Markings on bullets

[chris allen]

Which way does gravity work ?My thoughts are its from the junction of the chamber where the end of the neck is and the leade (where the bullet sits in the chamber) .Absolutely nothing wrong . Chamber could use a little polish but nothing to be concerned about .
Chris

[13Fox]

I don’t have access to a bore scope. Wish I did…

The dummy cartridges that I have been experimenting with have a runout of .002-.003. Not perfect but not terrible.

I am experimenting with the suggestion of extracting the cartridge producing the marks. While the bolt does not have the striker or ejector in it to put pressure on the head or bolt, I cannot take the extractor out, and agree that pressure from the extractor maybe creating some “misalignment” and the bullet may be scraping during extraction. I am in the process of investigating this and will advise when I come to a conclusion.

The markings are at the 6:00 to 10:00 position, which generally is opposite the extractor. I would expect extractor related marks to be on the same side that the extractor is…

But like I say, I am still playing with this thought as I am not convinced that the extractor is not a problem.

I spent some time Sunday night taking some chamber castings. Took me a few times to get a good enough casting… I think that small bore was creating some bubbles and I couldn’t get a good casting at the throat. Third attempt gave me a pretty good casting. I had not noticed the ring just above the shoulder as hemiallen pointed out, but sure enough, this ring is present on the castings… Thanks for calling attention to this!

What I did find on the casting is that it appears that the first +/- ¼” of the rifling has some issues. Three of the lands do not end at the leade as the other three lands do.They appear to possibly be eroded away, and my guess is from a misaligned reamer. The “erosion” is short at the first short land, and gets longer at the second and longer yet again at the third… This rifle probably has a total of 300 rounds so I cannot see any throat erosion being due to firing.

I could not identify burrs in the throat/leade that would create the marks on the bullets.

I examined the casting under magnification. I will admit freely that the casting is not a textbook example and perhaps may not be good enough to fully define this area. But the other lands and grooves are perfect, so I feel that it is a pretty good casting, but not perfect.

An evaluation with a borescope would be ideal, but unfortunately, that is not feasible at this time.

If I am dealing with a misaligned chamber and the rifling is not complete to the throat, then to me, this tube is never going to give me better groups than I am getting now, the best of which are 1.” Any thoughts?

On a side note, the neck is perfectly round and measures 0.2072"

Thanks again,
John

[chris allen]

If you go to Hornady site or have a Hornady manual the have some great pictures of how a cartridge is situated in a chamber (Internal ballistics). I still believe it is the edge of the leade where it joins the chamber .
Chris

[Chuck Miller]

Frankly, your talking about a 500.00 factory rifle that shoots 1" and I'm not convinced that your issues at the chamber will necessarily improve on that number. Probably more a function of the total quality of components used. I notice your shooting a vmax, have you up'ed the anty and gone to a premium bullet? If you were shooting 3-4" groups I could see where you would be taking a hard look, but 1"? There are just so many factors that could be holding you back from breaking the 1" barrier. I have a Savage 223 that has all the same issues you've mentioned plus about 6 more including an oblong chamber and it shoots under 1", with premium bullets, 36X Leupold and the best front and rear rest money can buy. I have a Cooper in 223 that won't break 1" with a Vmax?? Heck, a misadjusted parralax on your scope will keep you from breaking 1"

But then again I shoot with cretins that do high fives when they hit 6 outa 10 on a 2'x3' Bin Laden target Good luck on your search.

[rick w.]

I tend to agree with Al's method of taking a look at bullet depth. The old method of seating a bullet overly long, then polishing the bullet with 0000 wool does make a nice indication of a ring of marks.

One should have marks around the perimeter of the bullet that reflect contact in the throat/lead area. One thinks that the marks should be very much alike in width and depth, signifying a centered cut into the rifled bore.

Some use these marks to set their depth of seating of said bullet. Some like just a little touch, while others use a hard seat.........all in the results given on the target with the components of the day. I have seen cheapo bullets shoot very well in some rifles, awful in others; luck of the total draw one might say.

I was trying to think how a reamer with cutting edges twirled around would cut some parts of the barrel and not the other. A mystery to me but have not thought about it much.

I could see wear from a cleaning rod causing partials in the throat, which can be slowed by a nice two piece rod guide; but nothing is perfect there, but the guide will help lifespan.

It would be interesting to see a longish,0000 polished bullet from the chamber insertions, does it have a mark for each land etc?

I would have thought that lots of throat burning by shooting long and hot, would have been a bit more symmetrical, just a guess on my part. The seating depth can change quite a bit in a newly chambered barrel in the first forays on the line.

I reckon if you are not into the lands at all, then removing a dummy cartridge with bullet might make a mark due to the stout ejector causing the cartridge to cant outward on the rear of the neck area.

[Hornet lover]

I shoot with cretins that do high fives when they hit 6 outa 10 on a 2'x3' Bin Laden target [/quote]

I love it

[Al Nyhus]

There's much to be learned from having a visual of the rifling and how it contacts the bullet.

This really isn't that hard....... -Al

[13Fox]

More experiments undertaken…

Chambered dummy cartridge as suggested (no bolt, seated straight in with dowel, pushed out with rod. Exact same marks as photos, no evidence of rifling on half of the diameter of the bullet.

Seated bullet way out polished with 0000 steel wool. Dummy chambered easily and engraved rifling marks. Very clear rifling engravings at half of the diameter; Other half of diameter produced extremely faint marks. If bullet had not been polished as suggested, I am confident no marks would have been observed at that half. Also present were the same marks as the photos.

Tried the polished bullet method of determining seating depth as explained by Al Nyhus. This was a shocker to me… The final depth arrived at with this method is .030 deeper than all the other methods I have used for determining depth for this bullet in this rifle. Of note also, is that marks were present only on half the diameter for vast majority of adjustments. Also, great care had to be taken going in and coming out to minimize markings on the bullet that matched the same marks as the photos.

I have produced better accuracy than 1" groups with factory 700's varmint style rifles so I did not feel that better than 1" groups were too much to expect. Perhaps I need to re-evaluate.

Rifle is Remington 700 SPS Varmint, in a HS Precision PSS stock, Leupold bases and rings, Leupold 6-18x AO. Loads tried included Remington brass, CCI, WSR, Rem, Fed primers, 20 and 25 gr VMAX and 20 and 25 gr Berger bullets, Powders tried have been Benchmark, H335, 4198.

[chris allen]

This is my method of finding seating depth as to find where the bullet touches the lands .
Need :
1 brass fired but NOT resized .Make sure brass fits the chamber.
1 bullet that is in question
5 minute epoxy & toothpick

Mix the 5 minute and put a small amount on the INSIDE of the neck only.None on the bullet
Set the bullet carefully in the neck barely started into the neck.
Carefully chamber the round and close the bolt .
Allow the epoxy to set
Remove dummy and that is the seating depth to touch the lands with that specific bullet .
Chris

[MIBULLETS]

That's a new one to me Chris, sounds like a good one too.