If IMR4064 works so well in .308 .......

[Dan Boone]

I know a bunch of .308 shooters that are sold on IMR4064 in their rifles. That seems to be an acceptable (if not preferred) powder for that caliber.

I load for a .243 as well as a 7mm-08 and they both do extremely well with IMR4064.

All that being said, I have a 6.5 Creedmoor and the general consensus is that H4350 is the "preferred" powder, and IMR4064 should only be used with 120 weight bullets or lighter.

Unless I am horribly mistaken, aren't the 243, 308, and Creedmoor all basically the same case with different sized necks? And if that is the case, then why would there be a general opinion that IMR4064 shouldn't be used with 130 and 140 grain bullets in the Creedmoor?

I haven't done any loading for the 6.5 with anything other than H4350, and am having acceptable results with it. But I have a large amount of IMR4064 on hand and if I could use it on the Creedmoor it would eliminate a powder that I have to keep on hand. Before I waste bullets, powder, and time I wondered if anyone here could shed a bit of light on this?

 

[shoot4fun]

If you don't mind a lot slower velocity at max pressures then go ahead and use IMR4064 in your 6.5CM. If you check Hodgdon.com has data for the 6.5CM and IMR4064 all the way up to the 140/142 weight range. It will work with the heavies but better for the lower weight class of bullet.
It just appears to me that you would be handicapping the capabilities of the cartridge (Yes, I own two & regularly shoot them at long range) by using a less than optimal powder.

 

[Dan Boone]

Don't get me wrong ........ I don't want to handicap the rifle. I'm just trying to understand the reasons for the differences between the CM and the 308 since the 308 seems to do just fine with 4064? Aren't the case capacities very similar? What am I missing here? Does the neck diameter difference change the powder preferences that much? And FWIW I'm not trying to stat a debate or such, just trying to understand this. Thanks for your reply.

 

[Tim Singleton]

Case volume to bore diameter ratio

 

[Zero333]

My best attempt to explain is as follows..........

Blow air through a very thin straw and then through a very fat (say 3" in diameter) straw. You will never be able to create very much pressure inside your mouth when blowing through the extremely fat straw. But with the thin straw you can pop your eyes out with the pressure you create. Think of the cartridge case just like your mouth blowing air through a straw. If you try to blow really fast and hard through the thin straw you will pop your ears and eyes out, so you moderate the speed at which you create and release the pressure. Just as a slow burning powder does when trying to push all that gas through a small opening.

 

[Dan Boone]

That's a very good example/explanation, and I thank you. I guess that I just couldn't get my head around the LARGE differences in pressures going from .300 to .264. I've been reloading for many years, but some of the technical stuff goes over my head at times. But I've never strayed from safe reloading practices. So I'll just continue to load my H4350 and be happy.

 

[shoot4fun]

Yes, very good explanation. A long time ago I loved using WW 748 in my 308 and 7MM08. The first 243 I owned I thought it would work well there too but could find no data. I finally called Sierra tech and they gave me the short answer. It wouldn't be safe to use in 243 as pressures got too high too fast. If you look at Hodgdon data you see that the max velocity on IMR4064/140 combo is only about 2500 FPS and pressure is shown as one of the highest for all powders with that combo. Any way you slice it you give up 250+ FPS to be the choice. BTW, I know a lot of people use IMR4064 for 308 but I don't think it is the optimal powder for highest velocities there either.
Any how, best of luck developing loads for your 6.5CM. It is, in my opinion, a truly great cartridge.

 

[boltman13]

IMR4064 is a great powder for 308 especially semiautos as it generates the right gas port pressure for them. It is a bear to use in a powder meter due to it's size. Weighing charges takes time but it does give great results. The other problem is that it is more temperature sensitive than Varget, the go to powder for 308 these days.

 

[swadiver]

IMR4064 is a great powder for 308 especially semiautos as it generates the right gas port pressure for them. It is a bear to use in a powder meter due to it's size. Weighing charges takes time but it does give great results. The other problem is that it is more temperature sensitive than Varget, the go to powder for 308 these days.

+1

 

[racesnake]

Ive had 2 creedmores, an AR10 and a bolt gun, and both were one trick ponies as far as powder goes. It was H4350 or nothing. I tried several other powders but nothing worked like H4350.

 

[Ned Ludd]

My best attempt to explain is as follows..........

Blow air through a very thin straw and then through a very fat (say 3" in diameter) straw. You will never be able to create very much pressure inside your mouth when blowing through the extremely fat straw. But with the thin straw you can pop your eyes out with the pressure you create. Think of the cartridge case just like your mouth blowing air through a straw. If you try to blow really fast and hard through the thin straw you will pop your ears and eyes out, so you moderate the speed at which you create and release the pressure. Just as a slow burning powder does when trying to push all that gas through a small opening.

Zero, sorry but can you explain this one more time? I couldn't finish reading it the first time picturing your eyes bulging out and your ears wagging back and forth as you were blowing through the thin straw .


Seriously, a very good analogy!

 

[waldo1979]

IMR4064 is a great powder for 308 especially semiautos as it generates the right gas port pressure for them. It is a bear to use in a powder meter due to it's size. Weighing charges takes time but it does give great results. The other problem is that it is more temperature sensitive than Varget, the go to powder for 308 these days.

^^ +1.

I haven't had much luck with 4064 with mid-heavy bullets (e.g. 175gr) in bolt guns. Varget has always produce better results for me.