Home Forums Reloading Big Game Rifles Accurate 1680 low velocity in 450 Marlin.

I finally got around to reloading for my Marlin 1895m xlr chambered in 450 marlin. I've had good success with the factory 325gr leverevolution ammo so my goal was to try to match the performance of that load. The Hornady box suggests 2,225 fps out of a 24" barrel for the 325gr bullet but my rifle gets closer to 2,150 FPS out of its 24" barrel with that ammo. Not a big deal. So my goal was to achieve somewhere around 2,150 fps with good accuracy.
I chose Accurate 1680 powder because I've seen impressive numbers listed for it in the 450 marlin. Hornady lists a max load of 47.7gr giving 2,100 out of a 18.5" barrel. I also saw an article in Guns & ammo that listed a max load of 48gr of 1680 giving 2,230 from a 24" barrel. With that data it looked like I should easily make my velocity goal.
Well, my results have not matched the published data. I worked up to 48gr of 1680 with Hornady brass and winchester large rifle primer. At 48 gr of powder I'm getting only 1,965fps. I more recently got data from Accurate Powder with a max load of 49.5gr of 1680 giving 2,100 to 2,200 fps so I bumped up my load. At 49.5 gr I got an average of 1,990 fps.
Accuracy with all of these loads has been outstanding but I'm falling well short of the velocities that the data would suggest. Do I have a solow lot of powder? What could be going on? Has anyone loaded the the 450 marlin with AA1680? If so what were your results? Thanks.

No first hand experience here, but I'd like to be helpful in a small way so I ran your combination in QuickLOAD and here are the results.




When I see disparities between predictions and real results, I tend to rely on chronographed velocity as my primary pressure indicator---at least with bolt-action rifles. In other words I would keep on pushing until I see a velocity of about 2150, watching for signs...and it has been a pretty reliable method for me so far. I am not so sure I'd adopt that approach with a lever gun, though.

Thanks for the information. It looks like even some of the published data could be pushing the danger zone. From what I've read levers are difficult to gauge pressure. Traditional bolt action pressure signs will not show because the safe lever pressure is well below the point of flattened or blown primers.

10-4. More data points needed. Could be your powder is a slow lot. Or maybe not. Could be anything, or none of the above.

I am attracted to velocity like a moth to a flame, but I won't fly right into it. I think, since a lever gun might whisper sweet nothings in your ear as you push it to the limit and then will just up and leave you when it's had enough, it might be wise to forego the laser trajectory of the 2150 fps load and go with the rainbow trajectory 2000 fps load.


I've got a .30-30 load shooting a 175 Sierra at well below what I think its potential should be (a little over 2000 fps, but accurate), but if I want to push a bullet of similar weight over 2800 fps I drag out a .30-06.

I guess unless I was to get some powder from a different lot I'll never really know if that's the issue. I'm not terribly concerned about a little loss of speed. More curious about why my load is slower than the data I've seen.

Usually 1680 is very consistent from lot to lot. Or at least the several lots I have on hand are.

There are several reasons for differences in velocity between published data and your rifle. Here's some info I've posted before in threads discussing similar discrepancies:

Why Your Rifle Doesn't Get "Advertised" Velocities

Your chronograph might not be all that accurate. Modern “personal” chronographs are marvelous inventions, especially for the price, but light screens aren’t infallible, since not so oddly their results often vary according to light. Even with diffusers above the screens, readings can and will vary depending on the light from the heavens, even in chronographs costing far more than $100—though in higher-priced models the variations will be smaller, both because they deal with light better, and because their screen spacings are longer. Some newer chronographs don’t even use light screens, so don’t react to variations in light, though their accuracy can vary due to other reasons.
In contrast, the chronographs used in ballistic labs are all top-of-the-line. Sometimes they’re not even available to home handloaders, or the price is too steep. The spacing between the screens is even longer, making readings more accurate, and the chronographs are set up indoors, under consistent lights. (So far I don’t know of any ballistic labs that use non-light-screen chronographs, but that will probably change.)

You’re not using the “same” load. Many handloaders assume that all 130-grain .270 bullets produce the same pressures. This is a hold-over from the days when just about all bullets were simple cup-and-cores, so did produce similar pressures, but today’s bullets vary enormously.
The main pressure factors are bullet material and bearing surface, the amount of bullet that actually touches the bore. Pure copper jackets or bullets tend to produce more pressure than the common gilding metal, a combination of copper and a little zinc, because copper is softer and hence “grabbier.”
Bullets with softer cores and flat bases also tend to produce more pressure, because the core can be “bumped up” in diameter by the powder gas, sealing the bore far more than a boat-tailed bullet, which tends to let a little gas slip by, especially just after it leaves the case mouth.
The list of factors goes on and on, but the main point is that you can’t substitute data for one 130-grain .270 bullet for another and expect identical results. More or less pressure produces more or less velocity.

