Like many factory rifles, some Sakos are (were) made with a "bump" near the forward end of the barrel channel to place some positive pressure on the barrel. I've been working with a .300 Win L61R than had no up pressure bump and it was scattering shots in the 2 inch range, which is not up to standards for a Sako.

Before taking more drastic measures, I placed about four thicknesses of plastic electrical tape in the bottom of the barrel channel about 2-3 inches back from the forend tip. This immediately shrunk groups to less than one-inch, with no vertical dispersion. "If some is good, more must be better" the thinking goes, so I added two more thicknesses. The additional up pressure caused marked vertical dispersion of about two inches, but no horizontal dispersion. So I took one thickness out, and ended up with a one-inch group centered exactly where I wanted it with about equal vertical and horizontal dispersion.

Now for the question: Will the electrical tape work on a long term basis? If not, what should you use for the up pressure material (bedding compound?) and how does one "tune" the pressure like I did by adding and removing layers of tape?

I know, I know, many of you will write that NOTHING is acceptable other than a fully floated barrel. Don't bother. That's a somewhat crude methodology that often fails with sporter weight barrels and besides, done right it requires fully glassing (and preferably pillar bedding) the action which is an operation I don't want to tackle if it can be avoided. I'm happy with one-inch groups from a .300 magnum; I just want them to last.

This isn't what you want to hear, but get rid of the pressure points in the forend of the stock (free float) and you will likely have a sub MOA rifle. Each of my three Sakos responded this way. They were all 1"+ rifles from the factory, remove the pressure, glass bed the lug and they are 1/2" rifles. Each later got McMillan Stocks, which did not add of detract from the accuracy in the factory stock once the pressure was removed and lugs bedded.

Stonecreek, to determine the amount of weight there is on the barrel, place (clamp) the rifle in a rest and wrap a strap of some type that doesn't stretch around the barrel. Using a trigger pull guage type device attached to the strap, lift the barrel until you can slip a piece of paper between the barrel and the tape. Record the amount of weight it took to separate the two. Pour an epoxy bed, and using the weights as a guide, start trimming the excess. Believe it or not, some folks prefer to suspend the gun up side down so they can methodically hang precision trigger weights to move the barrel. For better results, torque the guard screws and record the setting so that you can repeat the set up.

Thanks, guys, I appreciate the advise.

AZ Pete: I'm glad you've had good luck with your barrel floating, but I don't want to go through that process right now. One thing that holds me back is the crossbolt in the Sako that bears against the action lug. It appears difficult to get a meaningful glass bedding since the relationship between the crossbolt and the lug can't change.

Malm: Thanks for the details on using bedding compound for the up-pressure bump. What is your experience? Do sporter barrels usually do better with the forend bearing in this manner, or with a full-floating barrel? And do you think that the electrical tape trick would be stable so long as the action is not removed from the stock?

I have not used tape, and my bedded barrels were done by others so can't give advice there. This is just a general comment on electrical tape in the long run. I think that it will over time 1. compress and 2. deteriorate, so it will not be consistent in the long run. I think that the bedding compound is a good idea. make a slight notch in the barrel channel at the same spot as your tape, put the compound in, get it close to size (using the weights method if you can) and then take your scraper with you to the range and scrape it in to the perfect spot.

A friend told me about a method of putting it in the vise upside down and putting weight on it, but I can't remember the procedure or where I have it written down at. I am going to find it when I finally get around to stocking a big bore and full length bedding it.

Red

quote:

Originally posted by Stonecreek:
Malm: Thanks for the details on using bedding compound for the up-pressure bump. What is your experience? Do sporter barrels usually do better with the forend bearing in this manner, or with a full-floating barrel? And do you think that the electrical tape trick would be stable so long as the action is not removed from the stock?

The quest for ultimate accuracy starts with consistency and uniformity. Forearm contact with the barrel is no exception. Unless there is uniform contact and pressure on the barrel, then I tend to float everything first. Free floating the barrel removes ALL forend influence and provides a good, neutral starting point should pressure be needed later. From my experience, about 90 percent of rifles shoot better free floated. If, after carefully working various loads and such, the groups still refuse to come together, then addind an epoxy pressure bed will provide more uniform results because you will be starting from scratch so-to-speak. If that makes sense.

I'm not an electrician, but from a gunsmithing point of view, I don't believe electrical tape is very durable for long term use. In the cold it tends to stiffen up, and as it begins to heat up, it softens. I would rate it somewhere behind business cards.

quote:

Originally posted by Stonecreek:
Thanks, guys, I appreciate the advise.

AZ Pete: I'm glad you've had good luck with your barrel floating, but I don't want to go through that process right now. One thing that holds me back is the crossbolt in the Sako that bears against the action lug. It appears difficult to get a meaningful glass bedding since the relationship between the crossbolt and the lug can't change.

Two of the three Sako's that I floated and bedded had cross bolts. They don't present a problem. If you feel that you have good recoil lug contact with the cross bolt now, then just float the barrel and see what improvement you get. Bedding may not be needed. I cannot say that the bedding was a factor in my improved accuracy, I just did it when I floated the barrels, as a matter of routine.

the poor rifle will be getting stressed, your pulling the action down by screwing it in the stock and forcing the barrel up with a built up area in the barrels channel. surely that is pulling things out of alignment and the heavy recoil is probably stressing things more.

quote:

Originally posted by Paul from nz:
the poor rifle will be getting stressed, your pulling the action down by screwing it in the stock and forcing the barrel up with a built up area in the barrels channel. surely that is pulling things out of alignment and the heavy recoil is probably stressing things more.

On the other hand, maybe it is pulling it "into" alignment.

I wouldn't be happy with tape. Here's how I would do it.

If you measure the torque on the action screws you could replicate the tension on the barrel by putting a bed of glass before and/or after the tape, retorquing and allowing to set. As these are only temporary you wouldn't prepare the wood and could use release agent on the wood as well as the barrel.

Remove the tape and prepare a proper bed where the tape was, retorque the screws and leave to set. When set you can remove the two temporary beds which should have mirrored the tension put on the barrel....

Then the only thing you have to worry about is the stability of the forearm either from humidity or different holds. I doubt either are likely to be a big issue?

quote:

Originally posted by 1894mk2:
Then the only thing you have to worry about is the stability of the forearm either from humidity or different holds. I doubt either are likely to be a big issue?

And, the direction and the amount the barrel is going to move when it starts to heat up.

quote:

Originally posted by AZ Pete:
This isn't what you want to hear, but get rid of the pressure points in the forend of the stock (free float) and you will likely have a sub MOA rifle.

I dunno, I have a heavy barreled Remington 700 that shoots better with forend pressure than free-floated. Couldn't believe my eyes.