H4198 vs IMR4198 for 45-70 FTX 325 gr

[Franco]

Just some reloading info for those who load 45-70 using the Hornady FTX bullets. I shot my Marlin 1895 cowboy w/ 26" barrel today and wanted to relay my educational experience.

I loaded two boxes of 20 yesterday. One with H4198 and the other with IMR4198. Both used Hornady brass, CCI 200 primers and 47.5 gr of powder. I understand they are different powders but Hornady data shows only a 50 fps or so increase in MV using the IMR. I didn't measure velocity today but WOW what a difference in trajectory.

I was hitting just a hair low of center at 100yds using the H4198 loads, about 3 MOA (open sights leaning on my gear bag). Then, when I moved to the IMR4198 loads, I was shooting 8" high of center. Luckily, I put a large backing paper around my 11"x11" target so I could see it hitting a couple inches high of the target. I moved my rear sight down 2 notches (to the lowest setting) and am hitting dead on at 100yds with the IMR4198 in reasonably tight groups (for aging eyes and open sights resting on a gear bag....).

I will be loading with IMR4198 going forward, at least with FTX bullets.

 

[NCsmitty]

Thanks for the update on your loads, Franco.

I'm not surprised that you got those results, as IMR4198 is a bit faster burning than H4198. At the same charge weight, IMR4198 is probably producing more pressure and a higher velocity compared to H4198. It would be interesting to see the actual difference over a chronograph.



NCsmitty

 

[Franco]

I will check the velocity next time I go out, when it's warmer than 11 F w/ 20 mph winds.... The Hornady data suggest only a 50 fps difference but I would be surprised if that's correct given an 8" difference in 100yd trajectory.

 

[ArchAngelCD]

I'm not surprised that you got those results, as IMR4198 is a bit faster burning than H4198. At the same charge weight, IMR4198 is probably producing more pressure and a higher velocity compared to H4198. It would be interesting to see the actual difference over a chronograph.

Exactly my thoughts. With the same charge weight the Hodgdon powder will generate more pressure & velocity than the IMR powder. That would explain the different POI.

 

[Franco]

I think you have that backwards? The IMR powder generated higher velocities and flatter trajectory with the same charge weight as the Hodgdon.

 

[Asherdan]

Franco, that 47.5 load looks like it's 0.4g short of max for both IMR & H4198, according to the Hornady data I've attached. Did ya' work up to that at all or just jump right in?

From my experience...The IMR load hitting higher suggests that it was the slower moving load, it was in the barrel longer and the muzzle rise due to recoil caused the higher POI. That's something I always have to remember when switching from my 1400 fps practice loads to hunting loads going 1750 - 1950 fps.

From my reminder notes:

Unique -> H4198 = adjust scope 4" DOWN
H4198 -> Unique = adjust scope 4" UP

 

[Franco]

I just jumped right in to the 47.5gr load. I did know that it's just shy of the max.

Your could be right about the cause of the trajectory change but I know that I'm hitting very good groups with IMR so I will stick with that. I'll need to start charting this myself.

 

[ArchAngelCD]

Sorry, you're right Franco, I did flip the 2 powders...
(and I was even agreeing with the quote above what I wrote)