450 LM "LeGendre Magnum"

Talk about the AR15 style rifles chambered in 450 Bushmaster.

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Re: 450 LM "LeGendre Magnum"

Postby JaredP » Thu Dec 14, 2017 9:29 am

Hoot wrote:Welcome Aboard Jared!

I also use QuickLoad and do a lot of modeling for the 450b. When comparing predicted results using W296 versus real results, it became apparent that QL gets W296 wrong in that caliber. I'm guessing it gets it wrong in the 450 LM as well. I edit the powder characteristics now when doing W296 workups to get it in line with what I see at the shooting bench. IE Dial it down. I'm at work, so I don't have my notes with me, but its quite a bit lower in practice than in theory (see sig). ;)

Hoot


Thanks Hoot, I've definitely seen your name come up a number of times in various forums as I was researching this topic.

Can you advise on what my best route is to replicate the 450LM? Should I just go off of info from this thread? Should I contact Tim as LeMag?
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Re: 450 LM "LeGendre Magnum"

Postby Hoot » Thu Dec 14, 2017 11:01 am

Tim is for all intent and purpose, retired from the scene. If I were you, I'd PM Kiwi Greg and share some correspondence with him. I gotta say though, the 230gr FMJ would be my last choice as a starting bullet. Sure they're affordable, but they're short in length, compared to the FTX and other families. In order to get adequate seating depth for neck tension, you have them seated almost to the ogive. I'm no fan of the 230fmj. I've tried them several times but any of the Hornady FTX family, SST/ML and XTP Mag bullets are much easier to work with IMHO. Get them under control and then venture into the 230fmj.

Given I have zero experience with the 450 LM, aside from trading correspondence with Tim during the development phase, I'm not the person to ask for advice. You certainly can PM Tim "Wildcatter" and see if he responds however. He did stop by the forum about a month ago, so he's still around.

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In Theory, there is no difference between theory and practice. In Practice, there is.
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Re: 450 LM "LeGendre Magnum"

Postby JaredP » Thu Dec 14, 2017 11:39 am

Thanks for the info.

Looks like I'll start with the 250 XTP or the 240 XTR MAG, which I think is rated for higher velocity and more suited for this application.

In the meantime, can you look at this QL data for the a modified 450 BM and see if I have anything wrong with my set up?

Image

I'm getting quite lower than Kiwi Greg's reported ~3070 FPS when using the 250 XTP and 65k PSI. I'm also pretty inexperienced with QL.
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Re: 450 LM "LeGendre Magnum"

Postby Hoot » Thu Dec 14, 2017 7:19 pm

Jared, QL tends to over-predict a little to keep the overambitious from harm. Not by much though. Obviously, no one in their right mind starts testing at max load. AA 1680 has been a relatively safe powder given its volume versus energy content. Another powder to consider, but hich is also not characterized by QL is the new Hodgdon CFE Black.With all due respect to the AR10 platform, I would not set the maximum chamber at 65k. Maybe in a bolt gun. There's always time to work up but rarely to work down when you've gone too far. I used QL to establish starting points for both .308 and 260 Rem in an AR10 platform, but not a straight walled cartridge that is not SAAMI approved. You'll be sailing in relatively uncharted waters, save for the load reports from folks like Kiwi Greg. No disrespect to Wildcatter, but take his load limits with a healthy dose of caution. By his own admission, he never worried about the cost of blowing up guns. We mere mortals, aka working stiffs, see life through different glasses. In theory, (see sig) either W296 or H110 would be good matchups for a 250gr bullet since they are well suited in the 450 LM's little brother. That being said, some powders behave differently at higher pressures, so the recipe that works for the 450b may not scale linearly upward just because the 450 LM case holds xx grains more powder.

I am not at all comfortable giving advice on a caliber that I've never loaded myself. If you don't mind, I'll be content to just watch you guys forge new trails. I've never created new calibers using QL, so I'm no authority as to how that'll go.

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Re: 450 LM "LeGendre Magnum"

Postby JaredP » Fri Dec 15, 2017 8:24 am

I appreciate your time Hoot. AA1680 does look like the tamest powder to start with here.. I suppose I'll just start low and work up.

As far as dies go, can I just use 45 BM dies and use the 45 colt collet FC die to put on the side crimp?

For chamber reamer? I've never done one before, so I really have no idea.
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Re: 450 LM "LeGendre Magnum"

Postby Al in Mi » Fri Dec 15, 2017 11:47 am

Check with Dave Manson on the reamer, I know he's made reamers for Tim in the past.

Full length sizer die might be a issue, not sure if the 450 die will be long enough.
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