7mm WSM or 7mm RM Help Please.

[Hally]

Hi all l am thinking of getting a new Barrel ( caliber) for my DTA I was thinking of a 7mm RM but then someone told me to go with the 7mm WSM.It will be used for Fclass sometimes and longrange steel gongs out to 1400m or so.Are there some of you out there that have experience with it and howe does the 7mm WSM compere to the 7mm RM thanks.

[gun nut]

Hally,

have a read at this site, should cover any questions you have. "www.ballisticstudies.com/Knowledgebase.html"

 

Mike

[Wiltshire Boy]

I shoot a 7 Rem Mag as a stalking rifle and was going to have one made as an F class rifle but was told that belted magnums weren't allowed. There are also some technical reasons why I was put off 7rm as a target round which I will pm you if you like.

 

Cheers

 

R

[gbal]

I shoot a 7 Rem Mag as a stalking rifle and was going to have one made as an F class rifle but was told that belted magnums weren't allowed. There are also some technical reasons why I was put off 7rm as a target round which I will pm you if you like. Cheers R

7 rem mag isn't a common 'target' cartridge,but there are plenty other 7mm calibre that are-perhaps its the current favourite -see 7WSM or 7 Shehane or 284 win etc. Nothing is perfect for everything,but you do should not dismiss 7mm as a calibre for longer range F class shooting- it is rather hard to beat all round!

george

[Wiltshire Boy]

Personally I went for .284 win , I discounted 7 RM not 7 mm! Previous post the RM was in lower case sorry for confusion.

 

Cheers R

[gbal]

Personally I went for .284 win , I discounted 7 RM not 7 mm! Previous post the RM was in lower case sorry for confusion.

 

Cheers R

What matters is you got it right- even if the 7 r m is only lower case necked down 7 R M !!

The old 284 win deserves a place in the limelight-though it was a mean round in the win 88 lever-but not for f class (F class)!!

Interesting too that quite a few choose not to wildcat it eg to the Shehane-it's 'good enough' as is.

atb

george

[Hally]

Thanks for all the advice the 7 WSM appeals to me as l can get a barrel off the Shelf for the DTA.Little worried about barrel life but there is all way a cost to pay l suppose.They seem to be good flat shooting cal with better recoil than the big 30 cals.

[Roebuck]

Another choice : 280 remington / 280 AI

[garyw]

Thanks for all the advice the 7 WSM appeals to me as l can get a barrel off the Shelf for the DTA.Little worried about barrel life but there is all way a cost to pay l suppose.They seem to be good flat shooting cal with better recoil than the big 30 cals.

you need vince [gun pimp] or Laurie to give there opinoins as they know a thing or two about the 7mms.

[mole-e30]

I shoot a 7x300WSM (for its technically correct name) at 1000 yard Benchrest, it is a wonderfully accurate calibre, HOWEVER it is hard on barrels, I recon I will do well to get 500-600 rounds from it, so for F-class I have gone for 284Win.

 

If I was building a long range target rifle, then 7mm of some form either WSM if its low shot count or 284Win / Shehane if the round count is higher, the BC of 7mm bullets takes some beating, however the only other option wold be a 300WSM if you can afford a long heavy barrel to push the new 230gr bullets fast enough.

 

Hope this helps.

 

Bruce

[gbal]

I shoot a 7x300WSM (for its technically correct name) at 1000 yard Benchrest, it is a wonderfully accurate calibre, HOWEVER it is hard on barrels, I recon I will do well to get 500-600 rounds from it, so for F-class I have gone for 284Win.

 

If I was building a long range target rifle, then 7mm of some form either WSM if its low shot count or 284Win / Shehane if the round count is higher, the BC of 7mm bullets takes some beating, however the only other option wold be a 300WSM if you can afford a long heavy barrel to push the new 230gr bullets fast enough.

 

Hope this helps.