Powder varies in burning rate from lot to lot. Powder makers can’t make each batch of powder identical because of variations in atmospheric moisture. The powders sold to handloaders, however, usually come pretty close because different batches are normally blended, so a new batch of Warp Speed 40-Million comes within 2-3% of previous batches.
Even then, however, how you store powder can affect burning rate. Let’s say you live in the dry West, storing powder in typical 1-pound canisters in your garage. Every time a canister gets opened, the powder loses some moisture. After a few reloading sessions, that powder is going to weigh less. When you weigh 60 grains of H4831 six months from now, there’ll be slightly more powder in the pan of your scale.
But the biggie is lot-to-lot variation. As an example, look at loading manuals that list both Hodgdon H414 and Winchester 760. These are exactly the same powder, made in the same factory, but are put in different canisters. (If you don’t believe me, ask Hodgdon, which sells both these days.) Yet many manuals list different charges of 414 and 760 for the same bullet in the same cartridge. The numbers won’t be vastly different, but they will vary some, and the differences are totally due to variances in manufacturing lots. When bullet companies orders powder for testing, it would be unusual to get 760 and 414 from the same lot. In fact, I believe the only loading data that lists exactly the same data for both powders is Hodgdon’s.

Primers and brass also make a difference. Many handloaders only differentiate between standard and magnum rifle primers, but even among “standard” primers there’s enough difference to result in a 5% difference in pressure, resulting in about a 2.5% difference in velocity. And yes, there are even differences in primers from lot to lot.
Brass varies in weight, with heavier brass producing more pressure and velocity. Even the precise size of the flash-hole has some effect.

Your barrel is different than the test barrel. It doesn’t matter whether barrels are factory or custom, they all vary slightly in bore dimensions. Even the test barrels used in pressure labs vary somewhat. They’re required to match SAAMI (Small Arms and Ammunition Manufacturers Institute) dimensions, but those dimensions are not exact, just within a certain range.
One lab technician told me that in most of the smokeless rifle cartridges hunters use, each .0001” (one ten-thousandth of an inch) of bore diameter changes pressure about 800-1000 psi, about 2% in a typical modern rifle load, for about a 1% change in velocity. (One old ballistic rule is that any change in pressure also changes velocity about half as much. The variation differs slightly with the powder type, but the rule is still generally valid.) This means that if your .270’s bore measures .2773” instead of some company’s .2770” test barrel, it will produce about 3% less velocity--about 90 fps in a typical 130-grain load.
Since bore diameters CANNOT be held to tolerances of .0001”, even test barrels produce different pressures and velocities with the same load. In fact, it would be a major miracle if they did not.

Don't look at how far off from book you are. Look at how close you are. Within 200 FPS is not all that bad.

One other thing, using Quickload as a predictor, is that it is not at all accurate with big capacity straightwall cases, overestimating pressure and velocity by a fairly good margin.

I dope it by increasing case capacity, generally starting at 3.5% with light bullets and as much as 7% with heavier bullets. This is with a .45-70.

To get the right amount of "kentucky windage" on the case capacity, I will chronograph the load in question and adjust the capacity to get the pressure/velocity right.

After that, I can get good predictions with that combination.

I have not ever been able to get H322 and Quickload to agree with any precision on an initial load.

I am an avid user of Quickload, but wouldn't trust it for big capacity straightwall cases.

Good advise.

John, that is very interesting and I'll be chewing on it for a while.

Right now my thoughts are focused on how it would affect the first few inches of bullet travel where ignition and its effects on pressure would be seen. It looks like a pretty complex problem. It's difficult to take an "all else being equal" approach to it, because it seems that all else cannot be equal---it changes up everything.

If you've got something to throw at that line of thought, I'd be most interested.

obie458,
I've used AA1680 with my 45-70 and noticed the same thing. My measured velocities were over 200 fps slower than the published data. My Marlin has a 22" barrel, not like the 18 1/2" models which would explain some velocity loss

I always learned longer barrels resulted in velocity GAINS... that's why they always use a 24" barrel for velocity. Different cartridges vary but I saw a good way to put it in general is 25fps per inch is gained in regards to barrel length