300 RUM, 200 AccuBond + Retumbo Results:

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Jon A, Aug 19, 2003.

  1. Jon A

    Jon A Well-Known Member

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    I finally got a chance to do some loading and shooting and have found my new “do everything load” for my 300 RUM. I know some out there are looking for results/experience with these components, so here you go:

    The Rifle:

    [​IMG]

    My rifle isn’t some big heavy bench gun or expensive custom gun. It’s just your average run-of-the-mill A-Bolt Composite Stalker. [​IMG] It has the factory original (pencil thin) 26” barrel with well over 1,000 rounds through it. About ¾ of those were from when it was a 300 Win Mag before I had it rechambered to RUM. The only accuracy mods I’ve done to it are a Moyer’s trigger, and relieving some more material from the barrel channel of the much-too-flexible composite stock to make sure the free-floated barrel stays free-floated (it must have been something to do with the increase in recoil of the RUM, but right after I got it rechambered it wouldn’t shoot worth a damn—-the barrel contacting the stock was the problem). The scope is a Leopold 3.5-10X50mm with Stoney Point Target Knobs.

    The Load:

    200 Accubond , 95 grains of Retumbo, brand new completely un-prepped Remington cases, Federal 215 primers loaded to 3.60” OAL, 3177 fps.

    I started out with H870 because I had a bunch I wanted to shoot up and I thought I could get some good velocities. I was easily able to beat the above velocity with it. I didn’t get a pressure sign (in my rifle the first sign is an ejector mark) until a round clocked 3311. Backing off quite a bit still put me at 3246, but the load just wouldn’t shoot. I think it’s because I was in too big a hurry to pack all that powder in the case properly so I was compressing it so much the seating depth varied widely. Anyway, it wouldn’t shoot and H870 is dead. Enough about that.

    96 grains of Retumbo yielded 3208 and no pressure signs. I didn’t clock 97 grains but I’d expect it would have gone around 3240. I got a slight ejector mark with that one. Extraction was unchanged—still a finger-tip affair.

    So I backed off to 95 grains. What this powder lacked in velocity, it made up for with consistency. Three randomly picked rounds went 3171, 3183 and 3179. I know it’s only three rounds but I’ve never had an extreme spread of 12 and a standard deviation of 5 before even with only three rounds. This is with “as thrown” powder charges, no less. I knew right there this load would be more accurate.

    Disclaimer: I feel this load is safe in my rifle but if you try it in yours you will die, guaranteed. Don’t try it. You will die!!!

    OK, now that that’s out of the way, I can tell you that my rifle has a rather sloppy chamber and with rounds seated to 3.60” to fit in the magazine it basically has a free-bore as well. So you really might run into pressure signs before I did. This is backed up by Brent Moffit’s data—at 90 grains he was at 3082 fps while I was only at 2977 fps. At 92 grains I was still only at 3062 fps. So really, work your way up to this slowly guys—especially given the tales of Retumbo acting completely differently for different people. Be safe.

    The Bullet:

    I now realize I forgot to take a pic of the bullets before firing. Oops. Sorry. You all know what they look like anyway.

    I have been waiting for a very long time for somebody to make a heavy, high BC 30 bullet with reliable terminal performance. I was actually close to setting myself up to swage my own bullets so I could make what I want. Well, Nosler came through. It seems so far they did it well enough I might not have to get into the swaging business. Don’t get me wrong, there is nothing “earth-shattering” about the terminal performance of these bullets. Some bullets will do some things better. Other bullets will do other things better. But this bullet lived up to my expectations (as far as I could test it). It seems like a very good all around bullet for my purposes.

    I apologize for my lack of photography skills and/or equipment. Damn I need a digital camera! Anyway, these pics were the best I could do. I hope they’re good enough for you guys:

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    The bullets from left to right are the 180 Scirocco, 180 XLC, and 200 AccuBond. The bullet of each type on the left is a simulation of a long range impact with minimal resistance. Each on the right is a simulation of a normal range (like 250 yard) impact.

