What causes vertical stringing??

[Goat]

I finally got to shoot my unfired 1980 M-375 today and was disappointed with the results. I tried 220gr Hornadys with high expectations since so many have reported good results with them. Horizontally groups were good to great but like the 200gr Sierra and 250gr LFN GC Beartooth they had severe vertical stringing. Since I was shooting good with other rifles I don't think it is my bench technique. One buddy that I talked to said his bench rest buddies say that vertical stringing is asking for more powder. Since the load is two grains below max and shows no signs of being hot I will ease up to max and see what happens. Could the problem be related to the forearm? This rifle is in the "Sporting Carbine" configuration so there are no barrel bands to contend with. Maybe the forearm is putting unnecessary pressure on the barrel. I will try more loads in the next few days.
Goat

[Hobie]

To what other rifles are you comparing? Off sand bags? More info is needed.

More powder might, but so might less or simply moving the receiver directly on to the bag (if used) rather than resting on the forearm...

[TedH]

My Marlin 375 was bad about that also when I got it. On mine the firing pin was gummed up pretty bad. So much so that I would even have occasional misfires. A good cleaning of the bolt and firing pin solved that for the most part. I also found some benefit from a good firm crimp with a Lee FCD. Those two things pretty much eliminated my vertical stringing.

Are you shooting 36.0 gr. of RL7 with that Hornady 220? That seems to be the accuracy benchmark for most every 375 Win. rifle I've ever seen or heard about. If it won't shoot good with that load, look at the rifle itself, or your technique.

[2X22]

but so might less or simply moving the receiver directly on to the bag (if used) rather than resting on the forearm...

Yep. I was out shooting my 444 yesterday and my 1st two groups were strung vertically. I moved my sandbags so the end of the forend was resting on the bag rather than in the center of the forend and the groups magically went into nice rounded groups.

2x22

[Goat]

I was also shooting another Marlin and an 1885 High Wall today. I usually rest the very back edge of the forearm on the front rest and the rear is in a "rabbit earred" sandbag. I did fire one group with the front rest under the reciever and it made no difference. I was using a good bench, good rest and bags and had no problems with the other rifles. I am about to go load some more. Thanks for the suggestion Hobie about moving to the recever if you need more info let me know. Yep, Ted 36gr of RL-7 withthe 220 Hornady with a FC die.
Goat

[BigSky56]

If you have a rifle that wont group remove the forearm and mag tube and shoot it, if it groups start working on where its binding. In the articles section of this site is a treatise on a tuning up a lever for accuracy. danny

[Technical Director]

And if the manner the shooter has shouldered and gripped the rifle is not consistant, one would realize a changing whipping motion with each shot. Another possiblity may be due to the action having come loose in the stock which would also result in a whipping motion of the gun when fired.

[1886]

Hi, Your bag/bench technique and or barrel time. Stay as consistent as possible on the bench then try different powder charges and possibly primers. Only change one variable at a time so as to accurately isolate each variable. God Bless, 1886.

[Sixgun]

Loosen up any screws that are attached anywhere forward of the receiver about 1 full turn. if that don't work, remove everything forward of the receiver. If that don't work, you have problems with your load.---------Sixgun