Load Data not the Same

[HunterDave]

I'm new to reloading and I need to make sure of something before I go any further. I have worked up loads for my 3006 right up to the max as published in the Nosler 6 manual. There are no signs of over-pressure and the groups have gotten tighter. I've cross referenced the data in my manual against the IMR powders load data site and I found a big difference in the max allowable load for my 3006 loads. I'm using IMR 4350 and 165 gr Nosler BT bullets.

According to the Nosler 6 manual the max load is 57 gr (100% volume) but according to the imr data on the internet 60 gr (compressed load) as the max. I checked a different site and 60 gr was also listed as the max.

Since my groups are getting tighter at 57 gr I would like to go to 57.5 to see if they get tighter yet. As I wrote earlier there are no signs of over-pressure at 57 gr. My question is this......

Do I stop now at 57 gr since this is listed as the max in my manual or should I try for a tighter group at 57.5 gr which is safe according to other load data?

[elkhunter11]

Do I stop now at 57 gr since this is listed as the max in my manual or should I try for a tighter group at 57.5 gr which is safe according to other load data?

Manuals are guidelines,they can't take into effect variations in chamber or barrel dimensions,powder lots,or brass capacities.That load may or may not be safe in YOUR rifle.It may not show pressure signs in cool weather,but it may in warm weather.

[leo]

What methods are you using to determine "pressure signs"?

[HunterDave]

Originally Posted by leo

What methods are you using to determine "pressure signs"?

That's a good point. I suppose that I should take my vernier calipers to measure the casings. Right now it's just a visual inspection of the casing and paying attention to what is happening with the rifle (ie. hard opening the bolt, etc).

I still don't understand why the max capacities would be so different depending on which manual you use. Obviously there's no set standard but if these reputable companies are testing the ammo shouldn't their findings be close at least?

Does anyone have a different max load in any manual besides the two that I found?

[wwbirds]

It actually prompted me to buy the latest Nosler book as my old one was at least 20 years old and listed 56 grains of IMR 4350 as max. I worked this exact load up for my T3 last year but with Hornady SST and Nosler Partitions in 165 and the tightest group for me was 56 grains of IMR 4350.
Rob

[greylynx]

I you want to see really big discrepencies, pick up a old 1962 Lyman manual and compare the the grains of powder required for otherwise identical loads.
The differences are quite remarkable.

I think the risk of law suites has been implemented into loads over the years.
I can't see a powder like 4350 changing its characteristics.

[BallCoeff.435]

Lots of things will change the pressure that you get in a chamber compared to some manufacturer's observations (whether or not they're adjusted for legal reasons - that's another discussion entirely)

Some will cancel each other out a little, statistically. But if they all add up to throw the pressure off in one direction or another, then you'll end up wondering what is going on. Reloading numbers too will differ a little from one company's publications to another, and numbers in the same book will change over the years.

If a load is listed as max, then it can be assumed that the pressure is probably getting up there. It may or not be safe to go farther. Use good judgement. If you're at 100 gn of powder 'x', and it's listed as max but you're not getting a sticky bolt yet, it would be a very bad idea to see what would happen if you crammed in 120 gn assuming it would fit.

As already mentioned, the numbers are just a guide. Scientific observation of your own equipment for a particular set of conditions, logical reasoning, and sometimes calculations are the last word.

[foothillsman]

there's alot of causes for the discrepencies. One companies test may be showing pressure spikes that go over the max pressure so stops at let's say 52000 psi. The pressure spikes may be 60000 psi (max). Company #2 tests and gets no pressure spikes and loads max out at 58500 psi with a few reaching 60000 psi. This is the reason you get the discrepincies, but the cause may be chamber/ barrel difference, different primer, different brass, different bullet, powder lot difference, skill or how the person testing the loads interpret what they see and read.

[leo]

My old hornady manual vs new has a huge difference for max load with same powder, same bullet. My guess is LIABILITY to be the main cause. I have a 338mag that loved a particular load 1/2 grain over published max. Mic the case head and no expansion.

