Higher powered cartridge shooting low

[peterk123]

This has to do with my new beloved Marlin 1895 45-70. I got the fiber optic sight on the front and the skinner peep on the rear. Great set up. I no longer have sight issues. But, let's talk loads. At 50 yards the 24 grains of 2400 is right on. Nice grouping. As for the 45.5 grains of 3031, well it is a totally different story. At 50 they shoot low. I am shooting off of bags. I am taking the hit. And let me tell you, after ten rounds I am feeling it. I can't even say it is a consistent group, yet. I need a larger piece of paper to really figure where these things are going, but they are low. Any ideas on why they would shoot five inches lower than my soft rounds? I think I may back off on the load and see if it makes a difference. Pete

 

[slap shot]

More powder = faster projectile and a lower POI at close range as the bullet is getting there faster if that makes sense.

 

[mac1911]

Faster loads impact lower, its just how it is.

now why are they grouping poorly?

i assume nothing so you have to tell us what your shooting for , bullet,alloy, primers , ectect.
Shooting stout loads can really get to messing with good fundamentals. Its why target loads are often "dumbed" down.

 

[northny]

I’m a big fan of a lead sled when working up stout loads. It makes it more fun and keeps me from developing a flinch. Working off a bench with something that smacks you hard is no fun. I toughed it out for years till I got smart.

 

[peterk123]

Thanks guys. I thought it that a stronger load may hit low at short distance but I just could not picture it in my brain for some reason.

Some more info. 45.5 grains of IMR3031. 405 grain hitek coated bullet, 18 Brinell. Starline brass;new. Large rifle primer.

I have the front and rear of the rifle set on sand bags. Shooting at an eight inch round paper splatter target. The paper target is probably not helping because the misses are lost. I will use a large cardboard backing next time and more of the splatter targets so I can track the hits better.

Fun trying to figure it out. Not sure my shoulder agrees though

 

[mac1911]

Thanks guys. I thought it that a stronger load may hit low at short distance but I just could not picture it in my brain for some reason.

Some more info. 45.5 grains of IMR3031. 405 grain hitek coated bullet, 18 Brinell. Starline brass;new. Large rifle primer.

I have the front and rear of the rifle set on sand bags. Shooting at an eight inch round paper splatter target. The paper target is probably not helping because the misses are lost. I will use a large cardboard backing next time and more of the splatter targets so I can track the hits better.

Fun trying to figure it out. Not sure my shoulder agrees though

Large backer and use a aiming point just big enough you can see it clearly. Also a roll of this will give you a nice clean backer anytime you want

TRIMACO Easy Mask 2.9 ft. x 140 ft. Builder's Paper-35140 - The Home Depot

The Trimaco 2.9 ft x 140 ft. Brown Builder's Paper is an Economical Kraft construction paper which is large enough for several projects. Painter's Builder's Paper can be used as a paint drop cloth and

www.homedepot.com

 

[gerrycaruso]

Pete, the lower point of impact and the lousy groups are most likely 2 different issues. I'll explain at the range tomorrow.

 

[one-eyed Jack]

Draw the trajectory curve for both loads on a piece of graph paper and you'll see why. The faster load will be lower before it crosses the line of sight for the first time. Jack.

 

[straightshooterjake]

When people consider the point of impact for rounds with different ballistics, there are two important factors in play.

The first factor, which most people think of, is that the slower bullet will fall more due to greater time of travel. This is basic physics which says that all bullets begin falling at the same rate as soon as they leave the barrel. So this factor indicates that the faster bullet will hit higher because it has less travel time.

However, there is a second factor which has an opposite effect. The slower bullet stays in the barrel for a slightly longer time than the faster bullet, and the barrel begins to recoil as soon as the bullet starts to move. So the slower bullet leaves the barrel a little bit later in the recoil cycle, and is initially launched at a slightly higher angle. This factor predicts that the slower bullet will hit higher.

So how do these two factors combine in the real world? Here are some of my thoughts and observations.

1. If you want to know how the elevation will vary with different rounds, then shoot them. There are some guidelines about which of the factors will matter more, but shooting them on paper is always the final answer.
2. For pistols, usually the heavier bullet hits higher. For .38 special, 158gr rounds hit higher than 125gr rounds most of the time. The .45-70 rifle which is the focus of this thread has a pretty pistol like trajectory, so it is not surprising that the slower rounds hit higher.
3. If you hold the firearm tighter, will that control the recoil and make slower bullets hit lower? In my experience, no. We are only talking about a fraction of a degree of movement that happens in a millisecond. The movement during recoil turns out to be very consistent, regardless of hold.
4. For rounds with widely differing ballistics, you really can't guess the results. How will a 158gr .357 at 1400 fps compare to a 125 gr .38 special at 950 fps? Shoot them on paper if you want an accurate answer.
5. If the heavier bullet is launched at a higher angle, but also moving slower and falling more than a lighter bullet, then can their paths cross at some point? The answer is yes, but this mostly happens with rifle bullets at pretty long ranges. At practical distances for handguns or a brush rifle, the round which hits higher, will probably remain higher.

 

[mac1911]

Thanks guys. I thought it that a stronger load may hit low at short distance but I just could not picture it in my brain for some reason.

Some more info. 45.5 grains of IMR3031. 405 grain hitek coated bullet, 18 Brinell. Starline brass;new. Large rifle primer.

