25g--Summary

m_head, lb	N	PE, ft-lb	v_bodyafter, ft s^-1	v_frags, ft s^-1	v_snap, ft s^-1	*t_lurch, ms*	R_head, in	R_bullet, in
5	3	510–570	-0.9 to -1.0	460–550	4.4–4.7	11–24	5.2–5.5	4.8–5.0
6	18	210–590	-0.9 to -1.2	430–840	4.1–4.8	3–24	4.2–5.5	4.8–6.0
7	30	120–600	-0.9 to -1.3	420–910	4.0–4.8	2–24	3.8–5.5	4.8–6.8
8	30	110–600	-0.9 to -1.3	420–920	4.0-4.9	1–23	3.5–5.2	4.8–6.8
9	20	140–600	-0.9 to -1.2	420–900	4.0-4.8	1–19	3.5–4.8	5.0–6.8
10	13	110–590	-0.9 to -1.3	440–920	4.0-4.8	1–15	3.5–4.2	5.5–6.8

    This summary of allowed values reveals the remarkable facts that (a) the lurch is always negative, regardless of the combination of variables and the mass of the head, and (b) the speed of the lurch is constrained to the same narrow range of 0.9–1.3 ft s^-1 regardless of the mass of the head. Moreover, the other variables are similarly constrained to near-constant ranges. This means that there is a basic range of solutions for the basic set of variables. The more reproducible the range of solutions, the more fundamental it is.
    To put it another way, the SL7A scenario with default values for the important variables Θ_cl, m_cloud, d_snap, and m_body allows only a narrow range of answers for the equally important variables PE, v_bodyafter, v_frags, and v_snap. The ranges for PE, v_bodyafter, and v_frags overlap the observed or default values or are very close to them.
    To put it still another way, scenario SL7A requires solutions that are consistent with the observations. In particular, it requires a rearward lurch at speeds close the the observed 0.8 ft s^-1. This is a very strong result, even stronger than I had expected to find when I began this work.
    Nevertheless, these results come from only a single scenario. We next try the same approach on SL6A, which solves for v_cloud instead of PE, and has a very different default answer for the lurch. The next section shows that in spite of these differences, the allowed ranges prove to be very similar.