Basically my 75% rule is, take a bullet that weighs @75% of the standard weight bullet for your double, load the same powder charge, and it will hit to the sights, ie. the same place as the full power charge.

This 75% bullet load has less recoil, a little more velocity, and with the right construction the bullet is great for deer/pigs/black bear etc.

Make your elephant gun into a fun "pig" gun that kills better than the heavier constructed softs you normally use.

A buddy of mine has a Chapuis 470 double with a Swarovski 1-4 in claw mounts.

I finally got a chance to help him load some ammo today.

We had some 350gr Hawk Flat Point bullets with the .035jkt.

In other Chapuis 470's, 80gr of IMR 3031 has proven to be a perfect load.

So we loaded up 12 rounds with 75 grains of IMR 3031 and 5 grains of poly. [Always start low, and work up].

Why 3031, I have a lot of it on hand, and it has proven itself perfect for these 75% loads. In my 450 No2 I get the same results with IMR 3031, IMR 4831, and RL 15.
I use RL 15 for full power loads and 3031 for the 75% loads.
The first 2 rounds shot by me kneeling [no benches in the woods] were touching at 50 yards.

However they were about 6" high and 3" right.

When he shot the groups were in the same place.

No pressure signs, so we went back home and loaded 12 more woith 80gr of IMR 3031 and 5 grains of poly, and just for fun 2 rounds of 50gr of IMR 4198 with 15 grains of poly filler, this is a Nitro for Black equivelent load.

WE went back to the woods.

This time the 80gr load hit spot on with the ion sights [the irons are spot on with Federal Factory 500 grainers.

The scope hit an inch high and right but he had the scope sighted in with some 500gr lead loads from Superior.

At about 30 yards the Nitro for black loads also ht with the sights.The NfB loads have almost no recoil. They usually hot with the sights at 50 yards but hit a lower than the other loads at 100 because of their reduced velocity usually around 1700 to 1800fps.

These lighter loads are a great way to get more fun shooting and local hunting with your doubles.

So far my 75% rule has worked in several 450/400's and several rifles in the 450 to 475 class.

As have the Nitro for Black loads, for even less recoil.

You might want to give them a try.

Just remember the powder charge is the same, the BULLET weighs 75% of the regular/regulated load.

Works in 500 Nitro's as well with the
440gn Bullet.

And if you want an even cheaper option (less powder) give AA 5744 a try. If you dont know what load to start with in your double just drop Accurate Powders an email and they'll respond back pretty quick with some recomendations. Worked for me.

By N E 450 No2

quote:

So far my 75% rule has worked in several 450/400's and several rifles in the 450 to 475 class.

What 75% bullet did you like in the 450/400?

I've used Tony's rule with great success in my 450-400. If you have a .411 barrel, the 300 grain Hornady bullets for the 405 Win have worked perfectly. The 300 gr Spire points are perfectly regulated at 1 grain less rl 15 than the 400 Woodleighs. I also have a 5744 load for 300 gr Hornady flat points that are right on the money using the second leaf flipped up. Bob

I too am a convert to Tony's 75% rule. I use 300 grain Hawks in my 450/400 3 inch. I actually think they print better than the 400 grain Woodleighs I usually shoot.

Great pig/deer round! Pig Bomb!

Tony's 75% Rule works well for my 458wm double too. I am using 350gr Woodleighs but will switch to Hornadays when I run out of the Woodleighs.

JPK

People have used .410 or .411 Pistol bullets
in 450/400's.

From people who have been using DR's for years, when DR's weren't popular, using bullets designed for other calibres was one
of the only options available if you wanted to shoot them and the 75% rule was well known.

The other option was pulling old "Kynoch" ammo and replacing the Cordite.

210 gr 41 mag pistol bullets with 48 grs of 5744 (no filler required or recomended for this powder) in my 450/400 works really good on white tails and pigs.

Just finished exchanging emails with Hawk Bullets and he is going to make of run of some 215 grain bullets to test the 75% rule with my 9.3X74R Chapuis.

