Odd findings with zero 125 JSP today

[steel1212]

I was trying to work up a nice load for 125gr zero JSP and settled on 4.0 TG to start with just to see where I was at and would go from there. Here is the history

Springfield 1911 9mm factory barrel

4.0 TG

125gr zero JSP

1.150 OAL

WSP

Win brass

Now the PF came out to around 137 which I thought was a little steep considering only 4.0 of TG but it came out around the same out of my eagle as well. The odd thing was on the springfield I had to crank up my rear site like 2.5 complete turns of the dial up at 15 yards just to get it to hit where I wanted. I was shooting 147 grainers with 3.3 TG before. I would have thought the 125 grainers would be flater not have more drop? I didn't have enough rounds to run through my eagle for accuracy testing as well to see if it was just the springer or the load. I didn't have any tumble but I know with the 147s I had to bump up from 3.1 E3 to 3.3 to gain some velocity to make them stop tumbling, would that be an option here?

[wide45]

It is not drop.

Heavier bullets often print higher because the gun recoils more while they are still in the barrel.

[steel1212]

I never thought of it like that but the 147s have less felt recoil than the 125s thats for sure.

[LPatterson]

If you had to raise the sight 2 & 1/2 turns to get the bullet up where you wanted then it would seem to me it is shooting flatter because it was lower. Might want to try it at 25-50 yards for POI.

[steel1212]

Bring the rear up seems like to me that the other round was shooting flatter and I have to lob this one in more. I was at 15 yards but I'll try at 25 as well.

After thinking about it I see what your saying though. I'll try it at 25 yards.

Edited November 10, 2007 by steel1212

[Allgoodhits]

Bring the rear up seems like to me that the other round was shooting flatter and I have to lob this one in more. I was at 15 yards but I'll try at 25 as well.

After thinking about it I see what your saying though. I'll try it at 25 yards.

At the distance (15yds) you are testing, neither bullet you mention is dropping, "relative" to the sights. Keep in mind the bore is below the line of sight, 1/2" or more if iron sights and as much as 1 1/2" to 2 1/2" or more if scoped. At close distances you need to get the bullet to come up from the "bore line" to the "sight line". The point(s) where the bullet intersects the line of sight is the zero. Actually, given a far enough distance, the zero will occur twice. Once as the bullet rises to meet the line of sight, and once again when the bullet drops back down to the line of site.

The point at which the bullet is at it's highest trajectory above the line of sight is the "mid-range" trajectory usually represent as inches. True "flatness" of a bullet/cartridge is the bullet with the lower mid-range trajectory. Flatness when referring to felt recoil is not the same thing.

I have seen many people sight-in a scoped handgun at 25 feet or closer, only to be amazed when it shoots a foot or more high at 25 yards, and depending on ballistics of the bullet, it could be two feet high at 50yards! Yet, if sighted at 50 yds, it may be an inch or so high at 25 yds and an inch or so low at 10 yds! It has to do with the bullet intersecting with the line of sight on the way up and on the way down. Your zero should be for the longest likely shot you may have to take, unless you have the ability to change sight settings. Also, your zero should be under the conditions you need it to be zeroed.

In other words, from sandbags at 25 yds shooting as carefully and slowly as you want, is likely going to print very low when you have to shoot 6 shots in less than 2 seconds at any distance closer, simply because as you press the trigger at that rate, and without the support of the sandbags, then you are likely to pull the muzzle down slightly during shots, or the muzzle drops below the line of sight when the slide returns and you shoot the next shot before it has recovered and settled back exactly. Firearm design, cartridge, compensator and springs and shooter trigger control skill will minimize some of this, but it is present to some degree for all of us.

Regarding the turn and half turns on the elevation: First, most "clicks" are 1/4 to 1/2 inch at 50 yards. I think most thread pitch is such that about 25-30 clicks to a revolution. Given 1/2 inch click moving POI 1/2" at 50yds then at 10 yds each click is only about 1/10". At close distances, say 10-20 yds it takes a lot of clicks to move POI.

Second, the higher impact is not the heavier bullet, but the slower bullet. Heavier usually denotes slower since we chase a power factor. All guns with the grip below the line of the bore will have muzzle rise when fired. The bullet leaves the barrel as the muzzle is rising. A slower moving bullet is in the barrel for a longer time, and the barrel has risen more over time, thus the heavier bullet in some cases will print higher than the faster (lighter) moving bullet. Of course this print higher vs print lower will reverse at some greater distance depending on the mid-range trajectory and or external ballistics of the projectile.

Hope this helps!

Martin