External Ballistics of cast bullets.

[braddock]

know if I have the right section but I have a problem with bullet drop.
I got into casting quite late, as I'm 78 years old so I need to get up to speed pdq if I'm going to get any results this side of the bar.
I expected some drop but when I load 165 grn flat nose in my mod 94 30/30 with a muzzle velocity of 1550 fps the point of impact is 8 to 10 inches below what speer factory loads with 150 grain flatnose ammo at 2280 fps does.
Is there an easy way of estimating this trajectory prior to going to the range and re-zeroing the rifle every time I change loads?
The problem is I have one of those williams peep sights and it's rapidly running out of elevation adjustment.

[nueces5]

you have two options
change the sights or increase the load
I'm used to the fall of my cast
in the mauser of engineers I put in 300 meters and there is a bulleye at 50 meters
Basically I ended up using two loads, for 600 meters and for 50 meters, and with that I already have enough to play with.

[braddock]

Wow, I didn't expect so much info so quickly, many thanks, guys.

[Bigslug]

The NOE Bullet Molds site lists an estimated ballistic coefficient at the bottom right hand corner of each of their bullet blueprints. Find the closest shape to your bullet and key those numbers into the online ballistic calculator of your choice (Federal has a good one).

[MUSTANG]

May be more than you want to wade in; but I use the Ballistic Calculator from this web site:

https://shooterscalculator.com/ballistic-trajectory-chart.php

Your results will depend on how appropriate/accurate the information is you input. I use this in Load development and also use it for printing out Drop Charts for saving in a binder for my various "Keeper Loads".

[414gates]

Keep in mind that the G1 BC number x 1000 means the bullet will travel roughly that far before losing half it's energy.

The flat nosed 150gr bullets have a stated G1 of 0.25, so for the sake of the exercise, say your 165gr cast bullet has that BC.

It means if your rifle starts out at 1500 fps, then at 250 yards the bullet is at 750 fps, compared to the Speer load where at 250 yards it's still 1140 fps.

This explains the big drop difference - caused by a significant overall reduction in speed for a bullet with a relatively low BC.

[charlie b]

What are you using the rifle for? Plinking? CASS? Hunting? If hunting, what ranges?

As stated above, the easiest solution to get close is to increase the vel of the cast load. You could probably get close to the 2280 of the factory load if you really wanted to and ballistics of the factory flat point and a cast flat point should be close. If hunting you might want to go this route.

If you just want something fun and cheap to shoot, then reduced loads are the way to go. Yes, you might have to change the front and/or rear sight to accommodate the 'rainbow' trajectory. I am sure you could find the right sight combination for your rifle.

[Hick]

Just to clarify what all the above posts are correctly hinting at-- the trajectory of a bullet does not depend so much on the weight, but rather the shape and how it is affected by wind resistance. The thing that determines this is called the "Ballistic Coefficient." So, for each of your bullets you need to find the Ballistic Coefficient (some mold manufacturers list that data). Once you know the ballistic coefficient for a bullet, most of the online calculators can give you a good prediction of the trajectory.

[braddock]

Charlieb, paper punching and, when my legs (and wife) allow it, hunting, though that really isn't much more than an annual event if I'm lucky as old age and prior lower limb injuries catch up on me.
I guess I suspected all of the reasoning, it just came as a shock to me just how much drop there is, certainly much more than my 22 LR.
I'm just getting all the ingredients together to start powder coating my boolits so I can up the velocity and thus minimise the issue.
Big problem is there aren't any registered 50 yard ranges near me to continue using low velocity rounds, so it's either 25 or 100 yards and up. 25 yards isn't too much of a challenge is it, even accounting for insipient cataracts.

[mnewcomb59]

Braddock it sounds like you are sighted in for 150 jacketed and you found your cast load with 1/3 the energy hits at a different spot. It sounds like you never zeroed the rifle after you changed ammo. Different loads hit at different points of impact. This is not an external ballistics problem, it is a rifle harmonics and recoil problem. Your factory load has much more recoil and the barrel rises after you pull the trigger and before the bullet leaves the barrel from the recoil forces. Your cast bullet load does not have as much recoil and your barrel basically stays on target from trigger pull until the bullet leaves the barrel.

