Lyman Great Plains Rear Sight too small ?

[Zerstoerer]

Got myself a nice Lyman Great Plains Rifle.
Nice gun, great stock and very accurate.
Only problem is that the gun came with an adjustable rear sight installed and my club only allows primitive, fixed sights.
The gun comes with a fixed sight also, so I bang out the adjustable one (per directions left to right) and try to slide in the fixed one.
Problem is that it slides right through the dovetail cutout. The adjustable one was very, very firm in the cutout and I was already concerned that I forced it through the wrong way, but the instructions clearly say which way to do it.
Is it even possible to enlarge a dovetail by forcing a sight through the wrong way?
So I called Lyman and told them about it. They send me a replacement rear sight which-
Slides right through! A handwritten note says that I ‘may need to peen over the sides of the dovetail in the barrel to hold the sight in’.
What does that mean? How do I do that and why do I have to do play gunsmith if all Lyman had to do is make a correct size sight (like the first one).
Are there other sights available on the market that might just fit?

 

[arcticap]

In this case peening is to expand the metal surface by working or hitting it with a blunt object like a hammer or a metal punch.
Folks place a punch around the edge where the base needs to be expanded and hit it to spread out the metal enough so that the part will fill the empty space in the dovetail.

Lyman probably makes & recommends peening a smaller sight base instead of filing a larger one because filing is delicate work and may lead to the part being made too small which is the same result as making the part too small to begin with.
At least if the part is too small you're not damaging the dovetail, only the sight which they have replaced for free anyway.
So now you have an extra sight to practice peening on.

 

[Zerstoerer]

That makes sense, thanks for the quick answer.
The included instructions said:

"You may need to peen over the sides of the dovetail in the barrel to hold the sight in"

I understood it the way that I would need to hammer away on the gun, not the sight.

 

[Zerstoerer]

arcticap,

I just hammered the base of the sight down a bit and it works!

Thanks again for the advice, I love this forum.