Developing a .404 Jeff Cast Bullet plinking / practice load

[Ray B]

One option to obtain .424" cast bullets is to get cast bullets for the .44/40 which measure .427" and run them through a sizer die squeeze down the .003".

 

[3nyala]

Why not Hawk bullets, from 300 to 400 tn, $110 vs $68 for the bengals. Nice thing is they are soft copper and lead and would extrude well at reduced velocity here in this thread.
And a 404J is not one of the cheapest rifles to build or feed, so why not Hawks?

I searched for 404 bullets and only got main stream premium bullets. Hawk never came up. Also Bengal does not seem to have a way of ordering. I may have used an old link or something. I’ d go with bengals for practice for sure.

But does anyone think this will work?

 

[farmer_john]

Why? They’d be more expensive than the coated gas-checked HC .424” boolits that Bengal Bullets makes now.

.404 (.424

tiiarmory.com

Whats the difference in the hardness options?

 

[3nyala]

One option to obtain .424" cast bullets is to get cast bullets for the .44/40 which measure .427" and run them through a sizer die squeeze down the .003".

They seem to only be 200 grainers though. Want closer to 400.

 

[Jack Stevens]

Whats the difference in the hardness options?

Due to velocity differences, i.e., how fast do you intend to send them?

There’s Rigby velocity, original.404J velocity, and downloaded “plinking” velocity (typically using 5744 or similar).

.404 (.424

bengalbullets.com

 

[3nyala]

From Bengal Website,

Bullets will be unavailable for order for the time-being. Current turnaround for standing bullet orders is approximately 6 weeks.​

Not sure what that means.

 

[Jack Stevens]

From Bengal Website,

Bullets will be unavailable for order for the time-being. Current turnaround for standing bullet orders is approximately 6 weeks.​

Not sure what that means.

What it likely means is that BB went from a full-time gig to a part-time, "made-to-order" business model. I'm sure these guys have other jobs. The custom hard-cast boolit business is fickle, with times where orders come slamming in, and then dry spells where orders only trickle in.

When I ordered my first batch of the .404J 390grn/.424" boolits, they listed a lot of their other boolits as in stock and didn't have the above "Unavailable" banner on the site. Emails were answered right away. That banner was up in June 2025 when I last ordered more .404s and some of their .358 slugs.

The guy I've dealt with is "James." Nice guy. I emailed him to place the order, and when it was ready to ship he contacted me, and I sent him a check.

Email: kbt452@gmail.com (although the name in the header of James' reply email was "Keith Tow"). There's also: bengalbullets@gmail.com

Regardless, their boolits are well made and, I think, reasonably priced. I would do business with them again. If anyone's seriously interested, shoot James an email and see what their current status and wait time is for ordering the 390grn .404 slugs.

 

[farmer_john]

What it likely means is that BB went from a full-time gig to a part-time, "made-to-order" business model. I'm sure these guys have other jobs. The custom hard-cast boolit business is fickle, with times where orders come slamming in, and then dry spells where orders only trickle in.

When I ordered my first batch of the .404J 390grn/.424" boolits, they listed a lot of their other boolits as in stock and didn't have the above "Unavailable" banner on the site. Emails were answered right away. That banner was up in June 2025 when I last ordered more .404s and some of their .358 slugs.

The guy I've dealt with is "James." Nice guy. I emailed him to place the order, and when it was ready to ship he contacted me, and I sent him a check.

Email: kbt452@gmail.com (although the name in the header of James' reply email was "Keith Tow"). There's also: bengalbullets@gmail.com

Regardless, their boolits are well made and, I think, reasonably priced. I would do business with them again. If anyone's seriously interested, shoot James an email and see what their current status and wait time is for ordering the 390grn .404 slugs.

View attachment 754258

What hardness do you recomend to practice with and what velocity range for the hardness levels?

 

[tward1604]

Do yall ever have any issues getting these to chamber in your rifles? I have a batch and none of them will chamber in my rifle. The bullets I have from Bengal measure .425

 

[Ray B]

Do yall ever have any issues getting these to chamber in your rifles? I have a batch and none of them will chamber in my rifle. The bullets I have from Bengal measure .425

i'm guessing that the part that doesn't fit is the cartridge neck? If the bullets being .001" too thick and your rifle has a minimum diameter one solution would be to turn the case necks, but the cases would be strictly for those larger bullets.