It doesn't matter which rifle or handgun : when you dramatically change velocity and bullet weight your point of impact will change and you will need to re-zero the rifle. You are not seeing 10 inches of bullet drop at 100 yards from a 1550 fps load. You are seeing 10 inch different point of impact. 1550 fps will shoot flat to 100 yards when zeroed 1 inch high at 60 yards. 1550 fps will have 1 inch of drop at 100 yards when zeroed at 85 yards. 1550 fps will never have 10 inches of drop at 100 yards - that is just a bad rifle zero.

If you want to use two dramatically different loads you can come up with a cheat sheet to change your rear sight setting or write down how many clicks on your scope you need when switching back and forth between the different ammo. With my 357 lever actions a 125 gr at 1300 fps hits about 15 inches low and 4 inches left at 50 yards when zeroed for a 158 at 2000 fps. Nothing can be done about it. You can experiment with different bullet weights and velocities to find a plinking load that hits closer to your hunting load.

[charlie b]

Really low vel loads are a hoot at the range. Here are a bunch of lighter loads.

http://www.gmdr.com/lever/lowveldata.htm

As for range use, just load up the ammo and go shoot. Zero the rifle for whatever ammo you are using. Change the sight settings when you change ammo. I write done the sight setting on the ammo box lid so I can remember from one session to the next.

If you can't get the rear sight high enough you can use the old style of adjustment for fixed sights. Select a lower point on the front sight to align with the rear. It can be difficult this way, but, it works. If your eyes get bad you may need to go to glass sights. Red Dot is easiest, but, for a M94 you might want something 'older' looking, like a fixed low power scope.

[braddock]

I'm trying to make sense of why the groups are so low, with factory speer 150 grain and hornady 160 grn ftx the points of impacy were 6" and 4" below point of aim at 100 yards.
My williams rear sight is so far up it's in danger of falling out so I took a couple of images to share.




311476311477FWIW the barrel is 0.600" in diameter at the front sight, 0.746" in diameter at the rear sight, I'm trying to establish the mean hight of the front and rear sights so I can make some sense of it.
Looking at the second image, this is the setting that brings the groups of my 179 grn cast with 16 grains of 2400 up to the point of aim, if you look carefully at the inverted image (sorry) it's just possible to make out the stop screw (behind the white calibration mark) which will allow the peep to drop to the position for the factory hornady ammo.
The calculations I've made indicate that to shift the point of impact 4" at 100 yards I should move the rear, peep, sight 1 mm or 0.040" which actually worked, shifted the sight 1.5mm and the poi rose 6".
So my hornady 160 grn ftx print 2" high at 100 yards which should put the bullet in our small deer's kill zone out to about 170 yards given my group size of around 3".
Incidentally my magnetospeed sporter says these hornady don't make 2400 + fps, they averaged out about 2280 fps but it's a sod of a job to hang the sensor onto the barrel and mag tube securely so there might be a built in error there. I have to say though that the cast bullets made about 1560 fps average which is what was expected.
I'll do some development full loads with RL7, starting at 22 grns behind the 179grn cast which should make about 1800 fps, if successful I'll continue developing the load as my powder coating enterprise comes on line in a few weeks, reducing the risk of leading.
For the sake of argument, I'll also reload some speer 168 grain spbt and use the gun as a 2 shot using cfe223 which gives significantly lower pressure than, say, Varget.
Thanks for all your interest, it certainly helps my addled brain think....

[braddock]

Here's the images I tried to install in my post. I'm trying to demonstrate the hight of the sights above the bore center line and wondering if they are truly in line with the bore.


311502


311503

[Willie T]

Simplified answer: Dropping velocity by 730 fps is why you are shooting low.
Two remedies that are easy:
1- Gas check your cast and tip the powder can to load your cast close to factory velocity.
2-disregard remedy number two. I posted incorrect information. My apologies.

Changing loads requires you to sight your rifle in to the load you are shooting. Anemic plinker loads are fun but they are not going to shoot to the same point of impact as full power loads.
Willie

[dondiego]

Simplified answer: Dropping velocity by 730 fps is why you are shooting low.
Two remedies that are easy:
1- Gas check your cast and tip the powder can to load your cast close to factory velocity.
2- Install a taller front sight post to gain the needed elevation adjustment with your low velocity ammunition.

