300 whisper = pita

[800X]

This thread isn't meant to discourage anyone thinking about building a 300 nor is it meant to bash any vendors, but I have to share my problems with the hope of helping others if possible.

A buddy and I each decided to play with the 300 in an AR platform. We each bought uppers from M1S. Right off the bat we have had trouble with rounds chambering. We started with CorBon 220 subsonic and then loading our own with brass we bought off the web.

Our successful feed rate was maybe 2 in 5. During all of this we also were having terrible keyhole problems with anything heavier than 180gr.

After much frustration we checked the twist rate as best we could with a cleaning rod and we positive that our barrels were actually 1 in 10 not 1 in 8 as advertised. So the feed problems became secondary to getting new barrels.

I called M1S and explained my findings expecting to get some grief. Surprisingly they were not at all reluctant to offer new barrels. This made me think they were expecting calls of this nature. They assured me that we were the only complaint they have received on this matter. I guess it’s possible, however unlikely that we bought the only two 1 in 10 barrels out there.

It took quite some time to get the replacement barrels (months) but overall I think M1S was as helpful as they could be. This brought me back to the feed problem. We decided right off the bat to start fresh with 221 fireball and form it ourselves. This has worked extremely well. So we tried our formed 300 whisper brass purchased earlier and immediately had the same problems.

The brass bought from keith_davis is, as posted by him trimmed to 1.390. I believe this is our problem. The 221 formed by us usually ends up at only 1.350 - 1.355.

To Mr. Davis's credit, he has contacted us more than one telling us he is happy to help us with any problem that may be brass related. I think he is a stand up guy. At this time however I think that I will wrestle with this myself because the brass was received exactly as described.

I have a crappy Lee trimmer that requires I use deprimed brass to trim. I am trimming some tonight and will be function testing this weekend. I will post my results. I am afraid I will have to deprime the 900+ primed cases I bought so I can trim them, but it will be well worth it if this solves my problem.

FWIW, I have not had a cast of my chamber but I checked the neck diameter with a gauge pin and found both barrels to be .336" Both the 221 and 300 brass I have measures about .332 loaded. This is a fairly tight fit for an autoloader, but I think I am OK.

The moral of the story is that M1S barrels seem to require a trim length of 1.355 (all four of the barrels had this problem) and be sure to check the twist rate before you pull you hair out.

[Cornholio]

Definitely keep us posted. I'm very interested in your developments.

I am starting out myself. I am having problems with the Redding 300/221 2 die set I just bought from Graf's. I don't think the decapping pin is screwing down into the FL size die far enough. Every time I try to use the 300 expander, the brass gets stuck before I'm able to size. I think the expander is still partially in the neck area of the die, because if I really force the ram, the neck starts to actually swage, and if I keep going, the neck gets crushed near the shoulder. And even then, the primer is not being decapped. Redding customer support wasn't all that helpful over the phone, but told me to send the die in.

The only way I've been able to load ammo so far is to remove the decapping pin and size without it, then expand the case neck with a K&M Expandiron used for neck turning brass. Then load as normal. Either that, or I have to thin the necks down significantly with the neck turning tool, and then I can use the die with the decapper installed (even though it still doesn't decap). I am using once fired Remington .223 brass trimmed to 1.43". I was going off the diagram for .300-221 as seen on www.ar15barrels.com, which shows the case length to be 1.450".

I was planning on buying some brass from David Davis myself. I contacted him about some free samples he offered in his advertisement. He responded twice, but I haven't gotten any brass from him. He also has not responded to my emails since then.

[cherokee]

I had the same problem with brass from davis. I found that I had to resize the brass twice before loading it (Turning the brass 180 deg between passes)then it fits in the chamber. Once it has been fired in the weapon it works well. Maybe his resizing setup needs some adjustment. I would still buy brass from him again. His brass is reasonably priced and it saves me the hassle of making it my self.

[Cornholio]

I must have spoke too soon. I just received an email from Mr. Davis. He was out of town. I'm looking forward to trying out his brass!

BTW, what is stamped on the Model 1 barrels?

Mine is stamped (rather sloppily) "SS 300 FB" on the top of the barrel half-way down the length, and "300 FB 1/8" on the bottom near the chamber. Supposedly, it was an Armalite barrel, but I have never heard of Armalite making .300 Fireball barrels.

[Cornholio]

I had the same problem with brass from davis. I found that I had to resize the brass twice before loading it (Turning the brass 180 deg between passes)then it fits in the chamber.

Damn, what gun are you using? That is one tight chamber!

[800X]

OK,

Back from the range.

I trimmed 10 of the CorBon empties (lake City brass) and 15 of Mr. Davis's brass to a length of 1.345". All were resized once more for good measure and loaded with Sierra 220gr MK over 10.1 grains of H110.

The good news is that everything fed beautifully. I was impressed with the smoothness. I really think that I have solved this issue finally.

The bad news is that this upper (my buddies) would not cycle completely. I'm back to the same issue where it won't strip the next round. I had this same problem with the first two barrels I bought, and I finally had to move the gas block back to correct it. The first of these replacement barrels (my upper) cycled perfect right out of the box this time around. This means that 3 out of 4 M1S barrels will not quite cycle. Before I put my foot in my mouth on this issue, I will play with the upper a bit more.

So problem one is finally solved. From now on I will trim all my brass to 1.345. I think it is strange to have a cartridge with so many listed trim lengths but I know this works and I won;t be looking back.

[800X]

Also, I wanted to add that I measuded the neck diameter of all my rounds before I left. The CorBon, the 221, and Mr. Davis's brass all measured between .329 and .333. Remember I had measured my chamber neck to be .336. I found the spread between all three types to be about the same. I have no idea if CorBon neck turns but none of the brass was too thick. I was planning on keeping track of neck diameter while I shot so I could see if the larger necks were causing problems, but the perfect record today has made this a moot point.

[Gos]

It's a pretty common mistake to trim 5.56 brass down to 1.4 since that is the length of the .221 fireball; but not the 300 whisper. The real trim to length for the 300 whisper is 1.355".
Don't feel too bad. Even the new Hornady book got it wrong.

How about a sticky for the trim to length?
Gos.