Are the most accurate loads always the fastest?

[Watcher]

I’m working on a load for my .308 TR. I’ll be using Lapua cases, SMK 155 bullets, CCI Large Rifle primers and Viht N140. The Viht manual shows the lowest charge as 37 grains and the highest as 44.2. If I work on .3 grain increments this will work out at some 25 separate loads which is quite a lot.

Is it valid to assume that my ideal load lies towards the top of the range? I have received recommendations that this is the case but also understand the need for a safe progression. In these circumstances is it better to start at, say, 40 grains? Is it likely that my ‘ideal’ load lies in the lower reaches.

My objective is to create a TR load that’s good up to 1,000 yards.

[Steve E]

What rifle and what barrel are you using. If your aim is to shoot 1000yds with any accuracy your load will be at the top end of what the Vhit' manual states. it may even be higher. PM me

Steve

[Watcher]

Done

[rox]

Are the most accurate loads always the fastest?

In general, no. But there's certainly a minimum practical velocity required to achieve consistent performance at the upper limits of the reach of the 308 (i.e. at 1000 and beyond). Falling into the transonic region is reckoned to be bad news (although some thinking reckons this to be over-hyped). Nevertheless, for consistent 1000 yard TR performance 2900 to 2950 fps seems to be the accepted minimum velocity required to achieve performance comparable to typical competition factory ammo (RUAG, HPS etc). I doubt you would achieve this velocity even at the maximum load you quote from the manual. Of course, the loads in the manual are designed to cope with the worst case and lowest denominator in terms of case & chamber dimensions, strength of action etc. Some argue that they should never be exceeded, but you may also consider that some CIP-tested factory ammo certainly does exceed those maximums, and by some margin, and it passes the testing. Whatever you do, you should certainly work-up from starting loads, but for 1000 yard shooting you are unlikely to find viable loads at the lower end of the range, so your interval can be larger there, and you're looking for pressure signs, not groups, so it needn't take loads of rounds and time.

..

[Steve E]

Every thing that ROX says is spot on. You will not go far wrong with his advice.

Steve

[Watcher]

Thank you both.

Watcher

[GazMorris]

Another vote in favour of what Rox (and Steve E) are saying.

My personal experience is that nearly all sensible loads in a 308WIN will shoot acceptably for TR* at short range but you'll need circa 2900 fps to get good groups at 1000 yards with the old 155 Sierra, and maybe a little less with some of the more ballistically efficient bullets. In my rifle this happens at about 45 grains with N140 or 44 grains with TR140** using Sierra 155s, Remington 9 1/2 primers and RUAG cases.

I have done minimal tuning to get handloads to shoot at least as well as RUAG in my rifle (other than working out roughly where the max load lies.) I take once-fired RUAG cases from my rifle, do some basic checks on the cases, neck size, clean the primer pocket, prime, fill and seat. Works out at about half the cost of new RUAG. I've ended up with what I think is close to the most accurate load (about a grain and a half under max) based on a small number of test-firings but couldn't prove it statistically.

Good luck.

GazM

* But not BR or F-Class. They're a whole different kettle of fish because the rifle wobble is much less, so there is a much finer ability to separate ammo from hold.

** This where I get 2900fps in my rifle but it may be more or less in your rifle. These loads may not even be safe at all in your rifle. Please work up carefully.

[Dangermouse]

lowest charge as 37 grains and the highest as 44.2

I would do one of each along the lines of,

37gn
37.5gn
38gn
38.5gn
39gn
39.5gn
40gn

Then two loads of

40.5
41.0
41.5

Then two loads of each going up in .3's, going higher than the advertised maximum load.

Shooting two of the higher loads gives you more confidence in stepping up and should you get a slightly stiff bolt or questionable primer you can compare before moving on.

Should this be a new rifle / barrel, you can do this as part of the shooting in process,

DM

[IainWR]

Chucking in my one reloading experience.

My recent GB team to SA used RUAG cases, SMP 2166 bullets and 46.0 (+/- 0.1 over 13200 rounds which was a phenomenal task) grains of Vhit N140. Given that we were loading for a group we took the trouble to have it pressure tested at the Birmingham Proof House. It came in within the reduced pressure limit applicable to reduced dimension firearms under rule 150 Bore and Chamber dimensions ie under 3650 Bar max Average Working Pressure out of a standard CIP test barrel. This is also the pressure limit for RUAG 155 as supplied to the NRA. The CIP limit is 4150 MAWP, which coincidentally is the extreme limit for the Proof Houses agreed reduced limits.

So, provided its done carefully, it is possible to go beyond the Vhit limit. Of course, once you exceed any published limit you are on your own as to justifying it. The fact that my team did it does not entitle you to quote our experience - and before you ask we can't sell our experience, but you could reproduce it. I remind everybody of NRA rule 256: a competitor is responsible for ensuring that his firearm and, if provided by himself, his ammunition, is safe to use (other NRA rules require that your rifle meets strict conditions if you are using issue ammunition).


Iain
Not answering for the NRA, but quoting a rule book that he might have had something to do with.

[Watcher]

Thanks everyone; I'm much more comfortable now.

W