308 Test With Small Base And Full Length Dies

[BigBoreBubba]

So a few weeks ago I finally got around to working up some test loads for my AR-10. I bought a set of small base does to load with, and I also had a set of full length that I figured I’d work up a few loads with. I already had it set in my mind that the small base set was what I would settle on using, simply for feeding reliably. But I figured “what the heck” I might as well load a few with the FL sizer just to see if they would cycle.
I loaded Hornady 155gr HPBT’s over H335. With the SB dies, I loaded four sets of rounds (5 each) starting at 41.0 and ending at 43.0. With the FL sized brass, I loaded three sets of rounds (4 each because I ran out of cleaned and trimmed brass) starting at 41.7 and ending at 43.0. I also used the taper crimp die from the SB set on these, as I wanted all other variables the same.

Now before I get into my results, let me give you a little info on the rifle, and how it usually performs. I built the gun a year or so ago. It’s got a Ballistic Advantage 5R heavy barrel with a large muzzle brake, Atlas Bi-pod, an Elftman 3 pound trigger, Aero Precision upper and lower receivers, and it’s topped off with a Vortex Viper 6-24x50.

Up to this point in its life, it’s only had factory ammo ran through it. It normally shoots around MOA with good ammo such as Norma.

Now onto the results. I started out with the small base loadings. The results were, shall we say, less than stellar…. About a 2” group was the best I could muster. At first I thought that I might have been having one of my (all to common these days) bad days. But I was taking my time, getting good trigger breaks, timing my shots between breaths, and I felt certain that they were good shots. I had even fired 5 factory rounds to warm the barrel up before the test loads, and let the barrel cool enough to maintain a steady temperature between groups. Needless to say, I was not impressed.
Then I switched to the full length sized, taper crimped loads….. WOW! The worst group I had was about 1”, and the best…… just over 1/2”! That is the best this gun has ever shot! I simply couldn’t believe the difference. Not only that, but they all cycled perfectly.
Needless to say, I will not be using the small base sizer again.
I also have a set of small base dies for 223/5.56 that I haven’t used yet, and don’t know if I ever will.

What are your experiences with different styles of dies?

 

[bluejay75]

A crimped bottleneck cartridge will never break a bench rest record but it turns out some very consistent ammunition.

I just purchased the 6.5 Creedmoor SB set just for the taper crimp.

I surmise that a tiny bit to moderate crimp normalizes the differences in not so perfect neck tension. But I’m in the minority on crimping.

 

[BigBoreBubba]

A crimped bottleneck cartridge will never break a bench rest record but it turns out some very consistent ammunition.

I just purchased the 6.5 Creedmoor SB set just for the taper crimp.

I surmise that a tiny bit to moderate crimp normalizes the differences in not so perfect neck tension. But I’m in the minority on crimping.

Yeah, I didn’t put a very heavy crimp on them. The only reason I crimped at all, wel two reasons really, is that they were to be fired in an auto loader from a magazine, and because it was mixed brass. Pretty much a guarantee to have slightly different neck tension with mixed brass.

 

[Dale Alan]

Did you use mixed brass randomly or were 5 shot groups all same headstamp ?

 

[BigBoreBubba]

Did you use mixed brass randomly or were 5 shot groups all same headstamp ?

Mostly random. I think a couple groups ended up being same headstamps.

 

[Dale Alan]

OK, I was just curious . I am wondering how much same headstamp/internal volume played a role , if they turned out to be the better groups ? I use SB dies for some rifles and have never done a side by side with other dies . Interesting experiment .

 

[BigBoreBubba]

If I were loading “serious” match grade ammo I would definitely use only one headstamp. I was really just hoping for a good MOA plinking load. I do think the last two groups I shot happened to be all Federal brass, but I don’t know if that was enough to make that big of a difference.

 

[Blue68f100]

I only crimp ammo for tubular magazine feed. All of my AR ammo is not crimped. I do run 0.002-0.003" neck tension on my ammo for AR's.

Using all same head stamp brass can make a big difference. I load for a lot of simi auto and have never needed a SB die, including Browning's BAR's from the 70's. The std die will be easier on the brass, too.

 

[FROGO207]

For my 308. First I do not crimp those either. I do chamfer the inside of the mouths first loading and after trimming. I anneal after every 3 times. I had to get a SB sizer to size down 2K 7.62X51 brass that had been run through a machine gun when I first got it so it would chamber. After that I full length sized my brass with the Lee die that was stock. It ran without a hiccup. When worked up all my ammo was better than MOA with ease. Some bullet weights were better than half MOA. Sounds like we got similar results. They make a SB die for a reason and it is good for that. I had to try both crimped and not crimped with identical ammo to make my decision clear.

