[SlamFire1]

It is almost gospel within the shooting community that tight chambers, and tight case necks mean better accuracy.
However after owing this Ruger M77, I am wondering if this is doctrine is false.
http://img.photobucket.com/albums/v479/SlamFire/Ruger%20M77%20Glassbedded/96ReducedRugerM77afterGlassbeddingD.jpg

This 308 rifle, after it was bedded, shoots exceptionally well. I am very happy with it. And yet, when the cases come out of the chamber, the necks are swelled up to a greater diameter than any match rifle I own. Maybe even some of the service rifles I own.


I am getting to believe that the most important accuracy issues for a barrel are a concentric chamber, good crown job, and a good tube. I don’t think tight chambers are all that important for outstanding accuracy.


http://img.photobucket.com/albums/v479/SlamFire/Targets/168Nosler390Pats4895.jpg

[krs]

As long as you're happy...http://i130.photobucket.com/albums/p263/twagger/guns/055group.jpg

[JDGray]

Nice groups Guys!!

And krs........YOU SUCK!!:neener:

[krs]

:D Take this!...http://i130.photobucket.com/albums/p263/twagger/guns/today10mphgusts.jpg

[LongRifles, Inc.]

"Tight" is a relative term.

A cartridge must have enough room for the neck to expand so that it can release the bullet. Run it too tight and pressures go through the roof and this is never good. (very unsafe)

Second. When a guy says "tight neck" its not that the neck was tightened up to increase accuracy. The necks are turned on the brass so that the wall thickness is consistent around the circumference. The tighter neck is to bring the cartridge neck/chamber neck dimension back into the proper relationship.

is it the end all answer to accuracy? Absolutely not. Many rifles shoot fine with out of the box ammunition. But when a person does spend top dollar on all components and machine work a tighter neck does typically help shrink group size.

Hope this helped.

[SlamFire1]

Boy, did I get the title wrong. I was thinking of rifle barrel chamber necks. I used to see reamers sold stating "cuts a tight chamber neck".

I have never trimmed cartridge case necks. My ammo shoots within the accuracy requirements of the game I shoot: NRA Highpower.

[krs]

SlamFire,

You're not wrong, really. When you've seen the sort of thing you described above with phrases like "cuts a tight chamber neck" it's meaningless without knowing the dimensions involved.

I have a reamer that I had made for my 6ppc barrels. I twiddled slightly with the shoulder angle and specified that I wanted the neck to be .262" in order to cut a minimum from my cartridge necks when I turned them to .261" for a "tight neck fit in the chamber".

I have another reamer for my .222 barrels that I decided I was getting sick of turning necks and ordered the reamer to make the neck .245" knowing that my cases were almost always 244" out of the box.

Both reamers would give me a .001" fit of neck to chamber but with the .222 I was giving away the added refinement of turned necks, which would assure that the neck wall thickness was uniform and the necks were all concentric both to the case centerline and that of the chamber.

I'd gotten the same 'tight neck chambers' in both but my .222 would be less the precision setup.

Turned out that that 'less precise' chamber fired the best single group I ever made - the one you see above through the paster - .055" center-to-center for 5 shots at 100 yards off rests.

[Bart B.]

The smallest 10+ shot groups I know of from 30 caliber rifles at medium and long range have all been done with full-length sized cases fired in standard SAAMI dimension chambers. Chamber necks were about .344- to .345-inch and loaded round neck diameter was anywhere from .334- to .338-inch. That's a few thousandths clearance all the way around the case neck.

Note that it's the rimless bottle neck case shoulder slamming into the chamber shoulder and centering there from firing pin strikes that positions the case neck in the chamber neck and the bullet in the barrel's throat. If the case neck's not straight with the shoulder, it'll be off center in the chamber neck as well as the barrel throat.