Preliminary load development charge increments - large magnum rifles

I hope it's a general enough question it can help others as well.

I've never developed up a load for a large magnum rifle. In my case, .338 WM.

The often-stated 1% of total powder charge for increments, it feels, would not be useful here. That would mean approximately .7 grains. In my example, using IMR 4831 and the Speer 200 Hot Cor bullet, the spread is pretty narrow: 70.5 - 74.5 gr IMR 4831.

Additionally, customarily I will start at midpoint unless anecdotal data from shooters suggests otherwise for some reason. I also stop short of the maximum charge. So here, using 1% increments, that would mean starting at 72.5 gr and working up to about 74.0 by 72.5, 73.2, 73.9 and...we're out.

I've seen it said that the 1% is correct for all cartridges - that a 338 has a lot more powder, so .7 grains is 1%, whereas it's a massive step in something like the .17 Hornet. Still, with such a narrow spread, it sure feels inadequate.

Ignoring chrony work for now, how do you guys approach powder charge increments on large magnum rifles?

I'm a even number sorta fellow so I'd start at the bottom , load 5 rounds each 70.5 , 71.5 , 72.5 , 73.5 stopping short of the max unless I see a pattern at the range showing the rifle likes speed . After a visit to the range you should have a idea of the best shooting load then try a half = .5 up and down just to see if it makes any difference . After you get that worked out play with the overall length a bit .
Don't be in a hurry - let the rifle cool down between 5 shoot groups . A couple more trips to the range confirming the best shooting group should do it .
Things to watch out for scope and or hardware movement , developing a flinch , & eye relief is a big one !

I go .5gr on everything then fine tune, (or not) from there.

Quote:

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Originally Posted by Ithaca Gunner

I go .5gr on everything then fine tune, (or not) from there.

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OK, sold. Thanks.

Thanks too, toallmy.

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Originally Posted by toallmy

I'm a even number sorta fellow so I'd start at the bottom , load 5 rounds each 70.5 , 71.5 , 72.5 , 73.5 stopping short of the max unless I see a pattern at the range showing the rifle likes speed . After a visit to the range you should have a idea of the best shooting load then try a half = .5 up and down just to see if it makes any difference . After you get that worked out play with the overall length a bit .
Don't be in a hurry - let the rifle cool down between 5 shoot groups . A couple more trips to the range confirming the best shooting group should do it .
Things to watch out for scope and or hardware movement , developing a flinch , & eye relief is a big one !

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That's what I do also

I load for the best accuracy.
I've usually ended up at about 85% of max. with jacketed and bottle neck cases.
I'll start there with a new powder, and tinker around up & down 1/2 grain at a time, staying below the 95% of max. thresh hold
but more often then not, I end up back at the 85-ish percent.

Your in well plowed ground with the .338.
I'd do some reading/research on various forums and published data rather than try to re-invent the wheel so to speak.

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Originally Posted by Winger Ed.

I load for the best accuracy.
I've usually ended up at about 85% of max. with jacketed and bottle neck cases.
I'll start there with a new powder, and tinker around up & down 1/2 grain at a time, staying below the 95% of max. thresh hold
but more often then not, I end up back at the 85-ish percent.

Your in well plowed ground with the .338.
I'd do some reading/research on various forums and published data rather than try to re-invent the wheel so to speak.

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OK, thanks a lot Ed. So using Lyman as an example, with a range of 66.3-74.0, the difference is 7.7 grains, so you stay below (.95*7.7) + 66.3 or 73.6 grains, and more often than not you tend to circle around 85%, (.85*7.7) + 66.3, or 72.8 grains. Do I have that right?

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Originally Posted by huntinlever

. Do I have that right?

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Yeah, lookee there. You're smarter than you thought.:bigsmyl2:

I've always stayed within the parameters of what a gun & cartridge was designed for.
I figure if I need a .300WinMag for hunting or something---
I'm better off buying one instead of trying to make my own from a .308.
Researching what other hand loaders have done and had good results with gives me good starting and reference points.
It is also certainly cheaper than doing all that research and testing on my own.

Ammo makers tend to take their factory loads up as high/fast as they can get them and still be fairly accurate.
I've noticed they go a little past what is actually the most accurate loading, and get right up to the edge of over pressure.
Most retail customers only look at the advertised speed of their ammo rather than what is most accurate.

Another thing is wear and tear on your guns. They are like any other machine-- they wear out and break eventually.
I look at it like the family car: Sure, it'll go 125 miles an hour.
However; it will probably live & last a lot longer if I keep it under 80.

