Changed powder, now shooting low?

[Arka3L]

Hey all,

I decided to register to get some help as the original person who helped me just responded with "harmonics" but I don't think its the case.

Little background: I started some new loads for my .308 Rem 700 SPS with a fellow range goer and he set me up with IMR4895 powder. We tested 4-5 loads until we got the perfect group and ended up making a couple hundred rounds of 41 grains. Got my new scope zero'd, and was literally stacking rounds at 100 in the bullseye. Then the ammo shortage happened... 10 months later, I finally get my hands on components and start loading again but no IMR anywhere. H4895 however was available at the local store so i picked up 3lbs. Many sources said that it runs a little hotter so one should go down a grain and go up from there.

After 5 different loads starting from 40 - 42 in .5 increments, every load was shooting roughly 3" lower than my IMR rounds were. Harmonics is one thing, but to have 5 consecutive loads all shoot low in the same region? What could cause this? I don't own a chronograph, so I can't tell you the speeds, but knowing my bullets are shooting lower makes me feel like they're going to be even more effected down range?

 

[redbullitt]

Adjust your scope lol.

Every powder and combination is going to to act different, and it will react differently with your rifle. I can switch brass and get a different POI. The same can be said for projectile and powder and even primers sometimes.
The H4895 is just a couple places hotter on the burn chart, so not a huge difference.

What projectile are you running? Any other changes you might be overlooking?

Hodgdon lists 41.0- 43.5 with H4895 with a 168 smk at a short 2.800 coal. At what point did you find pressure signs?

You should work up a new loading if you change a major component like projectile or powder. Just the way it is. Get a load that works and run with it.

 

[Big Z]

Fuck it. Crank the dials and rock on. One could say, that a bullet exiting the barrel faster will be exiting at a point in its whip that is lower.

 

[chefcam864]

Your friend was right, in saying it was harmonics. It would take a MASSIVE difference in velocity to hit 3" low at 100. Like Big Z said, ef it, crank the turrets, and get to shooting. You have the better of the two powders now anyways. (I REALLY like H-4895!)

 

[Rem7targetactical]

Learn how an OCW test works, perform one, and you will have the answer you are looking for.

 

[918v]

You should have loaded 42grs of IMR4895. That's where the node is. And that's why H4895 is shooting lower.

 

[Arka3L]

Adjust your scope lol.

Every powder and combination is going to to act different, and it will react differently with your rifle. I can switch brass and get a different POI. The same can be said for projectile and powder and even primers sometimes.
The H4895 is just a couple places hotter on the burn chart, so not a huge difference.

What projectile are you running? Any other changes you might be overlooking?

Hodgdon lists 41.0- 43.5 with H4895 with a 168 smk at a short 2.800 coal. At what point did you find pressure signs?

You should work up a new loading if you change a major component like projectile or powder. Just the way it is. Get a load that works and run with it.

One thing i didn't take into account was that I was also using different bullets. I went from 168 Nosler HP to 168 Amax. My other components are all the same as with the previous loads. Adjusting my scope is an easy fix but I wanted to understand the ballistics in a little more detail as to why they were all falling lower than my previous powder. It seemed like they weren't running as fast.

You should have loaded 42grs of IMR4895. That's where the node is. And that's why H4895 is shooting lower.

Tried it, didn't work out for me, 41 was my sweet spot.

 

[aloreman]

So u changed bullet and powder and cant figure out why it shoots different? Thats odd

 

[918v]

One thing i didn't take into account was that I was also using different bullets. I went from 168 Nosler HP to 168 Amax. My other components are all the same as with the previous loads. Adjusting my scope is an easy fix but I wanted to understand the ballistics in a little more detail as to why they were all falling lower than my previous powder. It seemed like they weren't running as fast.


Tried it, didn't work out for me, 41 was my sweet spot.

And how did you determine it was your sweet spot?

 

[Arka3L]

So u changed bullet and powder and cant figure out why it shoots different? Thats odd

Preschool is out already?

And how did you determine it was your sweet spot?

Well, let's see.. 41 = stacking rounds. 42 = not stacking rounds... I may be relatively new to reloading but not my marksmanship.


Seems like this thread is over if I'm going to be treated like an idiot by people. We ask questions because we don't know the answers, don't make us feel like fools, there's a sticky about this very issue.

 

[918v]

Mr. Sensitive:

The tightest group is not the sweet spot. The sweet spot is defined as a powder charge weight in the middle of a range of charge weights which does not disturb the point of impact. So, if 40.8grs, 41grs, and 41.2grs all print in the exact same spot, then 41grs is indeed the sweet spot.

