Tony, I was at the range today for 2nd trial with the Hollis, and one of the loads was your suggestion. I have some .411 Hornday 300 spire points, which I tried with 64 grains rl 15. They printed right above the sights, 1.8 inches apart. I think your rule is gonna work with this gun. I only loaded 2, just to get started. They crossed, so do you suggest I reduce the charge slightly?

I also had 400 gr woodliegh's at 2.8 inches for 4 and a 5744 plinker, 3 shots at 1.3 inches. I'll need to corral Rusty and Mark into a chrony session to take the next step, but I'm having a good start. Bob

Bob
Sounds like your new double is going to be a shooter.
Here is what I would do.
I would load 4 rounds with 62 grains of RL 15,
4 rounds with 63 grains and 4 grains of 64 grains, all with the 300 grain bullet.
Shoot them all at 50 yards making note of the right and left bbl hits [as you well know].
I would let the bbl cool completely between each 4 shot group.
By shooting these 3 different powder charges you should see a trend. Either they will hit closer together or farther apart OR they may stay the same. If All if those loads cross, then I would start at 65 grains and go up, watching for pressure signs and see how the trend develops as you increase the powder charge.
Those 300 grain Hornadays should make great deer and pig hunting loads as wess as good practice loads.
Whar are you using for a filler, foam or poly, and if poly how much?

Sounds like your double shoots as good as it looks.

Tony, I'm using 3 grains of dacron. It's a pretty compact plug that comes just to the base of the neck. I'm getting a little primer cratering, but cases fall out on their own. No cratering on the low pressure xmp5744 loads. How do you interpret the primer signs in a double? Bob

Bob
I assume you are using Federal 215 primers.
Look at the firing pin openings in the breech face of your double. If they are fairly large you might get some primer extrusion into the holes. This is not the same as the primer showing a severe flatening, which in a double could mean headspace is off.

Or if your firing pins are pointy or large and flat they can drag on the primer as the rifle is opened.

How exactly do the primers look.
Also If you shoot both bbls does the rifle break open smoothly and do the cases fall out?

Tony, the primers are not flattening at all. JJ just rejointed so this gun is tight as a vault. The primers have a tiny rim or 'pucker' around the indendation. It opens smoothly and the cases fall right out. I am waiting on custom dies as JJ measured and found the chambers slightly oversized. I am just barely sizing enough to have the gun close on the cases so I work them as little as possible. I think I should size just a little more as it's just barely closing and locking up.
Do you think I should use just a bit less dacron? 3 grains is a pretty tight plug, but not coming in to the case neck. Bob
Bob

I would not worry about the primer pucker.
My 450/400 3 1/4" is a 60 grain Cordite gun. I have mostly shot IMR 4831 in it mut preliminary testrws indicate 71 to 72 grains of RL 15 will be about right for it. So you 64 grain load should not be too hot.
I would not reduce the amount of poly. In fact the poly should be compressed between the bullet and the powder.
Take a fired unsized case, put powder in it, put in your poly and insert a bullet. See if the poly os compressed as the bullet reaches seating depth. If not increase the poly.

Also for a Nirto for Black load start with 44 grains of IMR 4198, 12 grains of poly, and a 300 grain Hornady SP. Velocity around 1700 fps. Work up [watching for pressure signs] until they hit with the sights at 50 yards.

I'm gonna need some convincing to try anything other than 5744 since I'm getting 1.3 inch groups at 50 with 35 grains. It's amazing it's that accurate with the powder sloshing around like that. I just need to try it with the 200 yard leaf to see if it will be on at 50.

Great idea on the poly. I'll give it a try with a fired case. Thanks, Bob
Bob