Groups Went to Hell - Why

[BillGulledge]

Custom 257 on a pre '64 Winchester action - always shot well but only with 1 specific load. I consistently got groups under 3/4 inch with 42 gr D 4350/120 gr Hornaday HP, but very poor groups with any other load/bullet. Last year, even this load would no longer group. I don't think this rifle has had enough use for the barrel to be shot out, but I bought it used so I really don't know.

How do I go about diagnosing the problem and determining if a new barrel is required? If a new barrel is required, what twist and length are recommended?

 

[BoydAllen]

It may be that there has been enough throat wear that your seating depth has become obsolete, perhaps a new load work up is in order. Also, How do you clean? Another thing, consulting my Hornady manual, it would seem that your load is extremely light. In those cases where light loads are used repeatedly in the same cases, I have seen the head to shoulder measurement get shorter, eventually resulting in necks being too long, even though the case is within length spec. Are your fired primers above the case head?

 

[Terry]

Bill

I have cleaned my guns to where the patches came out clean just to learn there was more in the barrel.
I like to use Witches Brew in "clean" barrels. I'm often surprised.

Terry

 

[madmixerman]

Have it borescoped.

 

[Immike]

Bill

I have cleaned my guns to where the patches came out clean just to learn there was more in the barrel.
I like to use Witches Brew in "clean" barrels. I'm often surprised.

Terry

That man is right!!! Witches Brew surprised me too. I'm sold on it.

 

[BoydAllen]

What a lot of fellows don't know is that you can have hard carbon in a barrel and show a white patch. The only reliable way to remove it is careful use of something like IOSSO, or JB. The suggestion to have it bore scoped was excellent. They have become a lot more common, and are the only way to really know what is going on inside a barrel.

 

[jonbearman]

Your case could be trimmed to minimum length allowing carbon to build up in the neck area.I take a similar case and form it with my full length sizer and leave it long,say about .050 of max length.Then I try chambering it and if I feel crunching through the bolt handle then I know I have to remove that carbon to restore accuracy.I use iosso on a tight patch and put the cleaning rod in to approximatly where the neck ends and by hand rotate the rod clock wise and after 10 or so revolutions ,pull it out and check for heavy black carbon on the patch.I repeat this till it is clean.The patch will look grayish if it is clean.The iosso is an abrasive and will pick up minute amounts of barrel steel.It wont hurt anything.

 

[BigDMT]

If you want that Pre-64 Winny to maintain it's monetary value, you'll keep the original barrel on it.

Sounds like a cleaning issue to me too.

 

[Klong]

Put a different scope on it and see what happens! I had the same thing happen to me a few years back. The scope had gone bad,

 

[kelbro]

My bet is on copper build-up. And possibly carbon.

 

[oldhoward]

Hi, I have a 257 Weatherby and had a similar problem. My groups opened up 3 to 5 inches at 100 yards! I have near 1200 rounds shot thru this rifle, many were 75 grain loads used for p.d. hunting. I tried everything, bedding, trigger, loads adjustments, free floating, and restocking, nothing worked. I was ready to re-barrel the rifle. I do clean my rifles religiously, so I thought. Well just by chance I bought some Bore Tech cu+2 copper remover and their carbon out product. I tried the products on the Weatherby and I was surprised, I stopped counting bright blue patches at 60. I was embarrassed to say the least. The rifle now shoots 3/4 inch groups and some groups are 3 shots almost thru the same hole, 5 shots open up a bit.

 

[Larryh128]

Does your pre-64 rifle have the 3rd barrel tensioning screw? If it does, look there for the issue. A lot of those old wins need the barrel channel coated with stock finish so they don't turn with the weather.You can also bed the 3rd screw as well. A friend had a tack driving pre-64 that would consistantly pattern 5-8" groups at 100. After a little stock work, It groups under 1.5 at 300. Makes some of the 700's look ill.

 

[fdshuster]

Bill: Give it a very thorough cleaning, to the point you would swear that it is "clean", then follow madmixerman's advice and have it borescoped. If heavy, coal black streaks are seen, especially in the grooves, and for about 1/3 of the barrel length, closest to the chamber, it's carbon fouling.

Then, follow Boyd's advice & go to work with IOSSO or JB to get the carbon out. It's very difficult to remove, so expect to spend some time with it.

Some claim "WipeOut" will remove carbon, so this would also be a good time for you to try that. I never had any meaningful results with it, but maybe you can get it to work. Re-inspect with a borescope. If the carbon is gone it would also be a good time to check the condition of the throat, looking for the common alligator skin firecracking. If you do find heavy erosion/firecracking, then a new barrel would be the required fix.

"I bought it used, so I really don't know", tells a lot, since you have no idea of the actual rounds fired by the previous owner, so if the problem is not carbon fouling, then it's most likely time for a new barrel.

Many used rifles that I have bought, at fair prices, needed barrel replacement, simply because they were shot out, some sellers admitting that upfront & others claiming they were shot "a couple hundred rounds".

When I buy a used rifle, it's with the assumption the barrel will need replaced & I offer an appropriate price.

 

[CaptainMal]

No clue what 257 cartridge you have that rifle in. I have twin 257 Roberts rifles, one Mauser and one Remington action. Both are "fussy". One only shoots 100 gr. bullets well. The other likes 115's only. Beats me so changes might be in order.

All the comments about copper fouling and carbon issues are VALID. Check there first.