Point of aim movement

[M. De Land]

I was watching Kibler assemble his So. Mtn. Rifle kit the other day and he mentioned that when drilling the pin holes in the barrel lugs that they needed to be elongated to accommodate the stock length expansion in Tiger or Curly maple stocks from moisture changes in the cross grain wood structure. He said it was not necessary with walnut or cherry stock wood. Any of you builders ever notice this? Kibler said he has only seen it a few times in historic guns but has in a few.

 

[Flint62Smoothie]

... and here I thought it was due to metal barrel heating up from firing? As every builder I know does it, at least as represented by the dozen or more BP flint or earlier ignition arms that I have on hand show, stocks of maple, walnut and cherry.

 

[Britsmoothy]

Yeah when you read of shifting zero after the first shot and opening groups this is the first place to look.

 

[Many Klatch]

Regardless of whether it's the wood moving or the barrel moving, it's a good idea to elongate the barrel lug holes for the pins. A binding pin will throw off your point of impact.

 

[Tom A Hawk]

This subject is discussed in Chapter 10 of Recreating The American Longrifle. While its hard to imagine heat deflecting a 1" barrel perhaps its a good reason to use keys rather than pins.

 

[Britsmoothy]

This subject is discussed in Chapter 10 of Recreating The American Longrifle. While its hard to imagine heat deflecting a 1" barrel perhaps its a good reason to use keys rather than pins.

Yes it will. Even a stock will offer resistance along one plane and induce a curl in the barrel even if only slight. Add some stress and it will go sideways too.
Heat is energy and it has to do something.

 

[87TT]

I don't see how keys would behave any different but heat and moisture , yes.

 

[Tom A Hawk]

I don't see how keys would behave any different but heat and moisture , yes.

With keys and staples there is room for longitudinal movement within the staple.

 

[87TT]

I think you're right but slotting the underlugs should accomplish the same result.

 

[Grenadier1758]

Slotting the underlugs does account for the stock movement and barrel movement. It should be done for all muzzle loader stock attachment.

 

[87TT]

My PR SMR kit should ship today or tomorrow and I plan on it.

 

[M. De Land]

I think I will pull my three keys and give them a "waist" where they go through the staples, just to be sure.

 

[fire bear]

M. De Land, any chance you could post a picture of your key's with a waist so I can see what you are talking about? Thanks

 

[Tumbledown]

For pins, just how much of a slot are we talking? How does one do it?

 

[Many Klatch]

For pins you must widen the hole maybe a 1/16" inch on both sides. It doesn't take much. Make sure the pin doesn't bind.

As an experiment you can pull the pins from a gun that has started "wandering" with a hot barrel. You will find that it will shoot better. Remember, the pins are only there to hold the forearm of the stock to the barrel so there is a place to hold the ramrod.

 

[EC121]

Norman Bates used to shoot a rifle in line matches with the barrel taped in using electrical tape. Supposedly they were test firing the rifle before finishing it. It was so accurate that he took it as is without pins or finish. With fouling and handprints all over the wood it looked really bad, but if he showed up, everyone else finished down one more place.

 

[Britsmoothy]

Norman Bates used to shoot a rifle in line matches with the barrel taped in using electrical tape. Supposedly they were test firing the rifle before finishing it. It was so accurate that he took it as is without pins or finish. With fouling and handprints all over the wood it looked really bad, but if he showed up, everyone else finished down one more place.

Was he the motel guy?

 

[sawyer04]

I think I will pull my three keys and give them a "waist" where they go through the staples, just to be sure.

I make sure there is waist on the key. Keys are meant to hold the steel down and not forward or backward. Good point sir De Land.

 

[M. De Land]

M. De Land, any chance you could post a picture of your key's with a waist so I can see what you are talking about? Thanks

I will do it soon and post a picture. It simply is key width removal on both sides (for and aft) between the staple ends when the key is fully inserted. Think of an hour glass shape. It only requires perhaps .010 on either side and can easily be done with a file.

 

[M. De Land]

For pins, just how much of a slot are we talking? How does one do it?

On Kiblers video he did it with a jewlers saw after positioning and drilling the lug hole. The round blade comes loose from the saw bow, is inserted through the lug then the blade is reattached to the saw bow and the hole is lengthened in both directions horizontally from the original hole. It is important with pins that the "upindicular" (gun mechanic term) be maintained, only the width elongated.