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Can MP 300 be substituted grain for grain for IMR (Read 1056 times)

hopkinskid Junior Member Offline ASSRA Board Member Posts: 64 Location: Hopkins, MI Joined: May 12^th, 2020	Can MP 300 be substituted grain for grain for IMR Oct 15^th, 2022 at 10:51am	Print Post
	I'm running out of 4227 and for the first time bought some MP 300. I got it for my 8.15 Aydt and .33-47 High Wall. Are they similar enough that I can expect to bracket my current 4227 loads by .5 grain below and above and be done with load development with the new powder or is that a pipe dream?


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Skalkaho Oldtimer Online Posts: 785 Location: Montana Joined: Sep 29^th, 2006	Re: Can MP 300 be substituted grain for grain for IMR Reply #1 - Oct 15^th, 2022 at 11:29am	Print Post
	J. Louis where are you? In my 38-55 using 4759/4227 were about same with 300 MP, did better with stouter load and mag primers...
	« Last Edit: Oct 15^th, 2022 at 12:27pm by Skalkaho »
	May the Bullet Gods be with you.......
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Premod70 Oldtimer Offline Posts: 864 Location: North Carolina Joined: Jan 16^th, 2016	Re: Can MP 300 be substituted grain for grain for IMR Reply #2 - Oct 15^th, 2022 at 4:04pm	Print Post
	My experience is 300MP is a little faster burning than IMR 4227. I’d start a couple grains under my standard 4227 load and go up from there.


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bpjack Frequent Elocutionist Offline Posts: 2758 Location: East Olympia, WA Joined: May 18^th, 2008	Re: Can MP 300 be substituted grain for grain for IMR Reply #3 - Oct 15^th, 2022 at 4:54pm	Print Post
	I use 300MP for breech seating only. 25-20 Win, 32-40 and 38-55. Much better groups than 4227 with the right load. Magnum primers for sure. You can reach a point where adding more powder makes little difference. If you double charge it is not near as bad as 4227. Don't ask me how I know! Jack

	ASSRA # 11318 just a bit of a hoot.
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JLouis Frequent Elocutionist Offline Posts: 10625 Joined: Apr 8^th, 2009	Re: Can MP 300 be substituted grain for grain for IMR Reply #4 - Oct 15^th, 2022 at 5:38pm	Print Post
	Skalkaho I am still here but only at times. My competitive breech seating cast bullet Benchrest shooting days are now gone. Not sure if anyone can now go back and to do a search on all of my own 300MP success's. I am pretty sure by now that everyone is now pretty much sick and tired of hearing about them all. In short is has been a very successful for myself to use and it also typically does like Large Rifle Magnum Primers.

	" It Is Better To Now Have Been A Has Been Than A Never Was Or A Wanna Be "
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JerryH Frequent Elocutionist Offline ASSRA Member #10876 Posts: 1241 Location: Easton, CA Joined: Nov 9^th, 2014	Re: Can MP 300 be substituted grain for grain for IMR Reply #5 - Oct 15^th, 2022 at 9:24pm	Print Post
	14.5 gr. of 300MP with a WLRM primer and a 231 gr. Mos bullet lubed with Javelina Schuetzen Lube breechseated worked very well in my 33-47 CPA 44 1/2 rifle. I shot my first 250 target during a practice session with this rifle/load. My powder is labeled 300MP not MP300. Make sure they are the same powder before you use my load data. Start low and sneak up on your best load.

	I'm not a complete idiot, some of my parts are missing.
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JLouis Frequent Elocutionist Offline Posts: 10625 Joined: Apr 8^th, 2009	Re: Can MP 300 be substituted grain for grain for IMR Reply #6 - Oct 15^th, 2022 at 9:33pm	Print Post
	I call it 300MP for short.. It is actually called Alliant Powder Pro 300-MP. The MP stands for Magnum Pistol Powder / Smokeless Spherical Magnum Pistol Powder.

	" It Is Better To Now Have Been A Has Been Than A Never Was Or A Wanna Be "
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hopkinskid Junior Member Offline ASSRA Board Member Posts: 64 Location: Hopkins, MI Joined: May 12^th, 2020	Re: Can MP 300 be substituted grain for grain for IMR Reply #7 - Oct 16^th, 2022 at 4:24am	Print Post
	Oops! Yes, 300 MP. I'm in SW Michigan-about 2.5 hrs north of the Beeson Range. J. Louis, your posts got me interested in 300 MP in the first place. Thanks for sharing! I've only been able to find Federal and Remington LR magnum primers so far, but I'm on the lookout for Winchesters when I find some.


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hopkinskid Junior Member Offline ASSRA Board Member Posts: 64 Location: Hopkins, MI Joined: May 12^th, 2020	Re: Can MP 300 be substituted grain for grain for IMR Reply #8 - Oct 16^th, 2022 at 4:34am	Print Post
	Jerry H: thanks for the input. I'm starting with Javelina Schuetzen Lube and am waiting for a mold and breech seater from David Mos for my .33-37 High Wall with a Ken Briesen LH twist (14") barrel. That gives me a ballpark to start with when they come. For now, I'm playing with the Aydt and trying to get a load ready for next season with 190 grain Hoch mold bullets. She's a Haenel Original Ayt and looks like she'll shoot as good as she looks.


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JLouis Frequent Elocutionist Offline Posts: 10625 Joined: Apr 8^th, 2009	Re: Can MP 300 be substituted grain for grain for IMR Reply #9 - Oct 16^th, 2022 at 8:17pm	Print Post
	I personally have never had any day in and year long consistent results with using the 4227 powder. And in my own experience the 4227 has also called for abit more powder.

	" It Is Better To Now Have Been A Has Been Than A Never Was Or A Wanna Be "
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JLouis Frequent Elocutionist Offline Posts: 10625 Joined: Apr 8^th, 2009	Re: Can MP 300 be substituted grain for grain for IMR Reply #10 - Oct 16^th, 2022 at 8:24pm	Print Post
	This is one of my 38-55 200 yard targets. Hopefully you can also see all of the load data and if not just please ask. (You need to *Login* or *Register* to view media files and links)

	" It Is Better To Now Have Been A Has Been Than A Never Was Or A Wanna Be "
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hopkinskid Junior Member Offline ASSRA Board Member Posts: 64 Location: Hopkins, MI Joined: May 12^th, 2020	Re: Can 300 MP be substituted grain for grain for IMR Reply #11 - Oct 17^th, 2022 at 11:01am	Print Post
	Thanks for sharing! I'm encouraged that a change to 300 MP is the way to go. J Louis, your posts about 300 MP in the .33-47 have been a gold mine to a noobie like me trying to start from the beginning with my own .33-47 and your .38-55 target is what my current dreams are made of. Much appreciated! I can hardly wait to post my own 250 targets!


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