I'm working on a load for a .375 Wby. First powder was XMR-4350 and it was dog slow. So I switched to IMR-4320. Velocities are getting into the area I feel they should be. But the exterme spread is freakin' ridiculous. I;m using 250 Sierra BT's, Norma brass and Fed. 215's. All charges are weighed on an RCBS beam scale. At 79.0 gr. the spread was 69 fps. At 80.0 gr. it's 89.5 fps. Also, the velocity consistently decreases with subsequent shots. First shot's ALWAYS fastest in the string. I'm shooting 3 or 5 sghot strings and not shooting the barrel hot.

What's a reasonable spread??
What can I do to reduce it??

There are so many things that can affect extreme spread, neck thickness, neck grip on the bullet, appropriate primer, case length, etc, etc, etc. Try these to see if any help:
-Ensure cases are trimmed to same length.
-On loaded rounds, see if the neck diameters are the same or if there is a greater amount of runout.
-Try a standard primer rather than a magnum. (My .375H&H prefers Win LR primers rather than magnums by 3/4" in grouping!)
-Try a different magnum primer.
-Polish your expander ball just so it shines.
Let us know if these work.

Try switching to a std. primer. I have found magnum primers being a bit hot for use w/ powders like 4350. The 210M is stil a warm primer & more than enough to light 80gr of 4320. If your groups are good, I wouldn't get too excited about the extreme spread but it may play havoc w/ longer range groups.

fredj338 and prof242 gave good advice. I would add that most expander buttons are too big and need to be turned down to improve neck tension.

You didn't say whether you were crimping or whether you were loading single shot or loading from the magazine. If you are using the magazine, recoil could be walking the bullets in or out of the case.

I would add that ES is an obsolete yardstick. In the old days, before computers and calculators, ES was popular because it could be quickly calculated with pencil and paper, whereas standard deviation was not something you wanted to tackle with a slide rule. Now there is no excuse not to use standard deviation. If your chrony won't calculate it, use a spreadsheet.

A good rule of thumb is that you need at least 10 shots to calculate SD. If you are shooting 3 shot groups, then combine the velocities from three 3-shot strings, so that you have 9 data points all together. An SD of 1/2% of velocity (about 14 fps) is pretty good, less than 1% (about 28 fps) is decent.

quote:

I would add that ES is an obsolete yardstick. In the old days, before computers and calculators, ES was popular because it could be quickly calculated with pencil and paper, whereas standard deviation was not something you wanted to tackle with a slide rule. Now there is no excuse not to use standard deviation. If your chrony won't calculate it, use a spreadsheet.

A good rule of thumb is that you need at least 10 shots to calculate SD. If you are shooting 3 shot groups, then combine the velocities from three 3-shot strings, so that you have 9 data points all together. An SD of 1/2% of velocity (about 14 fps) is pretty good, less than 1% (about 28 fps) is decent.

Precisely.....and further there's nothing I've seen to show group size is related to SD.....even though logic says it should be.

IMO you're chasing a ghost and will just frustrate yourself here.

quote:

you're chasing a ghost and will just frustrate yourself here.

This seems to hit the proverbial nail squarely.

How does the load group?

If your getting good groups in with an acceptable velocity then I would not bother with SD.

While it's true that ES & SD are not the ultimate measure of a load, acuracy is, it's hard to get an accurate load that is all over the vel. board. I have seen little diff. in accuracy from single digit SD to SD in the low 20s. You will see accuracy diff. at 300yds & beyond if your shot to shot is 80fps though.

All I can tell you is that IMR 4320 is about the worst powder I have ever tested for shot to shot variations in velocity.

I used to shoot it a lot in several 22-250 Remingtons. The groups were good, but when I got a chronograph I could not believe the variation in velocity readings.

Like others have mentioned, it did not seem to hurt the groups any, but you KNOW it had to make a difference in point of impact at longer ranges.

Try another powder. I have not shot a 375 Weatherby, but have had good luck with Varget and/or H 4350 in 375 H&H rifles.

A couple of 375 H&H rifles I have tested have shot much better groups with 300 grain Swift A-Frame bullets than any other.

If groups were the holy grail of hunting loads, I'd agree with that ES has it's limitations.

However, hunting loads, in my opinion, are all about consistency, and an ES of 90 simly indicates there is something wrong.

