45-70 SUBS - 405gr LFP/Titegroup

[mobo215]

Hodgdon RLDC has a subsonic load listed for 45-70:

13.0gr Titegroup
410 HDY SUB-X
COAL: 2.547"
MV: 1005 FPS
27,900 PSI

I don't have the 410gr bullets, so I tried a small batch of ACME 405 LFP over 13.0gr Titegroup. I seated them a bit deeper to crimp to the cannelure. Velocities verified with a Garmin Xero C1:

Henry X 45-70, 20 shots:

• AVG Kinetic Energy: 1242.3 FT-LBS
• AVG MV: 1175.5 FPS
• EX SPREAD: 18.0 FPS
• STD DEV: 4.8 FPS
• MIN VEL: 1165.6
• MAX VEL: 1183.6

First, these SD and XS numbers are pretty good! Unfortunately, these were supersonic and three of the 20 shots hit the paper sideways. Even if they came in under the sonic barrier, I wouldn't want a baffle strike on my Obsidian 45. I'm wondering if I can trust any subsonic load that uses this 405gr LFP bullet to stabilize. I'd like to work up a load to launch 300gr Hornady Interlocks at subsonic velocities, using Titegroup. I can't find any data that even puts me in the ballpark, but I'm guessing 8 or 9 grains of Titegroup will get close.

Anybody try something like this? I'm looking for the lowest velocity possible that will stabilize reliably.

 

[hlee]

Start here for stability estimates…

Twist Rate Stability Calculator

Our newly updated Twist Rate Stability Calculator not only tells you what your SG is, but it also lets you know if you are reaching your optimized BC.

bergerbullets.com

Or here

Bullet Gyroscopic Stability Calculator

Calculate the Gyroscopic stability of a bullet with the Miller approximation.

bisonballistics.com

Or, put “ballistic stability calculator” into your search engine of choice.

 

[mobo215]

Start here for stability estimates…

Twist Rate Stability Calculator

Our newly updated Twist Rate Stability Calculator not only tells you what your SG is, but it also lets you know if you are reaching your optimized BC.

bergerbullets.com

Or here

Bullet Gyroscopic Stability Calculator

Calculate the Gyroscopic stability of a bullet with the Miller approximation.

bisonballistics.com

Or, put “ballistic stability calculator” into your search engine of choice.

The Berger site only goes up to .375, so I'm using the other site. Something doesn't compute. The 405 LFP I was using would be *over-stabilized*, even down to 850 FPS:

What am I missing here? Why did I get 3 keyhole shots?

 

[hlee]

The Berger site only goes up to .375, so I'm using the other site. Something doesn't compute. The 405 LFP I was using would be *over-stabilized*, even down to 850 FPS:

View attachment 8492104

What am I missing here? Why did I get 3 keyhole shots?

I’m not 100% confident in the Bison ballistics as it seems to be calculating Sg from supersonic velocities and extrapolating to subsonic.

It may be informative to put some reasonable values into the Berger calculator, and then check the Bison calculator against that.

 

[hlee]

That said, I was keyholing 22 cal bullets from a 6.5 twist 22 arc barrel, once the velocity got “too high” in my test ladder.

 

[mobo215]

I’m not 100% confident in the Bison ballistics as it seems to be calculating Sg from supersonic velocities and extrapolating to subsonic.

It may be informative to put some reasonable values into the Berger calculator, and then check the Bison calculator against that.

I did notice that despite entering 850fps as the velocity, the chart starts at 2000fps. Not sure what to make of that.

 

[redbullitt]

For subsonic 4570 the best thing you can do is load a big bullet if your rifle can do it, a 600ish grain postel etc gives me the best luck. 4570 is a big case... too big for good subs really. The best fix ive found is making your own big cast bullets to eat up the case space. Also can get rifle set up for cut down 4570 cases... lol but that's a rabbit hole.

If the acme cast bullets are not playing nice with your barrel they can do all kinds of crazy things on their way to target. Keyholes can happen very easily.

Commercial cast bullets tend to be of very hard alloys that play havok on some types of rifling, they may not obturate to the barrel well in low pressure loads, and often they simply are not fat enough. Excess pressure for the bullet base can easily make keyholes too. Even the bullet lube they used may not do well at low velocities or vice versa.

All this can easily cause barrel leading and distort the bullet to make it do crazy things in flight you don't normally see in jacketed bullets.

Another thing to consider... your cases may need cast bullet prep! Generally brass sized for jacket bullets will swage cast bullets down too small for your barrel, resulting in poor shooting ammo. Good cast bullets in 4570 are often .459 or bigger depending on what your rifle can chamber. Thiccc is good if it can chamber. Noe and Lyman make great tools to prep your cases for cast bullets to work well.

For powders... Trail boss tin star and unique have been the easiest to work with here, though very hard to find lately. Titegroup may be a little fast/harsh for a plain base cast bullet, causing your keyholes.

I'm not sure what your twist is, but my Marlin shoots slow 405 cast bullets very well. I'd be surprised if yours wont since that is sorta THE 4570 bullet.

 

[redbullitt]

For subsonic 4570 the best thing you can do is load a big bullet if your rifle can do it, a 600ish grain postel etc gives me the best luck. 4570 is a big case... too big for good subs really. The best fix ive found is making your own big cast bullets to eat up the case space. Also can get rifle set up for cut down 4570 cases... lol but that's a rabbit hole.

