Reloading for a double rifle

My old boss used to work for Holland and Holland and has recently acquired one of their fine double rifles in 303 British, I think it's a royal model but not sure, in any case its probably worth several times more than my car. We're going to develop a load for it, it's over 100 years old but at some point the sights/barrels were regulated for modern ammo. Does anyone know how velocity, seating depth, etc might effect the poi for each barrel? Or is it a matter of fine tuning different variables until we get lucky and both barrels shoot the same at 100m or whatever the regulated distance is?

If you are lucky their may be a record of the regulated load. Bullet weights and velocities that differ from that load will have both barrels having a different point of impact possibly totally unrelated to where the sights point. If you just want to shoot it then fine they are close quarters guns anyhow so a 8 inch spread at 100 yards might not be a problem.
Personally I would be reluctant to use modern factory ammunition and try loads that duplicate the mk 6 ie 210 or 215 grain bullets at around 2000 fps.

Marty Henry is spot on, but if the rifle has been re-regulated for modern ammo it might pay to try some factory 180 grain loads just to see how they shoot first. That will show immediately where you are at. You should still be able still find some old but clean Mk VI 215 grain ammo to try as well, but clean the rifle with hot water afterwards because of the corrosive primers.

what is stamped on barrels....alot of older classic rifles had a load stamped into them....guess it was what sights were regulated for...
being single shot you will be able to allow cases to grow to chamber size and just leave them alone with just a wee squeaze and neck trim...should be great for case life.
SxS 303brit with 180-220grn round nose would be absolute hammer of thor and joy to use as bush rifle.... Ive often contemplated bakail single in 7.62x39mm getting a rechamber to the bigger round....

and more importantly...WHERE ARE THE PHOTOS???? how can we drool over keyboard without them???

I’ll probably have the info at home, forget BP in these rifles, there are conversion light loads, I currently am using 2208 in my 500 BP Express with no probs, my latte is getting cold!!

Yes BP is no great show in the .303 Brit, very useful still in some Bore Rifles & the dam 577/450, just a prick to clean up if you are only firing a couple of test shots, seems Ok if a big shoot em up session .

I was using 2208 in my .577 BPE Ex but in my 12bore I using Nitro loads as 160gr-170gr of Black has some boot & burns up a lot of powder/money fast .

You could always try Holland & Holland they keep very extensive records and are usually quite willing to help in parting with this info.

If you go to the enquiry page here https://www.hollandandholland.com/bespoke-gun-making and send them a nice letter with the serial number and a few stamps from the barrel etc you should get back a quite indepth reply with who the gun/rifle was made for and regulation sighted in distance etc.

Worth a try.

Yes BP is no great show in the .303 Brit, very useful still in some Bore Rifles & the dam 577/450, just a prick to clean up if you are only firing a couple of test shots, seems Ok if a big shoot em up session .

I was using 2208 in my .577 BPE Ex & in my 12Bore I use Nitro loads as 180gr-190gr of Black has some boot & burns up a lot of powder/money fast .

Went to edit post on checking loads & some how made new one ?

Attachment 153232
Shooting the British Double Rifle, author Graeme Wright

You need to be happy with the pressures for the rifle!!!!

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Originally Posted by Maca49

Attachment 153232
Shooting the British Double Rifle, author Graeme Wright

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Cheers, this rifle was actually one of the ones Graeme used to develop the loads in the book. I've looked at the ADI data and it looks like some of the above loads are producing 38000 psi or more, which is what my first batch of 180 grain Sierra SPs in front of 37 grains of 2208 should be doing (minimum load in the book), I'll try to get my hands on the rest of the documentation accompanying the rifle before anyone fires it.

Wood Leigh make a 215 grain pill in .312 cal just for your purpose. That, some 2209 and a chrono should have you there.

Ok just had the image from Wright’s book open. It’s all there.

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Originally Posted by tommygun

Cheers, this rifle was actually one of the ones Graeme used to develop the loads in the book. I've looked at the ADI data and it looks like some of the above loads are producing 38000 psi or more, which is what my first batch of 180 grain Sierra SPs in front of 37 grains of 2208 should be doing (minimum load in the book), I'll try to get my hands on the rest of the documentation accompanying the rifle before anyone fires it.

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Already building some provenance.