is it a must to work up new load when changing powder lots

[Metal god]

I just bought some new IMR 4895 . I first was thinking I should work up a new load using the new powder lot . I went to IMRs online load data and it turns out my best load ( accuracy ) is 3 tenths below there minimum .

175gr smk
Win lr primer
WCC case
40.7gr IMR 4895

So I loaded 50 up and went to the range . All seemed fine and they shot real accurate . They did seem to have a bit more kick/pop to them but that could just be me . No pressure signs at all . I had another load with me I wanted to test but forgot the chrono so I did not shoot the new load or get to see what the new powder was getting in terms of velocity .

The one thing I believe I noticed was each piece of powder was longer or at least what appeared to be on average they seemed longer . More like 4064 but I did not pull the old lot out to compare .

Should I always work up a new load even when working with the same powder ? I can see why you should if the load is at max or over . More to the point and when my load is on the low to mid charge range ?

On a side note and unrelated .A couple weeks ago I neck sized only for the first time ( old lot of powder ) 3 things I noticed . 10 tighter fit in chamber . there was slight resistance when closing bolt . 2) sticky bolt when at the top of the cam 3) they were not as accurate as my FL sized loads .

Feel free to comment on this if you like . I did not want to start a different thread on the subject

[jwrowland77]

I've always gone by if my load is on the low end, I don't do a new workup for different lot.

Saying that though, I have several loads that are near max per the IMR website, and when I get a different lot of powder, I generally drop it down a couple grains and work it back up. Some powders are more consistent lot to lot than other.

Varget is one of those powders, I'd workup the load every new lot. I saw a lady ruin her bolt and firing pin at a match after 3 sighters and had to sit out for the day, because she didn't workup the new lot of Varget.

[Bart B.]

I never have and neither does Sierra Bullets. Our accuracy with different bullet weights didn't change with powder lots but muzzle velocity did a little bit. Our loads were usually near maximum so a different lot of powder for a given charge weight didn't matter much.

A Lake City Arsenal ballistic engineer once told me they usually started each lot of M118 7.62 match ammo with the same charge weight then adjusted it to meet velocity & pressure specs (2550 +/- 30 fps at 78 feet, about 50K cup) so sight dope on rifles would be very close. Accuracy change across a 1 grain spread on charge weight was insignificant. Accuracy spec was 3.5" mean radius for 250+ shot test groups which produced about 12" to 13" extreme spread.

This is with IMR powders. I don't know about others which may not be a uniform across powder lots.

[James K]

Canister grade powder (the kind you and I buy in small containers) is very carefully controlled by the manufacturer to be sure a new lot gives exactly the same performance as all previous lots.* I never worked up new loads for a new lot and I don't know anyone who does.

*That is a bit simplified. In fact, when a powder maker works up a new batch of powder, which could be in the tons, it is tested for performance. If, more by coincidence than intent, it happens to match perfectly with the specs for canister sales, it is set aside for that purpose. If it doesn't match canister specs, it is sold to ammunition companies or a government contractor; they work up loads to their requirements.

Jim

[Metal god]

Thanks guys . There is something I noticed couple months ago and after looking at IMRs website I remember the fact my load is very low . My Sierra book has 41.5gr as max . The fact I was .8gr below that was telling me as was close to max load and there was no need to find another node . Now I look at IMRs load data and I'm below minimum and there max is almost 5gr higher . That kinda makes me mad . I never went over 42.5gr because Sierra's book indicates anything over that would be getting way over max . IMR seems to think your really still on the low side at 42.5gr .

I was at the range last week talking to a guy shooting the same combo . 175gr smk and 4895 . I asked what his charge was and he said 44gr I thought holy cow he is WAY over max . Turns out he was still a grain below according to IMR .

Going up in .5 increments from 40gr to 42.5 my 40.7gr load by far shot best . I'm getting 2540fps from a 24" barrel with that load . I'm thinking there's another node out there for me to hit at the 43 t0 44.5gr area maybe . I , like a lot of people am looking for that 1000yd load . 2540fps is right on the edge so I'd like to find a little hotter load that shoots 1/2 moa at 100yds like my 40.7grain load does .

When shooting those 42gr and 42.5gr loads . the rifle seemed fine and I did not see any pressure issues . So I think I'm going to kick it up a bit and start at 42 and work up to 44.5 and see what happens . what do you guys think about that ? Or should I even bother seeing how I have a good load already ? .

