A nice long range rifle with a sad life.

[madsenshooter]

I have never had to use a magnum primer. It is not a .50 BMG powder and would be very dangerous to use it as such.
Any load over 75 grains in my magnum rifles really changes how it burns.
But in cases from .223 to .300 Win Mag, the powder has worked very well for me. It is close to IMR-4350, just slightly slower, Not 7828 slow.
In cases up to .30-06 and 7.62x54R, a load up to the shoulder of the case is just about right. You can go more but it is really not needed. Just never tightly compress the powder. It will spike like mad if too compressed.
I have many,many loads that work well.

You must have the faster lot. This slow lot only goes good with a booster that I put in the middle of the charge of 7383. I've been using it in my K31 more than my Krags. There were three loadings used in the spotter rifle, thus the three lots. The slower stuff was for the tracer round that had a flashtube, plus a non-standard (hotter) 50BMG primer. I haven't worked with any of the faster lots. Thing is, the nitroguanidine coating needs to explode first. That explosion consumes all the oxygen, then the remaining nitrocellulose burns without a flame making it flashless.

[Rapidrob]

Sorry to hear you have to use an igniter charge, but with powders such as 5744 as the initiator , you'd be fine.you'd only need to use 3-6 grains. A so called "duplex load"
I had to do that using the surplus .50 BMG powders.

[madsenshooter]

I use a slightly faster powder. Big flakes, 10B101 (surplus Vihtavuori powder for 50BMG plastic training ammo). The flakes pretty much stay in place in the middle of the big logs of 7383. Very little to no compression, but a caseful with the bullet weights I've so far worked with. The loads I've worked up are very accurate. Sorta odd to be able to grab a case as soon as it comes out of the rifle and not get burned by it. It is a real pain to weigh out three charges per case though!

[Rapidrob]

An update from my post 6 years ago!
It turns out the rifles original bolt had seen a better life. The locking lug was peened a little and it did not help the excessive chambers length. ( .0250 ). I bought a new bolt body from Grampa's Parts and the bolt is now a nice tight fit.
Over the decades I've tried the Dental floss and the O-ring trick but all they do is blow the shoulder out thinning the brass at the web. Never got more than two shots out of a case. Now with the new bolt I decided to try something a little different. If I can't blow the shoulder out, why not form the shoulder further out? It can be done in several ways. Here is what I just did and it worked so well I could not be happier.
I have on hand hundreds of once fired POF .410 brass shotgun shells. These are .303 Britt that have never had the shoulders and mouth formed into the brass. ( that is how the CORDITE was loaded originally for the .303 ball ammo.)
I annealed the mouth of the brass cases and started to form the neck and shoulder in my sizing die. Once I could close the bolt on the newly sized case with resistance at the 2:00 position, I knew I was golden. The .410 cases formed into .30-40 do not need to be trimmed. I loaded up five 220 grain rounds and fired them into my bullet trap. BINGO! perfectly formed .30-40 cases that fit my rifle like a glove. Neck size only from now on.
I fired the rifle 25 times in my clubs match this past Saturday and Won the Off-Hand 200 meter match! Target was NRA steel silhouette chickens. This rifle will shoot.
The match in March will be firing 20 rounds at a man size AR550 steel torso with electronic flash to score hits set to 500 meters. I'm hoping the rifle will hold it's own.
This rifle has been a safe queen since I bought it in 1975. First there was the mercury primer destroyed bore. Then the problem of the OEM barrel replacement having a long chamber and a loose bolt locking lug of the rifles bolt.
You can do the same resizing of a .303 Britt casing as well. It will be a little short for .30-40 but should not hurt your rifles throat.
By re-sizing the brass .410 shotgun shells I have been able to make:
6.5 Dutch
.30-40 Krag
and of course .303 Britt.
All needed the shoulder to be further out to save the brass from case head separation. Yes, the brass is Berdan primed.
I just threw the fired cases into the wet tumbler and not one case shows any signs of stretching or cracking.
Here are the shells:
L to R- .410 POF annealed, formed case by die set back and fired in chamber with full load, original Winchester new casing.

Arrow pointing to where case head separation would happen if round fired again.

Formed and fired case on left, new Winchester on right. ( fired case to have mouth trimmed up.)

POF .410 case used to make all three calibers.

Primers needed.

6.5 Dutch made from .410 brass shells.

.303 Britt with shoulder out .020. This worked out great!

[madsenshooter]

With rim turned down to .485" a better fitting 6.5 Japanese can be made from .303, 30-40, and mostly likely your 410 shells too. I use .303 mostly, but have some I made from 30-40. I do the sizing before turning the rim down and opening up a .41 magnum shellholder a bit allows me to reload the semi-rimmed case.

[Rapidrob]

With many of the 6.5 Jap rifles having a "loose" chamber causing case stretching at the web, do the turned down .303 brass hold up better?