Hammer Bounce In Slow Motion on Brocock Bantam/Compatto

Jump to latest Follow Reply
D

DrPutz

Member
Mar 18, 2017
242
31
Ohio, United States
I created some slow motion videos of the Brocock Bantam/Compatto Hammer to see what hammer bounce looks like. The Brococks have a great side window to see what is going on with the hammer. The videos are with no pellet, so there may be a bit less bounce with a pellet. I will need a better setup to safely try this. Hopefully you can see these ok, as I marked them unlisted. I will work on slowing them down further this weekend.

Slingshot Hammer Tuned to Reduce Bounce Bantam 177
https://youtu.be/tDJSv3IDh98

Same Bantam 177 without the Slingshot Tune, but Short Strong Spring
https://youtu.be/OwcEvQ0aHj8

Compatto 177 with a Short Strong Spring Tune with Regulator (1.33 fpe/ci efficiency)
https://youtu.be/t3ciTt0onTE

Compatto 22 26fpe Hunting Tune with a Short Strong Spring Tune
https://youtu.be/VyxA8rWegTI

Compatto 25 34 fpe Tune with a Short Strong Spring Tune
https://youtu.be/Zjc5nO8pyUc


 
Thanks dp.
You might find this sm of the FX system of interest. I made the originals of my FX Royal Elite, then Dan Brown did this one a little better with an FX Independence.
If you watch the valve stem on the left it is obvious there is no secondary valve openings.
By the sounds of the Brococks it would appear there is a chatter in the report indicating secondary valve openings. I could be wrong. ... Kind regards, Harry.

http://redirect.viglink.com/?format=go&jsonp=vglnk_148724009113614&key=0eff82a158b9bcd735539ea921a97f93&libId=iz87x422010009tm000TA3z071btvqetq&cuid=f-&loc=http%3A%2F%2Fwww.network54.com%2FForum%2F79537%2Fthread%2F1354003980%2FHammer%2Bstrike%2BSM%2Bvideo%2BFX%2BElite

 
Upvote 0
Do you have any gap between the hammer and valve stem when the gun is uncocked in any of those arrangements? In every one of those videos you can clearly hear the second or third + opening of the valve during the violent bouncing post-initial strike. 1.3 fpe/ci for a .177 is very poor unless that rifle is shooting near its peak velocity ie: 20+ fpe, in which case it would be nominal (imo). I have also slow-motion recorded my rifle during its shot cycle at 240 fps and further slowed down you cannot hear any 2nd opening of a valve. I use a custom made Spring Stop Guide (ssg) with a gap of around .03"-.05".

Both these videos don't show the hammer but you can clearly hear the shot cycle. First one slow motion second one real time. You wan't a single clean crisp POP, not a Pop, pop, brrpop.



These two videos are of a .25 cal marauder making 45~ fpe.



-Matt
 
Upvote 0
On the Slingshot video, I have about 1/16" gap between the inner hammer and the valve pin. The problem is you need way too much spring to get the inner hammer moving fast enough to get the energy up enough to crack the valve open, but then it is too hard to cock, even with a very light valve spring. I still have my valve leak, so will have to drain it again and look at the valve a bit more. The Harper valve opens on the side and I think there is a burr causing a problem.

On the strong short spring setups - I have about 1/16" to 1/8" gap between when the hammer and valve when it is uncocked. I think that all of the twangy and bouncing noise on the videos is the spring and hammer bouncing, rather than the valve. I think that after firing, the spring elongates, allowing some of the extra bounce. 

The 177 Bantam with a strong short spring is now putting out roughly 20.4 fpe with JSB Monster MkI, 3.6% variation (838 fps at 185 bar down to 808 fps at 150 bar for 60 shots) for 1.2 fpe/ci efficiency - I am tuning it for FT this spring. The JSB Monster MkII is put out a bit less fpe - probably because of their very large skirts. The MkIIs are shooting much better than the MkI - 0.62" at 55 yards on a breezy day in the cold yesterday.

I will try to get some videos of the business end today, if it is warm enough out. The ones of the muzzle end from inside indicate a short fast burp of air, but I am not sure if that is indicative of what the valve is doing yet. 
 
Upvote 0
You must log in or register to reply here.
Top Bottom
Back
Home
Forums
Resources
Menu