    The “long range” Scrirocco retained 88.7%, the “normal range” retained 78.2%. Great weight retention but they didn’t penetrate very far—as one would expect with them opened to such a huge diameter.

    Both XLC’s retained 99%, of course. The “normal range” XLC is what I’m used to seeing from my tests and the reason I used X bullets exclusively for so long. Absolutely perfect! It’s the “long range” one that’s disturbing. It hardly opened up. The wound channel was tiny. As you can see the shank is slightly bent. This is the only bullet that didn’t penetrate straight. About ¾ of the way in it took a 45 degree turn to the left. I could attempt to explain why with some Euler column buckling equations but I won’t. [​IMG] I’ll just show you what happened.

    The AccuBonds retained 76% and 64%.

    They don’t look all that impressive. Much the same as a Partition doesn’t look all that impressive compared with some of the “pretty” mushrooms some of the custom bonded bullets give. But Partitions always get the job done. If this bullet mimics their performance, I’ll be more than happy.

    In an impact where the XLC hardly opens up and doesn’t penetrate straight, these open up just fine and go straight. In an impact where the Scirocco is nearly turned inside-out, these hold together and penetrate farther. A pretty good compromise between the two.
     
  2. Jon A

    Jon A Well-Known Member

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    Here’s a bunch of them recovered from 2900 to 3300+ fps:

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    As you can see, they don’t look that much different. As the velocity increased, they simply got a little bit shorter and shed a bit more of their weight. Their frontal diameters remained virtually constant. At the front of the mushroom they were all right around .48”. On some of the lower velocity impacts the overall diameter was a bit more because the nose jacket hadn’t broken off or folded tightly against the shank yet. This didn’t seem to affect penetration much though. I think the area right at the front of the bullet is probably the determining factor there. But the higher velocity bullets did penetrate slightly more—the opposite of how the X and Sciroccos did. Although I would guess an impact that simulated a hard hit at close range might have increased the penetration of the XLC over the “normal range” test had some of the petals come off. I would also guess such an impact with the Scirocco would make it look like you’ve seen in other tests here—totally inside-out, without very good penetration. But that’s just my conjecture....

    Like I said before, each bullet does different things better. For the all around performer, I think the Accubond will suit me well.

    It will open up easily at extreme ranges with minimal resistance. The Scirocco is probably even better in this respect. A shot on a deer at long range clean through the lungs? I’d guess a Scirocco will do more damage and kill more quickly. That’s a good bullet for this application. I’m not so sure the XLC is. Both the other bullets are making huge wound channels before the XLC is even opened up. I don’t feel it would be a good choice for this situation.

    Elk in the ass at 20 yards? That’s what X bullets are made for. They are they obvious choice (in my test at least, I’d expect the Failsafe to be similar). Extreme penetration. The AccuBond isn’t going to do quite as well in this situation but it will beat the pants off the Scirocco—or any other “standard” bullet for that matter I’m convinced. While it won’t be an X bullet, it should get the job done. It isn’t going to flatten out like a pancake, it isn’t going to come apart, it’s simply going to expand to about 1.5 times its diameter, hold about 2/3 of its weight and keep going—much like the Nosler Partitions I used for so long.

    So, it looks--at least to me from my testing--like this bullet will be a good terminal performer in about any situation in which I could put it. Maybe not the best for that particular situation, but it should get the job done.

    Here's a pic of them all lined up:

    [​IMG]

    Of course none of this means a damn thing if you don’t hit where you’re aiming.
     
  3. Jon A

    Jon A Well-Known Member

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    Accuracy:

    Well, how’s this?

