Anytime you interfere withthe butt of the gun on recoil, it will affect POI. You must be consistent in your hold, trigger squeeze, etc. to be accurate.

There are any number of problems that can cause vertical stringing. Does your loads drop in flush with the chamber when you have the barrel off the frame - if the shoulder (or in your case) the bullet seating causes the case to headspace so there is pressure against the frame when you close it, this can cause stringing. A bad scope or loose scope mounts can cause the same. A loose bolt in the grip can also. Have you chrono'd the loads to see how consistent your velcities are? You may be shooting an inaccurate loading.

Five inches is a lot of stringing, and it may be a combination of factors. I would rest the forend, and either don't rest the base of the grip or rest it on sand bags rather than a hard surface for best accuracy. Also rest your elbows.

Courtney Plater, as much as it offends my fragile ego, I acknowledge that you may be correct in suggesting that I focus on the potential that I am flinching. I've shot pistols for about 15 years and haven't encountered this type of patterning in a long time. I'll work hard to ensure that I'm not flinching by employing a second shooter to reload and occasionally load an already empty case, just to see what I do. As I don't see this problem with other guns, or even other barrels on the same frame (7mm TCU), I would be surprised if the problem is me. However, your point is valid and worth investigating. Thanks for the response.

Rob, thanks for the response. My rounds (158gr. GDHP over H110) are falling right into the chamber and don't seem to be requiring any force to close on them. I slugged one of the rounds, but haven't actually taken measurements off of it yet. However, it looked like the rifling wasn't fully engaged at the front of the cylindrical portion of the projectile. I'm going to recruit some other shooters to see how they do with the gun/round. Perhaps I'm the source of variation. I don't see this type of problem with my 7mm TCU barrel though.

There is one other factor that can really affect vertical POI. I don't know about your case prep, but make sure your case are all the SAME length. Then, when you load, put a good firm crimp into the case. I know, it isn't necessary to keep bullets from walking out from recoil since there is only one in the gun at a time, but it does make more consistant loads.
If you are crimping cases with a slight variation in length (only 4 or 5 thousanths is enough), the amount of crimping will be affected and pressures will vary by enough to make BIG variations in velocity. A good crimp is important in a straight pistol cartridge case to keep the force needed for bullet pull (or push if you prefer) consistant..

Is this a proven load, or are you still working it up? I recently exoperienced (horizontal) stringing with my 45 LC, 1/2 grain change in powder fixed it. But if your load is proven, and you're using the same brand of cases, and preped them for uniformity, sight screws are tight, etc., I agree that it may be your mechanics.
Hangers are alluminum blocks that attach to the barrel to which the forearm is attached. Keeps it from mostly touching the barrel. Virgin valley used to offer hanger bars before they went out of business. You needed to buy the bar and their forearm. Pachmyer offers them also with their hard rubber forearm. They work great on my Contenders.

I missed the original thread, so don't know what the setup is.

I do know that the one case I had of extreme verticle spread, ie ~10" at 50 yds, was with a 10" 357 maximum buring a full charge of H-110. When I changed to AA 1680, my groups tightened right up to a nice tight round group, and this at the same velocity.

As I recall, I tried a variety of rests for the gun, but it was only after I changed powders that the groups settled down. I wouldn't have belied it if I hadn't seen it myself.

I'm having vertical stringing problems with my TC 20" 30-30 carbine. I'm shooting 125 grain hp's. Unique, sr4759, and red dot all string badly - say 3" at 50 yards with 5 shot groups. IMR 4227 does not string too bad. This is a mid range load. I've noticed that ALL my strings start high and string down as the barrel warms up. I'm wondering if it has something to do with the way the forearm is held on with 2 screws. Any clues as to what's happening?

if you want to find out fast...take one of the screws out. Seriously sometimes that works.

duhh, why didn't i think of that?
Thanks for the suggestion

Not sure what you've discovered yet, but here's something that could help:

You can explore the possibility that it is flinching by setting up a video camera at an angle that allows you to see both your eye and trigger finger.

If you really want to find out, mix a "dummy" round in with your regular loads (a dummy round being one with an inert primer and no powder). Any flinching will be immediately obvious.

I'm sure you realize that anything forward of the muzzle may be subject to significant muzzle blast, including the camera's microphone.

Finally, all precision shooting is done with "trigger press", not squeeze or pull (IMHO).

skb2706,
Thanks for the suggestion. I loosened the front screw on my tc 30-30. Groups improved dramatically. Now it's shooting like a tc should. I'm getting bugholes at 50 yards and ~1" at 100 yards with sierra 168 grain bthps from my carbine.

Max - no prob. thats the beauty of online forums. We can get different ideas from all over. In the past verticle stringing on a Contender...at least for me could be attributed to two things always everytime.
Loose scope or mounts.......foreend with two screws on a factory forend. I use hanger bar setups on all mine.

What is a hanger bar? I am wondering if I have to go through life with an empty screw hole on my contender.

Are you shooting from a hard bench with a bipod? If so, try putting a bag under the bipod. It worked for me.

Hanger bars are basically a section of square keystock machined to bridge the two forend screw dovetails on your longer TC barrels. The bar then has a single drilled and tapped hole in it. This is to eliminate the barrel from directly contacting the foreend. It also reduces any stresses between the two screws due to heat build up.....at least this is the premise the system was sold to me on. I like it and all my barrels...even factory are set up this way. It does require a fore end that is either build to accept this bar or modified accordingly.
Just ordered another hanger bar from Steve Stratton (VVCG) for a factory barrel I am working with in .204 Ruger.

Hmmmmm Im think if my contender keeps shooting ok with just one screw tight, then I'll just keep shooting it with one screw tight. Maybe I'll leave the one screw loose and put a bit of non-hardening loctite on it. I'm cheap and lazy.
Is there an advantage for using the hanger bar?