150 grain .284 Speer hot core, WC872 82 grains, 7mm Rem Mag

[Oldfeller]

I have some WC872 that I have been trying to utilize in 7mm Rem Mag. Past attempts have been stalled at 82 grains in a tapped down mild compression against a .020" off the lands 150 grain Speer flat bottomed hot core (bullets are pull downs from Federal factory loads so don't feel bad if you bullet detector just went off on you because Speer/ATK doesn't sell that particular bullet as a Speer or as a Federal component).

Issue is I have got as much powder as can be coaxed into the case but am only getting 3,090 fps to 3,134 fps which is not all it could be. Barrel is dirty after 10 shots and throat is getting a hard powder residue after 20 shots that requires some scrubbing to remove.

Scratching my old Shooters noggin, it feels like the WC872 powder needs some help to get it to burn cleaner/slightly faster.

I am already using a magnum primer and I am thinking I need a small booster to get the pressure up faster and a bit higher to get a cleaner burn. Book data for H870 (nearest equivalent) can be found in several manuals, Speer #11 and Lee's thick tomb both show the same loading for minimum and maximum for all bullet weights up through 160 grains -- 80 grains (which is two of their plastic scoops full which is why they stop at 80 grains of the slightly lighter powder). Lee shows pressure at 46,400 cup for the load, which does not really even make it up to normal minimum load pressures for the 7mm Rem Mag.

I likely am at less pressure than that (within lot variations and all on the medium ball 20mm cannon powders, mine being WC872). Primers are just a simple flat spot, still rounded some on the corners.

I am going to use up the powder over time, but I want to get something a little more 7rem-mag-ish out of it. It seems a shame for my 7mm-08 to be slinging the same bullet at just 300 fps less velocity than the 7rem-mag using twice as much powder by weight (IMR 4895 being used in the in 7mm-08).

Here's my thought. Bump with WC820 (very fine, very small ball powder) scooping 4.4 grains of it out of the .3cc Lee dipper. WC820 will burn at H110 rate, lifting the entire starting side and top of the pressure curve some and guaranteeing better ignition and cleaner burn of the 80 grains of WC 872 that sits on top of it. I'll get some extra pressure and fps, but not a killing lot.

If I don't get some normal looking pressure on the primer, I'll step up by half grains up to the .5cc Lee dipper which is 7.6 grains to see if I can safely go there.

This will work volume-wise as the tiny fine balls of wc820 will snuggle up inside the air spaces of the lowest levels of WC872 larger spheres during the load tap down step, not taking up as much space as you would think it would.


---------- why bring this here? ----------


Bumping is a skill used here, as well as large familiarity with the surplus powders mentioned. Why struggle to do it with WC872 & WC820 instead of just buying 2 pounds of IMR 4831 and using book loads and techniques?

Well, heck fire, what is the fun in that? I already got close to the equivalent speed, but I have LOW LOW pressure still (and a dirty throat residue) and I certainly have some more room to speed the burn rate up a little tiny bit to find some more fps up at the lower end of "magnum" pressures.

Now, question becomes has anyone done something along these lines before and what did you learn about it?

(benchmarking is an art form, you build off of what has gone before if you can).

[leadman]

Having shot a 7mm Rem Mag for about 15 years I can say that my Chrony says you are right in the velocity range for 150gr 7mm factory loads. I too have used WC872 in the 7mmRM with 150gr and 140gr jacketed bullets. Out of a Rem 700 made about 1972 (original blued stainless barrel) my velocity was close to yours.
In my Encore proHnter with 28" barrel I pick up more about another 150fps with WC872, about another 300fps using IMR7828.
My lot of WC820 is closer to 2400 speed than H110.
I personally would not try duplexing powders just to get a little more velocity when you are already in the normal velocity range for the cartridge.

[Oldfeller]

Well, we agree that I've got all that the base powder WC872 has to offer, and we likely also agree that the resulting pressure is well below the normal magnum range pressures in a 7mmRemMag (Richard Lee lists the pressure as low as 43600 cup for 80 grains of H870).

