300 Blackout Trajectory VS Subsonic 45-70 Trajectory

[375rifleman]

I was just inquiring about the differences between the trajectory/ballistics of the 300 Blackout VS the trajectory/ballistics of a subsonic 45-70 ? Since there are already rifle scopes calibrated for the 300 Blackout trajectory. Thanks in advance for any and all thoughts, opinions, or answers.

Regards,
375rifleman

 

[MudRunner2005]

Even with supersonics, neither will have good ballistics beyond 400 yards. They're just not designed to do so. Subsonically, I would give the advantage to the .300 BLK just because it was originally designed to be shot suppressed with subsonic ammo...The .45-70 wasn't. And when you don't get a very full case capacity (like subsonic .45-70) you can run into lots of problems like hang-fires, failure to fires, and powder ignition issues. Also, the .300 BLK uses around 10.5 grains of Hodgdon H110 magnum pistol powder to push a 215-220 grain bullet at around 1,050-1,060 from a 16" barrel. So it is VERY efficient, simply because it was designed to be a subsonic round with a big heavy projectile.

Given the fact that you can use ANY .308 caliber projectile for .300 BLK, and you can make your own brass from range pickup 5.56 brass for next to nothing, I would have to give a strong advantage to the .300 BLK. Not to mention that you can get some really cool factory rifles in .300 BLK already threaded and ready to be suppressed. You can also buy/build an AR upper for it, that only requires a barrel swap...Same bolt & same mags as 5.56/.223 Rem.

I built my .300 BLK back in 2015, and due to ammo prices and spotty paychecks (had some occupational issues from 2016-2018) I haven't even put more than a couple hundred rounds through it at most. But, now that I'm working at an ammo plant for a machinegun range, I get employee pricing on all of our remanufactured ammo. So, needless to say, I'll be stocking up about 100-200 rounds a paycheck.

If anyone is interested in some of our ammo, feel free to shoot me a PM, and I'll give you our info to contact us.

 

[375rifleman]

Thanks for your thoughts and response MudRunner2005. I do realize that the 300 Blackout was designed to be subsonic from the start, even considering that the 45-70 wasn't designed to be subsonic I have read/heard of many subsonic 45-70 loadings. I also realize that subsonic cartridges weren't meant for longer range shooting (past 400yrds-800yrds). The 45-70 carries a lot more energy/power down range than a subsonic 300 Blackout ever could just considering the increased bullet weights at similar velocities. Thanks in advance for any and all thoughts, opinions, or answers.

Regards,
375rifleman

 

[tim_w]

The one very nice thing about super heavy bullets going slow as in subsonic vs those supersonic is.....
Subsonic speeds have many fold less air resistance than supersonic flight. Now of course you will be lobbing artillery but lets just look at vel and energy bleed. Take the same 220 gr smk using its g7 BC.

Lets say it can get the job done with a vel from 1000 to 700 fps and has a mv of 1000 fps. What is its lethal range in yd when it hits 700 fps or a mere loss of 300 fps and 240 ftlb of energy from @ muzzle?

Hard to believe but 1500 yards!!!!

Now same bullet but with a say 2800 fps mv. It will have lost 300 fps in a mere 200 yds. Its 240 ftlbs in just 60 yds.


My point is if a subsonic bullet has the energy and vel to get the job done easily @ 100 yd with 200-300 fps cushion if you can adjust accurately for drop and wind it can still get it done at some hard to beleive ranges. The wind would be the hard part given flight time IMO.

Still it shows just how much more energy it takes to hold supersonic flight vs subsonic. Its why nonexpanding solids of old traveling subsonic could get it done at some crazy ranges if they could hit the targeted game.

 

[RT2506]

First off the original 45-70 was actually a sub sonic round. 500 grs of lead bullet pushed to just under 1200 fps with black powder. I shoot basically the same load in my Sharps 1874 copy. That big ol bullet don't have to be moving too fast to shoot clean through most any critter in North America out to 1000 yards and you can eat right up to the bullet hole as the old buff hunters used to say. You have to know exactly what the yardage is but with a good rifle and load these rifles are mind blowing accurate even at 1000 yards shooting with a Vernier open sight.

 

[tim_w]

Again thats cool part and fun shooting challenge of slow movin heavy lead. As long as its got enough left to punch a hole deep enough if you can hit right you can take it down.

 

[J E Custom]

Now there are some relativity good 45 cal bullets that have better ballistics than a brick that could be loaded to get better trajectories at subsonic speeds, so if you are interested in sub sonic loads for the 45/70, these should be looked at. (what comes to mind is the 250 grain .452 dia. flex tip used in the 450 bushmaster).

