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Discussion Starter · #1 ·
So I turn on the computer this morning and hit the forum here, the first thing I see is the new link system to Biz rate and click for the Military M14, I end up at Brownells and see this....

.308 Match Ammo Chamber Reamer
For military M-852 match ammo (168 gr. bullets, M14 length); or any load using Sierra 168 gr. boattail. ??????????????????

WTH ???....Which is it ?...It can't be both. And wth is M14 length ? Is it M-852 Nato round, or a dang .308 ?.....geez, no wonder people have trouble with their rifles function and ammo selection. If I thought it would do any good, I would call them about this.

The two are only .00355 off from each other !! Not to mention the degree difference on the bottleneck for a match reamer.
No problem Right ? OH, those should function real nicely.....I swear, I give up......
 

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I'm guessing M14 length means that the lands are a reasonable distance (0.02" jump or so) from the bullet for a 308 win bullet that is loaded to M14 maximum magazine length, or therabouts.

I'm guessing how far you ream determines if you have a shorter 308 or a longer 7.62x51 headspaced chamber, so I think their description could be correct.
 

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I know reamers are confusing. Here is my guess. The M-852 uses the 168 BTHP projectile and the .306 match reamer is set up with a little longer throat than a standard .308 reamer. When I picked up my .308 obermeyer match reamer, I was told the difference between the .308 match and the obermeyer was the throat length and the cone angle. Both were a little larger to accommodate the larger round. The obermeyer was designed to be used with the M-118 ammo or the 173 BTHP round. I chose this reamer because I shoot 175 SMK' exclusively. The one person I know that has the answer for sure would be Ted Brown. He did a lot of explaining to me when I was in the market to buy my first reamer. I do know the cone angle on the obermeyer is 2.5 and the .308 match is 1. Something, I think 6.
 

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Discussion Starter · #5 ·
Nope, their description is not correct. There is no such thing as M14 length. The cartridge OAL or distance from the lands has nothing to do with chamber reaming. It is either 762mm or 308.
 

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I believe the first comment about being short throated is probably correct. I used a "Palma Match" reamer on one of my guns rather than the Commercial .308 Winchester reamer. There would probably be an interference fit if I ever tried to load a 180 grain round nose bullet, but with a HPBT match bullet, the jump is very near ideal IMO.

The bullet and Cartridge OAL are quite relevant if your chambering reamer also cuts the throat. The pull through ones driven from the muzzle do not affect the throat.

- Ivan.
 

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Discussion Starter · #7 ·
As you can see from these photographs, the throat is clearly affected by the pull through muzzle driven, and the chamber driven finish reamer. The beginning of the rifling is also affected by the reamer. These knives set the 762MM Nato chamber only one way, headspace and throat depth are achieved by the operator's expertise, and bushing installed.

Yes, you can get custom reamers for custom set-ups, but not as in their advertisement, it is either one, or the other. It cannot be both.
 

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Guys, I'm curious: is this in any way akin to the .223 vs. 5.56 vs."Wylde" chambering differences, only in .308?

As I said, just curious. You boys obviously have a wealth of knowledge on these mystery chambers, and I do not.
 

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Discussion Starter · #10 ·
Yeah Mesa, it's pretty much the same in 5.56 and .223.

To add confusion to the already longer G.I. chambers, as opposed to the commercial .308, the military takes their headspace reading from .013 further down the bottleneck on
7.62MM
 

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Amazing!

Wonderful! Moving the headspace ref datum point?

Well, being our government, I'm sure they had their good reasons, huh?
 

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Discussion Starter · #12 ·
Actually, I believe the military was first, and the commercial folks went a different route with datum location, of course, I could be wrong, but I won't tell anyone if you don't.
 

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Discussion Starter · #14 ·
Yep, but it was because of a request from the military to develope a shorter cartridge with roughly the same ballistics as a 30-06, for their new main battle rifle design, our beloved M14's. Of course, as usual, you are correct Phil. DI5
 

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How much of a difference do you fellows think it would make to ask a custom reamer maker of great quality like Pacific to make a reamer with the headspace of your choice that put a certain bullet, like say the 168 grain SMK a 10 thou jump off the lands if it was seated to 2.800"?

You would have to use it on an unchambered barrel, but with the price of a real US M14 up here...

I'm not saying it would be night and day different, but I would love to see the result if the barrel were treated like a precision bolt gun barrel. Dialed in with a spider on the offside of the tailstock, and made true using a range rod down the bore indicating the truest you can instead of by reading the outside surface of the barrel...

Wish I was rich!
 

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Discussion Starter · #19 ·
They will not only do the custom work, they will create the CAD drawing and program for your project and add it to their long list of files for future smiths. Might even name it after you if you ask....except I would call it Green River Reamer DI5

Sounds like a plan, do you need my address so you can send it to me to try out, when you are done ?GI3
 

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Very interesting, Ripsaw! The more I think about it...you know, that would probably also be one accurate bolt gun chamber that could use 7.62mm ammo in a pinch, unlike most 308 Win precision rifles...

You and this forum are evil GI1

We'll share custody.
 
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