He gave me a choice of .030 and .035 jackets. I chose the .030 since I'll use them for deer and pigs.

The fellow at Hawk has always been great to work with on special orders.

I'll report what I find out.

With the 25% shorter bullet, do you use the same seating depth or the same cartridge length, or is there not enough difference to matter?

I'm curious as to why this recipe works. Using the same charge under a lighter bullet should create lower pressures with a bit higher velocity. Lower pressures imply a lower recoil and thus a lower rate of muzzle rise. This lower rate of rise combined with a shorter barrel time (ie., higher fps), should--it seems--cause the reduced load to shoot to a lower point of aim. Since the recipe works, what is really going on, then?

The topic is of interest to me, for while I don't own any doubles, I do like fixed sights on my singles.

It seems reasonable that the same powder charge using the same powder shouild give aqpproximately the same bullet muzzle energy, and how much difference is there in trajectory at 50 yards.

Seems like the unknown is 75% of what powder for them to regulate the same. Pick 3031 at random? It only works for 75% weight bullets and 3031? If the barrels still regulate, with the undefined slightly greater velocity, what are the corresponding bullet muzzlwe energies? Or is it considered irrelevant in this experiment?

ASDF, Will,

This works in many or most DR's, as reported hear. I've used 3031 but that is just because I haven't gotten around to trying it with powders I now use for full weight DG loads.

I seat my 350gr bullet to the cannelure which results in a shorter loaded length.

My 75% Rule loads do shoot a bit lower than my full weight loads. Somewhere between my fixed sight and my 100yds flip up. I just shoot with a bit of a proud bead and the fixed blade. Felt recoil isn't really significantly less.

I haven't chronoed the Rule loads because I wouldn't hunt DG with them. Velocity and energy aren't really relevant.

While there is much about THE regulating load for doubles, and this may be somewhat truer for Nitro cartridges since there often isn't much in bullet weight selection out there for some, it surely hasn't been the case for my rifle. I've found that changing powders can significantly vary what velocity shoots to regulation even with the same bullet.

JPK

The reason I am using 3031 for my reduced weight bullet loads is that I have a lot of it on hand.

I have tested my 450 No2, with full weight bullets with IMR 3031, IMR 4831, and RL 15.

After finding the load that regulated the 480 grainers, I shot the same powder charge with the 350gr Hornady RN's.
They regulated perfectly.

I found that I prefered RL 15 with the full weight bullets, but still use IMR 3031, with the lighter bullets because I have a lot of it.

I find the recoil of the "75%" loads to ne a little less that the full power/weight loads.

For even more recoil reduction, try some Nitro for Black power level loads.

For instance in my 450 No2

300gr HP 60gr of IMR 3031, 1750fps.

300gr HP 52gr of IMR 4198, 1878 fps.

400gr Cast 50gr of IMR 4198, 1822fps.

With IMR 4198 I use 15 [fifteen] grains of poly.

These loads are in the 45/70 power range and very plesant to shoot.

In a 450/400 double try a 300gr bullet with 40 to 44 grains of IMR 4198 for around 1700fps. Again you must use a filler.

I'm just trying to understand what is going on here. Your 75% Rule just says that if one uses the same powder charge on lighter than nominal bullets that the rifle was regulated with the barrels will still be regulated, right? But not neccesarily the same POI?

And apprently using a different powder doesn't make any difference in regulation? At the reduced powder loads the bullets have a greatly reduced velocity but still maintain regulation, right? But result in a different POI?

And with the lighter bullets the bullet muzzle energies should be about the same as with the heavier bullet and the same charge of the "regulating" powder charge. But I guess one wouln't know this unless the lighter bullets were chonographed.

Will

The beauty of the 75% rule is that the lighter bullet load will BOTH regulate properly, AND hit with the same POI as the full power load.

With my loads in my 2 doubles the 75% loads not only regulated, but also shot to the sights, hitting the same place as the full weight bullet loads.
Since the 350gr loads have the same trajectory
as the 480/500 grain loads the 350gr loads hit with the flip us sights at distance, same as the heavier loads do.

