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Which "Max Load" do I use?


Wild Gene

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When I look at the Hodgdon Manual for a 155 grain bullet for a 308 it shows a Maximum load of 46 grains. (SIE HPBT)

When I look at the Hornady Manual for a 155 grain bullet for a 308 it shows a Maximum load of 44 grains. (A-MAX)

Both figures are for H4895 powder but the bullets are different. I am doing the math for the Dan Newberry OCW test. So, do I use 46 as my max load for the calculations or 44?

If I use his formula, and 46grains as my MAX load, my loads are 41.4, 42.2, 43.1, 43.9, 44.2, 44.5,44.8, 45.1, 45.4, 45.7, 46.0 and 46.3.

I have a couple pounds of H4895, that is why I am using that powder with the 155 AMAX's I also already have.

Rifle is 20" barrel, 1-12 twist.

Get very good consistent hits our to almost 700 yards so far on steel, but I can't shoot a 100 yard group under 1.75". Today, I shot groups and they stunk (2"), but then I went to the 14" steel gongs and made consecutive hits from 300, 500 and 600 yards easily. I pulled out my AR and shot a .33" hundred yard 5 shot group. I am totally perplexed. I was shooting Hornady Steel Match Ammo with the 308, and it shoots a ton better than the Federal Bulk ammo I have. I know the 155 is probably not the optimal weight bullet, but like I said, I have a bunch of them to shoot up (around 300).

Help please.

Thanks,

WG

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14 inch target at 600 is abit over 2moa, which you are shooting at 100, so yes, you should be able to hit a tgt bigger than 2moa with a gun/bullet combo that is shooting 2moa.

I don't do the ladder test, tried it and can't figure out what the results are telling me. so I just load 5 rounds at say 43gn, 5 at 43.5, etc. Then shoot em in seperate groups. The best load wins!

And fyi, I never could get 4895 to group tighter than 2moa...

I got better results with 8208, Varget, and AR comp...

Good luck!

jj

And another fyi, I do all my load test group shooting at 200, easier to see the results...

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You could always load for the ladder using the lower max watching for pressure. If you don't get any, you could slide your charges up the scale a little bit. What you are looking for is an accuracy node, not the max velocity. Different bullets have different max loads as they are different even if they weigh the same. A lot of it has to do with how much bearing surface they have. I use the method that jj does, but seeing that I have a shooting lesson with Dan this week, I'll probably be giving an ocw test a try in the near future. It makes good sense as long as your bullets tell you something. One thing to remember, a lot of people can say you should do this or that, but the bullet never lies. What it does is what it does. Learn from your bullets.

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Its a given that different loading manuals will show different max loads if the only comparison is powder and bullet weight.

The components will vary and the chambers / barrels that were used to develop the load data are all different.

Even if you duplicate all components, you cannot duplicate the test chamber.

Therefore, if I am using data from a bullet manufacturer, and I can duplicate all other components, I use their max load.

If not, I gather as much data from other sources as I can for the bullet weight/powder combination and take an average.

Either way, I use ladder charges to test and work up to the average max.

If I see no pressure signs I may push farther and go to the highest published load.

That said, I wouldn't push the load to the very limit unless there is a reason to.

Really hot loads leave no margin for error and are really hard on brass and barrels.

However, if you are working up a long range target or hunting load and need every bit of energy/velocity you can get, then fine, go for it.

If you are shooting at relatively close range, accuracy is the deciding factor, not speed.

A round traveling at 2800 fps will punch a nice clean hole in paper, ring a steel plate or put down a buck just as well as a 2900 fps bullet.

If you find yourself reloading as hot a possible and always pushing the limits of your firearm and cartridge,..... get a bigger gun.

Tls

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Rigger, yep, I figured out the same thing when I did the math in my head. Here at home I routinely hit 8x10" plates out to almost 700 yards, if I get my wind right.

Shooter, I was thinking the same thing. Just load the whole range of rounds and then shoot away and watch for signs of excess pressure.

What I just don't understand, and am getting hung up on is, and probably for no good reason, is why does the Bullet Company have such a different MAX load than the Powder Company. Is there really that much variation in two 155 grain boat tail bullets?

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Reread the op, looks like you want better than 2moa with a bulk 155gn fmj bullet?