 

[Grumpy gumpy]

Do yall ever have any issues getting these to chamber in your rifles? I have a batch and none of them will chamber in my rifle. The bullets I have from Bengal measure .425

Do you have a bullet sizer with a 424/423 die? I run my cast through a 424 die when I lube and fit the gas check
Gumpy

 

[Jack Stevens]

What hardness do you recommend to practice with and what velocity range for the hardness levels?

I went with the 15BHN. My practice loads are 2050fps-ish.

 

[Jack Stevens]

Do yall ever have any issues getting these to chamber in your rifles? I have a batch and none of them will chamber in my rifle. The bullets I have from Bengal measure .425

They chambered in mine at .424", and I played around with COAL, but felt the coating was still a bit too thick. So I got a Lee bullet sizer die and knocked them down to .423." Worked fine and didn't affect the GC.

 

[tward1604]

They chambered in mine at .424", and I played around with COAL, but felt the coating was still a bit too thick. So I got a Lee bullet sizer die and knocked them down to .423." Worked fine and didn't affect the GC.

Thanks @Grumpy gumpy and & @Jack Stevens, I was thinking about getting a Lee sizer and this is good confirmation to just do it.

404 Brass is too expensive for me to turn the necks just for lead practice loads unfortunately.

 

[Jack Stevens]

Thanks @Grumpy gumpy and & @Jack Stevens, I was thinking about getting a Lee sizer and this is good confirmation to just do it.
404 Brass is too expensive for me to turn the necks just for lead practice loads unfortunately.

I also bought a .422 sizer for ‘just in case’ but haven’t needed to use it.

Both the .422 and .423 Lee sizers were custom made by Lee, as they didn’t stock that size. Lee did get them made and shipped pretty quickly as I recall.

 

[cmk]

Could we make jackets bullets for 404?

I recently acquired a 404 Brno 602 and have been looking for practice rounds. I tried some 416 bullets but they keyhole and cannot for the life of me find any moulds to cast bullets.

So here is an idea I came up with to make jacketed 404 bullets with about the same amount of work as casting bullets. This is untested at the moment.

A .40 cal SW handgun case is .423 in diameter. My initial idea was to just press in two 180gr bullets into the spend 40SW case (no powder of course) and load it as a bullet. I ran the idea through Gemini AI as I am not an engineer and after many iterations we can up with this.

TITLE: MANUFACTURING 400-GRAIN .423 PRACTICE PROJECTILES (CASE-SWAGED COMPOSITE)
DOMAIN: INTERNAL BALLISTICS & MATERIALS SCIENCE
CALIBER: .404 JEFFERY (.423" GROOVE / .412" LAND)

1. MATERIAL PROPERTIES & PHASE TRANSFORMATION
To convert 70/30 Cartridge Brass (C26000) into a functional jacket, the material must be moved from its "work-hardened" state to a "recrystallized" state via thermal annealing.

- PRE-ANNEAL YIELD STRENGTH: ~65,000 PSI (Hazardous for rifling engraving)
- POST-ANNEAL YIELD STRENGTH: ~15,000 - 18,000 PSI (Safe/Ductile)
- VICKERS HARDNESS (HV): Drops from ~160 to ~65.
- ELONGATION %: Increases from <10% to ~55% (Allows for "cold flow" during sizing).

2. CORE PHYSICS & HYDROSTATIC "SQUISH"
Using Soft Lead (BHN 5) creates a hydraulic-style bond during acceleration.

- ACCELERATION (2,150 FPS / 24" BORE): ~35,889 Gs (Peak 60,000+ Gs).
- INTERNAL INERTIAL PRESSURE (Pi): ~13,380 PSI.
- OBTURATION MECHANICS: Pi (13.3k PSI) pushes outward against the Annealed Jacket Yield (15k-18k PSI), forcing the .011" brass walls to seal the .423" grooves perfectly.

3. MANUFACTURING WORKFLOW (THE "RIVET-BOND" METHOD)
Step A: DECAP & DRILL. Remove primer. Enlarge flash hole to 1/8" (0.125").
Step B: ANNEAL. Heat to dull red (~700°F). Air cool to "Dead Soft."
Step C: CAST. Pour molten soft lead into the case on a flat steel plate.
- LEAD VOLUME REQ: 0.115 cubic inches for 332 grains of lead.
- PROTRUSION: ~0.26" of lead will extend beyond the .75" brass case.
Step D: SWAGE/BUMP. Use a press to collapse the 2% thermal shrinkage gap and shape the nose (ogive).
Step E: FINAL SIZE. Push through a .422"-.423" die.
- TENSION LOCK: Brass elastic recovery (spring-back) clamps onto the lead core.
- WORK HARDENING: Sizing introduces ~2-3% Cold Work; minimal effect on safety.