 

Bruce

Bruce-you might be getting into some 'heavy gun' weight issues too with the bigger 30s and 230 g ,to tame the recoil enough to be as 'shootable' as the lighter calibres,if you go for the 'rapid shots in the same wind condition' approach,especially.No free lunch !

george

[mole-e30]

Bruce-you might be getting into some 'heavy gun' weight issues too with the bigger 30s and 230 g ,to tame the recoil enough to be as 'shootable' as the lighter calibres,if you go for the 'rapid shots in the same wind condition' approach,especially.No free lunch !

george

Hi George

 

Like they say, there is no such thing as a free lunch, there is always the inevitable "trade off".

 

That is why I like my 7WSM, but it does have a brake on it is a 1000 BR Light Gun, where brakes are OK!

 

Cheers

 

Bruce

[gbal]

Hi George

 

Like they say, there is no such thing as a free lunch, there is always the inevitable "trade off".

 

That is why I like my 7WSM, but it does have a brake on it is a 1000 BR Light Gun, where brakes are OK!

 

Cheers

 

Bruce

Bruce,

That brings back memories of being in a Diiggle relay between a braked 338,and a braked 30 BooBoo ,and hoping they would frire simultaneously,so that I could get a shot of too,'moderately' balanced by such blasts from either side.Didn't workout!

There weren't many,or any,big heavy 30 bullets in evidence then (or even WSMs!)

Having done the math,to be as 'shootable' (and 70 " wind deflection) as the 16 lb 6.5s 142 g @ 2950,the 30 with 220g will need 2650 fps and need to be 23.2 lb! The 7mm will get by nicely with 2800fps,175g and 18.9 lb.(as you know!!)

 

No wonder the faster 7s are back.

 

A a big 30 can work,but it's not the thinking man's route.

The 224s with a 90g "just" need 3270fps,but only 10.3 lb weight, so a no go,I think.

 

As ever,there is choice for the newcomer,but the above need to be bourne in mind!

 

george

[Laurie]

Hally,

 

returning to your original question, re 7mm RM v WSM, they're very similar in terms of case capacity, so will provide the same performance, recoil and barrel life with any given bullet allied to loads producing similar pressures.

 

Having said that, the WSM is a superior design as it has done away with the case-belt. Belts and accuracy cartridges don't mix well as the belt tends to change dimensions under repeated doses of heavy pressure thereby affecting case to chamber fit and consistency. Having said that, there are many instances of very accurate 7mm RM rifles over ther years. Nevertheless, WSM makes for a better choice and has very good if pricey Norma brass available for it. 7mmWSM rifles (or more likely 7mm/300 WSM as Bruce uses it being preferable to start with the 300WSM case) built to BR and F-Class standards have achieved remarkable long-range results in recent years including The Gun Pimp's 1,000yd UK BR Association record group and the scores you see in the annual GB F-Class Association Long-Range meeting at Bisley with its 1,100 and 1,200 yard matches. F-Class world champion Gary Costello (of March Scopes UK and Magnetospeed chronograph fame) tells me he did 1,400yd plus testing of the 7mmWSM F-Class loads against .338 Lapua Magnum rifles and the seven was superior at these sorts of distances.

 

As Bruce and George point out, you get nowt for nowt and pay for the WSM's performance with barrel life - 600 to 1,000 rounds depending on how much fuel you stick in the furnace. Here are the case capacities of the major long-range sevens as measured by filling the case to the brim with water and reweighing it:

 

284 Win ............... 66gn

280 Rem .............. 68gn

280 Ackley ........... 74gn

7mm RSAUM......... 72.5gn

7WSM ................... 81gn

7mm Rem Mag ..... 82gn

 

The rule of thumb is to calculate the % change in capacity and divided that figure by 4 to get the % change in MV for any particular bullet and providing the cartridges are loaded to the same pressure.

 

So 7mm RM at 82gn is ~16gn = 24% larger than .284 Win. It'll therefore give a 6% MV improvement.

 

Looking at it the other way round, if a 7mmWSM gives a 180gn bullet 3,000 fps at maximum pressure, the 284 will give it ~6% less, or 180 fps for 2,820 fps MV, pretty well what happens in real life. You get ~2,000 round barrel life though from the .284W for the loss of 180 fps MV unless you load the 284 to silly pressures - ie a 200-300% barrel life gain for loss of 6% performance.

