X-Terminator 223 53gr load velocity seems lower than expected

[BobbyJ]

I just built a 24" AR and bought 4 pounds of X-terminator (aka AA 2230) And I did a quick three shot ladder from 23.50gr to max of 26.0 gr. The max load for 53gr Vmax was like 26.3 (Nato) for X-terminator in the Western reloaders book.

I bought Hornady Factory 53gr to see what it shot at for a baseline. It was 3360 fps out of my 24" 81 degrees outside.
I think the box said 3450fps so I was in the ballpark velocity wise.

Today I tried X-terminator and the velocities are a bit lower than expected could it be just a lot variability where my lot is 10 percent weaker?

Gun - Aero Enhanced Upper with Improved National Match AR-15 Bull Accuracy Barrel by EABCO - 24" Stainless Fluted 5.56 NATO/.223 Rem (Wylde) 1:9 Varmint Barrel
Brass - New Starline
Primer - CCI 41
Loaded on Dillon XL 650
53gr Vmax OAL 2.245

53gr Vmax X-terminator
23.0 - 2896 (SD 13 ES 33)
24.0 - 2977 (SD 29 ES 71)
24.5 - 3050 (SD 33 ES 75)
25.0 - chrono disconnected
25.5 - 3180 (SD 16 ES 40)
26.0 - 3244 (SD 8 ES 18)
=======================
Factory 53gr 3360 fps
==================================
55gr FMJ CFE 27.4 gr 3117 fps
========================

All the loads shot about the same. All under 1 MOA .6 to .8 range. Really could not see any nodes. Maybe there is but I would need to get my lead sled out. Most of the variability was me with a not so steady rest.
The power did no fill case till around 25.5 gr, could shake the rounds and feel the powder moving on 25gr and less. The SD and ES seem to be better with a full case.

Looking at Western powders book
53gr - 24.8 = 3295
Mine - 24.5gr = 3050 fps (almost 250 fps less)
Nato loads for 55gr are 26.3 gr at 3452 fps mine using 26.0 gr + lighter 53gr was 3244 or 200+ fps lower than expected.

Since the accuracy is the same with any of the loads I tried I wanted to try to get 3300-3350 fps. But that probably would mean 26.5 grains which is over book. I'm thinking the pressures listed in Western Power load book are higher than my pressures. Possibly due to my lot of powder. Was hoping I could match the Hornady factory.

Do the Lots vary that much? 26.3 is max book load. Doubt I will even get to 3300 fps with 26.3gr.

 

[Beiruty]

I modeled your AR and the gas port should be 11.17" away from the bolt face to match your MVs
Here is the simulation with 26gr of X-Terminator

 

[ASD9055]

I modeled your AR and the gas port should be 11.17" away from the bolt face to match your MVs
Here is the simulation with 26gr of X-Terminator

View attachment 1364635

I am trying to learn GRT, so this is for my education. The note in GRT gas leakage says " it is NOT for gas ports for cycling action". Shouldn't you try and match the velocity in another method? (But that would require several MV measurements at same powder load)

 

[Coyotefurharvester]

Pay attention to how the primers seat in the Hornady brass when you process them, I doubt they will feel like new brass. I looked at the Hodgdon data, probably won't be able to get to the Hornady velocity, especially out of a AR. If you can get bugholes, at 3200 or slightly under run with it(the prairie dogs won't care).

 

[Beiruty]

I am trying to learn GRT, so this is for my education. The note in GRT gas leakage says " it is NOT for gas ports for cycling action". Shouldn't you try and match the velocity in another method? (But that would require several MV measurements at same powder load)

Yes, you can tune the powder model or initial pressure (primer output) or other parameters. I suspect that the published data is for bolt action rifles and not Semi-auto. Semi-auto would lose pressure behind the bullet, hence lower MVs.

 

[BobbyJ]

Pay attention to how the primers seat in the Hornady brass when you process them, I doubt they will feel like new brass. I looked at the Hodgdon data, probably won't be able to get to the Hornady velocity, especially out of a AR. If you can get bugholes, at 3200 or slightly under run with it(the prairie dogs won't care).

I was just shooting for what I know i will shoot the 53gr at using factory ammo. 3360fps.

I know the same ammo in different guns will shoot at different velocities. Like my old 1980s colt shoots around 100 fps slower than out of my newer 6820s with the same ammo.

But in this case I have known ammo shooting at a known velocity and I was simply trying to match that velocity and came up far shorter than expected based on various reloading sources.

That factory ammo is suppose to be loaded at 223 specs not NATO so it should be ever easier to match since my AR is above standard 223 specs.

