My M38 will only provide accuracy with 129 and heavier bullets, with one exception, that being Nos 120BT. The freebore is enormous, and I suspect that is the biggest obstacle.
I also have a Howa 1500 6.5x55, and it also has a very long throat, so much so that I load to magazine length, or just enough to hold the bullet, whichever is available. The Howa prints a pattern with 90TNT's, marginal with 120gr pills, and is a 1-1/2" gun with 140's, which look rather ridiculous hanging so far out of the case!
Probably have to save the 90's till I get a 260 Rem...

Second Timer:

First off from experience, ditch the use of Varget powder in the 6.5 x 55 with a 100 grain bullet.

Secondly check out your throat length in the Howa. Is it long throated like the Winchester, Ruger rifles or not? If I it long throated and you are seating your bullets like regular rounds accuracy will suck period.

If you are in the market for varmint loads in a 6.5 x 55, any bullet in the 100 grain and under weight will do well. I personally think the 95 grain Hornady V Max is my least favorite tho.

For coyotes and bobcats to preserve hides, the 120 grain Match king give a good showing in my book.

As for powders: RL 15, IMR 4064, R L 7 and IMR 3031 would be my top picks for accuracy and velocity combos. My personal load with that bullet weight ( 100 grain Ballistic Tip or Sierra HP) is 43.5 to 44.4 grains of IMR 4064. The bullet is seated only about an 1/8th to a 1/4 of an inch. The throat in my Ruger and Winchester swallow that with no problem.

It also worked fantastic in my Swedish Mauser.

Varget may be good in other applications, as is H 4895, but in ALL of my 6.5 x 55s, their accuracy is akin to slinging gravel. They group like a 12 gauge at a 100 yds at best.

Cheers and Happy Holidays
seafire