Starting in 7MM - Straight 284 or Shehane

[pat fulghum]

I started shooting F class last March, I jumped in with both feet and learned a lot but I wish I knew more before I geared up.

For example, I bought a 6BR off this site (Thanks Cody Richardson) and made it to Mid-Range High Master quickly, but I really wish I would have started with a Dasher vs that 6BR.

I did shoot 4 days at Rattlesnake ridge and did well with the 6BR, but I was the only one shooting a 6BR and really was out gunned.

So I'm trying to not make the same mistake again with my Long Range build. I have everything in hand except I'm still torn over the reamer decision.

For those of you that have a straight 284 .. Do you ever wish you had a 284 Shehane?

Is one easier to tune a load compared to the other?

All advise appreciated.

-- pat

 

[ShootDots]

I started shooting F class last March, I jumped in with both feet and learned a lot but I wish I knew more before I geared up.

For example, I bought a 6BR off this site (Thanks Cody Richardson) and made it to Mid-Range High Master quickly, but I really wish I would have started with a Dasher vs that 6BR.

I did shoot 4 days at Rattlesnake ridge and did well with the 6BR, but I was the only one shooting a 6BR and really was out gunned.

So I'm trying to not make the same mistake again with my Long Range build. I have everything in hand except I'm still torn over the reamer decision.

For those of you that have a straight 284 .. Do you ever wish you had a 284 Shehane?

Is one easier to tune a load compared to the other?

All advise appreciated.

-- pat

I had 3 Shehanes and 2 "straight" .284's. I have read that there is approximately 3.3grs more water weight capacity in a Shehane over the .284. However, in reality, as far as "practical" powder loading goes, you will realize "generally" only about 1 (and maybe a few tenths) gr more powder. There is no "performance sense" in doing a Shehane over the straight .284. All you are doing with a Shehane is straightening out the case walls to a very minor degree. To give you an idea of just how small the transition is from a .284 to a Shehane is, when I dumped my last Shehane, I tried an experiment. I re-sized the Shehane brass back into a straight .284 die with ZERO ill effects. As a matter of fact, I could not tell any more resistance running the Shehane cases back thru the .284 die than I did when I ran straight .284 brass in! There is NO benefit>>>period!

 

[Zilla]

Straight .284.

 

[Elwood]

In my .284 I use 55 to 55.6 grains of H4831sc and in my Shehane I run between 57.4 to 58 grains, there's approximately 100 fps difference between the two, 2820/2830 fps versus 2930/2950 fps. In my book that 100 fps at top level will make a difference.
I would argue that the .284 is possibly easier to tune, and probably more powders to choose from, but all of my Shehanes have shot extremely well with either H4831sc or on ShootDots recommendation IMR 7828ssc.

My vote goes to the Shehane, every bit as accurate and that extra 100 fps is the difference between cutting the line and getting the point.

 

[ngb1787]

Keep it easy, .284

 

[birdog]

With my Straight 284 and RL-17 I get 2925 fps with single digit SD. I have shot it at 20 degrees and at 98 degrees and have not had to adjust my load. It performs well to 1800 yards.



1500 yards
one sighter then four on paper

 

[DJSBRS]

With my Straight 284 and RL-17 I get 2925 fps with single digit SD. I have shot it at 20 degrees and at 98 degrees and have not had to adjust my load. It performs well to 1800 yards.



1500 yards
one sighter then four on paper

Randy, what twist barrel and length, and primer did you use for your test?

DJ
DJ's Brass Service
205-461-4680

 

[Laurie]

Like Benjamin (Shootdots), I have both and found that the make of barrel appears to have a greater effect on MVs than the chamber / case. My Benchmark barrelled Shehane actually shoots slower than my Bartlein barreled straight 284 - not by much and I run full cases in both with Viht N165. I'm not running them as fast as Ian (Elwood) and have obtained good results from both.

Logically, I should say there's no benefit in going for the Shehane, but for some reason (unlike Elwood's experience) I found it easier to tune and on balance, now that I have the dies, I'd likely rebarrel both rifles in Shehane than the straight version when required.

However, there is nothing like the performance difference between them as there is between the plain 6BR and the Dasher, so if velocity alone is the criterion I'd say stick with the straight version.

 

[Keith Glasscock]

Pat,

You can make 2900+ velocities with a straight 284. I will be testing a new combination out at Rattlesnake this year. It easily obtains 2925 (with excellent accuracy to 500 yards) through my Benchmark barrel. I can push it another 100 fps higher, but I'm just starting to sense that the pressure seems to be sneaking up on me at that point.

One of the reasons I shoot the slower load (2820 ish) is that I don't have to do load development per se. I can throw the same charge of H4350 in a straight case and shoot it through virtually any barrel with good results. Right now, I have 3 barrels that I shoot the same charge through. Two of them are 32" long and the last is 30". I love tolerant systems.