I would be surprised if you get any better performance with that bullet...

155 Palma, or jhp match, yea, should get better than 2moa.

Imho

jj

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No, I want to use a bunch of H4895 and Hornady 155 A-Max bullets I already have.

I am going to run the numbers for both MAX loads. All this will do is to give me a few more cartridges to load on the lower end. Where they are similar on the middle to upper end, I will just use the numbers I derived for the higher powder charge. I will then just start shooting, watching for signs of excess pressure when I approach the 44 gr. max load suggested by the bullet manufacturer.

I probably should have simply worded my question as "which maximum powder charge do I use, the Bullet manufacturers, the Powder manufacturers an average of the two or the lowest or highest".

wg

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Have you thought of shooting some FGMM loads? They shoot pretty good out of most guns, and are kind of a benchmark that you can use to see if your gun will shoot or not. If they shoot pretty good, you know that you can use that as a starter point and go from there. I know how it is when we have bullets and powder, and want to shoot what we have, especially when this stuff is not easy to come by sometimes.

38Superman is also right when he talks about pressure. We never know all the specifics about the firearm that they shoot. How tight are the chambers, how long is the throat, how many rounds are down their barrel, and how long are their barrels. It all comes into play with pressure, and every gun is different. Mix in a few lawyers to protect the home company, and loads may be reduced. That's why I said start down with the lower max and go from there. You can always go up if things look good.

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Those are different bullets with different bearing surfaces. HPBT is not the same shape as a AMAX. That changes contact in the barrel thus resistance and pressures. Just a thought.

[Edited to correct from VMAX to AMAX. My original point remains intact despite the type]

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I have a bunch of the AMAX not the VMAX. AMAX is a HPBT with a ballistic cap on the end.

The Steel match shoots 1-3/4" groups, and is much better than the bulk Federal 308 I have lying around in this rifle. I'm hitting long steel, I just haven't figured out the recipe for a 1" group at 100 yards. That is the perplexing part. I had a few friends shoot the rifle and they aren't shooting it as well as I am.

I am impressed with the VMAX in my .223 ammo. I'm getting 100 yard 5 shot groups measuring .33" on center from Atlanta Arms Match Ammo and my Seekins Rifle.

Too many "Max's"! Haha.

wg

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I corrected my previous post. I totally fat fingered that on my phone. :-)

Shapes are still different from brand to brand and product line to product line. Secant, tangent, or hybrid ogive profiles. Differences in "boat tail" shapes at the base. Some bullets extend the jacket farther forward than other hollow points to change the relative locations of centers of pressure and mass. And on and on.

OK, so I broke out Bryan Litz's "Applied Ballistics for Long-Range Shooting" to take a look at the two bullets. Their dimensions are different and they happen to correlate with the idea of bearing surface coming into play with the two different maximum loads across the two courses you referenced in your original post.

Let's look only at the straight sections of the bullet bodies since those surface areas are clearly the majority portion of the bullet bearing surface on the bore. There are two models of Sierra 155 grain Palma HPBT listed in this text.

  • Sierra #2155 - 155 grains, total length = 1.131", straight cylindrical section length = 0.273", BC(G1)ave = 0.417, BC(G7)ave = 0.214
  • Sierra #2156 - 155 grains, total length = 1.210", straight cylindrical section length = 0.230", BC(G1)ave = 0.449, BC(G7)ave = 0.229
  • Hornady Amax - 155 grain, total length = 1.218", straight cylindrical section length = 0.376", BC(G1)ave = 0.415, BC(G7)ave = 0.212

As we can see from the length of the "straight" cylindrical portion of each bullet, the Hornady has much more bearing surface. With that we should expect more friction in the barrel and thus more pressure. For a bullet that generates more pressure we should expect a lower maximum powder charge to be recommended by the sources.

Your listed sources from your original post show 2 grains *less* max load for the Amax bullet. This supports the idea of bullet bearing surface being one variable that is involved with this issue of different recommendations. We can't assume these projectiles are point masses. Their shapes matter in many situations; not only in aerodynamics.

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Thank you Michael!