[jwrowland77]

I assume your loading for .308?

1000yd load with 175gr SMK, you'll need around 2650. When I initially started trying to find a 1000yd load, I started with IMR 4895, it just didn't work for me. I ended switching to 2000-MR to get the velocity I wanted/needed as well as accuracy to hit 1000 and stay super sonic with 175's. IMR 4064 is another powder that has gotten me the velocity I needed as well. The 2000-MR is getting me around 2760fps with 175gr SMK and the IMR 4064 is getting me 2680fps using 175's. At .02 off the lands.

I hope it works for you though.

[Metal god]

I assume your loading for .308?

oops yeah sorry

I have a couple lbs of PP 2000-MR but never really gave it a chance . I've not been loading long ( close to a year ) all bottle neck cartridges . 223/5.56 and 308 . 2000-MR was one of the first powders I could get and I loaded it a little but before I really gave it a chance some 4895 and 4064 came available and I have not looked back . Maybe I'll pull that out and give it another try .

For some reason I've not had great luck with 4064 and 175gr snk . Looking back at my notes . My best load was 41.5gr with a .8 moa 5 shot group . I had a .9 moa group at 42.5gr . That's where I stopped because the book says I'm at max . Turns out once again I may have a couple more gr to work with . That 42.5gr load had a five shot average velocity of 2632fps and a SD of 19 . Thats not to bad , maybe I can play with seating depth and get that group a little smaller .

[4runnerman]

I never have done it. My loads are all in the mid-range so I am safe either way. If I am starting a new 8 lb can and loading for a match,I will go shoot a few just to be sure,but still have seen no difference in POI. I do not check with Crony once my load has been developed either. If I switch powder or primer,then I will.

[Sport45]

Originally Posted by 4runnerman

I will go shoot a few just to be sure,but still have seen no difference in POI.

Same here. Just a few to verify then I load as many as I want.

[jwrowland77]

Originally Posted by Metal god

oops yeah sorry



I have a couple lbs of PP 2000-MR but never really gave it a chance . I've not been loading long ( close to a year ) all bottle neck cartridges . 223/5.56 and 308 . 2000-MR was one of the first powders I could get and I loaded it a little but before I really gave it a chance some 4895 and 4064 came available and I have not looked back . Maybe I'll pull that out and give it another try .



For some reason I've not had great luck with 4064 and 175gr snk . Looking back at my notes . My best load was 41.5gr with a .8 moa 5 shot group . I had a .9 moa group at 42.5gr . That's where I stopped because the book says I'm at max . Turns out once again I may have a couple more gr to work with . That 42.5gr load had a five shot average velocity of 2632fps and a SD of 19 . Thats not to bad , maybe I can play with seating depth and get that group a little smaller .

I will say, that the 2000-MR does not start to really perform until near max or at max (47.7). As a matter a fact, I just tested some new loads yesterday with it.

Yeah definitely use the IMR powder site for 4064. The match load I had that used 4064, was 44.5C. The powder site has it going all the way to 45.6C.

Yeah, if the powder site uses the bullet I'm going to use, I always use the website data. It's a bit on the hotter side of things. If I want a tamer load, I look in one of my manuals.

[Bart B.]

One think most reloaders don't realize is how a given source determines pressure and velocity. There is no standard, all sorts of ways with huge variables are out there. The industry standard is seldom what their numbers are based on.

SAAMI specs require a precision dimensioned pressure and velocity barrel mounted in a fixed receiver that moves backwards in recoil zero amount. And it's got the same pressure measuring system (strain gauge or copper crusher; both with tight tolerances) for each cartridge. There's even a standard method of positioning ammo to test, picking up a cartridge, handling then loading it so the powder's positioned the same way for each shot; called the "SAAMI twist." So their "ruler" that measures stuff is the same for each cartridge. Few folks outside of some commercial ammo makers use that.

The popular practice is to hold the rifle against ones shoulder, shoot a bullet through a chronograph, then look at the primer and/or case for pressure indicators they use. Rarely will two people shooting the same rifle and ammo log identical results. This is the "rubber" ruler that's used for the vast majority of published data. So don't take it with a grain of salt; a 10-pound sack of salt is more realistic.

A close relative of this popular system is the way a given load is tested for accuracy by many people. Several accuracy-determining methods are used and a given set of shot groups will result in a wide range of accuracy lables by the masses evaluating them.