[Dick284]

Old vs. new.
you guys know that even lot to lot s of modern prduced powders have different characteristics. So why would 20 or 30 yr old powders be the same?

Also remember that modern pressure trace equiptment is far more relaible than the old copper crusher stuff of yester year. Yes liabilty plays a part, but only if you have relaible test data to support your claims of safe vs. un safe.

Also rember that the 30'06 and 280 Rem are SAAMI standard max operating pressures of 50,000CUP, while the 270Win and 25'06 are 53,00CUP cartridges, are the actions different in modern rifles, no, are the cases made from different raw stock material, no.
Some cartridges will give you a bit more wiggle room because of their historical linige, other not so much.

[WABBIT]

Your looking at IMR4350 data for different bullets,

IMR data is for a 165 Sierra SPBT - Max 60
Nosler data 165 BT - Max 57
Speer #11 data 165 - Max 58
Barnes #4 data 165 - Max 57.5
Hornady #7 data 165 - Max 57

The make of bullet does make a difference, even though the weight is the same.
I have had instances where one bullet is fine and another shows pressure signs using the same charge of identical powder, I had to reduce by over a grain. They all say start at reduced loads and work your way up, the risk is always yours if you go over the max.

Hope this helps.

[billie]

FWIW, Speer #13 is also 58gr max for IMR 4350.

[BallCoeff.435]

Another thing to consider is that you very well could just be shooting better as time goes on, even though you're using progressively faster loads. The faster loads might be a red herring.

Today I shot a 1-cm 5-shot group at 100 meters, which is a good as I've got so far. I think most of that was just very good new equipment that has finally settled down, and relatively hot reloads that seem to be dialed in. But some of it was due to improved confidence and really paying attention to what I was doing. Starting out an hour earlier, with the same batch of reloads, things were all over the place.

[Duramaximos]

Red herring - good word(s)

[378Canuck]

Recommend to get a chrono because you are flying blind. Speed of bullet in manuals and actual vary but the most accurate I've found is the Sierra newer issue. Your best groups will have a connected speed. I don't think changing powders is that important in my opinion. You hear people talk about their best load but when you ask them what speed are your bullets flying at and they don't know. The twist rate of your rifle is designed to handle a certain speed window and if your low groups will be lousy and likewise at the upper end.

[HunterDave]

Thanks everyone for the input.

I decided to not go over the recommended max despite the lack of pressure signs. I had another look at my load work up targets and I'm actually going down .5 gr to 56.5 gr. I'm shooting from a cheap old bench rest (no leadsled) so my aim does move slightly anyway. With 56.5 gr I'm shooting 3 holes together and two holes within an inch with five rounds at 100 yds.

My main objective when I started out was to find a good coyote round for hunting and I think that I have achieved that. Somewhere along the lines I started trying for perfection which I guess reloading can do to you.

Time to take some bullets out and reload them again!

[378Canuck]

It's addictive for sure. Now your dealing with one rifle, imagine finding accurate loads for 6. Record everything.

[Dean2]

Originally Posted by greylynx

I think the risk of law suites has been implemented into loads over the years.
I can't see a powder like 4350 changing its characteristics.

You might think that but todays powders have A LOT more energy than the older versions. I have some war surplus H-4831 that you need to load a lot more grains of to get the desired velocity, than you need to with current production H-4831.

The other difference is pressure rigs have improved dramatically. A lot of the old loads were a long ways over the SAMMI presure limits. I let the individual gun and componenets dictate the max loads. I use loading manuals as a starting point. Just remember velocity=pressure in the same length barrel. If the manual says 3000 fps at 60 grains equals 60,000 psi, and you get to 3000 fps at 57 grains, your combination of chamber, brass, primer, bullet and gun are producing 60,000 psi too. If you go all the way up to the published max you are going to be way over max pressure.

[deanmc]

Originally Posted by Dean2

If the manual says 3000 fps at 60 grains equals 60,000 psi, and you get to 3000 fps at 57 grains, your combination of chamber, brass, primer, bullet and gun are producing 60,000 psi too. If you go all the way up to the published max you are going to be way over max pressure.

