Help with rear sight on a 10" octagon .357 barrel

[billythekid55]

I have a 10" octagon barrel in .357 magnum.  The barrel shoots 6 inches high at 30 - 75 feet.  I took off the sights and installed a red dot on a Weaver mount.  I can get the barrel to shoot nice groups at 30 and 50 feet.  I prefer a sight to the red dot, but did this to confirm the barrel shoots fine.  I contacted Thompson Center and they said it needed the medium sight and to send the barrel to them.  I sent the barrel in and got it back with a new sight.  It still shoots 6 inches high.  I only tried 30 feet, but it should shoot fine at that distance.  Does anyone have a 10 inch octagon barrel that they could either measure the sight, or take a picture, or tell me how far the bottom notch of the rear sight is above the barrel?  I have contacted Thompson Center again, but they will not receive the email until Monday, and I would like to have some more information for them when they respond.

Anyone have any other ideas why this barrel would shoot high.  Everything I have read leads me to believe the rear sight is too high.

Thanks much in advance,
Bill Morgan

[P.A. Myers]

A site I have that came off an octagon measures .540 above the barrel. This is to the top of the sight blade at full depression.
Octagon barrels have a fixed front site and the bulls have a pinned blade so you could go taller. I have switched most of my barrels to the older style 'saddel sights' . Many have required a taller front site blade. A steady hand with a Dremel could easily cut the rear notch deeper and adjust up if needed. The standard types of rear sites are plentiful and cheap so you can expiriment a bit.

I have a 44mag 9inch that used to be a super14. It shoots flat with lead bullets and high with jacketed. I have other barrels [and guns] that dont do that. Seems odd.

I hope this may help, good luck.

[billythekid55]

I have a 44mag 9inch that used to be a super14. It shoots flat with lead bullets and high with jacketed. I have other barrels [and guns] that dont do that. Seems odd.

I hope this may help, good luck.

Thanks for the tip with the lead/jacketed bullets.  Looks like I have an excuse to go shoot again

Thanks, bill

[MePlat]

Don't worry about the rear the front is pinned in.  Get a piece of steel the same thicness as the original blade and cut and shape it with a grinder and file,  make it more than high enough,   pin it in and file it to get the correct height with the rear a few clicks off bottom  You can even shape the top of the sight the way you want as a bonus..  Cold blue it and it works like a charm.  I know I have done it a few times.
As simple as that is I would leave the rear alone.

[P.A. Myers]

Dear Bill,

The front sight on an octagon barrel is NOT pinned. It is soldered to the barrel. Bull [round] barrels have
sites mounted by two screws and the blade is pinned. Replacing or altering the rear blade is the best option.

[billythekid55]

I spoke with a gunsmith friend of mine this weekend while we were teaching a Hunter Education class and mentioned the problem of the barrel shooting high.  His thought was that the barrel will shoot high with .38 special ammo and shoot on target with .357 ammo.  His reason was the .38 has less powder, does not move as fast and stays in the barrel longer.  This "barrel time" lets the recoil act on the round a fraction of a second longer.  The impact the "extended barrel time" has causes the .38 to shoot high.  I had taken the sight off and installed a red dot.  At 40-50 feet, the .357 did indeed shoot about 6" lower.  I was surprised by this, but his explanation made sense.  I have replaced the iron sights and will make another trip to the range to see if the .357 does shoot on target using the iron sights.  If it does not, I will either get another barrel or use the red dot.

The example the gunsmith used was "shooting .44 special in a .44 magnum."  The .44 magnum was sighted in at 75 feet.  When he shot the .44 special at 50 feet, the gun shot 12 inches high.

Stay tuned, I will let everyone know what happens.

thanks for all the info and posts
Bill