How much is too much? Powder that is.. 6BR w/ 95gr SMK

[jiwilliams]

How does one know when they are reaching the upper limit of the powder charge for a given load? I'm loading for a 6BR with 95gr SMK at 31gr. I would like to push it a bit to see if I get better accuracy in my 9 twist barrel.

What signs do I look for? What loads have others used?

JW
Houston

 

[jiwilliams]

Guess I should have mentioned that is 31gr of Varget

 

[JHardy]

For good hints, see "Guns of the Week," Week 65,great results with Varget and BIB 95s).

Good luck,
Jim Hardy

 

[Preacher]

if your developing loads with a chronograph look for signs of no velocity increase for a given weight increase.
If your velocity is 2950 fps @ 29 grains, and 3000 fps @ 30 grains, and 31 grains gives you only 3010 your at the top of that combination..... and heading into dangerous territory.........

 

[CatShooter]

if your developing loads with a chronograph look for signs of no velocity increase for a given weight increase.
If your velocity is 2950 fps @ 29 grains, and 3000 fps @ 30 grains, and 31 grains gives you only 3010 your at the top of that combination..... and heading into dangerous territory.........

In 50 years of loading, I have never run into a situation that increasing powder weight didn't increase velocity... even when way over safe loads.

I don't think that is a good indicator of a maximum load.


.

 

[jwv2001]

If you have a chronograph, then Preacher gave you the best advise. If you don't have a chronograph then you have to look for signs on the brass that would indicate that pressures are reaching maximum. This method is not always the most reliable. Things to look for would be cratering or flattening of the primer, a shiny ejector mark on the case head, a stiff lift when you open the bolt with a click at the top of the lift.
If you don't have a chronograph, maybe now is the time to think about buying one.

 

[BoydAllen]

I watch three things, bolt lift, primer cratering, and primer flattening at the corners. This is all predicated on correctly FL sizing,with a die that is a good match for the chamber) every time. I also record temperature and humidity as well as seating depth, charge, powder, bullet,brass mfg, and primer. If you change anything, you need to back off and work up fresh. I had a friend that was shooting a top load in an AE round. When he changed from Federal to Winchester primers, the primer was blown out of the case. There is nothing wrong with Winchester primers, but in his rifle they produced significantly more pressure. One caution, if you have an unexpected hard bolt lift, or anything else that does not seem right, don't scratch your head and try another one. Stop right there.

 

[Forum Boss]

If you have an ejector, look for "ejector wipe" on the base of the brass. That's one of the most obvious signs that you've reach a pressure max.

You should also be measuring the diameter of the brass at the web at the extractor groove itself. All cases will expand some at the web, but if the expansion is excessive you're too hot and you've probably ruined your cases.

An easy "I'm way too hot" test is to bring a regular shell-holder to the range. If the fired brass will NOT comfortably slide into the shell holder without resistance, you're way too hot and should back off.

Other things to look at are primer flattening and primer cratering. The latter can be a little deceptive as there are a number of mechanical reasons why you can get cratering even at a low load.

Work up in 0.2 grain increments and inspect the cases carefully. Also you should be using a chronograph. My feeling is that if you can get the 95s in the 2950-3000 fps range you should be happy.

Remember safety first! Nobody gets an award for fastest bullet if they've trashed their brass or hurt themselves in the process.

 

[jiwilliams]

Thanks guys, those are all good comments.

As to the comment about dimishing velocity increases with more powder, is that a function of not burning all the powder before the bullet exits? or not burning it completely during a point in the pressure curve that contributes to an effective or efficient increase in velocity. Something tells me I'm opening a can of worms.

Let me ask about primer 'cratering' as this is not a term I'm familar with. I've shot a lot of pistol with hot loads and I have experienced primer flow where the primer starts to 'flow' back into the firing pin hole recess,and is often shaved by the slide as it unlocks. Is this flow similar to 'cratering'? The term 'crater' seems to imply something else. Is it flow that builds around the firing pin indentation?

Thanks,

Joe,in windy Houston)

I'm trying to borrow my friends chrono,years ago when I shot lots of pistol I had my own). If I can't get his I will order one from Midway.

 

[CatShooter]

Thanks guys, those are all good comments.

"Something tells me I'm opening a can of worms"

HA!!

As to the comment about dimishing velocity increases with more powder, is that a function of not burning all the powder before the bullet exits? or not burning it completely during a point in the pressure curve that contributes to an effective or efficient increase in velocity.

I have never seen that, nor do I know anyone that has seen that. Powder pressure normally peaks at around 8" to 10" in the barrel... in large cases, it is not completely burned when the bullet leaves the barrel.

Let me ask about primer 'cratering' as this is not a term I'm familar with. I've shot a lot of pistol with hot loads and I have experienced primer flow where the primer starts to 'flow' back into the firing pin hole recess,and is often shaved by the slide as it unlocks. Is this flow similar to 'cratering'? The term 'crater' seems to imply something else. Is it flow that builds around the firing pin indentation?

