Temp test: AR Comp vs. Varget (308 Win.) + 223 Rem

kombayotch

kombayotch

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Sep 20, 2007
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#1
Finally got my hands on a bit of AR Comp. Did a pressure work up with the Pressure Trace system with both AR Comp and Varget since I have quite a few more rounds on the barrel since the last Varget temperature test. Barrel is a 26" Barlein 5R 1-11.25 twist with a little over 7500 rounds on it.

Work up both powders and a 190 SMK in 1 gr. increments, plotted the data and put a trend line to it. The powders give the following velocities at 62,000 psi:

Varget: 2768 fps.
AR Comp: 2706 fps.

AR Comp seems to be faster buring.

I loaded them to the same velocity for the test. I just used the Varget load I was using in my 22" barrel and matched the velocity with AR Comp. It takes about 2 gr. <span style="text-decoration: line-through">more</span> less with AR Comp to get the same velocity.


Temp_test_Varget_AR_Comp.jpg


AR Comp is indeed temperature stable, twice as good as Varget (0.09 fps/F vs. 0.22 fps/F). Varget results matched my previous test results, which was with a different lot. AR Comp has nice small kernels that meter and dispense very well. I had an SD of 6 <span style="font-weight: bold">(all shots across temperature)</span> with loads dispensed from my tuned Chargemaster.

I didn't shoot any groups with this, it was all into the berm. So, I can't comment on groups, but I am going to play with this powders some more. The only thing I did notice was that a bit of a concern was that the 210M primers seemed to have trouble igniting it. There was always a noticeable delay before pressure rise in all of the traces.
 
#2
Re: Temperature test: AR Comp vs. Varget (308 Win.)

Very interesting.

Military Electronic Pressure Velocity and Action Time (EPVAT) testing normally calls for ammo to be conditioned at least two hours at ambient temperature, at -20F (+/- 5F), and at 165F (+/- 5).
 
#3
Re: Temperature test: AR Comp vs. Varget (308 Win.)

All of the ammo was conditioned for two hours at each temperatures. I could get 165F with the heating pad I used, but unfortunately, that is as cold as I could get from the icebox and fridge.

I my earlier test with Varget at those temperatures and got the same slope with this, so I'm not that worried...
 
#4
Re: Temperature test: AR Comp vs. Varget (308 Win.)

What is a tuned chargemaster?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: kombayotch</div><div class="ubbcode-body"> AR Comp has nice small kernels that meter and dispense very well. I had an SD of 6 <span style="font-weight: bold">(all shots across temperature)</span> with loads dispensed from my tuned Chargemaster.


</div></div>
 
#9
Re: Temperature test: AR Comp vs. Varget (308 Win.)

I've since tried dispensing them both in my LNL AP, in full progressive mode and AR Comp definitely meters better than Varget. Over a large number of throws (>30), all AR Comp charges fell within 0.4 gr. Most of the Varget charges were within 0.4 gr. However, Some would occasionally go way higher, opening that up to an extreme spread of 0.8 gr. or more.

There was also a noticeable difference in force required to cut a kernel. It really didn't take much to chomp and AR Comp kernel. But with Varget, there was additional needed to the point that the mouth on the case I was using for the test was completely rounded inwards by the end of it.

For comparison, I also metered some H414. It too had charges that span 0.4 gr. However, the vast majority of charges fell on one particular weight, whereas they were pretty evenly distributed between the two center values with AR Comp.

I would not hesitate to use AR Comp on a progressive to make some short range rounds for practicing snap shots and shooting off-hand. I would not do it with Varget given those occasional blips in charge weight.
 
#11
Re: Temperature test: AR Comp vs. Varget (308 Win.)

I'm going to have some data from 77 gr. SMKs and 70gr. Berger VLDs out of a 24" AR barrel in a bit.
 
#14
Re: Temperature test: AR Comp vs. Varget (308 Win.)

Powder temperature sensitivity is very important to me, and should be to every reloader. You have posted more valuable real world data on temperature sensitivity than any one person on the Hide or any other web page I have seen.

I wonder if we could bother you to take all of the work on the different powders you have tested, and make a master thread on the subject. Then talk a mod into making a sticky out of it that could be added to.

Thanks for your work,
Ty
 
#16
Re: Temperature test: AR Comp vs. Varget (308 Win.)

The markers on the graph show the three temperatures that were tested. Brass was all prepped the same way, including OAL (which btw, probably has the lowest effect of anything on consistency and accuracy).
 
