Why do we get fanatical over barrel alignment?

[gunsandgunsmithing]

I think our job chambering barrels is to do all we can do to give it every chance to be all it can be. That said, I bought a takeoff bbl several years ago now, that was intended to just be a fireforming bbl. So, I chucked it into a 3 jaw and never indicated anything. It won a lot of matches! Lol! Go figure!

 

[INTJ]

Ordered one. I was actually looking for one this morning. The mity isn't cutting it on longer chambers.

I just got one and have used it on a couple of barrels. I tried it on the Mitituyo .0001 test indicator and it doesn't work well. It turns the .0001" graduations into .001". However, on the Interapid it makes the .0005" marks into .001" marks and it's easy to see when you have zero movement.

I think the progress a lot of us make is we start with the Gordy rods because hey are easy to understand, add the Interapid when we start understanding about tolerance stacking, the go completely to the Interapid when we get comfortable with it.

 

[LVLAaron]

The mity with a 1.5 inch indicator turns each hash mark into 3 tenths. That's workable, you can pretty easily read between the lines. But you put a longer tip on it, and you might as well use a wet noodle.

 

[Dusty Stevens]

Tolerance stacking. Control everything you can

 

[Bamban]

I go for .015 under shoulder diameter then step bore in enough to get the reamer started. I use the dead center for supporting the reamer tell its cutting good and have never had a problem with chatter doing it that way so far. I do check my tail stock for alignment often also.

How far from the chuck do you align the tailstock?

 

[jkohler]

How far from the chuck do you align the tailstock?

I have test bars that are 20 and 12 inch that I check with.

 

[jackieschmidt]

So why does throat and bore alignment matter significantly more than loaded round to throat alignment? Both things seem to be directly related to getting the bullet heading down the barrel and spinning about its axis correctly

About 10 years ago, quite a few Short Range Benchrest shooters got on the “loaded round straightening” kick. Several manufactures marketed little fixtures that allowed you to check the loaded round for runout and straighten if necessary.

I bought one from Bruno, which he copied from someone else.

In the loading area, you could see shooters (sometimes frantically) attempting to get their rounds perfect before being called back to the line.

The trend, (or fad), kinda ran it’s course. I really think it dawned on most of us that it just did’t make much difference. Trust the dies to do their work.

It did me.

My theory is since most of us get pretty aggressive with the full length sizing, and give the loaded round about .002 clearance in the neck, the entire thing kinda self aligns as everything expands with the initial pressure.

At the very least, if you take care in the chambering process, you can be confident that the first thing the bullet encounters is truly aligned.

 

[Sniperhandle]

Ordered one. I was actually looking for one this morning. The mity isn't cutting it on longer chambers.

So the indicator you ordered is only good for .001 When we are usually using indicators that are good for .0001 Because of the length of the dial indicator rod, Now you have reduced the amount you can dial in to? I don't do it this way you guys are talking about, I use rods, So I'm trying to figure this out?

 

[jackieschmidt]

So the indicator you ordered is only good for .001 When we are usually using indicators that are good for .0001 Because of the length of the rod, Now you have reduced the amount you can dial in to? I don't do it this way you guys are taliking about, I use rods, So I'm trying to figure this out?

If you are using the Gordy range rod method, it might surprise you that if you indicate to run true in a 6 inch length, it might run out .001+ at other points.

regaeless of how you set up a barrel, always remember tha when something is nor truly straight, all you can hope to do is get two points running dead true. Anything in between or on either side will exhibit runout. The only way to establish a truly straight third point is to single point bore, then ream so it will be dead true with the muzzle and the throat.

This is the way I do chambers. I indicate the muzzle ID, the area where the throat will be, then drill out the stock, single point bore on the same taper as the case, then hand ream for the final dimensions and finish.

As a note, I do not polish chambers. I have found that the finish the reamer leaves is a perfect trade off between ease of extraction and allowing the the case walls grip the chamber so as to not increase exccesive bolt thrust.

