Faster than imr 4064

[GhengisAhn175]

I bought 8# of imr 4064 thinking it'll be the right powder for my 16.50" 308 spittin 175 gr SMK but my velocities are barely breaking 2k at 43.0 grains and I'm starting to compress...

Would like to hear suggestions for alternatives as is like to be around the 2500-2800 fps mark as others are
Reporting while staying safe.

 

[InfScout1/69]

You shouldn't be compressed at 43 grains. You may be just hearing it when you seat the bullet. But when seated if you shake the round alittle you can hear it moving around. I start getting compressed loads at almost 46 grains

 

[InfScout1/69]

One the powder settles in the brass you have more room. Just shake it or tap it on the table alittle before seating the bullet

 

[Rhyno]

H4895 or Benchmark.

Both burn faster, I had great success with them pushing light bullets (granted my barrel was 10" longer then yours.) And loading for an auto loader.

 

[Twoboxer]

I think the other folks are steering you right . . . with Lapua brass at ~56.0gr (water) capacity and a COL of 2.800" Quickload shows ~103% fill. So it depends on your case, but you can probably shake it down shake it down for a bit more capacity.

In a bolt gun you *should* be close to ~2400 fps . . . say at least 2300+ . . . with a 16.5" barrel. FWIW, FGMM 175gr apparently uses 41.75gr IMR4064, and Quickload shows 2356fps for that load from a 16.5" barrel. If not a bolt gun, then maybe the issue is there.

 

[Road_Clam]

I bought 8# of imr 4064 thinking it'll be the right powder for my 16.50" 308 spittin 175 gr SMK but my velocities are barely breaking 2k at 43.0 grains and I'm starting to compress...

Would like to hear suggestions for alternatives as is like to be around the 2500-2800 fps mark as others are
Reporting while staying safe.

Is it possible your chrono was not reading accurately ? My chrono is very fussy to inconsistiant light conditions. Your velocities are way low compared to my #'s . I chronod' some 4064 loads and here's my data shot through my Alpha Master :

178 AMax , 4064, 41 gr. avg = 2378 fps
.
178 AMax , 4064, 42.3 gr. avg = 2637 fps

178 AMax , 4064, 42.5 gr. avg = 2688 fps

 

[UNRL Ghandi]

I was running 43.3 gr of IMR 4064 through my 18" .308 using 175 SMKs and was getting right around 2600. Same load through a 24" barrel was hitting 2750. I was using Federal GMM brass and CCI BR2 primers.

Something definitely seems off. Don't think it's the powder. Seems like it's gotta be one of the measurement tools - chrono or powder scale.

As Rhyno noted, it was suggested to me a while back to try the H4895 powder for an AR10 I had and use magnum primers. Got a little more velocity for me, but I had better accuracy out of the slower loads so I stuck with the 4064.

 

[GhengisAhn175]

Thanks for the info fellas.

It's not a bolt gun, an hk mr762 semi auto.

I don't think chrono is off, albeit it's a pro chrono but it worked just fine for my Aiax loads (2900 fps and verified with distance shots).

I hope there isn't something defective with the rifle itself... I could try different powder or just drop 50 bucks on fgmm and try that on the chrono. Haven't been able to test
This part yet and going to go camping for a week starting tomorrow. Will keep reading the thread for info/suggestions!!

 

[MLC]

8208 XBR would be a good alternative but I'd try using a drop tube and getting a bit more powder in that case.

edit
I ran it in QL and you should be over 2400fps with 43 grains unless you're using really roomy brass.
As for 2800fps, not with a 175.

 

[Road_Clam]

I'm no burn expert , but I don't see how a faster burn powder will elevate your m/v ? . I do know when I was working loads in my AR-15 , you need to choose the correct speed burn or you will encounter cycling issues. I tried 4198 in my AR and had a ton of failure to feed issues. Turns out 4198 was too fast of a burning powder. I use both Win 748 and Benchmark in my AR and the cycling and performance is excellent. I also use both of these powders in .308 , so my advice would be try Win 748 in your gas gun. Good luck, hope you get it sorted out. Here's a burn chart that might help you choose :

 

[Rhyno]

I'm no burn expert , but I don't see how a faster burn powder will elevate your m/v ? . I do know when I was working loads in my AR-15 , you need to choose the correct speed burn or you will encounter cycling issues. I tried 4198 in my AR and had a ton of failure to feed issues. Turns out 4198 was too fast of a burning powder. I use both Win 748 and Benchmark in my AR and the cycling and performance is excellent. I also use both of these powders in .308 , so my advice would be try Win 748 in your gas gun. Good luck, hope you get it sorted out.

More powder burns. In a short barrel with a slow burning powder you may be pushing powder out of the barrel before it is all burned.

With a faster burning powder more will burn.


That's the theory anyways.

 

[GhengisAhn175]

Mlc, I am using once fired m118lr brass it's military mixed. I believe it's 7.62x51 most likely and it's slightly roomier than a standard 308.

I was told that this shouldn't be the issue however but I haven't ruled it out just yet

 

[FLIGHT762]

Mlc, I am using once fired m118lr brass it's military mixed. I believe it's 7.62x51 most likely and it's slightly roomier than a standard 308.

M118 LR brass is not roomier than standard 308 brass. You have it backwards. There are several commercial brands of 308 Winchester brass that have more internal case capacity than Lake City M118 LR brass.

I'm also a believer that you either misread you Chrono or it didn't read properly. You should be getting around 2500 FPS out of your load.

 

[pawprint2]

2500-2800 FPS, with a 175 and 16.5 in tube on a gas gun-I don't think you can do it safely, 4895 has Long been known as the gas gun powder with 168's&175SMKs, the idea that your powder is too slow, just doesn't hold up to historical facts, some really "fast" powders (for a gas gun) such as 3031, may not produce enough gas at the port to run the weapon. If you are bent on the velocity, try 150SMKs and 4895, around 43.5 grains, you should be able to get there, keeping magazine length OAL, and running the gun.

 

[GhengisAhn175]

Just an update fellas:

Had a friend with an oehler and verified chronos. The Aiax was still at the 2900 mark but the hk loads I had questions on were at 2400-2500 fps.

Guess it was the chrono. Funny it worked well for one caliber and not the other.

Will keep making my fgmm clones at 41.8 gr of imr 4064 as that have me 2425 fps as an average.

 

[wxl]

Just an update fellas:

Had a friend with an oehler and verified chronos. The Aiax was still at the 2900 mark but the hk loads I had questions on were at 2400-2500 fps.

Guess it was the chrono. Funny it worked well for one caliber and not the other.

Will keep making my fgmm clones at 41.8 gr of imr 4064 as that have me 2425 fps as an average.

Had to be the chrony or the gun. Nothing wrong with the recipe or 4064 for 175 SMKs.

 

[Bender]

4064 is a fantastic powder!!!