I've been playing around with ptbsearch and have found a few things of interest. First, a periodic R135 Herschel conduit (shown here at periods 4, 5, 6, and 8):

`x = 140, y = 51, rule = B3/S23`

17b2o$17bobo$19bo75b2o2b2o$8b2o5b5ob2o72bobo2bo$2b2o5bo4bo6bobo18b2o

38b2o8b2obob2obobob2ob2o13b2o$2bobob3o5b2o2b2obobo18bobob2obo32bobob2o

bo2bo2bo3b2ob2obob2o13bobob2o$4bobo5b3o3bobobo21bobob2o34bobob2o4bob2o

3bo22bobo2bo$4b2o5b3o6bo23b2o9b2o27b2o7b2obob2o2b2ob4o15b2o2b2o$14bo4b

2o31b2o2bo35bo2bo2bo2bobo4bo23b2o$14bo3b3o30b2ob2o36bo2bo2bo3bo2b3o$

10bo3bo3b3o30b2o39bo9bob2o24bo3bo$10bo3bo3b3o30b2o39bo3bob3o29bo4bo$

14bo3b3o30b2ob2o36bo3bo5bob2o26bobobo$14bo4b2o31b2o2bo35bo3bob2ob2ob2o

27bobobo$11b3o6bo34b2o36b2obo2bobo32bo4bo$12b3o3bobobo71bobobo2bo33bo

3bo$2bo11b2o2b2obobo18bo39bo11bobo2b2o21bo$2bobo9bo6bobo18bobo37bobo

10b2o25bobo11b2o$2b3o5b2o3b5ob2o19b3o5b2o30b3o5b2o30b3o5b2o$4bo5b2o7bo

24bo5b2o32bo5b2o32bo5b2o$17bobo$17b2o7$9b2obo36b2obo36b2obo36b2obo$9bo

b2o36bob2o36bob2o36bob2o2$2b2o38b2o38b2o38b2o$2b2o38b2o38b2o38b2o16$b

3o37b3o37b3o37b3o$bo39bo39bo39bo$2o38b2o38b2o38b2o!

It is of particular interest because it uses a well known still life that is part of many low period oscillators but was not used to catalyze larger reactions until a search by MikeP found it. I have had some success in using this still life with ptbsearch. The only use for the new conduit that I could see at the moment is a slight improvement of the p316 gun (using modified p4 sparkers to reduce size further):

`x = 94, y = 81, rule = B3/S23`

b2ob2obo$obobob4o5b2o$o2bo6bo4bo5b2o$bobob2o2b2o5b3obobo$2bobobo11bobo

$4bo7b2o5b2o20b2o$3b2o4b2obo28bo$2b3o3bo3bo29bo11bo$2b3o7bo28b2o9b3o$

2b3o7bo38bo$2b3o3bo3bo38b2o10b2o$3b2o4b2obo50bo$4bo7b2o7b2o38bobo$2bob

obo13b2obo37b2o13b2o$bobob2o2b2o6b2o2bobo14b2o36b2o$o2bo6bo6b2o3bo15b

2o$obobob4o3b2o$b2ob2obo5b2o67b2o$82b2o$78b2o$78b2o3$47b2o$48bo34b2o$

45b3o35b2o$12bob2o29bo$12b2obo2$21b2o$21b2o7$31b2o$31bo$29bobo$29b2o

32b2o$14bo47bobo$14b3o45bo$17bo43b2o$16b2o6$71b2o$71b2o20bo$91bobo$78b

ob2o10b2o$48bo29b2obo$9b2o35b3o$9b2o34bo$45b2o3$14b2o$14b2o$10b2o$10b

2o67b2o5bob2ob2o$79b2o3b4obobobo$54b2o15bo3b2o6bo6bo2bo$16b2o36b2o14bo

bo2b2o6b2o2b2obobo$16b2o13b2o37bob2o13bobobo$30bobo38b2o7b2o7bo$30bo

50bob2o4b2o$29b2o10b2o38bo3bo3b3o$42bo38bo7b3o$39b3o9b2o28bo7b3o$39bo

11bo29bo3bo3b3o$52bo28bob2o4b2o$51b2o20b2o5b2o7bo$73bobo11bobobo$71bob

ob3o5b2o2b2obobo$71b2o5bo4bo6bo2bo$77b2o5b4obobobo$86bob2ob2o!

