300 bo

[fiver]

be quick on the sprue cut.
i recommend a 2 cavity mold and only using one of them... jus sayin.

 

[popper]

IMHO the reason the slower twist doesn't do better is the case capacity and the powder. Can't get enough powder in the case to get the needed pressure curve to get the higher fps where a slower twist would have an advantage with heavier bullets. Seems like the 300 Hamr is 'tuned' to 125gr range. IIRC DJ did the same with the 40WT. I pushed a very hard, high Cu alloy PB 145gr to 2150 fps in 1:10 18" BO carbine AR - gave a nice inch dia. circle @ 100 yds on the target. Gas cutting the base on the port. Haven't tried it with a GC version - something to do. And CFE black seems to be the best powder. Don't have any!

I get really good accuracy @ 2300 fps, 110 Vmax and H110, both 1:8 & 1:10.

 

[300BLK]

I think Popper's results with plainbase bullets in a gas gun is remarkable. I won't do it, powder coated or not. Lee 155s at 1900+ are normal loads for mine.

 

[popper]

It was just an alloy experiment but did educate me on some stuff. First AR BO I bought was supposed to be 1:9 but was really 1:7. 1:8 or 1:9 should cover all the bases for any supers.

 

[Mainiac]

I've been shooting 8" twist 300BOs since 2014, and have shot cast exclusively. Most shooting has been done with the Lee 155 and TL160, both lubed and cast. The 8" twist is no issue for running either of those bullets full speed. I have friends who also have 300BOs, 7", 8", and 10" twist. We've shot lighter and heavier bullets, all supersonic, and the 8" twist doesn't seem to be a hindrance. The 10" twist barrel was ordered and expected to be superior, but hasn't shot cast AS WELL as his 8" twist Hardened Arms.

I bought a 12 twist Wilson 7.62x40 thinking it would be superior due to "kinder twist" and 5-6gr increase in powder capacity, but it has yet to prove its worth in either regard. Velocity increase is minimal, and accuracy hasn't been as good. The 300Ham'r was designed for jacketed bullets, so expect more of the same.

As for a longer barrel in 300BO. There is only modest velocity increase in barrels beyond 16". Spend some time on the 300 Blackout forum and you'll see that some folks have spent a lot of time getting the most from the 7.62x35. Some guys are experimenting with as quick as 1-5" barrels!

Thanks for the info!!!
So,a 8 twist will shoot well,up to around 2100fps,with cast?
Where does the 300bo crap out,as far as speed? Thanks

 

[300BLK]

I haven't chrono'd my 140s, but suspect they are close to 2100fps. 160s at 1920fps held accuracy to at least 500m, so what do you need the load to do?

110Vmax will go 2400fps, maybe a bit faster in 16", but I suspect heavier bullets will fare better beyond 200 yards.

If you're going to shoot supers only, go with 8 twist and carbine gas. Pistol gas will need an adjustable gas block.

 

[fiver]

all the 110's start giving up the ghost around 200yds.
they simply are too stubby and start wandering.... bunch of little animals out there that are probably still confused and thankful for that happening...LOL

 

[popper]

Series	9​	Shots:	4​	150 GD jax	19.1 cfeblk
Min	1757​	Max	1890​
Avg	1836​	S-D	59.2​
ES	133​
Series	Shot	Speed
9​	1​	1757​	ft/s
9​	2​	1828​	ft/s
9​	3​	1890​	ft/s
9​	4​	1872​	ft/s
----	----	----	----
Series	10​	Shots:	1​	145GC	16 H110 HT
Min	1624​	Max	1624​
Avg	1624​	S-D	0​
ES	0​
Series	Shot	Speed
10​	1​	1624​	ft/s
----	----	----	----
Series	11​	Shots:	1​	145GC	15.7 rx7 AC
Min	2009​	Max	2009​
Avg	2009​	S-D	0​
ES	0​

Some chrony data, 18" carbine. Some loads I tried, none trying for max.
150 SP turned some good numbers too:
2260 avg, ES=12 IIRC, H110. Have to look for cfeblk as I have some chrony data for it, didn't remember using it all.

