260 rem 123gn ELD-Match & N560 1:8 twist

[Mick Miller]

@DaveT @TJC What sorts of velocities and charges are you using? I ask because the book states 2900fps at maximum load, understanding that there is a fat chunk of caution thrown into modern reloading manuals and every rifle is different. In other words, I'm not intending to cut and paste your loads, just interested in what 550 gives you for a given charge.

[DaveT]

Mick

26" Kreiger barrel , Lap brass, cci br primer, 41.5g N550 gives 2908 fps and no pressure signs whatsoever......loaded to 2.88 and feeds fine from AI MAG.

Coudn't see any need to push it harder.

[Mick Miller]

FWIW these are the results from the N150 trials.

I have a 1kg tub of N550 to trial next.

[DaveT]

Should give you a decent speed hike up around 41g - 42g of N550.

See if you can extend col beyond book (saami / cip) to give yourself some pressure headroom.

[The Gun Pimp]

I wouldn't have thought you were anywhere near a full case at 39.5gn of N150

I was running mine with 45gn of Elcho17 (similar to Reloader 17 or RS 60) which was pushing a 123gn Scenar at over 3000fps. But, that would be from a 29 or 30 inch barrel.   The Vit N150 is probably a bit slower than Elcho 17 (Maybe Laurie would comment?)    

The much smaller 6.5x47 Lapua will get close to 3000 fps with a 123gn bullet and with excellent accuracy.

I never found the 260 to be a good 1000 yd BR cartridge but if I were to try one again I'd be forming the brass from Lapua's 308 Palma (with small primer pocket).

As always - these loads were safe in my rifle but may not be safe in yours - work up loads slowly

[Laurie]

N150 is a rather bulky powder and 40.5gn was mildly compressed in Lapua brass in my chamber (your 260 reamer Vince). Interesting as to how MVs (and therefore pressures) vary according to chamber and barrel dimensions. 40.5 N150 was giving me right on 3,000 fps from a newish Bartlein 5R 30-inch, but after a couple of hundred rounds started blowing primers - the classic pressure rise syndrome as a barrel runs in fully, as mentioned by Baldie in another recent thread. I didn't retune that particular load it, so don't know what would have been the final optimal charge weight, but MVs were WAY above those posted above. This was an N150 lot of a few years vintage, and I have a suspicion that this particular powder grade varied more between lots than I usually associate with Vihtavuori in those days. (It dated from the period when Vihtavuori  was part of Eurenco and was being run down prior to a possible closure, and before Nammo Oy  rode up as a white knight and saved the plant / company.)

30-inches of TrueFlite barrel also gave me 3,000 fps in 6.5X47L with the 123 Scenar and same lot of N150, but the barrel life was very poor - I think that TF made some poor barrels around this time, or used an inferior grade of steel maybe - it was just after the original owners sold out and before the new ones seemed to get their act together. Or .... maybe the load was just too hot and I got away with it for a while as 6.5X47L doesn't show pressure until ejector marks / blown primers show up. Elcho-17 / Re17 / RS60 will give significantly higher MVs in these cartridges than N150 - or the same MVs at lower pressures - having a higher specific energy rating, but more important even, the special EI deterrent infusion system that really does extend the initial peak part of the pressure-bullet travel  curve and flatten it.

I've never used my FN SPR in BR (except for one Diggle winter 300-yards 'Precision Rifle Comp' back in its original factory 308 Win days - that must be a long time ago as the 300 winter comps morphed into the current 600-yard UKBRA series many years back). It must be one of my few rifles that I've not shot in 600 or 1,000 BR at Diggle! I did have good results in Diggle F-Class with it in 260 Rem at out to 800 yards with the 123gn Scenar, best result being 99.8v, the dropped point just outside the 5-ring at 7 o'clock that would have scraped a 5 if it hadn't dropped a half-MOA out of the pattern, all other 19 shots staying within a half-MOA elevation band.

This is the rifle that's about to become 260 Rem AI. I really like the FN (Winchester 70 pre-64 type) action and McMillan A4 stock. It would have become a 6.5 Creedmoor, but a fat and loose-fitting firing pin sees it blank SR primers at low pressures / velocities , so it has to remain a LR primer equipped calibre. (I could of course still use the Creedmoor, but if I can't use SRP Lapua brass, I'd rather have the 260AI's extra case capacity.)

[Mick Miller]

2 hours ago, The Gun Pimp said:

I never found the 260 to be a good 1000 yd BR cartridge...

