Dacron filler (for reloading 450/400 NE 3”)


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Mar 1, 2020
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I just purchased a DR in 450/400 NE 3”. My rifle should be delivered to me anytime now.
While waiting for it, I am loading up a few rounds to check the rifle out when I have it in my possession.

After reading through some discussions on the web and Hornady reference I have decided to use the following:

Hornady brass
Federal 215
Hornady 400 gn FMJ

COAL 3.650”

80 gn and 81 gn

RL 15
68 gn and 69 gn

When I charge the case with RL 15, there seems to be quite a void whereas H4831sc seems to have minimal void.

On further web surfing, many talk of using Dacron filler but some say do not use it. I never had a caliber requiring fillers so I would appreciate your informed input.
What say you...to use Dacron or not to use?

If you use it, would 2 or 3 grains adequate? Have you had Dacron melt and foul up the action or bbl?

the best thing to fill a case with is powder, which means use more of a slower one.
the trouble is will it regulate in your double?
With smokeless, the Dacron will come out in a cloud of fine particles and short strands. 2-3 gr total fill of Dacron is not very dense in a large capacity case with maybe 30-40% empty volume fill and is by definition low mass. You can shoot if over fresh snow in the winter and see what comes out of the muzzle. No, it won't melt or leave any residue in the bore. The specific heat during the smokeless powder burn is too low and the event duration is too short.

Dacron can melt and leave some residue if used as a blackpowder cartridge filler. The specific heat of burning BP is much higher because of the high percentage of unburned solids in BP. The effects of Dacron used as BP cartridge filler is usually exaggerated and invariably gets carried over into discussions of smokeless loading. And even in blackpowder cartridge use it is no worse than and usually a lot less noticeable than the regular smokeless shotshell plastic wad residue left in shotgun bores after firing long strings.

But as Bruce stated, the best filler for most similar applications for near full pressure, hunting type rounds is a larger volume of slower powder. The best use for Dacron filler in smokeless carts, especially large capacity straight walled cases, is for consistency of pressures and velocities in greatly reduced, low pressure, low velocity loads with powders like 5744 under cast bullets.
I use approx 0.5g Dacron with 80.0 gr 4831 and 400 gr dgx and dgs In my DR. I try to pull the Dacron apart to reduce the weight to fill the remaining air volume in the case. I have good success with this without our have any residue in the barrel.
Thank you all for the replies.

I use approx 0.5g Dacron with 80.0 gr 4831 and 400 gr dgx and dgs In my DR. I try to pull the Dacron apart to reduce the weight to fill the remaining air volume in the case. I have good success with this without our have any residue in the barrel.

Scott, it it 80 gn of H4831 or IMR 4831?
My Regulated loads are
DGX-79.0 g IMR4831. COAL 3.640, RT barrel 2032fps, left 2044 FPS

DGS- 79.5 g IMR4831, COAL3.656, Rt. barrel
2044 FPS, left 2061.
I use foam backer rod, 1/2", purchased from the hardware store, for my load of 63 grain Rr-15, one grain under Hornady maximum.

I got the recommendation from AR, and read of use of similar wads in Graeme Wright's "Shooting the British Double Rifle "

Kynoch sells a similar product, although more costly.
I find it much easier to work with than Dacron .
Burns cleanly, no residue.
I cut them to length so that when seated over the powder, bullet seating just slightly compresses the foam. I pinch twist the foam to start in the case, then press and seat it with a pencil eraser.
The R-15 load regulates in my rifle better than the 87 grain on VN-135 and has less recoil.
I use foam earplugs for the same purpose. Quick, easy, effective. But it is not needed with the slower / more bulky powders.
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certain things that work ok in straight cases should be avoided in bottlenecks.
this is because tsome things compress behind the shoulder and cannot escape, causing extra pressure.
Your on the right track, use 5 grs of dacron pillow stuffing or Kynoch foam plugs from England, The Dacron won't melt, it will come out as a plug and land 10 or 15 ft. on the ground..Always a good idea with double rifles to use a filler, using powder to fill a double rifle case is verboten, they are simply too large, even with H 4831..Use a new wood pencil flat faced new, to stuff the dacron in in the case, the wood pencil is spark proof...Never use a substance that melts..
Using loose Dacron filler in straight wall cases with smokeless loads is of basically no issue if done properly and it's easy to do. It won't melt.... the "specific heat" of the smokeless burn event is too low. It will either come out in a dark compressed mass as is common if used in BP loads (which I won't do- where a stiff wad filler is advised) or as a cloud of shredded strands/clumps of Dacron as what usually happens with smokeless loads. In straight wall cases, with smokeless loads, loose Dacron fill only very minimally increases pressure and usually decreases standard deviation of velocity.

