AIAE OCW test results

[powereng]

Just wanted to run my OCW test by some of you guys to confirm that I'm reading the results correctly.

Rifle: AIAE MKIII, 308, 20" barrel w/ muzzle break.

Brass: Federal GMM, once fired
Powder: Varget
Primer: CCI BR-2
Bullet: 175gr SMK's
Headspace: 1.558"
COAL: 2.130" (.020" Jump)

I started at 42.0gr of Varget and went up to 45.0gr in .3gr increments. I used 42.0, 42.3, 42.6, 42.9 as fouling shots and started my OCW test from there.

From with I can gather, 43.2 would be my low node, 44.1 would be my scatter node, and somewhere between 44.7 & 45.0 would be my optimal node. I didn't see any pressure signs at 45.0 but I didn't make any loads past book max. Although I love the group at 43.2 I read not to chase tight groups but rather similar groups.

For reference, the yellow label is 2.75" long. Any yes, there are 3 shots at 43.2 & 45.0. Let me know what you think. Thanks.

 

[Dan Newberry]

I'd probably stick with the 43 grain area. 43.2 is likely the top of that node, as you begin to spread out a bit at 43.5.

You might find that 43.0 would have you deep into that 43 grain area node.

I wouldn't run it above 43 grains, as Federal brass is not going to like being pushed that hard. It's decent brass if you don't hammer it to death.

Good test... thanks for sharing your info.

Dan

 

[powereng]

Thanks Dan, I'm going to run the test again, this time focusing more on lower end of the charge weights. I just always see Varget recipes in the 44.0 to 45.0 weight range, so I assumed thats where mine would fall.

I hear you on the Federal brass, but thats all I have until some Winchester brass starts to become available again. Thanks again.

 

[dustinoif3]

What's max charge for your setup? I was curious if 45.3 would still be in the node and have the same poi. Oh and not to hijack but thank you Dan for your website and method! Good stuff

 

[timelinex]

Thanks Dan, I'm going to run the test again, this time focusing more on lower end of the charge weights. I just always see Varget recipes in the 44.0 to 45.0 weight range, so I assumed thats where mine would fall.

I hear you on the Federal brass, but thats all I have until some Winchester brass starts to become available again. Thanks again.

Many people, including myself, have their recipes in that range, however that's with winchester brass. Winchester brass fits the most, without pressure issues. I'm surprised you didn't run into serious pressure issues at 45, that's a really hot load even for winchester brass.

 

[Dan Newberry]

Timelinex... I agree 100 percent with the amazement that there were no pressure signs at 45 grain in FC brass... whoa.

 

[Graham]

I shoot 45 Varget and a 180 JLK VLD in Lapua brass. I haven't met an AE that didn't like it.

 

[powereng]

I was keeping a real close eye on brass and primers the whole time. Trust me, after my GAP-10 experience, I know what to look for.

I did load up some 45.3's last night for my next test, but maybe I'll just go ahead and pull those. Thanks for all the input.

 

[powereng]

Update

I've been working to perfect my load for my AE MKIII and thought I'd share some more of my results. After Dan told me to concentrate on more toward the lower end of my original OCW test, I ran a second OCW test using charges between 42.0 and 44.1gr seen in the pic with the yellow label. This led me to a good node of around 42.9gr.

Today I ran another OCW test, this time using 0.1gr increments around the 43.0gr node seen in pic with the green label. Once again 42.9gr seemed to be the magic number.

Up until this point I've using nothing but Federal brass for my testing due to quantity on hand. Since I would someday like to switch over to Winchester brass, I decided to run the same OCW test using the little Winchester brass I have on hand. My hope was that I wouldn't have to start my testing all over again once I got my hands on a larger quantity of Win brass, and to see if brass affected my accuracy node. I did changed out my die neck bushing from .336 for the Federal brass to a .332 bushing for the Winchester brass, to keep the same .002 neck tension on the bullet.

