Choice of 6.5

[justin credible]

For long range the 7mm will outshoot the 6.5 due to bullet weight and higher bc. A 284 lobbing a 180 gr bullet with nearly a 0.8bc at 2880 (just under HME) will give a barrel life of around 2500 rounds as well.

I don’t know anyone who shoots top level F Open who uses a 6.5 variant, it’s either a 7mm or a 30cal magnum that wins every time. 

I have been fortune to recently buy a rifle that has 2 barrels which can be changed in the field. The barrels are a straight 284 and a 6.5creed. The 7mm will be used for the ELR days at PRL and the 6.5creed will be used for the shorter range PRL days so the best of both worlds in one rifle.

 

 

 

[No i deer]

According to my ballistic calculator a 139gr scenar in my 6.5x47 the bullet will drift 84 inches in a 10mph full value wind

My 184gr hybrids in my 7mm saum will drift 61 inches..

If I was to use the 180gr ELDM's and 190gr A tip bullets it's 5 to 10 inches less than the 184gr hybrids.

Again according to my bal cal a 180gr ELDM shot 100fps less in my 26 inch barrelled 284 it shoots inside 184gr hybrids in my 30 inch 7mm saum..!!

[OSOK]

This really isn't that hard to understand .... BC's are higher in 7mm's than 6.5mm's so on a day when the wind is up a good shooter with a 7mm will should beat a good shooter with a 6.5mm . You really need look no further than 1000 yard F Class shooters around the world and they don't use 6.5's anymore ... It's either 7mm's or 30 Cals . I've seen very good 6mm's and 6.5x284's clean up at 600 & 800 yards on calm days but thats not common . Anyone who remembers the 2009 world F Class champs at Bisley where the US team bought 6.5's and were hammered by our 7mm's .... Top 13 positions from memory were UK 7mm's !

To try and push any 6.5 to compete with a competitive 7mm you would end up with a barrel burner / limited barrel life  and too much heat across your 2 & 15's that i found would give poor results .... better to  run a 7mm in WSM , Saum or 284

Whatever you build keep the weight upto the max allowed ... I always found that this helped especially if it was a heavy action , rings and scope etc ... ie , right over where it goes bang and not as an after thought in the ass end of the stock .

OSOK

[One on top of two]

Is the OP intending to use it for F Class ? 

[The Gun Pimp]

5 hours ago, No i deer said:

According to my ballistic calculator a 139gr scenar in my 6.5x47 the bullet will drift 84 inches in a 10mph full value wind

My 184gr hybrids in my 7mm saum will drift 61 inches..

If I was to use the 180gr ELDM's and 190gr A tip bullets it's 5 to 10 inches less than the 184gr hybrids.

Again according to my bal cal a 180gr ELDM's shot 100fps less in my 26 inch barrelled 284 shoots inside 184gr hybrids in my 30 inch 7mm saum..!!

How much does the 139gn Scenar drift when launched at 3400fps (6.5WSM)?

[OSOK]

The OP said he wants 1000 yard accuracy and I've used F Class as the benchmark of that .

I was running both 139g Scenars and 155g Cauto's through mine at 3,400 ish but had to back both back to 3,268 & 3,210 to get them to shoot well at which time they had lost any advantages .

My 6.5 WSM running at 3,400 was the same as my 7/270 WSM running at less than 2,900 given my bullet choice etc .

OSOK

[Kalahari]

Reading all this with interest. Long range stuff isn't really my thing but it is interesting all the same. My rather simplistic view on page three seems that it is a bit like boxing, "a good big one will beat a good little one" but perhaps/probably I have got it wrong. It seems that the problem of launching a relatively light bullet at very high velocity is that drag is a squared factor of velocity so it slows the light bullet down pretty quickly.

 

David.

[MarinePMI]

1 hour ago, OSOK said:

The OP said he wants 1000 yard accuracy and I've used F Class as the benchmark of that .

I was running both 139g Scenars and 155g Cauto's through mine at 3,400 ish but had to back both back to 3,268 & 3,210 to get them to shoot well at which time they had lost any advantages .

My 6.5 WSM running at 3,400 was the same as my 7/270 WSM running at less than 2,900 given my bullet choice etc .

OSOK

Running 140gr class bullets at 3400fps; you likely have bullet deformation occurring. Backing it down is the only option aside from rebarreling with a gain twist.

