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Throat Reaming Guide

What are the possibilities that could be true?

A) I got lucky and this barrel is better than any other I got over the last 10 years and the tight throat chamber makes no difference.
B) The barrel is about the same as other barrels I got over the last 10 years and the tight throat chamber is the reason it shoots better than others.
C) The barrel is better than most and the tight throat chamber makes the most of it.

Again, my interest is in the context of long heavy VLD bullets, and in my case using 223 or 308 for F Class FTR. Meaning I have limited case capacity that requires a long throat to get performance with heavy projectiles.

Time will tell. Light winds expected on Saturday, 30 rounds on the bench ready for testing.
Just curious. How much over nominal bullet diameter are your FB's? How tight is tight?
 
You are all entitled to your opinions.

I have my own and will continue to test using the tightest safe freebore diameters I can get away will and prove the point to myself.

Sometimes people do well despite the weaknesses they have and not because of them.

Jack Nicklaus was once a superstar but he could not have been competitive against a swing like Tiger Woods.
Your assuming i didnt test this? I used to run tight freebores like everyone else. I have been trying to figure out the magic in reamers a long time. Sometimes you get a specail one. I used to think it was in lead angle, but i tested that enough to know that wasnt it. Its the diameter. But your spot on, you should test it for yourself.
 
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I'm not assuming. I'm recognizing that different bullet weights/length seated to different free bore lengths react differently. I would not dare to make a claim that one condition applies ideally to all variations.

My focus is ideal accuracy with heavy VLDs, seated long.
 
I'm not assuming. I'm recognizing that different bullet weights/length seated to different free bore lengths react differently. I would not dare to make a claim that one condition applies ideally to all variations.

My focus is ideal accuracy with heavy VLDs, seated long.
My curiosity is the same as Dave Tooley's.

How does your freebore diameter compare to bullet diameter?
 
I'm a bit confused, happens alot. you talking freebore diameter as opposed to freebore length right? Getting ready to order a Reamer from JGS is why I'm asking.
 
I'm a bit confused, happens alot. you talking freebore diameter as opposed to freebore length right? Getting ready to order a Reamer from JGS is why I'm asking.
Well both really...

A dedicated throating reamer allows you to control your free bore length, but the finer points of how exactly the free bore is machined will result in minor to significant dimensional variances in free bore diameter.

The reason I came up with the throating guide bushing is in an effort to reduce those axial variances that can result in an over size free bore diameter. It also allows just about anyone to perform this critical task at home with excellent results.
 
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My curiosity is the same as Dave Tooley's.

How does your freebore diameter compare to bullet diameter?
In this last 223 Rem barrel, the throating reamer measures 0.2243. The finished throat measures 0.2246 to maybe as large as 0.2247, but I'm feeling more like 0.2246". Hard to tell more precisely than that. A reamer cannot cut undersize. The only question is how much oversize it will cut.

The 0.224 bullets I measured are as large as 0.2244 at the largest point.

Barrels I measured have had free bore diameters well over 0.225 and they generally shot inside1/2 MOA at 100 yards with the 223 and 88 grain EDLMs seated to an OAL of around 2.670".

This effort is an attempt to get well inside 1/4 MOA consistently and hopefully closer to 1/8 MOA with the 88-90 grain projectiles.

To be clear, my body reamer only takes out about half the rifling for the first 0.100". This is to avoid getting any sort of step in the free bore once reamed.
 
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Most of the Uni Throaters are .4375" same as a reamer. Make a tapered bushing to fit the ID of the action with a center ID of .438". This bushing needs to be secured in the bolt race by scope base screw(s) and protrude beyond the action tang. The back side needs to be faced true. You can insert the Uni Throater through a Micromerter Adjustable Reamer Stop (MARSII), then slide on the bushing, and attach the throating reamer. With the propper Pilot bushing on the throating reamer and a lubricated reamer it can be hand bottomed out. Slide the MARS II down against the bolt race bushing. Tighten town the set screws on the MARS II. Then dial back the MARS II the desired depth and cut the rifling. Can't be done easier or more accurately.
 
