Loose bore = Less Velocity?

[MagnumManiac]

JB works best if used with a calibre specific jag…tight.
A brush doesn't have enough force to lay the roughness over.

Cheers.

 

[Shane Lindsey]

I used a 338 bronze brush. It was tight. Seemed to help with accuracy. I have never thought I needed a borescope as I clean often. Ensure I hit the throat and use JB every so often when feeling froggy...now I am re-thinking. Maybe lots of build-up due to fireforming with brass that isn't long enough???

 

[Gregg C]

I feel your frustration. I had built a 33xc. Had super high hopes. All for naught... Using 3 different powders, 2 different primers, couldn't get what I believed I should have been getting velocity wise.
30in K and P barrel. Horrible copper fouling. 15 shots equaled several hours of hard *** work to get it clean. If I didn't, pressure would raise its ugly head. The 338-378 Weatherby would push those same 250 Bergers along at 150fps faster using less powder thru a 31in Lilja. The 33 shot well, but it was ****ing me off to spend money on components for unsatisfactory performance. After 500rds thru it, I quit shooting it, and ordered a 34" Lilja.
I learned a lot, tho....

 

[slikmrc]

I had a fairly new FWT 25-06 barrel on a rifle I bought acting the same as what you were seeing. Barrel looked like the lapping process was missed, very prominent boring marks in the barrel. Tried JB and Iosso with little change, barrel was coppered up in 5 rounds and pressured up way below book max. I ran a full 50 round course of the Tubbs lapping bullets thru it and the rifle really came around. It still coppers up a bit after 30-40 rounds but is getting good speeds for a 22" barrel. The only reason I tried the lapping bullets is the cold bore and next two shoots out of it would stay at 1/2 moa. A sample of one, but the Tubbs bullets kept this barrel from heading to the garden for some staking duty.

 

[Lefty7mmstw]

On a 30-06 based wildcatted 338 you won't quite see 338 Win ballistics. Heck, I can't even get 338 Win from my 35 Whelen and she should push better with the extra diameter. I get to 2900 fps from a 225 Hornady or 2750 fps from a 250 Sierra in my 338. Anything within 200 fps would be about all I expect. I do have a 26" bbl. on my #1 in 338Win.

 

[Radman]

If you look closely between pic no.1 and pic no.2, you can see I have already lightly lapped that barrel, I will use JB on it every time I clean it for about a dozen times. I can't complain, it was a customer return warranty and I got it for less than half price, a Win Model 70 EW Portuguese made rifle. It had crooked scope mount holes, so I drilled them to 8-40 and later found the rough bore, it shoots sub MoA with 225g Accubonds.

Cheers.

 

[Radman]

Interesting. I too have found scope base mounting holes misaligned on several rifles down through the years.

 

[MagnumManiac]

On a 30-06 based wildcatted 338 you won't quite see 338 Win ballistics. Heck, I can't even get 338 Win from my 35 Whelen and she should push better with the extra diameter. I get to 2900 fps from a 225 Hornady or 2750 fps from a 250 Sierra in my 338. Anything within 200 fps would be about all I expect. I do have a 26" bbl. on my #1 in 338Win.

I have both 338-06 and 338WM, my fastest barrel will easily push a 225g to 2980fps, the slowest to 2890fps in the 338WM, the 06 will get 2680fps tops with a 225g. 250's top out at 2775fps in WM and 2550fps in the 06, all with 26" barrels. So, about 200fps difference across the board.

Cheers.