I got a 223 Wylde chamber reamer w/ go/no-go gauges couple weeks ago.
I have read about barrels marked 556 that were really 223, barrels not marked at all etc. So I decided that I would lightly ream my mid 90’s bushmaster A1 barrel. Which has been shooting fine since I got it in 97, the only problems I have ever had with it were magazine related with surplus mags.
After about a dozen turns (just finger pressure, no T handles or wrenches) and this is what I saw when I stuck the borescope in to look;
(not the best pic, I had to hold the camera to the eyepiece)
As you can see, it is only cutting on the right side of the neck area.
I called PTG and asked about it. They said that chambers reamed off axis was common on mass produced barrels in the 90’s. They said that they have even seen that in hammer forged barrels. Mostly it was worn bushings on the machines.( I am sure a sloppy setup would do the same thing.)
( Last week I reamed the chamber in my Rem700 as it was a .223 chamber and it came out fine. I read up on the 556/223 when I got the rifle about 10 years ago. All my ammo at the time was surplus 556, so I was concerned about it. I had no popped primers or signs of overpressure so I didn’t really worry about it. I finally had some money to get a reamer)
That said… I have to inject my usual sarcasm and point out that you’ve got a bore scope… sprung for the reamer… but you’re hanging on to a 90 bushmaster???
And I have little to no faith in the “usual pressure signs” after having various batches of ammo pressure-tested at a certified lab.
I mean, when a handgun round fired in a test barrel produces twice the “book” pressure, and is high even by rifle standards, and shows no “pressure signs” I’m not sure what I should be looking for.
Sweeney is right, “pressure signs” are very, very unreliable. I recently worked up two loads in two different rifles and the first sign of high pressure was blown primers. I used to be a firm believer in “reading” “pressure signs”, no more. As to chambering a rifle barrel, this is a very easy operation to mess up. I have a Remington M700 heavy barrel 243 with a chamber cut badly right at the Remington factory. I have seen the same in a Weatherby, a couple of Winchesters, even a Sako. I think your experience is proof that if something works to your satisfaction don’t mess with it that is to say, unless you have an actual problem that manifests actual symptoms, leave well enough alone.
Depends on the powder. Pressure signs can be effective… but like anything else they should be taken in context and preferably with a chrono. There are some powders that are sneaky like a snake. XBR 8208 and one other (which I’ve can’t remember and haven’t personally experienced anyway) where the powder will turn on you quick with little warning.
I had XBR start popping primers on me on a load after changing powder lots.
Many if not most production barrels are not concentric. That borescope should tell you that. Even barrels produced by companies that make high end Highpower barrels have throats that are not concentric. One company that produces a lot of stainless 5.56 and sells complete rifles turns out barrels by the thousands with off center throats. Some of those barrels will shoot fine and some will not.
Something to think about-- Barrels are spun, the reamer held still but in a floating reamer holder. The reamer will follow the bore because of the pilot on the front. The reamer spins in the pilot following the bore.The rear of the reamer in a floating holder will follow the hole bored by the front of the reamer following the bore. How does a reamer cut 1 side of the throat off center of the bore. Answer is in the pilot.
Actually there are 2 ways the throats could be off center but 1 is highly unlikely. The lands on one side of the barrel could be taller than the lands on the other side.
Constructor: thats what PTG pretty much said.
Justin: I did it because I have read many many threads/stories etc about mismarked chambers and I wanted to see .
Mist wolf: yes, I had to see for myself.
I am the type that ~has~ to do things myself. Unless it requires equipment etc that I don’t have. Or that I know I am not good at ie: car bodywork and paint. My first 1911, I was always trying things. Different springs, guide rods grips etc. Sometimes I would get to the point that I had to take it to a gunsmith because I didn’t have the tools, or I when I put a extended safety on it, I just wanted it checked to make sure I did do it correctly.
One day I took it to the 'smith and he started bitching about the idiot marks I made and how people might think that he did it. I started to say something, but he said “do you know how I got my start?” I said, “probabley doing what I’m doing” He said “yes, if you want to know how something works, you have to get into it and take things apart, see how everything works and interacts and put them back together. You have to get your hands dirty”
I know Ned Christianson at MichiGuns sells a .223 to 5.56 reamer that has an integral pilot and only cuts the throat dimension. As has been discussed many times here, 5.56 in a .233 chamber will street the gun and accelerate wear but not turn the gun into shrapnel.
I know BCM makes a very high quality HF 5.56 bbl. I’m quite sure that BM bbl has a HUGE gas port anyway.
I know what you’re saying, given BM’s rep; it’s hideously over gassed; they always have been. If you read some of the gas port, short stroking and buffer threads here, you might be able to find some ranges of the size.
I would take a guess that BM probably didn’t mess the port up (terribly). Since you indicated that this is an A1 barrel my guess is that it is in the .093-098 range.
Most of the port issues I have seen were with their other offerings. 16", 14.5", SBR.
