155 scenar factory loading

[Swamp Donkey]

Hi all, does anybody know what powder Lapua use in the factory 155gr scenar loads ?

I'd like to duplicate if poss as they shoot better than I can at 1000 yds, or am I still better off doing the usual load development instead ?

Or, has anyone any pet loads using n140 that works well in anything ?

 

Cheers

 

Pete

[alpha1]

43.2 grains of N140 with 155grain a max works for me at 300 yards don't know about 1000yards I have never had access to a range that long.

[Offroad Gary]

46 n140 and 155 scenar in any decent rifle works. Usual rules apply, work up etc...

[Laurie]

It's likely a 'non canister' bulk version of N140 that's used by Lapua with the load reworked for each new powder manufacturing lot. So develop your own loads with N140 or the very similarly performing Swiss TR140.

[Nicky]

Hi it's Nicky, used N140 and N540 with 46.4 grains, 155 scenar 308. Got to 1000 yards. In summer had to back off and use 46.0 as loads started running HOT. Primers were showing problems.

[brown dog]

Agree with Laurie. Non std powder in the factory ammo.

 

 

My standard load for 24" AWP barrels was:

OAL 72.9mm or 2.87"
46gr n140,
155 scenar
Fed 210M

in Lapua brass.

 

 

46gr seems to be the universal constant. The OAL I've listed is the same as factory. Can be a smidge hot in some barrels.

 

Backing off to 45.5gr in summer brings no noticeable change to performance, just keeps you on the correct side of the pressure precipice.

[MJR]

Don't wish to highjack swamps post but what sort of velocity does this load average? Actually that info might be helpful to him to.

Thx.

[Swamp Donkey]

Hijack it as much as you wish

[Davy]

Lapua .308 factory were usually filled with Bofors powder. I might even have a copy of an email from Lapua confirming this.

[Offroad Gary]

Don't wish to highjack swamps post but what sort of velocity does this load average? Actually that info might be helpful to him to.

Thx.

2850 from my AE

[Scotch_egg]

2850 from my AE

 

What length barrel?

[Offroad Gary]

What length barrel?

24" and black

[Scotch_egg]

The colour makes all the difference

[onehole]

Hi ,,,I have a stonking accurate load with 155,s A,max and Scenar at 44/140 in a 24" HV tube.This gives around 2750 .Not sure that thats enough for 1000 yards . Interestingly I am now in search of the next accurate node and went to the range yesterday and shot two tiny test groups with 44 but with 45 and 45.5 preloaded rounds theydidn,t perform as good as the 44g load.Primers still looking good so will retry with 45.8,,46 and 46.3 on next calm day,,,,hope its in there somwhere.

[MJR]

Onehole, thanks for the info.

 

Has anyone tried N150 with the 155gn bullets?

[Laurie]

Onehole, thanks for the info.

 

Has anyone tried N150 with the 155gn bullets?

 

Yes. It works very well at the expense of some velocity.

[MJR]

Thanks Laurie, shame velocity suffers.

[dRb]

Using Privi brass in my Sako M591 in .308, I was starting to see pressure signs at 44grn N140 @ 71mm COAL.

 

2013 Viht manual gives 43.4grn max too, so I'd work up to 46! :s

[Laurie]

dRb,

 

as with any cartridge, max charges are affected by a number of factors which often do not have a great effect in themselves, but cumulatively do.

 

The single biggest is chamber throating. NOT COAL per se, as that may be severely reduced from its allowable maximum by loading to what fits a magazine. Most .308 Win rifles see a longer COAL than the 2.810" SAAMI value before the bullet ogive starts to touch the rifling lands, 2.9" or thereabouts with 155s not at all uncommon with factory sporter or tactical rifles.

 

Then there is chamber size and brass construction. Thin brass (Winchester / Norma) will often see a full extra grain of a powder in the N140 class used to get to full pressures compared to the thickest / smallest capacity examples.