You might have to go up/down a grain or two for best results, but the end result is you have a bullet/load more suitable for smaller game, with a little less recoil for fun use.

Even the Nitro for Black loads hit to the sights at 50 yards, and regulate as well.

Even the NfB loads are powerful enough for deer and pigs.

So you are using bullets that are approximately 75% in weight and 75% +/- of the powder charge, though it may be a different powder?

And they still regulate and have the same POI, at 50 yards anyway?

How simple is that?!!

At 50 yards, the "same" POI is a little questionable, as I don't know that is a fair test, as there probably isn't much difference in any load at 50 yards I would guess, but thanks a lot for clearing this up for me.

quote:

Originally posted by Will:
So you are using bullets that are approximately 75% in weight and 75% +/- of the powder charge, though it may be a different powder?

And they still regulate and have the same POI, at 50 yards anyway?

How simple is that?!!

At 50 yards, the "same" POI is a little questionable, as I don't know that is a fair test, as there probably isn't much difference in any load at 50 yards I would guess, but thanks a lot for clearing this up for me.

I agree re the 50 yard comment.

They need to regulate close enough at 100 yards
to make it valid IMHO.

100 Yard first shot will be fine to 150 yard second shot on game.

Will,

I don't think it is all cleared up for you....

quote:

Originally posted by Will:
So you are using bullets that are approximately 75% in weight and 75% +/- of the powder charge, though it may be a different powder?

And they still regulate and have the same POI, at 50 yards anyway?

How simple is that?!!

At 50 yards, the "same" POI is a little questionable, as I don't know that is a fair test, as there probably isn't much difference in any load at 50 yards I would guess, but thanks a lot for clearing this up for me.

NE450#2 said: "After finding the load that regulates the 480 grs, I shot the same powder chargewith the 350 grs. They regulated perfectly"

Concept is same powder, same charge but with a bullet that is about 75% of the weight of the standard full power loading.

Well, someone is confused.

You can't make plinking loads with the same powder charge.

Will

The 75% rule:
You take a bullet, that is 75% the weight [as close as you can get], to the bullet that is the standard load for your Nitro Double.

Then you use the SAME powder charge as your normal load.

You might have to adjust up or down a couple of grains.

The result is a load that is better suited to smaller game, that will regulate and hit to the sights.

Because the bullet is lighter, [and the powder charge the same] recoil will be reduced.

In testing out to 200 yards in my 450 No2, and to 300 yards in my 450/400 3 1/4", the trajectory is the same for the full power/weight load and the 75% load.


In testing Nitro for Black loads, I have been able to find loads that regulate well and will hit to the sights at 50 yards.

They still shoot good at 100, but because of their reduced velocity they do not have the same trajectory as the full power loads.

As to the different powder.

I first developed loads for my 450 No2 with IMR 3031, finding that 81 grains shot best with the 480 Woodleigh Softs.

I then tried 81 grains of 3031 with the Hornady 350RN, and found it hit with the sights and regulated well.

I then worked up a load with the 480gr bullets with IMR 4831, finding that 100 grains shot the best.

I shot some 350's with the same 100gr of 4831 and found they hit with the sights and regulated well.

I then tried 480's with RL 15 finding 88 grains shot the best, and the 350's again shot with the 480gr bullets.

I like RL 15 for full power loads best, but I continue to use 3031 for the 350grain bullets because I have a lot of it.

The 75% rule has worked in several British doubles, and in 3 Chapuis 470's.

HOLY COW! This gets more confusing by the hour.

Now I don't see the point of the 75% number.

In theory the same amount of powder behind any bullet weight should give approximately the same bullet muzzle energy, which indeed turned out to be the case for the 9.3x74R in the Chapuis for 270 gr. 286 gr., and 320 gr. bullets. I didn't test for regulation but the POI was about the same at 25 yards, just shooting off-hand.

