So just recently I picked up an old single shot bolt action rifle. It is a very heavy barreled 22LR with a 25" or so barrel. The rifle has a comfortable target style wood stock.

The rifle has a nice globe sight on the front with removable inserts and a receiver mounted peep sight.

I was thinking about cutting the barrel length back and maybe threading it, to make the gun a little easier to maneuver with, and fix the crown as it looks a little rough.

I was thinking about having the muzzle re-cut for the globe sight (standard 3/8" dovetail) and reusing the front sight with the shorter barrel length.

The issue is that I am thinking about going from the full 25" barrel that it's at now, to a 16" or 18" length.

How will this reduction in barrel length effect the front sight? Will I have too much issue re-zeroing the rear peep sight? I don't mind putting a new-manufacture front sight on it with a taller or shorter height to make the rear sight work. Would I need a taller or shorter sight?

What do you guys think?

Is the barrel straight or tapered?
Depending on the taper of the barrel, I'd think you'd possibly end up needing a shorter front sight if the rear sight adjustment can't take up the difference..

I think the barrel does taper, but very little. The barrel is about the same size diameter as the reciever, not sure if that helps.

You could also switch to the old school Redfield and Lyman style target rifle front base.   IIRC they're not dove tailed they're held on with screws.   You can buy various height bases or even stepped bases with 2 heights so for major changes in height.  (indoor short range for one and a different height for outdoors 100 yards).   As I recall without going to the safe for my 40x, the underside of the base is round to match the barrel contour and is held with 2 screws.   They Redfield Olympic I have attaches with a crossing thumbscrew.

Lyman makes a decent small globe that is still in production for not a lot of money.   The Redfield Olympics are quite large and it took me awhile to warm up to them with their glare sheild face.

You're probably going to be regretting cutting down the barrel on a (presumably fine ?) old target rifle, someday.
They were designed with long barrels (and the accompanying long sight radius) for good reasons.
Just my opinion.

From what I can tell, the rifle is a Schultz & Larsen M70, their base model / entry level target gun. They were used for "club guns" from what I read.

I will try it with the full length for sure, but I was just curious about if it would work.

The one I have is in pretty good shape, but is definitly used. Not like I'm chopping up a pristine rifle worth thousands of dollars.

If you do it, be aware that the value of the adjustment marks or clicks on the rear sight will change accordingly.
For example, if one click on the rear sight previously moved the point of impact one inch at 100 yards, shortening the sight radius by half would cause the point of impact to move 2 inches per click; etc.
You could calculate it out by percentage of alteration from the current length, etc.
You'll probably end up with "awkward" values if you need to know how much to move it during a match or something.

But if you're just plinking, trial-and-error will suffice without blowing a brain muscle.

How does sight radius alone affect point of impact? The only change I could see would be if the barrel was tapered and the actual height of one of the sights was changed.

 I never said it would.
Changing the sight radius won't change the point of impact per se, IF the sights are placed perfectly back into the original LINE of SIGHT, (they wont be, due to fitting discrepancies, or barrel taper, as you noted) and IF Barrel harmonics don't change by chopping it. (They will).

But the VALUE of the clicks on the rear sight WILL CERTAINLY change, because the angle between the line of sight and the line of bore has  been altered by shortening the sight radius. ( They aren't parallel to one another in the real world, nor should they be.)

Match rifles such as that are often used in such a manner that the rear sight is adjusted frequently for yardage changes, lighting factors and ammo variations from lot to lot, hence my warning re the value of the rear sight clicks.
( If we were discussing a scoped rifle, the point would be moot and my warning invalid, )
Make sense now?

He is correct, you should always think of the rifle sight and bore as the two long legs of a triangle.   A large chop off will change your sight line to bore line angle unless you're very lucky with a coincidence.  And that's with all things being equal, which they're not, like muzzle velocity and harmonics.

Thank you guys for the information.

The rifle is a single shot bolt action rifle I am just going to plink and have fun with at known distances, 25 or 50 yards.

All I am looking to do is retain the target sights and the way they act and how they are used for shooting, and create a more compact and easier handling rifle.