Changing loads requires you to sight your rifle in to the load you are shooting. Anemic plinker loads are fun but they are not going to shoot to the same point of impact as full power loads.
Willie

You aren't going to "gain needed elevation" by increasing your front sight height!

[Willie T]

You aren't going to "gain needed elevation" by increasing your front sight height!

Yeah, I screwed the pooch there. Will edit my reply accordingly. Drinking beer and watching college basketball don’t mix with posting on the internet. My apologies.
Willie

[Recycled bullet]

I think he must have meant to raise the rear sight to gain the needed elevation adjustment to zero the rifle

[Recycled bullet]

My low velocity plinkers shoot fourteen inches lower than full power loads at fifty yards in my 308 Winchester rifle.

[charlie b]

Yep, same for me.

Is there a way to get a new front sight that is lower, or file it down?

[35 Rem]

To me there is no problem. Since it's a 30-30 we are talking about you can load a cast bullet to practically full power as long as it's a gas check design. That way you give up nothing in either trajectory or range when shooting cast. That's why I shoot cast in rifles chambered for 30-30, 32 Special, 7.62x39 and 35 Remington. These cartridges all generate velocities compatible with cast bullets when shooting heavy for caliber weight bullets. In other words, cast hunting loads give up nothing compared to factory ammo.

[popper]

Slower bullets invariably hit lower. Cheap solution is to aim higher. Mark your target 6-8" above desired point, aim there and look at groups lower.

[dondiego]

Slower bullets invariably hit lower. Cheap solution is to aim higher. Mark your target 6-8" above desired point, aim there and look at groups lower.

I have heard of low velocity pistol rounds that impacted higher due to barrel hang time and recoil.........just saying.

[Pirate69]

I think the observed difference is a combination of both internal and external ballistics. Based on information provided in the initial post, I created two loads and ran the two loads through QuickLoad.

Cast Load: NOE TL310-165 RF, BC 0.242, 1550 FPS
Speer Load: Speer FN 2011, 150g, BC 0.255, 2280 FPS

I first looked at the total drop, due to gravity at 100 yards. The cast load was predicted to drop 8.1". The Speer load was predicted to drop 3.7". A difference of 4.4". The time to 100-yard target for Cast/Speer was 0.2108 seconds/0.1416 seconds. Cast drop differences for 125 yards and 150 yards were 7.1" and 10.6", respectively. Gravity alone does not account for the observed difference between the points of impact at 100 yards.

I think the remaining difference is the internal ballistics and barrel harmonics. When the initial "explosion" occurs in the chamber, a pressure pulse (wave) is generated that moves from the chamber to the muzzle and back through the steel barrel. The pulse moves at approximately 19,000 fps and probably moves up and down the barrel 5 or 6 times before the bullet exits the barrel. The pulse makes the barrel vibrate much like a tuning fork. It vibrates in both a vertical and horizontal direction. In essence, the muzzle moves in a very small circle with respect to the static bore centerline. All things equal, a bullet that exits the barrel when the bore is in the 12 o'clock position will hit higher than a bullet that exits in the 6 o'clock position. Same effect in the horizontal plane. Don't think OP indicated a difference in impacts right or left of the other load.

The pulse also sets up a vibration across the barrel as well. This results in the bore diameter actually expanding and contracting as the pulse traveling up and down the barrel. If the bullet exits the bore when the bore is expanded, there may be some unequal gas blow by which may generate some yaw as well. Best to exit the bore which contracted (accuracy node) to ensure best bullet fit to the bore.

I do not think the barrel is free floated. If so, then the wood contact can interfere with the normal barrel harmonics and clock exit positions can change from shot to shot.

In this case, I think the recommendation to sight the rifle in for each desired load and record the settings is the best solution. Gravity alone is giving about half the observed differences in POI.

Just my thoughts. I know this is a lot of "what ifs" but these could be contributing factors.

[Larry Gibson]

"Is there an easy way of estimating this trajectory prior to going to the range and re-zeroing the rifle every time I change loads?"

