Why do different bullets shoot so differently?

[D.Hayden]

What is it that makes different bullets shoot so differently in different rifles?

Is there anything to look at: Why one bullet/load might shoot so well in one rifle, the next it's crap?

There's a group of us.. that have pretty much have the same uppers.. JP 18" Mid-weight, 1/8 twist

The exact same cheap Winchester 55s shoot fine in 2, shoot like crap in 2.

Luckily.. in mine they shoot sub MOA.. no problem.. at 100 yards.. in the worst ones.. 4" group at 100 is best they can do. My barrel seems to shoot everything well, that the others shoot well.

There's no pattern to how old the barrel is.. (the oldest and newest are the worse).

Thanks... Dave

[uscbigdawg]

Dave,

I know the feeling. My 18" 1:8 Oly barrel shoots .25 MOA w/ 69's and .5 w/ 55's with only a .5-.75 POI shift. My 20" 1:9 JP barrel, while it has about 40-50k on it never really shot anything great. While still sub MOA, it never had one load that stood out over another.

Rich

[SA Friday]

BerKim, if you could consistantly answer this question you would make millions. There are just too many variables to the process. It would be almost as good as a brass magnet.

[Guy Neill]

There are simply too many variables to allow defining a specific reason guns differ in particular ways.

Having aid that, the muzzle is a very critical point. It may be worthwhile to re-crown those rifles not shooting well to see if it will help.

Guy

[Chris Conley]

I have an idea. When they make the barrel, a boaring bit and rod is pushed thru the barrel with a hydraulic ram. When the bit comes thru the other side it very hot. I'm not sure how many barrels they get out of one bit but you would think that the first few are maybe a few 10,000ths or so out of perfect spec. Then as they do more the bit wears and brings it right to spec. Once the bit starts to wear out then your back to that few 10,000ths out of perfect spec. The ones in the middle are the good ones and the first and last ones are the ones that don't shoot so well. Luck of the draw. I've watched a barrel being made (takes 35 seconds) at a factory and I had these questions. To any company, as long as it's in quality spec it's good. When it gets out of spec then they change the bit and start good barrels and bad all over again. Just the nature of mass production.

Chris C.

Edited June 28, 2008 by Chris Conley

[cking]

First off use some quality ammo like Federal/black hills for testing.Before you start clean the snot out of barrels with Jb bore paste and make sure you get the carbon ring right in front of the chamber.

Now how can they be so different, Jp probably buys blanks from somebody like douglas. The blanks can vary bore diameter, the best bores taper slightly to the muzzle. You can test this by driving a lead plug through bore to find the loose and tight spots.

Next is cutting the chamber, did they really get it aligned to bore, read the procedure Complass lake's Frank White goes through to get this part done right, no automation here.

What chamber cutter did they use. Lots of different cutters for .223. Long lead, short, how tight is neck. Depends on bullet weight you want to use.

Then crowning, but that really is the easy part.

Then break in.

So many places to screwup, thats why no two barrels are alike.

[wsimpso1]

BerKim,

I gotta wonder if your buddies are shooting the same batch of 55's. Some shoot great, some don't. Now for why each barrel has its preferences, geez, none of us knows for sure, but every barrel is an individual... And this coming from a guy who worked for Remington as a product engineer.

Billski

[havotec1]

+1 for checking for nick in the crown, even the slightest imperfection will kill.

[TMC]

This is still a mystery. We have eliminated the ammo but shooting Berkims ammo in our guns but no luck there. One of our group has lowered the powder charge slowing them down and that has closed the group for his rifle. I've loaded a few to try but haven't shot them yet.