The first thing I would do is increase neck tension, provided, that is, that the bullet is seated deep enough. It seems fashionable to seat the bullet "out", but the price paid is often inconsistent ignition. The old timers rule of thumb of seating a bullet at least "one caliber" deep was based in fact. FWIW, Dutch.

If the velocity is all over the place you may need to try a different powder or primer. But first were you shooting on a clean bore or a fouled one? If you're cleaning the gun between strings that would cause this. Every time i've shot a clean gun over a chronograph the velocities are eratic but after a few shots they settle in.

Strut10 ----- What kind of Chronograph are you using. Good shooting.

Ever crimp your loads? Try the factory crimp die from LEE... It might help.

Maurice

Thanks for all the help, thus far, fellers!! To answer your questions:

How does the load group?
Technically.....one hole. But I'm shooting 25 yards. So I don't know yet. I usually do my initial chrono'ing and pressure observations at a 25 yard target. A lot less walking to change paper.

What kind of chronograph are you using?
Chrony Beta Master (or Master Beta, as I like to call it)

Ever crimp your loads?
Not these. I had thought about the Lee crimp die. But I can't find one listed for the .375 Wby. Who might carry it?

Lee will make a crimp die for anything if you send them a dummy round with a seated bullet. Give them a call. The factory crimp die works great. Also, changing primers may help as well, but I'd order a crimp die anyway.

quote:

Originally posted by jstevens:
Lee will make a crimp die for anything if you send them a dummy round with a seated bullet. Give them a call.

Thank you for the info. Will call them today.

Hi Strut10

Honestly if the load groups well at 200, 300 yds(if you're shooting that far out) consistantly and you are confident with it, leave it alone.
I say this because I've been chronographing loads since 1979 and one of the first 'oddities' I noticed was the most accurate loads had some of the worst spreads... Go figure.

The chronograph is a tool, like any other tool it can do a lot for you, but sooner or later you will also come to the conclusion that spreads are not that important for accuracy.. Especially in a .375 cal rifle.

Try a low fat diet and a Thigh Master....

quote:

Originally posted by ricciardelli:
Try a low fat diet and a Thigh Master....

Smartass!!

quote:

Originally posted by RDub:
Hi Strut10

Honestly if the load groups well at 200, 300 yds(if you're shooting that far out) consistantly and you are confident with it, leave it alone.
I say this because I've been chronographing loads since 1979 and one of the first 'oddities' I noticed was the most accurate loads had some of the worst spreads... Go figure.

The chronograph is a tool, like any other tool it can do a lot for you, but sooner or later you will also come to the conclusion that spreads are not that important for accuracy.. Especially in a .375 cal rifle.

I definitely will be shooting the gun to 300 yards and probably beyond. I guess it may just be time to stop thinking so much and start shooting. I do, however, already have the dummy round and $$ off to Lee for a crimp die. Can't hurt.

If the accuracy is there, I wouldn't worry about it...

I tested 15 powders in a 6mm Rem with a 75 grain Hornady HP....

By far the most accurate of all of them, was with H 414... the same load also had the widest extreme velocity spread of all 15 of them...

Didn't make sense, but it works... so why should I care....points of impact at 300 yds yielded very tight groups for rock chucks...

I got tired of trying to put logic into reloading some days... if it works, use it and be happy....

There are very few calibers that 4320 will work in, it has always been a poor powder. I would try 4895 and H380 instead. 4895 has always proven a very good powder.
If you want low SD's, black powder is the only one that will do it, smokeless is tough to reduce the SD, more so the larger the case. It has no bearing on accuracy.
I just ran a long string of black 45-70 loads at 200 yd's that gave me an SD of 3 and an ES of 7.3 fps. I had horrible vertical stringing with this load. The load that gave me an SD of 6.9 and an ES of 14.9 gave me a nice round 1" group at 200 yd's.
Extend your range and load for accuracy, forget the SD's. You will waste time and powder trying to get it low and then you will find out it might group like crap!
Forget the velocity also, put the chrono away until you find the most accurate load, then check it just for the heck of it. Fast is not always better and won't make the rifle kill any better if you can't hit what you aim at.

quote:

Originally posted by fredj338:
... If your groups are good, I wouldn't get too excited about the extreme spread but it may play havoc w/ longer range groups.