4. NUMERICAL COMPARISON: DIY VS. COMMERCIAL JACKET

| Feature | DIY .40 S&W Jacket | Standard Rifle Jacket |
|------------------------|------------------------|-----------------------|
| Alloy | 70/30 Cartridge Brass | 95/5 Gilding Metal |
| Jacket Thickness | 0.011" - 0.012" | 0.025" - 0.035" |
| Yield Strength (Annealed)| ~18,000 PSI | ~12,000 PSI |
| Core Retention | Mechanical "Rivet" | Chemical/Flux Bond |
| Sectional Density (SD) | 0.319 (400gr / .423) | 0.319 |

5. STABILITY & FLIGHT BALLISTICS
- TWIST REQ: 1:14 (Standard for .404 Jeffery).
- GYROSCOPIC STABILITY (Sg): ~2.0 (Statically Stable).
- CENTER OF GRAVITY (CG): Rear-biased due to brass web and lead-filled primer pocket.
- CENTER OF PRESSURE (CP): Forward-biased on blunt practice profiles.
- SPIN RATE: ~110,571 RPM at 2,150 FPS.

6. SAFETY LIMITS
- VELOCITY CAP: 2,200 FPS (To prevent aerodynamic slumping of the exposed soft lead nose).
- DIE MATCH: Use a .423" push-through die to ensure groove-to-groove engagement and prevent gas cutting (leakage).

I know AI can hallucinate so I want to make sure this idea is not an hallucination too... and safe. It would be only for reduce loads for practicing.
If there are any engineers that can weigh in on this idea I am happy to have your comments.
Thanks

It can be done, but you won't be able to fit 2 × 180gn bullets in 40 S&W case. The second (top) bullet will not be seated very deep, and may have trouble staying put.

This is a 10mm Auto case, which is a bit longer, with a 180gn bullet squished into it, nose down.

After seating the first bullet, the case bulged out to approx .435 (yes, I did lean on the handle a bit). Running it through a couple of resizing steps has it down to .423.

Adding a second 180gn bullet would give about 430gn final weight.

 

[Huvius]

It can be done, but you won't be able to fit 2 × 180gn bullets in 40 S&W case. The second (top) bullet will not be seated very deep, and may have trouble staying put.

This is a 10mm Auto case, which is a bit longer, with a 180gn bullet squished into it, nose down.

View attachment 755826View attachment 755827
After seating the first bullet, the case bulged out to approx .435 (yes, I did lean on the handle a bit). Running it through a couple of resizing steps has it down to .423.

Adding a second 180gn bullet would give about 430gn final weight.

Round the nose, or even push them into a regular FLS die to use the shoulder to form a bit of an ogive on the bullet.
I’ve done this for my 10.75X68 which is the same dia as the 404. Works great but is a little time consuming.
Any cast .416 bullet can be paper patched to .424” quite easily but that too takes a little dedication to get right.

 

[Huvius]

For my bullets made from 40S&W brass, I was lucky enough to have a paper patch bullet mold that the brass fits so can pour the core rather than push it in. You could flux the inside of the brass to get more of a “bonded” bullet but I don’t think that’s needed.
Another cheap option is to take an aluminum Lee base pour mold of a smaller bullet and drill it out to hold the 40S&W / 10mm brass to pour the core as I have done.

 

[farmer_john]

For my bullets made from 40S&W brass, I was lucky enough to have a paper patch bullet mold that the brass fits so can pour the core rather than push it in. You could flux the inside of the brass to get more of a “bonded” bullet but I don’t think that’s needed.
Another cheap option is to take an aluminum Lee base pour mold of a smaller bullet and drill it out to hold the 40S&W / 10mm brass to pour the core as I have done.

View attachment 755869



View attachment 755870



View attachment 755871

How do those fly?

 

[Huvius]

How do those fly?

They shoot as well as I can and are superb on water jugs!
That’s my son when he was 16yo shooting his TypeA Mauser 10.75X68.