This is the extreme that I'll be shooting it at. More often our 'long distance days' are 600-800 yards. Occasionally we get to play at 1000, so it would nice to be having something that can reliably get me onto paper, even if it's not going to win me anything. If I find I enjoy the long distance stuff a bit more I can consider losing one or two other guns and investing in something that is tailored for that discipline alone.

This rifle, however, would be equally at home foxing or on a hill, well maybe a bit too heavy for the hill but nonetheless, I could get by with it (and frequent rest stops).

I'm keeping my fingers crossed the 550 works, I almost bought a tub of RL19 instead, in the books it suggests that it could get me there with ease.
This is a brand new rifle - do I need to look out for issues once it's run in?

 

[Mick Miller]

Back from another load of velocity tests with n550. What a disappointment. At maximum book charge of 41.5gns I managed 2730FPS. At 1000 yards that will still be supersonic, but only just.

Wish I'd gone for trying the RL19 next now instead. 

[TJC]

Surprising. I was out yday getting 2800 with 40.0gr N550 pushing both the 140 RDF and 139 Scenar. 

[Mick Miller]

Not sure if it being a new barrel affects velocity at all? I'm going to up the charges gradually and see what happens. At 41.5gns I have no sticky bolt, no change to primer, no different to the starting charge.

All velocities recorded with Magnetospeed v3, so I'm confident that the measured MV is correct.

 

[TJC]

A new barrel tends to speed up so at the margin that should help but 41.5gr N550 pushes the 123gr 2750 FPS according to VV data...and that’s with an 18” barrel ! Remind us what barrel length and brass you are using ?

I’m getting 2930 with a 130gr and that’s with factory ammunition so it puts things into perspective. I don’t doubt your data. The magneto is great. 

[Mick Miller]

Barrel is 600mm varmint (Tikka T3x). Brass Remington 243 sized to 260 and formed.

(in old money 23 5/8")

[TJC]

VV data is considered conservative. If you can edge up the powder a little it could help. Be careful and remember that N550 is temp sensitive so what you achieve when it is 5 degrees out won’t be the same come spring/summer. 

[Mick Miller]

So, does this mean developing two loads? Winter/spring, summer/autumn? I think I may revisit the N160 too and see if upping the charge there has an effect as there weren't any signs of pressure with that combo either.

How temperature unstable are the double base powders? Will I be likely to encounter a sudden spike on hot days?

[TJC]

I’ve found a 1 FPS change for 1 F degree change with N550 and I’ve found it to be reasonably linear ie predictable. 

[Mick Miller]

Good to know.

 

[Mick Miller]

Full 550 data (max book load for both and N150 is faster)

[James 1]

I also have a 260 and I’m using eld-x 143grn 20tho off over 44.8grns of n560 which give me good groups with no pressure signs, just need to chronograph them when the weather is better, this load has taken me a while to find. 

Cheers James 

[Mick Miller]

I'm up to 43.2gns for 2870fps with N550, next few loads will be in .2gn increments up to 44.2gns. So far there are no pressure signs, bolt lift fine, primer fine. I think if I can get around another 30fps, which should be on the next step, I can play around with seating depth to tune the groups.

I'm going to try 143gn bullets too as the 123gn ELDM's group pretty badly so far.

[DaveT]

I have found it harder to find loads that see Hornady bullets group well  vs Scenars ........if you can lay hands on a few 123g Scenars I think you would be pleasantly surprised how they perform with N550.

[Mick Miller]

I have some kindly given to me to try. Only problem is, they won't be any good for hunting whereas the ELDM's likely are (despite being a 'match' bullet). I'm trying to get a 'one-bullet-fits-all' solution. It probably won't work out that way.

 

[Mick Miller]

Final word on this bit of load development, save playing with seating depths. A stout dose of N550, 44gns to be precise, produced 2907fps over 4 shots with an S.D of 5.5fps. Next up is, as mentioned, seating depths now that I have replaced the stock magazine with a Waters Rifleman Gen.5 6-shot magazine to allow longer seating depths.

There were no pressure signs in my rifle, the load was cross checked in QL to make sure it fell beneath simulated max chamber pressure just to be safe. Coincidentally, the QL stated max velocity matched the results from the Magnetospeed.

These test loads were all .060" off the lands, so I'll try 20 thou, 40 thou, 60 thou and 80 thou off the lands and see which out of a series of 5 shot groups proves to be the best.

Your rifles mileage may vary. Please work up any load based on this result carefully.