Not too long ago, I fell into a unfired 70s era Colt rat gun.
I like shooting it, but not at the longer ranges. (the older I get, the less I want to walk down to distant target boards)
I load my .223s for it with 50 or 55 grainers at about 75% of the max for the above reasons.
The target Cong will drag off their wounded,,,, but these still hit hard enough for a clean kill on those little black dots.

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Originally Posted by Winger Ed.

Yeah, lookee there. You're smarter than you thought.:bigsmyl2:

I've always stayed within the parameters of what a gun & cartridge was designed for.
I figure if I need a .300WinMag for hunting or something---
I'm better off buying one instead of trying to make my own from a .308.
Researching what other hand loaders have done and had good results with gives me good starting and reference points.
It is also certainly cheaper than doing all that research and testing on my own.

Ammo makers tend to take their factory loads up as high/fast as they can get them and still be fairly accurate.
I've noticed they go a little past what is actually the most accurate loading, and get right up to the edge of over pressure.
Most retail customers only look at the advertised speed of their ammo rather than what is most accurate.

Another thing is wear and tear on your guns. They are like any other machine-- they wear out and break eventually.
I look at it like the family car: Sure, it'll go 125 miles an hour.
However; it will probably live & last a lot longer if I keep it under 80.

Not too long ago, I fell into a unfired 70s era Colt rat gun.
I like shooting it, but not at the longer ranges. (the older I get, the less I want to walk down to distant target boards)
I load my .223s for it with 50 or 55 grainers at about 75% of the max for the above reasons.
The target Cong will drag off their wounded,,,, but these still hit hard enough for a clean kill on those little black dots.

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You obviously haven't seen me before the first cup of morning coffee. :coffeecom

Excellent post as always and much appreciated Ed. Gives a great working range. Especially given the scarcity of 338 components, anything I can do to get quickly to a good, effective and accurate a hunting load as possible, would be great.

Not to be a tick and get under anyone's skin, but I figure that I select a tool (gun in this case) based on performance applicability to the job at hand.

I won't use a 5000 ft*lb magnum w/ a 400 gr bullet where a 2200 ft*lb w/ a 150 gr bullet cartridge does the job, or using another perspective, I won't use a 3500 fps cartridge to flatten trajectory where shots are 50 yds, so... I load cartridges to their design potential and apply the "right" (that's subjective) cartridge to the job.

I almost always find very accurate jacketed bullet loads at max/near max velocity potential if I tinker a while with powders, seating depth, etc.

As far as charges, on rifle cases of moderate to large volume, what I usually do is:
Select bullet & powder to be used to meet the job at hand, look at max charge applicable and select 5 loads (4 shots each*) each in 2% increments down from max (max, -2, -4, -6, -8%), start somewhere about 0.030 off lands for normal jacketed (provided magazine length makes that possible, if not then load to 0.020-0.030 off magazine), shoot them same day in effort to get same conditions (preferably not a windy day), select the best shooting load and revisit as follows:
Best shooting load of that 5 group test (4 shots each test) repeated with 5 shots, and 1 more 5 shot group with powder charge changed by + & - 1% max powder charge from that 1st 5 shot group charge.
35 bullets and you can usually find something promising.

Then tinker w/ seating depth if you don't quite have what you want, but it is close. Some bullets and guns like 0.005" off rifling to start, some 0.100" off. There are some guidelines based on bullet type within the jacketed and monolithic realm, but there are exceptions to the 'rule' that everyone will find when testing.
If the accuracy doesn't "do it for you", change the powder and repeat.

For much of my hunting loads I stop w/o ever tinkering w/ seating depth, and simply shoot more targets over multiple range sessions w/ same load so I "feel good", but if it's really important, then I would load 5 groups (or More) of 5 shots each and see if it really is as good as I believe. It also helps to Overlay the targets on one another when analyzing so that you see the aggregate. 5 Little groups, with mean impact all 3/4 inch off the aiming point in different directions, isn't much of a 100 yd load.

Round things off for powder charge changes. 2% on 40-60 gr: I use use 1 gr. 2% on 60-80 gr: use 1.5 gr as increment.

New powder I am uneasy about in an application (for a variety of reasons: old can, no direct data, surplus powders, etc.), or a gun w/ a tight bore, I will Add Several increments at the reduced end of things. Maybe down to 20% or more under max listed/estimated. I have started my loading on some things (intended to be investigation into full performance) at 25-30% under max estimated. However, there is no reason in my mind to do this on a factory gun w/ commercial chamber, using reliable data with new commercial powder.

