7mm Questions and Idea's

[bobeager]

OK, you 7mm fans what is the ideal twist for a 284 Win with the Berger 180 grn VLD or Hybrid? Is the "Shehane" variant worth the trouble? Where can you get the "Shehane" Dies. Is it worth going for the " 5 R" rifling? Any other "good oil" on this chambering would be appreciated.

[bruce moulds]

bob,
i would recommend the straight 284, or the 7 remsaum, bypassing the shehane.
the other option for more than the 284win is the 280 rem ackley imp. it is about the same as the remsaum but uses a 308 boltface, and rws & norma make 280 brass of equal or better quality than lapua brass. nosler also makes 280 ackley brass which does not need fireforming. 180 berger at about 3000 without stretching brass, as the shehane appears to at that level of performance.
the std 284 win will give 2800 to 2850 with good brass life. m l mcpherson of cartridges of the world fame, experimented with 284 cases improved in a manner similar to the shehane, and found that with pressure tested loads at the same pressure those cases would give about 50fps more than the std 284. of course you can always get more speed from any case, but at increased pressure.
7mm wsm faster than remsaum/280 ackley faster than 284. wind deflection and barrel life inverse. recoil as with speed.
i have shot 9" & 8.5" twist barrels in 284 win, and cannot tell the difference in accuracy.
the stability calculator on the safclass website suggests that 9" gives a stability factor well over the 1.4 normally considered safe. from memory 8.5" gives a factor of something like 1.7, which is very high. interestingly, speeding the bullet up in the same twist does not significantly increase stability compared to increasing the twist a little. worth investigating is the stability factor of a 9.5" twist, just under 1.4. enough to matter? who knows without trying it.
just my 2 cents worth from experience so far.
bruce moulds.
life is a compromise, but life is good.
edited to add: just got 2400 shots from a 284 win krieger including a rechambering. it was toast.
7mmwsm barrels reported to be as bad as or worse than 6.5/284. as low as 800 shots.
bruce moulds

[Ovenpaa]

I like the 7mm SAUM, I shoot a wildcat version with slightly squared off shoulders and Berger 180 targets however I have 500 hybrids due over very shortly to try. VLD's need some work to get the optimum OAL whereas the Targets and hopefully the Hybrids are less picky which is good when barrel life is fairly short. 180's seem to work well from 2950-3050 and the SAUM can comfortably do this.

For brass I use Norma 300 and I have recently heard of a dedicated Norma 7mm however it is easy enough to form from 300 and the brass is very consistent.

I shoot with a Barnard action and TrueFlite barrel at 32"

The Shehane is quite popular over here in the UK and seems to give good results.

[RAVEN]

Bob I'm with Bruce
Have a look at the 168VLD's as well I have had very good results with these out of 1:8.5
I have just received 2 new 32"Kiegers both 1:8.5 but one is a 5R so my load testing will be interesting to see which one works the best.

My original barrel Krieger 30" 1:85 3rd Chambering 3800 rounds down the tube was good enough to get 5th at Canberra 2010
Go the 284's
Cheers
RB

[bruce moulds]

this is purely conjecture, based on anecdotal evidence.
it appears that the 180 berger has an accuracy node at about 2800 to 2850, then another one between 2950 and 3000.
the standard 284 win can achieve the first one comfortably, and the 280 ack/saum can do the latter easily. they do it at accurate pressures, and case life pressures.
evidence for the above statement is all out of 9 twist barrels. 8.5 remains to be seen.
are these nodes due to velocity, pressure, bullet spin rate, or a combination of all or some of these, or something else.
so far my 8.5 twist seems to shoot at the 2800 node, as did a previous 9 twist. this at pressures which gives more than 20 shots on primer pockets.
the poor old shehane is somewhere in between, not giving enough pressure for the 2800 node, and too much for the higher one. it appears the tack drive at the high node, but primer pockets suffer.
if you really want to hold close to the wind, i believe some brits have experimented with the 404 jeffery improved necked down to 7mm. 180 at 3600 to 3800.
bruce.

[bobeager]

Thank you all.

[bruce moulds]

bob,
it would be most interesting to hear what you decide and why.
also remember that sierra now has a 180 gn 7mm bullet.
bruce.

[bobeager]

Most likely a straight 284 Win, in a 8.5 twist, 30" Kreiger HV profilel with 5R rifling. Why, my mate has a 284 reamer, my other mate is a barrel fitter (wizard), 284 dies are easy to come by, I am intersted in about 2800 to 2850 to 2900 fps because I don't like recoil, and a 5 R barrel because I haven't tried one before. Just don't tell my wife or my "Dasher" about it!

