twists and nodes

[bruce moulds]

there seems to be a node for 180 bergers in 7mm at about 2820 - 2840.
this seems to be a fairly common in this country and overseas.
mostly these loads have been shot in 9 twist barrels. my experience with a 9 twist barrel agrees with this with 3 different powders.
experience with two 8.5 twist barrels presents no node at these speeds, but a good one at just below 2800.
this suggests that spin rate is connected to accuracy.
as an aside, i feel that the ideal burn rate powder to achieve these speeds in a std 284 would be a 50/50 blend of 2209/2213sc, but i am too scared to try it.
bruce.

[Lynn Otto]

I'm no expert on reloading but rule no 1 says "Do NOT mix powders". I think it is a good thing that you are too scared to do this Bruce, for all of your foibles I would rather you stayed with us a bit longer.

[Norm]

Maybe just getting a longer barrel would be safer?

[johnk]

There are manufacturers other than Thales.

What about Reloader 19, or VV 160 or 560?

[Hangfire]

Go 280 Ackley.

[RDavies]

Ive had 8, 9 and 10" twist 284 barrels and the only difference in nodes has been minor and due to barrel length. My 31" barrels have been in tune at 2830-2840. The 29" barrels at 2820, and the 28" barrels at 2800. My 6BR and 6.5 seem to reflect this as well.
For me 2209 seems to be perfect for the lower node with 180s. A bit of pressure, but its where it likes to burn consistantly.

[bruce moulds]

just when you come up with a good theory, someone kills it with facts.
oh well,
bruce.

[Hangfire]

Still go 280Ackley. You might find a better node at 3000!

[DaveMc]

I have had less 7mm barrels than you guys but 2820-2840 concurs with a lot of my barrels (including both 7mm - 9 twists but also 6.5 and 6mm 8 and 8.5 twists). When they get short I tend to go for a faster powder, smaller case and lighter pill (e.g. 2208 123gr instead of 2209 and 139 in 6.5) so can't confirm this node with length but it makes sense and have seen similar with the 2950-2980 node in my BR - comes back to 2920 in the short barrel.

If I can't find a node around there (and I will search from 2800-2850) I change my seating depth and try again - normally comes together quickly otherwise I label the barrel as "finicky" and move on.

Love the thought of the 280 Ackley and now I seem to have a couple of good 284SH barrels will look seriously at it (wait till you see my latest one Rod -am desperately trying to work out how to get it and myself down to NSW Queens) . I don't see many 280AI's around up here though. Are there many down south?? The SAfricans seem to like them and I would probably design reamer around necked down Lap 30-06 brass for a try. I am down to this, a no neck 284 Shehane, or a 7mm RSAUM for my "wild wind day" rifle. But the 280AI is coming up favourite at the moment (well this week at least!) due to my supply of 308 bolt head actions including and a brand new BAT Tri lug staring at me. PLUS 3 more 7mm barrels (2 @ 32 inch) plus the fact the South Africans are as much in love with their "tombi" as we are with the 284. Any comments - reports - news appreciated......

[Matt P]

Dave
The biggest issue with the 280AI, is the brass. The lapua isn't real flash and the other option RWS is very $$$$. I was using a 7/06 improved and the velocity wasn't much better than the 284, if your're going to buy a reamer anyway look at necking down the 9.3 x 62 Lapua case to 7 mm slightly more case capacity than the 280ai with high quality brass.
Matt P

[bruce moulds]

dave,
be aware that the 280 case holds more powder than the 7mm/06 due to the shoulder being 0.050 forward.
full to the top of the neck, i believe that the 280ai is closer in capacity to the saum than the 284 win.
rws brass is $$$$$$, but it is if anything better than lapua.
there is also nosler 280ai off the shelf.
it would seem that the 280ai will work with ar2217, offering improved barrel life.
my experiments show real world capacities to be virtually the same for the 7mm/06 unimproved and the 284 win to the base of the neck.
there are a few around here in s.a., and all shoot well with minimal work.
one thig the 280ai has is a lovely long neck, meaning you don't require much freebore (less than 0.2") and there is a bit more protection offered to the throat.
bruce.

[bruce moulds]

buffalo arms sells 284 basic brass. this seems longer than formed 284 win brass measured around the outside.
possibly it could be formed into a 284 shehane with the same length neck and a longer body.
9.3x64 brenneke brass has similar body diameter to the 284, which is 0.5" in front of the extractor groove, the same as a h&h case in front of the belt.
a machinist could convert rim diameter to 308 size, and a set of form dies could produce cases of whatever capacity required, which would not need fireforming if all the tooling was correct.
the 9.3 x62 case that matt mentioned has been necked down and legitimized as the 6.5 x 65 by rws. it would be a snap to neck this up to 7mm and fireform in an improved chamber. another alternative would be to deal with the shoulder angle how it is done with the 6 and 6.5 super lr by pushing the neck/shoulder junction back to create a 30 degree shoulder.
just some thoughts,
bruce.

[MROFD]

Bruce, the 280AI sounds like a good thing...........

[DaveMc]

Matt,
That's dissapointing news on the Lapua brass.

Thanks on the info too Bruce. _ I can convert the bolt head here but would prefer to leave all as 308 for now so I can switch barrels back to 284 if I want (and per my mood on the day.....?) . Might do it with one of the savages but not the BAT.

I agree the 280AI does sound like a good thing - in fact they all sound good so which way to go???
Anyone know what brass the South Africans use????

Come in Jannie??????

[Cameron Mc]

Dave , I tried 280ai. RWS brass, really good but expensive. I found the 284 to be more efficient in comparison. I had to load back my 280ai to get accuracy. With Bergers it may be different.

Just my thoughts
Cameron

PS the 6 SwissMiss is going great, but again, expensive RWS brass.