Good point. Never thought of it that way.

[elkhunter11]

Just remember velocity=pressure in the same length barrel. If the manual says 3000 fps at 60 grains equals 60,000 psi, and you get to 3000 fps at 57 grains, your combination of chamber, brass, primer, bullet and gun are producing 60,000 psi too.

In theory,your assumption makes sense,but there are other factors that come into play.That is why different manuals list different velocities for identical loads,with identical components,with the same barrel length.Given two rifles with the same length barrels,using identical components.one rifle may safely produce a given velocity,without exceeding the SAAMI pressure for the cartridge, while another rifle may reach the SAAMI pressure for that cartridge,before it achieves that same velocity.It is not simply a matter of adjusting the powder charge until the velocity reaches a given level as some people are assuming..

[Dean2]

Elk

You are exactly correct. In some guns you may well reach max pressure for a particular rifle before hitting the published velocity, even with exactly the same load components as the published loads. This often has to do with barrel length, but in many guns, the max Sammi pressure may be too hot for that particular firearm and the cases will start showing pressure signs before you get to the max pressure. (This can be casued by chamber size, headspace, bolt tolerances, squareness of the action, powder and primer lots and a host of other causes).

A guy needs the combination of a chronograph, so that when he hits max published velocity at the adjusted barrel length he knows to stop, and other indicators. In addition to a chronograph, to work up to max loads safely, a guy must measure head expansion (max .0015 from fired in the same gun with min published load) and watch closely for primer flatttening, primer pocket enlargement (if the pockets get loose after less than 3 firings you are way up in the max pressure zone) and in some cases cratering (many new Remington 700s, becasue of the new bolt design, crater everything so it isn't a reliable indicator in those), as well as marks on the case head, to ensure he doesn't get into trouble with pressue. As you rightly said Elk, it is quite common to hit max load for a particualr gun, well before you get to max published velocities.

If you start blanking primers you are past maximum and need to back up at least .5 grain immediately. When the bolt starts locking up one has gone WAY past a lot of warning sgins and is already in the danger zone.

[elkhunter11]

A guy needs the combination of a chronograph, so that when he hits max published velocity at the adjusted barrel length he knows to stop, and other indicators.

A chronograph is a good tool,but you can safely load without a chronograph.In fact, relying too much on a chronograph to estimate pressures,is not a good idea.Even with identical barrel length,and identical components,the same chamber pressure produced in multiple rifles will not produce the same velocity in each of the rifles.A rough factory barrel can produce more pressure for the same velocity than a lapped aftermarket barrel of the same length.You can achieve more velocity with equal pressure,by coating the bullets with moly or other coatings.

a guy must measure head expansion (max .0015 from fired in the same gun with min published load)

My own feeling is that .0015" is excessive.,My experience has shown that any more than .001" expansion at the web,with a new case,will result in very short case life due to expanded primer pockets.I like to keep web expansion at around .0005" myself.

pocket enlargement (if the pockets get loose after less than 3 firings you are way up in the max pressure zone)

I use 5 firings from a new case,as I have seen data where actual pressure tests showed that at the SAAMI design pressure,most cases will not show excessive expansion within five firings.Cases do work harden after being fired and reformed,so this only applies when starting with new cases.

If you start blanking primers you are past maximum and need to back up at least .5 grain immediately. When the bolt starts locking up one has gone WAY past a lot of warning sgins and is already in the danger zone.

When I see any pressure sign,I immediately back off 2 full grains on the large magnum cases,(RUM,STW etc)and a full grain on the medium size cases(308WIN,30-06 etc.).On the really small cases(223 and smaller)I back off at least 1/2 grain.In most cases,these amounts of powder result in a velocity reduction of about 100fps.

The last thing to be aware of,is that powder burning rates often vary with temperature,so chamber pressures do as well.A load that is developed in cool temperatures,may very well show pressure signs in hot weather.