Heavy bullets in 30 BR

[FilippoMo]

I wonder if anyone tried heavy bullets up to 155 grs in 30 br ,what to expect accuracy and velocity wise
sincerely
Filippo

 

[bfr 4570]

I shot some 165s out of a 30 Bellm (30 Dasher with short neck). They where for fire forming. They went good to about 300 yds. Then they started falling out of the sky.

I wouldnt want to shoot anything except paper apast 250yds.

 

[Hombre0321]

While waiting on a new barrel for a F-Class rifle build on my Farley Actioned rifle I shot the 30BR for 6 months at the mid range distance of 600 yds. I tried every bullet I could stuff into the 30 BR case. The bigger bullets at 155 grains did not do well at all out of the 17 twist barrel. I really struggled with this cartridge shooting it at a distance it was never intended to shoot at.

I did finally get it to shoot at 600 yds but it took very good conditions to do that. I ended up shooting a Custom bullet made by Micheal Turner that weighed 125 Grains. These shoot very well at that distance on those good days. The heavies just would not work at all with the small boiler room of the 30BR.

Roland

 

[FilippoMo]

My barrel has a 1 in 12" twist so there should be no issue with stability.Any recoded velocity?
The 30 Bellm has a neck of the same lenght as the 6 Dasher?
Thanks
Filippo
I will be shooting paper at 300 metres

 

[bfr 4570]

OAL form Bellm is 1.4" neck is very short.

 

[Laurie]

The bigger bullets at 155 grains did not do well at all out of the 17 twist barrel. I really struggled with this cartridge shooting it at a distance it was never intended to shoot at.

Roland,

that's not the fault of the cartridge, but of your using 155s in a completely unsuitable twist rate. The shortest of the 155s, the original Sierra MatchKing has a Stability Coefficient (Sg) of 0.95 at 2,500 fps from a 1-17" twist barrel under standard ballistic conditions. 1.0 is theoretical bare stability and 1.4 is the recommended minimum value to cover all weather and atmospheric conditions. So, at 59-deg F and 29.92 inches mercury atmospheric pressure, you would expect this combination to put the bullets through the target sideways and produce an unimpressive group at 100 yards - never mind 600!

Miller's formula says you'd achieve 1.00 at 87-deg F air temperature still at 29.92 inches Hg, so if you were shooting on a hot day and with low atmospheric pressures such as being at a considerable height above sea level, you could expect marginal stability. However, a combination that is marginally stable at 100, is likely to be marginally or perhaps more than marginally, unstable at 600.

 

[Hombre0321]

Laurie, I never said it was the fault of anything, certainly not of the cartridge. I would agree complettly that I was using ( and said so in my post ) the 30BR way beyond what the cartridge was designed to do.

In the quest to shoot it at 600 Yds ( I didn't have anything else at the time as I had a build in progress) I tried everything I could come up with. Book theory aside never once did I have a 155 grain bullet keyhole at any distance I shot it at. That would be 300 and 600 yds. Never once have I ever shot it at 100 yds. Now I didn't mess with the 155's for very long as they simple would not work. I really didn't expect them to but didn't want to leave anything on the table.

I finally after a long conversation with Mike Turner (the custom bullet guy) tried his 125 grain bullet. Micheal has had great success with this bullet in his 30/30 point blank rifle, and he though that maybe given the right conditions, that this bullet might shoot in my rifle.

It did shoot sometimes, it was a FB bullet and never was meant to shoot that far but I did manage to win a match with it on one of those Polly Anna days we get once in a blue moon.

I take my information and guidence were I can find it. However theory and written theory for me is just that theory. I shoot a lot to verify everything, proof for me is on the Target no matter what is written or by whom. If it will or won't shoot I'm not going to find out in some book.

Roland

 

[Laurie]

Roland,

like you I'll try anything, but I do try and figure the underlying physics out too wherever I can both beforehand and afterwards. When it comes to bullet and rifling twist rates, I've generally found that there is a good correlation between what the Miller formula predicts and what happens on the range.

My point was that it's not the cartridge being unsuitable, but the barrel rifling twist rate for the bullet being used, or perhaps better stated as the choice of bullet for that barrel as changing bullets is a lot easier than changing barrels. A 308 Win rifle with a 1-17" twist barrel won't stabilise 155s, but nobody says that cartridge is 'unsuitable' for 600 yards. Likewise, I've shot 7.62X39mm M43 at out to 600 yards using the 123gn Lapua flat-base FMJ 0.310" diameter bullet in a short-barrel bolt-action carbine. This is a smaller capacity case (13% smaller internally) and significantly lower performance cartridge than that the BR and while not exactly a first choice as a mid range match cartridge did surprisingly well at 500 yards, performance dropping off at 600 on a freezing cold winter's day probably because terminal velocities were now mixed sub and super sonic out there in these conditions. The rifling twist was of course suited to the bullet and its velocities.

I quite accept that 30BR is used with such slow twist barrels and specialised bullets for specialised short-range competition. I didn't suggest you try 155s in this field, rather it would have been wise to see if they worked at this distance before trying them in a mid range match. At the shorter distance you'd almost certainly be on the paper - somewhere - but you'd almost certainly see signs of gross instability. I did the same thing with the 0.224" 90gn Sierra MK in .223 Rem with a 1-8" twist barrel just to see if they worked despite what people said. This twist rate to bullet length match is much closer than what you were working with with an Sg of around 1.2 and to be honest I thought this would work out as I've used other bullet / twist / calibre combinations that stabilised OK at that sort of value. No go, oval holes and two to three inch groups even at 100.

I suspect there are bullets that would work at 600, albeit with a lot more wind drift than most combinations designed to be used competitively at this range. Some of the short 125gn 30 calibre HP varmint numbers might stabilise OK in a 1-17" twist. Lapua also makes a 0.308" version of its dinky little 123gn FMJ. As I don't use these bullets, I don't have any to hand to measure them and run them through the spreadsheet.

 

[Hombre0321]

Laurie,
I hear what you are saying, however thier is always more ways than one to skin a cat. As to testing I personally always test at the longest distance I can find. I am not interested in short range shooting and feel ( once again personally) that shooting at a longer distance is preferred if I am goimng to shot matches at greater distances.

In shooting the 155's in my 17 twist 30 br, I did get groups at the test distance of 300 yds. They wern't very good groups but they were groups. I did not have such a stablizing problem shooting them at distance that I wasn't on paper.

I am sure that you are correct that they were so unsuitable for that distance in that twist barrel that they were just not going to work.

As to the cartridge vs the twist rate. Of course I agree with you that the problem was in fact the twist rate of "MY" 30 BR. Even with a faster twist rate and the current selection of .308 bullets, and the powder capacity of the 30BR all taken into account. If someone really wanted to make this work at the Mid-Range distance I think this could be done.

I am certainly not that guy as I am complettly happy shooting cartridges that work much better. My Mid-Range benchrest and F-Class rifle is in 6BR, and with a barrel change is also chambered in 6dasher and 6X47Lapua. The switch barrel thing lets me play with weight between the two discipline's as well.

Roland