Monday, August 3, 2015

3 August 2015Presentation On Shaped Projectile Testing for ASTM Consideration.
Link to PDF at the bottom of this announcement. Please read this message in it’s entirety before downloading.
As we promised in June, we are releasing the presentation we developed for input to the ASTM subcommittee that is considering the question of modifying the definition of a paintball in ASTM Standard F1979-10 to include the addition of non-spherical shaped projectiles.
Our findings and recommendations contained in this document are only intended for the actionable use of ASTM members.
This presentation is offered freely to the paintball community only for information purposes, to satisfy the curiosity of the community and to aid any other researchers who may be interested in repeating, validating or extending this work.
If you reference / forward or cross-post this document please attribute the original authors and source link for the document.
You assume full responsibility for your actions if you decide to use this information to make any decisions regarding the use of any paintball or paint projectiles in any way. We are not accountable for your actions.
This testing was designed to answer a fundamental question:  When comparing paint types of similar mass and velocity, does a First Strike paint projectile impact the target with a similar or different force when compared to spherical paint?

We believe that this is the foundational question on which the remaining ASTM standard paintball testing can be subsequently layered on top of. Why?
    1. There has been many many claims in social media and elsewhere that FSR hit with more force than round paint-balls. Until now, with the release of this test data, there has been no publicly released empirical data to prove or disprove this claim. In order to move the decision making process froward this question must be put to bed once-and-for-all.
    2. The force imparted by the impact of the projectile drives the outcome of all other currently defined impact type ASTM test. Since the caliber, maximum allowable mass, and leading edge shape (hemispherical) of the FSR and common round-balls are the same we propose that establishing a clear comparison and understanding of impact force is the key first step. If the recorded forces are found to be notably different then we would have to re-evaluate any next steps. If the impact forces are found to be the same then we propose it is a natural next step to include non-spherical projectiles in the definition thus opening up the ability for manufacturers to legitimately conduct the remaining suite of ASTM tests. (those tests are not applicable today because of the definition only including spherical paint)

Some things to keep in mind.
1. Paintball is an extreme sport. There are many risks to your health that you assume as a player when you pickup a loaded marker and step out onto the field. The accountability for the decision to play is solely yours and yours alone. Wear the right approved safety gear, educate yourself on proper gun operations and be safe.
2. We specifically do not address the question of pain. Pain is a very subjective thing that can and does vary for each and every person and from situation to situation. Only you can decide what is an acceptable maximum level of pain. There is no off-the-shelf pain meter that anyone can go buy to conduct an empirical test.  Please do not ask us about pain. It is like asking about porn, it cannot be described or measured but you know it when you experience it.
3. We do not address safety. That question is possibly answered by the test and evaluation of products by vendors against a number of other standard tests that have been developed over time. Please do not ask us if anything is safe or not.
4. This test protocol is only one way of testing for impact force.
    •    We used commercially available and laboratory calibrated (traceable to NIST standard) piezoelectric impact force load cells interfaced to a data acquisition module with a sample rate of 51.2 kilohertz (51.2 thousand samples per second). This provides sub 10,000th of a second measurements so we can measure / record the impact forces over time and with fine resolution.
    •    The use of .5 inch thick ballistic gel was determined to be an approximate substitute for human flesh. In reality there is no perfect substitute. Human flesh/muscle is vascular. It has arteries, veins, capillaries etc. that possess and impart internal pressure to the flesh that is not able to be reproduced in an off-the-shelf product.  We used .5 inch thick gel based on our observation of common areas of the human body that receive paintball impacts, best, arms, back, thigh and so forth.
    •    Given that the FBI and other forensic scientists use this formulation for projectile penetration studies and is accepted to be an approximation of the resistance offered by flesh to a bullet, we felt it was a suitable product to aid in simulating non-penetrating blunt force impacts as well. It receives a hit, flexes with the hit and rebounds to its pre-impact state. It may deform, tear, crater and split a well. So, like flesh it can be transformed. We reiterate, it is an approximate substitute.
   •   Why not ballistic clay? We are not trying to capture the shape of permanent wound cavities. We needed a substance that approximates the behavior of human skin over muscle (deform and rebound) and would permit for the transferal of impact forces to the sensors in a reliable, consistent and repeatable manner. For every shot into gel we used a new fresh gel sample.
    •    The distance we set the target from the muzzle (55 inches) was selected in order to minimize to the greatest degree possible, any change in velocity from what was read at the chronograph as a result of distance. We were testing for worst case, maximum velocity, maximum impact force readings.
    •    There is a difference between the theoretical force calculation and actual force measured. A round paintball and a shaped First Strike projectile will deform on impact. The way they deform has an effect on the actual force being transferred into a target. It is a well known observation that round paint-balls that are not brittle and bounce can hurt a lot more than good quality paint-balls that break much easier.

        ⁃    Actual impact force measurements differ from the theoretical because each round gelatin projectile, even those from the same box, will deform (squish, expand, fracture, break, rupture) in different ways due to the nature of gelatin and it’s sensitivity to shell thickness, humidity, temperature, amount of fill, fill formulation and its effect on the gelatin and so forth.

        ⁃    Straightforward impact force math cannot account for all of those dynamic variables so direct measurement is the best path forward.
        ⁃    It is logical to conclude that First Strike rounds will also have some variability in their ability to fracture but since the FSR shell is manufactured polystyrene and it is not susceptible to changes due to humidity, fill liquid, normal heat variations and so forth we believe that FSR fragmentation variability is much less dynamic and pronounced than with gelatin shell paint-balls.
        ⁃    We have not conducted formal frangibility tests yet. Please do not ask if we have. It is possible we will do so in the near future.  Your opinion on our approach may differ on some, more or all of these items. If so, we'd like to hear your rational, thoughtful feedback and we encourage you to setup and conduct your own testing and publish your own findings.

5. We are extremely happy to collaborate on any legitimate peer review of this work or extension to this work. We do not profess to have all the answers. We are sharing what we did and what we think we learned. This is a learning endeavor for all of us and we want to continue helping to be part of a process to improve our collective body of knowledge and the sport and industry of paintball.
Please send any relevant questions you may have to: . We will answer them as we can make time.
Please send all flames and other hateful vibes >/dev/null
ASTM Presentation document can be found at this link:
MAG FED MONTHLY has done an article on this work as well:
Thank you all for your support and patience,

Lou Arthur

David Cady

David Williams

No comments:

Post a Comment