rugger 220 swift crooked chamber

[coyote]

Hi all could anyone tell me why a 220 swift with a crooked chamber[non concentric about .030 thou] would constantly shoot 1/4 " groups all day .
I know rugger has hammer forged barrels on these it's a m77 mk 11 stainless with the beavertail laminate stock .
the gun stoped shooting last summer due to throat erosion I couldn't touch the lands with the bullet no more so I requalified the barrel when I set it up in through the head stock I cut of the old tenon dialed in the bore on both ends [where the new throat will be and the muzzle].
After machining the new tenon and threading I got the reamer out put it in the hole and the back of the reamer was just wobling up and down I thought I didn't dial in the barrel properly,after rechecking my work it was right on the money so I bored the hole concentric and finished chambering.
Thing is I always thought a chamber misaligned like this one would never shoot this gun shot almost as tight as my br's 1/4 " groups with the right load an good bullets most of the time I have rechambered a lot of guns and never seen one this out of wack and be a shooter.
What do you guys think?

 

[tiriaq]

When you indicated the barrel true in your lathe, did you reference on the outside of the barrel, or on the bore? It is not unusual for the bore to be off centre.
With an unchambered barrel, a plug gauge can be inserted in the bore, and the indicator brought into contact with the gauge. If there is already a chamber, the indicator can be inserted into the chamber, if the chamber is coaxially aligned with the bore. When the barrel is dialed in on the bore, the threads and chamber can be cut true to the bore.

 

[coyote]

Tiriaq I wrote in my post I dialed in the bore I always indicate the bore on any barrel and a plug gauge that is what I used on the muzzle end .My question is I know the barrel's chamber was crooked and a lot why was it a good shooter.

 

[tiriaq]

Sorry, missed that.

 

[the wrench]

I had a Ruger m77( not that the brand makes any dif.) that had been re-barreled and the chamber was cut oval. Made reloading almost impossible, but it was a great shooter.Not as good as yours but I could keep all shots inside a 1" circle @ 100 yds. , and this was a 7mm mag.

 

[Oscar Makonka]

My question is I know the barrel's chamber was crooked and a lot why was it a good shooter.

As long as the bullet gets aligned and launches square into the bore and lands it will generally shoot very well. You've struck a node with your probably fullsized brass that fits loose enough in the chamber and the slug far enough into the throat that it is aligning itself. Not good for brass life and if your chamber is out of wack as much as you say you will have to fullsize your brass for it to keep shooting and chambering properly, Likely your brass won't last very many reloadings.

 

[coyote]

WhenI bought the gun I was unsure how many rounds had been fired through it I received about 35 worn out brass that I fired a few times then replaced them with a new batch 100 win brass.
I didn't load to heavy 40.5 gr h380 behind 55gr bullets chronoed about 3750 fps I fired about 1700 rounds and had to FL resize every 4 firings or so the old chamber was a bit looser than the freshly cut one I just did the old brass does not fit I have to FL resize.
My brass lasted about 17 reloads each from what I have documented in my loads book and it still looks pretty good but I will replace them soon I will go to the range on the weekend and see if it shoots any better with the new chamber but I am not holding my breath the barrel seamed to be a little loose ahead of the old throat for a few inches now at least the bullet easily reaches the lands so it should help.

 

[Leeper]

Not having seen the thing, it's hard to say for sure but I suspect the barrel wasa a bit crooked at the breech so that the breech end of the chamber was eccentric but the throat portion well aligned. With a curved bore, as you move ahead, some portion has to run out. If you dial in the throat area (or as close as you can reach) the breech end will run out. Dial in the breech end and the throat will run out. The reamer will probably follow the bore well enough so the throat would be reasonably concentric in either case.
Anyway, if the original throat was concentric, accuracy could be quite good even with some misalignment at the rear end. At one time, Ruger claimed the 220 Swift was their most accurate chambering. I know I've seen some shoot some small groups. Not 1/4" all day long but at least now and then. Regards, Bill.

 

[coyote]

Bill I think you are right about the crooked barrel I seen a video of a guy on you tube dialing in a barrel through the headstock like I do now I used to run them through a steady rest .
This guy dials the barrel in about 2 inches in from the breech with the 4 jaw and then dials it in just on the eddge maybe 1/4 " in with the cat head [spider] on the other end of the head stock until he gets the first few inches of the barrel runing perfectly concentric ,the muzzle end of the barrel is not dialed in but the part that is chambered run true.
So if the barrel has a crookedness to it the chamber and throat are well aligned to the bore.I only seen this last night so I fear the way I rechambered my possibly crooked barrel may not have helped but I will see I may go to the range tonight.
has anyone here ever chambered a barrel using this method I think it makes a lot of sense if there is any warp to the bore.
I think I am going to try one I have here a bevin king It's been on the shelf here for a few years .

 

[Leeper]

I prefer to dial the bore and the future location of the throat then bore the start of the chamber to ensure alignment and concentricity.
It used to be common practice to thread between centers then chamber in the steady rest. This is still a perfectly viable way to do things providing the bore is reasonably straight. Another technique consisted of chambering in the 4-jaw chuck as you described (chamber portion running true) then threading between centers. Setting up with the breech end running true and allowing the muzzle to end up where it may then chambering and threading in that position is just fine; as long as you don't mind that the barrel points off to the side or bottom or whatever. Chambering this way then threading between centers will yield a barrel which points the right way but in which the chamber may not be perpendicular to the bolt face.
I have seen well regarded 'smiths who simply trued the shank of the barrel on center then held the barrel in a three jaw chuck to thread and chamber. Certainly not what I would call an ideal technique but, if the three jaw is a good one, it can work not bad. They were happy enough with the results and, apparently, so were their customers.
One problem with chambering in the headstock is that many tailstocks sit high when the lathe is cold. This can potentially produce an oversized chamber if the reamer is supported on a center. Using a "floppy" holder like Guntech uses takes care of this by allowing the reamer to center on the work once the chamber is started. Otherwise, chambering in the steady compensates for misalignment as might be found in an old, worn, lathe.
Tailstocks are generally set up a bit high ( about .003" on a 13" swing lathe) to compensate for the change in the machine axis as the headstock warms up. So, if you want to verify tailstock alignment, do so after turning and thread so the headstock is warm. After the tailstock is worn from sliding back and forth for a few years, you may have to shim it up to re-align it. Regards, Bill.