That supports my findings too, except I based mine on actual volume of powder observed in the case. I don't think I could have fit another two grains in a case. I went ahead and lowered my Maximum charge and based my OCW calculations on that. Now I just need an hour to fire my 27 rounds based on their procedure.

wg

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Determining the ma load is easy; work up the powder until the bolt gets stickey and then back it down about .3-.5g or so. as far as an OCW test goes i tend to stick to .5g as its just easier to do. Regarding shooting 155s; these don't always shoot all that well in non-specially set up rifles. The Sierra 2155 and 2156 all have very short bearing surfaces, i cant comment on the Hornady amax bullets but i suspect the bearing surface is short too. These bullets generally do not jump very well and need to be seated close to the lands. They also need to be seated into the case enough to develop enough to hold onto the bullets, this is usually at a minimum 1/2 the bore diameter, more is usually a little better. In most factory guns you are going to have a hard time to accomplish both of these things. Rifles for Palma competition are set up to shoot these bullets and have a short throat and a tight bore.

Shooting and hitting 14" gongs is not a measure of accuracy, you need quantitative results on paper, not hit or miss.

What ever you end up doing, your max reliable range is going to be limited to the velocity that your 20" barrel develops and the point where the bullet transitions from super to sub sonic. in a 20" i suspect this will be 800M max, check a ballistics calculator to be sure.

I would not try too hard to get those 155 AMAX to shoot, if they dont shoot, then they dont shoot in that barrel, save your self some time, effort and barrel wear and try a 175 SMK. Sierra also makes a 150g SMK bullet that has the same profile as the 168g SMK up front but with a lower bc and it will take the jump.

Seat those 175 SMKs into the case, they take the jump fine, load with FGM primers and some H4895. They should shoot well.

This is not to say you cant get those 155 amax to shoot in a factory barrel, i did it in a 24" win M70 HV and did well with it at 1000K but i dam sure made sure they were going supersonic when they made it all the way down there.

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  • 5 months later...

I try and veiw max loads in load data as a report that the testers got that day. I can think of a few examples where there is up to a 2 grain or more difference with the same bullet and powder. There are known errors in manuals from time to time as well.

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Thanks for the replies.

I just find it strange that if you have Brand X bullets and Brand Y powder, you can look at Brand X's information and it might say 43 grains for the combination and you look at Brand Y's information and it might say 45 grains, for the exact same X+Y combination.

That's what I was getting at.

By the way, saved myself tons of time. Bought a GA Precision rifle and it has shot everything I have fed it SUB MOA.

wg

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I've concluded published load data is is not always correct or uniform. I've seen powder manufacturers publish one set of data for a given powder/bullet/OAL and the bullet manufacturer publish different data for the same exact combination. One reason may be that they use different chambers, different temperatures, etc in their testing. Another reason may be that they've tested different batches of powder and different batches of the same powder can have slight variation in performance. Add different bullet profiles and it gets even wonkier.

Start with a middle of the range load that both source agree on, and work your way up until you are happy watching for pressure signs and strange velocities. If you get a new batch of powder, back it off and test again.

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  • 2 weeks later...
  • 3 weeks later...

Different makes of the same weight bullet produce different pressure and velocity numbers. The shapes of the bullet will also effect pressure and velocity. All things equal, a bullet with a thicker jacket will produce higher pressures then a thinner jacketed bullet. In an extreme case a solid copper bullet will produce more pressure by a wide margin. Reloading books serve as a guide for reloading. In some cases you can put well over a books max charge in a case and have sub max chamber pressure. Long throats and seating bullets out effectivley reduce pressures for a given charge. Barrels that are worn will require a little more powder to maintain velocity then when they were new. When you are reloading for a bolt gun the first sign of pressure that you usually run into is a stickey bolt. In a semi auto you normally start to see marks from an extractor. Looking at a primer is a universally poor way of evaluating pressure, you have to look at the brass, feel the bolt lift/ look for marks as well as evaluate velocity over a cronograph. Also consider some lots of powder are faster or slower then others, Varget is natorious for this. With a 20" .308 your going to have trouble maintaining a supersonic past 800 yds at best so dont push it. If its a remington rifle then your bullets are probably seated out long.

If the rifle is still shooting 1.75" or so i might try another bullet and see what happens, the 155's just might not work as they dont like to jump and if you are seating them out so there is bearley any bullet left in the case then that will not help anything at all. A Sierra 175 is a good place to start and they are not sensitive to jump.

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