I found that changing out the brass did cause a POI shift to the right. However to my surprise, changing out the brass also cause my groups to shrink slightly and my accuracy node to stay the same at 42.9gr. Results are the pic with the pink label.

I started by taking 5 fouling shots using FGMM ammo and then started with test with the Fed Brass and then moved onto the Win brass. Each shot was taken within 30 seconds of the previous shot. The barrel was quite warm when I finished, but with no negative results to accuracy.

Let me know what your thoughts are.

 

[Graham]

Switching brass shouldn't have a noticeable effect on the windage of your groups at 100 yards.
Your zero is probably changing because you are shooting the rifle more.

 

[Dan Newberry]

Great test, I think you've found where you want to be.

I would have guessed the Win cases would have wanted a touch more powder than the FC cases, but maybe the neck tension difference brought them together... can't argue with those results, for sure.

Annealing the Federal brass will help it a lot. It seems like the FC brass alloy just work hardens earlier than other brands... but it's useable brass, which has gotten a whole lot better in recent years.

Thanks for sharing your results.

Dan

 

[Rprecision]

Just wanted to run my OCW test by some of you guys to confirm that I'm reading the results correctly.

Rifle: AIAE MKIII, 308, 20" barrel w/ muzzle break.

Brass: Federal GMM, once fired
Powder: Varget
Primer: CCI BR-2
Bullet: 175gr SMK's
Headspace: 1.558"
COAL: 2.130" (.020" Jump)

I started at 42.0gr of Varget and went up to 45.0gr in .3gr increments. I used 42.0, 42.3, 42.6, 42.9 as fouling shots and started my OCW test from there.

From with I can gather, 43.2 would be my low node, 44.1 would be my scatter node, and somewhere between 44.7 & 45.0 would be my optimal node. I didn't see any pressure signs at 45.0 but I didn't make any loads past book max. Although I love the group at 43.2 I read not to chase tight groups but rather similar groups.

For reference, the yellow label is 2.75" long. Any yes, there are 3 shots at 43.2 & 45.0. Let me know what you think. Thanks.

Heres from my test, seems like we both found the same thing !

So until today I had not developed a load for my AIAE Mk III. I am running the AINA 1/10 18” Barrel.

I had some .308 loads worked up for a different rifle, which worked ok with 1-moa’ish results. In the mayhem of reloading scarcity I picked up a few boxes of FGMM 175 loads which shot 3/8 MOA. This motivated my load development.

On to the test,

175SMK
Varget 42.3-45.0
Hornady match once fired brass, FL Sized, Trimmed, Prepped
FGMM LR Primer’s
COAL 2.800”





I am new to interpreting OCW results as a new user. I was impressed the entire range of loads shot within MOA mostly.

I hit some pressure signs at 44.4 concluding with a sticky bolt on 45.0. Although I wish the 45.0 load would have worked, as it was basically a dead ringer and probably has some good velocity behind it.

From 42.6 to 43.8 all shot very similar minus the round I pulled. Although 42.9 and 43.5 trend left POI. 42.6 shot identical to the FGMM 175 but were too close on the low side to 42.3 which scattered. I am inclined to interpret the results as loading to 43.0 grains (to make it easy) would be a pressure tolerant load. That gives enough change from 42.6-43.8 to fall in the same accuracy realm.

I have other head stamps, which will be used in the future such as Winchester (WIN) and a gaggle of once fired Federal (FC). What is the best way to pick a load which should work across the spectrum?

Thanks

 

[powereng]

Rprecision - since my post I have had to change my loads for my AE MKIII. I changed out the factory AI muzzle break with a Thunderbeast muzzle break to accommodate my future suppressor. The Thunderbeast muzzle break completely changed the harmonics of my barrel and screwed up my original accuracy node for 42.9 grains. When I re-did my OCW test with the Thunderbeast muzzle break I found that 42.6 grains was the only charge weight that would produce decent 5 shot groups. Speeds where around 2485 to 2500 FPS. With the AI break I could shoot 1/4" to 3/8" moa groups no problems. With the Thunderbeast break I struggle to shoot 3/8" moa groups. I guess there is a price to pay for wanting to run a suppressor.