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    That group measures 2 ¾”. It was shot in variable 5-15 MPH (my estimate) crosswinds—at 400 yards. I had 7 clicks to the left dialed in. I was leaning over the hood of my Trailblazer on a couple sandbags—not exactly the "ideal" bench rest set-up. But it was good enough to tell me how accurate this load is. That’s actually the first and only group I shot from 400 with that load that wasn’t from field positions. I like to “quit while I’m ahead.” [​IMG]

    This group really made my day. I had spent most of the day getting the crap beaten out of me by the rifle while shooting shotgun patterns with the H870 load. This group told me that I had found my load, it validated the rifle’s accuracy and my shooting ability and it was a good note to end on for the day. I had one big bloody (literally) smile on my face after shooting it. Just imagine if there had been no wind and I had been shooting off a real bench? [​IMG]


    Here’s a 5 ¼” group shot in close to the same conditions as above. From 700 yards. I had 12 clicks of windage dialed in.

    [​IMG]

    Yup, it’s a bit low. I was going off the computer printout for the faster H870 load.

    I know that may not impress many here to much, but that's OK, I'm happy. [​IMG] That's why I posted the specs on the rifle and my shooting set-up--pretty much a cheap factory, light weight, hard kicking rifle being shot in much less than ideal conditions. I think I did pretty well considering....
     
  4. Darryl Cassel

    Darryl Cassel Well-Known Member

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    Excellent report on bullets, and loads.

    Did I miss the 200, 220 and 240gr Match King bullet pics?????

    Later
    DC [​IMG]
     
  5. Mysticplayer

    Mysticplayer Writers Guild

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    Great report and pictures. Always great when someone takes the time to share info and experiences.

    I too will be doing some testing with the Accubonds when the forest fires stop raging. I will be launching them from my new RUM. I will also use Retumbo and expect to be in that 3200fps range (35" barrel). No fears about the accuracy or ongame performance. Just something new to try.

    Like you, I am also suffering from inconsistent performance and H870. I believe the high ambient temps are causing most of my grief. Starts off shooting well then sprays as barrel temp goes up. Big heavy barrel so don't think that is warping.

    Thanks Ian for the samples...

    Jerry
     
  6. Guest

    Guest Guest

    Jerry--
    You can expect 3400 from your 35" barrel with the Retumbo and the 200 gr Accubond. I'm getting 3200 from a 25.5" K&P on a standard .300 RUM with 94.5 gr of Retumbo and the 200 gr AB.
    Jon--I really appreciate the info--I was wondering what the AB would in terminal performance and I am impressed. I sometimes shoot deer as close as 30-50 yards and as far out as 800 in some of our bean fields and I haven't had a SMK failure yet but the AB is just a little more insurance against shedding the jacket on the close shots and the BC is .588--good enough for shots out to 1000 with the RUM...
     
  7. Mysticplayer

    Mysticplayer Writers Guild

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    Chris,
    will find out about the vel in the future. Only getting 3000fps with H870 and 240gr MK, so 3400fps may be optimistic. Would be nice...

    I am surprised at the bc of only .588. The bullet is as long as the 220gr MK which is rated over 0.6. My guess is that companies are taking a very conservative approach to their bullet performance.

    If the Hornady SST/Amax are an example, these poly tip bullets fly flatter then their book BC would suggest. Would be interested to see how much elevation you need to go 1000yds from a 100yd zero. This would give us a ballpark on the real world BC.

    Jerry
     
  8. Jon A

    Jon A Well-Known Member

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    Thanks, guys.

    I should have known you'd say that, Darryl. [​IMG] Now that you did I'm a bit PO'd at myself. While I didn't include any Matchkings in this test, I have tested the 240 before in the same medium and I really should have included some pics. I'll try to take some (without a digital camera that means I'll have to wait until the whole roll is shot up before they can be developed). One word of warning, while they performed very well as far as the wound channel goes, what was left of the bullets isn't much to look at. But my box of 240's was on standby if these failed to shoot--I came very close after the poor results with H870.

    Jerry, yeah the temps were in the 95 degree range during all this testing. I'm sure that didn't help. But that's another vote for Retumbo that it did so well in the heat.

