I got a 'how come' question. I'm trying to get 2400 fps with a 160 gr RN in a m/96 Swede with 29" barrel. I want to get close to the original Norma load designed for the rifle. I got 2370 average with 37 gr IMR 4350 and thought that if I bumped it up 1/2 gr I should see a small increase in velocity. WRONG! Velocity actually lowered to 2200 over 20 shots. How come?? Probably a very good explanation but I am clueless at the moment. Halp! Gary

gsmithp,

I have noted this when I approached, or went over, maximum loads with certain powders. I mostly had signs of pressure problems when this happened. Good-luck...BCB

The paradox of increased charges producing kower velocities is long-known to experimenters. But I don't have any explanation for WHY or HOW it happens. One theory (how sound a theory? I don't have a clue) is that the overly increased load density actually reduces the efficiency of the ignition by the primer, so that less of the larger charge actually burns � less, also, than the lower charge. If this is what happens, then obviously the lower volume of powder gas produced could be why a larger charge sometimes produces less velocity.

It's good to see you back Ken. Hope all is well with you and everything is improving.

Steve

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Every man dies, but not every man really lives!!

Yes, I have seen this on many occasions too. Two things come to mind:
1. You have exceeded the max. load for that powder.
2. You need to go to the next faster burn rate powder if you expect improvement, you may not get it, but more or slower powder won't help.
Just one more reason for a chronograph for load development!

Ken, so good to see you up and posting a little! Hope things are progressing well for you. Miss your excellent advise and "style"!

BP

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Speak softly, but carry a big stick!

If you were anywhere near a maximum load, I'd be agreeing with the other posts. As you get near max, you get less and less gain as you add powder, and you can reach a point that you get less. I'll be doggoned if I understand the physics of that.

But you are far below a maximum load. I use 44 grains XMR4350 behind a 140 grainer, for 2750 fps. You're 7 grains below that.

I wonder if it is possible that gun position has anything to do with it? With light loads, it does make a difference whether you start from a muzzle down or a muzzle up position, because in one case, most of your powder will end up at the neck, and in the other it will be at the head. (Never did figure out how cartridges have necks at one end, and heads at the other....)

BTW, isn't the Swede a lovely machine?

37.5 grains of IMR 4350 shouldn't be an over load. Max swede pressures would be somewhere in the area of 42.0 grains. This would exceed your desired velocity in a 29" barrel.

I believe Ken is on the right track with this. Perhaps increasing your crimp or selecting a different primer would help.

Sierra lists 43.1 grains AA4350 and 43.3 grains of H4350 as their top end recommendation. These produced 2400 FPS in a M94 carbine (18" barrel.)

43.0 grains of H4831 should produce 2400 fps in a M96.

Note: Sierra loads at 3.062" OAL and a Hornady would be roughly 3.0" OAL. I would reduce the charge a bit for the Hornady and work up. Sierra used a Rem 9 1/2 primer in their testing.

Alliant suggests 45.0 gr. of RE-19 and 47.0 gr. of RE-22 as top end for the Hornady 160. Both of these loads would also exceed your desired velocity in a 29" barrel.

[This message has been edited by Scott H (edited 08-29-2001).]

Thanks to everyone for your thoughts on my load problem. A couple other little factoids may help in understanding what's going on is I'm using Lapua brass which requires a reduction in powder volume. I figured I was covering that with the 37 gr starting load but maybe that was the max load for that brass and the half grain extra pushed it over? Pretty slow velocity for a max load though, isn't it? Also the Rem 9 1/2 primers I used showed signs of high pressure by the firing pin dent being pushed back out level again leaving just the ring around the edge. A couple pin indents blew out leaving a hole and gas escaping thru the bolt. I'm thinking the Lapua brass is much smaller inside than I thought or the Rem primers may be too soft. I am also using the Lee factory crimp which may be causing higher pressures. I like that crimp though cause my extreme velocity spread using it is only 55 fps. I am using a chrono and have it out about 15 feet. I think I'll just go back 1/2 gr again to 2370 and try a different primer. Say, if any of you Swede shooters know where I can find a clamp-on front globe sight for the unthreaded m/96 muzzle so I can use my Soderin receiver sight I'd appreciate a shout. I won't be shooting for accuracy until I can mount some sights I can see. Not that I'm old or anything. Much obliged to all, Gary

Contact Torkjell Vic for sights.
t.vik@c2i.net

[This message has been edited by Scott H (edited 08-29-2001).]

