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Double grouping

25 Aug 2015
@ 04:49 pm (GMT)

Arve Ringsbye

I bedded my Wby ultralightweight last weekend as pr the matchgrade bedding instructions. The rifle was bedded front and rear, and app.1 inch forward in front of the receiver, the barrel was fully floated. Action screws torqued to 55.

Tested the rifle with 3 different 4 round loads yesterday, all loads was grouping within 1-1 1/2 inch before bedding at 100 yards. After bedding each load shot to the same poi for the 2 first rounds, the third and fourth round hitting 2 inches high, 1/2 inch left, for all 3 loads.

The bedding looked fine, but very tight. Therefore, and because of maintenace, I greased the rifleaction before reassembling it.

So what to do? I might just follow your instructions on page 104-106 in your book?

Can you help me here Nathan?

Might be a problem with the riflescope, but wouldn't think so because of the same poi as before bedding for the first 2 rounds of each 4 shot group.


25 Aug 2015
@ 09:15 pm (GMT)

Nathan Foster

Re: Double grouping
Hi Arve, hope all is well with you and your viking hordes of the north.

Yes, it may be a case of a pinched fit. It will also pay to check the magazine box over and make sure that it is not pinched either. After assembly, perform the 1 O'Clock test as described in the books.

If the rifle was not free floated before, there is a chance, being an ultra light, that the barrel has a stress issue which was hidden via its original pressure point bedding. I suggest you limit the rifle to three shot groups and do make sure it is allowed to cool between shots. You can test the rifle later for rapid fire - after developing a good load. I am loathe to suggest new pressure point bedding. It can be made to work but the rifle will always string vertically.

The bullets you are using can be a finicky too. The AB is the least finicky to work with and displays the least fouling. When testing, test the AB first, the Scirocco second and the TTSX last. Having said this, I would prefer to see you work with one bullet only during each session.

The ES of your loads is not very good. This makes me wonder about either neck tension and or uniformity of neck temper. You may need just a touch more neck tension if this can be done without effecting concentricity.

Please start out with just the AB and do a full work over, coming up in half grain increments, three shot groups. Try to establish exactly where near max is for this rifle. If you can get N165 at a reasonable price, I would like you to switch to this.

Concentricity is the name of the game when loading for your WBY so either make sure you have the right neck dies for the job and if there is any doubt, purchase a concentricity gauge.

Just remember, a rifle scope can pick up stress too after removal and refitting. To this end, undo the front scope ring screws, then re-tighten them.

Also keep an eye on the rate of fouling, how the rifle is copper fouling etc.

In my mind, I see a potential conundrum where you may need high / near max pressure to effect consistency during the WBY jump for the sake of harmonics and ES. But at the same time, a welter weight barrel, if stressed, will display increased double grouping with such loads.

We really need someone to mass produce a barrel de-resonator. Cast and blasted, then drilled and tapped. Rubber packer, metal outer, .75" thick, clamps on (like scope rings) and deadens vibrations. Non concentric in shape so that it can be turned and essentially dialed to a sweet spot. Mounted just ahead of the forend tip. But alas, most people want to make either gun mufflers or black rifle parts.
27 Aug 2015
@ 09:08 pm (GMT)

Nathan Foster

Re: Double grouping
Well, that's another rifle playing ball. I helped Arve further via email and after a test shoot, he sent me the below photo.

Key factors: Good bedding and good relief where needed. Incremental load work while being sure to change one variable at a time as opposed to (for example) changing seating depths or bullets etc and causing or having to deal with multiple variables.



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