Thanks to all who responded.

[Cameron Mc]

Most likely a straight 284 Win, in a 8.5 twist, 30" Kreiger HV profilel with 5R rifling. Why, my mate has a 284 reamer, my other mate is a barrel fitter (wizard), 284 dies are easy to come by, I am intersted in about 2800 to 2850 to 2900 fps because I don't like recoil, and a 5 R barrel because I haven't tried one before. Just don't tell my wife or my "Dasher" about it!

Thanks to all who responded.

Bob, I have been shooting straight 284 for some time now. Have settled with 1-9.5" twist. Have had no problems stablising 175mk's. Have tried 180 Berger's also out to 600yds with no sign of stablisation issues.

I think you will find the recoil quite easy to handle with 284 and 2850fps. It is a big push, not snappy like a 308w.

If you need any info let me know.

Cameron

[RAVEN]

Cameron I found the same felt recoil in my 7mm Mag with 2217 slow burning the recoil is like a push not punch the higher energy faster burning powder will give more felt recoil than the slower 2213 & 2217
The 1:9.5 IMO doesn’t work at sea level
an Open shooter has one hear in SA with luck warm results using 180VLD's
I have a 1:9 Kreiger and my velocity is 200fps slower than my original 1:8.5 doggy barrel I guess
As more ppl get this calibre we can make more informed choices with lots of data about.
I can tell you now that there are things that work in Queensland but not elsewhere.
I built my first 284 in 03

[bruce moulds]

there's a fair bit of stuff about 7mm on the 6br forum at the moment.
bruce.

[BATattack]

this is purely conjecture, based on anecdotal evidence.
it appears that the 180 berger has an accuracy node at about 2800 to 2850, then another one between 2950 and 3000.
the standard 284 win can achieve the first one comfortably, and the 280 ack/saum can do the latter easily. they do it at accurate pressures, and case life pressures.
evidence for the above statement is all out of 9 twist barrels. 8.5 remains to be seen.
are these nodes due to velocity, pressure, bullet spin rate, or a combination of all or some of these, or something else.
so far my 8.5 twist seems to shoot at the 2800 node, as did a previous 9 twist. this at pressures which gives more than 20 shots on primer pockets.
the poor old shehane is somewhere in between, not giving enough pressure for the 2800 node, and too much for the higher one. it appears the tack drive at the high node, but primer pockets suffer.
if you really want to hold close to the wind, i believe some brits have experimented with the 404 jeffery improved necked down to 7mm. 180 at 3600 to 3800.
bruce.

the bergers have another node at 3100fps that really hammers!!

[Cameron Mc]

Cameron I found the same felt recoil in my 7mm Mag with 2217 slow burning the recoil is like a push not punch the higher energy faster burning powder will give more felt recoil than the slower 2213 & 2217
The 1:9.5 IMO doesn’t work at sea level
an Open shooter has one hear in SA with luck warm results using 180VLD's
I have a 1:9 Kreiger and my velocity is 200fps slower than my original 1:8.5 doggy barrel I guess
As more ppl get this calibre we can make more informed choices with lots of data about.
I can tell you now that there are things that work in Queensland but not elsewhere.
I built my first 284 in 03

1-9.5" twist is too close to the edge for the 180vld's. I have had my best scores at Belmont (sea level I think) with 175mk's and 168smk's. I am going to try the new 180smk for interest. Are these available yet? How many rounds can you go before accuracy goes off? My original barrel has done 1900rds and is still performing with little fouling....Kreiger.

Cameron

[RAVEN]

1600- 1800

[bruce moulds]

cameron,
i'm not altogether convinced that 9.5 twist is too slow for the 180 berger. it should be stable if the formula is correct. the guy down here with problems could have them elsewhere.
the 155 gn 308 bullet only has a stability factor of 1.33 on the safclass calculator. i am assuming it is one of the current fullbore bullets. the 180 berger out of a 9.5 twist has a factor approaching 1.4 at 2800 fps.
it would be a good experiment, but it would cost money to find out for sure.
the new sierra 180 is shorter than the 180 berger, possibly nearer to the length of the 175 sierra, or about 1/2 way in between according to photos. it also has a claimed b.c. equal to the berger. might be just the ants pants for you.
i would strongly consider rechambering that barrel now to get the best value out of it. the other option is to just run it 'till you kill it.
bruce.