#17
Re: Temperature test: AR Comp vs. Varget (308 Win.)

When you shot the powder charge at 41.0gr at 20 degree did all 5 shots record velocities around 2542fps?

Not questioning what your doing. I just agree with it and not to many people have considered that.
 
#20
Re: Temperature test: AR Comp vs. Varget (308 Win.)

SD is a function of consistency, no accuracy. The consistency of the CM is greatly improved if you add a reducer and re-tune it's parameters as described in the links above. If you wear a grounded anti-static wristband, you will prevent any drift due to static build-up, as the static charge will be dissipated each time you pick up the pan. Like the Acculab (just sold mine), it will be more consistent if powered though a UPS and left on all the time. Another trick is to observe the reading when you remove the pan, before dumping the powder into the case. If it is not -(pan weigh), dump it back in the hopper.

The 0.4 - 0.8 gr. figure is for a stock CM, without any of those modification or precautions being taken. That being said, this powder is giving me lower SDs across the board compared to any of the other powders I've been using. However, it's kernels are also much smaller, which may be a factor. I've been tempted to see if I get similar results with H322 or Benchmark, which I don't normally use. I was told that 8208 XBR also has tiny kernels...
 
#22
Re: Temperature test: AR Comp vs. Varget (308 Win.)

I've settled on 40.7 gr. for 308 Win. with a 190 SMK and the same charge weight in 303 Brit. with a 174 SMK.

Did OCW tests today in my Stag AR (24") with the 77 SMK and 70 Berger VLD:

P1060348.jpg


22.0 gr. @ ~2600 fps. looks like the node for the 77 SMK.

P1060349.jpg


23.2 gr. shows promise.

The velocities are a lot less than Alliant lists at max charge weights. But, I also have a Wylde chamber... so, I think I need to put a pressure sensor on this barrel to see where the pressure actually is.

 
#23
Re: Temperature test: AR Comp vs. Varget (308 Win.)

Worked the 70 VLD load a bit higher. Looks like there is another scatter node at 23.4 gr. 23.6 gr. produced a nice clover leaf. I would stick with 23.0 gr. as a node. There may be another one around 23.8-24.0.

Anyone else try this powder in their AR?
 
#24
Re: Temperature test: AR Comp vs. Varget (308 Win.)

It is great data. I've always been concerned the the "summer" loads I worked up with Varget would be dogs in the winter (albeit Florida winter). They have been shooting fine, and now I can see I should never have worried.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: fireguyty</div><div class="ubbcode-body">Powder temperature sensitivity is very important to me, and should be to every reloader. You have posted more valuable real world data on temperature sensitivity than any one person on the Hide or any other web page I have seen.

I wonder if we could bother you to take all of the work on the different powders you have tested, and make a master thread on the subject. Then talk a mod into making a sticky out of it that could be added to.

Thanks for your work,
Ty </div></div>
 
#26
Re: Temperature test: AR Comp vs. Varget (308 Win.)

Pushed the load up a bit more yesterday. It took more than a grain of powder to get up to the velocities Alliant is listing.

P1060376.jpg

<span style="font-style: italic">***should read 70 Berger VLD</span>

Again, a scatter node showed up at 23.4 gr.
I'm liking 24.4 gr. for the next node.


Here is a plot of the velocity data I've accumulated to date:

70_VDL_ARCOMP_VEL.jpg
 
#31
Re: Temperature test: AR Comp vs. Varget (308 Win.)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: X-fan</div><div class="ubbcode-body">Does the 77 normally open up more vertical at distance as compared to the Berger?
I have never bothered to try it at distance, but a pointing die looks like it would do wonders to ballistic QC?

Looks like another shooter BTW

Peace </div></div>

I still haven't tried them at distance. The 77 SMKs have kind of fallen off in interest since the 70 VLDs shoot so well. They have the same BC and can be driven 200 fps. faster. I was also just "borrowing" a few of the 77's from a friend...

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MALLARD</div><div class="ubbcode-body">how did the change in temp effect your exit times ? The CCI BR4's im using cause delay as well. </div></div>

Not following what you mean... ?
 
#32
Re: Temperature test: AR Comp vs. Varget (308 Win.)

I doesn't look to me like you've reached your pressure limit yet. Your last load was 23 fps faster than the one before it. I would keep going up until velocities leveled off.
 
#34
Re: Temperature test: AR Comp vs. Varget (308 Win.)

Pushed the 77 SMK load up a little higher.