    I do think most of the plastic tipped bullets have underrated BC's (including Nosler's Ballistic tips) but as far as I can tell this bullet is spot on or very close to .588. It matched my charts out to 700 very well correcting for weather/altitude as well as I could. Trajectory at only 700 isn't a very accurate way to measure BC's but that's all I've got.

    Remember the length of the bullet has little to do with BC's--but weight has a great deal to do with it. If you beleive their advertised numbers, the AB has a more aerodynamic, efficient shape than the 220 SMK. But the SMK has a 20 grain weight advantage which makes it harder to slow down for the same drag force.
     
  9. rufous

    rufous Well-Known Member

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    Jon, still curious what you fired these bullets into? Maybe you stated that and we missed it. I recovered some 7mm 160 Accubonds yesterday that I fired into a cardboard box filled with dry newspaper. I shot 2 at 250 yards, 2 at 400 yards and 2 at 500 yards. They were all fired from the prone position using my Kramer snipepod. The 2 at 250 were 1.15" apart. The 2 at 400 were 2.64" apart and the 2 at 500 were 5.8" apart. The bullets looked very much like the ones you recovered. Retained weight ranged from 96 to 98 grains for an average of 60.6%. They look very much like a partition would look. I think they will be an awesome big game bullet. Rufous.
     
  10. Jon A

    Jon A Well-Known Member

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    I took some more pics:
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    That's pretty self-explanitory.
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    Here you go, Darryl! [​IMG] I've included a 240 SMK in the lineup that I tested earlier in the same medium. It retained 41% of its weight counting the jacket and core together (they were found in one piece but the core is free to fall out). All of them I recovered looked pretty much the same--expanded down all the way to their bases. I also tested the 180 XBT and Scirocco at the same time. While the recovered MK may not be as photogenic, its penetration equaled the XBT, was better than the Scirocco--and the wound channel was huge, easily the biggest of the three.
     
  11. Brent

    Brent Well-Known Member

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    Jon,

    Must have missed your post on this over here. Your Accubond in the pic you just posted looks like the one I took out of the Mooses shoulder I got last week, 133gr retained wt.

    I shot the 90gr Retumbo load some more today, 1.3" 3 shot group at 200 yards off the bipod and a crappy rear rest. You should have seen my off hand group tho, I'd of had you all rollin on the ground laughin. [​IMG] Ain't no wonder why I missed on the first shot now! Holy smokes, what a reality check!! Kept 4 out of 5 on a 9.5"x11" piece of paper and dropped one about 8" below the bottom edge. I was done when Shawn showed up with the AR-50 though. Put a few M33 balls through the Oehlers at 2745 fps and drilled some deep holes! [​IMG] Man they shoot sweet... Took Shawn a few rounds to get settled in, but after I put three into an inch at 200 yards he sure tightened his groups up trying to catch up. [​IMG] [​IMG] Muzzle brake works better than I thought tho, sky screens and diffusers didn't even twitch at just ten feet from the muzzle, I don't think I've even seen that happen before. [​IMG]
     
  12. Ian M

    Ian M Well-Known Member

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    Jon,
    Interested to hear what you are shooting the bullets into, very uniform performance. I have seen similar mushrooms when we shoot into water.
    ian
     
  13. Brent

    Brent Well-Known Member

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    Ian,

    Jon said it was dry cottonwood.

    Here's the recovered 200gr Accubond from the Moose. Went in and breaking the shoulder, passed through busting two ribs and stopped on the outside edge of the other shoulder just missing the shoulder bone on the off side. Weighed 133gr in the end.

    [​IMG]

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  14. Jon A

    Jon A Well-Known Member

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    Sorry, Ian, I guess I posted that in the thread at "the other place." [​IMG]

    The penetration tests were into wood (dry cottonwood). It isn't quite as hard on bullets as water or solid flesh. I have found this to work well over the years since you can fire a round at full muzzle velocity into it and the resulting bullet looks much like one recovered from game at 2-300 yds.

    BTW, I liked your bonded bullets article.

    [ 08-27-2003: Message edited by: Jon A ]