Semi custom M70 fwt 280 em. when zeroed it shot a 5 shot group that was sub half MOA. took it home and cleaned it thoroughly. took it back to the range today and the first shot was 6 inches low and 3 inches left. next two shots were and 2 inches left of center and dead center vertically. next shot was an inch further right adn an inche higher. the next several shots were dead center adn 2 inches high. Right where the original zero was. all I can think of is that the rifle likes to be dirty

6" off from dirty to clean?

I'd be checking on a few other things. That's pretty extreme.

everything was tight and to torqued, like i said shots 5 through 20, even letting the barrel cool for a half hour put bulets 2 inches high and dead center. the fouling is the ony thing i can think of

When you say semi custom, I sure hope that 'aint a custom barrel ...

tno factory barreled action with a custom stock made from a fairly nice piece of French walnut

There's a reason they're called "fouling shots". Some rifles just plain won't shoot with a clean barrel.
Paul B.

I always shoot a couple of fouling shots after cleaning the bore, but the fouling shots are always dead on or very close on all my rifles (all with after market barrels). And they all shoot great with a dirty bore until the bore gets too dirty, which varies with the rifle. It would worry me if fouling shots were far away from normal. I need to be confident on the long shots.

the last 3 shots i shot today landed in a group that mic'd .787 inches at 200 yards. an inch under the X the only thing that makes any sense is that it doesnt like a clean barrel.

I'd be getting a new barrel then. I couldn't handle that.


YMMV.

Been there, done that.
Your barrel is shot out.

I suggest either a new barrel, or if this one used to shoot well, you can have a smith set it back a thread or two and cut a new throat. Regardless, you are near the point where no matter how many fouling shots you fire it won't group.

its a brand new barrel, I dont think its ahd 60 rouneds through it. are you missing the part where it still shot half inch groups after fouling today? or the 3/4 inch group at 200 yards?

original zero being 2 inches high at 100 yds

why? it shoots sub half inch groups. and after four foulers it shot to its normal point of aim.

If you don’t shoot it much, I wouldn’t clean that bastid for the next 10 years. 😀

Ive got one like that John. Mine takes about 3-4 rounds from a clean barrel to come in to where it belongs. Odd part is when you switch loads, it takes a couple round to refill it with whatever is different before it starts grouping again.

Why? Because my barrels both factory and custom shoot +/- less than an inch from where they are suppose to be. Clean or dirty. Doesn't matter. If you're happy with it, that's all that matters. But I couldn't be.

I just ran back down to the range to satisfy a curiosity. mild rain and losing light so I stuck a paper plate up at 200 with an orange thumb tack in the center. didn't have time to set up bags. Shot off of a pack using the oarange tack for an aimp point. 10 round fairly rapid fire. all landed in a 2 inch group about 2-2.5 inches above the orange pin

Tom, you saw the bench target from this 280...I dont think the barrel is shot out

My .22/6mm takes about 12 or so rounds after cleaning to get back to where it shot before cleaning.

Some rifles are just weird.

When I’m working with a new rifle, I make notes in my range book on where the first shot goes if I’ve cleaned it or even if it’s been a while since I shot it last. I note barrel condition, cold, clean or cold, fouled.

I’m currently working up loads in a used 300 Wby which I had treated with DBC when I got it and after a round of 20 shots, I cleaned it and a week later was testing some more loads with a different powder. I got lucky and the first shot of the day was in the group of 0.85”. I’ll check it again later to see if it’s a trend. Of course that’s not how it always works but I’ll find out over time. Then I’ll do what it takes to ensure a good first shot.

That seems really odd. I've never experienced anything that dramatic. What are you cleaning it with?

Yep.. Most factory barrels shoot better when slightly fouled... I've had guys come in sayin' their rifles are thoroughly cleaned, yet shoot like crap.. I've told 'em to stop cleaning the dang thing UNTIL the groups start to open up..

Many have come back in later or called me to say 'you were right'..

All of of mine shoot somewhat differently after cleaning. Not as extreme as the OP's but enough that I sight in before deer or groundhog season and then don't clean until after the season.

Dale

I usually help a couple people with loads and or sighting in if their rifles. After we are done the advice is don’t clean till after season. Some rifles aren’t bad and some change quite a bit when cleaned. Edk

I have 2 rifles that will not lose zero bare metal clean and a cold bore. My .257 WM with a Bartlein barrel and my 6.5 Creedmoor Browning X bolt. Both have McM stocks. This is shooting out to 550 yards. Have a couple of others that I need to really check out.

I've got a Win 70 featherweight in 280 that is the same way. Would not start grouping until 10 rds had already been sent down the tube. So, I scrubbed it all down and applied the Dynatek ultra bore coat, shot till it started grouping again and haven't cleaned it since. It'll put Berger VLD's into under 1/2" groups. I'll probably never clean that barrel again.

does it harm the barrel to leave it fouled for a season? like will rust begin where there is copper and powder fouling since there isn't any oil to protect the bore?
Big Ed

It sounds like the OP has discovered something about his rifle that we all would like to discover about our own, that is, exactly what it takes to make that particular rifle shoot sub 1/2 inch with that particular ammo.

I leave mine dirty throughout the season, but I will pull a dry Boresnake through it several times after a wet day. Its not the powders so much as it is the jacket material filling in the tool marks. Your Gold buddy!

I very seldom clean my high volume rifle barrels unless there's a reason, which is rare unless it's an overbore chambering that's pushed hard. I've got a couple 6.5CMs that I shoot in PRS matches that have had their muzzle brakes cleaned more frequently than their barrels. These rifles have been cleaned every 600-800 rounds. Accuracy returns after the barrels are fouled.

i've also generally stopped scrubbing hunting rifle barrels like I used to. Unless there's a loss in accuracy, I'm putting a rifle up for long term or some other incidental reason, I don't clean the bores. Store riles vertically with bolts open or bolts out and shoot'em dirty.