I just put in a Timney Trigger in my Browning Hells Canyon 6.5 Creedmoor. Shooting factory Hornady 143gr ELD X's.

So, I am happy with the groups (5 shot) but wondering what causes vertical stringing. Could it be my shooting technique at the bench?

If this is a change from previous, I'd greatly suspect bedding and/or screw torque issues.

Yes, it did not do this prior to me taking the gun apart. I don't remember what the torque WAS, but it is now 45" lbs in the front and 40 in the rear.

I was shooting a Weatherby Ultra Lightweight 30-06 a few weeks ago and had many groups, with various loads, that looked a lot like yours. I found when I used a softer front rest and held onto the forearm of the rifle or applied some pressure with my left hand on top of the scope the vertical grouping lessened somewhat. This light rifle with this much recoil bounces up fairly harshly and and evidently not consistently when allowed to free recoil.

Now I really got consistent groups when I put the pressure point back in the forearm and held onto the thing. This is the second Weatherby Ultra Lightweight that has shot much better with the pressure point.

I did not hold the forearm at all and used a mechanical front rest with a pretty hard bag. It is a Caldwell Rock BR Competition front rest and rabbit ear rear bag.

Make sure nothing is making contact now. IE, the new trigger may be bulkier and is giving a false torque on the screws as it binds the action to stock fitment. Mag box/bottom metal properly seated and etc. Google around and see what others are using for torque settings, etc...it is likely in the stock-to-action interface that is the issue.

Hard front bags can cause vertical stringing. I was always taught soft front bag, hard rear bag. Rock BR isn’t a bad rest as I used one for years before upgrading to a Bald Eagle.

This is common when the load is not quite correct for your rifle, this is why you roll your own and do load development

For those that use a "soft" front bag, what do you recommend?

I use either ground corncob or air soft BB’s. Both work well.

Never heard this before, always found the opposite to be true.
You won’t find corncob or air soft BB’s ever at a BR match, pretty much 100% sand in a front bag

You won’t find skinny barrels and forends either.

Just to clarify, the rifle is a Hells Canyon long range and came with a McM Game Scout stock. The barrel is what I would consider a magnum sporter type contour.

I went and counted, I have 8 different rests for all kinds of different shooting. every one is filled with sand. never found a soft front rest to ever be a good idea.
Like I was saying earlier the most common cause of vertical is your load being off just a little, a little more or less powder normally cures it. can also be caused by a tail wind or your swivel stud contacting your rest under recoil

Think if you go search the archives of BR Central you will find where it’s been discussed a few times that hard front rests will induce vertical stringing. Also I have never tore a bag apart to see what they used, but since this isn’t a match who really gives a sh*t what it’s filled with.
Since I also have multiple rests and bags for use in certain situations, I have found that for hunting rifles with rounded forends that a soft bag on front filled with corncob works just dandy, I also have one that is loose filled sand which is a little harder but after fluffing the bag it also works just Jim spiffy for its intended use of shooting hunting rifles. Also have a couple of bags that are match legal for shooting flat Varmint or BR stocks. For sh*ts and giggles,

IBS rules

Rest. A front rest sand bag shall support the front part of a rifle: a rear rest sand bag shall support the rear part of a rifle; neither rest may be attached to the bench, the rifle, or to the other.
They must be movable in all directions independently of the other. Any part of the rifle resting
thereon must maintain one half inch distance from any part of the rest holding the sandbag on
which the rifle rests. Wherever the rifle makes contact on its sides there may a maximum one
half inch in height and a minimum of one half inch thick on each side. This does not apply to any
devise holding the sand bags in place or any fore-end stop. Sand bags on front rests must be a
minimum of one and one half inches wide from the direction of the muzzle to the butt stock and
rear rest sand bags must be a minimum of one and one half inches wide by three inches long.
Multi-piece front bag systems are acceptable as long as they meet all other criteria listed in this
definition. Only “Heavy Guns” are allowed rear rests that utilize mechanical adjustments. Rifles will be removable from their front rests without lifting any part of the front rest from its contact
points with the bench it is occupying.
Sandbag. A sand bag is defined as a bag with or without a pedestal, with a leather, cloth or synthetic cover that is capable of being easily flexed by the fingers. They may contain a dry finely divided nonmetallic substance such as, but not limited to, “Heavy Sand”, sand, gravel or grain, without additive and packed loosely enough that bag can be easily deformed by pressure of the fingers.
The cover of the sand bags must not be bound in such a manner to prohibit free movement of the contents. Lubricants on the sand bag may be used. Front and rear rest sandbags must be such that when lifting the rifle from the rests, the rests does not lose any contact from the bench it is occupying. Vertical spacers under a rear bag are allowed as long as they do not contain any protrusions which can be inserted into the bench top or a sandbag.

