I was readng the last post about the Jukar holding the caps in the hammer piece. My Lyman GPR does a wierd but somewhat cool thing. when I shoot any load above 50gr FFFG the hammer blows back to 1/2 cock and sometimes full cock. It is the original nipple, there doesn't seem to be any huge powder burns anywhere, they are standard #11 caps, cci and old cva caps patched roundballs the patches appear ok no burn thrus the recoil isn't excessive. The caps are usually blown clear of the rifle. Is this dangerous or just another quirk of the sport that is muzzleloading?
-
Friends, our 2nd Amendment rights are always under attack and the NRA has been a constant for decades in helping fight that fight.
We have partnered with the NRA to offer you a discount on membership and Muzzleloading Forum gets a small percentage too of each membership, so you are supporting both the NRA and us.
Use this link to sign up please; https://membership.nra.org/recruiters/join/XR045103
"Semi-Automatic" GPR
- Thread starter cmdrted
- Start date
Help Support Muzzleloading Forum:
Kentuckywindage
62 Cal.
- Joined
- Aug 25, 2006
- Messages
- 2,529
- Reaction score
- 6
sounds like a weak main spring.
twotoescharlie
40 Cal.
- Joined
- Dec 1, 2005
- Messages
- 189
- Reaction score
- 1
or burnt out nipple
TTC
TTC
paulvallandigham
Passed On
- Joined
- Jan 9, 2006
- Messages
- 17,538
- Reaction score
- 87
Replace the nipple. Original nipples are NOTORIOUS for being soft, and wear out internally, opening up the hole, or Orifice, in the nipple. Lyman GPRs are not known for weak mainsprings.
To check the mainspring tension, put the butt of the UNLOADED gun on a bathroom scale, and take the "weight " shown on the scale for the gun. NOW, looking down at the scale as you do this, slowly cock the hammer from its rest position to full cock. I suspect the difference between the two measurements will be at least 20 lbs, more than enough tension to keep the hammer down on the nipple PROVIDED the nipple is in good shape.
To check the mainspring tension, put the butt of the UNLOADED gun on a bathroom scale, and take the "weight " shown on the scale for the gun. NOW, looking down at the scale as you do this, slowly cock the hammer from its rest position to full cock. I suspect the difference between the two measurements will be at least 20 lbs, more than enough tension to keep the hammer down on the nipple PROVIDED the nipple is in good shape.
That kind of stress and strain can't be good for the lock. Sounds like the hole in the nipple is too large. I'd suggest replacing it. I had that happen on an old double barrel pistol of mine and it ended up damaging the wood before I found nipples to fit it, which solved the problem.
- Joined
- Jun 12, 2005
- Messages
- 7,995
- Reaction score
- 1,003
agree with the consensus... probably not a safety issue, but it can't possibly be good for the lockwork. had a caplock pistol which did this to halfcock- quite disconcerting and never could get it to pattern, so i used it in a bit of 'horsetrading' and replaced it with a c&b revolver. (i did tell the new owner about the problem, and he shared the opinion that a new nipple would most probably fix the problem).
make good smoke!
make good smoke!
Tumblernotch
69 Cal.
- Joined
- Feb 26, 2005
- Messages
- 3,370
- Reaction score
- 11
I would fix it. It may not cause a problem with a solid tumbler, but I had a stirrup type tumbler break from sudden blowback that threw the hammer back past full cock. Plus it put a dinger in the stock.
It would also pay to look closely at the threaded part of the nipple from time to time for erosion. I bought a gun from a feller years ago that had a nipple in it that hadn't been taken out for a long time, and the gun had been fired with heavy loads. There was a big hole in the threaded portion and the gases had eaten into the threads of the bolster. I had to drill it out, re-thread it and make a threaded liner for it.
It would also pay to look closely at the threaded part of the nipple from time to time for erosion. I bought a gun from a feller years ago that had a nipple in it that hadn't been taken out for a long time, and the gun had been fired with heavy loads. There was a big hole in the threaded portion and the gases had eaten into the threads of the bolster. I had to drill it out, re-thread it and make a threaded liner for it.
cowpoke1955
58 Cal.
- Joined
- Oct 23, 2006
- Messages
- 2,090
- Reaction score
- 6
I agree with replacing the nipple. Replace the factory nipple with a Spitfire or Hot Shot nipple in .75 X 6mm thread. I had to replace the one on my GPR after a couple of years. The nipple became so deformed it wouldn't pop the caps anymore. After replacing the nipple, I haven't had any problems. It has been about 27 years and still going :thumbsup: .
jtmattison
70 Cal.
- Joined
- Mar 17, 2004
- Messages
- 4,686
- Reaction score
- 8
cmdrted said:
It's not good. As the others have said you may have a weak mainspring, which I doubt because GPR's have a coil spring. I'd vote on a burnt out nipple. Once the hole gets too big it allows blow back enough to reset the hammer. I've had mine go to half-cock but never full-cock.