[jwrowland77]

Originally Posted by Bart B.

There's even a standard method of positioning ammo to test, picking up a cartridge, handling then loading it so the powder's positioned the same way for each shot;

+1, this can make a difference in the way it performs.

This is why I like my compressed load for match. It's packed in there. No movement. It gives me the most consistency from shot to shot. It's the most accurate in my rifle anyway.

[Real Gun]

One thing I learned is that when starting a new container, assuming nothing, I better recheck my powder drop weights. My PowerPro 300-MP was light. I suppose that could just be the difference in density between the last of one container and the decant from the new container.

[Unclenick]

Per all the above, several considerations:

IMR has apparently changed their manufacturing process up at Valleyfield. From communications with Hodgdon described on another board, I gather the original process is now considered too expensive, so IMR powder appearance may be expected to change. I just hope the performance isn't changed much with it, as geometry affects stick powder characteristics. I also heard the SR line of powders was being discontinued. This is all second hand information, at the moment. I haven't had time to verify it.

Canister powders generally vary in burn rate ±3%, where ±10% seems to be more typical for bulk grade powders, with occasional wilder excursions. Bulk powder that has too extreme a burn rate difference can be surplused out, so you really need to mind your load workups with surplus powder more than with any other.

Some 1990's era Varget was an exception to the canister grade tolerance range, with more substantial variation by lot reported. I believe Hodgdon upgraded their QC circa 2000, and now has that under control.

±3% variation will cause pressure to vary about 5%-6% in typical rifle chamberings and powders. In the .308 Winchester, it's approximately like adding 1.7% more or less powder. Less than a grain. Rifle cartridge proof loads average about 140% of MAP, so ±3% of burn rate is not enough difference to damage a gun. Indeed, as Bart points out it may not even be enough to spoil accuracy, though it can move you off the center of a sweet spot so you no longer have quite as much charge weight forgiveness at one end of the load range of the other.

The tighter canister grade burn rate tolerance is needed by handloaders to keep load manual data valid, while ammunition makers can use their pressure test gear to adjust charge weight for the wider bulk powder tolerance and don't have to stick to particular charge weight recipes. Blending of bulk product with held back faster or slower lots of the same type powder is used to control canister grade powder burn rate tolerance. That makes canister grade powder more expensive than bulk grade. Saving cost is why manufacturers, except some smaller operations, normally use bulk grade powder. Sometimes exceptions are made for match grade ammo.

Despite the tight burn rate tolerance, canister grade powders can have significant bulk density variation. Only Western Powders publishes this data. If you look through their Accurate powder products on their web site, you see bulk density vary from ±2.2% to ±5.6% for different products. You can see how, if someone is depending on a volumetric approach to charging cases, as benchrest shooters often do and as Lee's VMD method does, that the combination of the bulk density variation and the ±3% burn rate tolerance could raise pressure close to 25%, with is almost a proof load if the starting point was a maximum load of the original powder lot. Someone loading warmer than SAAMI standard MAP to begin with could be carried into the proof range pretty easily.

.308 Winchester has more variability in the available commercial and military case volumes, combined, than anything except the commercial case volume variation in .300 Winchester Magnum. If you look at Sierra's data, they use a Federal case which, IME, typically has about 45.5 grains of water capacity under the 175 grain SMK. Hodgdon's data uses a Winchester case, which, for the lots I have, runs about 47.4 grains of water capacity. This makes a difference of nearly 10% in peak pressure for the same load in QuickLOAD, and corresponds to about 1.2 grains difference in charge weight of Varget under that bullet. This explains part of the difference with the Sierra load. The other part is that Hodgdon tests their loads to SAAMI standards in a pressure/velocity gun on a universal receiver, while Sierra works theirs up by the rubber standard Bart described in an off-the-shelf Savage 12V-SS. I believe, because of the rubber standard's vagaries, Sierra allows an extra margin of safety. That means their load ranges tend to be a bit low.


Back OT

To the OP's question, I would always work loads back up if I dispensed by volume exclusively. I always work a load back up if its for a different gun. If I were changing two variables at once, say, both powder lot number and primer, or also the case or the bullet, I work back up. There are a few exceptions for very long standing standard loads I can think of, but none involving maximum loads come to mind. I probably won't trust the new process IMR powders completely until I've wrung them out, so I'll work back up with them as they appear.

