Off the reservation combinations

9

95GTSpeedDemon

New member
7mm rem mag.
im working up loads with 120gr nosler BT's. i dont need max FPS.
H4350, IMR4198 (based of of tons of research and already testing, it works.), & varget.
now, 4350 & varget have hodgen data for up to 130gr.
What i want to do is make some powder fouling shots / fire formers with some spare bullets i wont be using, but they are 150gr. apparently when switching powders theres an accuracy hit for a couple shots. im trying to eliminate that issue, without having to use the very hard to find expensive 120's.

Finding out whats really possible, not just by whats been vetted in a published book, is what im after.

i have gordon's & quickload.
awhile back when i first started using QL and was more trusting of it, i made some 4198 150gr foulers. (modern reloading pg 285 38.5-43gr)

Im a little more leery about doing that now that i have learned a bit more, but maybe someone else has tested it.

are these programs accurate when estimating varget and 150gr pills as far as pressure goes. S.E.E. is definitely a concern since im around that 70% fill mark.

Varget is slower burning than 4198, so the chance of SEE would be greater is what i read.
 
Welcome to the forum. Please pop over here to introduce yourself to the board.

CAUTION: The following post (or a page linked to) includes or discusses loading data not covered by currently published sources of tested data for this cartridge (QuickLOAD or Gordon's Reloading Tool data is not professionally tested). USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assumes any liability for any damage or injury resulting from the use of this information.

SEE seems to come in two flavors. The one explained by the late Dr. Lloyd E. Brownell, who saw some of these random events in his lab at the University of Michigan in the 60s, showed the randomizing of pressure begins at more like 60% case fill and gets worse as case fill goes down to 40% or so. Most manufacturers recommend 70% to provide a safety margin that allows for variation in the make of cases and for how deeply different bullet designs seat into the case, thus affecting how much volume they take up.

The other is the very rare situation in which a very small quantity—10-20% case fill–seems to detonate. Normally, the powder being made into separate grains prevents detonation by having no continuous path through which an ignition shockwave can travel. However, when the powder quantity is small enough, partial ignition can burn off the surface and fuse it into a contiguous material mass. A lot of handloaders have seen that happen in varying degrees, and, in theory, such a structure could detonate when the stars all line up correctly.

As far as pressures from the interior ballistics programs go, if you compare published data of actual measurements, like Hodgdon's, it doesn't take long to see the program models are often off a bit. This is due to some details of losses and ignition not being modeled. If you take a maximum published load, use the capacity of the brand of cartridge case used in their measurement of that data, and adjust the powder burn rate factor, Ba, until you get a pressure match for the maximum load, you will usually have a higher velocity than the manufacturer shows. If the velocity is correct, the pressure is often too low, but not always. I have never seen one that is set correctly for the maximum pressure that tracked the pressures for the starting loads very well, so I aim to match the maximum before I start switching bullets around to get a safe value.

Each cartridge and bullet combination behaves a bit differently, but I don't think I've seen a situation where, if you reach maximum pressure in the simulator, knocking the charge down 10% won't give you a safe start load, but never say never. Try to find a Ba value that seems to work well with other cartridges, then apply that to your new case.

One thing the programs are pretty good at is ratios. If you put a 120-grain bullet charge in the software and then substitute a 150-grain bullet, then change the charge to match the 120-grain bullet's predicted peak pressure, the charge adjustment ratio you need to make to do that will typically match the real-world charge adjustment ratio well.

Obviously, for a magnum case, 4198 is too fast to get into the usual magnum velocity range at published pressure limits. A fast powder doesn't let the bullet move very far before the pressure peaks, so expansion is low, and the pressure peaks in a smaller volume, and at safe peak pressures, won't deliver high muzzle pressure for the last bit of bullet acceleration. A fast powder is also more likely to be "spikey" in response to small charge increases, IME, so it can be more ticklish to adjust for and have more temperature sensitivity and so on.
 
thank you for that explanation!

i was playing with the program and what i found was 4198 showed low pressure even at the 44gr max load listed for 120's, or 43gr for the 150's (bullet bearing surface aside).
i went all the way up to 48gr in the software with the 120 and like you described and i expected, the fps doesnt change much, but pressure rises.

i will play with the software like you described and see if i can come up with a load that seems "safe" to try.

another forum i posted on noted that powder mfg's have changed formulations sometimes many times over the years so load data and the softwares might not be as accurate as one would think.
 
QuickLOAD's author personally tests samples, but there is no way for him to know if the sample he buys is typical or is on the fast or slow side of the burn rate tolerance. He also repeats testing occasionally, but I don't know his schedule for that.

GRT was a little different in that it would, I think, often borrow from QL as a starting point, then encourage feedback from users with Pressure Trace instruments to adjust the characteristic curves for its slightly different dual inflection point model. But after Gordon passed away without leaving anyone the password for getting into the GRT source code, that progress has stopped, I believe. Also, Jim Ristow has since retired for age and health reasons, so the Pressure Trace is no longer available. A calamity of issues.
 