Get a new nipple. I recommend a hot shot nipple.
:thumbsup:
HD
rafterob
62 Cal.
Also, you did not mention the powder you are using. The substitutes burn hotter and may contribute to gas burn. Although you say this is new out of the box so gas burn may not be your issue. I have seen nipple holes, nipple threads and clean out screws blown through. The threaded portions often look like a groove was filed into them.
Even if the gun (and the nipple) are brand new, that doesn't mean the nipple is good.
If there is anything that is not excellent about Lymans imported guns it is their nipples.
They have a tendency to break and it wouldn't surprise me a bit to find that some of them were made with oversize holes thru them. (It should be around .028 which is slightly smaller than 1/32 of an inch and I'm speaking of the tiny hole that is down inside the nipple, not the large counterbored hole that is at the top of the nipple).
If there is anything that is not excellent about Lymans imported guns it is their nipples.
They have a tendency to break and it wouldn't surprise me a bit to find that some of them were made with oversize holes thru them. (It should be around .028 which is slightly smaller than 1/32 of an inch and I'm speaking of the tiny hole that is down inside the nipple, not the large counterbored hole that is at the top of the nipple).
Tumblernotch
69 Cal.
- Joined
- Feb 26, 2005
- Messages
- 3,370
- Reaction score
- 11
Zonie said:
I bought some nipples at the York shoot last year. The first one I put in a rifle I just built and within the first 5 shots had mushroomed enough that I couldn't cap it. I made a holder for it so I could put it in my lathe and filed it down so that the caps would fit. I then casehardened it. Have had no problems since, looks and acts like new. I went ahead and treated the other the same way. These new nipples are way too soft.
On the other hand, I have a Richmond rifle-musket that I bought in '83 that still has the original nipple on it and virtually no sign of wear, inside or out. I lost count of the rounds through it. One of my planned projects soon is to start making my own. Why pay for something when you're going to have to re-make it to make it work?
:thumbsup:
paulvallandigham
Passed On
- Joined
- Jan 9, 2006
- Messages
- 17,538
- Reaction score
- 87
I learned to avoid nipples made of blued steel. They always tend to be soft, and short-lived. I buy stainless steel nipples, which can also be soft, but tend to give good service for some time. It all depends on the strength of the mainspring, as to how long the nipple lasts before it begins to expand toward the top enough to make fitting a cap on difficult. I have used both fine files and India stones to remove the "bulge" from the nipples to keep them going. Unlike the blued steel versions, the stainless steel models don't seem to burn open the orifice in the nipple.
I am going to look at both the Spitfire, and the Ampco nipples the next time I am near them, and spend the extra money to see if I don't finally get a nipple that I can depend will last for more than one year.
I am going to look at both the Spitfire, and the Ampco nipples the next time I am near them, and spend the extra money to see if I don't finally get a nipple that I can depend will last for more than one year.
jtmattison
70 Cal.
- Joined
- Mar 17, 2004
- Messages
- 4,686
- Reaction score
- 8
Zonie said:
It's funny so many folks on here have made that claim but I have never had a problem with a Lyman nipple. Mine have all lasted for a very long time. I've only had to replace one so far and that was after several hundred shots with heavy conicals.
HD
cmdrted said:
You need a new nipple and make sure it fits.
If you keep shooting it you will eventually break the lock or something related..
Could be a weak mainspring is contributing but it should not blow back at all.
The first clue is hearing the hammer restrike the nipple just after the shot, then it blows to 1/2 cock, then full cock if it has sufficient velocity the hammer being blown back can damage the internals.
Change the nipple for a new STEEL nipple. If it still does this it needs professional help.
The hammer blowing back is a danger signal.
Avoid "trick" nipples. The things are designed to sell to people who never do accuracy testing. They increase the velocity spread and degrade accuracy. Or so some of mu finicky friends have found out. But more people don't do the testing.
Dan