It is nice that they also apparently turn out to be still regulated with the different bullet weights (as this is the reported magic of the 375 H&H) and different powder.

Will
I have never said anything about energy.

By using the 75% rule, you have a bullet that enables you to hunt smaller game with an ELEPHANT gun. Recoil is somewhat reduced, and the 75% load will regulate, and hit to the sights just like the full power load.

Since it has the same trajectory as the full weight bullet loads, it hits the same as it at all practical hunting ranges.

The 75% rule may not work for all double nitro rifles as each rifle can be a law unto itself, but I have not known of a case that it did not work.

If you just cannot get a lighter "deer/pig" bullet to shoot in your gun, then the other option is to get a full weight bullet from Hawk in a .025, or .030, or even .035 jkt. thickness so it will expand on the lighter game.

The whole point of the 75% rule is to give a double rifle owner a better bullet for shooting "normal" game.

Many of us really like to hunt deer, pigs, black bear, etc with our elephant guns.

It just so happens that the "physics" all fall in to place with a bullet that is 75% of the weight of the full load....

Or maybe it is just magic.... Whatever, it works.

quote:

Originally posted by Will:
Well, someone is confused.

You can't make plinking loads with the same powder charge.

Will if you want a plinking load try the nitro for black loads. They will be quite a bit lighter than the 75% rule loads.
Bill

Will

The 75% rule only works when your double has two triggers. A trigger reduction of 50% dictates different rules for those suffering from TDD (Trigger Deficit Disorder).

quote:

In theory the same amount of powder behind any bullet weight should give approximately the same bullet muzzle energy

I don't see this as being so, especially if the formula is tried with slower powders.

With the higher SD bullet, the burn will tend to be more complete. Switch to a lower SD bullet, and the pressure will drop faster as the light bullet moves away quicker. Lower pressures mean lower temperatures, and this can result in a less complete burn. The burn can kind of "fizzle out" with powders too slow for the combination of SD and relative case capacity. Further, what burn there is (with the lower SD bullet) will be at a lower pressure, which in turn will lower efficiency even more.

QuickLOAD isn't ideal for lower pressure simulation, but it does show trends. I tried Reloder 15 in a 400/350, switching from a 310 gn bullet to a 233 gn bullet. It estimates (very roughly) that the KE drops between 15 and 20 percent with the lighter bullet.

I'm still mystified by "why" this 75% rule works. It still seems it shouldn't, but I'll accept that it does.

I don't own a double rifle, but has anyone observed the same results with a bolt action rifle? It would be cool to have a practice/plinking load that hits to the same POI and have a good rule of thumb to begin load development. I'm thinking of my 404 Jeffery and my 416 Rigby.

Tony.. this is a great thread. We are always looking for ways to shoot our doubles more. I will try this in my 470 NE and Hawk does make a jacketed 350 grain bullet in that caliber.

My Austrian 470 NE double was built regulated for 101 grains of IMR 4831 shooting a 500 grain Woodleigh bullet. This gives a velocity of 2270 fps. I have found that it will shoot a 500 grain paper patch lead bullet with 98 grains of IMR 4831 to the same point of aim at 50 yards with the same or slightly higher velocity.

I have tried lighter loads with the 470 using a Starling lead cast gas checked bullet, (500 grains), and 45 gr 5744 with 2-3 gr polyester fill. These shoot to the same point of aim at 50 yards (scope and iron sights) as the full power load. Velocity here was 1572 fps with of course less recoil.

I will try this "75%" rule with a Hawk 350 grain jacketed bullet in the 470. 50 yards is ok for practice and tired eyes.

Thanks for all your research.

quote:

Originally posted by asdf:

quote:

In theory the same amount of powder behind any bullet weight should give approximately the same bullet muzzle energy

I don't see this as being so, especially if the formula is tried with slower powders.

With the higher SD bullet, the burn will tend to be more complete. Switch to a lower SD bullet, and the pressure will drop faster as the light bullet moves away quicker. Lower pressures mean lower temperatures, and this can result in a less complete burn. The burn can kind of "fizzle out" with powders too slow for the combination of SD and relative case capacity. Further, what burn there is (with the lower SD bullet) will be at a lower pressure, which in turn will lower efficiency even more.