Hey Strut10, One of the main "benefits(???)" of using a chronograph is the ability for it to create confusion about your Load. Fred's post is right on the nose.

If you want an accurate Load at a specific distance, Develop the Loads at 300yds using the never improved upon Creighton Audette Method and leave the Chronograph at home.

Once you get the Load Developed and sighted in, create your own unique Drop Chart by shooting that Load at the distances you intend to take shots and record the Drop Rate.

Once all that is done, if the Velocity is or Extreme Spread is still of any interest to you(you can always laugh at it), then pull out the chronograph and send a few Loads across it.
---

Chronographs create way more misleading information than any other Reloading Tool. Focus on what is important - the Grouping ability of the Load.

I have an extreme spread problem also. The doctor put me on a diet. roger

O.K. fellers. Thanks for being my online support group.

Advice taken. I'll be off to the bench to fire some 100, 200 & 300 yard targets first chance I get. I'm still taking the chrono to satisfy my curiosity. I just won't let it have any say in what's a keeper load & what ain't. That'll be the paper's job.

quote:

Originally posted by bartsche:
I have an extreme spread problem also. The doctor put me on a diet. roger

Put myself on a slightly modified version of the "Ethiopian Diet Program" back on 15Mar. Went from a few Biscuits either side of 300 to 221 as of this morning.

As the old DIs used to tell us, "Mind over matter - pukes! I don't mind and you don't matter!!!" Helps get the right attitude toward the unnecessary Lard we tote around.

Best of luck with the diet.
---

Hey Strut10, It seems like you have it figured out now. Nothing at all wrong with a chronograph, as long as you ignore it!

quote:

Originally posted by bartsche:
I have an extreme spread problem also. The doctor put me on a diet. roger

Be watchful of those custom diets. They can be hadardous!

I went on the Purina diet once. You go and get large bags of Purine dogfood and simply put chunks in each pocket and eat them when ever you feel hungry.

There was nothing bad about the food but after a long time after I'd lost over a hundred pounds I was in the middle of a road licking my balls and was hit by a car.

Try a good consistant crimp!

Have you checked or deburred the flash hole in the brass? I have read somewhere that a decent sized burr obstructing the spark from the primer could cause inconsistant ignition, therefore inconsistant velocities.

https://forums.accuratereloading.com/eve/forums/a/tpc/f/2511043/m/174107515

Well then explain how the 37.0 grain load with those berger bullets is both the tightest group AND the lowest ES and SD? Not being sarcastic, BUT this one is both. I use my chrono whenever I go to the range to shoot test loads. It provides a wealth of info, especially about pressure, or at least when you've reached max!

How the hell can an ES of 100 fps be accurate at long range? It HAS to vertically string at that distance.

Hey grizz, Got some bad news for you - the chronograph doesn't tell you a thing about Pressure. That really is what a lot of people want to believe, but it just isn't true.

The problem is that it is not "consistent" between rifles chambered for the same cartridge. That variability, along with the fact it only measures velocity, has nothing at all to do with indicating if the Pressure your rifle is experiencing (at a specific velocity) is below, the same as, or above any other barrel using the same cartridge and Load.

So, if you really think a chronograph is indicating a "specific pressure" to you, you have simply been mislead.
---

quote:

Originally posted by Bartche:
Be watchful of those custom diets. They can be hadardous!

I've heard that a good bit(from "fat" buddies ). Don't disagree. Only know the tonnage is going down like Monica on Moscow Bill.

P.S. Stay out of the road!

Hot core, you are of course correct. BUT I did not say you could tell what pressure you were running. What I meant is; when you're working up to maximum load levels, you can see the rate of velocity gain per each increment of powder added. When that gain slows down, or even stops you have reached the pressure limit of that particular load combo. If you're not where you want to be as far as desired velocity levels, it's time to try another powder.

I've used my chrono this way for years to go above max listed in manuals, achiving higher velocity than could have been obtained without the chronograph. Used in conjunction with case head/pressure ring expansion measurements, you can determine you're whithin safe linmits.

Hey grizz, We are now in complete agreement.

About the only time I post on these issues anymore is when I think a Beginner or Rookie can read a post and "possibly" misinterpret it.

You have a good sound method that will serve you well.

Good hunting and clean 1-shot kills.