Cratering is often thought of as a pressure sign, but it is dependent on the firing pin spring.

That is to say, if you have a weak firing pin spring, you will get cratering at low pressures, and even factory loads will look "dangerous", while in fact, they are fine.

Also... oversized pin holes in the bolt will allow the "appearance" of cratering, but it is "Faux" cratering.

It is best to use a little bit of all of the signs - cratering, flattening,at the outside margins), sticky bolt lift, and case face wiping/streaking...

Reading cases for loads is a black art form, but it's all you got!


.


Thanks,

Joe,in windy Houston)

I'm trying to borrow my friends chrono,years ago when I shot lots of pistol I had my own). If I can't get his I will order one from Midway.

 

[jimm]

if your developing loads with a chronograph look for signs of no velocity increase for a given weight increase.
If your velocity is 2950 fps @ 29 grains, and 3000 fps @ 30 grains, and 31 grains gives you only 3010 your at the top of that combination..... and heading into dangerous territory.........

In 50 years of loading, I have never run into a situation that increasing powder weight didn't increase velocity... even when way over safe loads.

I don't think that is a good indicator of a maximum load.


.

50 years of reloading !! Good Grief Charlie Brown , you are a old fart for sure

I guess that goes to show that no matter how long someone does something they "still aint seen it all " . I use a chronograph for all my load development and have seen the circumstance that Preacher described occur over and over . BTW, he didn't say there would be no velocity increase , just that the increase would be marginal.

This seems to be especially true in " overbore " cartridges . Personally , I have seen cases like the 7STW and 7.82 Lazzeroni Warbird come to a practical standstill as far as velocity increase goes and this happens over a spread of 3 or 4 rounds with 3 tenths increase in powder for each round . In the middle of this " node " is where I usually find a low es loading .

jimmba

 

[jiwilliams]

Well.. I got a chrono and headed to the 200yd line at the range.

With the 95SMK seated .010 in
31gr at 3000fps
31.5 at 3040fps and
32gr at 3070fps. Each with Varget and Federal 205 primers and Lapua cases partial neck sized.

The gun HATED all three... The faster the bigger the group.

I had some factory Lapua 105gr ammo. I pulled the bullets to reseat them at different depths. I also loaded some 95gr SMK into the factory case/powder as some of the pulled 105gr bullets were used for other testing.

The result? I don't know what powder Lapua uses.. it weighed in at 29.3gr and put the 95SMK at 2870fps and the 105gr Scenar at 2808fps. However, this the barrel LIKED at both .005 and .010 into the lands. At 200yds I would get 4 rounds touching but often a 5th off an inch or so. I assume it was wind drift or bad bench habits.

So.. I guess the lesson learned is less is more. If I stay in the low 2800fps range I'm golden. I would guess somewhere above 3000fps is another sweet spot but I'm not sure I can get to the fps safely.

Anyway, that is my update.

 

[chino1969]

if your developing loads with a chronograph look for signs of no velocity increase for a given weight increase.
If your velocity is 2950 fps @ 29 grains, and 3000 fps @ 30 grains, and 31 grains gives you only 3010 your at the top of that combination..... and heading into dangerous territory.........

In 50 years of loading, I have never run into a situation that increasing powder weight didn't increase velocity... even when way over safe loads.

I don't think that is a good indicator of a maximum load.


.

50 years of reloading !! Good Grief Charlie Brown , you are a old fart for sure

I guess that goes to show that no matter how long someone does something they "still aint seen it all " . I use a chronograph for all my load development and have seen the circumstance that Preacher described occur over and over . BTW, he didn't say there would be no velocity increase , just that the increase would be marginal.

This seems to be especially true in " overbore " cartridges . Personally , I have seen cases like the 7STW and 7.82 Lazzeroni Warbird come to a practical standstill as far as velocity increase goes and this happens over a spread of 3 or 4 rounds with 3 tenths increase in powder for each round . In the middle of this " node " is where I usually find a low es loading .

jimmba

I've witnessed the same phenomenon with Ackleys. There is a point during load development where an increase in powder charge will yield no velocity increase or change on the target. The way I interpret this is that I am at the 'overbore' point where a resultant powder increase will not result in a velocity increase. Typically with Ackleys, my pet load will be just below this point by a few tenths of a grain.
Chino69

 

[CatShooter]

Catshooter
I have never seen that either.

Usually when I am near over pressure my shots climb extremely fast as does my velocity.

What is being described as seeing pressure is usually how I find my best load.

It might be case specific?
Lynn

Lynn...

Actually, I "have" seen the effect, but it is a statistical anomaly. If you repeat the string, it is gone. It comes from the variances in sampling 5 shot groups.

Here's the problem with that "wives tale".

