284win build specs

[longrangeprecisionshooter]

Plan to get a 7mm barrel to try the 284win caliber for some casual local match from 800-1000yard.
Not sure about the twist rate and powder selection for the build.

What I have in mind is, 28-30inch barrel in 1.25" straight or heavy contour like M24/MTU, all depends on availability of the barrel blank. Would like to shoot heavy bullets between 175gr and 190gr. Is 2700-2800 an ideal Muzzle Velocity for heavy bullet?

I searched online, majority shoot in 8.5 or 9 twist, some shoots 8 twist. Not sure if 9 twist is still OK, or harder to tune the load/push the 184gr or 190gr bullets in 28" barrel to faster MV?

Any suggestion on the reamer's freebore length? The longer the better(more flexible) or really depends on the specific brand/type of bullet I am using?

And for powder, not sure what the best fit for 284win is, what I have in Varget and H4350 with small amount of N555 can be used for break in and load testing.

Any information or suggestions would be appreciated. Thank you.

 

[FeMan]

For barrels twist, I have used 8.5s and 9s. Both have worked for Berger 180 and 184 just fine at sea level. If you want to shoot 190+ or ELDMs, you might want to go to an 8.5 as they are harder to stabilize. I don't see any benefit to going to an 8. I'll bet they shoot just as well but it will produce more torque on recoil.

I would recommend Berger 180s or 184s. The 190s seem to do well in RSAUMs and other cartridges that can push them at higher speeds. I could never get them to shoot well in my 284s.

As far as freebore goes, I have 3 reamers but the 0.235 and 0.205 work well with the Bergers. I have shot many more barrels with the 0.235 and never ran out of neck even up to 3,000 rounds of throat wear.

I would start with H4350 since you have it. I have shot it, 4831sc, RL16, RL23, and VN160. All these have worked well in particular barrels but H4530 is the one the barrels usually prefer IME.

Good luck and I hope that helps.

 

[bulaman]

I shoot a 30", 1.25 straight Krieger in 284 Win (Not Shehane). My reamer is a 0.225" FB with a 0.319" No Turn Neck with Lapua brass. I shoot mostly 184 Bergers seated at the lands and flip back and forth between RL-16 and N555. I know a lot of guys that shoot the 180-184 grain bergers with H4831SC and like it as well. The sweet spot for my barrels have been 2,800-2820 fps.

 

[rimfiremac]

9 twist is too slow for the >180gr offerings. The geometry of the 183smk etc and 195eol are similar and need to be spun at 8.5 at a minimum.

Epicyclic radius gets smaller with faster twist also, so, spin fast and chill.

Rhetorical point these days, but drive using RL23 or RL26 and the straight 284 will impress you. Accuracy node for just about everything is someplace between 2770 and 2820, so drive up to that and then fine tune in that band.

If this is only for match shooting inside 1k though, the same on-paper results can be achieved with the fast 6's. All diameter does is increase energy on arrival (and departure). Run the numbers for drift with 2 mph wind at 1k between a fast 6 and heavy 7 and the delta between those numbers is your performance gain... The gross drift is still your miss.

 

[Sandstorm]

9 twist is just fine for F-Class and the 180 or 184 gr Bergers and preferred by most that i shoot with.

 

[yukonal]

9 twist is too slow for the >180gr offerings. The geometry of the 183smk etc and 195eol are similar and need to be spun at 8.5 at a minimum.

I've been shooting 180's out of a 9 twist for a decade. They shoot better than the 168's did...and they hammered.

 

[rimfiremac]

Yep, totally, the 180s run fine in the 9, and like you say always have... The new stuff is a bit different in geometry (ie cg/cp geometry) and hence benefit from the fast spin.

The 180gr hyb- smk- etc world and the 9 roto is well proven, no misunderstanding there

 

[longrangeprecisionshooter]

Thank you very much for everyone's reply.

I noticed the 175gr, 180gr and 183gr Sierra's 7mm bullets from their matchking line requires 8.5 to 8 or even faster twist, is this true? It seems Berger's 184gr still can stabilize in 9twist, or that twist value showing on Sierra's website is because it is in a slower muzzle velocity?

 

[Willow]

I run 8.5 twist barrels for my 284 Shehane, 32" barrels and 2213sc (H4831sc) powder. No issues with stabilising Berger 184gr with an 8.5 twist barrel. If you intend to try Sierra 183s, you will need an 8 twist.

