A friend of mine is developing a new load for his 6.5x55mm Tikka. He has changed everything except the primers!This includes switching from neck sizing to full length sizing, and increasing the OAL of the loaded round. His barrel and chamber have also had a clean with Butches Bore cleaner ect. It turned out his barrel was in very serious need of a clean. Anyway, after puting everything back together (we had the action out of the stock as well)the first problem was that he had a wondering MPI...shooting 3 rnd groups with some known good "old" ammo the groups moved from 6 O'Clock, through 9 up to 1 O'Clock. Prior to this he had fired about 20 shots so the barrel should have fouled a little. Anyway after removing and refitting the stock paying attenion to tightening the front action screw first, it now seems to have settled down. Could over or incorrectly tightening the action screws cause wandering MPI??? Now to his "new" loads. These are 140grn bullets in Lapua (sp?) brass with 47grns of Vit N160. The brass is absolutely covered in black almost greasy soot which smells "funny"..this black stuff is almost like powder which has not burned properly. The primer is also showing very slight signs of flattening. Is this black stuff due to high pressure?? His old loads just showed "normal" fouling on the cases.

Any ideas???

Pete

Your black sooty case necks sound like a combination of low chamber pressure and work hardened necks on your cases. On a new case that is properly annealed the neck and shoulder area is quite soft. When a cartridge with normal chamber pressure is fired the neck and shoulder area being the softest and thinest part of the case expand first to form a gas seal with the barrel.If the case neck is too hard it does not expand to form the gas seal as quickly and some of the gas leaks back causing blackening of the case neck. Very low chamber pressures contribute to this as well.A severe case of this can actually collapse the case in the shoulder area.Solution Check the powder charge is not below the recommended starting charge for that particular bullet and or anneal the cases.

Snowman,
It is the brand new cases which are showing the problem and after firing the cases are showing "slight" signs of the primer starting to flatten. The bolt is not in anyway sticky and lifts OK. Also the powder charge is near the top of the recommended range for this bullet weight/powder.
We have also checked the powder scales with check weights and they are ok....

Pete

[This message has been edited by Pete E (edited 05-21-2001).]

You may have a combination of a number of things. Whatever the problem, I agree with Snowman that you are getting pressure and powder past the case. I believe your statement, "This includes switching from neck sizing to full length sizing, " may be the answer to the problem. I'll bet the shoulders are being set back way too far and causing an excessive headspace condition. This would account for the flattening of the primers. With the shoulders of the cases being set back too far the brass doesn't have the opportunity to expand enough to seal the gases forward of the shoulder. After the primer strike the case will tend to go forward. The gases will slightly pop out the primer which is then flattened as the pressure builds while the projectile starts down the barrel. Try neck sizing again with no other changes and I'll bet the problem goes away.

And, yes, poorly set actions in the stock will cause your PI's to wander. Bob

Bob338 and Snowman have given you good advice. A little remark, FWIW - you say that it is new cases that are giving you the problem. You might just have a batch of cases with the shoulder too far back. I would try full-length sizing one or 2 fired cases, and neck-sizing another 1 or 2 new cases. One of 2 things should happen - a) Your problem vanishes, which would indicate the validity of my 'theory', or b) Your full-length sized cases still show the same symptoms, but the neck-sized cases don't. This would indicate the need to back your sizing die off until it just touches the shoulder, but doesn't set it back significantly. You can use one of the neck-sized fired cases and some engineer's blue to get the setting right.

Rikkie

Thanks guys,

I suspect that the problem is related to the
resizing. I know when he first had the problem, he full length resized some of the
once fired "new" brass and the problem
persisted, but I'm not sure on his very first
firings whether they were resized or not.
To give you some more background, he had taken his rifle and dies to a local gunsmith
who stripped and cleaned the rifle and also
advised him is dies were incorrectly set...the sizer die apparenty was not "over camming" properly. The seating die was also altered and I think his cartridge OAL is also
too long. I think this may be compounding the
resizing problem. I think the next stage is to go back to neck sizing as suggested and
also reset the bullet seating depth to what it was previously. if this cures the problem
he can the carefully adjust the resizing die to full length resize as required.

Thanks again for the help,

Pete

Others will shoot me for this but I have I have had exactly the same soot problems with 6.5x55 LAPUA cases at charge weights which really should not have been underpressured. (47gr N160 with 140gr bullet is likely to be hot - speer max is 45.5gr which itself is over SAAMI pressure levels)

I did not like the experience of a case in my rifle behaving in this way (to wit you're being told it's under pressure or over pressure in this thread alone) and went back to remington cases which in my rife are only sooty at start loads.

So try some remington cases - I'd be confident that your problem vanishes whether full length sized or neck sized. I'd also be confident that your friends rifle will start experiencing extraction problems if he neck sizes LAPUA brass.

A quick up date....my mate took the rifle back to the range this evening along with some of the fired cases. He also took some once fired, full length sized & primed cases for the 'smith to see. The 'smith loaded a couple of these with a different powder (RL19) and tried them and no sooty deposits.
My mate has bought some of this powder and will try a few more rounds after his holiday.
So it looks as if it may have been a bad canister of powder (vit N160) & perhaps Snowman was right after all! The powder was only 3 months old and stored in back room away from damp, heat ect. I guess we'll know more after he does more tests!

Thanks for the help,

Pete

[This message has been edited by Pete E (edited 05-22-2001).]

Just had a quck call from my friend...after returning home last night with the new powder, he loaded a couple of roads only to get the same problem results!! The *only* variable different we can see is that he is using his own bullet seating dia where as the smith used one of his own on site. So back to head scratching time!

Before leaving for his holiday, my mate
tried reloading some old Norma brass and he is getting the same problem with that. It does not really make sense??? Have to wait
another week now before he tries anything else. He has ordered a new redding die set,
so maybe this will change things...

One question only:

Is he trying to reach the lands?

-- Mats

Problem Solved!

My mate altered the bulletseating depth and reduced the COL by 1.5mm or so, and the sooting has dissappeared, the grouping is sub 1" again and the signs of pressure are gone. I've no idea why such a drastic change was needed as the barrel and chamber were only cleaned.

Pete

I ought to wait for the experts to comment on this turnaround but I couldn't resist asking my novice's questions...

Was he crimping or not?

What was COL before and at what distance was he touching lands? (I'm assuming he wasn't actually loading to touch lands?)

COL now being shorter must mean that bullet seating depth has increased by the same 1.5mm; so was it that the bullet was seated too short before and thereby not proprely holding the pressure at combustion?

------------------

The usual cure for sooty cases is go to a faster burning powder...That works 99% of the time....

------------------
Ray Atkinson

ray@atkinsonhunting.com
atkinsonhunting.com

Sorry I did not get back earlier, but we've been away stalking.
Ray,
The powder was not to blame, as it performed ok before the problem and it performed OK again after the problem was solved.

Peter,
I can't give you the figures off hand, but I know he was not crimping.His originally load was designed to be just off the lands. Anyway, after thinking this through over a beer or two, the best we can come up with is that the chamber was so full of crude that his old load was actually headspacing on it. With that crude removed the cartridge case was able to move forward a touch so now the bullet was tight onto the rifling causing high pressures. By seating the bullet in a little, the high pressure was solved. After the cleaning but while he was developing a new load but with the old long COL, he was getting signs of pressure at say 45.5 grains where as now 47 grains is not showing any pressure signs at all. This was solved litterly the night before we went stalking so we will be looking into it a little deeper now we have the time; at the moment, he is just glad to get his rifle shooting again!

Pete

[This message has been edited by Pete E (edited 06-04-2001).]