 

[INTJ]

So the indicator you ordered is only good for .001 When we are usually using indicators that are good for .0001 Because of the length of the dial indicator rod, Now you have reduced the amount you can dial in to? I don't do it this way you guys are talking about, I use rods, So I'm trying to figure this out?

The Interapid has marks every .0005". When using the 2.75" (or is it 2.675"?) stylus it comes with the each mark shows 0005" of movement. However, the Interapid is of such high quality, and the marks are spaced far enough part, that it's easy to see when you have zero movement.

If you use the 5.5" stylus then the sensitivity is cut in half. Still, the indicator is so good and the marks are spaced enough so you can still see zero movement.

Direct reading off the lands and grooves is the most precise way to dial in--period. All the other methods can (and do) induce error. The question then becomes does that error matter?

With the Gordy "Grizzly" rods, you have clearance between the pilot one the bore as well as clearance between the rod and the pilot. If we assume .0002" of clearance, we could easily have .0004" of runout when we think we have none. Again, the question is will that matter?

With range rods, they have to be in perfect alignment and even then we aren't measuring the throat but the breech.

I use the Interapid. When I get a barrel dialed in I want it perfectly concentric with the spindle bore at the throat. I find that generally, I can get that 2-3" (ish) straight. The muzzle routinely rounds out .015 - .030" when the barrel is dialed this way.

I am still not convinced on prebore. Those little boring bars can deflect, and I think it would be easy to wind up with less support that using the reamer all the way. But I haven't fully sorted that part out.

 

[LVLAaron]

So the indicator you ordered is only good for .001 When we are usually using indicators that are good for .0001 Because of the length of the dial indicator rod, Now you have reduced the amount you can dial in to? I don't do it this way you guys are talking about, I use rods, So I'm trying to figure this out?

On a long cartridge I can't dial past the throat without a rod... Maye the rod works better... maybe "reading between the lines" on the indicator is better. I'll figure it out. Just because each line is 1 thou, doens't mean you can't use it to read closer than that.

I never indicate the muzzle end when doing the chamber. Some barrels that might be out 40 thou... That'd definitely give you a crooked throat.

 

[LVLAaron]

The Interapid has marks every .0005". When using the 2.75" (or is it 2.675"?) stylus it comes with the each mark shows 0005" of movement. However, the Interapid is of such high quality, and the marks are spaced far enough part, that it's easy to see when you have zero movement.

If you use the 5.5" stylus then the sensitivity is cut in half. Still, the indicator is so good and the marks are spaced enough so you can still see zero movement.

Direct reading off the lands and grooves is the most precise way to dial in--period. All the other methods can (and do) induce error. The question then becomes does that error matter?

With the Gordy "Grizzly" rods, you have clearance between the pilot one the bore as well as clearance between the rod and the pilot. If we assume .0002" of clearance, we could easily have .0004" of runout when we think we have none. Again, the question is will that matter?

With range rods, they have to be in perfect alignment and even then we aren't measuring the throat but the breech.

I use the Interapid. When I get a barrel dialed in I want it perfectly concentric with the spindle bore at the throat. I find that generally, I can get that 2-3" (ish) straight. The muzzle routinely rounds out .015 - .030" when the barrel is dialed this way.

I am still not convinced on prebore. Those little boring bars can deflect, and I think it would be easy to wind up with less support that using the reamer all the way. But I haven't fully sorted that part out.

You can take the slack out of the grizzly rod. Then the only slack you have is whatever oil you have between your surfaces.

Pre-bore is the way to go. Even if your tool has some deflection... so what. The hole size doesn't matter, as long as it's perpendicular to your throat.

 

[Sniperhandle]

If you are using the Gordy range rod method, it might surprise you that if you indicate to run true in a 6 inch length, it might run out .001+ at other points.

regaeless of how you set up a barrel, always remember tha when something is nor truly straight, all you can hope to do is get two points running dead true. Anything in between or on either side will exhibit runout. The only way to establish a truly straight third point is to single point bore, then ream so it will be dead true with the muzzle and the throat.

This is the way I do chambers. I indicate the muzzle ID, the area where the throat will be, then drill out the stock, single point bore on the same taper as the case, then hand ream for the final dimensions and finish.

