Safely use musket cap conversion nipples with Lyman GPR?

[Naphtali]

Several vendors offer conversion nipples for Lyman's Great Plains Rifles that convert from using #11 percussion caps to using musket caps.

While this appears useful on paper because of additional brisance of musket caps, has anyone used this conversion successfully?

1. Does musket cap have space and clearance within GPR's hammer nose?

2. Does musket cap project too high for proper impact and ignition?

3. Lyman specifically states not to use musket cap conversion. I cannot imagine a SAFETY REASON to avoid them. Any first-hand information will be appreciated.

[quickdtoo]

This is just my opinion, but it may be because the cup in the hammer isn't big enough to prevent debris from the much larger musket cap from hitting the shooter's face. That said, I know lots of hammer gun shooters that have removed the cup entirely and/or bent the hammer to allow the hammer to fully hit the cap without any issues. Musket cap conversions are the go-to ignition for us Washingtonians that must use original percussion type caps for muzzleloader seasons.

[filmokentucky]

Musket caps seem to be be made of stouter stuff than the smaller ones.
I've never had one break up on me. Still, I would be a bit nervous lighting
one off with an un-cupped hammer. Even wearing my glasses. Bits of copper sticking out of my nose would sure spoil my day--and my nose.

[Naphtali]

I'm confused by the first replies. Lyman's percussion lock is not well made. Its hammer face is concave — that is, it envelopes a #11 nipple's nose.

I have no idea whether the nose covers a musket cap the flaps, but rupture or no rupture it would appear to capture a disintegrated musket cap because of the female hammer nose.

quickdtoo: I recently moved from Skagit County. I usually use flintlocks. Ain't temperate rain forest great?
**********
Guys, I'm aware of the theory, but I'm short on first-hand experience with the nipple conversion. So I guess I must buy caps and nipple and just try it for myself.

Remember the motto of every unindicted politician: Who Blames First Wins!

[lostid]

the concave hammer face isn't really a design flaw,besides being a hammer to strike the cap,,a hammer/spring mechanism is made to hold against back pressure. When folks talk of true accuracy in cap lock rifles nipple wear and gas cutting IS an issue. One of the indications of nipple wear is the lock being forced back to half-cock after firing the round/shot,,,too much gas is "escaping" back through the nip and not pushing the projectile forward.
 The problem with using a 6x.75 mm Musket cap nipple on the Lyman type arms is the nip is too long for the hammer to directly strike the surface of the cap/nip. Thus the conversion,,or bending, filling, cutting of the hammer and filling the nip to angle,, too fit the musket cap, with a direct fall of the hammer.
 Now heres my point; Yes a Musket cap is larger and there-fore capable of "hotter" ignition, yet the same nipple has a larger hole at it's base allowing more gasses to escape and putting pressures on springs and hammers that weren't designed for it.
 
 Bottom line. given the success of the gpr/h firearms, as hunting and target rifles, with grand results,,wouldn't the manufacturer offer "Musket cap" models?? as best for the rifle? Buyer beware.