Most of the Uni Throaters are .4375" same as a reamer. Make a tapered bushing to fit the ID of the action with a center ID of .438". This bushing needs to be secured in the bolt race by scope base screw(s) and protrude beyond the action tang. The back side needs to be faced true. You can insert the Uni Throater through a Micromerter Adjustable Reamer Stop (MARSII), then slide on the bushing, and attach the throating reamer. With the propper Pilot bushing on the throating reamer and a lubricated reamer it can be hand bottomed out. Slide the MARS II down against the bolt race bushing. Tighten town the set screws on the MARS II. Then dial back the MARS II the desired depth and cut the rifling. Can't be done easier or more accurately.
Thanks nat. Couldnt be easier than that
 
Trend is to shoot very tight Freebores. I got into trouble with this years ago with "fat" bullets and even fatter pressure rings, Carbon, not to mention that reamer makers having +/- .0005 on the grind.

I don't care what kind of pixy dust is sprinkled over a chamber with .0003 over bullet dia freebore, I will NEVER go there again, for many reasons!
 
You are all entitled to your opinions.

I have my own and will continue to test using the tightest safe freebore diameters I can get away will and prove the point to myself.

Sometimes people do well despite the weaknesses they have and not because of them.

Jack Nicklaus was once a superstar but he could not have been competitive against a swing like Tiger Woods.

Young fat Jack had a better swing than Tiger ever had. He used to crush the face of his driver in a matter of a few weeks and had to be rotated through. He won the PGA championship long drive in 1965 with a drive of 350 yards with a 42 inch wood driver and a rubber ball (a distance that was barely matched a few years ago when they reinstated the PGA championship long drive.) He beat much better players in an era of superstars, and had a much longer career even dominating into the senior tour.

I think that people make decisions in their heads about things that have little or nothing to do with reality
 
I'll tell you this. I'd rather have a chamber with the CORRECT LENGTH freebore for the bullet far away from the donut. That always shoots better IMHO. I use a ptg throater and it works flawlessly. It has a bushing and a guide with a stop all built in. No need to reinvent the wheel.
 
Young fat Jack had a better swing than Tiger ever had. He used to crush the face of his driver in a matter of a few weeks and had to be rotated through. He won the PGA championship long drive in 1965 with a drive of 350 yards with a 42 inch wood driver and a rubber ball (a distance that was barely matched a few years ago when they reinstated the PGA championship long drive.) He beat much better players in an era of superstars, and had a much longer career even dominating into the senior tour.

I think that people make decisions in their heads about things that have little or nothing to do with reality
LOL You're funny.
 
Anyway, regarding what throat diameter might be too tight, I based my thoughts on two key points...

One is the obvious angular variance that is possible when the projectile is loosely guided toward the centerline of the rifling. The more the long axis of the projectile coincides with the long axis of the rifling, the more (at least theoretically) accurately the bullet will enter the rifling, and fly with less axial wobble. Heavy VLDs are long and difficult to make fly straight. Keeping such projectiles axially aligned with the bore is paramount with them..

So to this point alone, tighter is better, but with the caveat that the free bore diameter is not too tight. This is the grey area.

My assessment of what is too tight is largely based upon my own observations but also supported by the technical article linked below.

If you bother to read the article, keep in mind that he is discussing a 308, not 223. The importance of this distinction is pertaining to clearances. In this case, the largest "tight" free bore diameter evaluated was just 0.3085, then he made a jump all the way to 0.310 and avoided anything in between, likely for practical reasons. Either way, the .3085 throat is relatively tighter than anything I have suggested for 223.

What is clear from the article is that too tight causes a significant pressure spike, but too tight in this test is well below the bullet diameter. This is not something I'm suggesting.

What is unclear from the article, is at what point over 0.3085 an increase in free bore diameter equates to pressure resulting from a 0.310 free bore diameter. We are not left with a choice of 0.3085 or 0.310, as there are options in between.

 
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They can't actually prove gravity exists, but Steven Hawking said that the "universe could create itself out of nothing because of gravity" (paraphrasing). Steven Hawking must have been super smart because he spoke with a robot voice.

This is how I see most of these conversations.
 

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