As a note, I do not polish chambers. I have found that the finish the reamer leaves is a perfect trade off between ease of extraction and allowing the the case walls grip the chamber so as to not increase exccesive bolt thrust.

Ok when you dial in the muzzle, Are you dialing in off of the bore or are you using a rod?

 

[Sniperhandle]

You know, we used to dial in the chamber end and the muzzle end, Then we went to dialing in the chamber end only, There are so many different opinions about this even just in this thread? At least we aren't still chambering from a steady rest.

 

[gunsandgunsmithing]

Ok when you dial in the muzzle, Are you dialing in off of the bore or are you using a rod?

A rod only reads off of the lands and the lands and grooves are virtually never exactly the same. A reamer pilot does the same, registers off of the lands. If the two are not perfectly concentric to one another, pick one because you can't have both. Most people claim the grooves matter most but I'm not sure how they quantify that statement. Now, we have to MAKE the reamer follow the grooves, which is not natural. The reamer wants to follow the pilot and/or the first surface being cut. Most of this is just reading material and winter time activity, when we aren't shooting. Bottom line is, was and will be...don't pull the trigger at the WRONG time.

 

[Sniperhandle]

A rod only reads off of the lands and the lands and grooves are virtually never exactly the same. A reamer pilot does the same, registers off of the lands. If the two are not perfectly concentric to one another, pick one because you can't have both. Most people claim the grooves matter most but I'm not sure how they quantify that statement. Now, we have to MAKE the reamer follow the grooves, which is not natural. The reamer wants to follow the pilot and/or the first surface being cut. Most of this is just reading material and winter time activity, when we aren't shooting. Bottom line is, was and will be...don't pull the trigger at the WRONG time.

So we are trying to line up everything perfectly so the bullet can travel down grooves and lands that are almost never perfect?

I'm getting small groups now, I have won some local long range matches, I think I am just going to keep on doing what I have been doing, I appreciate all of the input from everybody though, This stuff can be really interesting for sure!

 

[LVLAaron]

A rod only reads off of the lands and the lands and grooves are virtually never exactly the same. A reamer pilot does the same, registers off of the lands. If the two are not perfectly concentric to one another, pick one because you can't have both. Most people claim the grooves matter most but I'm not sure how they quantify that statement. Now, we have to MAKE the reamer follow the grooves, which is not natural. The reamer wants to follow the pilot and/or the first surface being cut. Most of this is just reading material and winter time activity, when we aren't shooting. Bottom line is, was and will be...don't pull the trigger at the WRONG time.

Easy fix to your problem statement. Dial the throat and an inch in front of it (on the bore). Get that running true - drill and pre-bore a little bit. Ream. Now your pilot isn't doing anything except going along for the ride.

 

[gunsandgunsmithing]

So we are trying to line up everything perfectly so the bullet can travel down grooves and lands that are almost never perfect?

I'm getting small groups now, I have won some local long range matches, I think I am just going to keep on doing what I have been doing, I appreciate all of the input from everybody though, This stuff can be really interesting for sure!

Exactly right and exactly what most shooters SHOULD worry about. Anyone that doesn't understand that even a high end lathe has more runout from the FACTORY than what most internet posters EXPECT, should really focus on things that matter the most to their results. Let the smiths split those other hairs. I have trouble when smiths or anyone else starts splitting tenths, when they are self taught with a basement lathe. Sorry, but true.

 

[gunsandgunsmithing]

Easy fix to your problem statement. Dial the throat and an inch in front of it (on the bore). Get that running true - drill and pre-bore a little bit. Ream. Now your pilot isn't doing anything except going along for the ride.

I didn't mention my method but I agree with you, mostly. Still, you can't possibly have two surfaces that are NOT concentric to one another to run true to one another, by any method.

 

[LVLAaron]

I didn't mention my method but I agree with you, mostly. Still, you can't possibly have two surfaces that are NOT concentric to one another to run true to one another, by any method.

Sure. It's about minimizing the things we don't want. If there's a better way to get a concentric throat, I'd like to know about it.