* -- why 4 shot groups to start? I dislike 3 sot groups as there is almost no statistical viability, or room for "dorking" a shot (as I call it when I am at fault), and 5 shots or more on everything uses my bullets up faster.

Rules of thumb for me. I Adjust as I see required at times.

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Originally Posted by TurnipEaterDown

Not to be a tick and get under anyone's skin, but I figure that I select a tool (gun in this case) based on performance applicability to the job at hand.

I won't use a 5000 ft*lb magnum w/ a 400 gr bullet where a 2200 ft*lb w/ a 150 gr bullet cartridge does the job, or using another perspective, I won't use a 3500 fps cartridge to flatten trajectory where shots are 50 yds, so... I load cartridges to their design potential and apply the "right" (that's subjective) cartridge to the job.

I almost always find very accurate jacketed bullet loads at max/near max velocity potential if I tinker a while with powders, seating depth, etc.

As far as charges, on rifle cases of moderate to large volume, what I usually do is:
Select bullet & powder to be used to meet the job at hand, look at max charge applicable and select 5 loads (4 shots each*) each in 2% increments down from max (max, -2, -4, -6, -8%), start somewhere about 0.030 off lands for normal jacketed (provided magazine length makes that possible, if not then load to 0.020-0.030 off magazine), shoot them same day in effort to get same conditions (preferably not a windy day), select the best shooting load and revisit as follows:
Best shooting load of that 5 group test (4 shots each test) repeated with 5 shots, and 1 more 5 shot group with powder charge changed by + & - 1% max powder charge from that 1st 5 shot group charge.
35 bullets and you can usually find something promising.

Then tinker w/ seating depth if you don't quite have what you want, but it is close. Some bullets and guns like 0.005" off rifling to start, some 0.100" off. There are some guidelines based on bullet type within the jacketed and monolithic realm, but there are exceptions to the 'rule' that everyone will find when testing.
If the accuracy doesn't "do it for you", change the powder and repeat.

For much of my hunting loads I stop w/o ever tinkering w/ seating depth, and simply shoot more targets over multiple range sessions w/ same load so I "feel good", but if it's really important, then I would load 5 groups (or More) of 5 shots each and see if it really is as good as I believe. It also helps to Overlay the targets on one another when analyzing so that you see the aggregate. 5 Little groups, with mean impact all 3/4 inch off the aiming point in different directions, isn't much of a 100 yd load.

Round things off for powder charge changes. 2% on 40-60 gr: I use use 1 gr. 2% on 60-80 gr: use 1.5 gr as increment.

New powder I am uneasy about in an application (for a variety of reasons: old can, no direct data, surplus powders, etc.), or a gun w/ a tight bore, I will Add Several increments at the reduced end of things. Maybe down to 20% or more under max listed/estimated. I have started my loading on some things (intended to be investigation into full performance) at 25-30% under max estimated. However, there is no reason in my mind to do this on a factory gun w/ commercial chamber, using reliable data with new commercial powder.

* -- why 4 shot groups to start? I dislike 3 sot groups as there is almost no statistical viability, or room for "dorking" a shot (as I call it when I am at fault), and 5 shots or more on everything uses my bullets up faster.

Rules of thumb for me. I Adjust as I see required at times.

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Wow, fantastic. Thanks for taking the time and the generous wealth if info.

1st run of 5 loads: So, if I have it right, using Lyman and the 200 grain JSP, with a min-max of 66.3-74.0 grains IMR 4831, your first set of 4-shot groups would be: 73.4, 73.5, 73.7, 73.8 and 74.0 grains, right?

2nd:

Quote:

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...repeated with 5 shots, and 1 more 5 shot group with powder charge changed by + & - 1% max powder charge from that 1st 5 shot group charge.

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So, say I find 73.7 is the best. Repeat with 5 shot string. Unclear what you mean by "+ & - 1% max powder charge from that 1st 5 shot group charge..." (man, have to admit Winger Ed nailed it....languages, great. Math and related...."meh."). Do you mean 5 at 73.7, and +/- 1% of 74.0, or 73.9, then above the max by 1%, or 74.1?

A general question of measuring off lands. I think I recall just setting a dummy round and chambering it with the bullet so that the bullet is driven back by whatever the chamber does, then doing the seating depth setback from there by whatever amt. - here, let's say, 0.030". That should obviously work in terms of chambering, and double check for magazine clearance. Is that the process - I believe what I've seen as "jamming the chamber?"

Nope. Your Math is wrong.

2% on your 74 grain max example = 1.5 gr intervals, so: Maybe 74, 72.5, 71, 69.5, 68 is about what I would try. Maybe 74, 72.8, 71.6, 70.4 and 69.2 as your first 5 4 shot groups. Look at the recommended Start charge w/ you combination in a manual and tweak these a little if need be.

