I would like advice on the probability of finding the same POI with two bullet weights in a 308 Winchester?

For example, if someone were using a 165grain bullet at 2600fps with an 18" barrel, what would be expected in order to shoot a 110 grain bullet to that same point-of-impact in the same barrel?
Would one expect a similar POI if the light bullet was reduced to the same muzzle velocityas the heavier bullet?

Does anyone have any experience and formula for setting this up?

Only experimentation can give you an answer.
No two rifles will perform the same.

Until you actually try some different loads you won't know anything, no matter what anyone here says.

If you go with 180 grain spritzer and a 165 grain spritzer, it won't be exact, but close enough that effectively it will be the same for field shooting. In other words, your wobble from field conditions will be a bigger error than the bullet weight.

Too many variables for a simple answer so, as Snyper says, do the homework. Weight of gun and it's battery (ie., you), stock pitch, eieio, are in play.

My .308 RPR throws 135, 155, 168 SMKs to close to same POI despite a 400 fps range. Good luck doing that with a light sporter. Most extreme case I've seen is our little .243 WBY UL that throws 2 different 100 gr loads over 5" apart at 100 yds.

As mentioned, guns are different. My experience is that the best guns that shoot well with "anything" will also be easy to get to print similar POI with different loads. Lighter guns and guns that move a lot during recoil is harder. Stock design is important.

I have guns that also shift horisontally with different loads, that makes it hard. Some guns only need a tuning of velocity to get same POI.

I have one extreme shooter. 270w loads with 130 TTSX, 150 Norma SP and Hornady 150 SST all hit the 25cm gong at 500 meters with no sight adjustment. Same gun puts these loads plus 160 Partition into the 10 ring at 100 meters without adjustments. Rebarreled Tikka M65 270w.

I dont understand how this is possible as the trajectories must be different. They converge at 100m and 500m?

quote:

Originally posted by buckeyeshooter:
If you go with 180 grain spritzer and a 165 grain spritzer, it won't be exact, but close enough that effectively it will be the same for field shooting.

Maybe. But you won't know til you try. In some rifles the different in impact could be a lot.

So does anyone have any experience where the same velocity with different weights ends up doing the same POI?

quote:

Originally posted by 416Tanzan:
So does anyone have any experience where the same velocity with different weights ends up doing the same POI?

Only with my .308 RPR at 100 yd (ie., zero). Group centers are safely within 1" vertical dispersion there if I run the 135 and 155s at same vel as the 168s. It's a heavy gun, vertical buttplate in line with bore axis. As such, an exception that sorta proves the "rule".

Looking at it from a different angle, even that WBY UL .243 will print a 100 gr loading to the same impact as 75 gr heads so long as I adjust velocities.

I don't understand "nodes" as well as my geek engineer kids, but I think that's what I'm addressing with load variation.

Again. It could happen. But just because it happened in one instance does not mean it always will. POI is not a function of MV alone

There are many variables, the biggest of which is probably barrel vibration, which will vary with pressure, bullet weight, jacket hardness, surface area touching the bore, etc., and probably the phase of the moon
There is simply no way to tell except by shooting.

I should probably add that I am thinking that barrel harmonics might seem to match if the projectiles in a rifle were to reach the muzzle at the same time. the main difference would be recoil, since the heavier projectile would produce more recoil.

Personally, I have always loaded lighter projectiles to faster velocities in all my hunting rifles, so I do not have any real experience over the past 35 years with 'same velocity, different weights in one rifle'. But the question of grandkids and plinking loads raises these new theoretical ideas.

My 416 Taylor shoots 325 250 and 400 into the same hole 300grers are enough off that one would want to re sight

For what it's worth.....

I have a Remington 700 AAC that shoots 150gr Balistic tips with 46grns of Varget to the same point of impact as it does the 168gr Nosler custom comps with 44.4 grns of Varget at 100 yrds. I have not tested this at further ranges. At that 100yrd distance both groups can be completely covered with a quarter 100% of the time if I do my part.

