New Ruger .17hmr keyholing

Key holing is caused by undersized bullets, oversized barrels and sometimes excessively low velocity. Using the word 'random' suggests an ammo quality thing. Rimfire ammo can just be like that. Changing ammo is the way to go.
However, according to Midway's site, your biggest problem fixing this is the relatively crappy availability of different brands of .17 HMR ammo(stuff's as expensive as .22 Magnum ammo too). Your options are the Federal(Using a 17 grain V-Max), the CCI(also with the same bullet), a Hornady with a 17 grain V-Max and a 16 grain Speer TNT HP bullet from CCI(one grain isn't going to change much). Everything else is either not available at all or 'mixed' availability(Federal V-Shok using the same 17 grain V-Max anyway.).
Graf's is showing Winchester in stock, but it's still with a 17 grain V-Max.
 
If the bullets weren't for sure key holing, I'd suggest you consider that the scope might be the problem. My problem a year or so ago, where I got: good group, not so good group, ok group, crazy bad group, then ok group, was the scope.
 
I measured the diameter of the bullet in the federal stuff...

Just above the case mouth, it measured exactly .17, not sure if those are supposed to be exact like that or not.
 
Every now and then a lemon gets out the door and it's time to throw in the towel and call CS--that's the point I finally reached with my Henry.

My $199 marlin .17 hmr (say what you will about marlins--this is one fantastic rifle package IMHO) groups pretty much any ammo at MOA or better--I wouldn't waste any more time getting more frustrated/aggravated if I were you.
 
.17 caliber bores are prone to extreme copper fouling, which can greatly impact performance. While I wouldn't necessarily expect it with .17 HMR, it's still possible.


Use a good copper remover, and retest.


I shiny bore means nothing, since copper, lead, and brass fouling can be just as shiny as the base material -- and it's not like you have a very good viewing angle with a .17 caliber bore, anyway.
 
Yeah, I was wondering if 17 cal has fouling sensitivity and/or tendency to foul quickly.

Would 60-70 rounds be enough to cause the problem?
 
I pull a snake thru the bore on my Savage 93R every 40-50 rounds to maintain that dime-sized 100yd accuracy. Never had my groups open up as bad as you described though.
 
IMO: Get rid of the cable for cleaning your gun and use a bore guide w/ a Dewey enamaled rod w/ effective chemicals. I like Montana Xtreme but there are others that are good as well. Accuracy can suffer at the throat and crown from anything that dings them. Push your rod thru the barrel, unscrew the jag, slowly push the end of the rod thru the crown by hand, then pull the rod out wiping as you go. Just my opinion as a basic cleaning place to start. Use aluminum jag for anything that has copper remover in it.
 
This is not right. A 17 grain .17 bullet (short) should shoot great.

As mentioned take a good look at the crown - probably the most overlooked accuracy destroyers. Another one might be a defective excessively rough bore. Still another - defective ammo with extremely thin copper jackets. .17's are notorious bore foulers and even with relatively low vel. rim-fire .17 HRM fouling can build up quickly.

I use a nice Dewey nylon coated rod for all my rifles with a 30 minute soak in Gunslick foam then brushing with a nylon brush. I never drag the brush back into the bore past the nice sharp crown. Continually wipe off the cleaning rod. I also use 5W-30 synthetic motor oil to attack carbon.

After cleaning it and checking out the crown measure the twist with a cleaning rod, ruler, tape, and felt tip pen. Don't know what the specs are but your measurements should be real close. I think it would be almost impossible for the twist to not be spec.

To avoid censure, I too clean the carp (ugly-undesirable-rough fish) out of my rifles.
 
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