300 Norma Improved 35 degree
- Thread starter Alex Wheeler
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Ledd Slinger
Silver $$ Contributor
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I think that 0.2750 freebore is a compromise between the 230gr and 245gr Berger, what freebore would one need to order for a dedicated 245gr LRHT set up?
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Teflon
Silver $$ Contributor
What is your load data for 220LR with N565? Also length of barrel?
Thanks.
Im also curious if H1000 is to fast for 245LR in 300NMI?
I have 2 29in and 1 30 inch barrel. 2 8s and 1 9. I haven't settled on a load been fighting issues so hopefully I can get one close.
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I'm going to retest the 81.5 load to make sure it holds up and test at distance. I did order some 245 to play with too.
Also it seems like I'm getting more speed with less powder than others.
Ledd Slinger
Silver $$ Contributor
Maybe, but those speeds are pretty low for the NMI. Using a 29-30" barrel, you should easily be able to hit 3200+ fps with the 220gr Berger. But you may have to switch to a slower powder.
My latest 300 NMI will run the 220gr and 230gr Berger both up around 3200 fps from a 27" barrel with 10" twist using 92.3 gr of N570. With your long 29-30" barrel, those speeds should be a breeze with the same bullets.
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Unfortunately I have n565 and I'm pressuring out faster than I expected. I can get up to 3150 but it's sticky at 85.5 grains. But I had some issues that I had to work out. I need n570 which I plan on grabbing some later but I have so much n565 that I will use it up before switching. Even with n565 I see guys running 3100 to 3200 but not having such luck. Mine is for elr matches so I'm not trying to push the edge of pressure.
Ledd Slinger
Silver $$ Contributor
How many rounds are on your barrel(s)? Might be that it's not broke in yet. Usually somewhere around the 100 round mark your barrel should speed up. How much depends on a lot of factors in the barrel internal dimensions, twist, finish, and perhaps even the molecular structure of the steel. Sometimes barrels don't speed up much, but sometimes it can be fairly significant.
I know N570 will push the 220gr much faster than any powder in the h1000/N565 burn rate area. My last NMI with a shorter 26" barrel and 9" twist could push the 220gr up around 3180 fps with no pressure signs using N570. I would personally say that anything heavier than 215gr should be propelled by a powder with a slower burn rate than H1000, "IF" you are looking for high speeds. If only concerned with accuracy, then of course N565 should do fine with 220gr and heavier bullets.
N568 has shown promise as well and some guys like it for accuracy, but it won't give the speed of N570.
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This barrel is at like 180ish. I had some pressure issues and had to figure that out I might be able to go higher now but haven't tried. Those are amazing speeds and wouldn't mind those lol
Ledd Slinger
Silver $$ Contributor
Yeah N570 is definitely the King for speed in the 300 NMI.
Ledd Slinger
Silver $$ Contributor
@schw15 , I was just thinking...
When I tested N568 in my current NMI with the 220gr with as much powder as i could stuff in the case, I still didnt get great speeds, but I started seeing erratic speeds and signs of unburnt powder in my barrel as well. That told me I wasn't getting a complete burn so it was never gonna go faster.
N568 is a very slow burning powder, slower than N570, but if you have a 30" barrel, it might allow for a more complete burn which could result in some good speeds with N568. So might want to check that out as well, especially if you want to do testing with the heavy 245gr.
When I tested N568 in my current NMI with the 220gr with as much powder as i could stuff in the case, I still didnt get great speeds, but I started seeing erratic speeds and signs of unburnt powder in my barrel as well. That told me I wasn't getting a complete burn so it was never gonna go faster.
N568 is a very slow burning powder, slower than N570, but if you have a 30" barrel, it might allow for a more complete burn which could result in some good speeds with N568. So might want to check that out as well, especially if you want to do testing with the heavy 245gr.
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Yes that is a good idea specially for the heavier 245. Have you seen a lot of barrel wear with n570? Or faster throat wear
Ledd Slinger
Silver $$ Contributor
Not enough to concern me with the amount of rounds I will put on the barrel as a hunting rifle. I don't really concern myself with barrel life on hotrod cartridges that move heavy for caliber bullets at such fast speeds. It will never last as long as a 308 win and that's just the nature of the beast. When the barrel wears out, I'll just set it back or get a new barrel.
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