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Thread: Barnes MRX Loading tips...

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    Default Barnes MRX Loading tips...

    Well, today's shooting session invloved five different guns and my chronograph. All went very well and one of the tests was the Barnes new MRX (It should be called the MR$$$ bullet). Twenty bullets retail for about $25.00.

    I used a very well proven rifle an old 30-06 Dakota model 97 with 24" super smooth barrel. This rifle will typically send 180 grain bullets at 2800 + fps with a relatively mild load. I started with a proven powder, brass, primer combination and here are the results. The Partition load is a test load for reference. It had been used before and I included both old and new ammo loaded with this combo to compare with the MRX load.


    All Loads were with Lapua brass and Federal-210M (match) primer. Velocities are average of five shots, 15' from the muzzle. All bullets were seated .025" off the lands. Cartridge OAL was 3.305"

    Nosler 180 grain partition spitzer.
    (old load) Fired last year.
    H4350 56.0 grs. 2816 fps, sd=13

    (new load) Fired today.
    H4350 56.0 grs. 2820 fps, sd=11

    180 grain MRX
    H4350 54.0 grs. 2728 fps sd=12
    H4350 55.0 grs. 2774 fps sd=10
    H4350 56.0 grs. 2802 fps sd=15

    The 55.0 grain load was shot for accuracy with five shots going into .8" in two minutes, from the sand bags. The last five of 25 shots. I only had 20 MRX bullets and loaded 10 of the middle load, guessing it would be the best performer. Judging by the sd numbers it was. Another hint here is the 46 fps gain from 54 to 55 grains and only 28 fps gain from 55 to 56 grains, the max load here is the 56.0 grains. I would now try 55.5 grains and it would likely be the best. There were no pressure signs detected with the 56.0 grain load but I'm at the knee of the pressure vs velocity curve as evidenced by the short gain in velocity with the last one grain increase.

    This rifle has two very obvious talents; It is fast, very fast (due to the very smooth barrel) and it is very accurate. (I did not shoot the partition load on target today but it is truly a .5 MOA load.) It also doesn't care whose bullet it is or if it's barrel is very warm. I could touch the barrel to my face after the fifth shot, it was not hot.

    I don't have TSX data to compare this with so make your own guess. The MRX is something other than lead in the shank and it has the TSX grooves around the bullet.

    Just a little loading tip for your shooting pleasure.
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    Default Thanks for the info...

    Thanks for the post professor. It will make a good reference in the archives. The MRX is intriguing, but I have not (yet) taken it for a test drive...I don't think I could keep up with the payments that come with this pricey rig. One of my friends is in the process of developing an MRX load for a 300 RUM, but I haven't heard of his progress. I'll ask him.

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    Thank you for the info. I was thinking about getting some for my 280 but still cant get over the price of them. Maybe I'll scratch enough together to buy a box and try them out.

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    Thumbs up 30-06

    MRX 180gr
    56.0 of IMR 4350
    Fed 210M
    FC Nickle Case
    Alaska

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    Member 8x57 Mauser's Avatar
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    Jeff,

    What kind of velocity does that load give you?

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    Thank you for the through research. How do you know the distance from your bullet's ogive to the lands? I have never been able to do this satisfactorily. Thanks. J.

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    Quote Originally Posted by OldRgr View Post
    Thank you for the through research. How do you know the distance from your bullet's ogive to the lands? I have never been able to do this satisfactorily. Thanks. J.
    I partially resize (about 1/8") a case then, without powder or primer, seat a bullet in it about 1/4". I smoke the bullet black with a candle then chamber the round. It should be too long and will require a little push to close the bolt. The bullet will run against the rifling and be pushed into the case. Now extract the round carefully and observe the marks from the lands of the rifling. Measure this overall length. This is the contact length for this particular bullet. (Do this three times and get a consistant measurement.) Write this contact length down in your log for this bullet and this rifle. Now when loading ammo with this bullet for this rifle, seating the bullet with an overall length .025" shorter is than this contact number is .025" off the rifling.

    A handier and easier way to do this is to use a Stoney Point case length gage and a modified case for your caliber. Simple to use and more consistant results. Actually works great.