There must be some variable other than powder charge which is making the heavier charge appear to give a lower velocity. Outside of Secondary Explosion Effect (S.E.E., a rare phenonomenon not in play in this instance), it is physically impossible for a greater charge of the same powder to give lower velocities, all other things being equal.

Some possible variables:

1. Temperature at time of chronographing.

2. Chronograph screen spacing inconsistent.

3. Barrel condition changed (unlikely).

4. Seating depth changed.

5. Crimping pressure changed.

6. Primer, powder, or brass lot changed (this you would know).

7. Unusual variance in moisture content of powder. If the loading of the two differnt lots was done on different days, the powder could have been much drier or more moist on one day than on another. Moisture content does not effect the performance of the powder, per se, so much as the relative weight (ie, weighing "damp" powder will give you more water and less powder at a given weight than weighing "dry" powder). You'd be surprised how much atmosphereric moisture powder can absorb, expecially if left out in a measure hopper. Don't believe me? Try metering the same IMR powder with identical powder measure settings when it is "dry" versus when it is "wet" and see what each volumetrically idential charge weighs.

I hate to disagree with my collegues, expecially Ken Howell, who knows more about interior ballistics than most of the rest of us put together, but I just cant buy the prospect of more powder giving less velocity. Just ain't gonna happen, in my admittedly humble opinion.

Sorry, Stonecreek my friend, but it's neither a personal opinion nor a wild hallucination that at some point, with some powders, an increase in the charge produces a lower velocity than the lighter charge produces. Many careful, dependable experimenters have seen it happen. I can not doubt their experience or their veracity simply because what they report doesn't make obvious sense to me.

Unfortunately, noticing and acknowledging that it occurs do not reveal the reason it occurs. In this realm of human endeavor, many things happen that don't come with an easily understandable reason attached.

Thanks for the tip, Scott. I have contacted Torkjell and he is off hunting in Germany. It's well into Autumn there already. I notice you have a different email address for him than I have. I'll add it to my address book. Gary

quote:

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Originally posted by Scott H:
Contact Torkjell Vic for sights.
t.vik@c2i.net

[This message has been edited by Scott H (edited 08-29-2001).]

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I agree w/ the phenomenon of the point of velocity loss at a point of additional powder added. I've seen it in I-4350 in compression in my .375HH.
The explanation could be in the efficiency of the burning of the powder. Consider it as a fuel, as in air to fuel ratio. When the ratio becomes "too rich" , as in too much powder, the efficiency declines or fails to improve. Granted, this would be mostly applicable in a max-load scenario.
My solution to the original posters question would be to try a hotter primer (FED215 or CCI250), of course starting low and working up again. This seemed to give me slightly higher velocity increase, and more shot consistancy at the chrony... respectfully, Sparkman375

"The explanation could be in the efficiency of the burning of the powder. Consider it as a fuel, as in air to fuel ratio. When the ratio becomes "too rich" , as in too much powder, the efficiency declines or fails to improve."

This would be true IF the charge depended on the oxygen in the limited amount of local air inside the case. But it depends solely on its own built-in supply of chemically bound oxygen � which is proportionately greater in the greater charge.

The efficiency of the primer's ignition of the powder charge depends on how much air space there is among the powder granules � on how easily, i e, the hot primer gas can penetrate to or at least near the front of the charge. A severely crammed charge of course eliminates much of this space that would remain in the lighter charge.

Regardless of the loading density (grains per cubic inch, or percentage of available space filled), the ability of the powder to burn � once all that's going to be lit has been lit � is the same for any amount of powder.

I'm thnking that Ken might be fairly close on that last post. In that the phenomenon is probably related to the possible speed of the initial flame front moving from primer throughout the charge. Though I think it might have been stated backwards somewhere previously, it seams as if small grain ball powder would reduce the available area for this flame front more so than large course grained powders. That being said, once the available flame path to the unignighted powders got to a restricted condition, net burn rate would be reduced, at least until the bullet left the case and opened the pack back up.
I've not experimented with it myself, but it seems possible.

I don't have anything to add, but I'll join the others in welcoming Ken Howell back, and I hope you are feeling much better.