Pressure sign work-ups are generally handled in 2% steps, anyway, so it's just six rounds to go from -10% to a maximum charge, using the rubber standard to scan for pressure signs. So it's not a big deal to add that step.

In all the powder I've seen except surplus bulk powder, a shortcut is possible if you have a chronograph. As you run low on that first lot of powder, keep back just enough to load 15 rounds with the published minimum load. Load 12 at that same charge weight with your new lot of powder. Primers, cases, and bullets and loading method are presumed to be the same.

Take those rounds to the range together with the chronograph. Fire three of the old rounds as fouling shots. Then measure velocities on the remaining 24 rounds, alternating between loads: one from the old lot, then one from the new lot, so all the old lot cartridges are odd numbered shots, and all the new lot loads are the even numbered shots. This is so barrel temperature, lighting condition changes, etc., have their influences averaged out. Then find the average velocities of the odd shots and the average of the even shots. Use the following formula to find the charge of new powder lot that produces the same velocity as the old:

Woldload = original best accuracy load charge weight with the old lot of powder.
Vminold = Average Velocity of OLD lot of same type powder with manual Minimum Charge Weight.
Vminnew = Average Velocity of NEW lot of same type powder with the same manual Minimum Charge Weight.
Woldload × (Vminold /

Vminnew) = Same Velocity charge weight of new powder.

The idea here is that since the powder types are the same for both lots, they'll have proportional fps/grain relationships. This formula would not work very well with two different powder types, even if you knew you were not exceeding peak pressure with either. That's because the different types will not likely produce the same barrel time at the same velocity, and barrel time is what synchronizes you with muzzle deflection to find a sweet spot. As long as it's the same powder type, with the same shape burn curve, the above formula will get you very close, though. Within a tenth of a grain or two of producing the same barrel time with the new powder lot as your old lot did.

[Brian Pfleuger]

I just saw an interesting thing happen when changing lots of W748.

Unfortunately, I changed from neck sizing in Lee collet dies only to collet sizing and Redding body sizing with a 0.0015" shoulder bump at the same time I switched powder.

With no other changes, the load went from 1/2-3/4 MOA to 1.5MOA.

Sadly, I am out of both the old lot and that particular bullet so there'll be no experimenting to figure it out.

[Bart B.]

With most cartridges' bullet weights, best accuracy happens when the pressure curve shape is most repeatable. That ensures the bullet leaves in the same small range of muzzle velocities and muzzle angle. Anything that changes that pressure curve shape too much and it's no longer repeatable from shot to shot will see accuracy degrade.

[Metal god]

Well now that's some interesting reading there Unclenick

So I just loaded up 10rds of the new lot to the same specs as I was shooting before . That is very close to IMRs minimum charge 40.7gr . I did this and only 10 because I only have 10 or 15 rnds left from the old lot loaded and I'm shooting tomorrow ( for some of you today ) Did not have the time to do all the case prep and what not so the test will be with 10 shot lots with each lot loaded to the exact same specs including cases , primer and bullets . I also have the load workup from 42.5gr to 44.5gr . I will only start on those if the new lot of powder shoots the same as the old one .

If my old lot was getting 2550fps how much of an increase of velocity Would the new powder need to be to indicate I need to start over on load development ? 20 40 60 fps ???

I'll check this thread in the morning and again while at the range . I'll be there at 8am pacific standard time and these test will be the first thing I do . I'll try to update this thread in real-ish time while at the range if anyone is interested

[mehavey]

Repost from earlier post:
http://thefiringline.com/forums/show...ght=powder+lot
~~~~~~~~~
Just for grins, I ran a Lot# Change series today [four years ago] (weighing the cases this time) to see if velocity differences would be noticeable. (The lots were only several months apart)

Last Week @74DegrF:
Lot#255 (my old Lot of IMR4831) gave me 2,530fps last week using 53.3gr

This Week @73DegrF
Lot#255 gave me 2,527fps
Lot#265 (New Lot) produced 2,457fps (with unsually good StdDev)



Quite a difference for those who operate at/near MAX loads.
Be forewarned (again) to step things down before you step them back up.
~~~~~~~~~~~~~

...went downstairs and ran [a volume] comparison test. (No need to convert to specific gravity, just ratio the relative densities).