Here is the interesting part of the thought -- mild bumping in small stages looking for some normal magnum pressure signs in the full case WC872 load are likely to increase the area covered under the pressure curve quite a bit as you are raising up a very broad flat curve by increasing the start pressure. Indeed, if you did increase pressure and burn rate some then the amount of unburned powder remnants coming out the muzzle would go down as well. Efficiency goes up ....

The second interesting point is the very fine grain nature of the WC820 bump powder will hide the grains in between the larger WC872 grains, in essence allowing a heavier, denser powder charge in the same case volume.



I need Loyd or Buckshot or Maven or some of the other older experimenters to comment, as likely they have done something analogous as they have used the same powders in a variety of cartridges.

Otherwise, I guess I'll reinvent the wheel by myself.

[Lloyd Smale]

Ive never used 872 or any of the other 50bmg powders for mag rifles. Ive allways been one that believed it using powders in the right burning rates for what im loading. I dont try to get 50bmg powder to work in an 06 and i dont try to get bullseye push 300 grain 44 mag loads either. My surplus experience is with pistol powders and powders made for the 223/308. that said im with leadman. If your truely getting 3100fps out of a 150 in a 7mag your doing pretty darned good. thats the velocity they top out in pressure at with most combos ive tried. Bottom line too is that load will kill about anything you shoot it at and will be flatter shooting then a 130 grain 270. What id be looking at more the getting a few more fps is accuracy. If that load shot moa the experimenting would come to a screatching halt.

[Oldfeller]

Thank you for the input, Lloyd. That's two votes for "quit while you are ahead".

I think I will quit while I am ahead.


Question all answered -- thread is finished.

[geargnasher]

Three votes. If you DO use a little kicker charge to get that case full of 872 powder burning efficiently you'll find out how much energy you've really been messing with there, but were mostly blowing out the muzzle unused. Your primary concern is excessive combustion heat and bore surface damage, even without the kicker. You can make it work, but not the way you're going about it.

Gear

[swheeler]

Kelly you stuck on burning that WC872 get some real bullets, 160 gr or better yet 175 grs, what you been shootin field mice:)

[Oldfeller]

Field mice sized deer is all they got around where I live. Size of a big dog or a full sized billy goat with skinny legs.

120 grain Sierra pro hunter slug at 3,100 fps in the neck or lungs is recommended minimum 7mm-08 dosage around here.

[swheeler]

I have not used a kicker with 872 in any rifles, but I have used WC872 in 7mm Rem Mag with 160 Speers and 175 Noslers, never did reach book velocities with similar loading, compressed case full. I have two very different lots/speeds, one from Jeff Bartlett that is real close to canister H870 and one from Pat McDonald that is slooooow, about 200 fps slower on same loading, I've about used up the 32 pounds of the faster Bartlett stuff. I found that in the 264 WM with 140 gr Hornadys and the 300 RUM with various 180,200 and 220 gr bullets I could reach or slightly exceed book velocities, with normal pressure. So my recommendation is trade the 7mm mag for a 300 RUM, you can use about 33 more grains of powder per load, enjoy the recoil and kill two of those tiny deer at a time! Good to see you post Kelly;-)

[Lloyd Smale]

keep in mind that its rare a "BOOK" load is really going to give "BOOK" velocity. Most manuals are pretty generous with there velocity readings for a load. Probably a matter of a company like hogdon wanting you to think there 4831 is faster then imr's or wanting you to think that magicaly because your using a 150 grain speer bullet your load will be a 100 fps faster then the same load with a hornady bullet. Also look at the guns they use. Sure a certain 7 mag load might make X velocity out of a 30 inch test barrel but wont come close in your 24 inch barrel. Lots of it is marketing. I use a loading manual considering them a tool to give me a good safe load but not really giving me a top end load and I sure don't take there velocity readings to the bank

[swheeler]

Yes all things have to be considered and a chrono is handy, probably why I've been using them since late 1980's, wish I had one the first 25 years I loaded.