Confused

[tony]

Loading some 6.5x55s using N160 and Berger 130gr VLD hunting B/heads, new Lapua cases neck sized and deburred, cci BR2 primers, B/heads seated .063" off lands.

 

Following the load data from the Berger manual, start load at 43.0grs to a max of 45.6grs.

My loads were 3 X 44.0grs

3 X 44.5grs

3 X 45.0grs

3 X 45.5grs

My results were as follows, (100yd target), the first two groups were around an inch, the second two groups were clover leaf, so good result there, job done!! Well not quite, firstly all the bases of the cases had pressure marks on them, this was a bit worrying, why should there be pressure marks on the starting minimum load? secondly all the cases on all the loads had equal amounts of black soot down the sides, in my experience this is usually caused by a too light a load and generally disappears when the load is increased? I stand to be corrected and would appreciate any help and advice you guys can give me.

Thanks Tony.

[silentsoulsleave308holes]

when you increased the loads from the minimum load did the pressure marks on the cases decrease ????

 

it is possible to get these signs when the under loading for instance it is considered dangerous to start at the minimum start point with 300wm and it is recomended to start at 10% below max and work up or down from there.

 

not saying this is the case for all cals but it is certainly pos for others too

 

the pressure signs you say? were they flat primers or case swipes? or both

 

is the load a load you worked out in the cooler days not so long ago and now its warmed right up it maybe giving you some extra pressure?????

 

i have seen chambers where the shoulder junction gets missed out in the cleaning and the carbon hardens decreasing head space a little giving case swipes

 

its late so sorry for any typo's just trying to throw some ideas

[baldie]

The cases are showing pressure marks ?

 

Ejector marks ?

 

The cases are not obturating fully and gripping the chamber walls correctly. This is shown by the dirty necks and soot down the sides.

 

You are therefore getting harder than normal bolt thrust.

[Laurie]

How do you define 'pressure marks'? What kind / strength of rifle are you running?

 

I agree with Baldie. You are running very low pressures depending on the age / strength of your rifle. Let's put it this way, I used to load 140gn Sierra MKs in Lapua brass over 44gn N160 for a 100 year old Carl Gustaf M1896 Swedish service rifle, and considered that load about right in the days before affordable chronographs for this 45,000 psi rifle. However, on some outings - not all and not at all predictable - the damned cases would still soot up.

 

My more recent foray in a modern rifle with the cartridge (a factory Savage 12 6.5-284 F-Class rebarrelled by Osprey Rifles to 6.5X55 with a 30-inch Bartlein F-Class profile tube and with a standard reamer, nothing tight-neck, custom or whatever) saw N160 + 139gn Lapua Scenar loads worked up to 48.3gn for 2,999 fps MV average / ES = 21 in Lapua brass with the CCI-BR2. This actually performed not too badly at half-MOA at 100, but was around a grain above the rifle/cartridge's 'comfort zone' and a bit more still still over prudent / brass life preserving levels. (So, don't copy, please!) Even so, this was not a brass trashing load on a winter's day, but I imagine it might have been in hot summer conditions, and in any event it would have been two, maybe three firings before primer pockets went slack.

 

I eventually adopted a load comprising the 140gn Berger LR BT above 50.4gn N165 that gave very good groups and ~2,850 fps. I've come to the conclusion that counter-intuitively N165 is a far better match to the cartridge for 130-140s despite appearing too slow. It burns cleanly without any of N160's brass-sooting practices too. (Usual load warnings apply - start lower and work up, if copied.)

 

Incidentally, I had the chance to run some factory ammo through this rifle and got:

 

Hornady 140gn PSP: ............. 1.1" average 100 yard groups; 2,487 fps MV average, 126 fps spread, 38.4 fps SD

Lapua 139 Match ................... 0.59" average 100 yd groups; 2,596 fps MV average, 35 fps spread, 13.5 fps SD

 

The Lapua is supposed to achieve 800 m/s (2,625 fps) presumably from a 24-inch barrel, so was running 30 fps down despite six extra inches up front. The issue whenever one talks 6.5X55 SKAN is throat length - they are VERY long-throated unless we're talking custom rifles throated specially for one bullet just off ot into the lands at an ideal seating depth in the neck.

 

I still have this barrel waiting to go back on the action (currently 7-08 Rem now in a Dolphin F-Class metal stock) with a low round count and expect to get my money's worth out of it as it shot very well indeed. If it weren't for the hassle, I'd have it stuck back on specially for The Gun Pimp's 500yd Fly-Shoot 6.5 Challenge on 2nd August as it is one of the best, likely the best 6.5 combination I've had.

[tony]

You think I should up the powder charge a bit more Laurie or just change powders?

[Laurie]

Try increasing charge weights first. Go up in 0.3gn steps and see if you can find something that works better. Assuming you are using a modern rifle, 47gn which is around where you start compressing charges should still be pretty safe with QuickLOAD predicting just over 55,000 psi. This is too much for old service rifles (far, far too much for Krags and higher than a Swedish M1896 should be fed), but is easily handled by Lapua brass in a strong modern sporting rifle.

 

If you get up to / close to 47gn and it's still literally mucking you about, then think of trying something different.

[palo]

I worked up loads in my sako 6.5x55 with the same bullets and n160 and got good accuracy with no pressure signs at 47 grains.

Accuracy was excellent but bullet performance on deer was poor so I stopped using them.

[tony]

Try increasing charge weights first. Go up in 0.3gn steps and see if you can find something that works better. Assuming you are using a modern rifle, 47gn which is around where you start compressing charges should still be pretty safe with QuickLOAD predicting just over 55,000 psi. This is too much for old service rifles (far, far too much for Krags and higher than a Swedish M1896 should be fed), but is easily handled by Lapua brass in a strong modern sporting rifle.

 

If you get up to / close to 47gn and it's still literally mucking you about, then think of trying something different.

Thanks Laurie I will try that, the rifle in question is a Sako75 so hopefully will be ok.

Thanks also to all the above for their input/help, will keep you posted.

Tony.