Old Lot#255: 15.18gr/cc
New Lot#265: 14.82gr/cc

Load Density Ratio: New Lot/Old Lot = 0.976
Therefore Predicted Velocity of New Lot (relative to Old Lot) = 0.976 x Velocity of Old Lot

Predicted Velocity Lot# 265 = 2,466fps
Actual.... Velocity Lot# 265 = 2,457fps

Interesting Indeed.

BUT... This would seem to apply were I throwing volumes, not weights. Since I was weighing charges, the New Lot#265 would occupy more case volume for the same weight -- nominally increasing pressures (ergo increasing velocity) all other things being equal.

[Metal god]

Range just went hot . I'll shoot my fouling shots , let barrel cool then shoot five shots of each lot . Update in a few

[Metal god]

Ok first five shots of each IMR 4895 lot

Old lot
2571
2591
2574
2564
2550

New lot
2532
2528
2515
2517
2527

So far the new lot seems slower but more consistent . Next update of final 5 shots of each lot coming soon . Barrel got pretty hot shooting 10 shots in a row . Letting it cool now

[Jim Watson]

Metal god is working at the low end of the load range and "working up" with a new can of powder is not needed for any of the usual Internet Cautionary Recommendations. As said, there might be some tweaking to maintain accuracy.

In fact, when a powder maker works up a new batch of powder, which could be in the tons, it is tested for performance. If, more by coincidence than intent, it happens to match perfectly with the specs for canister sales, it is set aside for that purpose. If it doesn't match canister specs, it is sold to ammunition companies or a government contractor; they work up loads to their requirements.

This is pretty much my understanding of the process.
We read so much about "special orders" and "blended" powders in factory loads that We Commoners cannot hope to duplicate that we give them way more credit than is due.

Phil Sharpe said that in WWII, a powder lot was a railcar load, 20-30 tons. That was done for consistency's sake at the ammo plant, the powder mill was holding to the same specifications for much longer production runs but you could not be sure of getting consecutive carloads. So you had better check the load and tweak if necessary.

Despite the tight burn rate tolerance, canister grade powders can have significant bulk density variation.

A friend ran into that yesterday. He dug a can of powder out of the closet and found it noticeably denser than what he had been using. I said to adjust to the same weight, even though the same volume at higher density was still a handbook load.

[Metal god]

Second set of five shot strings . I alternated shots from lot to lot in both sets of strings

Old lot
2569
2600
2573
2606
2568

New lot
2560
2561
2556
2534
2526

It seems clear that the new lot is a tad slower an more consistent .

The fact the new powder is slower I will go ahead with the other load work up

[Bart B.]

Metal god, I don't think 5-shot tests are good enough to see meaningful muzzle velocity spread differences. The old lot had a 41 fps spread and the new one 17 fps.

Depending on how each cartridge was handled from its resting place to in the chamber, half that spread could be caused by that alone. The varaibles in how hard you held the rifle to your sholder could easily be the other half. Which means that some of those variables will cancel each other out and the others will add up in one direction.

That aside, the new lot may well be more uniform in pressure curves shapes and muzzle velocity. If you test slung up in prone with the rifle resting on bags under the fore end and stock toe, you may well get lower velocity spreads that when shooting the rifle resting on something atop a bench while you're setting at it. I sure do.

[Metal god]

It was 10 shots in total of each lot . I did them in 2 seperate strings because I did not want to heat my barrel with a 20 shot string . Both strings were started with a barrel temp of 70' .

I loaded one round at a time and both lots have been in the same box since last night to chamber . They had the exact same handling for the last 14 hours .

As for how I hold the rifle . I'm sure I'm not the most consistent but did make the effort . Those 2 shots that were in the 2600 area were out of all norms for that load . Till then I had never had this charge shoot that fast .

[Metal god]

Once again Bart your right . I just did 2 five shot test holding the rifle different . First test was barely touching the rifle and letting it almost free recoil . Second was holding it tight in to my shoulder I should add all these test are from a bench with bi-pod and rear bag .

1st test very little pressure on rifle
2551
2555
2559
2552
2565

2nd test holding rifle tight into shoulder
2517
2582
2568
2552
2568

The second test I did not let the barrel cool all the way down . I did let it cool just not the 30 min I had been doing .

That first test and letting the rifle recoil back on its own was the most consistent and lowest ES & SD I've ever had . Hmm never thought to just let the rifle go and let it do all the work .