NBRSA is a little different,

The front sandbag. The front shall be a bag, without additions, containing sand only, and at least 1⁄2” thick over its entire surface. The portion which contacts the rifle shall contact the entire surface under the fore end. Tape on the sandbag is legal.

Agreed x2

as a bench rest shooter many of us buy the special heavier type bench rest sand,we pack all our rest bags very tight and even use some water when we fill and tamp bags ,so when its dry its very hard , firm and solid. some of us even use a deodorant that has the white powder so both hard bags slide the rifle forearm and stock back easy as it recoils. i want my bald eagle rests extremely hard always,soft bags can open your groups up.

http://benchrest.com/archive/index.php/t-84040.html

Tony Boyer points out in his book that hard front bags opens group.

Greg Walley
08-28-2012, 09:30 AM
Technically, no. At least in the NBRSA. Rules state that the bag must be able to be deflected 1/4" by finger pressure. Of course, that is very vague, and I've never seen a M.D. enforce this rule. But you don't want a rock hard bag anyway. Was it TB who said that the bag should feel like a ripe orange? That is a good description to go by.

We’ve fixed a lot of bad guns-barrels-scopes-actions over the years by simply removing a bit of sand from both sandbags.

Greg Walley
Kelbly’s Inc.

Butch Lambert
08-27-2012, 09:44 PM
Terry, if the bag is filled with sand, it is legal. Tony B. is right, a hard front bag can contribute to vertical.

Hard front rests definitely affect accuracy in lighter-weight hunting rifles.

Any possibility that the front swivel stud is close to the rest?

No, I make it a point to verify that.

I agree that the bag being "hard" can affect groups.

What so many are glossing over is that he said it wasn't stringing shots before changing the trigger. If in fact nothing else has changed, form, load, rest, whatever, then it points to something with the rifle itself. It could be a piece of foreign material in the bedding, interference from the new trigger to the stock (as someone else mentioned), the stock taking some moisture and "swelling" if it's wood, etc. Start with what may have changed when the problem started. Is the recoil lug bedded tight? If so look for "shavings" or foreign material in it's pocket.

I think its more the individual person that affects group size, not the sandbag. A lot of guys grasping at straws here and pulling chit out of their azz.

That.

I followed your advise of placing a piece of soft material (I use a towel) a long time ago and the vertical stringing I was experienncing disappeared.

The proof is in the pudding.

Alvaro

Yes, you surely are.

WOW Swifty you sure know how to rant, only problem is you always seem to leave out any common sense.
You mention Tony Boyer, He runs his bags very hard. when he feels it is too hard he might take out a teaspoon's worth of sand but it is still pretty hard.
one thing is for sure is the rear bag is softer than the front (opposite of what you suggest). Looking at Tony's book right now............not even a mention of the airsoft BB's you also suggest.
Hardness in sand bags is relative not absolute. I mentioned that I have 8 different rests for different applications, my rest for Benchrest is by far the hardest and the one that I use for Big game rifles with slender stocks I still consider hard but is more supple. there is an appropriate hardness for each application and sand of some sort most of the time is the best solution. Never IMO airsoft BB's.
The only analogy I can think of is you are saying Rectal is better than Vaginal........you can sell that until the end of time and I'll still never believe you.

Yeah, I know I read that from you JB. This is a heavy outfit with a 26" barrel and bedded McM Game Scout stock with a Nightforce scope.

If I change receiver screw torque, should I tighten the front or back? Currently I have it at 45" lbs in the front and 40 in the rear.

1) I have had this happen a few times when the barrel was touching the stock. As the barrel heats up, it pushes further up from the stock and the point of impact climbs with each shot.

Slide a dollar bill between the stock and the barrel, and make sure it goes all the way to the receiver. Where they touch the stock can be relieved for a barrel clearance fit.

2) If the new trigger interfered with the stock in the rear, it could pry the barrel down in the front, down into touching forestock.

Put carbon black on the trigger and assemble the rifle. See if black shows up on the stock. Relieve the stock so the new trigger fits.

Heat will cause it to rise.Another thing you might try is back off 1/2 grain and see what happens.

Oh, one more thing (Lieutenant Colombo interpretation here) that I did not mention thinking it did not matter , I had a pretty breezy head wind while shooting. Maybe 5 to 8 mph?

Would that matter?

I don't think a 3 mph difference in a head wind will cause that big of movement at 100 yards. I am assuming 100 yards as I don't think you stated. If it is properly bedded I also don't think that screw torque is the likely cause. Take it apart and check everything for any binding or foreign material in between the metal and the stock. If nothing is in there Clarkm is probably on the right track. The new trigger is touching somewhere. I am guessing the trigger assembly is held in with cross pins like on a Rem 700. Is one of the pins sticking out on one side further than it was and now digging into the stock?

Also, is one group all that this happened to? If so, it may be all for nothing, can't base much off of just one group.