I've found the easiest way to use is to cut elongated sections of fairly thick Dacron batting that is 1/4" to 3/8" thick. The section of Dacron should be of such volume that when it is seated on the powder and the bullet is seated on top, the Dacron is only minimally compressed. For most large capacity cases that amounts to something well less than 3 gr of Dacron- hardly any increase of projectile mass at all to worry about. But as with any loading- start low and work up using a chronograph or other methods to gauge pressure or indicators of pressure.

First pic shows basic components prior to charging. Rest are of sequence of how I insert Dacron for smokeless loads where there is advantage for smokeless loads in very large capacity cases that have too much capacity or for very low pressure/low velocity, light loads with powders like 5744 under cast bullets. Fairly long tweezers work well to "pull" the Dacron fully into the case and on top of the powder once an end of the Dacron has first been started with the fingers. Last pic is of level of Dacron that has been fully seated on top of powder and is ready for seating of bullet.

I have a close friend that is a double rifle fan. Has well over 2 dozen of them in various calibers up to 577 NE. Some years ago he had serious concerns about various different fillers being used. Since we had a means to test this, we did.

We consider 45000 PSI to be max working pressure in double rifles. In this case we used a 470 NE, 500 gr Woodleigh Softs for the test. It is our contention that overall Dacron can, and does cause higher pressures, and since there are other materials available that are far more consistent, foam being at the top of the list, why use something that could cause erratic and over max pressure loads, which can do damage to your rifle.

:) Interesting I'll say! I've never seen that type of pressure or velocity difference or disparity of data between loose Dacron and other fillers. I've shot a wide variety of them, pretty much the same you tested, in repetitions and in different cartridges, different bullets and powders... including: foam backer, styrofoam, cornstarch packing pellets, granulated poly as used for shotshell filler and several different cereal based granulated fillers. The only ones to show a small increase in velocity with a commensurate very small increased pressure were the granulated cereal fillers like grits, cream o wheat and germade. I am having trouble visualizing the reason for such a discrepancy between a low mass, low density filler like Dacron as being the one singled out in the data and the other varieties of materials used as fillers. The discrepancy raised a red flag. No way that 2gr of low mass, low density Dacron filler holding powder against the rear of cartridge and filling air space between powder and bullet would increase pressure out of proportion to the similar application of most all the other fillers tested- nope, something else is going on.

And last but absolutely not least... I see no control shots in the data- a basic tenant for valid scientific testing. Nothing to compare any of the data to. And one variable was not tested which I suspect may be a primary factor affecting pressure.

Might I suggest an abbreviated rerun of the test including a another variable. Additionally, the rerun needs to include a set of 3 control shots. The test equipment will be attached and calibrated in identical fashion. (I'm assuming an Oehler or similar piezoelectric transducer epoxied to the chamber wall and wired to a recorder/ receiver??) All loads will be identical with same bullet and powder and powder charge- the only load differences will be if filler is used or not and type of filler. 12 shots will be required for the test.

One set of three shots with NO FILLER and the rifle rested and shot at horizontal (the control set if you will). One set of three shots with NO FILLER and the rifle held and shot at a high angle where gravity will hold powder at base of cartridge case...the variable not tested in the first run. One set of three shots with foam backer rod filler. One set of three shots with Dacron filler. Obviously the fillers hold the powder next to the cartridge case's base so no need for changing orientation from normal horitzontal for these shots. The sequence of test shots from each sample group and among the groups should be fired in random order and the barrel cooled equally between shots so temperature will not skew/bias the results.

My suspicions for an hypothesis is that the orientation of the powder in the case upon ignition may affect pressure and the pressure of low density Dacron filler load may be similar to a non-fillered load fired with at high angle where powder is against rear of case at ignition. That is the reason for my suggestion to increase the scope of the test to include the control and the variable of the orientation of the powder.

