English Longbow Testing against Various Armor Circa 1400

Here is an interesting series of tests.

There seems to be a consistent bias towards minimizing the effectiveness of armor. A jack test piece of fifteen layers of linen and one of deerskin is used, while the Ordinance of Louis XI sets 25 layers of linen with one of deerskin as a bare minimum, and 30 layers of linen plus one of deerskin as the desired goal.

The weight of linen used in the test piece is not specified, but linen comes in a wide range of weights.

The tests were done with pieces of simulated armor about foot square pinned over a box of clay. These would not necessarily behave the way a complete a complete jack or mail shirt would.

Here is a test against complete sleeveless jacks rather than simulated patches.

When complete jacks were tested, a 25 layer jack reproduction defeated all attacks from a a 80 lb. bow. Bodkin points did best, but failed to entirely penetrate. 15 layers over mail, attacked by bodkins, were barely penetrated.

Bane tested over mail two layers of linen, but the ordinance of St. Maximin de Treves, published in 1473, required mail worn with a jack of ten layers, with the jack as the outer layer.

The author tested the bow against modern reproduction mail made from iron wire, which is described as "average quality". However, the author describes the reproduction by saying "The rings were inconsistent in craft and the integrity of the metal around the rivet was questionable on average." I have seen similar problems in other modern reproductions of medieval mail. I doubt that medieval customers would have accepted such poor quality control in armor expected to to offer the wearer the difference between life and death. Medieval iron mail would be less protective than steel, but probably offered better protection than the modern reproduction used in the tests described as mail of "average quality."

The plate armor test also presents problems. The author apparently chose to use the minimum thickness of Robert Hardy's tests, 1.2 mm. Unfortunately, the quality of steel was not specified. I suspect that modern mild steel was used, which would be better than much medieval armor, but worse than the best. 1.2 mm is quite thin for a breastplate; Williams measured five breastplates from 1470-1510, ranging from 1.5-2.5 mm, with 2.1 mm median. Earlier breastplates and coats of plates were often worn over a mail shirt, and later ones had some overlap with the mail gussets worn beneath plate. Arming doublets worn beneath may have have been considerably stouter than the two layers of linen in Bane's tests.

Perhaps more important,body armor was convex, not the simple flat plate, and the kind needle bodkin head that gave the best results against plate in Bane's tests was particularly vulnerable to failure of the head or shaft if it struck obliquely.

Bane also draws unsupported conclusions about the damage caused by non-penetrating deformation of armor. He uses the standards published by the National Institute of Justice for body armor, which counts more than 1.7" deformation of specified clay backing material as a failure. This is designed to measure behind armor blunt trauma caused by modern bullets, which are much faster and energetic than the heavier and slower war arrow. The lowest level of protection, IIA, is expected to stop a 124 gr 9mm bullet moving at 1225f ft/s. In contrast Hugh Soar, shooting a very heavy 144 pound bow, measured his 1324 gr war arrows with leaf shaped or long bodkin heads at speeds of 155-157 ft/s. The backface of flexible armor struck by the bullet is going to have much higher peak acceleration and very different effects on the body than that struck by an arrow.

The most interesting results of the test was the high effectiveness of the ubiquitous Type 16 head in penetrating jacks and mail, against which it achieved slightly better penetration than the long bodkin. This is consistent with Soar's results with what he decribed as a leaf shape head, shaped much like a Type 16 but without separation between the barbs and the socket. He found that it performed as well against mail as the long bodkin.

Apparently subtle details can make a big difference in results. These include the shape of the arrowheads tested and the quality of the metal used in them. On the defensive side, the weight of the linen used in defensive jacks is also worth documenting.

This is experimental archaeology. Give us enough information to reproduce your results.