Just a thought

J E CUSTOM

 

[RT2506]

The US Army decided to go with the 45-70 after testing in which bullets fired from 1000 yards would penetrate 6 inch pine logs set at a 45* angle and then go over a foot down into the sand behind them. As for the trajectories of these big slow bullets it averages about a foot drop at 100 yards depending on bullet used. (At 1000 yards drop will be around 165 feet for 500/520 gr going just under 1200 fps). While shooting at 1000 yards at a 4 foot square piece of steel painted white from the prone using cross sticks with my Sharps I can shoot then lean over and look through my spotting scope and see the bullet come in at a pretty steep angle and hit the steel. It then takes about 2 to 3 seconds to hear the impact. I once shot a deer at 111 yards using Lymans 405 gr flat nose mold that drops a 418 gr slug out of my mix. Deer was facing me and I aimed at the white patch on it's chest. This slug was propelled by a weighed charge of 70 grs FFG compressed 1/10th inch with a over powder card cut from wax coated milk carton in a Winchester case fired by Fed. 215 primer which ran 1400 fps. By the time I fired and the bullet got there the deer started to put it's head down. Bullet struck just above the eye line in the center of the forehead. The pullet proceeded to make saw dust out of the spinal column down the neck then deflected and came out right behind the scapula of the left front shoulder. Then the bullet proceeded to angle down and hit the left back leg just above the knee joint and shot it completely off. Then the bullet hit the hard packed sand/dirt logging road and go underground running about 5 yards looking like a mole had gone down the road. The bullet then came out of the ground and about 1 yards away hit a 4 inch thick pine tree going through it and jerking a palm size piece off the back. I lost track of where the bullet went from there. A freight train don't have to be going too fast to run through a bunch of stuff.

 

[MudRunner2005]

I haven't shot a subsonic .45-70, especially at long distances, but common ballistics says that a subsonic anything (especially a .45-70 with 400-500 grain projectiles) shooting 1000 yards has got to be much more than 1 foot drop per 100 yards of distance. Even modern guns and cartridges pushing heavy bullet over 3,000 FPS drop more than 1 foot per 100 yards. After about 500, I could see it dropping multiple feet per 100 yards, multiplying the drop every hundred yards to the target.

 

[RT2506]

I meant to say about a foot drop at 100 yards for these bullets. I will try to correct it. I got a phone call in the middle of typing and had to come back and hurry the reply. Yes at 1000 yards the average 500/520 gr bullet starting out just under 1200 fps will drop about 165 feet at 1000 yards.

 

[tim_w]

I haven't shot a subsonic .45-70, especially at long distances, but common ballistics says that a subsonic anything (especially a .45-70 with 400-500 grain projectiles) shooting 1000 yards has got to be much more than 1 foot drop per 100 yards of distance. Even modern guns and cartridges pushing heavy bullet over 3,000 FPS drop more than 1 foot per 100 yards. After about 500, I could see it dropping multiple feet per 100 yards, multiplying the drop every hundred yards to the target.

Actually when you consider its lossing very little vel compared to supersonic flught there would not be a huge increase in drop rate compared to the same bullet supersonic. I know its a way high because compared to the 45/70 basically wadcutters, but the ratio would be close to the same. consider according to jbm traj cal it takes a 220 SMK 1500 yd to slow a mere 300 fps from a 1000 fps mv. What is that a loss average of 20-25fps/100yds? Looking at the chart vel as well as traj drop rate stays fairly consistent from zero to 1500; in the 20s moa rate.. The decay rate is just so minute comparitively becuase vel loss rate is so small. Its i weird looking at subsonic drops aftter years of long range drops working with supersonic only performance. Can you imagine your 300 BO rifle angle to hold for 309 MOA@1500 LOL. THats 4859" of drop with a 100 yd zero. Wow talk about lobbing one in there!!!

 

[RT2506]

I might add that that 500ish gr bullet that starts out just under 1200 fps is still going average 750 fps at 1000 yards with average 650 foot pounds of energy.

 

[tim_w]

See that is just unreal when you come from the supersonic world of lr rifle bullets. You would loose that much vel in 300 yd. So even pitching a bullet that is basically a flat ended cylinder with a terrible bc still gets you to 1k with more energy than many hunting handgun calibers. Sure its lost 1/3 compared to a super slick high g7 profile bc smk but still 1k. Thats crazy. That is why shooting those steel animalbtargets at 1k and further with these 150 + yr old cartidges and modern ones of the same type can be so much fun. I see it as the big brother to shooting 22lr at 200 300 yd . Itsball about getting the drop then reading that wind and the few seconds flight time. Great way to spend a good chunck of a weekend. IMHO.

 

[375rifleman]

What would be a good twist rate for shooting a subsonic 500 or so gr hardcast 45-70 bullets ? Would 1 in 20 even be ball park? Thanks in advance for any and all thoughts, opinions, or answers.

Regards,
375rifleman