Just repeating here and not my idea at all as it has been around quite a few years, but quite a number of knowledgable shooters and ballisticians out there subscribe to the pressure wave theory of internal ballistics. Where sometimes, after powder ignition in a cartridge with a lot of air space, an unexpectedly high pressure zone or pressure focus area (a pressure wave) accumulates for a very short time at the base of a bullet. Some also believe that in addition to the air space variable, the orientation of the powder upon ignition affects the parameters and shape and scope of the pressure wave and likewise the peak pressure within the combustion chamber.

The other thing to consider is that each load is an entity unto itself. The whole idea behind the use of a filler to begin with is to decrease the velocity SD (and correlated pressure SD). Any load developed with a different major component needs to be worked up from low suggested start then approach the objective using at least a chronograph. If significant decreases in velocity SDs are not realized, then there is no reason to use a filler to begin with. Then approach the objective velocity with a different powder.
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No way that 2gr of low mass, low density Dacron filler holding powder against the rear of cartridge and filling air space between powder and bullet would increase pressure out of proportion to the similar application of most all the other fillers tested- nope, something else is going on.

There are a lot of things that will surprise one when you are doing such work. First, let me tell you, we did not do this to publish a paper in Scientific American or Double Rifle Journal! We are shooters/hunters, and my friend with that owns many double rifles wanted to find a better way, plain and simple. He had a suspicion that dacron and some other materials used for fillers could be improved upon greatly, and that at times some fillers could cause excess pressures. We were already doing other work with the 470 NE and we added this test to learn more about various fillers.

I have a 50 yard indoor shooting range here. I enjoy doing test work, load data, bullet terminal data, and really enjoy running various pressure tests, which this was simply one tiny little learning project for us.


I run a Oehler System 83, along with Pressure Trace 1 and 2. I have run pressures on various projects for over 20 years.



While the Oehler is a incredibly reliable and stand alone system, I much prefer the software for the PT systems, which give a great view of the pressure curves, far better than the more expensive Oehler, so there are many times when we use the PT systems for a more detailed curve. You would be amazed at what you can learn by viewing what happens in that 1.5 to 2 milliseconds.

I was using a PT II below for a blending test in 500 NE, I wanted to see the Curve.



We used the PT 1 Unit for the 470 NE tests, like the Oehler, it is a stand alone system, but gives you an excellent view of the curves with its better software. Unfortunately for the shooting world it is no longer available, and I am lucky to have two of these units, both very coveted and put away.


The test work done on the fillers was in 2010. It gave us enough information to be able to make decisions based on what we learned from it. And that was, and is that Foam is more consistent and less volatile than some other fillers. It was our contention that one could get in some pressure issues simply because of filler, and or the type of filler used. I can assure you that the test was conducted by very experienced hand loaders, and done in a manner that left us no doubt about the results.

Personally I do not use fillers for anything, so I have no stake in the outcome one way or the other. I am not in the Foam Backer business, and have no foam to sell you. I could care less one way or the other whether to use Dacron or Foam, or toilet paper, used or not used................Which we did not test "Used Toilet" paper......... HEH..........Maybe we should have, to been more thorough. HEH HEH........

I often find that when tested results do not go along with traditional beliefs that it can be disconcerting to those with traditional and or conventional wisdom.

I much prefer to use a powder that fills the case completely, and even be compressed............
the best thing to fill a case with is powder, which means use more of a slower one.
the trouble is will it regulate in your double?

I concur...............

very interesting michael.

Yes, an eye opener you might say. We have done many such things here that would be very surprising to many.............
A good stiff load of Dacron, say 5 grs, will up PSI about 1000 to 1500 PSI, hardly enough to make much difference in regulation, but don't push your doubles beyond 40,000 PSI and with your dacron or Kynoch plug you will be at less than 42,000 PSI and good to go. I shoot my 470 at 2020 FPS. a mild load, easy on the body and quick to come back to aim and it kills the same as when I used to load it a 2245 FPS... I load my 450-400 3" at 2100 and 5gs of Dacron..and it works great and my preferred buffalo gun..

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