Barrel run out, and indexing..

S

skeetlee

Active member
I have been talking with a couple good fellas that hang out around here about barrel indexing, and the effects run out can play while shooting. This is an area i havent expored deep enough into yet, and i feel like i need to.
I chambered 2 barrels yesterday. One barrel had only .007 run out and the other had .035. I cant help but wonder if to much run out, such as the barrel with .035 will cause exsessive gun movement while shooting or under recoil? The second part of all this, is were is it best to clock a barrel with this much run out? This topic has been disscussed with me with two different trains of thought. 12 or 6 is the question? I think the high spot should be at 6. Maybe your experience is different?
So can there be to much run out? Where do you clock your run out? lee
 
If you are going to shoot at Phoenix I would chamber it at 9:00 for the predominant left to right wind in the morning. You could be lost in the afternoon. ;)
 
I read a PS magazine article that tested an indexed a .22 RF barrel, and the tightest groups were with the impact point at the 6 O'clock position. I have a theory that that orientation allowed the bullet traveling down the barrel to approximate the drop from gravity curve, in effect producing the least side force on the rifle as it went down the barrel, like a zero gravity effect used to train astronauts in a plane flying downward. This would give the lest vibration when firing. Has anybody tried this in a centerfire barrel?? Putting a laser bore sighter in the muzzle, and rotating the barrel in v-blocks would give a good indication of the right orientation, assuming the runout down the barrel is not too extreme. Much faster bullet speed, less of a curve needed for zero gravity down the tube, ya know...
 
Another option is to find the runout, index it to wherever (I'll suggest around 6 O-Clock) and then re-index to "centers" which puts the muzzle back in front of the chamber. There are several builders here who feel that having the muzzle in front of the chamber is important.

REMEMBER if you do this to pivot on the throat!!!

I don't like this method, I'm not promoting it, just noting it.

al
 
my worthless 2 cents

My experiance with the 12 or 6 indexing has been a wash on what is more accurate. I have done both ways on 10-12 barrels that I paid very close attention to and they have shot very well and I have not seen enough differance to suggest one over the other. For me it is a either way situation. However on the long range guns I do like the muzzle up for obvious reasons in scope adjustment. I believe I read a post by Mr. Beggs (hope my memory is correct) that said he is a muzzle down guy because he found more accuracy this way. With that said you can probably discount my either way belief since he has been doing this longer and knows what the heck he is talking about. So now that I have confused the discussion more and have in no way helped you decide what to do I believe my job here is done. Thank you and have fun with your search for fame and glory with one hole 5 shot groups.
Brandon Johnson
 
alinwa said:
Another option is to find the runout, index it to wherever (I'll suggest around 6 O-Clock) and then re-index to "centers" which puts the muzzle back in front of the chamber. There are several builders here who feel that having the muzzle in front of the chamber is important.

REMEMBER if you do this to pivot on the throat!!!

I don't like this method, I'm not promoting it, just noting it.

al
Click to expand...

Wait......what???
 
I do not post very much, but I build mostly longrange rifles and have had good luck putting the muzzle in front of the throat.
I tried both ways and if I got my high spot index wrong point of impact would move that direction futher out. Nothing scientific just the way It works for me.

Steve
 
While Gene Beggs' threaded bushing system ran into problems with full pressure PPC loads (Hard extraction set in a lower than "normal" pressure due to thinner chamber walls.) I don't believe that there was a problem with cartridges that had .222 sized case heads, and since there are several of these that are known performers, at least at 100 yards, if someone wanted he could try a barrel clocked to any point of rotation that he wanted (without doing anything but removing the barrel, slightly repositioning the bushing, and holding it in position while reinstalling the barrel), there would be nothing to stop him. Personally, I greatly admire his ingenuity in coming up with this. Hopefully, some day one of the shooters that has a higher hobby expenditure limit will have BAT make him an action with an enlarged front receiver ring, so that barrels that have normal tenon dimension can be evaluated to find their most advantageous clocking. No....I'm not holding my breath for that one.
 
No need to hold your breath

Boyd Allen said:
... have BAT make him an action with an enlarged front receiver ring, so that barrels that have normal tenon dimension can be evaluated to find their most advantageous clocking.
Click to expand...

Boyd,
I shot such an action this past summer. A 1.53" diameter 3L action with a 1.25-16 thread and a bushing down to 1.062-18. These sizes keep adequate mechanical strength through the barrel tenon, bushing and receiver ring. No case stretch issues in 30BR. Trouble is, the gun shot well enough as first assembled that I haven't bothered to test indexing. If I can find some time, I still want to do this.

Cheers,
Keith
 
Neat! I look forward to hearing about your results. I had spoken with Gene about this option, but was not aware that anyone had done it.
 
I would like to thank Jackie Stogsdill for doing the smithing. It took some head-scratching and figuring to get it to work, and it turned out real nice.
 
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