Gentlemen,
Through the years, I have noticed what many have already mentioned. i.e. when approaching max pressures you see very little gain in veloicty for each grain of powder. There seems to be a point in every case/bullet wt. combo that when evloicties start to become stable (in one case for the .416 velocities varation is 7 fps max spread.) onece you pass this point pressures will rise with very little increase in veloc. and the extreme spreas will increase.
I have experienced velocity loss when using ball powders. For instance, using 90 grs of 748 ball I recieved (in 416) 2365fps with no pressure signs I went to 92 grains and only got 2350 fps I was using CCI 250 pr;;imers at the time. I went to Fed 215 primers and velocities started climing. no more problems.
I have never had this problem with stick powders, but I would either change powders or go to a hotter primer. If the primer is not hot enough to ignite the powder you get a partial burn, in other words the bullet starts to move before the powder can completly burn and leaves unburned powder going down the barrel with the bullet. I would try the Primer thing first, Just back off a little bit and work up again.
George

Ken Howell:

For the time being, let's just agree to disagree on the phenomenon in question; you have far greater experience than I in this area and I greatly respect your knowledge.

But I would like to have your comments on the issue of moisture content of powder and how it affects the net fuel content in a given load, as well as how moisture content might affect burning rate, gas production, etc. Would you do us the honor?

Ken Howell, glad you're back!
There is a phenomenon in black powder shooting that I wonder if it might be applicable here. When you reach a max load in a muzzle loader, and then go to a higher powder charge, muzzle velocity goes down. Why? Because the max load is the maximum amount of powder that can be ignited; adding more powder simply adds to the weight of stuff going out the end of the barrel (ejecta), effectively adding weight to the bullet, therefore lowering velocity.

This phenomenon does not only occur at maximum loads.
The powder/pressure-curve seems to be not a straight line at all. When developing loads, I noticed that the point of impact did not climb regularly with the increased load (1 grain-steps, 5 shot-groups). Sometimes the point of impact climbed regularly, then it stopped rising, and sometimes it jumped a considerable amount.
Fair weather, no wind, cartridges in the shade, shooter not drunk.

There's a book, now long out of print, called PRINCIPLES AND PRACTICES OF HANDLOADING AMMUNTION by Earl Naramore. If memory serves, it was brought out around 1948. (I'm too lazy to get up and look.) Seems like Mr. Naramore was some kind of ballistician for a government arsenal He has had several articles in the American Rifleman during the 1940's and 50's. The book is long winded and very dull in places, but well worth finding and reading. (It's also expensive when you do find one in good shape.)
Anyway, it was brought out in the book, that each powder has it's own pressure range, regardless of type. Go below that range and velocities can become erratic, and strange things like S.E.E. or P.E.P. and D.D.T. occur. (All those letters are the same thing, pick the one you like best.) Go the other way towards excessive pressures, and when you reach the limit for that powder, pressures increase greatly, but velocity does not. It slows down. Then you would have to go to a slightly slower powder to try and get more velocity.
I'm willing to bet that IMR-4831 just might be slow enough to give you that 2400 FPS your looking for, although I personally don't think trying to pick up another 30 FPS is worth all that trouble. One thing is for sure though. I think you are right at, or slightly above a safe maximum load in your Swede right now, if I understand what your post said, and if I understand Mr. Naramore's writings. (I've read that 800 plus page book four times and am going through it for round #5 right now. My advice is be careful.
Paul B.

Well, soon as my head stops spinning from trying to edit all this information I shall retire to my reloading room.

Here is what I think I have learned here so far. The powder I am using is either not igniting completely or is burning too fast resulting in high pressures and lower velocity because the bullet is still somewhere in the barrel when the gasses stop expanding.

Better ignition or a slower burning powder would burn until the bullet exits resulting in higher velocity and a lowering of internal pressures.

Since the load is well below published max loads I will load up another batch only with the 215 primers and see what the difference might be. Going to a slower powder makes some sense too if ignition isn't the problem.
Tomorrow is Friday, I will try to get to the range in the morning if my domestic assistant will not find too much for me to do tonight.

gsmithp,

I shoot the Swede, but in a modern Sako. I have had problems with incomplete combustion, and found that a primer change improved things. A change from CCI to Federal 210s made a great deal of difference.

Good shooting.

Patrick

I'll use the 210 as well since I don't have any 215's right now. Wasn't able to test another batch yet as the Minnesota State Fair is on and the family dragged me along with them to have fun or something. I'll try and find an hour on Monday to chrono a few rounds with the primer change. Thanks, Gary

quote:

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Originally posted by Patrick_D:
gsmithp,

I shoot the Swede, but in a modern Sako. I have had problems with incomplete combustion, and found that a primer change improved things. A change from CCI to Federal 210s made a great deal of difference.

Good shooting.

Patrick

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I would probably be of the hunch that much of the powder is getting pushed out the muzzle and burning there rather than while the bullet is still in the barrel. An interesting test would be to fire some rounds at dusk or night (make sure of your backstop!) and see how much change there is in the muzzle flash.