable length of any bolt capable of being used in say, a Crossbow of 150lb draw? Have any field tests been undertaken with this objective in view? I would be very pleased to have answers to any of my questions. Thank you for your time. Regards Walter.

Hi Walter,

A bolt must be suited to the bow to shoot well and each bow will be different to a degree.

The bolt should have a balance point between 1/4 and 1/3 back from the head to fly cleanly and this is basically true for all bolts. The bolt weight is quite important to how it flies in relation to the draw weight of the bow, so that a light bolt suited to a 150lb will not fly well from a 300lb and vice versa. I have some bolts that shoot very well from a 300lb, but when shot from a 180lb will buck and fish tail so badly that I struggle to hit a 4' boss at 20 yds.

Bolts also have a 'resonance' so that for example a 13" bolts on a 11/32 shaft with a 150 grain head will fly well from a 180lb, a 12" will fly well enough but is getting a little twitchy, but go under 12" and they fly like a dog. Get all the way down to 8" and they fly well again.

Fletch size also has an impact on how they fly and sometimes not the way you expect, so that a bolt that is twitchy can be made to fly straight by either increasing or reducing the fletch size.

Experimentation is in order and the answer to your question is in reality many weeks of chart making that I don't think anyone has done.

My light bows generally run a 4.5-5" powerstroke and a 150lb will shoot 11/32, 13", 150 grain, 4" fletch well, a 150lb with a longer stroke will need a heavier shaft and preferably heavier head.

Heavier bows tend to be more forgiving and so an 800lb bow will tolerate bolts made for 300lb upwards. A bolt to suit an 800lb will be around 15" long 5/8 barrelled ash with a 45-75gram head.

With an 850lb bow, I have found that taking a bolt weight from 85grams to 120grams makes almost no difference to the exit velocity from the bow, so the natural act would be to select from the heavier end of this.

Regards

Tod

Hello Tod. There you are you see. I knew that I would very soon be well and truly out of my depth, I think more to my lack of real study of this fascinating subject that anything else. Okay so I am going to have to return to the books and get more into the relationship of crossbow bolts with their respective bows that I have done to date.

One thing though which I am grateful for Tod, is that you have at least confirmed, (I think) my belief that bolts were used, in lengths of at least 8 inches. I had previously seen photographs of medieval bolts which were only 8 inches long and completely fletchless, being made of iron and obviously weighing many grams, perhaps even ounces. That these 8 inch bolts were used in crossbows of varying draw weights encourages me to continue my search for more information.

Tod, you have given me lots of valuable information which I shall use in the days and months ahead. I want to thank you for this and hopefully will get back to you as soon as I am more fully equip to do so. My heartfelt thanks to you and yours. Walter

Walter Spencer wrote

Quote:

One thing though which I am grateful for Tod, is that you have at least confirmed, (I think) my belief that bolts were used, in lengths of at least 8 inches. I had previously seen photographs of medieval bolts which were only 8 inches long and completely fletchless, being made of iron and obviously weighing many grams, perhaps even ounces. That these 8 inch bolts were used in crossbows of varying draw weights encourages me to continue my search for more information.

Hi walter,

No problem with the help. Although an 8" bolt will fly well from a 150lb bow, I have never seen a historic example and nor have I seen a historic all steel bolt and would love to see either if you have sources. Historically bolts are (generally) found between 13-15" long.

Tod

I think I must equate to the medieval buffoon because I now find that the references I thought I had to actual factual, historical iron bolts, were in fact, references to iron and aluminium bolts being made, in replica fashion. But I am encouraged that discussion is underway, because I have this feeling that in some ways we are overlooking the fact that some of these, so beautifully crafted arrows of various lengths, even up to 30 inches, are not always as effective as a short, heavy bolt of 8 to 12 inches would be.

The answer is, I believe, in the momentum of the arrow, or as I see it, the bolt. Momentum being the mass of the bolt multiplied by its velocity, as every member knows and I think that if we could run a series of experiments, then we would see that the shorter, heavier bolt, even though it was subject to a faster drop rate, would impart a greater blow to the target. Kinetic energy (foot pounds) being considerably higher than could be achieved with a longer, slimmer arrow of light weight.

But I am still light years away, or so it seems, from finding out if the shorter, heavier bolt of 8 to 9 inches would perform well in any crossbow of 150lbs to 300 lbs draw. Hopefully some members might decide to tackle this issue with a series of well documented trials and give the membership their results. But still pleased the way this topic is going. Regards to all. Walter

Gary Teuscher wrote

Quote:

I would hazard to guess again as well then that the draw lengths for the bows might be in the 10-12" range? And I am speaking of drawlength, not powerstroke.

If you measure the originals or pictures of, you come to two broad ranges for western and central European bows.

Hunting bows have a bow length or around 600mm and a curve of around 100mm depth and a powerstroke of around 120mm

War bows have a length of 720mm a curve of around 130mm depth and a powerstroke of around 170mm.

Obviously there are many exceptions outside of this.

Tod