Recoil is a big consideration with 7mm's. The faster you go, the more it wears you out with recoil and torque.

 

[birdog]

Randy, what twist barrel and length, and primer did you use for your test?

DJ
DJ's Brass Service
205-461-4680

9 twist Brux
CCI BR
30"

 

[Ringostar]

Which bullet do you plan on using? Many shooters have learned that a little less velocity is more accurate. Those shooting the 180 hybrid tend to prefer the lower 2800 range. One of the best shooters already commented on using the straight 284. He says that he's only at 2790, and recently broke his own national record score. Many shehane shooters have gone back to straight 284, because of preferred lower velocity.

 

[Sniper338]

Another vote for straight 284. Not enough to benefit doing a shehane.

 

[Scott Harris]

we have shot out many Shehane barrels over the years and recently are shooting straight 284s. we load to get 12-15 reloads from our brass. this equates to an average speed of 2870 with the Shehane and 2770 with the 284. So, when loaded to the same pressure, I estimate you get about 100 fps extra with the Shehane.

Additional data points. we start seeing pressure signs around 2850 with the 284 and 2950 fps with the shehane. my freebore is .250 with the 180 hybrids

 

[Keith Glasscock]

Scott, which bullet, brass and powder?

 

[pat fulghum]

THANKS!

I have read through all the advice here and what I have read other places.

I do plan to shoot the 180 Hybrids..

I'm going to bite the bullet and go with straight 284, 32" Straight Bartlien, 1 in 9 twist, .188 freebore, .015 Jump.

Please let me know if I'm doing something wrong with that selection...



Final Expected Ballistics
So at 1,000 yards with 10 MPH cross wind at 1000 ft elevation at 65 degrees... (Rattlesnake Washington approximation)

180Hybrid @2830 fps, 271 inches drop with 55.0 inches wind (Proposed 284 - H4350)
180Hybrid @2930 fps, 250 inches drop with 52.0 inches wind (Proposed Shehane or Straight with RL17)

vs.

105 Hybrid @3175, 234 inches drop with 62.6 inches wind - (My 6x47L)
105 Hybrid @3000, 269 inched drop with 68.7 inches wind - (someone's dasher)
105 Hybrid @2850, 304 inches drop with 74.8 inches wind - (My 6mmBR)

-- pat

 

[Ringostar]

Will a 188 freebore keep you above the doughnut? You might consider a little more clearance.

 

[dskogman]

The .188 Free bore works fine with 180 hybrids. Your proposed setup is almost exactly what I have except I have an 8.5 Twist. Shoots great.

 

[pat fulghum]

Now the question turns (pun intended) to neck size and brass.

Here is what I've read....

Norma (aka Shiraz) brass is thick at .0155
Would require .284+.031+.004 or a .319 neck if you don't want to turn or deal with donuts. But I still see that most people turn it down to ~.0125 thickness then use .313 neck chamber. Is .0155 neck wall too thick for accuracy?


Lapua
Take 6.5x284 Lapua brass, which is also thick but you have to expand it to 7mm. Neck wall will thin to ~.014 during expansion and neck turning needed for donut removal. Seems like most turn brass down to .0125 and use a .313 neck

Seems like each requires turning, so it seems like .313 neck is the way to go.

Did I get this right?

 

[Cowtownup]

Your math and logic appear correct to me. I've seen people post reamer specs from .313 to .319 neck diameter and freebore is typically in that .220 range for shooting 180's and 183 SMKs...

I went with a .316 neck and a .225 freebore and plan on shooting the 183 SMKs. I necked up Lapua brass with a sinclair expander mandrel and turned the necks to .014" thick. That should put me at .284" + .014 + .014 = .312" loaded round and leave me .004" clearance. However, the 183 SMK's measure .283 diamter which gave me another .001 of clearance. I'm going to be shooting straight 284 in a Bartlein 8.7 twist.

Good luck to you...

 

[Keith Glasscock]

Now the question turns (pun intended) to neck size and brass.

Here is what I've read....

Norma (aka Shiraz) brass is thick at .0155
Would require .284+.031+.004 or a .319 neck if you don't want to turn or deal with donuts. But I still see that most people turn it down to ~.0125 thickness then use .313 neck chamber. Is .0155 neck wall too thick for accuracy?


Lapua
Take 6.5x284 Lapua brass, which is also thick but you have to expand it to 7mm. Neck wall will thin to ~.014 during expansion and neck turning needed for donut removal. Seems like most turn brass down to .0125 and use a .313 neck

Seems like each requires turning, so it seems like .313 neck is the way to go.

Did I get this right?

On the Lapua brass, use a .315 neck and .220ish freebore to stay above the donut. Neck turning doesn't eliminate the donut...