"Dampened" free floating?

[PeterCartwright]

I was reading though old posts when I ran across an idea I find intriguing:  This guy talked about free floating a barrel and then filling the void with "Great Stuff" (it's that aerosal expanding foam used for insulation around windows etc.)  He referred to this process as "dampened free floating".  I assume the purpose is to deaden the normal harmonics of the barrel.

I have a Howa in .338 Winchester as a current project rifle.  It's proving to be something of a problem child so far as accuracy is concerned.  I've restocked in (Boyd's laminate), glass bedded the action and free floated the barrel without seeing much improvement.  My next step may be to try some upward pressure toward the end of the stock/barrel via a shim (credit card material?). 

Anybody tried the "Great Stuff" trick?

[Cknerr]

A little upwards pressure at the far end of the forend tip can settle down a problem child. It only takes 7-8 pounds. Old business cards work well as temporary shims. I start out by seeing how many I can cram under the barrel (usually 1). Then add one more to the stack. Loosen the action screws, stick the cards under the barrel, shoot. You will have to play with the load abit. Then keep adding cards and playing with the load until you find the sweet spot. Now you know how thick to make a collar/bridge/pad. Press on with the mission! Full bedding often helps too. Yes, everyone tries to get free floating....that usually works, especially in the heavier barrels. Light/thin barrels can be a different story. Some times I think it is just to be ornery! In those cases, the opposite works. Case in point, I have 2 custom made 270's, both use Mauser receivers, identical (as much as possible) Douglas barrels, etc. One has a free floating barrel, the other one has both full bedding and the collar I described above. They now shoot the same. The contrary barrel originally shot 4" groups at 100ds.

If you have fluted the barrel, all the above may be useless. I have never tried this on one. Don't use them as a rule.

No guarantees...might help though.

Good luck,
Chris

[gunnut69]

The most stabil and least affected by weather rifle I own is a 300Mag built with a wood stock and bedded full length with not pressure. I suppose it's like having a sybthetic stock with wood wrapped around it..

[PeterCartwright]

Range Report 
I took the problem child to the range today to do some more 'sperimenting.  3 shot groups @100yds. (Nosler 200 gr. BTs with a starting load of RE19).  Here's what I experienced:
3 shots with free floating barrel=3"
3 shots with two business card stock pads inserted under the barrel about a half inch from the end=2.5"
3 shots with three card stock pads=1.25"  (Point of impact also raised a bit more than two inches).

Looks encouraging.  It's certainly the best progress I've made to date.  I'll have to get back to the range to see if this research is repeatable.  I'd be a happy camper with an 1.25" rifle. 

As a side note, the Boyd's laminated stock to which I added a sorbothane (sp?) butt pad turns the .338 into a pussycat.  No pain on the bench.  No technicolor shoulder after range time.  Beats the daylights out of the "tupperware" stock that came with my Howa.

[gunnut69]

You might also check the crown. I've seen a lot of improvement with a nice clean cut crown..

[PeterCartwright]

Hopefully the final post on the "problem child".  I am optimistic that the problem has been solved-although via a circuitous (sp?) route.  First I restocked in a laminated birch Boyd's platform.  Then I glassed the front and back action screws and the chamber area.  Then I added free floating.  Then tried upward pressure toward the end of the forestock.  Finally, I cut a new crown.  None of the above (by themselves) seemed to alter this rifle's maddening tendency toward erratic grouping.  Most groups hovered between 2.5 and 3+ inches (usually closer to the 3" mark).  Finally, I tried one more of your tricks, viz. full length bedding and voila!, the beast SEEMS to have been tamed.  Yesterday I shot two consecutive groups that measured below 1.5".  The 250 gr. Nos.PT grouped in less than 1 1/8".

This is a standard Howa barrel (I guess you'd call it "medium sporter" weight-not at all like the whippy Weatherby Mk. V I own in .270 Wby.).  Frankly, I would never have suspected that it would like full length bedding.  Go figure.  The project has provided me with some valuable education.  Thanks to all for your help.

P.S.  I've got a nice "Loopy" M8 in 4X on the way to finish the project.  (I've been working with an underpowered Burrris in 2.75X).