View Full Version : Question About the Lyman Great Plains Rifle

January 25, 2011, 02:29 PM
The GPR has a cleanout screw for the percussion "snail". The screw is simply a set screw type design with a female Allen head receptacle on one end. When I purchased the rifle (used), the screw appeared to only be tightened part way. About 1/2 of the threads were exposed. After removing the screw for cleaning, I noticed that the screw easily goes in deeper before meeting any resistance.

My question is: Does the depth of the screw have any impact upon ignition when the cap is popped? I would prefer that the screw be fully seated; but I don't want to do it if there is some reason why the previous owner left it protruding part way. I cannot find anything in the Lyman user manual that addresses this point.


The cleanout screw as installed by previous owner.

The cleanout screw installed fully seated

January 25, 2011, 02:47 PM
I think the original screw is a round head screw with only about 3-4 threads. If you screw that set screw in too far it will hinder ignition or bottom out on the nipple threads and possibly ruin them, and if you leave it sticking out, you will snag it or loose it.

January 25, 2011, 02:47 PM
That screw appears to be longer than the one on my percussion GPR, so perhaps it's a replacement screw.

Take the nipple out, install the screw to the depth you want, and see if it interferes with the nipple opening; keep in mind the nipple threads enter the chamber, so its possible that the cleanout screw might interfere with the nipple threads if fully installed. You should be able to see if that cleanout screw interferes with the area immediately under the nipple flash hole (center of the nipple opening). If not, I see nothing wrong with screwing it down.

January 25, 2011, 02:55 PM
mykeal + 1
That would be my call and have seen it in simular M/L's. Most recently, on a Traditions Tennessee .... ;)

Be Safe !!!

January 25, 2011, 03:51 PM
Also agree with mykeal.

If after you do as mykeal suggests, and if you find the set screw interferes with the nipple, you may be able to find a shorter set screw at your hardware store.

January 25, 2011, 05:01 PM
A set screw is historically incorrect. It should be a round head screw with a stright slot.

January 25, 2011, 11:16 PM
Thanks for all the replies, guys.

First of all, I'm convinced that those of you who say it isn't the original screw are correct. I've surfed the Internet for close-up pictures showing the screw on other GPRs. All those that I found show a slotted head rather than an allen type receptacle.

I can't find anything that defines the length of the original screw; but I'm betting the one in my rifle is longer. I did some checking for interference with the nipple (as mykeal) suggested).

If I remove the nipple, the clean-out screw will insert fully. Then, when I install the nipple, the bottom edge of the nipple will contact the clean-out screw and stop short of full insertion (probably two threads short).

If I reverse that process and fully seat the nipple first, then the bottom of the clean-out screw will contact the nipple base and stop a few threads short of full insertion.

I suspect that the original owner lost the standard screw; and replaced it with a set screw which had matching threads, but was fractionally longer. Apparently, his solution to the interference problem was just not to insert the screw deep enough to contact the nipple base.

The rifle fired fine without issues with the non-standard screw; but I went ahead and ordered a correct replacement from Lyman earlier tonight.

Once again, thanks for everyone's help.

January 27, 2011, 10:32 AM
The original screw was a slotted set screw. Screwed in flush, the reason it is there is it closes the channel leading in to the powder chamber.

It is not really a clean out screw, during manufacture they had to connect the flash channel to the powder chamber and drilling is the easiest method. The best way to close it is a screw. It makes for a great cleanout plug.

Lyman list the screw as a cleanout plug Part number 6030123.

And it is NOT a round head screw.

January 27, 2011, 10:42 AM
It is not really a clean out screw......Lyman list the screw as a cleanout plug Part number 6030123.

Then why do YOU think Lyman lists it as CLEANOUT plug?

January 27, 2011, 11:29 AM
Lyman uses that name in their parts catalog because that's the term used in the popular lexicon. People who are not generally well versed in gun parts would look for it under that name.

I've never needed to remove it for cleaning the flash channel, but I'm sure many people have. I believe it's original function was to simply close out the hole used to drill the flash channel on production line guns, but it can certainly be used to provide access for cleaning. So, why not call it that?

January 27, 2011, 11:36 AM
It will be interesting to see what Lyman ships to me.

A shooting buddy called his brother who also owns a GPR. The brother checked his rifle; and it also has an Allen head set screw. Yet, I have found pictures on the Internet showing a slot head configuration. Perhaps, Lyman used different types during certain years of manufacture???

I am more concerned with the correct length of the screw than anything else.


January 27, 2011, 11:52 AM
Mine's a slotted head also. And it's short enough that when the head is flush the end does not contact the nipple threads.

January 27, 2011, 11:59 AM
Lot of good replies. Whether it is a clean out plug or screw, it doesn't matter. It is not needed. Once you seat a proper length screw, forget it is there. You simply do not need it for cleaning.
Maybe some of the originals had something like that but I have never seen it. Nor have I ever seen one on fine custom made rifles.
It is a modern notion. Or as someone said, a part of the manufacturing process.

January 27, 2011, 12:02 PM
What year production is your GPR? Mine is 1999.

January 27, 2011, 12:05 PM
Maybe some of the originals had something like that but I have never seen it.

Now you can say you've seen it....


January 27, 2011, 03:33 PM

February 14, 2011, 05:49 PM
In post #7 I mentioned that I had ordered two additional screws from Lyman.
The screws finally arrived in the mail; and they are exact duplicates of the screw that was already in my gun....same length with Allen head. It appears that Lyman has used both Allen heads and screwdriver slotted head screws at different times during their production of the GPR.

February 14, 2011, 06:04 PM
Now I remember what I was going to post...as the official thread derailer, I was going to post this picture:


A year later, junkman, Col. Colt "improved" it!:D

February 14, 2011, 08:20 PM
And my Navy Arms 1863 Springfield doesn't have a clean out screw either...


February 14, 2011, 09:23 PM
"And my Navy Arms 1863 Springfield doesn't have a clean out screw either..."

But the 1855 and 1861 Springfield and Fayetteville and Richmond rifles and carbines did. Also the Smith, Merrill, and Gallagher carbines. The percussion Sharps rifles and carbines had cleanout screws in the breech block too. Never seen a "fine custom made gun" with a cleanout screw?? Look on pages 44/45 of Echoes Of Glory: Arms and Equipment of the Union at a "fine custom" Morgan "sniper" rifle, and pages 50/51 of the Confederate book for a "fine custom" Leonard "sniper", both with cleanout screws. That's not to mention countless civilian guns from both before and after the civil war. Cleanout screws were quite common on early muzzleloaders. Some had them, some didn't. It is in no way a "modern notion". The term cleanout screw also has nothing to do with the popular lexicon. That is what it's for. Weather it is needed or not is up to the user.
But that's not the topic of this thread...........

I have a Cabela's "plains rifle" from about the mid 90's made by Investarms (same maker as the GPR) with the slotted cleanout screw. I have a GPR and the plains pistol from about two years ago with the allen screw. Investarms changed the screw. Mystery solved.