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8 bore percussion woes - revisited!!
This is a follow up to my post earlier in the year, the original went AWOL following the forum server crash!!
Following some persistent ignition problems, and after carrying out some intrusive work to the breach plug, my big 8 behaved flawlessly for the next two outings, shooting 30 big loads on each occasion. However, at the North of England Championships last Saturday, the problem returned after about 20 shots.....
The nipple stays clear, the musket cap fires every time, I clean the gun thoroughly after each use, I load with the hammer down, I can only assume it is fouling build up in the transfer port preventing the powder charge getting under the nipple. I am using Swiss 4 (1 1/2 Fg) as recommended. The only difference from last Saturday and the previous two outings was perhaps the weather, Saturday had a very cold start and maybe moisture in the air is the problem coupled with large grain size?
Your thoughts on this frustrating issue are most welcome.
I suspect that your original 8 bore was nippeled for F4 3/16 caps.These were made for large bore guns and Live pigeon guns and were foiled and laquered to stop damp intrusion..THEY WENT "BANG" EVERY TIME !! I believe they were the most powerful cap made by ELEY,successors to F.JOYCE & CO.LONDON. ENGLAND. I used them at Internationals  and Worlds on my STENSBY from 1974 to 1997 and never had a Misfire. FORGET CHUR WHEN I USED THE WILLIS WITH CCI CAPS..JANES "MISSFIRE MIKE"!!!! comments..
They are difficult to find but if they come up at actions BUY BUY BUY. They I'ant Mecany more.  OLD DOG   
The only alternative is to re-nipple and use Fiocci Brass caps but they are corrosive.If you can find them..OLD DOG
I witnessed your misfires last Saturday, very frustrating. Because of the larger surface area per unit mass, a smaller grained powder is more susceptible to damp than the larger grained variety which you were using. Because of this  I wouldn't have thought the relationship between grain size and dampness would be the problem. I wonder if you loaded with the hammer on half cock and rammed the first wad down with gusto, the flow of air through the nipple may encourage the powder to get further into the breech. To enable this to be more effective and give you more airflow you could open up the small diameter of the nipple a tad. I always load my gun with it on half cock on the principle that any residue from the spent cap will be forced out by the flow of air.
Hi Bev, I do ram a single card down over the powder with as much force as I can muster as per your previous advice. I have taken to loading hammer down also as per advice received. Having said that, I can see the logic of half cock loading particularly as I think the issue is the tight transfer port get clogged up with powder residue after a few shots. Also clearing the nipple of any cap residue has got to be good.
On the nipple front, I did try changing over to a traditional big bottom, small top hole style one part way through Saturday in the hope that the powder would find its way further up the nipple.  This didn't seem to work, however I didn't try it at half cock though.
With regard to grain size, if the transfer port is choking up, a finer grain powder would presumably have a better chance of getting through. Perhaps I should try Swiss 3? As you have said previously, it does kick excessively with swiss 2 or even Czech (Vesuvit) so probably best to stay clear of loading it with that.
I will try loading at half cock next time out.
Any further thoughts anyone?
I had the same problem with my 8 bore, the cure was to pour 5 grains of Swiss No 2 powder down the barrel before the main charge. This flowed under the nipple and ensured ignition every time.
Thanks for that option. When it wouldn't fire off, I borrowed some Swiss 1 from the flinter boys (and girls) straight down the nipple hole, it went then!!!
So, "Bertha" was allowed out of the naughty cabinet yesterday. She hadn't seen the light of day since April in Yorkshire. It was a club friendly competition with charge/load limits, so reduced loads for an 8b were used. I am wondering if this is the issue with the my misfiring?
After 18 or so shots without problem, I got the usual misfires and some hangfires. The cap goes off but the charge doesn't. Having a good look and prod down the nipple shows the nipple to be clear, but obstruction in the breach passage to the acorn, so no powder under the nipple. Poking this through then inverting the barrel releases grey flaky combustion products which I assume were the cause of the blocked passage and consequently preventing powder getting through under the nipple. Once clear, the gun behaves for a while, but will then play up again with the same issue. No amount of whacking the gun to settle the powder and quick ramming with hammer half cock seems to be able to shift this build up and allow the powder to flow under the nipple. Strangely, or maybe not, with a good charge/load there doesn't appear to be a problem as it shot well after the competition when stoked up. I am using Swiss 4 powder.
Has anyone had similar experiences with big guns and light loads? Maybe I should only use it with big loads as intended? For the next national comp (big bore- no load limits), I will use it for this comp only (unlike Yorkshire), but will have some swiss 2 to hand as previously suggested and a nipple primer.
It seems that this problem is a regular thing but why , has I have said before always reload with the hammer down, Using Swiss powder is throwing money away any type of black powder should ignite  with no problem  but just seat your card wad on the powder , a main fault is to continue  tamping the wad thus caking the powder which may be your main trouble .
My reasoning for loading at half cock is as per Bev's comments above, which I believe to be sound. Larger grain powder and small nipple hole does not allow expulsion of powder through it, but does allow air to escape.  The breach plug on this gun is NOT a Nock patent type with a nice big transfer port leading from the apex of the acorn to the underside of the nipple allowing an easy flow path for the powder. It has instead the port entering the acorn perpendicular to it and down from the apex, if that makes sense. The port was quite small in diameter and I have previously opened this up as best I could with the limited access for tools. I also polished the acorn and cleaned up the bowl area under the nipple to achieve a better flow for the powder as per DEVA's comments previously.
I do not tend to ram the powder once the wad is seated over it. I still believe the issue to be fouling build up in the breach area, probably in the transfer port, which is the cause of my problems.
So how to reduce the fouling? hence my question on lighter v heavier loads. I like Swiss powder for its velocity performance and generally cleaner use, but now understand that it can be susceptible to fouling particularly in hot weather, which it was on Sunday gone. Suggestions for another powder to try, or any other thoughts please. Bear in mind this is a large 8/1 bore with 42" barrel.

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