I have the front and rear of the rifle set on sand bags. Shooting at an eight inch round paper splatter target. The paper target is probably not helping because the misses are lost. I will use a large cardboard backing next time and more of the splatter targets so I can track the hits better.

Fun trying to figure it out. Not sure my shoulder agrees though

Still sick and board so I played around with the Quick loads- I used 45-70 govt, 26" barrel
The Lee cast bullet was the onl;y 405 grain one I could find in the data- If you want to me to enter your specific bullet data I need dia and length.
first up is with 2400

now with 45.5 of 3031--- considerably faster


My heaviest cast loads are 30 cal 200 grainers and I find even with gas checks and sized to fit my bore I do not get good accuracy above 1600 fps.
I dont know how well coated bullets seal the bore like a well fitted lubed cast bullet does ?

 

[peterk123]

Installed the longer studded rear peep today. The new peep solved my main issue. The first photo show the hit at 50 yards and 75 yards with my 405 grain behind 45.5 grains of 3031. The second photo includes the 100 yard shots. Except for one shot (call it operator error), everything goes higher the further out I go.

Then I shot the 24 grains of 2400 at 100 yards. Those were even higher; off the target.

So I am starting to figure this out, I think. Tell me if I am on the right track. This big hunk of lead arcs like a rainbow and I am not shooting at a distance great enough to experience the dropping of the trajectory. Whereas a fast flat shooting round may experience a drop at a 100 yards (in theory) because the barrel is basically aiming low, due to the fact that it was sighted for fifty. And at fifty yards, the fast flat shooting gun is shooting almost perfect straight at the target, so almost no arch. Am I close?





BTW, I am getting close to living with this type of accuracy at 100 with iron sights. Now I just need to find a powder and weight that will be consistent and not try to dislocate my shoulder. 24 grains of 2400 is a soft shooter but I do not like all the space in the case. It has to cause inconsistencies. @gerrycaruso , I am going to try the loads you sent me. That might be the ticket. Either 4895 or 3031 in the 31 grain range. Trapdoor load but should still fill the case fairly well.

 

[gerrycaruso]

If you're interested in a mild load that will take up a lot of space, try trailboss.

 

[mac1911]

Installed the longer studded rear peep today. The new peep solved my main issue. The first photo show the hit at 50 yards and 75 yards with my 405 grain behind 45.5 grains of 3031. The second photo includes the 100 yard shots. Except for one shot (call it operator error), everything goes higher the further out I go.

Then I shot the 24 grains of 2400 at 100 yards. Those were even higher; off the target.

So I am starting to figure this out, I think. Tell me if I am on the right track. This big hunk of lead arcs like a rainbow and I am not shooting at a distance great enough to experience the dropping of the trajectory. Whereas a fast flat shooting round may experience a drop at a 100 yards (in theory) because the barrel is basically aiming low, due to the fact that it was sighted for fifty. And at fifty yards, the fast flat shooting gun is shooting almost perfect straight at the target, so almost no arch. Am I close?

View attachment 337787

View attachment 337788

BTW, I am getting close to living with this type of accuracy at 100 with iron sights. Now I just need to find a powder and weight that will be consistent and not try to dislocate my shoulder. 24 grains of 2400 is a soft shooter but I do not like all the space in the case. It has to cause inconsistencies. @gerrycaruso , I am going to try the loads you sent me. That might be the ticket. Either 4895 or 3031 in the 31 grain range. Trapdoor load but should still fill the case fairly well.

Picture of your sights?

Your zero will dictate your “trajectory”
Along with load , sights ectect.
For example my 165 grain cast loads(aprox 1600fps or less) out of my 1903a3 needs the rear sight set to the 600 yard setting to get my point of aim point of impact . My 168 gn match loads at 2600 fps are point of aim point of impact at 200 on the 200 yard setting.

im not sure what they zeroed the old original 45-70 rifles for but Im sure its further out that you might think especially with no adjustable sights.

I'm not sure of the Ballistic Coefficient of the 405 grain bullet you have but I think .250 would be a ok guess. given your 3031 load spit out data of 1716 fps I will use that.
With a 100 yard zero= Point of aim point of impact your groups will shoot approx 1.5" high at 50 yards and drop off quickly at 100yds plus.

Same load with a 180 yard zero you could hit a game size broad side kill zone out to about 230 yards just holding center mass.
You might find one yardage point that the different loads will cross paths but thats not practical. This is why they have adjustable sights

Basically find a load you and your rifle like and zero it for the distance you shoot at most. Dependent on the adjustments of your sight type you can learn you "come ups" for your other distances.

 

[38ExtraSpecial]

Stole this pic from the google images.
Not sure the cartridge but you get the idea. If your rifle is zeros for 50 yard then it’s going to hit higher until you hit say 200 yard for this example.
if you zero for 25 yards then it’s even worse.
However if you take a 100 yard zero as seen last then you’re going to see a drop after that. More of a traditional thought process to how a bullet would act vs. your zero distance.

 

[peterk123]

Thanks guys. @Michael J. Spangler , your graph sums up what I was trying to articulate in my previous post. Wish I could tell you what I have it sighted in for. Lets call it fifty yards. At 100, my front sight covers the entire eight inch target so I am just "centered" on it. Figuring out this damn gun has been a lot of fun. Happy with the sights, now time for better load development.