    A note on the above technique; Sometimes the bullet will stick in the throat, jammed into the rifling, just punch it out with a cleaning rod and do it again. You will need a 6" dial/digital caliber to do this measurement.
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    Thanks; appreciate it greatly. J.

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    Default Ballistic Advantage?

    Since the core of this bullet is denser than lead, I take it the bullet length would be shorter than a lead core. Is a shorter bullet of comparable weight an advantage or a disadvantage ballistically?

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    Quote Originally Posted by Sako Workhorse View Post
    Since the core of this bullet is denser than lead, I take it the bullet length would be shorter than a lead core. Is a shorter bullet of comparable weight an advantage or a disadvantage ballistically?
    Yeah, kind of, if you want to split some fine hairs.

    Sectional Density is the bullet weight in pounds divided by the square of the diameter. (SD= W(lbs)/d*d. The BC of a bullet is the SD * a form factor or shape coeffecient. Basically how stream lined the bullet is. This shape, however, has nothing to do with length. So...longer ain't better in flight, in fact longer bullets require a faster twist rate in the gun to stabilize so are a disadvantage if not of pure lead. Copper or gilding metal jackets, or non lead cores or alloyed lead cores for any given weight and caliber are detrimental to this twist requirement. Fortunately, all so very slight as to not be considered unless the bullet is pure copper, then it's length will be considerably longer and twist rate may be a consideration. If the bullet is of aluminum or titanium, we would need to redesign the gun.

    With the MRX the core is not more dense than lead, (try to find an element heavier than lead), it is more dense than pure copper so it is shorter than the TSX but longer than a lead core. I think the MRX core is a bunch tougher than lead, though.
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    Default Tungsten!

    If I am understanding correctly, the Barnes MRX bullets have a tungsten core, which is approximately 1 1/2 times denser than lead.

    Specific gravity of lead = 11.34
    uranium = 18.7
    tungsten = 19.25

    I am wondering if this might not have a significant effect on the ballistics.

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    Default Densities and ballistics

    How timely - I visited a couple today with a 'periodic table of the elements' shower curtain.

    While Tungsten may come before Lead, it's more dense. Several things are. Some of those things may even have ballistic uses. One that may is the big W (that's Tungsten, of course, not a comment on the current occupant of 1600 Pennsylvania Avenue). By contrast, you wouldn't get much benefit from Iridium, even if it is quite dense.

    I can't bring myself to shell out for tungsten shot for ducks, but if the advertisers are to be believed, it's alloyed so as to be both more dense than lead and almost as malleable.

    I haven't ever gotten my hands on the MRX, but I'm guessing the tungsten backside is an attempt to make up for the tremendous length of Barnes' all-copper TSX, which, with the comparatively low density of copper and those grooves in the shank, has to be reeeaaalllly long in .308 to weigh 180 grains. The boattail just adds to that difficulty. The MRX's plastic tip is another lengthening luxury the tungsten affords.

    So I'm guessing here, but I'll wager the MRX is about the same length as a traditional lead bullet of comparable weight, or at least no longer than the old-fashioned X bullet.

    What I don't know is whether all that weight in the bullet's rear end causes instability in flight. Or, for that matter, in game. As a matter of physics, is the MRX's butt too big?

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    Quote Originally Posted by Sako Workhorse View Post
    If I am understanding correctly, the Barnes MRX bullets have a tungsten core, which is approximately 1 1/2 times denser than lead.

    Specific gravity of lead = 11.34
    uranium = 18.7
    tungsten = 19.25

    I am wondering if this might not have a significant effect on the ballistics.
    Oh, yes, and don't forget gold at 19.2 and plutonium at 19.84 at osmiun at 22.6.

    I meant an element (metal) that can be formed into a bullet. Gold and plutonium can be but not necessarily make the best bullets. Tungsten (W) cannot be formed into a bullet. The tungsten shot and bullets are powdered tungsten formed with a thermo-plastic polymer (also very heavy) to hold it together. It is not pure tungsten it is actually called Technon-this plastic/tungsten core formed with heat and pressure and would be a good core for a solid. (Basically it is some powdered Tungsten and glue.)

    Interesting side note:
    A solid tungsten rod, encapsulated in lead then jacket with gilding metal jacket was used for bullets in M-16 , 5.56 military ball ammo. This 69 gr. M855 "penetrator" round required a faster twist barrel and had it's share of problems but fullfulled a specific military "need".