 

Shooting solids might be another option.

[The Gun Pimp]

1 hour ago, MarinePMI said:

Running 140gr class bullets at 3400fps; you likely have bullet deformation occurring. Backing it down is the only option aside from rebarreling with a gain twist.

 

Shooting solids might be another option.

No, I didn't blow any up but barrel -life was about 400 rounds in F Class.  Great round though.

[No i deer]

4 hours ago, The Gun Pimp said:

How much does the 139gn Scenar drift when launched at 3400fps (6.5WSM)?

I will work it out later Vince 👍

[Popsbengo]

Lot's of excellent input there thanks.   Done some reading elsewhere and I'm starting to think 7mm SAUM or WSM now.  I'm not into competing as I don't want to be tied down to comp dates.  I do however what to shoot as well as I can possibly do.

All I need now is a gunsmith to make dreams into reality...

[No i deer]

The 6.5wsm  pushing a 139gr scenar at 3400fps will drift about 1 inch more than the 184s in my saum according to my bal cal figures but we wernt talking about super duper wildcat 6.5s that I was aware of..

400 shots barrel life 😅

[KABOOM]

5 hours ago, MarinePMI said:

Running 140gr class bullets at 3400fps; you likely have bullet deformation occurring. Backing it down is the only option aside from rebarreling with a gain twist.

 

Shooting solids might be another option.

Very interesting, how does one know if the bullet deformed or some other malady caused a keyhole? I would tend to guess any recovered bullet deformed on impact the backstop. This makes my brain itch so please enlighten me.

[MarinePMI]

5 hours ago, The Gun Pimp said:

No, I didn't blow any up but barrel -life was about 400 rounds in F Class.  Great round though.

I'm not talking about blowing bullets up per se, more so bullets becoming deformed and showing less accuracy as the bullet "wobbles" due to the deformation.  This is when the bullet is long for caliber,and pushed too hard into the lands.  The front half of the bullet begins to spin as the lands take hold, but the rear resists, and so the bullets begin to deform, separate jackets and/or create weird voids.  A gain twist barrel helps ease (or ramp up gradually) the RPMs, lessening the deformation.

 

It's also why GT barrels allow a slightly faster speeds as well as being very tolerant of different bullet lengths.  The first I heard of it, I was a bit skeptical, but I've been running a GT in a 224 Valkyrie and it's been very accurate as well as faster than one would expect for a given charge and bullet weight.  I am well over book max with 75gr bullets and 2000MR powder, so the flattened pressure curve theory of a GT barrel appears to be well founded. 

 

JMTCW...

[MarinePMI]

22 minutes ago, KABOOM said:

Very interesting, how does one know if the bullet deformed or some other malady caused a keyhole? I would tend to guess any recovered bullet deformed on impact the backstop. This makes my brain itch so please enlighten me.

There's no way to see it; it's anecdotal for the most part.  The big thing is, when pressure/load/velocity goes up, and accuracy degrades, with long for caliber bullets, it's a sign that the bullet is being deformed.  The ELR guys see it a lot (and hence a lot of them going to shooting solids to gain a little bit more forgiveness).  Even solids will deform, so there is no free lunch or magic cure.  It's just physics.

This is what is driving some of the next generation bullet/ammunition developments (SIG .277 Fury for example).  Exotic metal bullets and barrels, bi-metal cases, 30-40% increases in chamber pressures; we're in a time of change in the oldest part of the firearms industry...the ammo itself.

Hoplite Arms is working on a lot of this newer tech, and it's proving to be quite interesting.

[KABOOM]

1 hour ago, MarinePMI said:

There's no way to see it; it's anecdotal for the most part.  The big thing is, when pressure/load/velocity goes up, and accuracy degrades, with long for caliber bullets, it's a sign that the bullet is being deformed.  The ELR guys see it a lot (and hence a lot of them going to shooting solids to gain a little bit more forgiveness).  Even solids will deform, so there is no free lunch or magic cure.  It's just physics.

This is what is driving some of the next generation bullet/ammunition developments (SIG .277 Fury for example).  Exotic metal bullets and barrels, bi-metal cases, 30-40% increases in chamber pressures; we're in a time of change in the oldest part of the firearms industry...the ammo itself.

Hoplite Arms is working on a lot of this newer tech, and it's proving to be quite interesting.

Thank you im wrapping my head around the theory, makes some sense.