Lee Loader

Ranch Dog wrote:Thanks for the info! Makes me glad that I spent my 7.62x39 money on the target cam.

I don't blame you. My Howa Mini in .223 is a great rifle and this was a real let down. I'm out of the mood to buy any more guns now.

Forgive my ignorance but what am i looking at? I dont recognize any obvious defect in those pics (but would like to learn!)

GRV01 wrote:Forgive my ignorance but what am i looking at? I dont recognize any obvious defect in those pics (but would like to learn!)

The problem is where the rifling starts in relation to the "neck". I've put the two Howa pictures together, remember these are opposite sides. Look carefully where the rifling begins. It's lopsided.

What I find interesting is all three barrels have the same defect. The Howa barrel according to their site is hammer forged. It is highly unlikely that the rifling defect occurred during this process unless perhaps the barrel blank was not drilled straight. I couldn't tell from the information they give if the chamber profile is rough forged at the same time. We are assuming that the drill/cutter/reamer wandered off centre or was not centred when the chamber was being made. What caused this is anyone's guess. One has to wonder how widespread is this defect. It probably affects accuracy but will it also raise pressures as there is virtually no lead on one side and bullets may be jammed against one land?

My first thought was that it would push the bullet to the one side and then when it engaged the riflings that are just starting, that it might be off center. Would it recenter itself or not? How would you correct something like this? Would you have to trim some material off the back of the chamber, and rechamber the barrel?

I suspect the only way to correct that is a properly chambered and rifled barrel. Even with hammer forging I think the chamber has to be cut. Fact remains no mater how you do it the center line of the bore and the barrel need to be coincident. Good barrel making is part science and part art and you don't get art from push button machines unless the science is right.

Make smoke,

I have been doing a lot of reading on the subject since this post and it appears that problems keeping the bore and chamber concentric to each other are not uncommon even in expensive rifles. Worn reamers, too high feed rates, hard spots in the barrel steel and the use of floating reamers are mentioned. The effects on accuracy caused by the deformation of the bullet was quite interesting especially in one article that used a mathematical formula developed by a ballistician to estimate dispersion of POI caused by changes in centre of gravity. The same article gave some tolerances for commercial and custom match barrels. I watched a video of a custom chambering of a Shilen barrel (Savage action) that put it all into easily understood perspective.

With respect to hammer forging, this is a good article. They cover integral chamber forging in the article.
http://biblioteka.mycity-military.com/b ... arrels.pdf

On my shopping list is an ingot of Cerrosafe. Wonder what I will discover?

Interesting, thanks for the perspective

I think the reason they all appear to have the same defect is the same reason that punctured tires are all flat on the bottom.

So when you cut the chamber off center the rifling will be closer to the case mouth on the side that gets the least amount of cutting and farther away on the side that get the most contact with the cutting tool. Just imagine two cylinders meeting at an angle.

In private communications with experienced gunsmiths, this problem is not a rare occurrence.

Oddly enough, one of my students said it best today. (He's 12 years old and competes in 3-Gun and Run-n-Gun competitions and he'll tell me shooting stories during free time like recess). Anyway, today I told him about my chamber issue. He asked if all three barrels were made by the same company. I told him no and that this problem was more common than people realized. His response was, "I'll bet they haven't looked."

Macd wrote: especially in one article that used a mathematical formula developed by a ballistician to estimate dispersion of POI caused by changes in centre of gravity. The same article gave some tolerances for commercial and custom match barrels.

Very interesting. If you would point me towards this article, I'd appreciate it.