I have a Ruger .223 that shoots 53grn Vmax, 55gr hornady sp, 63grn Sierra, 55gr rem Sp,and 62grn Federal fusion factory all to the same point of impact at 100 yrds. Best I can get out of the gun is 1.5" average no mater what I shoot through it all groups hover around that mark with horizontal stringing. I haven't grouped it at 300yrds, but the loads I shoot through it all hit 2 liter bottles with the same holds at that distance.

Granted a roughly 10 grain bullet variation isn't much.

I could put down a lot of words but I don't have a clue. roger

How about loading up two loads with the 110gn bullet. One moderate, one mild. Then go to the range and compare these with the 168gn load.

That should give some pointers.

I do that with a 308 by using a Leupold scope with target type Adjustments. Seems a lot simpler to me. Dial in the load you are using. The only gun I ever had that only had vertical variation as you changed bullet weights was a 375 H&H. Every other gun I tried different weights had both vertical and horizontal change.

quote:

Originally posted by Snyper:
Only experimentation can give you an answer.
No two rifles will perform the same.

Until you actually try some different loads you won't know anything, no matter what anyone here says.

EXACTLY... anyone that suggests otherwise is talking out of the anal orifice.

Once again, the first post on a thread is often the best, and this thread is no exception.

That is something that just depends on the individual, and what someone elses gun will do is of no value..you simply have to try them, you need to experiment and find out what your gun will do and BEFORE you hunt with it.

quote:

find out what your gun will do and BEFORE you hunt with i

Yup.

What I'm doing now is planning for grandkids visiting Tanzania.
The gun and calibre is not yet chosen. I don't think the grandkids will be ready for even my wife's 375, or son's 338. So . . .

So what light caliber could 9-12 year-olds shoot for learning and handling and still use in the field, hunting an African animal like a hartebeest or warthog? I'm thinking a 308 is better than a 243, 6.5Creed, or 7-08 in Africa. A youth model with an 18" or 20" barrel will drop the velocity 100-150 fps from published loads (good for their recoil tolerance) and hopefully won't be too loud. My thinking is that some training rounds could be available with 110-grain bullets that would be loaded to the velocity of the hunting bullet loads (probably 165 grain, maybe 2550-2650fps). If the barrel vibrations throw the light bullets to the same general POI as the hunting load, fine. If not, then perhaps some judicious record keeping and a scope that tracks well can allow one to switch between loads without too many extra bullets fired on re-sight-ins. Limited ammunition and tailored hand loads in Africa always takes a little extra planning.

quote:

Originally posted by 416Tanzan:
So does anyone have any experience where the same velocity with different weights ends up doing the same POI?

Yes, some rifles will do that, and I have no idea why.

Some rifles, on the other hand cannot shoot the same weight, from different manufacturers, to the same point of impact.

I built a 22-243 Middlstead, and that rifle shoot bullet weight from 40 grains to 52 grains in exactly the same point of impact, in less than 1/4 of an inch.

Built a 416 Rigby Improved, and was trying the first load in it.

It was a 400 grain Trophy Bonded bullet, with 105 grains of H4350. This load shot well in a 416 Weatherby which I hunted with.

I fired 3 shots, and looked through the spotting scope.

I saw one ragged hole!!

I resized and reprimed the same 3 cases, and loaded the same powder charge, and loaded the Barnes Super Solid brass bullets, and fired the 3 shots at the same group.

The whole group was about 0.70 of an inch, for 6 shots.

I stopped right there, and used these loads to shoots several elephants, and many other game animals including buffalo and two lions.

One thing you can take to the bank is its a lot easier to make a big bore shoot a soft and a solid or different heavy loads that weigh close to the same weight than it is to make a 308 shoot a heavt big game bullet to the same POI as a varmint bullet..It can be done in some rifles however, but less likely or at least will cause you a worse headache..

quote:

Originally posted by 900 SS:
How about loading up two loads with the 110gn bullet. One moderate, one mild. Then go to the range and compare these with the 168gn load.

That should give some pointers.

900, Gave the best advice I could offer.

IME your lower velocity 110 reload is going shoot lower at 100 yds than the higher velocity 110.