 

[1shot]

Sierra 183's shot OK at best out of a 9 twist, at 1,200 ft. ASL. However, they shot lights out in Colorado at 5,600 ft. ASL. I'm now shooting a 8.5 and both Sierra and Berger bullets perform as expected. I have an 8 twist that I'm just starting to break in, but haven't had the opportunity to take it to 1K yet.
I hope this helps,

Lloyd

 

[longrangeprecisionshooter]

I run 8.5 twist barrels for my 284 Shehane, 32" barrels and 2213sc (H4831sc) powder. No issues with stabilising Berger 184gr with an 8.5 twist barrel. If you intend to try Sierra 183s, you will need an 8 twist.

Thank you for the information.

It surprises me that Sierra's heavy 7mm bullets requires much faster twist when it is in the same bullet weight range with berger's, which only requires 9 twists even at 190gr. Hornady also requires 8twist for their 180gr ELD-M.

Any idea why? As Berger hybrid target bullets is hard to get these days, I am considering to have some alternative options, but don't want to get the wrong barrel twist which can not stabilize the bullet.

 

[FeMan]

I have shot the 183 Sierras out of a 9 twist at sea level and had no issues with stability. The only ones a 9 twist would not handle for me were the ELDMs and the 190+.

 

[Liven The Dream]

On my first .284 I asked the the same Question !
From Krieger Barrels 1-8.5 30"
From My Smith ( Barrel Only Man) 1-8.5
I have and do shot 180 HB, 183 Sierra , 180ELD's I think it is working ?
I have shot a Sea Level and 4000 ft. and more .

I think keeping them below 2800 is a Plus?

180 Berger HB and Sierra 183's are hard to get ? I have B/O and wish list them >

 

[Sandstorm]

The 183 Sierra has a longer bering surface than the Berger 180 thats much shorter.
Thats really all there is to it...The longer bullets bearing surface requires more twist.

 

[GregC]

9 twist is too slow for the >180gr offerings. The geometry of the 183smk etc and 195eol are similar and need to be spun at 8.5 at a minimum.

Epicyclic radius gets smaller with faster twist also, so, spin fast and chill.

Rhetorical point these days, but drive using RL23 or RL26 and the straight 284 will impress you. Accuracy node for just about everything is someplace between 2770 and 2820, so drive up to that and then fine tune in that band.

If this is only for match shooting inside 1k though, the same on-paper results can be achieved with the fast 6's. All diameter does is increase energy on arrival (and departure). Run the numbers for drift with 2 mph wind at 1k between a fast 6 and heavy 7 and the delta between those numbers is your performance gain... The gross drift is still your miss.

the 1000yd record was set with a 9 twist & 184s.... most of us shoot 8.5tw with 180s 184s these days.... 190s haven't worked out for us shooting 284s and Shehanes.

 

[Drolds72]

Here is a target using 180's out of a 9t 32" brux. 2770fps I think its gonna shoot....

 

[longrangeprecisionshooter]

I have shot the 183 Sierras out of a 9 twist at sea level and had no issues with stability. The only ones a 9 twist would not handle for me were the ELDMs and the 190+.

Thank you.

Would you think the 180gr ELDM would work in 8.5twist? Just saw a local shop has 29" blank 7mm in 8.5twist in stock. Thinking to give it a try to start my 7mm shooting, for the next barrel in order, will definitely to get a 30" or longer barrel.

 

[Sandstorm]

The Begers are the preferred bullets.
If the ELDM,s dont work out.
Get some 180 or 184 Hybrids and youl be better off in the long run
But you decide on how you want to get there, in any case the 8.5 twist will work for most of the good bullets at least.

 

[longrangeprecisionshooter]

The Begers are the preferred bullets.
If the ELDM,s dont work out.
Get some 180 or 184 Hybrids and youl be better off in the long run
But you decide on how you want to get there, in any case the 8.5 twist will work for most of the good bullets at least.

Definitely Berger is the best/most consistent bullet to use. Maybe a-tip the 2nd if doesn't consider the cost.
Availability wise, Hornady 180gr ELDM, 190gr a-tip and Sierra 18xgr bullets are easier to find. Berger, only the 190gr Long Range Hybrid is in stock.
But I guess, for the 1st barrel, getting the experience and do some more testing are more important.

Thanks a lot for everyone's input.

 

[FeMan]

Thank you.

Would you think the 180gr ELDM would work in 8.5twist? Just saw a local shop has 29" blank 7mm in 8.5twist in stock. Thinking to give it a try to start my 7mm shooting, for the next barrel in order, will definitely to get a 30" or longer barrel.

I shot the ELDMs in an 8.5 twist. They would not stabilize in a 1:9 at sea level. They were extremely accurate and I shot around 1,200 of them. Then with the round count growing and warmer weather, they started blowing up on me in matches. I dropped them like a hot skillet and went back to Bergers.