I received delivery of early prod. sample 10mm 250 gr. FNGC
These are NOT for 10mm Auto by any stretch. However I plan to test them in the .401 GNR and my .38-40's, maybe the .401 Herters. At this weight the POI is often above the mechanical limits of sighting. One surely would not want to go any heavier as the bullets get too long. The .400 GNR would be absolutely perfect with a 250 gr. bullet like this. The .375 Win. had a 250 gr. factory loading and a .400 version would only be better.
For reference I have an old Lyman 240 gr. FNPB that was actually .406 cal. for use in the .401 WSL. It was a natural thing for guys wanting a heavier .40 cal. slug to size it .401 and run them. There were a few old .40 target long range numbers too.
I took a picture of the 180 gr. 10mm JHP (cannuler added) far left, the Lyman 240 gr., new 250 gr. FNGC bullets. Next is the .401 GNR and .38-40 with the 250 gr. bullets and far right is a .401 Herters with 180 gr. Remington bullet.
Not having any data I began with a reasonable charge 7.0 gr. of faster pistol powder to give an estimated 800-900 fps to start. I loaded both the .401 GNR and .38-40 Win. with the same charge to see what the case capacity and design would influence. This is before switching to 4227, 2400 or AA1680. No need to go too fast, I plan on around 1300 fps as a reasonable goal for a heavy loading. There is no reason the .400 GNR, on the blown straight .30-30 case, shouldn't rival the .444 Marlin performance with this bullet.
![[image]](images/uploaded/201801251921025a6a2e1ee4f10.jpg)
P.M. me at the yahoo "waterboyark" if you are interested in trying some too. It's sort of a custom order right now but possible.
One note about cast bullets and short neck ctgs.
The .401 GNR is a good example and the .429 GNR too. A short neck and struggle to retain as much neck tension as possible. Increasing bullet weight is also a recipe for bullet creep from the case with increased and duration of recoil. I'd not go past 300 gr. in the .429 GNR and have not tested this 250/10mm as of yet.
Look at the sides of that cast bullet comparing to the available internal case neck sidewall. What will touch the inside case neck when the bullet is seated to a particular depth? In my first earlier picture seated in the crimp groove, only the first band under, that narrow band is contacting the case neck to hold the bullet, and whatever crimp. By seating deeper I can shift the band lower, still in that neck area, and have that front band ahead of the crimp groove in the neck. That's two slim bands but an improvement in area and bullet grip with neck tension. The long necked antique .38-40 contacts all the bullet bands, those lube groves are just air to the neck tension but it has a bullet holding advantage.
Jacketed bullets have solid sides and are of no concern here. Lube groove laden cast slugs may need a little thinking of application or technique.
Look over the photo and added notes. Hopefully you can see what I mean. It's not the case's fault, maybe the bullet is not as good a fit as another design for this special application. Actually it was designed specifically as a high performance .38-40 bullet but with custom 10mm gas check bullets so limited it's worth a try for sure. I'll keep you posted.
![[image]](images/uploaded/201801252257545a6a60f279d11.jpg)