Not really, because you won't know what range the "new" loads are zeroed at.

Ballistic tables would tell you that IF you knew the zero range.

Selecting a bullet with a similar BC [doesn't have to be the same weight nor caliber, just a close BC] from the ballistic tables in the back of Lyman's Cast Bullet Handbook #3 may help you some.

[john.k]

Actually,there is an easy way......simply compare published drop figures for similar velocities and bullet shapes .........You might also note that 1500f/s is a problematic velocity ,as the bullet is affected by the turbulent flight zone around the "sound barrier" for much of its flight.Air drag is as much as twice what it is with a 2000f/sec.muzzle velocity

[Recycled bullet]

I have heard of low velocity pistol rounds that impacted higher due to barrel hang time and recoil.........just saying.I found this interesting correlation several years back between point of aim, and point of impact,

when tested under less than ideal conditions with my Smith and Wesson two and a quarter inch barrel fixed gutter trench sighted J frame

stainless steel magnum snub. Generally I found heavier bullets strike higher for a given distance and lighter bullets tended to strike lower all

other things being equal, trying to be as consistent as is reasonably possible.

It's just food for thought.

When tested in my right hand, fired offhand in single action at twenty yards these two loads both shoot to the exact same point:

1) old school graphite lubed 148 grain Remington hollow base wadcutter bullets seated flush with the case mouth and lightly crimped in r-p thirty eight brass over two grains of WW231.

2) 110 grain jacketed hollow points that I bought from everglades ammo company loaded over twenty two grains of H110 in star line 357 mag brass and heavily crimped.

Could those two loads almost make a display of what that revolver is ballistically capable of doing with the reloaders mind set??
[emoji848]

[popper]

Ballistic calculators don't take recoil or barrel harmonics into account. That is our job. I waded through the code of an on-lie calculator, interesting the approach used. There is one, forget which, that allows a comparison between a known load and an unknown, at the known zero.

[Larry Gibson]

The "known zero" is the problem. With out that drop tables won't give the OP any information because they too, depend on a "known zero".

[braddock]

Just a final(for me) post, basically got it sorted. I had a long and involved conversation with a well experienced armorer and he echoed all the points that were raised and one that was nearly raised in the 3rd paragraph of post #23, in that the lower velocity bullet spends more time travelling down the bore of the gun and, given the inherent problems with attachment points in mag tube lever action rifles, the harmonics significantly affect the POI downrange in addition (or sometimes in opposition) to the drop caused by gravity on the lower velocity projectile.
It made sense to me and helped with my shooting.
I've also found that instead of experimenting with several different loads and bullet weights I should concentrate on fine tuning and zeroing a specific boolit and I did and it has paid dividends both in POI and group size.
Many thanks for all the responses sharing your knowledge, I really appreciate it.
FWIW I stopped worrying about BC and adjusted the rifle by the target results - instant karma!

[Rich/WIS]

IIRC the Lyman #3 cast bullet book has ballistic tables in the back for their designs.

[charlie b]

FWIW, lever guns also can have problems shot from a rest. I think it was Paco who said to grip the fore end with your hand and then rest your hand on the bag. I found that helped my groups with a Win94.

[MUSTANG]

I am surprised no one else has cited it; but the Cast Boolits site has a thread where the Ballistic Coefficient's for a wide variety of Cast Boolits from different Mold Manufacturers is provided. There has to be at least 100 or more listed:

https://castboolits.gunloads.com/showthread.php?94638-Cast-Bullet-Ballistic-Coefficent-Table

In addition; for those using NOE Molds, their site has dimensional drawings for each (most?) of their Boolit Molds. These drawings include the Ballistic Coefficient for that particular Mold. This information can be found at:

https://noebulletmolds.com/site/bullet-dimensions2/308-2/

I personally appreciate the level of information and the design drawings that NOE provides us.

[Digital Dan]

Model 94 Trapper, 16" barrel, 50 yards w/Lyman 311041 BHN 10. Ballpark same velocity as Hornady 170 gr RN. Sights were not adjusted.

https://i.imgur.com/jmQScof.jpg

https://i.imgur.com/upvGZ9n.jpg

[mehavey]

At that range, we're looking at barrel dynamics (not BC).