For kicks I tried some FED 215M (Magnum) primers I had laying around with the same 42.6gr charge weight. Speeds with the 215M's where about 10FPS faster than the CCI BR-2's. Groups at 100 meters where outstanding, however at 200 meters the wheels fell off the bus for some reason.

 

[timelinex]

Rprecision - since my post I have had to change my loads for my AE MKIII. I changed out the factory AI muzzle break with a Thunderbeast muzzle break to accommodate my future suppressor. The Thunderbeast muzzle break completely changed the harmonics of my barrel and screwed up my original accuracy node for 42.9 grains. When I re-did my OCW test with the Thunderbeast muzzle break I found that 42.6 grains was the only charge weight that would produce decent 5 shot groups. Speeds where around 2485 to 2500 FPS. With the AI break I could shoot 1/4" to 3/8" moa groups no problems. With the Thunderbeast break I struggle to shoot 3/8" moa groups. I guess there is a price to pay for wanting to run a suppressor.

For kicks I tried some FED 215M (Magnum) primers I had laying around with the same 42.6gr charge weight. Speeds with the 215M's where about 10FPS faster than the CCI BR-2's. Groups at 100 meters where outstanding, however at 200 meters the wheels fell off the bus for some reason.

I'm surprised it affected your nose and accuracy by that much. Did you screw it in and line it up right? I just switched up both my factory brakes on 308 and 338 and it had no effect on accuracy, and I didn't need to change the load at all. While theoretically everything you do to a rifle changes the harmonics, in reality I think it's a consensus that as long as you are in an actual node, little things like that usually don't effect the accuracy and don't no new work up is needed.

 

[powereng]

I'm surprised it affected your nose and accuracy by that much. Did you screw it in and line it up right? I just switched up both my factory brakes on 308 and 338 and it had no effect on accuracy, and I didn't need to change the load at all. While theoretically everything you do to a rifle changes the harmonics, in reality I think it's a consensus that as long as you are in an actual node, little things like that usually don't effect the accuracy and don't no new work up is needed.

The top of the Thunderbeast muzzle break is flat so I used two small levels to level to the top of the break to the top of the scope base. A used a peel washer to time the muzzle break. If you have a better idea, I'm all ears. Thanks.

 

[timelinex]

The top of the Thunderbeast muzzle break is flat so I used two small levels to level to the top of the break to the top of the scope base. A used a peel washer to time the muzzle break. If you have a better idea, I'm all ears. Thanks.

Nope, that's exactly what I did.

 

[Rprecision]

Rprecision - since my post I have had to change my loads for my AE MKIII. I changed out the factory AI muzzle break with a Thunderbeast muzzle break to accommodate my future suppressor. The Thunderbeast muzzle break completely changed the harmonics of my barrel and screwed up my original accuracy node for 42.9 grains. When I re-did my OCW test with the Thunderbeast muzzle break I found that 42.6 grains was the only charge weight that would produce decent 5 shot groups. Speeds where around 2485 to 2500 FPS. With the AI break I could shoot 1/4" to 3/8" moa groups no problems. With the Thunderbeast break I struggle to shoot 3/8" moa groups. I guess there is a price to pay for wanting to run a suppressor.

For kicks I tried some FED 215M (Magnum) primers I had laying around with the same 42.6gr charge weight. Speeds with the 215M's where about 10FPS faster than the CCI BR-2's. Groups at 100 meters where outstanding, however at 200 meters the wheels fell off the bus for some reason.

Well that kind of sucks,

I did all my testing with a can, but I wouldn't think just a muzzle brake would throw things off that much.