 

Bore dimensions. The old 7.62mm No.4 Enfield based rifles with Enfield Lock barrels are TIGHT - that's why the NRA stongly advises that the RUAG / RWS ammo is not used in these rifles, as well as their having a weaker action. Most modern TR rifles use slightly tighter bore and groove dimensions than the SAAMI 0.300/0.3080" spec and this raises pressures. Despite that, most such rifles need a bit higher charges of N140 than the 44gn level, and many run very happily and safely indeed at ~46gn. Many factory rifles are either on the SAAMI dimensions or are a bit looser, but you don't know until you start loading for a rifle.

 

Finally, there is the bullet. Generally, you don't find a great deal of pressure difference between different makes and models sharing a single weight, but it can and does sometimes make a noticeable difference. I've found that the 155gn Hornady A-Max produces significantly higher pressures than Sierra and Lapua 155s, so much so that I'll normally drop charges half a grain.

 

So, working a load up sees a fair number of individual factors at play and the sensible handloader uses the manufacturer's data as a guide not as a cast iron rule. Occasionally, maximum loads in manuals are too high for a particular rifle and set of components. However, for some reason or other, some of Vihtavuori's .308 Win data are VERY conservative. The water capacity for current Lapua brass fired in a 'minimum SAAMI' chamber is ~56.1gn. Using this and assuming that the chamber is so relativelly short throated that Viht's 71mm / 2.795" COAL is the optimum just shy of the rifling, the company's maximum charge weight of 43.4 N140 for the 155gn Scenar, and 44.2gn N140 for the 155gn Sierra MK produces a calculated PMax of 54,480 psi and 50,279 psi respectively - very low indeed.

 

When you say you're getting pressure signs, can you say what they are?

[Swamp Donkey]

I tried out several loads today, starting from 44.2 as a known safe load in my gun, I was going up in .3gr intervals, using fed 210 primers, I had no signs of hot, apart from flat corners to primers, till 47.6 where I was getting an ever so slight marking to the head upon bolt lift, still easy to lift, just leaving a very small 'scuff' so 46 is good to try. Also, going from 44.2 to 46 needed 3moa less elevation at 900 so clearly a more 'potent' charge for 1000 yds. This is with new Lapua brass.

 

Pete

[dRb]

Primers flattening out on their edges, and the bolt trying to rub off the head stamping on lifting.

 

I'll run the test string again to be sure.

[Swamp Donkey]

It's only trying to rub off the headstamp at 47.6 gr, 46 is fine.

[Laurie]

Primers flattening out on their edges, and the bolt trying to rub off the head stamping on lifting.

 

I'll run the test string again to be sure.

 

 

Are you neck or full-length sizing? Circular marks on the case-head are often caused by the ejector button as you chamber a round and extract the case as a result of the case being a slight longitudinal crush fit in the chamber. This forces the case-head tight onto the bolt-face and ejector. This is a common feature on neck-sized brass as the shoulder moves forward a little on each firing. Likewise, setting the COAL so that the bullet is well into the rifling which produces the same effect on chambering the round.

 

I rarely see circular marks around the case-head face caused by excessive pressure. What IS such a sign is the casehead showing even the slightest raised extrusion at a single point where it's been distorted by excessive pressure swaging it into the ejector cavity, or any other such feature on the bolt-face. At this point, you usually but not invariably get noticeable resistance on raising the bolt handle due to additional effort needed in primary extraction and the bolt-face cutting the little extruded section as it's forced over it.

 

How often have you fired the cases and are primers still a good fit? Any case that shows true pressure signs externally usually sees the case-head and with it the primer pocket expand in two, at most three firings so it has to be scrapped. A not uncommon life for Lapua standard (large primer) .308 Win brass with true 'warm to hot' loads is five to six firings at which point the primer fit is noticeably looser even though it's still just tight enough to avoid gas leakage. These loads wouldn't cause any case-heads marks to show when the brass has been properly sized and the shoulder 'bumped' back by one to two thou'.

[Swamp Donkey]

It was new brass Laurie. I'll see if a photo will show the mark and post it here

[dRb]

It's only trying to rub off the headstamp at 47.6 gr, 46 is fine.

I was answering re what signs I was seeing