I'm just trying to figure out why as a learning experience.
- Could be my 26gr was really 24gr. My scales would have to be way off.
- Could be my X-terminator burn rate was slower than what the loading books state. This is more difficult to check since I only have one source of X-terminator powder one lot number.
- Could be my chamber just won't allow those speeds of 3360 fps with a 53gr. This is easily dispelled by the fact I can buy off the shelf 223 53gr VMax that shoots that out of my AR.

Wonder what powder hornady uses to get that velocity. I matched the seating, bullets, but used CCI 41s. I only use CCI 41, 450 or Rem 71/2 in ARs. Not sure what Hornday uses in the factory but it has to in 223 pressure specs and they show no pressure signs.

 

[BobbyJ]

I modeled your AR and the gas port should be 11.17" away from the bolt face to match your MVs
Here is the simulation with 26gr of X-Terminator

View attachment 1364635

Thanks for the nice sim! Have to check that program out. I use Quick Load which is a fun tool but its pressure curves are not all the accurate or can be fully trusted vs real world.

Garbadge in garbadge out. I question the real burn rate of my Powder Lot. I've done quite a bit of reloading and I'm usually really good at nailing a velocity if I have enough data. I've not had any WOW that was not as I expected with any of my reloads until this exterminator batch. Its much weaker than expected on all loads. If I had a real pressure gauge I could get more info.

ie 27.4gr cfe 223 should be around 3200 fps according to the books in a 24". And well I get 3120 or so. 80 fps low but in the ballpark.

For 69-70 gr bullets and 25.6 gr CFE Expected was 2900fps and I got 2890fps so very close.

But on X-terminator the book says 53gr 24.8 = 3,295
Me using 25.5gr (3,180) so .7 gr more powder to get 115 fps less
and even 26.0 gr still can't match the 24.8gr book load velocity. sill 56 fps less.

I'm thinking this lot of power is just not the same as what they used for the book. Its a different burn rate. Or my Chrono is way off (But it shows higher velocities with factory ammo)

The good news is the gun is not picky about ammo or loads. It will shoot anything sub MOA. I will probably load to 26.3 or 26.5 and call it good. I don't see any pressure sings.

Have any of you have a really weak powder lot where you had to adjust previous loads by 1gr or so to match you previous same powder load velocities?

It must be common as it says this. Results caused by ± 5% powder lot-to-lot burning rate variation using nominal charge. 5 percent of 25 is 1.25 grains.
Which is around how far off the book data is from my loads.

I think maybe I have just gotton lucky that all my previous powders H110, Siloutte, win244, CFE 223 were all very close to published load results. Was just a matter of time till I hit a 5 percent weak lot.

 

[BobbyJ]

Yes, you can tune the powder model or initial pressure (primer output) or other parameters. I suspect that the published data is for bolt action rifles and not Semi-auto. Semi-auto would lose pressure behind the bullet, hence lower MVs.

I wondered the same. Turns out that its not that much. 8 to 28 fps loss due to a port wide open. Western Powders does publish NATO AR loads which is a nice addition. So the loss in my case is most likely (At this point) due to lot to lot 5 percent variance. My Pressures at 26gr are likely lower than what the published pressures were.

I've not tested the hornady Factory out of a bolt. It should get around 3450 fps. Mines was 3360fps. The loss over box might be due to barrel friction, Wylde chamber not as tight as Hornady 223 test chamber (Likely)
I've looked around a little but I have not seen anyone else even chrono the Factory 53gr from a 24" bolt or AR.

Hornady claims 3465 fps out of a 24" test barrel (probably 1/12)
Subtractions
-30 fps for 1/9 twist vs test 1/12
-30 fps for gas port
-30 fps for Wylde chamber vs tight .223 for hornady test
-15 fps because hornady choose a hotter lot for testing and boxing

3465 fps -105 = 3360 fps (real world) out of my 24" using Hornady Superformance 53gr Vmax
but ...
- 116 fps for Xterminator 5 percent low lot where 26gr acts like a 24.6 gr load.
3360 fps - 116 = 3244 fps from my 24' using 26gr X-terminator.

So I am taking all that into account and was trying to match the 3360 fps not the box label that says 3465 fps.

They have a special powder (super top secret) that I don't have.

I could probably do it but I would have to assume that 27 gr of this lot of X-terminator = the pressure of 26gr of book load data for the lot they used.

I'm not willing to assume that just yet. So I will load it to the max book of 26.3 see how it shoots then call it good for this 4 pound lot.

 

[Beiruty]

How far the gas port is from the Muzzle?

 

[BobbyJ]

How far the gas port is from the Muzzle?

Its a standard rifle length gas system. But on a 24" instead of a 20" barrel. So a bit more dwell time. Works well with a h2 buffer. A variable gas system might allow more dialing in recoil wise.
Distance from port to muzzle is around 10.25-10.50"