Your Second 3 loads at 5 shots should be something like:
Your best load comes at 72.5 the first group of 4, so load groups of 5 at 73.2, 72.5, and 71.8 gr.
See how you cut the interval in half from ~ 2% charge to ~ 1%?

NEVER EXCEED MAX BOOK LOAD is my printed advice. I stick by it most often unless I know quite a bit about the whole affair I am working with.

If I Knew the gun well w/ other loads and that lot of powder I might consider tigntening the spread a little, but I would never go 0.1 grain intervals. 0.1 grain intervals gets you nothing but an overload risk and wasted bullets.
ANY good load on a cartridge on that size should be resistant to group size changes w/ powder charge changes +/- 0.2 grain or so, as w/o that behavior your loads will also most likely go to pot for accuracy with temperature changes of +/- 20° from test point.

Get a Hornady bullet comparator for setting the distance off the lands. It is good for So Much More once you see how it works and get a spread of inserts. I use it to set up my Case Sizing dies for instance.
The other option is to rub a black sharpie all over your DUMMY seated bullet cartridge and find out how long your COL has to be to start seeing rifling wipe the sharpie off when you chamber a DUMMY round. Start seeing land marks, you bullet touches. BTW: don't be freaked if it touches only on 1/2 the lands and/or on one side of the bullet when you first see marks. I have seen a number of barrels that do that, as they are machined poorly on occasion. Might still shoot surprisingly well though w/ some additional jump.

Quote:

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Originally Posted by TurnipEaterDown

Nope. Your Math is wrong.

2% on your 74 grain max example = 1.5 gr intervals, so: Maybe 74, 72.5, 71, 69.5, 68 is about what I would try. Maybe 74, 72.8, 71.6, 70.4 and 69.2 as your first 5 4 shot groups. Look at the recommended Start charge w/ you combination in a manual and tweak these a little if need be.

Your Second 3 loads at 5 shots should be something like:
Your best load comes at 72.5 the first group of 4, so load groups of 5 at 73.2, 72.5, and 71.8 gr.
See how you cut the interval in half from ~ 2% charge to ~ 1%?

NEVER EXCEED MAX BOOK LOAD is my printed advice. I stick by it most often unless I know quite a bit about the whole affair I am working with.

If I Knew the gun well w/ other loads and that lot of powder I might consider tigntening the spread a little, but I would never go 0.1 grain intervals. 0.1 grain intervals gets you nothing but an overload risk and wasted bullets.
ANY good load on a cartridge on that size should be resistant to group size changes w/ powder charge changes +/- 0.2 grain or so, as w/o that behavior your loads will also most likely go to pot for accuracy with temperature changes of +/- 20° from test point.

Get a Hornady bullet comparator for setting the distance off the lands. It is good for So Much More once you see how it works and get a spread of inserts. I use it to set up my Case Sizing dies for instance.
The other option is to rub a black sharpie all over your DUMMY seated bullet cartridge and find out how long your COL has to be to start seeing rifling wipe the sharpie off when you chamber a DUMMY round. Start seeing land marks, you bullet touches. BTW: don't be freaked if it touches only on 1/2 the lands and/or on one side of the bullet when you first see marks. I have seen a number of barrels that do that, as they are machined poorly on occasion. Might still shoot surprisingly well though w/ some additional jump.

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OK, thanks. I'm an idiot as I know the "standard" of 1% on a max of 74 = .74 grain steps. Face palm, blush.

I suspected you wouldn't have suggested overload, and obviously I have to do some homework (with Speer using this bullet and going up to 74.5, but with Speer's use of CCI and not the Rem 9 1/2's of Lyman's and also what I have), I thought there might be some play there but obviously I'm wrong. Thanks for the clarity and walking me through it.

On the comparator (I saw here - Sinclair, I think, but I suspect same idea?: https://www.youtube.com/watch?v=azv1dxKQNvA), I've seen some of this, but I got the RCBS precision mic I was using for shoulder setback (I see Forster standards used, too - https://youtu.be/H_T7gteAlkc?t=106). I see there's a second function for bullet seating but I've also seen some say they had less success for this function. Afraid I'm budgeted out for the time being but thanks again, and I'll cart it for future possibility.

No reason for feeling bad at all: humans are bound to err I think I heard before... :)

In any event, as long as you're on a better track, that was the intent, yes? Was for me.

Primer change from load manual listing.
Yes, it can make a difference in pressure, as others on here have shown previously and again recently in threads, and as I have seen in pressure data from a gun I once had as well.

