One More Try; KRB-7 and BH209

[wildhobbybobby]

In a previous post I described how I had a local machine shop drill out the flash hole of the breech plug of my Knight Rolling Block to .035" in hopes of eliminating hangfires with BH209. The larger flash hole did not solve the problem. I took the plug back to the machinist and asked him to put a dimple in the front face of the plug. Due to the thinness of the web of the plug, we didn't dare take off much material, but I hoped that the dimple would focus the flash energy enough to ignite BH209 properly. The modified plug looks like this:

Well, I took the rifle to the range today and fired a couple of shots. The good news was that there was no blowback, but the bad news was that the hangfires still occurred on every shot. One was nearly instantaneous, but the other was like shooting a flintlock.

Sadly, I am giving up trying to make BH209 work in the KRB-7. I sure hope Knight comes up with a solution, because there is too much potential here to be wasted.

 

[frontier gander]

An amateur with a flintlock or a seasoned flintlock shooter? Huge difference between the two :wink:

 

[cayuga]

Well you tried as much as you could, and for that you should be commended. I guess all you can do is wait for a change in the rifle design. Until that time, at least you know the rifle is a shooter with other powders.

 

[paia]

Disappointing news, but still a great report. I appreciate the info and admire your work with the KRB. And I bet Knight comes up with a solution pretty quick.

 

[big6x6]

Honestly...
Knight needs to look long and hard at the KRB and try to correct the hangfire issue. They have a lot to gain if they do..and potentially a lot to lose if they don't.

Great effort WHB!

 

[Underclocked]

I don't see any way to modify the "block" section to lock it forward without adding a lot of clutter and cleaning hassle. They would be better off with a complete redesign than to attempt any modification to the current design. Even if you made some sort of snapping lock that might fit that recess between the rabbit ears, that would only hold it at the top.

The bottom is pivoting on a ball-bearing and spring pressure. It slides rather easily forward and aft without that spring pressure. Maybe a stronger spring at the bottom and some sort of latch at top would combine to be enough to hold. That would do current owners very little good, if it DID work. The alloyed body of that trigger/hammer assembly coulld be another concern so far as locking strength.

I wonder if Knight could perfect a ball-check breech plug that would only allow unrestricted flow in one direction. I think that has been attempted before.

But I don't really see that idea as a practical solution. The plug would be expensive and probably not hold up to use well.

There are a lot of things about that design that probably involved bean counters more than engineering.

 

[big6x6]

IMO...for blowback to get to any sort of dangerous level..or even to the nuisance level wouldn't the blowback have to MOVE the block and hammer? No way for it to get to anyone without moving all that..

STILL the best thing Knight could have done would have been to copy the Omega/Apex design... Maybe they are just stuck on being able to remove the trigger assembly?

 

[Lee 9]

I thought because of the longer length of the breach plug the Triumph might have a problem but I have been through two cans of BH without any sign of a problem. Can some one identify just exactly what is causing the problem? I had in mind to buy one untill I found out they do not function properly with BH know I am wondering if there might be a impreceperable lag with all powders. Lee

 

[wildhobbybobby]

I have fired the rifle with Pyrodex, using the plug as it came from the factory with no problems and great accuracy. So, it appears that the only "problem child" powder with the KRB is BH209. Sigh...

 

[Underclocked]

Mine gives the tiniest amount of leakage now as there is a very slight amount of residue on the underside of my scope above the closure area. I believe that is unavoidable due to the "gap" left between the hammer and "block" when the hammer is down. Reducing that gap would make manufacturing a more expensive process, I'm sure, and it also would have impact on trigger function. There is also the matter of imperfect fit at the forward section of the block where it is overlapped a bit by the barrel.

If you close both those gaps as much as is possible, there is still the issue of strength of that alloyed assembly.

The hammer probably rebounds ever so slightly upon impact with the block. That rebound might be long enough in time duration to eliminate its mass as an aid in prevention of leakage. The gaps then take the lead role.

Butt, ah dunno.

 

[BPHunter]

The KRB7 positions the 209 primer close to the breech plug, but doesn't provide a tight seal. I noticed there's a bit of a gap and I was never concerned when using Pyrodex P or other subs. I read the reviews and recommendations carefully and realized before I bought some that it probably wouldn't work well in the KRB7. I like shooting big conicals and thats another weakness of BH209, as they don't recommend anyhting over 350 grains. I bought the powder specifically for my Omega, which shoots Powerbelts and sabots extremely well, but suffers a great deal from the dreaded crud-ring. BH209 works extremely well in this situation. I still use Pyro-P for my KRB7 and White .504 UltraMag.

 

[Joes]

Wildhobby just get a Knight Extreme plug and use it in your KRB problem should be solved.