Experimenting his way will at least get you going in the right direction. Shooting the 165 with them on the same target will give you an idea of how far you need to go.

In my 9.3 X 62 shooting 250 gr and 286 gr loads I had best luck with forearm bedded, rather than free floated. About 2" elevation difference.

Tanzan,
IMO, the ideal wife, daughter, grand kids rifle in Tanzania would be the 250-3000, its mild of voice and recoil, can be loaded down a good deal and still be a credible killer of the lighter game animals..

Ive shot game with factory WW and Rem. corelokt 87 and 100 gr. bullets as did my youngsters at about 12 to 14 years..Also depends on what size your kids are..

9 to 12 is quite young for Tanzania,I would prefer to wait until they are in their teens. Tanzania can be a dangerous place on rare occasions IMO...Spent a lot of time there over the years. but that's not any of my business, just a suggestion for what its worth.

quote:

Originally posted by Atkinson:
Tanzan,
IMO, the ideal wife, daughter, grand kids rifle in Tanzania would be the 250-3000, its mild of voice and recoil, can be loaded down a good deal and still be a credible killer of the lighter game animals..

Ive shot game with factory WW and Rem. corelokt 87 and 100 gr. bullets as did my youngsters at about 12 to 14 years..Also depends on what size your kids are..

9 to 12 is quite young for Tanzania,I would prefer to wait until they are in their teens. Tanzania can be a dangerous place on rare occasions IMO...Spent a lot of time there over the years. but that's not any of my business, just a suggestion for what its worth.

Last year (2015) our 7-year old grandson visited us in Tanzania. He was able to shoot a Marauder .25 PCP air rifle into a water jug, but needed special support to hold the full-sized rifle. However, in a couple years he would like to go out 'camping'. So the question of rifle approaches. And since my wife and I have maxed-out calibers at 375Ruger and 500AccRel, we could use a little camp gun that the grandkids could shoot. My son's 416 and 338, loaded to the gils, don't help as a loaner, either.

Your suggestion of a 250Savage(3000) is appreciated. In fact, my son and I have occasionally floated the idea of a 257 "Bob".

Practically considered of course, there is little difference from a .257 80grain TTSX at 3200fps (250Savage), .257 80gnTTSX at 3300 (257Roberts), or a .243 80gnTTSX at 3350 (243Win). I mention this because we have a 243Win (M70 Featherweight Compact 20" barrel) sitting in California for exactly the purpose of training grandkids.

The question is bringing a small rifle to Tanzania. The Ruger American Compact at 12.5" LOP, 6 pounds bare, 18" stainless barrel looks like a great package for grandkids and visitors. Its caliber choices are 223, 243, 7-08, and 308. (A Nikon Pro-Staff 2-7 is small and fitting for such a rifle.)

The 223 is out of the question for me, although my son used a 222 over thirty years ago effectively on small antelope (duiker, oribi, reedbuck, easily, and cob, with care). The 243 could work for grandkids, but it is too small for me to want to carry in a forest when grandkids were not visiting. To me, the 7-08 and 308 are two peas in a pod, but the 308 is the easier to get components and load for. Ditto on a choice between a 7x57 and 308.

That is why I am thinking of .308 165grain 'full hunting loads' at 2600-2650fps and 110grain training loads at 2600-2650fps. The light bullets will only generate about 8-9 pounds of recoil, something between a 223 and 243. The full hunting loads will generate 17 foot pounds of recoil but we all know that recoil during a hunt is almost not perceived. So my current thinking is that if a kid can handle a 12.5" LOP, 7-pound scoped rifle, (certainly doable somewhere along the 9-12 year range), then they should be able to practice with 9 pound recoil and take a game shot with 17 pound recoil. My son was 11 when he graduated from his 222 to a 270 (with a too-long-for-him 14" LOP and no recoil pad!). Basically, the 308 and 270 are pretty close in recoil, though the Ruger American Compact might jump a little more, probably weighing 1-1.5 pounds less than our old pre-64 270.

Anyway, those are the thoughts. I've still got a year to muse on this and watch the manufacturers' offers in the coming year.