    This new Barnes "tungsten core" does not deform easily and expansion is not to be had for such a "solid" conglomeration of a concrete like substance. It is not very compressable and must have a very thick pure copper jacket on it to allow it to be swaged down the barrel. This core is NOT 1 1/2 times heavier than lead. It also leaves the worst clean up job of any bullet material, this copper clad "tungsten". I also think this core would make worse the tendency of the other X bullets to "upset on impact" due to heavier rear section. It would swap ends easily if it failed to expand. One helluva bullet there!

    So if it is your belief that it is at least 1.5 times better than a plain old lead bullet then you make a good customer for Barnes. So it really wasn't a question just something to discuss. Ok, you win I was wrong there is a better bullet material than lead.

    Here are some more meaningful numbers.

    Bullet lengths all .308" diameter and 180 grains. These were on my bench.

    Swift Scirocco 1.430" (The longest 180 grain .308" lead core bullet, ever)
    Barnes MRX 1.365" (Is this shorter than the TSX?, it's shorter than the scirocco)
    Barnes TSX (??, don't got one to measure)
    Nosler Partition 1.180"
    Norma Oryx 1.235" (this one is 200 grains)
    Norma Vulcan 1.165"
    Swift A-frame 1.215"
    Lapua Mega 1.145" (this one is 185 grains)
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    Default

    Here are some more meaningful numbers.

    Bullet lengths all .308" diameter and 180 grains. These were on my bench.

    Swift Scirocco 1.430" (The longest 180 grain .308" lead core bullet, ever)
    Barnes MRX 1.365" (Is this shorter than the TSX?, it's shorter than the scirocco)
    Barnes TSX (??, don't got one to measure)
    Nosler Partition 1.180"
    Norma Oryx 1.235" (this one is 200 grains)
    Norma Vulcan 1.165"
    Swift A-frame 1.215"
    Lapua Mega 1.145" (this one is 185 grains)
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    ...the 180 grain .308 TSX (BT) is 1.388"

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    Quote Originally Posted by Doc View Post
    Here are some more meaningful numbers.

    Bullet lengths all .308" diameter and 180 grains. These were on my bench.

    Swift Scirocco 1.430" (The longest 180 grain .308" lead core bullet, ever)
    Barnes MRX 1.365" (Is this shorter than the TSX?, it's shorter than the scirocco)
    Barnes TSX (??, don't got one to measure)
    Nosler Partition 1.180"
    Norma Oryx 1.235" (this one is 200 grains)
    Norma Vulcan 1.165"
    Swift A-frame 1.215"
    Lapua Mega 1.145" (this one is 185 grains)
    __________________
    Murphy
    *****************************************

    ...the 180 grain .308 TSX (BT) is 1.388"
    Thanks, Doc. I should have guess you'd have those old obsolete bullets layin' around. I guess we need to compare all the poly tipped super sharp spitzers to the MRX, not the soft noses. Anybody have any old Nosler Ballistic tips? AccuBonds? Hornady SST? Anything with this tip is longer. I s'pose the heavier core allows the use of the tip without sticking the bullets out the barrel, as 8X57 pointed out. I'm going to cut one of this in half length wise and get some pics. I dunno what's in there.
    Last edited by Murphy; 02-23-2008 at 12:01.
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    Quote Originally Posted by 8x57 Mauser View Post
    How timely - I visited a couple today with a 'periodic table of the elements' shower curtain.

    While Tungsten may come before Lead, it's more dense. Several things are. Some of those things may even have ballistic uses. One that may is the big W (that's Tungsten, of course, not a comment on the current occupant of 1600 Pennsylvania Avenue). By contrast, you wouldn't get much benefit from Iridium, even if it is quite dense.

    I can't bring myself to shell out for tungsten shot for ducks, but if the advertisers are to be believed, it's alloyed so as to be both more dense than lead and almost as malleable.

    I haven't ever gotten my hands on the MRX, but I'm guessing the tungsten backside is an attempt to make up for the tremendous length of Barnes' all-copper TSX, which, with the comparatively low density of copper and those grooves in the shank, has to be reeeaaalllly long in .308 to weigh 180 grains. The boattail just adds to that difficulty. The MRX's plastic tip is another lengthening luxury the tungsten affords.