That said, rifle cartridge like the 338 WM and Extruded (stick) powder, I would probably use what I have on hand as long as it was the same type. i.e. If the manual uses a CCI std lg rifle, I would probably switch to another std lg rifle that I had. If the manual uses a CCI Magnum lg rifle, I would probably switch to another Magnum lg rifle that I had, or me being me I would use a standard large rifle and make sure I tested it in cold weather if I intended to hunt in cold weather.

Larger cases, heavier deterrent coatings for burn rate control often benefit from "hotter" primers, and may Really be advisable when the bore size is reduced on a case of "larger" capacity, but I have used standard WLR on 70 grain charges in magnum cases just fine. So, it all depends.
Remember that the F215 (magnum lg rifle) was developed for the 378 Weatherby. Federal didn't have a LR Mag primer before that, and many belted magnums were around before the 378 WM, and people used them frequently.

Comparator:
If you have comparable tools, hey, use them for what they do. Enjoy. No snark. Don't spend money you need for something else.
I just like my Stoney Point (Hornady bout the rights maybe a decade ago), and so I just made comment on that style and would recommend if the person reading the reply didn't have one. It really is a handy tool, but if you have something else that does the job, by all means just get to it w/ what you have! :)

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Originally Posted by huntinlever

anything I can do to get quickly to a good, effective and accurate a hunting load as possible, would be great.

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There's folks here that can help a lot more than I can with their scientific ways & all.
I'm glad to be able to post the redneck version of things and pass on a little bit of what I call 'geezer wisdom'.
Such as: Don't bet on slow horses, and don't squat while wearing spurs.

Quote:

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Originally Posted by Winger Ed.

There's folks here that can help a lot more than I can with their scientific ways & all.
I'm glad to be able to post the redneck version of things and pass on a little bit of what I call 'geezer wisdom'.
Such as: Don't bet on slow horses, and don't squat while wearing spurs.

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I got geezer down, just waiting on the wisdom part. The last advice, taken to heart.

Quote:

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Originally Posted by TurnipEaterDown

No reason for feeling bad at all: humans are bound to err I think I heard before... :)

In any event, as long as you're on a better track, that was the intent, yes? Was for me.

Primer change from load manual listing.
Yes, it can make a difference in pressure, as others on here have shown previously and again recently in threads, and as I have seen in pressure data from a gun I once had as well.

That said, rifle cartridge like the 338 WM and Extruded (stick) powder, I would probably use what I have on hand as long as it was the same type. i.e. If the manual uses a CCI std lg rifle, I would probably switch to another std lg rifle that I had. If the manual uses a CCI Magnum lg rifle, I would probably switch to another Magnum lg rifle that I had, or me being me I would use a standard large rifle and make sure I tested it in cold weather if I intended to hunt in cold weather.

Larger cases, heavier deterrent coatings for burn rate control often benefit from "hotter" primers, and may Really be advisable when the bore size is reduced on a case of "larger" capacity, but I have used standard WLR on 70 grain charges in magnum cases just fine. So, it all depends.
Remember that the F215 (magnum lg rifle) was developed for the 378 Weatherby. Federal didn't have a LR Mag primer before that, and many belted magnums were around before the 378 WM, and people used them frequently.

Comparator:
If you have comparable tools, hey, use them for what they do. Enjoy. No snark. Don't spend money you need for something else.
I just like my Stoney Point (Hornady bout the rights maybe a decade ago), and so I just made comment on that style and would recommend if the person reading the reply didn't have one. It really is a handy tool, but if you have something else that does the job, by all means just get to it w/ what you have! :)

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OK, many thanks again. Feeling pretty solid on shoulder setback now (bumped it back 0.002"), and am keeping the SAAMI COAL of 3.340 until load development is pretty solid, if I even need it at that point.

On a case that size, 0.3 grain increments starting from the mid point to about 5% over max or a full case, whichever comes first. For a monster like a Rigby or Lapua, half a grain. For about .223 up to .30-06, 0.2. For peewees like Hornets or Fireballs, I'll probably start with 0.2, but I'll go in somewhat resigned to the fact that they tend to be fussy little beeches that want it a single tenth at a time.

I don't do groups with multiples of the same charge to start. I do singles of each charge over the chrono all at one or two targets. If I get signs that the load is becoming too hot, I'll stop and pull the remaining bullets. What I'm looking for is velocity plateaus of 3-5 rounds where neither the speed nor shot placement significantly changes. Next trip to the range, I'll bring test batches of about 10 rounds loaded right in the middle of those flat spots. If they group, I'm done.