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.284 Jarrett

Sotahirvi

Private
Full Member
Minuteman
Aug 13, 2010
21
1
44
Northern Sweden
Fellas!

Looking for some had facts and experiense from this cartridge.
A friend of mine is planning a build and after some conferencing and discussing i suggested the .284 Jarrett.

From the Jarrett homepage:

".284 Jarrett
140 gr. Nosler bullet....3450 to 3500 f.p.s. | 150 gr. Nosler bullet....3350 to 3375 f.p.s.
160 gr. Nosler bullet....3250 to 3300 f.p.s. |
We were amazed that the .300 Winchester Magnum had never been reduced to 7 mm successfully. The wheels really began to turn wondering exactly what the volume of the case would be. We designed a different case taper, then used our traditional 35 degree shoulder along with a lead angle in the throat to accommodate 140 and 160 gr. bullets. We had a reamer made and proceeded to build the .284 Jarrett! After the case fire forming was completed, we did comparisons with the other big sevens to see where ours fit. We checked all of the cases by water volume and this is what we came up with: (volume to base of neck)

7mm Remington Magnum ..........73.5 gr. | 7mm Weatherby Magnum ..........78.0 gr.
..284 Jarrett ................................85.5 gr. | 7mm STW ................................98.3 gr.

It’s interesting to note where we are volume wise: 12 gr. greater than the Remington Magnum and 13 gr. less than the 7mm STW.

The next step was to shoot this thing! Of foremost importance to us was its accuracy. If it’s not accurate, the velocity doesn’t matter. The cartridge responded well to a variety of powders and without effort we were under our half minute accuracy with velocities appropriate for this case capacity. Our testing produced the following results:

140 gr. Nosler bullet.................................... 3450 to 3500 f.p.s.
..150 gr. Nosler bullet.................................... 3350 to 3375 f.p.s.
..160 gr. Nosler bullet.................................... 3250 to 3300 f.p.s.

These velocities are identical to a 7mm STW with a lot less powder. Even though all the 7mm cartridges are listed overbore, the question is how much overbore can you stand and still have a dependable cartridge? I do know the velocities shown are the absolute maximums for 7mm bullets, regardless of how much powder you use. The Mexican standoff: the bigger case won’t give you any more, and a smaller case won’t give you as much. This is the reason, for all the 7mm fans, we have to max out the 7mm bullet. It rounds out our performance cartridge line and gives us a big 7 that meets our accuracy criteria while producing predictable velocities. In an emergency, a Weatherby cartridge can be used in the .284 Jarrett, but I don’t recommend reloading them because the neck will be too short. Put a .284 Jarrett in your battery soon!"

According to EXBAL you get supersonic velocity out to 1800 m with 140 grs bergers vld´s at sea level.

Also it should fit the long action AI mags perfect.

Right! Anyone know?

Accuracy of the round?
Handloading easy/hard?
Case life expectancy?
Barrel life expectancy?
Twist rate?
Bullets recommended?
 
Re: .284 Jarrett

why not look at the 7mm Dakota it is based of a shortened 404 case that also works perfectly through AI mags.

Have a look at 190gr Matrix bullets from canada aswell i have measured them over .780bc.

The accuracy would be fine with the Jarret and the barrel life with heavy bullets and Retumbo will give you well over 3100fps in a 26-28" barrel and case life is over 10 rounds reloading and also dies and cases are available from Dakota. you can not achieve some of the stated balistics within safe pressure limits every one seems to say that their cartrige is so superiour.

Get the 7mm Dakota and dont look back it is pretty close tot he 7mm STW in calacity but works perfectly through AI mags and a long action. the rim is .012" larger than the standard magnums but most boltfaces work without modification if there is a problem just open it slightly.

Like i said cases dies and reamers are available for the 7mm Dakota it also has a 30 degree shoulder like most high accuracy benchrest cartriges. if you want the ultimate 7mm this is it because of its ease of loading through mags and working at safe pressures with exceptional accuracy. we are currently building 2 of them and the 9 twist will work with any projectile including the 190gr Matrix.

If you want any details just PM me.

 
Re: .284 Jarrett

+1 on the 7mm Dakota. I've spent nearly a year looking at stepping up from the 7WSM, but only wanted to go up to with roughly 90 grains of h20 from the 83 of the WSM. I wanted to run the 190 Cauterucio and 190 Matrix 7mm pills to 3,200 fps from a roughly 28" barrel. Finally, I needed to be able to load from a 300WM AI Magazine, which means an COAL of 3.645" or shorter.

