Accuracy loss - Coppering?/ Primers? / Help!

[Brown Dog]

Rather ****ed off:
First run out with the 300 for many months yesterday. Groups (at 100m) ranged from 1.1 to 2 MOA.

Impressed that I have managed to tune my accuracy with this rifle from 0.5MOA (factory) to 2 MOA with handloads!

Trying to find something to blame:

PART 1:
This rifle's only had around 130 rounds through it; copper colouring on the lands is obvious. After 1 hour's worth of patching with Barnes copper solvent, the patches were still coming out blue. Have I found my accuracy ruining culprit?

I'm going to order in some Forrest bore foam to really dig the rest of the copper out.

I've been virtually exclusively 308 until I bought this 300. Is this rate of coppering normal for 300 win mag?

PART 2:
To compound the error chasing problem, I was testing a new load too(!): 180 Accubond over 78, 78.5, 79 and 79.6 grs N165 with Fed 210 primers. In powder charge order, these shot 1.1, 1.4, 1.8 and 2 MOA.
Would the next sensible thing be to change to Fed 215M primers?
(210s were a deliberate choice because I have read that some people have noticed reduced velocity spread with non mag primers –reckon this is the least of my concerns when I'm shooting into 2 MOA!

)

Any thoughts or advice gratefully received!

 

[Ian M]

Dog,
My .300 WSM seems to copper foul very significantly with Accubonds, just a function of that particular barrel because I do not see it in other rifles. Probably also the higher velocities involved, since most of my Accubond shooting has been with .308 Win.

Strangely the Accubond CT Winchester factory load does not seem to copper foul, can shoot two or three boxes with no accuracy falloff.

I believe what happened to me was I did not recognize the copper fouling buildup and was not addressing it with my cleaning procedure. Now I have a new solvent that seems to get it out faster and more completely, no wash or anything in the bore after a good cleaning.

I believe that most of my magnums copper foul significantly more than my non-magnums, might be the price we pay for higher velocities.

No answer from Winchester re your .300WSM Stealth, will pass on the info when I get it.

I also found that overall length had a lot to do with my WSM accuracy,

 

[Varmint Hunter]

If cleaning the bore throughly doesn't return the accuracy with a proven load I would suspect a possible change in stock/barreled-action fit or tension. Do you have a wood stock?

My Weathery Mark V's (wood stocks) did this periodically. I eventually got rid of every one of them.

A 1" group from a factory rifle is not abnormally large. How often could your rifle fire the .5" group that you mentioned? I've seen factory rifles shoot exceptional groups intermittently and then just seem to loose that accuracy capability. A lot of different things can contribute to this.

For really stubborn copper build-up I have found that alternating between Barnes CR-10 and JB Bore Paste (separately) you can remove even the most difficult copper and carbon build up. Sometimes, either one alone just does not work as well. I am very careful with strong ammonia based cleaners and never exceed the recommended max time to leave that stuff in the bore.

Recently, I experimented with FOUL OUT bore cleaning foam. It seems to clean crud and copper out just like they advertise. It is also supposed to be safe for the bore even if left in for days. Just spray that stuff into the bore and let it sit for an hour, clean it out and respray. Let sit overnight and all the work should be done.

Good luck - VH

 

[BountyHunter]

Try Montana Extreme 50 BMB copper remover. By far the best of anything I have used and I have used all of them.

Order direct from Montana Extreme. www.montanaxtreme.com and POC is either Danny or Linda Huffman. They will take care of you.

Order their plastic bristle brush with it also.

BH

 

[Brown Dog]

All,
Thank you for your replies / ideas. I have just ordered some Forrest bore foam (possibly 'foul out' under a different name this side of the pond?).

I'll let you know if this sorts things out; I rather strongly hope it does -I'm in Scotland in 2 weeks and the thought of carrying the AW (my only alternative rifle)in the hills does not fill me with joy!

Varminthunter: The bedding on the Sauer 202 is unusual in that both the fore-end and butt are removable. The fore-end does not have an overly generous free-float (about 2 sheets of paper)and is my other potential culprit..not sure quite how I'm going to solve it..am applying brainpower in that area.
IanM: Thanks, I'm encouraged that a serious attack on the copper solved your 300 deterioration; I have to put my hand up to being something of a Luddite when it comes to thorough barrel cleaning. I think my 308 experiences have lulled me into a false sense of security...the AW rarely gets more than 2 pull throughs with a bore snake (heresy I know!)but just keeps on performing; ditto for previous rifles. [PS I think the Winchester question was from 'BRIT' -not me]
BountyHunter - Thanks, I'll try the Forrest first since it's available 'on my doorstep'.

 

[Centre Punch]

BROWN DOG:I would suggest you have a rather stout load of N165.If your load duplicates or is approaching factory ballistics you could have extreme pressures which would not neccessaraly show itself in the usual way. In February i worked up a load for my 243 using a 90 grn Lapua Scenar.Loaded with the max charge of H4350, it was superbly accurate. On using the same load on a warm September day, by midday bolt lift was getting heavy and the ejector plunger was not throwing the cases clear. After 5 more rounds accuracy was 3" and the case head facees were scored. Fouling removal took 11hrs of 15min soaks and scrubbing out with shooters choice copper remover. I would suggest a lighter charge of a faster powder, the slower powders being more suitable for the heaviest bullets. With all your fouling removed your accuracy will be restored, but it might be a lot of work.

PS. "****ed off" is an english term, where are you?

Good Hunting.

 

[Mysticplayer]

Brown Dog, My guess is that fouling is NOT your problem. Ammo is.

You know the rifle will shoot 1/2MOA with factory loads so there is little issue with accuracy. However, accuracy goes south with handloads so...

Check the runout of your sized brass and ammo. Try loads from 75gr and work up to 77.5gr. You indicated that the groups opened up the more powder you used. I bet you have exceeded the pressure sweet spot of the barrel.

Change powders (H4831SC,H1000 seems to work well for this case) and possibly primers. Pull a few factory bullets and measure them. compare to the bullets you want to use. How much bigger are the aftermarket bullets?

Try another bullet like the Nosler BT or Hornady SST. Diameter of bullets do vary and may be enough to cause loads to be over pressure although the amount of powder says otherwise. At least, it changes tuning so much that accuracy is poor.

With modern barrels and machining, fouling is not the issue it used to be. I usually find the accuracy problems in the load itself.

Have you chronographed your loads? pressure too low, too high?

Hope this helps...

Jerry

[ 11-29-2004: Message edited by: Jerry Teo ]

 

[Brown Dog]

Jerry and CP,

Thanks for the ideas; I have the feeling that the prob is a bit to do with coppering and a bit with load mis-match to the rifle. I am hoping that decoppering will at least get me back to acceptable accuracy ( I will be happy to get 3/4MOA from this rifle). But I will also try backing off the powder and playing with OAL- I'm loath to do this since I don't want to step down to 30-06 performance from a 300! (I don't think the load is that hot at the moment (he says without having chrono'd!) Viht list their top charge for a 180 as 81 grs of N165(although some of the litigation-minded US publications have the max down at 75grs!(which is Viht's starting load!!)).

I'll let you know what happens

CP- I'm North of Salisbury. You weren't by any chance, on the BDS Advanced Stalkers Course back in March? (I ask because one of the chaps was from Northamptonshire).

 

[Centre Punch]

Brown Dog:

No that was'nt me, i'm not that advanced....yet.