Powder and Malfunction Observations

General Firearms Reloading & Ammunition
1

I tested two reloads, and some factory ammunition, using two AR-15 rifles with 20" barrels. Charge weights for both reloads were in the middle of the recommended range.

One rifle, a Colt HBAR, and the second rifle, a Delton, both with 20" barrels were used.

First reload = 19.6g IMR4198 + 55g FMJ + WSR Primer @ 2.200" C.O.L.
Average Velocity = 2,848 fps, the rifle ejected the empty brass, yet failed to pick up the next cartridge out of the magazine.

Second reload = 25.0g Varget + 55g FMJ + WSR Primer @ 2.200" C.O.L.
Average Velocity = 2, 771 fps, which is 77 fps slower than the IMR 4198 reload.
The rifles functioned 100%, with reliable ejection and feeding.

The reload with 77 fps slower velocity functioned 100%.

This will give the engineering types something to keep them occupied. I suspect that Varget is a slower burning powder and maintains chamber pressure longer than IMR4198, thus cycled the actions of both rifles reliably. Varget is # 113 and IMR 4198 is # 79 on the 2024 Hodgdon powder burn rate chart.

A side note, the RRA carbine with mid length gas system and Stag Arms carbine with carbine length gas system both run 100% with the IMR 4198 reload. Accuracy at 100 yards is acceptable with both carbines.

2

I believe they call that gas volume but I’ll stay in my lane.

3

Gas volume. Extra velocity, in itself, doesn’t increase gas drive. It even reduces the amount of time that the port is pressurized. Consider that a starting load of CFE223 or BLC2 will give a poor velocity, large extreme spread and SD, and cycle pretty much any gun in good condition. They’re slow, gassy powders that start around 25 grains, and on the top end they make really good velocities. But some .223 appropriate powders aren’t really a good choice with autoloaders. The ones that I can think of that suck are faster burning ones with lower charge weights

4

I’ve run CFE223 and BLC2 in the past with acceptable results. I had some IMR4198 on hand and used it to load training ammunition.

For High Power Rifle Match loads, my go to powder is Varget regardless of bullet weight.

5

Those velocities are so slow for a 55 gr FMJ in a 20" barrel, that I wouldn’t put too much stock into the results.

Being that M193 is over 3200 fps, I try to confirm load functions at 2950-3150 to stay in the middle of the fairway.

Just my .02

6

I’ll also add- Try to bump up the 4198 load by a half grain. You woud still be under the listed max load of 20.4.

7

I agree that increasing the IMR 4198 charge weight 0.5 grains might make the rifles function correctly. Under 2,850 fps for both rifles is in the accuracy node for any bullet weight.

I’ll just burn IMR 4198 in my carbines for short range use (under 200 yards) and use Varget for accuracy loads in carbines and rifles.

The gist of the original post is that higher muzzle velocity does not equate to reliable function.

8

Yeah, I’m not necessarily suggesting those powders (CFE and BLC2), just using them as an example of when velocity vs function flip the other way. Though I do like them for bulk loads.

10

For sure. I used to run a low velocity TAC & 55gr FMJ load that ran silly good. But when we started shooting longer distances, I evolved into heavier bullets going faster.