Alpha brass base not flat

[Mj30wilson900]

So with my alpha brass I have found the bottom of my cases to not be flat and the shoulder to be .01 away from first firing.
After first mild load the brass smears the cartridge wording slightly as that base flattens against the bolt face and the shoulder elongated to my rifles chamber.
Putting a straight edge on the bottom of my brass revealed the concave bottom. Is this normal with alpha brass? I also get heavier than normal bolt lift.

 

[Maurygold]

Alpha brass is best in class. Load, and chambering are more likely to be an issue than the brass. Especially with heavy bolt lift

 

[OREGUN]

So with my alpha brass I have found the bottom of my cases to not be flat and the shoulder to be .012 away from first firing.
After first mild load the brass smears the cartridge wording slightly as that base flattens against the bolt face and the shoulder elongated to my rifles chamber.
Putting a straight edge on the bottom of my brass revealed the concave bottom. Is this normal with alpha brass? I also get heavier than normal bolt lift.

So before firing the base is concave and after the first firing, the base is “flat” and the shoulder has advanced .012”? Is that a correct rephrasing of your first two sentences?

Alpha staff are the people to ask about the case base shape.

Regarding the bolt lift and case smear, your load might not be as light as you think AND/OR you may be experiencing some case thrust as the smallish case expands into your largish chamber…similar to what you will get if you have a gross sizing error or some case lube left on your case. Frankly, I wouldn’t worry too much about any of it until the brass has been fire formed and you are able to control the shoulder dimension…except that I would back down on the load a bit more to eliminate the possibility that you are just over-pressuring the system.

If you are too inquisitive to do nothing, load a few with the bullet “jammed” into the lands (so the bullet holds the case head against the bolt face). This is a fire forming-wildcat trick that should eliminate the case thrust condition.

 

[DownhillFromHere]

OP, there's a fair amount of info missing here. Over the years, I've had a couple of dud cases appear in a new batch of top-tier brass, but it's highly unusual.

• First, you said you have heavy bolt lift, ostensibly with mild load - what does that mean? What caliber? Bullet? Powder charge? Primer?
• I just checked a new Alpha 6BR case - its head is slightly concave, with ~.001-.0015" showing under a straightedge next to primer pocket.
• "I have found... the shoulder to be .012 away from first firing." Are you saying the case grows in overall length on first firing, or just the shoulder? How are you measuring? In my experience, a .012" shoulder movement on first firing is a lot. I find my new brass to typically be "short" at the shoulder by ~.003-.004" from nominal center of SAAMI spec measured with a Wilson case gauge, and .002-.003" over center spec after first firing.

Beyond all that I agree with Oregun.

 

[Mj30wilson900]

So the cartridge is 6gt
Measured it with a starrett digital caliper and a headspace comparator no bullet in case.
Going to order a Wilson case gage and use a interapid indicator on a granite to recheck.
Mild load was lowest in Hornady loading manual with Varget.

 

[OREGUN]

The only new Alpha brass I happen to have here is 25 x 47. I think I see the concavity you’re talking about. Without someone suggesting I look for it, I would never have seen it. I would go out on a limb to say that that’s not an imperfection in the brass and you should completely stop worrying about it.

I also looked back through my notes on several different chamberings using Alpha brass. The range for initial shoulder growth seems to be somewhere between almost nothing and as much as .006”. All of those barrels are custom ordered and chambered by the same smith so may not be representative of a factory barrel or one chambered by someone with different ideas about headspace precision.

Your comparator is a fine tool for the job. The case gage may just further confuse the issue. Resize a piece with somewhere around .003” of shoulder bump as measured with your existing equipment and try the same load/seating depth, etc. I’d bet your case head smear and heavy bolt lift both go away. If they don’t, you are definitely over charged without regard to what Hornady says.

 

[Mj30wilson900]

 

[Mj30wilson900]

 

[Mj30wilson900]

 

[Mj30wilson900]

1.343 Alpha V.
1.353 Alpha O.F.
1.350 Hornady V.
1.353 Terminus shoulder length.

 

[OREGUN]

1.343 Alpha V.
1.353 Alpha O.F.
1.350 Hornady V.
1.353 Terminus shoulder length.

I don’ t know anything about 6GT dimensions but if those were my measurements, I’d write them down as reference and keep doing what you’re doing. Looks fine to me. Hornady’s load book is useless unless you are using their brass so…back off the load a little more and try the bullet jam method I mentioned above. Or do nothing and accept that the alpha brass is experiencing some case thrust on first firing.

 

[DairyDictator]

If I remember right the SAAMI headspace tolerance range for 6gt is +0/+.01"

The Alpha brass I measured was .0005"-.001" shorter than my go gauge. Sounds to me like you have a chamber cut to the high end of the tolerance. Not really an issue, just set your dies to bump .003 off a fired case.

Is any of this really an issue? How's it shoot and how's the velocity spread? If it's good, forget any of this ever happened and move on with life. If it's not, try contacting guys that do this stuff professionally (Alpha CS) instead of taking advice from rando's on the internet.

 

[DeathBeforeDismount]

So with my alpha brass I have found the bottom of my cases to not be flat and the shoulder to be .01 away from first firing.
After first mild load the brass smears the cartridge wording slightly as that base flattens against the bolt face and the shoulder elongated to my rifles chamber.
Putting a straight edge on the bottom of my brass revealed the concave bottom. Is this normal with alpha brass? I also get heavier than normal bolt lift.

