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Shooting High

1815 Views 6 Replies 5 Participants Last post by  James Gates
I have the rear sight on my 45LC Blackhawk turned down all the way, and am still hitting 4" high at 15 yards and off the paper at 25yds.  I know getting a taller front sight is probably the best answer, but I want to understand how varying the load can change the point of impact.

The load I am using is a Hornady 300gr XTP/Mag on top of 20.5gr of 2400.  I still have some room to go up on the charge before I get into max-load territory, at least with this gun.

What I want to know is:

1)  Will the point of impact go up or down as the velocity increases?

2)  Will the point of impact go up or down if I drop down to the 250gr XTP?

Thanks for your help.

(Edited by Husker at 2:42 pm on Sep. 6, 2001)
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Husker -

In my limited experience, I've learned that heavy bullets and or slower velocities will print high.  You'll need to increase velocity to bring those 300 grainers down.  Switching to a 250 gr. XTP without changing the powder weight thrown will do the same thing.

You probably have more far more reloading experience than I do but I believe pushing a 300 gr. jacketed bullet faster by using more than 20.5 gr. #2400 is dangerous.  Linebaugh and another source name (I can't find at the moment) list a 300 gr. lead slug, using 19 grs. #2400, at 29,400 CUP and 31,700 CUP.   Pressures are bound to be higher, by who knows how much, using a jacket bullet of the same weight.

Be careful!!
Been there - done that!

My "200th year" .45 Blackhawk will just barely get the rear sight low enough for 300 grain bullets.

Might switch to WW296 or H110, as you can run a little faster which will help.

I also filed a little on the uderside of the rear sight assembly (out of the gun of course) and gained a little more adjustment there.

My next step would have been to file down the top of the rear sight blade, but didn't need to.

It does make a huge difference how you hold the gun... tighter grip on the gun helps, as does shooting with a very soft rest under the gun.

Even adding a steel ejector housing could put some more weight up front, but then you put more stress on the screw holding it.
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Thanks for your reply.  Heavier bullets move point of impact up.  Lighter bullets moves it down.  Slower moves it up, faster moves it down.  Hopefully I can remember that.

I appreciate your concern with the pressure of this load.  I have the same concerns.  I started this load work up with 17.0 gr of 2400 using WLP primers, and increased it 0.5 gr at a time.  With 2400, the signs I look for are flattened primers and sticky extraction.  I also pay attention to the degree of dirtyness.  2400 has a reputation for being dirty, but I have found that it gets progressively cleaner as you close in on the max load.  So far with this load workup I still have normal looking primers and loose brass.  I did stop at 20.5, even though I feel I could go further, because I felt like I was getting close and wanted to get a better feel for how well the gun likes this load.

I probably should use the chrono for each charge as I work up, but mine only works on cloudy days, or early in the morning when I am shooting in the shade.  I've been so excited with this gun that I've been doing the load workup after work in the late afternoon & evening.  Hopefully I can get the chrono out this weekend and see what this load is running.  Maybe I'll be surprised, but I'm guessing 1350 or less.
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You might try switching to hardcast bullets, velocities will increase and bullet impact will drop.  I found that with Hornady 300 grain XTP's, the point of impact was much higher than with Beartooth 300 grain LFNDCGGC bullets.  The veleocites averaged over 150 fps faster with the hardcast bullets and the groups were tighter.  This was out of a S&W performance center M-629.

Thanks for your reply.  I do plan to develop a 300gr cast load for this gun as well.  I started with the jacketed because I am still breaking in this barrel.  When I get to the cast, I expect to tune the load to the same point of impact as the jacketed.


I was able to get this load over the chrono this weekend.  Average velocity is 1175 fps.  Based on that, and the absence of pressure signs, I don't think I have a dangerous load here.  

I do agree with the post that I can go faster with H110/Win296.  However, those powders work best when loaded to near max.  Max load is not my desire with this gun, thus my use of 2400.  Still, every powder has its "max load", and I feel that I am close enough to that to stop at 20.5gr.

To make a long story short, I called Ruger today and they confirmed that a taller front sight is available for this gun.  It is on its way to me at no charge.  
Chuck.....These are good answers as to what is happening and this is why....Bullet impact with hanguns varies with the weight of the bullet, velocity of the bullet, and weight of the hangun. All of these collectively, or by themselves can change the bullet impact. A handgun, due to its weight relationship to the bullet, begins to rotate in one's hand as the bullet accelerates down the barrel. If the velocity stays the same, the heavier the bullet, the more the rotationup, thus causing the bullet to impact higher. If the bullet weight remains the same and the velocity is reduced, the barrel time is increased(more time for the handgun to rotate) and the bullet will impact high. Normally, as you increase weight, velocity goes down....which compounds both of the above. One really sees this problem worse in the lightweight "snubbies"!
The gun factories have to set the sights adjustment to cover the most popular load weights/velocity. In some shooting circles, like ours,tend to used the heavier weight bullets. This compounds the problem. As you have been told, by switching to hard cast vs jacketed bullets of the same weight and powder charge...the hard cast is likely to impact lower. This is caused by the fact the hard cast has less friction, therefore less barrel time, therefore less barrel rotation, therefore a lower bullet impact. There comes a point( as you mentioned) that one cannot increase velocity with a given bullet weight due to running into excessive preasure.
What is the solution?....what you have been told...use a lighter bullet with a higher velocity (reducing the barrel time/barrel rotation) or installing a higher front sight to compensate for the increased barrel rotation with heavier bullets.
Best Regards, James
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