I have also recently been looking at stable circuitry that converts one common pattern to another. As far as I could tell, there were no known century-to-Herschel converters, so here are two (I would not be surprised if these are already known):

`x = 72, y = 28, rule = B3/S23`

63b2o$63b2o2$54b2obo$54bob2o$2o$bo28b2o38b2o$bobo26b2o38b2o$2b2o42b2o$

47bo$47bobo$48b2o4$20bo39bo$19b3o37b3o$21b2o38b2o3$11b2o$10bobo$10bo$

9b2o$50b2o$51bo$48b3o$48bo!

The only patterns I can think of where the century features prominently are the p246 gun, bistable switch, and Diuresis. The only one of these patterns in which a century-to-Herschel converter would be applicable would be the bistable switch, but the above converters do not work with it.

With a little bit of searching I came up with this (very slow) pi-to-century converter (this also uses MikeP's still life catalyst):

`x = 33, y = 38, rule = B3/S23`

32bo$30b3o$15bo13bo$15b3o11b2o$18bo$17b2o14$6b2o$2b2obobo$o2bobo$2o2b

2o3$5b2o$5b2o6$13b3o$13bobo$5b2o6bobo$4bobo$4bo$3b2o!

This works with one of the century-to-Herschel converters above, and, when combined with the known Herschel-to-pi converter, gives a new conduit, Lx496:

`x = 60, y = 61, rule = B3/S23`

42b2o$43bo$43b3o8$18b2o$19bo28b2o$19bobo26b2o$20b2o9$22b2o$21bobo$21bo

$20b2o7b2o$28bobo$28bo29b2o$27b2o29bo$56bobo$56b2o4$14b2o$14b2o5$2o$bo

52b2o$bobo50bobo$2b2o52bo$56b2o6$2bo$2bobo$2b3o34b2o$4bo19b2o7b2o5bo$

25bo7b2o2b3o$14b2o6b3o12bo$14b2o2b2o2bo15b2o$18bobobo16bo$20bob2o13bo$

20bo2bo13b2o$21b2o!

It's so slow and bulky that it probably will not improve any guns, unfortunately.

Also, one of Guam's new conduits can reduce the size of the p421 (and related p842) gun:

`x = 101, y = 76, rule = B3/S23`

23bo7bob2o28b2o$21b3o7b2obo27bo2bo$5bo14bo41bob2o$5b3o12b2o38bobobo23b

2o$8bo47b2o2b2o2bo23bo$7b2o47b2o6b3o22b3o$67bo23bo$66b2o$8b2o$8b2o17b

2o70b2o$27b2o69bobo$99bo2$55bobo$55bo4b2o28bo$59bo29bobo$24b2o30b2obob

2o26bobo5b2o$24bo19b2o11b4o29bo6b2o$26bo16bobo10b3o$25b2o16bo11b2obo$

21b2o19b2o11bo2b2o$21bo33b2ob2o$22b3o25b2o4bobo$24bo26bo5bo38bo$48b3o

44bobo$48bo7b2o38bo$56b2o$5b2o55b2o$4bobo56bo$4bo55b3o$3b2o55bo32b2o$

93bobo$95bo$95b2o$77bob2o$77b2obo2$13b2o71b2o$13b2o71b2o2$20bob2o$20b

2obo$4b2o$5bo$5bobo$6b2o32bo55b2o$38b3o55bo$37bo56bobo$37b2o55b2o$43b

2o$4bo38b2o7bo$3bobo44b3o$4bo38bo5bo26bo$42bobo4b2o25b3o$41b2ob2o33bo$

41b2o2bo11b2o19b2o$42bob2o11bo16b2o$42b3o10bobo16bo$2b2o6bo29b4o11b2o

19bo$2b2o5bobo26b2obob2o30b2o$9bobo29bo$10bo28b2o4bo$43bobo2$bo$obo69b

2o$2o70b2o17b2o$91b2o$33b2o$9bo23bo$9b3o22b3o6b2o47b2o$12bo23bo2b2o2b

2o47bo$11b2o23bobobo38b2o12b3o$35b2obo25bo15bo14bo$35bo2bo26bo11b3o$

36b2o25b3o11bo!

There are likely other gun improvements from these new conduits, but I have not tried much.

Request: Does anyone have a thorough collection of the known stable converters. I am especially interested in circuits that convert common objects to other common objects, as well as converters of common objects to gliders (or gliders to common objects). Below is a collection of all of the somewhat interesting converters that I can find (excluding Herschel-to-X, glider-to-X, and X-to-glider converters). Is it missing anything?