If the acme cast bullets are not playing nice with your barrel they can do all kinds of crazy things on their way to target. Keyholes can happen very easily.

Commercial cast bullets tend to be of very hard alloys that play havok on some types of rifling, they may not obturate to the barrel well in low pressure loads, and often they simply are not fat enough. Excess pressure for the bullet base can easily make keyholes too. Even the bullet lube they used may not do well at low velocities or vice versa.

All this can easily cause barrel leading and distort the bullet to make it do crazy things in flight you don't normally see in jacketed bullets.

Another thing to consider... your cases may need cast bullet prep! Generally brass sized for jacket bullets will swage cast bullets down too small for your barrel, resulting in poor shooting ammo. Good cast bullets in 4570 are often .459 or bigger depending on what your rifle can chamber. Thiccc is good if it can chamber. Noe and Lyman make great tools to prep your cases for cast bullets to work well.

For powders... Trail boss tin star and unique have been the easiest to work with here, though very hard to find lately. Titegroup may be a little fast/harsh for a plain base cast bullet, causing your keyholes.

I'm not sure what your twist is, but my Marlin shoots slow 405 cast bullet very well. I'd be surprised if yours wont since that is sorta THE 4570 bullet. Also you are not shooting them very slow to where I'd think twist will be an issue unless henry really messed up on specs for that barrel.

Also worth mentioning that, unless I missed it, you'll want to use coated cast bullets in the suppressor. They make a mess in there otherwise, and a huge pain if the can cannot be taken apart.

 

[wvfarrier]

I had the best results with 500+ grain projectiles for sub loads. At one point I was loading 600 grain hard cast lead (i forget which NOE mold) at 950fps. They were absolute murder on deer. Sounded like a sledge hammer hitting a side of beef. Basically like shooting them with a 12g slug.

 

[mobo215]

For subsonic 4570 the best thing you can do is load a big bullet if your rifle can do it, a 600ish grain postel etc gives me the best luck. 4570 is a big case... too big for good subs really. The best fix ive found is making your own big cast bullets to eat up the case space. Also can get rifle set up for cut down 4570 cases... lol but that's a rabbit hole.

If the acme cast bullets are not playing nice with your barrel they can do all kinds of crazy things on their way to target. Keyholes can happen very easily.

Commercial cast bullets tend to be of very hard alloys that play havok on some types of rifling, they may not obturate to the barrel well in low pressure loads, and often they simply are not fat enough. Excess pressure for the bullet base can easily make keyholes too. Even the bullet lube they used may not do well at low velocities or vice versa.

All this can easily cause barrel leading and distort the bullet to make it do crazy things in flight you don't normally see in jacketed bullets.

Another thing to consider... your cases may need cast bullet prep! Generally brass sized for jacket bullets will swage cast bullets down too small for your barrel, resulting in poor shooting ammo. Good cast bullets in 4570 are often .459 or bigger depending on what your rifle can chamber. Thiccc is good if it can chamber. Noe and Lyman make great tools to prep your cases for cast bullets to work well.

For powders... Trail boss tin star and unique have been the easiest to work with here, though very hard to find lately. Titegroup may be a little fast/harsh for a plain base cast bullet, causing your keyholes.

I'm not sure what your twist is, but my Marlin shoots slow 405 cast bullet very well. I'd be surprised if yours wont since that is sorta THE 4570 bullet. Also you are not shooting them very slow to where I'd think twist will be an issue unless henry really messed up on specs for that barrel.

Also worth mentioning that, unless I missed it, you'll want to use coated cast bullets in the suppressor. They make a mess in there otherwise, and a huge pain if the can cannot be taken apart.

The ACME 405 LFP's I'm using are coated. I measured a few of them and the diameter is exactly .458". I was expecting them to be .459", but they were not.

I think you may be on to something. I was using load data for the 410gr SUB-X bullet, which is jacketed. The listed velocity was 1005fps with 13.0gr of Titegroup. I think that the lead bullet was almost 200fps faster because it's 0.001" smaller in diameter than is typical for lead bullets, and because lead swages into the rifling with less pressure than jacketed bullets do.

17 out of 20 shots made perfectly clean holes in the target, while 3 keyholed. You're probably right that something is deforming the bullet base. On the other hand, since velocities were very consistent, I can only assume pressures are consistent as well. Titegroup really does a nice job keeping velocities in a tight band in the large cases.

410gr SUB-X bullets are over $1/bullet. I'd really like that make this work with less expensive lead bullets in that weight class or cheaper jacketed bullets in the neighborhood of 300gr, such as the Hornady Interlock HP.

 

[redbullitt]

Cast usually goes a good bit faster in same loading since it moves through the barrel much easier vs copper jacketed.

You should be able to get cast 405 or heavier, if not those to shoot. Those bullets at .458 are smaller diameter than I've shot in any of mine successfully and that's definitely the direction id be looking first.

Any leading in bore?

Perhaps try another cast bullet. Some places will let you pick diameter. Generally need to be .001 or .002 over bore at least. Bigger is good too if throat allows it and you can keep your brass from swaging them down.

Cast is the best way to shoot 4570 unless you've got deep pockets lol. Just takes a little experimenting to get it right, especially when using less ideal commercial cast.