Neck Diameter Various Brass Loaded Rounds?

[JASmith]

Lemonaid,

Excellent read.

Thanks for the link,

[BluntForceTrauma]

LA, good article. Thanks for the link. I notice that while the new 300PRC has a SAAMI minimum freebore spec of 0.3088 (meaning 0.0008) over nominal bullet diameter, the 65G SAAMI spec does it one better at 0.2644 (0.0004 over bullet diameter). So, if -- as the article claims -- a tight freebore aids accuracy, then the Grendel has had that feature built in from the start.

[LRRPF52]

Just for fun, am gonna try some mag dumps with 6.5 Grendel Wolf steel-case in an experimental chamber with a tight neck. After two mag dumps of 25 rounds each, will let a round of green-lacquered steel-case sit in the hot chamber for ten minutes and then attempt to fire and extract. We'll see what happens.

Any other testing protocols to suggest? Will report back in a couple months whenever barrel and testing gets finished.

I think it was BWaites who tried this with a 16" BHW barrel that had a .295" neck, not even mag dumps, but normal low-volume firing. Choked up pretty quick.

Runs fine with factory brass ammo, but not the steel case.

There aren't any unturned stones with chamber dimensions in the wake of Bill Alexander's testing with $11,500 in different reamer designs, with barrel costs in addition to all of that. It will be an exercise in duplication of what is already known.

[BluntForceTrauma]

I think it was BWaites who tried this with a 16" BHW barrel that had a .295" neck, not even mag dumps, but normal low-volume firing. Choked up pretty quick.

What is your theory about why it choked up? Lacquer build up? This stuff leaves behind minute amounts of melted residue, or what?

THIS TORTURE TEST may or may not be definitive, but they also tested the variable of steel-case with either lacquer or polymer coatings. See the subhead titled: "What Effect Do Coatings Have on Steel Cased Ammo Performance?"

I quote at length from the online article:

"A common belief is that the lacquer coating of certain steel cased ammunition will "melt" in the chamber of a hot rifle and cause subsequent rounds to fail to extract. At one point, we might have believed that.

But in this test, we saw three times as many failures to extract with the polymer coated Wolf brand ammo (15 extraction failures) than with the lacquer coated Brown Bear ammo (5 extraction failures). Although we fired the polymer coated Tula ammunition in different rifles, the rate of extraction failures in those rifles was lower than that of Wolf.

There will be a very small number of stuck cases experienced when shooting steel cased ammunition, but we didn't see a correlation between lacquer coatings and stuck cases.

If anything would make that lacquer coating "melt," it would be the treatment these rifles received during the test. We shot them until they were too hot to hold — hot enough that a chambered round would cook off in 10 to 15 seconds. We also tried leaving rounds chambered before temperatures reached that point. None of this harsh treatment caused extraction problems.

We found no evidence to back up the claim that lacquer coatings melt in the chamber and cause extraction failures."

[LRRPF52]

What is your theory about why it choked up? Lacquer build up? This stuff leaves behind minute amounts of melted residue, or what?

The steel cases don't seem to be as elastic as brass, so they allow more carbon to flow back around the neck area of the chamber.

This builds up and leaves no room for extended shooting sessions.

Same reason we have to clean suppressed gas guns more often.

I've also noticed with many AR15s that I've owned in 5.56 that when I fire a lot of steel case, then switch to brass, they would Fail To Extract.

The brass necks obturate and lock in with the carbon residue, creating too much friction, and win the war with the extractor trying to rip them out.

Going to a .295" neck with the Grendel and shooting steel case basically eliminates your necessary tolerance for extraction.

For chambers I have shot nothing but brass case through with .295" necks, I've had no problems, but there have only been a few of them.

[Wethepeople]

This is a great thread. As a former machinist/CNC programmer I really appreciate the knowledge being shared. It's dispelled some myths about steel cases I had previously bought in too as well. Carry on. Jeff

[A5BLASTER]

After shooting a couple of thousand rounds of the wolf fmj ammo through a few grendel barrels now this is what I have seen.

Not once have I seen any evidence that the coat put on the steel cases melts and comes off in the chamber.

I don't typically clean my rifles until the accuracy starts to drop off and I can't say I have found anything other then normal carbon build up in my sammi chambers.

Now I willing to admit that it could become a problem in a tighter necked chamber. But not having any experience with a rack neck chamber I am interested in what findings BFT comes up with.

On a side note BFT. The Barnaul version of the wolf fmj isn't laquar coated it's a backed on powder type of coating. So maybe a head to head test.

One barrel fireing only the wolf version and one barrel firing only the Barnaul version.