`x = 422, y = 364, rule = B3/S23`

9b2o$9b2o8$2b2o$bobo$bo$2o4b2o$7bo$3bobo$b3ob2o$o$b3ob2o$3bob2o2$bo$b

3o$4bo$3bobo$4bo7bo$11b3o$2bo7b2obo$bobobo154b2o$bo2b2o154b2o$2o$151b

2obo7bo$151bob2o6b3o$160b2obo3$43b2o$43b2o9$31b2o$31b2o2b2o$35bobo$37b

o$37b2o8$93bo$92bobo$92bobo$93bo12$102b2o$102b2o2$84b2o$83bobo$83bo$

82b2o$113b2o$112bo2bo2b2o$112bobo4bo$93b2o18bo5bob2o$92bobo21b2obobo$

92bo23bo2bo2bo$91b2o20bo4bo2b2o$113b5o2$115b2obo$115bob2o31$284b2o38b

2o38b2o$284b2o38b2o38b2o3$283bo39bo39bo$218b2o28b2o32bobo37bobo37bobo$

5b2o211b2o28b2o33bo39bo39bo$5bo274b3o37b3o37b3o$3bobo203b2obo26b2obo

37bo39bo39bo$3b2o204bob2o26bob2o34b2obo36b2obo$7b2o128b2o138b2ob3o14b

2o18b2ob3o14b2o$7bo129bo145bo13bo25bo13bo$5bobo127bobo144b2o11bobo24b

2o11bobo$5b2o4bo123b2o158b2o4bo33b2o4bo$9b3o287b3o37b3o$8bo289bo39bo$

9bo84bo204bo39bo$10bo82bobo204bo39bo$9b2o82b2o43bo29bo130b2o38b2o$137b

obo27bobo109bo$bo69bo29bo29bo6bo22bo6bo52bo29bo26bobo10bo39bo39bo39bo$

3o67b3o27b3o27b3o27b3o57b3o27b3o25b2o10b3o37b3o37b3o37b3o$o69bo29bo29b

o29bo59bo29bo39bo39bo39bo39bo2$64b2o99b2o46b2o28b2o121bo$63bo2bo98bobo

44bobo27bobo120bobo44b2o$63bobo101bo44bo29bo121bo2bo44b2o3b2o$64bo102b

2o42b2o28b2o76b2o44b2o50b2o$225b2o91bobo$225bo92bo$226b3o28b2o58b2o99b

2o$228bo28bo154b2o4bo$258b3o151b2o5b3o$260bo160bo56$67b2o$67b2o232bo$

104b2o193b3o$104bobo177bo13bo$105bo5b2o171b3o11b2o$111b2o174bo$286b2o

5$21b2o77b2o8b2o90b2o$21b2o77bo8bo2bo89b2o$98bobo9b2o$80bo17b2o$20bo

57b3o120bo$19bobo32b2o21bo122bobo$20bo34bo21b2o122bo$17b3o35bobo140b3o

$17bo38b2o140bo$275b2o$271b2obobo$269bo2bobo$26b2o53b2o55bo6bo61b2o60b

2o2b2o$26b2o53b2o54bobo5b3o59b2o$137bobo8bo$135b3ob2o6b2o125b2o$35b2o

97bo81b2o56b2o$35b2o98b3ob2o75b2o$2o55bo79bob2o40b2o$2o54bobo122b2o$

57bo2$19b3o12b2o33b3o37b3o37b3o48b3o12b2o65b3o$19bobo12bo34bobo37bobo

22b2o13bobo6bob2o38bobo12bo66bobo$19bobo8b2o3b3o23b2o6bobo29b2o6bobo

23bo13bobo6b2obo38bobo8b2o3b3o55b2o6bobo$30bobo4bo22bobo37bobo32bobo

73bobo4bo54bobo$32bo27bo39bo35b2o75bo59bo$32b2o25b2o38b2o112b2o57b2o2$

5b2o179b2o$6bo180bo$3b3o178b3o$3bo180bo33$63b2o$63b2o2$54b2obo$54bob2o

$2o$bo28b2o38b2o$bobo26b2o38b2o$2b2o42b2o$47bo$47bobo$48b2o4$20bo39bo$

19b3o37b3o$21b2o38b2o3$11b2o$10bobo$10bo$9b2o$50b2o$51bo$48b3o$48bo38$

2o$2o3$9b2o$b2o6b2o$bobo$3bo$3bo2$8b2o$8bo$9b3o$11bo!

A side note: Guam's new Herschel receiver (posted

here) needs two parallel gliders with a path separation of 4, which fits nicely between the possible separations for Callahan's receiver (2, 5, and 6).