    So I'm guessing here, but I'll wager the MRX is about the same length as a traditional lead bullet of comparable weight, or at least no longer than the old-fashioned X bullet.

    What I don't know is whether all that weight in the bullet's rear end causes instability in flight. Or, for that matter, in game. As a matter of physics, is the MRX's butt too big?

    8X57 Mauser,

    Thanks, I should have let you handle this one, you did a good job. It seems a net gain of one plastic tip and .023" shorter for the MRX.
    Last edited by Murphy; 02-23-2008 at 12:02.
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    Default A New Variable?

    Thanks everybody for the information. Very helpful as usual!

    As 8x57 MAUSER suggests, it seems that with these modern bullet designs there might be a new variable that could affect a bullet's ballistic path -- not just sectional density and ballistic coefficient, but now the center of gravity. In other words, what is the vulnerability of a bullet to start tumbling in mid air because the heavy rear end is less vulnerable to wind resistance than the very light front end, causing its butt to want to pass its nose as the bullet slows down. (It makes for an interesting mental image and offers lots of opportunity for off-color jokes). I suppose the spin will prevent the tumbling in air, but I will be interested to hear how these bullets work out on the range and in the field for long distance shots as their velocity slows down.

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    Default Hornady .308 Interbond 180 gr. Length

    Just to add one more piece of data to the above bullet lengths:

    Hornady Interbond (ballistic tip) 180 gr. = 1.377 inches

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    Quote Originally Posted by Sako Workhorse View Post
    Just to add one more piece of data to the above bullet lengths:

    Hornady Interbond (ballistic tip) 180 gr. = 1.377 inches
    We haven't measured them all but it would seem the MRX is the shortest of all the poly tipped bullets, I would see no ballistic advantage to shorter or longer but do have some concern about the rearward CG if that in fact is an issue with this bullet.

    As for accuracy, I've shot these bullets in three guns now since my original post and I've handloaded them for others. In two very good shooting 30-06 rifles it was the worst group ever recorded for both of them and I have a few left over in 300 win mag brass and they were also the worst that rifle has ever fired. Worse than the TBBC which it hates. About two inches, each for two three shot groups. The '06's both shot them into less than an inch but they typically shoot partitions into a half inch or less. One of these rifles also shoots TSX's into a neat 1/2" triangle, but don't tell Doc.
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    Default It rained this morning...

    ...so I couldn't go outside to play (shoot). I cut a 30 caliber 180 grain MRX bullet in half length ways. This was done as I have done with several other bullets with a dremel and an abrasive wheel. Geez! This thing is hard. The Tungst-a-loy substance is very hard and caused a lot of heat to be generated. The bullet got so hot it melted the glue that held in the poly tip and it popped out. I tried to get it cleaned up and will take a picture when I find the digital. I cut it so that actually half is left which made cutting into the other half, due to the width of the cut. Taking the thin half of the shank, I bent it in the vise and the core crumbled but was kind of stuck in the shank, bonded or just stuck under the pressure of forming, I can't say for sure but the heat of the cut did melt what looks like lead at the top of the core. Maybe just the bonding agent (glue). The solid copper front half is not formed in segments, there are no petals and the nose isn't scored to initiate expansion. This copper billet has a hole reaching down the center about .400" the upper .250" larger with the poly tip stuck in it. This tip is intended to initiate expansion but I'd say since the copper is much tougher than the tip, the tip would be destroyed trying to expand the copper. This copper is not soft annealed copper. I did bake the epoxy out of this "hollow point" and the tip fell out but I super glued it back in.

    This is a very tough bullet. This bottom half is similar to the A-frame and partition, except the nose is solid CU. Very much like the TBBC's but the core in the TBBC is bonded and it is hardened lead alloy. If these weren't so pricey they would be worth a test for a hybrid solid/expanding bullet. That's the way I see the TBBC. If the nose expands, they'll be OK, if not they'll tumble pretty bad. I would expect lots of penetration from these bullets but little or no expansion. Based on what I've seen in other bullets , those I've disassembled and used on various game at various velocities, we would need to keep impact velocities above 3000 fps to see any expansion. If it were shaped correctly it would make a very good solid, oh, but Speer already did that, didn't they.
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