 

[jmorris]

The only set of small base dies I have were given to me. If I have a rifle that will not work without special “under” ammunition, I fix the rifle.

 

[The Glockodile]

Hold on to your dies...

It's possible that you may need them in the future, possible that you wouldn't.

There's a lot of inter - part, inter - rifle variation when it comes to ARs "in the wild."

This isn't an Accuracy International barrel and chassis, wherein what you mix and match today probably won't be out of spec with something you mixed and matched the following year...

 

[Dale Alan]

Many uses for SB dies . Not all rifles that require them need "Fixing " . One use is preventing "clickers" in competition rifles ...resizing range brass, etc . . Handy dies to have .

 

[Bayou52]

Interesting. By contrast, I only use RCBS 308 SB rifle sizing dies. Seating depth is 15 thousandths off the lands. Absolutely no crimp. Out of a Weatherby Meateater, 100 yard cloverleafs are common. Our range does not go beyond 100 yards…

Bayou52

 

[cfullgraf]

I do not crimp my ammunition used in semi-auto rifles, AR-15, M1A, and M1 Garands.

I have found reloaded cases fired in the same semi-auto gun as they were originally fired in, standard sizing dies will work fine.

If the reloaded cases were fired in a different semi-auto rifle, you may have chambering problems in the second rifle.

The risk is very low but a combination of a slightly larger chamber and a slightly smaller chamber and a sizing die near the large end of specifications can cause chambering problems with the cases.

And, most case gauges, except maybe a Sheridan gauge, will not catch the problem.

Out of hand, for all cartridges I load for semi-auto rifles, I use small base sizing dies if available. I find no loss in case life and no difference in accuracy. Maybe the latter is the case because I work up loads using the small base sized cases and dial in an accurate loading.

What I recommend, if you start with new factory ammunition or buy new cases to generate cases for reloaded ammunition for your rifle, standard sizing dies will work well.

If you plan to buy once fired cases or use range pick up cases, use a small base sizing die. Cheap insurance against chambering problems.

I have a Colt Match Target with a 5.56 NATO chamber. Ammunition shot in the Colt and the cases resized in one particular standard sizing die I have would not chamber in three different AR-15's built for Service Rifle Competition.

 

[Blue68f100]

Something I learned years ago when dealing with brass that does not want to size properly, was to anneal it. This works for rounds fired in a MG, too. Once annealed it removes the spring back and will size easily and will be in spec.

 

[BigBoreBubba]

Some good advice guys. Most of my cases have been fired out of my gun. Some were fired out of my buddy’s Bergara (which is soon to be mine), and a few were range pick ups. The taper crimp I applied was very mild. I have about 50 more that I worked up for my range trip this Thursday. I will try to separate them by headstamps and group them.
I have them all loaded at 42.4 gr. That’s actually 4 shots in that group, just looks like 3.

 

[JFrank]

Some combos just like more Bullet hold / neck tension, it can make a great deal of difference on paper on the other hand i have not seen any difference on paper with just a die change other than the lack of clickers / heavy bolt lift causing a rifle to get upset in the bags leading tracking delays and condition changes.

 

[BigAlShooter]

I've never used a SB die, but I use RCBS competition FL die. I set it up to barely push back the shoulder on once fired brass only from this rifle - DPMS LR-308 24" bull barrel. Factory ammo will be 1.5". Then, the reloads will be much less, depending on bullet and powder. It likes Sierra and Nosler bullets and IMR4895 and 4064 powders. Crimping doesn't seem to affect anything, sometimes I crimp, sometimes I don't. I always trim, which usually takes a decent amount of brass off. If I do my part, I can get half inch at 100 yards.

 

[GW Staar]

If you've ever used Dillon .223 or .308 dies, you've used small-base dies. Unless they've changed there methods the last few years. According to them (a printed reply to the question on their forum), that's all they make in bottleneck rifle sets. I'd like to hear of a study with a little more control over components.....IOW's apples to apples....same brass, same primers, same bullets, same powder charge.

 

[lordpaxman]

I’ve only FL sized bottleneck cartridges, but I wouldn’t think all other factors being equal an SB would be a factor.
In addition to @GW Staar ’s recommendations, I would have a tendency to measure how much sizing you’re doing with those two different dies. Shoulder bump and neck expansion in particular.
Accuracy tests with mixed HS brass are interesting but inconclusive. Even single HS bass should be from the same lot. Good luck.