Lyman Great Plains Percussion Snail ???

[Prairiewolf]

First off, I just got my first muzzleloader a few weeks ago, a Lyman Great Plains 50 cal.  I LOVE IT!  Lyman desribes it as having a "Hawken style percussion snail with clean-out screw...."  What the heck is a percussion snail?   A gastropod the plays the drums?   (I've known a couple of drummers that could have used clean-out screws!)   

My rifle shoots quite low with the rear sight all the way up.  I'm trying to decide whether to file down the front sight, and file it narrower also, or to replace the rear sight  with the Lyman receiver sight (57GPR).  Does anyone use the Lyman receiver sight?  Which front sight?  I have tang sights on some of my other rifles and really like the "peep" sights. 

[necchi]

"Snail Breech" means;
 Well, it's the way they drill the hole in the breech. (It's a good thing) The end of the bore is actually where the breech begins, right? They drill straight down a short ways into the breech, then a smaller bit is used at an angle towards the nipple, then another smaller one at a steeper angle reaching the hole the nipple is tapped into.
 Lending the end result of a curved hole directly too the nipple in a curl, like a snail.

 The advantage is the main charge enters the breech and with a rap on the side of the gun actually settles into the hole directly in front of the nipple. The nipple flash now has direct access to the charge, and the charge is ignited from the rear and burns directly forward. It's not really new technology, that style breech has been around for 150yrs, but there are still available other styles that lead the nipple flash to the side of the main charge.
 Disadvantage is, this is a wonderfull place for storage oils and gunk to build up. It's really not an issue if proper cleaning is done with plenty of soapy water.

[coyotejoe]

Necchi, that's a pretty good job of explaining the internal configuration of a chambered breech but I always thought "snail" referred to the outside appearance of the nipple bolster which was often filed to a snail shell shape. Funny how we have different understandings of terms we both have probably used all our lives.
Filing down the front sight to raise elevation is a very common method of sighting in a muzzleloader, but if you like peep sights the Lyman #57 is a very good one. I use peeps on my hunting rifles and wouldn't have anything else but if you ever want to shoot at a rendezvous or black powder match you should be aware that they often are limited to open sights only.

[bub524]

The "snail" refers to the outer appearance of the breach plug. On some of the older rifles it was shaped like a snail as opposed to a drum and nipple arrangement. Look at a Browning rifle, an old Sharon or Santa Fe Hawken. A GPR doesn't have a "snail".
The breach plug face has a hole drilled into it. Then a lateral hole is drilled from the side of the bolster to the first hole. Then the nipple hole was drilled down into the second hole and the lateral hole plugged with a screw. If you see a screw there thats what was done.
But now I see thats pretty much what Coyote Joe said.

[necchi]

I think we'er talkin about two different things
*Snail Breech
*Snail Bolster

an your pretty far off there bub, the existance of a clean out screw doesn't mean it was drilled there for the breech. Just look inside the hole for the nipple, how can they tap a hole smaller than the drilled hole?
Weld it then drill an tap again?

[coyotejoe]

The Lyman, T/C and Investarms chambered breeches I've seen have a hole drilled straight through from the outside into the chamber below and connected to the nipple hole. That lateral hole is drilled with a #8 screw size tap drill, then the outer end is tapped 8x32 for the clean-out screw which really is just a plug for the hole. I have cured faulty ignition on some by re-drilling the flash channel for a 10x32 plug screw.
 Some T/C's, like the New Englander, have the lateral hole drilled from the opposite side and the open end plugged with a screw having it's head ground off so that it is not removable. In either design you have the lateral hole from nipple to powder chamber dilled with a standard tap drill and the open end of the hole tapped for a plug screw.
 Some custom versions of the chamberd breech (also incorrectly called a patent breech) avoid the plug screw by drilling the flash channel from the powder chamber at an angle upward and outward to meet the bottom of the nipple hole. Some think this a good idea  since it eliminates the 90 degree bend from nipple hole to flash channel but the flash channel is still a long and small diameter hole so I doubt that design offers any real improvement. That is pretty much the only two ways the nipple hole can be connected to the powder chamber in a bolster breech, either drilling across from the outside and plugging the open end or drilling at an angle from the powder chamber.