I looked at the 7 RUM with the shoulder pushed back, reforming the 7 STW, and the 7/300NormaMagnum, with shoulder pushed back (but didn't want to have to jump up to the 338 Action), I didn't really consider the 7/300WM, as I will not play with the belted cases. The Dakota give me everything I was looking for, although its kind of a pain to get good dies for, as I have now found out. But Neal Jones custom dies are going to cure that problem for me.

Jeffvn
 
Re: .284 Jarrett

Why not the 7 STW
Brass is easy, necked down 8mm Rem Mag, dies are easy to find as well.
I don't think the STW gives up anything to the Jarrett.
168gr Berger with Retumbo at 3150-3200fps
 
Re: .284 Jarrett

First thanx for all the answers.

My friend wanted to use the AICS stock on the remmy 700 and the STW is to long with the shoulder for the mags. some gunsmithing would probably solve the problem but he also wanted something exotic and easy to make from other cases.
Also he vanted to have a barrel life of 4500ish rounds.

He has also looked on the 280rem AI.
 
Re: .284 Jarrett


As to why not the 7mmSTW , I think its a lot tricker to get good accuracy from , where the 7mm/300WM is easier to get running good, if that makes sense .

Later Chris
 
Re: .284 Jarrett

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sotahirvi</div><div class="ubbcode-body">Fellas!

Looking for some had facts and experiense from this cartridge.
A friend of mine is planning a build and after some conferencing and discussing i suggested the .284 Jarrett.

From the Jarrett homepage:

".284 Jarrett
140 gr. Nosler bullet....3450 to 3500 f.p.s. | 150 gr. Nosler bullet....3350 to 3375 f.p.s.
160 gr. Nosler bullet....3250 to 3300 f.p.s. |
We were amazed that the .300 Winchester Magnum had never been reduced to 7 mm successfully. The wheels really began to turn wondering exactly what the volume of the case would be. We designed a different case taper, then used our traditional 35 degree shoulder along with a lead angle in the throat to accommodate 140 and 160 gr. bullets. We had a reamer made and proceeded to build the .284 Jarrett! After the case fire forming was completed, we did comparisons with the other big sevens to see where ours fit. We checked all of the cases by water volume and this is what we came up with: (volume to base of neck)

7mm Remington Magnum ..........73.5 gr. | 7mm Weatherby Magnum ..........78.0 gr.
..284 Jarrett ................................85.5 gr. | 7mm STW ................................98.3 gr.

It’s interesting to note where we are volume wise: 12 gr. greater than the Remington Magnum and 13 gr. less than the 7mm STW.

The next step was to shoot this thing! Of foremost importance to us was its accuracy. If it’s not accurate, the velocity doesn’t matter. The cartridge responded well to a variety of powders and without effort we were under our half minute accuracy with velocities appropriate for this case capacity. Our testing produced the following results:

140 gr. Nosler bullet.................................... 3450 to 3500 f.p.s.
..150 gr. Nosler bullet.................................... 3350 to 3375 f.p.s.
..160 gr. Nosler bullet.................................... 3250 to 3300 f.p.s.

These velocities are identical to a 7mm STW with a lot less powder. Even though all the 7mm cartridges are listed overbore, the question is how much overbore can you stand and still have a dependable cartridge? I do know the velocities shown are the absolute maximums for 7mm bullets, regardless of how much powder you use. The Mexican standoff: the bigger case won’t give you any more, and a smaller case won’t give you as much. This is the reason, for all the 7mm fans, we have to max out the 7mm bullet. It rounds out our performance cartridge line and gives us a big 7 that meets our accuracy criteria while producing predictable velocities. In an emergency, a Weatherby cartridge can be used in the .284 Jarrett, but I don’t recommend reloading them because the neck will be too short. Put a .284 Jarrett in your battery soon!"

According to EXBAL you get supersonic velocity out to 1800 m with 140 grs bergers vld´s at sea level.

Also it should fit the long action AI mags perfect.

Right! Anyone know?

Accuracy of the round?
Handloading easy/hard?
Case life expectancy?
Barrel life expectancy?
Twist rate?
Bullets recommended?</div></div>

I've shot a number of big 7mm magnums and I've shot a lot of Berger 140 grs. I will tell you something is wrong in the input if you think you are going to get 1800m+ supersonic from a 140 gr. Berger. @ std. sea level pressure. JBM only shows 1400m supersonic and 1300 above the transonic range.
They are good yes, but you will not get the performance you need unless you go to the 168's or 180's. Which your rifle can easily do.

Sorry my input is on the bullets only, but that's my experience with 7mm's.
 
Re: .284 Jarrett

Ah! you are absolutly right Sandwarrior. I put in the .264 VLD from the list by mistake.
whistle.gif