How old is it? There was bad batches of alpha brass where the base looked like a bannana. I think they were pre OCD but either way you should warranty them with Alpha. I bet they will take care of you and replace it quickly. Is it one piece of a bunch?

FYI I have about 3,000 pc of alpha brass I rotate through. Great stuff but everyone makes a dud once in a while.

 

[Mj30wilson900]

How old is it? There was bad batches of alpha brass where the base looked like a bannana. I think they were pro OCD but either way you should warranty them with Alpha. I bet they will take care of you and replace it quickly. Is it one piece of a bunch?

FYI I have about 3,000 pc of alpha brass I rotate through. Great stuff but everyone makes a dud once in a while.

Brass is less than 4 months old

 

[OREGUN]

One thing to keep in mind in case you’re not aware of it, that expansion in the new brass is not going to give you your best ES and SD data.I wouldn’t get too wound up trying to nail down a super precise load until you’re dealing with fireformed brass. You’ll be able to get close, but if you’re reloading process is really tight, I would expect that you can cut your SD in half once you are using fire formed grass.

 

[DeathBeforeDismount]

The measurements you are getting are not really an issue. Brass without a flat base is.

Fresh Alpha brass shoots just as well (if not better) than my reloaded brass that is annealed, cleaned, sized with SAC mandrel, cleaned, trimmed and loaded. Heavy bolt lift is probably due to pressure, fucked up chamber or something else. You also need to make sure chamber and throat areas are clean.

Lastly, those Hornady comparators are garbage. Most Calipers are really only accurate to about .001 anyway so if you are within a thousandth or two so Its most likely a measurement issue. Combine those two and you will get variances all over the place. I threw the Hornady shit in the trash and replace with the SAC set. MUCH more reliable and accurate.

 

[straightshooter1]

One thing to keep in mind in case you’re not aware of it, that expansion in the new brass is not going to give you your best ES and SD data.I wouldn’t get too wound up trying to nail down a super precise load until you’re dealing with fireformed brass. You’ll be able to get close, but if you’re reloading process is really tight, I would expect that you can cut your SD in half once you are using fire formed grass.

Typically, I find this is true. Spring of last year I finally got some Alpha brass for my .308 and loaded them up to fire form, not expecting any kind of good results. To my surprise, 80 consecutive shots chronoed showed an SD of 6.2 with ES of 29. I've never had virgin brass do so well, not even Lapua.

Just an aberration, I guess.

 

[OREGUN]

Typically, I find this is true. Spring of last year I finally got some Alpha brass for my .308 and loaded them up to fire form, not expecting any kind of good results. To my surprise, 80 consecutive shots chronoed showed an SD of 6.2 with ES of 29. I've never had virgin brass do so well, not even Lapua.

Just an aberration, I guess.

In the case where it was really good, was your brass expanding .010” on the first firing? I’ve had predictably low SD’s with Virgin Alpha as well, but typically in cases where the brass is only expanding a thou or two on first firing. The new 25 x 47 brass I referenced above only expands .002” on initial firing. That chamber is cut particularly tight. As expected, the SDs were very low from the start.

 

[straightshooter1]

1.343 Alpha V.
1.353 Alpha O.F.
1.350 Hornady V.
1.353 Terminus shoulder length.

Hmmm??? Maybe it's just the particular lot of brass you happened to get? I'd get hold of Alpha and see what they and willing to do about it. If the cases are stretching that much upon firing, they probably won't last as long as expected.

I didn't have any of those issues with the .308 brass I got. Here's a comparison of measurements I've taken (V for virgin, F for fired):

 

[straightshooter1]

In the case where it was really good, was your brass expanding .010” on the first firing? I’ve had predictably low SD’s with Virgin Alpha as well, but typically in cases where the brass is only expanding a thou or two on first firing. The new 25 x 47 brass I referenced above only expands .002” on initial firing. That chamber is cut particularly tight. As expected, the SDs were very low from the start.

Yeah, you're right . . . brass expanding .010" on firing isn't going to produce such good results. I've never had that problem.

As you can tell from my chart I posted above, my virgin Alpha brass fit nicely into my chamber (a Krieger barrel).

 

[davere]

A buddy got some Alpha 25x47 brass that .003" longer than a x47 Go gauge. His chamber is .001 over a Go gauge. Guess who had to bump shoulders on his new brass? So, Alpha's definitely not above reproach - no manufacturer is.

I'm running Alpha brass in my GT, as well. My brass arrived .001" shorter than my GT go gauge, which is basically perfect. I would be interesting to see how long your virgin brass is vs. a go gauge, just for reference (like, is your brass short, or is your chamber long-ish?). Long headspace can start to look like pressure problems, because the brass gets a "running start" at the bolt face during the early part of the firing cycle. It would also be interesting to see if you have the same issue after normally resizing the 1x brass and firing it a second time (bumping shoulders .002). If that's normal, you may just have to get all the virgin stuff fired and deal with it. And then, when you spin the next barrel, send a couple fired cases (not resized) to your smith, and have him chamber to that dimension, so you can keep using the same brass.