Question regarding point of impact of heavier bullets

[Arkansas Paul]

So I bought a 310 grain mold for my .44 magnum and one of the statements in a thread about it was, "I hope your front sight is tall enough for that bullet."
I have done very little shooting with it, but the little bit I did, sure enough, it shoots about 6-8 inches higher than 245 grainers at 25 yards.
This is with a gas checked cast bullet.


However, with my .45 Colt it is a different story altogether.
I shoot a lot of 255 grain SWC bullets out of it at around 1,000 fps.
When I switch to 300 grain Hornady XTP bullets, loaded in front of a stiff charge of H110 or IMR4227, the point of impact is not 6-8 inches high like with the .44 mag. In fact, it is very close to the same.


What gives?
Is it because the .44 bullet is cast? Do they shoot that much different than jacketed?


Just trying to figure out why it is happening with one and not the other.

If it matters, the .44 mag is a 4 5/8" barrel and the .45 Colt is a 7 1/2".

[mdi]

Mostly it's the "barrel time" and recoil. Faster bullets are in the barrel for less time than slower bullets and the recoil is lifting the barrel. Heavier, slower bullets are in the barrel for a longer time and the barrel has risen due to recoil and shots go high. At least that's my logic...

[JoeJames]

Mostly it's the "barrel time" and recoil. Faster bullets are in the barrel for less time than slower bullets and the recoil is lifting the barrel. Heavier, slower bullets are in the barrel for a longer time and the barrel has risen due to recoil and shots go high. At least that's my logic...Yup, a/k/a Dwell time. Only solution other than a taller front sight is increased velocity, but that can sometimes be limiting after a certain point. But - I was shooting Speer .430" swaged 240 grain swc's on top of 6.5 grains of Unique. It shot way high - I could not crank the rear sight down far enough. I upped the charge to 6.8 grains of Unique and then it was point of aim at 25 yards.

[Arkansas Paul]

That makes sense.
I'm pushing the 300 grain .45s at full throttle "Ruger only" velocities.
The cast bullets out of the .44 mag, I'm pushing the 310 grain cast bullets at only around 1,000 fps.

Funny, it seems like those should be reversed. lol

[lar45]

Brownells has Ruger front sight blades
https://www.brownells.com/search/index.htm?k=ruger+blackhawk+front+sight+blade&ksubmit=y

Another option is 2 dogs has custom sight blades and complete front sights with the base and everything. They look great, I've bought several of the sight blades and 3 of the complete front sights for my BFR's. I'll see if I can find a pic of them.
I know he hangs out at http://singleactions.proboards.com/ you can probably contact him there.

http://www.lsstuff.com/pics/bfr/bfr-sights-01.jpg

http://www.lsstuff.com/pics/bfr/bfr-sights-02.jpg

Here's a pic of the finished, blued and serated BFR sights. The Ruger sights need to be fitted to your gun and you have to drill the hole for the roll pin.
http://www.lsstuff.com/pics/bfr/bfr-sights-03.jpg

[fredj338]

Different guns different results. In my 4 5/8" RBHSS, the 300gr print higher than 250gr, enough so that I had to fill off a bit of the frame under the rear to get the sight far enough down to get POA/POI @ 25y.
BTW the dwell time thing, uh no. Run a 250gr @ 1000fps & a 300gr at 100fps, same dwell time, the 300gr always prints higher in that gun. Run a 200gr @ the same vel & it shoots lower.

[DougGuy]

My 7 1/2" SBH shoots the heavies high just like yours does. I have one load that I use for hunting, and I don't shoot any other loads in this 44 besides the C 430-310-RF. Mine needed the rear sight blade filed completely flat with the sight base, a new notch filed in the center, and the sight base screwed down tight against the frame.

[Arkansas Paul]

I'm just wondering now how far down range point blank is going to be with it printing that high.
I may have to do some experimenting with that just to satisfy my curiosity.

[bmortell]

my SBH 44 hits the same as yours higher with 300gr, but my SRH hits bullseye with 240 and 300gr. so I don't know whats goin on

[JoeJames]

I'm just wondering now how far down range point blank is going to be with it printing that high.
I may have to do some experimenting with that just to satisfy my curiosity.If you get a chance, read Elmer Keith - Sixguns. He wrote about the phenomena of heavier slower boolits shooting high at close range, but eventually going to the same point of aim as lighter faster boolits. Something like that anyhow.

[The Dar]

I was wondering the same question but in reverse. I've been using up a batch of 240gn SWC purchased from the San Antonio gun show which I've been shooting over 20 years in my 6" S&W mod 29. I recently started loading a Lee 214gn SWC which I cast. The lighter bullets shoot 4 to 5 inches low. The time in the barrel makes perfect sense to me.

[Bookworm]

BTW the dwell time thing, uh no. Run a 250gr @ 1000fps & a 300gr at 100fps, same dwell time, the 300gr always prints higher in that gun. Run a 200gr @ the same vel & it shoots lower.

Sure, different weight boolits are running the same speed, once they get up to speed.

A heavier boolit takes longer to get moving to speed. It takes more to move 310gr than it takes to move 240gr.

That difference in time to get up to speed is the difference in dwell time.

[frkelly74]

Mostly it's the "barrel time" and recoil. Faster bullets are in the barrel for less time than slower bullets and the recoil is lifting the barrel. Heavier, slower bullets are in the barrel for a longer time and the barrel has risen due to recoil and shots go high. At least that's my logic...

It is logical, yes, it is also the physics of the action vs the reaction that Newton studied long ago.

[Arkansas Paul]

If it's dwell time, it seems odd that the longer barrel of the .45 Colt, does not produce this effect. The 300 grain bullets shoot about the same POI as the 240s.
It's the 4 5/8" barrel that it is so pronounced.
You'd think the 7 1/2" barrel would have more barrel for it to dwell in, for lack of a better way to phrase it.

I know every gun is an animal within itself though.

[lar45]

Both bullets shooting the same velocity...
The heavier bullet causes more recoil, the gun rocks in your hand, which will point the barrel higher when the bullet exits. The bullet hits higher on the target.

The lighter bullet causes less recoil, which will not push the barrel as high when the bullet exits. The bullet hits lower on the target.

A lighter gun has less mass, so it should recoil more printing the bullets higher on the target.

I have a 480 Bisley that was shooting way too high, so I ordered a taller sight blade from Brownells. I punched out the roll pin and found that they had drilled the hole right through the front edge of the sight blade. I sent it back to have them put on a new sight base with the hole drilled in the correct place and to put in a higher blade as long as they had it all apart. The sights were then very easy to adjust to get POA to POI, point of aim to point of impact.

hope this helps.

[Shuz]

About 14 years ago, I found that my Ruger KS45N would print 300+ g boolits 13" high at 25 yards with a light magnum load of 19.5g of WC820 and a Lee 310. (1207fps) I installed a taller front Patridge sight and that solved that issue.

[WheelgunConvert]

I just love the look of an octagonal barrel.

Thanks for the pictures