284 case design issues (relevant for all 284 derivatives and wild cats)

[TonyR]

Hengehold.
I and others have gotten excellent vertical shooting the 180 grain bullets with the 280 class cases and the 7mm SAUM as well as the Shehane. I can't speak to brass life for the others but I just got rid of some Shehane cases with at least 8 to 10 firings on them after one of the necks split. Some of the cases in this group were used in testing loads with velocities up to 3000 fps, but most of the firing was done in the 2900 range.

 

[camac]

Hengehold,
I think the point to focus on is that the 284 or 284 Shehane will be load limited by brass pressure signs at a "lower" pressure than an equivalent straight case design. This might not be a bad thing if handled correctly. Tony R and others can give you more feedback than I on 284 Shehane but by my readings it appears to get the 180's into the 2900+ fps range at fairly mild pressure. It is an accurate cartridge too. A lot of 284 based users push their cases a little too far in load development (me included) and then back off. But a lot of case damage is already done. I am now getting excellent cartridge life by not pushing the boundaries. A good trick is to weight sort the brass and use the "oddballs" for load development - find the boundaries where you start to get case head expansion and then back down and ditch these cases. Look for ejector marks (That means brass flow after all) and if you have one use a blade micrometer on the extractor slot or loose primers. Remember though a new barrel cannot be pushed as hard as one with a few hundred rounds through it so worth keeping a few shells and doing it again later.
The 284 is an excellent, accurate cartridge design - and if you have a 308 bolt head is easy to fit.
Compared to a short magnum the main advantage (and it is a big one) will be barrel life due to low pressures etc. The WSM's are notoriously bad, RSAUM are better and I believe the 280AI have good barrel life too but can't confirm that.

 

[Hengehold]

Tony R,
I have no intention of loading cases past 10 reloads, which the Shehane can apparently do. This raises a couple of questions.

1. Did you settle for the 2900fps range because of pressure/brass issues or did you see the group sizes open up?

2. What kind of barrel life did you get with a Shehane? I would like to see 1500-2000rds on a barrel, were you close to those numbers?

3. Of the cases that you listed, would you recommend the Shehane over the others that you have experience with?

Thanks
Trevor Hengehold

 

[Hengehold]

Camac,
Thank you for the great info. One thing is still a little unclear to me though. When you said to "find the boundaries where you start to get case head expansion and then back down and ditch these cases" where do you measure on the brass? Do measure on the outside of the rim of the case?

Thanks,
Trevor

 

[camac]

Trevor, I find the best place to measure is at the bottom of the extractor groove. You will need a blade micrometre to get in there. This is the thinnest brass and likely to move first. Generally speaking 0.0005 inch case head expansion per load is an indicaqtor you are getting hot. After a couple of firings at that pressure you will see loose primers. 1 thou is too much. I also have 1 particular shell holder that is a very tight fit. For me, I can use it as a quick gauge.
The other area I messed up was trying to push the velocity too early in the barrel. Most barrels won't be able to get max velocity until a few hundred rounds. It is another good reason to fireform at a lighter load then start to look for a higher velocity node after that.

 

[TonyR]

Trevor.
I shoot it at 2900 fps from a 31 inch barrel because that is where the barrel gave me the best vertical accuracy. I would have shot it at 3000fps but the vertical opened up there and I knew I was getting close to the upper limit. Makes me nervous to be that close to the top anyway because a load that behaves perfectly in testing will get too hot in a competition in some circumstances.
I retired my first Shehane barrel from matches at 1500 rounds but it still shoots great and I believe one could get 2000-2500 from one. 1500 to 2000 seems to be a reasonable expectation.
It's too early to tell about the other cases in competition. The "280" has done very well in the one weekend of matches I shot it in and the SAUM is shooting waterline vertical at around 2950 fps with a 28 inch barrel at 300 yards off the bench but I haven't prepped enough brass to take it to any matches yet. They both are performing in my testing about like the Shehane did in the same sort of testing so I believe they will both be comparable to the Shehane accuracy wise.
I have shot thousands of the 180VLD at this point and I believe that they have to be tuned carefully and thoroughly in every gun and barrel to get the best results. I haven't seen anything that says to me one of these cases is more accurate than the others by itself. It is all in the load development and tuning. You should chose one or the other based on your style of shooting and any limitations in the rules or other requirements that may be put on you.

