Load development for point of aim

awaveritt · October 8, 2009, 12:56 PM

I have shot a thousand or so 158gr. lead bullets over 3.5 gr. of Bullseye thru my S&W 638 and have become used to the point of aim relative to my sighting hold. Now I'm casting some 125 gr. RN and am wondering what kind of change in point of aim I can expect. I plan to also use 3.5 grs of Bullseye to start out, but will this raise or lower the expected point of aim? I'm assuming an increased charge will be needed to return to my original point of impact with the 125 grain bullets. Anyone already invented this wheel?

**Unclenick** · October 8, 2009, 01:43 PM

Handgun POI is pretty much governed by bullet weight. Charge difference has a kind of built-in compensation. A hotter charge recoils more, but gets the bullet clear of the barrel sooner, and the two factors tend to cancel out. Not perfectly, but that's the tendency. A lighter bullet, though, gets out faster with less recoil, so the muzzle just doesn't rise as much before it exits. The result is lower point of impact by a few inches at 25 yards. Exactly how much depends on the gun weight and barrel length and is best determined experimentally. It seems to me that at 25 yards my Dan Wesson had about a 6" increase in POI going from 110 grain to 158 grain bullets. I've forgotten if that was with its 6" or its 8" barrel?

snuffy · October 8, 2009, 01:57 PM

A S&W 638 doesn't have adjustable sights? I can see why you're concerned if you have fixed sights.

October 8, 2009, 12:56 PM	#1
awaveritt Senior Member Join Date: December 30, 2008 Location: Central Texas Posts: 259	Load development for point of aim I have shot a thousand or so 158gr. lead bullets over 3.5 gr. of Bullseye thru my S&W 638 and have become used to the point of aim relative to my sighting hold. Now I'm casting some 125 gr. RN and am wondering what kind of change in point of aim I can expect. I plan to also use 3.5 grs of Bullseye to start out, but will this raise or lower the expected point of aim? I'm assuming an increased charge will be needed to return to my original point of impact with the 125 grain bullets. Anyone already invented this wheel?

October 8, 2009, 01:43 PM	#2
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Handgun POI is pretty much governed by bullet weight. Charge difference has a kind of built-in compensation. A hotter charge recoils more, but gets the bullet clear of the barrel sooner, and the two factors tend to cancel out. Not perfectly, but that's the tendency. A lighter bullet, though, gets out faster with less recoil, so the muzzle just doesn't rise as much before it exits. The result is lower point of impact by a few inches at 25 yards. Exactly how much depends on the gun weight and barrel length and is best determined experimentally. It seems to me that at 25 yards my Dan Wesson had about a 6" increase in POI going from 110 grain to 158 grain bullets. I've forgotten if that was with its 6" or its 8" barrel? __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

October 8, 2009, 01:57 PM	#3
snuffy Senior Member Join Date: May 20, 2001 Location: Oshkosh wi. Posts: 3,055	A S&W 638 doesn't have adjustable sights? I can see why you're concerned if you have fixed sights. __________________ The more people I meet, the more I love my dog They're going to get their butts kicked over there this election. How come people can't spell and use words correctly?