QuickLOAD isn't ideal for lower pressure simulation, but it does show trends. I tried Reloder 15 in a 400/350, switching from a 310 gn bullet to a 233 gn bullet. It estimates (very roughly) that the KE drops between 15 and 20 percent with the lighter bullet.

I'm still mystified by "why" this 75% rule works. It still seems it shouldn't, but I'll accept that it does.

When I browse the reloading tables, indeed it usually takes a few more grains of powder to goose the lighter bullets to the same muzzle energy, probably for the reasons you state.

But if a double still regulates with lighter bullets at somewhat less than equal bullet muzzle energies, so be it. What's that joke about the law being more like a loosely defined guideline?

Dr.W

In several different 470's, shooting Hawk 350gr bullets 80grains of IMR 3031 worked very well. I would start with 75 grains and work up.
Velocity should be @2300fps.
You must use filler with 3031.

I would like you to load some with 101gr of IMR 4831 as well, to test the theory in your double.

quote:

When I browse the reloading tables, indeed it usually takes a few more grains of powder to goose the lighter bullets to the same muzzle energy

I should have checked that myself. I've played with QuickLoad enough to have some confidence in its ability to get the trends correct. It's certainly not accurate enough to assume it will be correct. In this case, it was.

The fact that the lighter bullet loads have less recoil and higher velocity predicts that the 75% rule should not work.

Less recoil: Less muzzle rise and less ipselateral kick-out by the side-by-side double barrel.

Higher velocity bullet: Less barrel time.

The laws of physics would predict that the 75%-bullet-weight-loads with nearly same powder charge and higher velocity will shoot to a POI that is different.

They should be crossed and low, when compared to the heavier and slower standard load.

Why does the 75% rule work?
It does not compute.

Ju ju.

RIP
I agree, the 75% rule does not seem to work for "single bbled" rifles.

However, it does work for doubles.

I do not know why either.

But I do know it has worked in enough different doubles to be called a "Rule".

If it doesn't work for singles (which was predicted), then perhaps there is some unintuitive rotation of the double in recoil, the result of the combined yawing and pitching moments applied. Combined gyroscopic effects don't compute in my brain, so I'll let the matter be.

quote:

Originally posted by RIP:
The fact that the lighter bullet loads have less recoil and higher velocity predicts that the 75% rule should not work.

Less recoil: Less muzzle rise and less ipselateral kick-out by the side-by-side double barrel.

Higher velocity bullet: Less barrel time.

The laws of physics would predict that the 75%-bullet-weight-loads with nearly same powder charge and higher velocity will shoot to a POI that is different.

They should be crossed and low, when compared to the heavier and slower standard load.

Why does the 75% rule work?
It does not compute.

Many things about double rifles DO NOT COMPUTE, but they work. It is only a guess on my part, but even a lighter bullets traveling in faster than a heavy one creates a SHARPER, or faster recoil than the larger bullet going slower. I really don't know the answer, but I'm glad it works, and since it does, I don't worry about why, I just use it!

This is one of those things that logic tells you it shouldn't work, like the fact that the barrels are physiclly converging, most think, and logiclly so,but mistakenly, the the bullet paths has to converge as well. They don't however, if properly loaded! The reason for this I understand, but the 75% rule, I can't say, only that it does work !

quote:

Many things about double rifles DO NOT COMPUTE, but they work. It is only a guess on my part, but even a lighter bullets traveling in faster than a heavy one creates a SHARPER, or faster recoil than the larger bullet going slower. I really don't know the answer, but I'm glad it works, and since it does, I don't worry about why, I just use it!

I think there is merit in this theory. Perhaps the sharper, faster recoil of the lighter but faster bullets cause the muzzles to move fast enough to make up for the decrease in barrel time.

But then, as Mac says, it works and that is enough.

JPK