 

[Hengehold]

Tony,
1. I noticed that you said, "the 180VLDs have to be tuned carefully and thoroughly in every gun." In your experience, do you have to constantly re-tune the seating depth to accommodate for throat erosion with the VLD? Or in other words, “chase the lands.” If they are seating depth sensitive, I would imagine this would be crucial. This is one reason that I have avoided VLD bullets to this point.

I shoot tangent ogive bullets in my palma rifle and almost never have to play with seat depth over the life of a barrel.

2. Also, do you know anyone who has tried the 7mm, 189gr Cauter bullets? The 180VLDs are popular but I never hear anybody talk about the 189gr. The bigger the better...right?

Best,
Trevor

 

[dodgefan]

Has anyone taken a look at the 7.5x55 schmidt rubin/gp11 the case seems to be just about what you are looking for. wikipedia has a case diagram. If I knew how to paste it here I would. It does compare pretty well to the 6.5-284 though. Might be worth looking at.

 

[dodgefan]

Here is a list of the case dimensions.

Case type Rimless, bottleneck
Bullet diameter 7.77 mm (0.306 in)
Neck diameter 8.50 mm (0.335 in)
Shoulder diameter 11.60 mm (0.457 in)
Base diameter 12.60 mm (0.496 in)
Rim diameter 12.65 mm (0.498 in)
Rim thickness 1.65 mm (0.065 in)
Case length 55.60 mm (2.189 in)
Overall length 77.70 mm (3.059 in)
Case capacity 4.22 cm³ (65 gr H2O)
Rifling twist 270 mm (1 in 10.63 in)
Primer type Large rifle
Maximum pressure 380 MPa (55,000 psi)

 

[camac]

Dodgefan - looks like a nice case to build a 7mm on. Have you looked at brass suppliers???
Cam

 

[TonyR]

Trevor.
Yes, I do chase the lands because seating depth is crucial with the VLDs. I use the Hornady tool with the modified cases. I have also found it worth doing with different lots of the same bullet. I have found that they can require different die settings to get the same cartridge base to bullet ogive dimension for the loaded round. I have a friend who shoots the 189gr Cauterucio in his 280 REM in 1000 yard F-Class matches. I have never tested them but I suspect that the gain in BC would be lost in reduced velocity but that mey depend on where the gun tunes. Bob's bullets are generally excellent. I have shot my best scores with both of my guns using Bob's 177gr 7mm bullets. Berger now makes a 175gr XLD which I believe is another secant ogive bullet and they also have a 180gr Hybrid bullet that starts with a tangent ogive then transitions to a secant ogive so it seats off the lands for most people but has a higher BC than the 180 VLD. The BC of the 175XLD is the same as the 180VLD. The Berger advertized BCs have been extremely accurate since Brian Litz started figuring out what they really are. The BC of the Cauteruccio 177gr seems to be about the same as the 180VLD, maybe a little less. I use the same loads and seating depth for both and the 177s seem to print a little lower on the paper. Whatever you do with a 7mm is likely to be more sensitive than a 308 Win according to people I know that have shot both.

Dodgefan.
I have no experience with the Schmidt-Rubin but I have looked at the 7X55 Swiss as an alternative. There are a number of cases that can duplicate the 284 Win ballistics or even the Shehane. The easiest are the the 280 Rem-class cases including the 280AI and the 7X64 Brenneke. You can make any of these out of Lapua 30-06 brass or better yet find some RWS. I have a Brenneke that shoots the 180s about the same as the Shehane. It is long with the 180s seated out but it will feed single shot through a 700 Rem SA or a Nesika K. I am told that the Australians are using a 7mm based on the 9.3X62 Lapua brass to get similar results. QuickLoad and QuickDesign can save you a fortune if you start playing with all of these possibilities. Have fun!!

 

[dodgefan]

Camac
I know Norma and Privi Partizan both make brass for it, Hornady and Wolf produce loaded ammo and HDS has Graf headstamped brass available. I was thinking of doing a modern tactical rifle on it just to be a little different from the run of the mill 308/260 tactical guys. It should have enough powder capacity to push a 200+ gr. bullet at decent velocity.
The Privi brass is cheap and decent quality from what I've seen so far of the 100 rounds I'm trying in my 6.5x55. I can't say how how it handles really hot loads because I'm only loading to about 2875 out of a 28 inch barrel. If I could pick up a heavy Savage takeoff barrel in 308 for cheap I'd build one just to test it.