Yeah, overall I feel like I might just end up abandoning trying to play with varget. Lite case fill usually doesn't help with extreme spread, so even if it ends up being accurate with it once I try to shoot at distance it's going to not be as great. No sense in trying to blow myself up with nothing to gain. Sometimes I just got to be reminded that just because I possibly can doesn't mean I should LOL
 
There are reasons ammunition developers and manufacturers use slower powders for larger cases. Velocity with appropriate pressures, standard deviation with attendant accuracy, and SAFETY. It's easy to overload using faster powders in big cases.
 
i personally find that using slower than recommended burn rate powders, (there is a limit of course i'll mention in a minute) you will get better velocities at nominal pressure, and longer barrel life.

because most over-bore calibers tend to eat barrels that is an issue to me.

now as to slower than recommended burn rates, if you find a powder too slow for the rest of your components; cartridge, bullet, barrel: you will find that it's still burning when the cork pops out.
thus wasting power and degrading accuracy, also unable to reach normal velocities.
one example of this which shows the margin between usable and unusable is; i had a 243win with 22inch tube, using hornady 105a-max pills, and hodgdon h-1000 powder. but when i dropped to the hornady 103eld-x i could no longer use the h-1000, there being just enough differance in the two pills to make the 103 pop out a little too early.

all that being said, even the 4350's are faster than i would recommend for the 7mag assuming it is a bolt gun(which it most probably is). i would look at anything between hodgdon hybrid100v and ramshot magnum.

there are burn rate charts on the web easy to find if you need one.

lastly for foulers and fire forming your brass, yeah any powder that will safely push the pig down the pipe is fine.


DISCLAIMER! IT HAS BEEN SAID THAT I ALWAYS GIVE BAD ADVICE HERE; SO USE AT YOUR OWN RISK.
 
??????
In the 120s im going to try h4350, h4831sc, varget, and imr4198.
The first two are the most likely to be used, im curious if the 4831 actually burns it all, as it needs pressure to get it all burned and 120s dont really do that well lol
 
well just a thought, you can fire one at night just to see how much fire you are getting out the muzzle, compare with a faster powder.

little difference, your ok. big difference, not so much.


one thing i noticed when i "went too far" was that you don't reach the expected velocity and adding more powder makes very little difference, it's like anything over "this much" and it burns outside the tube. thus no increase in velocity. or very little.
 
There are a couple of things that can cause that. The gun is starting to stretch more, and enlarging the chamber. This is where the failure of velocity to grow with charge is a pressure sign, though a rifle with uneven locking lug contact can fool you on this point. Another is due to compressed loads. Compress them enough, and you start to lose space between the grains so they can light up a little more gradually. That second case is not to be relied on. It happens with some powders in some chambering and bullet combinations.
 
well no pressure signs, case not full, not close to max velocity but near max charge... increase charge and no increase of velocity but increase of noise. change to a little faster burn rate powder and speed comes up noise goes down, accuracy comes up.... i still think the powder was just a little too slow for the rest of the componants/combination
 
My point was that failure of velocity to increase with charge weight is a pressure sign all by itself in many instances. Cases and primers can show or not show pressure indications in actual pressures that differ by as much as two to one. And that's with military cases from the same lot and with the same load history. They are very unreliable.

On the other hand, you also don't want to be fooled by the inadequate sample size problem. If you make any load, you know it will have some velocity variation, as indicated by the ES. If you look at just one round for the velocity gain, as the velocity ladders that fool people often do, you don't really know if that one round was on the high or low ends or the middle of the bell curve of velocity scatter described by the SD. In other words, it could be randomly low or high or in between. It takes more rounds at each load level to get some idea of where the average is. I usually find the mean values of ten rounds at each charge level provides a reasonably clear indication of whether there is a significant deviation from the velocity trend at a particular load level.
 
georgehwbush said:
i'm a little on the cheep side and generally only fire seven or eight rounds of each step on a ladder test.
Click to expand...
These days with the cost and unreliable availability of components I think most of us are in this boat. I’m fortunate that I developed all of my loads about 10-12 years ago and stocked up on needed components enough to pretty much last me my remaining lifetime. I still fool with newer loads etc. but don’t quite work them up with as extensive of a process as in past years. Plus I don’t do nearly as much rifle shooting as before with more of an emphasis on practical pistol practice. These days my shooting is confined to indoor ranges with 25yd and 50yd lanes with occasional outdoors extended ranges for rifles. Because of these limits I mostly shoot my PCC’s and pistols offhand, no bench shooting. Lever actions at 50yds offhand are more than enough of a challenge at my age and degree of crappy eyesight.
 
I had been patreon supporter to GRT, till the the man passed away unexpectedly and his widow stopped the patreon program. I still feel pretty much in debt to Gordon.

The software generally works pretty well. There are exceptions of course. Light loads are usually no good. The latest head scratcher was a normal load for 6.5mm swedish Mauser. MV was significantly lower than the book and the sim. I seated the bullet rather shallow, trying to chase the lands. The brass was sooty and I felt some gas blow back. I reckoned the brass neck just didn't have enough time to expand to seal. I seated deeper and put in some crimp, and the problem went away. Things like that the software can't model correctly.

I'm also known to be cheap, so I tend to use faster powder to save on powder usage. I don't chase speed anyway, so it works out.

About additional powder charge for more speed, sometimes we lose the perspective. I have friends who swear a 0.1gr would make huge difference, and they saw that when they developed handgun loads. But 0.1gr change in a 50gr rifle load most certainly would make much smaller difference, so much so that it may be even masked by the "noise" of chrono measurements. I usually go in step of 1%, or 0.5gr for 50gr load. Even that the results are occasionally not indicative.

-TL

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