Did you work up the load this way or did you just go with the tightest group?

 

[Rem7targetactical]

Hence the OCW test.

 

[Thumper580]

Start over with your current components and find a new accurate combination. Very true that every component change will move the POI around. Keep good records on each combination that gives you the results you are happy with. Good luck.

 

[CK_32]

OP did you really just state you changed both bullets and powder and you don't understand why your getting POI shift?

Before you get jumpy I'm not saying this in a dick tone but its kinda self explanatory. But I'll go into some detail. For 1 IMR48 is a slower burning powder than H48. So your chamber pressure will be higher going to H48. 2 you changed the bullet manufacture, you might as well have started shooting a savage. Although bullets have the same weight their design, quality and performance is very different. So again changing bullets with the same powder will still end in a different node and POI shift again due to the bullets not being the same. Hell even lots can vary by the same company, let alone a new maker.


Again dont take this up the azz your asking for an explanation, I'm explaining exactly whats going on. Harmonics probably has a small factor but I think the biggest factor is you just went to a complete new load aside from the primers and brass..


This is also why so many buy 30+ # of materials and go about their loads/components as gospel.

 

[M36]

Arka, I dont think anyone is questioning your marksmanship. From my old fashion ways of using an accurate round for hunting out to 300 yards or so, I would be happy with your 41 gr load and that is what I would use. But for long range shooting and trying to change my ways of thinking about loads, I think the 42 gr shots are showing the smallest vertical spread which is what the others are trying to explain is a result of the Ladder Test and/or the OCW method. That small vertical spread is showing that your sweet spot, harmonic wise, for your rifle is in the 42 gr. ball park, for that load you made. The only thing to really narrow it down would be to shoot a 300-500 yards ladder test and see what happens, then dial it in from there. But checking out the two tests would probably make more sense of what the others are saying.

Im new to long range shooting and Im trying to learn also. If Im wrong, Im sure someone will jump in and Ill learn something else.

 

[Garyc]

Changing powder, brass, primer, etc. will often change the point of impact a little. Changing bullets is pretty much guaranteed to change the point of impact. A 3" POI shift from changing bullets is pretty small, it'll often be a lot more than that. You can't work up a load and then substitute a totally different bullet and expect it to shoot to the same point of impact, it doesn't work that way. Sometimes you'll get lucky and they'll be close, but that's just luck and by no means normal.

If the loads you're shooting now with the Amax are grouping well then adjust your scope to their POI and go with that. There's nothing unusual at all about a 3" POI shift when switching bullets, and it doesn't mean the new load is slower than the old or doesn't shoot as flat.

 

[rduckwor]

First rule:

ONE VARIABLE AT A TIME.

 

[Arka3L]

Arka, I dont think anyone is questioning your marksmanship. From my old fashion ways of using an accurate round for hunting out to 300 yards or so, I would be happy with your 41 gr load and that is what I would use. But for long range shooting and trying to change my ways of thinking about loads, I think the 42 gr shots are showing the smallest vertical spread which is what the others are trying to explain is a result of the Ladder Test and/or the OCW method. That small vertical spread is showing that your sweet spot, harmonic wise, for your rifle is in the 42 gr. ball park, for that load you made. The only thing to really narrow it down would be to shoot a 300-500 yards ladder test and see what happens, then dial it in from there. But checking out the two tests would probably make more sense of what the others are saying.

Im new to long range shooting and Im trying to learn also. If Im wrong, Im sure someone will jump in and Ill learn something else.

Thanks, I understand what you're saying about vertical variances. However, the third 42 grain round was off paper. It seems that somewhere between 41 and 41.5 grains would be my ideal spot correct? Both of these loads seem to have the smallest variances between each shot.


My next question, to anyone who's interested in answering, how OCD are you with your loads? Due to some of the responses, it seems that i should keep in mind that even bullets from the same manufacturer can differ, most likely weights. For those of you who shoot long range, and not too concerned with shooting through the same hole on paper at 100 yards, what is your tolerance on variances? Do you weigh every bullet, weigh every brass, weigh each powder charge multiple times, ensure that every round is the same length within a thousand of an inch..? I enjoy reloading on the terms of getting an accurate load made for my rifle, but on a single stage press and limited time, what are the most necessary checks? Do you also let the barrel cool between each shot?

 

[Big Z]

I keep components in the same lot as long as possible (buy in bulk). I throw my charges. Mostly I keep shit tight and square. I false shoulder, jam bullets, anneal & deburr flash holes. Size only enough for positive function. I don't use die locknuts with rubber in 'em. Lotsa shit will 'surprisingly' fall into place.
Just a quick 2 cents..