two diff loads...same point of impact ?

[mike in co]

i have a nice load for my 20" 44 mag and the load is mild(290/1370fps). i want to put together a lite load, but whats the chance of getting to the same point of aim...say at 50 yds ?
i have the same 290 , a 280 and a 265 bollit available.

thanks
mike

[S.R.Custom]

That's going to be a tall order. So much of POI is recoil impulse. A lighter load will, obviously, recoil less...

The only rifle that I have ever gotten close to this is the 7mm Remington Mag. At two hundred yards the difference in POI between a 150gr, 160 gr, and 175 gr bullet is negligable. But that only happens with equivalent powder charges. It seems that with the 7mm, the trade off between velocity and ballistic coeficient is such that the effects of each is almost perfectly offset by the other.

Forty-four caliber bullets, on the other hand, don't have much of a BC to play with. It's conceivable that you could get a hot 180 grain load to hit to the same POA as a light 240 or 300 grain load. (At 50 yards, heavier bullets generally hit higher than light ones with equivalent powder charges. And I only bring up the 180 gr. bullet as it's only that kind of weight difference that will have a significant enough trajectory difference to matter. But what use is a hot 180 gr load?) And with heavy bullets vs light bullets in a light rifle, the differing torque effect starts to affect lateral POI...

That said, I've always wanted to put a multi-blade express sight system on my Winchester 92 as a way to shoot multiple loads without having to dick around with the sights... One of those "some day" things...

[Bass Ackward]

Interesting and elusive quest. Your short range requirement makes it all the more feasible. Even more realistic the lower the line of sight to the line of bore.

[MTWeatherman]

Take some experimentation but my guess is that you could come up with a usable load. However, I'm betting you'll need a lighter bullet to accomplish it. Been down that road with my .44 Mag Winchester Trapper.

What I discovered is that the large amount of variables involved in the venture makes for no hard and fast rules, in general, and that the only way to try to achieve your goal is with significant experimentation with different powders and bullets. That experimentation did lead to development of a rule...for my rifle.

POI is obviously dependent on exactly where that barrel is pointing when the bullet leaves the barrel...that is heavily dependent on how much that rifle has recoiled backward, upward and torqued when that bullet leaves the barrel (in response to the lateral and rotation acceleration and velocity of the bullet and powder gases) and that in turn is dependent on rifle and bullet weight, bullet velocity, barrel length, barrel time, harmonics, powder type and weight, how the rifle is held, etc, etc. Even with two different powders delivering the same bullet at equal velocity, POI will change...due to the different acceleration curve on both the bullet and rifle, differing harmonics, and the difference in recoil due to the differing powder weights. Although, as a general rule, with an equal load heavy bullets do tend to hit higher than lighter ones with handguns but lower with rifles...this due to the differing barrel lengths and recoil behavior among other things...there are no hard and fast rules due to variation in the many factors mentioned. The point being...results are not always what you might expect.

Case in point. Here's what I discovered for my rifle...a 16 inch barreled .44. It may not have any application at all to you or your rifle due to the 20 inch barrel length alone....other issues aside. At 25 to 50 yards, a light load of fast burning powder with a relatively light bullet will approximate the POI of a heavy load of relatively slow powder with a heavy bullet. To me, that's totally counterintuitive...the load that approximates the POI of the heavy recoiling load...is an extremely light recoiler with a light bullet at much lower velocity. Barrel time is obviously a major issue here.

The heavy load is the 429244 Lyman 260 gr. bullet pushed by 23 gr. of H110. Red Dot at 6 gr. with the Lee 200 gr. (Actually 210 with WW) will duplicate this load in the vertical but hits about 1 inch left at 25 yds. Note, thisis likely not due to torque...would expect the reverse. Increase the load of RD to raise the velocity and it will shoot lower...reduce the load and it will shoot higher. With the same bullet, the medium burners such as Unique and Universal start low and shoot higher as the load is increased (within the range I tried). Use a heavier bullet with any reduced load, such as a 240 gr. and all shoot low...with powders I tried, velocity has to be too high in a 240 PB bullet to achieve the POI without leading. However, there well may be a powder out there that could do it. Never tried any real heavyweight bullets due to the 38 inch twist...but who knows what that would yield in the right rifle.

I've accepted a windage error in order to maintain the similar vertical POI...it's minute of beer can to 25 yds...compensate a bit for it and it's a totally usable load to 50 yards. My suggestion would be to try a similar load in your rifle...about a 200 gr. bullet with about 5 grains and 8 grains of Red Dot or Bullseye. Try other bullet and powder combinations as well...a light and a moderate load. Once you find a combination that brackets your POI...then start tweaking the load.

[MTWeatherman]

Should add a further consideration to the above. You may be able to achieve that approximate POI that you are looking for. However, you will be lucky indeed if it turns out to be the most accurate one for that bullet. You'll like have to be willing to compromise accuracy somewhat on that reduced load in order to have the convenience of a similar POI.