 

[Mainiac]

I haven't chrono'd my 140s, but suspect they are close to 2100fps. 160s at 1920fps held accuracy to at least 500m, so what do you need the load to do?

110Vmax will go 2400fps, maybe a bit faster in 16", but I suspect heavier bullets will fare better beyond 200 yards.

If you're going to shoot supers only, go with 8 twist and carbine gas. Pistol gas will need an adjustable gas block.

To tell truth,,ive only ever owned 1 ar,,and that is a 350 legend.i avoided the stupid plastic brass chuckers,for years!!!
Then for reasons i still dont know,i bought one.and found out that they are enjoyable to shoot.now,i find myself wanting a new play toy,and thought a .30 would be intresting.
Havent shot jacketed bullets in years.
The 350 will drive a 212 gr bullet 2200fps,but its very accurate down between 16 and 1800fps.
Im assuming the 30 would be similar.
I was thinking the 15 twist of the 300hamr,would allow it to shoot small groups,at wide open speed.

 

[300BLK]

Series	9​	Shots:	4​	150 GD jax	19.1 cfeblk
Min	1757​	Max	1890​
Avg	1836​	S-D	59.2​
ES	133​
Series	Shot	Speed
9​	1​	1757​	ft/s
9​	2​	1828​	ft/s
9​	3​	1890​	ft/s
9​	4​	1872​	ft/s
----	----	----	----
Series	10​	Shots:	1​	145GC	16 H110 HT
Min	1624​	Max	1624​
Avg	1624​	S-D	0​
ES	0​
Series	Shot	Speed
10​	1​	1624​	ft/s
----	----	----	----
Series	11​	Shots:	1​	145GC	15.7 rx7 AC
Min	2009​	Max	2009​
Avg	2009​	S-D	0​
ES	0​

Some chrony data, 18" carbine. Some loads I tried, none trying for max.
150 SP turned some good numbers too:
2260 avg, ES=12 IIRC, H110. Have to look for cfeblk as I have some chrony data for it, didn't remember using it all.

those RL7 and H110 velocities look to be transposed

 

[CWLONGSHOT]

Load some ZINC last nite!

IMR4198 - cci400 and a lyman 311332 bullet cast in ZINC. WAS 180g now is 113g, sized .309 seated 2.105

Loaded with 180g Data in fully prepped JAG case.

 

[popper]

They might be, I annotated after the fact. Don't have any cfeblk left, guess I used it all. Those zinc's should go real fast. IRC Ian was doing that for 223?

 

[300BLK]

zink might go fast with the right powder, but 4198 ain't it

 

[300BLK]

They might be, I annotated after the fact. Don't have any cfeblk left, guess I used it all. Those zinc's should go real fast. IRC Ian was doing that for 223?

I was looking specifically at the H110 and RL7 numbers; they appear transposed.

 

[popper]

Yes RL7 & 110 probably, I added that to the magnetospeed xls and probably did error.

 

[CWLONGSHOT]

Im not after speed with ZINC. Im looking for a good prospect steel mold of about 150g to have some ZINC cast from.

 

[CWLONGSHOT]

Any experience with Sierra 125 Game Changers?

I picked up 200 ta try in the HAM'r.

But man there profile makes for compressed loads trying to maintain 2.260.

CW

 

[popper]

125gr TGK? Yup, lots of bearing surface on that one. Better choice would be the 125SST, unobtanium.

 

[300BLK]

Any experience with Sierra 125 Game Changers?

I picked up 200 ta try in the HAM'r.

But man there profile makes for compressed loads trying to maintain 2.260.

CW

and there is the drawback to the 300 Ham'r, magazine length is a limit to powder capacity due to ogive length

try a Duramag 350 Legend mag for more length

 

[CWLONGSHOT]

125gr TGK? Yup, lots of bearing surface on that one. Better choice would be the 125SST, unobtanium.

I have a few boxes of 125 SST I find them fragile @ 2200 fps in Blk Out on Whitetails. In lung shots they are devastating. On bigger bones iffy.