 

Being a Yorkshire Scot, my vote doesn't need to be spelled out!

 

So, it's down to how you plan to use the rifle and how often. The WSM gives a short but merry life well suited to Bench Rest with its much lower round counts, and to national league Effers who have to grab any ballistic benefit they can at almost any price, the 284 is better suited to the club shooter wanting a highly capable round that lets barrels last two or three seasons. Both are capable of superb precision in the same quality rifles.

 

Of the others I've listed, the Remington SAUM should be a real contender, but hasn't made inroads here for some reason. The 280 Rem and 280AI Rem are seeing growing use in the US especially by people rebarrelling a long-action rifle with standard 0.473" dia. bolt-face. They're getting some very good results in the right rifle and in the right shooter's hands. At 74gn water capacity, the AI version is similar to the SAUM and mid way between WSM / RM performance / barrel life and that of the 284 / 280.

 

I had a hankering for a 280AI F-Open rifle for a while using my Barnard P based Eliseo tubegun and using a slightly short-neck version of the cartridge. That let's you form the brass from Lapua or Norma .30-06 cases. In the end after lots of thought, the variation on my FAC says '.284 Win' - boring but practical and cheaper. (Already got the brass, no custom reamer needed etc, etc.)

[Hally]

Thanks Laurie l haven't been a member of this forum all that long but long enought to know that when you post something it is well worth reading.I haven't given the 284 a lot of thought but l will have a long hard look.One thing that I'm after when not using it for Fclass we will be using it for a little longrange steel gongs out to 1400m or more and wondering about the ability of the 284 to do this.And we will be pressing it into work as a hunting round as well on Reds and Camels and Pigs so a little of every thing l suppose.Not asking for a lot am I.Thanks

[Laurie]

.284 Win MVs would barely keep you supersonic at 1,400M unless you're shooting at high altituides in warm conditions. For 1,400 / 1,500 yards tthe extra couple of hundred fps from the WSM / RM size cartridges would probably be valuable.

 

180gn Berger VLD at 2,800 fps = 1,196 fps at 1,400 yards and subsonic at 1,500.

180gn Berger VLD at 3,000 fps = 1,326 fps at 1,400 yards and 1,232 fps at 1,500.

 

That's under standard conditions (59F and 29.92 inches mercury pressure) claculated by Litz / JBM using a G7 BC value. (Speed of sound is ~1,126 fps under standard conditions.)

[gbal]

.284 Win MVs would barely keep you supersonic at 1,400M unless you're shooting at high altituides in warm conditions. For 1,400 / 1,500 yards tthe extra couple of hundred fps from the WSM / RM size cartridges would probably be valuable.

 

180gn Berger VLD at 2,800 fps = 1,196 fps at 1,400 yards and subsonic at 1,500.

180gn Berger VLD at 3,000 fps = 1,326 fps at 1,400 yards and 1,232 fps at 1,500.

 

That's under standard conditions (59F and 29.92 inches mercury pressure) claculated by Litz / JBM using a G7 BC value. (Speed of sound is ~1,126 fps under standard conditions.)

 

Thanks Laurie l haven't been a member of this forum all that long but long enought to know that when you post something it is well worth reading.I haven't given the 284 a lot of thought but l will have a long hard look.One thing that I'm after when not using it for Fclass we will be using it for a little longrange steel gongs out to 1400m or more and wondering about the ability of the 284 to do this.And we will be pressing it into work as a hunting round as well on Reds and Camels and Pigs so a little of every thing l suppose.Not asking for a lot am I.Thanks

284 is a bit overstretched as a target 1400y cartridge,as Laurie makes clear.So are most cartridges in this class,even if tweaked like the Shehane,or AI versions.But fun to try.

 

The 284 is pretty well a ballistic clone of the 280 rem,itself essentially a necked down 30-06 (like the 270w) and therefore performs pretty much the same as the 280 rem -ie well ,on appropriate game(depending on bullet etc, around 2750 ft lbs in factory loadings). A very fine red deer cartridge.Specific data on camels is not to hand!

george