P1060399.jpg


The fouler group is the lower node. I believe that the scatter node is between 22.5 and 22.7. The groups for 23.1 and 23.3 are definitely in the OCW range as their positions are the same and also the same as the lower node, only shifted a little higher due to higher velocity. Groups for 22.9 and 23.5 are both starting to shift. I would chose 23.2 as the OCW, I think I would again have three groups in the same location if I had went 0.1 gr higher on the charge weights. The interpolated velocity for 23.2 is 2778 fps.


My velocity vs. charge data for the 77 SMK:

Image1.jpg
 
#37
Re: Temperature test: AR Comp vs. Varget (308 Win.)

Haven't run any loads with Varget in this rifle. Given similar burn rates, the OCW nodes will be at similar velocities. Maximum velocity attainable may be different, but I don't load to that.

The intent of switching to AR Comp was to have a temperature stable powder that meters well enough for running ammo through the progressive press when I want to make a lot of practice ammo in a pinch. AR Comp fits the bill and has shown to offer other advantages as well.

The 24.4 gr. 70 VLD load is holding under 2" at 300 yards with 10 shot groups. I'll be developing some 55 gr. loads with AR Comp next.
 
#38
Re: Temperature test: AR Comp vs. Varget (308 Win.)

kombayotch,

Lately I've been working up OCW charges in the small cases (223 6mmbr etc) in 0.1 grain increments and getting clear scatter patterns and a bit more load tuning info at the same time.

Twice as many shots, but it has been working for me.
You ever try that?
 
#40
Re: Temp test: AR Comp vs. Varget (308 Win.) + 223 Rem

That is awesome, I load a lot of varget in my AR's and always wondered about the temperature stability of it as well as other "Extreme" powders.

You don't by chance have any information on H1000?
 
#43
Re: Temp test: AR Comp vs. Varget (308 Win.) + 223 Rem

No, but keep in mind that I have a Wylde chamber, therefore I can go a little higher than I would be able to with a regular .223 chamber due to the added capacity.

I didn't go any further because the case was already as full as I would want for running the load on the progressive. I wouldn't be able to hit the next node without having a compressed load even if I could hit it before pressure signs showed up.
 
#45
Re: Temp test: AR Comp vs. Varget (308 Win.) + 223 Rem

I wonder how close the burn rate is on AR Comp compared to RL-15. I run a lot of RL-15 but wish it was a bit more temp stable. I'll have to try some AR comp.

Bb
 
#46
Re: Temp test: AR Comp vs. Varget (308 Win.) + 223 Rem

Well, I tested AR Comp with Hornady 55 gr. FMJ and Remington UMC 55 gr. FMJ. Velocities weren't great and accuracy was terrible (~3 MOAish). Remington 55 gr. UMC ammo shoots amazingly well though... But the Winchester and Federal ball ammo doesn't.

Still searching for a load that is at least as good as the UMC ammo. Didn't have have much luck with H335.
 
#47
Re: Temp test: AR Comp vs. Varget (308 Win.) + 223 Rem

I think you are going to find it's the bullet, not the powder causing accuracy problems.

Winchester and Remington bullets that are sold as componets are slightly undersized, different from the ones they sell in their loaded ammo. .3075 for the Winchester Power Point .30 cal bullets, .3075 for Remington CoreLokt .30 cal bullets.

I haven't measured the .223 bullets.

I think they do this to minimize their liability foot-print, keeping someone from blowing up their firearm.
 
#48
Re: Temp test: AR Comp vs. Varget (308 Win.) + 223 Rem

Possibly... I have a bit of trouble seeing them sorting bullets or running different lines from a cost point of view. Segregating lots would be more likely.

Not seeing any better performance from the Hoarnadys though.
 
#49
Re: Temp test: AR Comp vs. Varget (308 Win.) + 223 Rem

True enough with the Hornadys too. For military ball ammo, the group had to be within 3 min @ 100 yds. Ball ammo isn't normally known for accuracy.

If you've found factory ammo that does, go buy it.

Try the Remington 60gr flatbase bullets, some of my friends swear by them out to 300 yds though I've never shot them. I've seen some pretty impressive scores posted with them tho.
 
#50
Re: Temp test: AR Comp vs. Varget (308 Win.) + 223 Rem

Isn't just one lot of UMC 55 gr. that is shooting well for me, every lot I've tried has. Powder looks like H335, but is slightly faster. No doubt a canister powder though. I'm going to try Benchmark. I've heard good things and rumor is that Hornady loads it in their 55 FMJ-WC ammo.
 
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