When you add more powder, you:

1 - Reduce the air space in the case.
2 - Increase the surface area of the burning stuff.

1 + 2 = you generate more gas that goes into less space, and since the "Stuff" is progressive burning, it raises pressure faster.

More pressure pushes harder on the bullet thing - so like all inert masses, the more pressure on it, the more faster it goes - there are NO exception to these basic rules of guns.

If you have a ES of 30, then, on average, you will have a velocity distribution all through the 30fps range, like 3000, 3010, 3015, 3020, 3030. For a mean of 3015.

Then we add .5 grains of powder, and we "should" get a distribution statistics of five rounds to be,maybe) 3030, 3040, 3045, 3050, 3060, for a mean average of 3045, or 30~ish fps faster.

But, statistics also allow a distribution statistics of five rounds to be 3030, 3032, 3031, 3034, 3032, and the mean of these is 3031.8... so we say, "Like WOW man, I only got 16.8 fps change, so therefore... bla bla bla..."

But if you run the same string over again, you will never get the same figures.

I have run strings and come up with five velocities that were all the same, i.e., 3407, 3407, 3407, 3407, 3407... so a ES of "0", and an SD of "0". Do you think I'm dumb enough to think I have discovered the best load in the world - not this puppy. Run the same loads,weighed) in the same cases, and it will come out with an ES and SD just like the rest of the loads.

It is easy to be seduced by those magical numbers that pop out of the chronographs - I have been shooting over chrono's since the late 50s... I believe about 80% of what they say.

The light changes, and your 3560fps load is now 3482, or 3795... Duh!

I had a long talk with Ken Oehler about 7 years ago about the absolute accuracy of chronos - mostly the state of the industry, not his stuff.

It was an interesting conversation - most people absolutely believe the numbers that come out of a chrono like they were numbers coming from the National Bureau of Standards.

But they are not - there is no reasonable or practical way to calibrate a chrono, and they ALL use the same $4 clock chip that is made in some country that you have to boil the water before you drink it. :,

The velocities on the same loads vary by the lighting, where the bullet flies through the window, and what the angle the bullet makes over the windows... yet, most shooters think that 3204 in the little window means absolutely, positively, irrevocably, 3204.000000000 feet per second.

It does NOT - Such beliefs are sheer fantasy.

If you want accuracy, you must have a reliable light source with a positive ON/OFF window - as the current chronos work, the circuit board "senses" a soft change in the screen current, because the bullet shape is soft, and the light source is broad. There is no instantaneous on/off... so there is no absolute point that the chrono thinks the bullet is there - it's kinda like the chrono starts getting a hint that something is changing, then at some point, says, "Self, I think a bullet is going through the gate, so lets start timing."

In order to be absolute, the light sheet must be thin,on the order of 1-ish millimeter), and the shadow cast must turn off and on completely - that is, from full light to full dark when the point of the bullet enters the sensing zone.

None of this is practical in a small unit that you can set up at the range.

---

And I ain't an old fart - I started loading at 11 years old. I'm just medium aged, like fine wine.


.

 

[jimm]

Catshooter you said " And I ain't an old fart - I started loading at 11 years old. I'm just medium aged, like fine wine."


Hey , youre as young as me seriously, the comment was all in fun .

I appreciated your last post on this subject . It encourages me to take a harder look at all the data I gather as I shoot . Time of day and lighting conditions as well as the chrony data . I try to do all testing at the same time of day and light conditions but that is not always possible . From year to year I retest certain load combos in the same month in the hopes of achieving the same sun angle .

I have never felt that any chrony I can afford would be " laboratory " accurate but that if tests were conducted in as near the same conditions as possible I would have some fairly good " rule of thumb " data .

I use a Oehler 35P with 8' screen spacing beginning 10 ft. from muzzle .Female pipe receivers in the ground allow male pipe stands to be placed the same from test to test . Hopefully this also will reduce the error that is inherent . Looking back at the test records , I keep them in binders for each rifle ) I can see where 20 round ladder tests are very similar for the tests previously conducted with the same combinations of powder /bullet/case /seating . Not identical by no means but easily recognizable throughout the test looking at each rounds data.

Finally I think that using the elements of the test ,target marked for each shot numerically, velocity for each shot recorded, powder weight for each shot, and past tests) as a proof read against each other . This requires time and thought and ........a bunch of collected info .

I dont understand the " why " of it but I have too many recorded tests that show velocity spread from shot to shot within a 3 or 4 round node to be reduced as compared to the rounds before that node or after and invariably this is where I find low es and sd and......small groups .My intention is not to be argumentative , simply telling it as I have seen it .

Jim Brown

p.s. I realized that some may misinterpret what I am saying about the velocity " coming practically to a standstill " . What is meant by that is that the spread becomes very small as compared to the rest of the test, usually within 20 fps or so over the entire node .