H335 223 Too Hot?

[Schuyshot]

I know I know, another is hot-rod load question...

Worked my way up to 27.0 grains of H335 under a 50gr JHP.
I'm averaging about 3100fps out of a 16" AR-15. (Caldwell Precision Chrono approx 10' away)

Primers look fine, and the bullet holes are accurate and nice and round on the paper at 100yds.
I checked ARMSCOR and PMC Bronze which are 300-400 FPS slower on the same day so it got me thinking:Is this too much? Realize I'm shooting in 30-50deg weather and think this won't be safe come summer.

Anyone else been in this speed range with H335?

 

[mac1911]

You really have no idea what armscor and PMC are using for powder or even the burn rate of that bulk lot of powder they used on that day they loaded that stuff
I'm running 26 grains with some Sierra 52 grain matchkings.
No idea what they are doing for fps. I see no signs of pressure. I went 26.3 and 26.5 and my groups opened up a bit and changed point of aim vs point of impact quite a bit.
I did the OCW system to find my load. I can run 25.5 to 26 with out any significant change of POA vs POI
I also run nosler 50 gn ballistic tips with 335 but they like a lower charge (24.3) those clock a touch over 3100fps when I tested them.
So yes 26 is aproaching the max threshold for H335 per most data..
I think Sierra goes on the high side of 26.X?

 

[Schuyshot]

My Hornady book has max load at 25.7 H335 getting 3300fps and a little faster on their website with 26.0gr. (Out of a 24" barrel!) I just kept working up to this point. I think maybe Ill go back to 26.6.

 

[AyeR15]

I know I know, another is hot-rod load question...

Worked my way up to 27.0 grains of H335 under a 50gr JHP.
I'm averaging about 3100fps out of a 16" AR-15. (Caldwell Precision Chrono approx 10' away)

Primers look fine, and the bullet holes are accurate and nice and round on the paper at 100yds.
I checked ARMSCOR and PMC Bronze which are 300-400 FPS slower on the same day so it got me thinking:Is this too much? Realize I'm shooting in 30-50deg weather and think this won't be safe come summer.

Anyone else been in this speed range with H335?

ill check when I get home but I load a similar cartridge at 26g with H335. Your data loads look spot on though. I would back off a hair IMO.

 

[Mountain]

Are your primers cratering?

 

[Schuyshot]

Are your primers cratering?

Nope.

 

[EddieCoyle]

It can be tough trying to diagnose over-pressure in an AR-15 by looking at primers.

If you have a micrometer, mark a spot on the case just ahead of the extractor groove and measure the diameter before and after firing. Any expansion at all in this area indicates excessive pressure (and you shouldn't reload the case).

You can also pop out a primer and reprime one of the cases. If you're running too hot, the primer pockets can end up noticeably looser.

How's the ejection? Does the rifle throw the brass in the same place as "normal"?

 

[NavelOfficer]

Realize I'm shooting in 30-50deg weather and think this won't be safe come summer.

Not related directly, but IMR promotes their IMR 8208 XBR as...

IMR 8208 XBR The latest in the versatile IMR line of fine propellants, this accurate metering, super short grained extruded rifle powder was designed expressly for match, varmint, and AR sniper cartridges. Ideally suited for cartridges like the 223 Remington/5.56mm, 308 Winchester/7.62mm NATO and the 6mm PPC, shooters will find IMR 8208 XBR totally insensitive to changes in temperature, while yielding max velocities and “tack driving” accuracy. Clearly, the competitor’s “choice” and the Varmint Hunter’s “dream powder”.

Perhaps, this might address the temperature issue, but you aren't likely to change powders

 

[mac1911]

Not related directly, but IMR promotes their IMR 8208 XBR as...

IMR 8208 XBR The latest in the versatile IMR line of fine propellants, this accurate metering, super short grained extruded rifle powder was designed expressly for match, varmint, and AR sniper cartridges. Ideally suited for cartridges like the 223 Remington/5.56mm, 308 Winchester/7.62mm NATO and the 6mm PPC, shooters will find IMR 8208 XBR totally insensitive to changes in temperature, while yielding max velocities and “tack driving” accuracy. Clearly, the competitor’s “choice” and the Varmint Hunter’s “dream powder”.

Perhaps, this might address the temperature issue, but you aren't likely to change powders

I have been playing with 8208 and will tell you it meters very very well. I have used it in 90' days and as low as 28' I,can't say I noticed any change in performance.
I did load some higher end powder charges for testing some 335 loads in the winter...I have no way to prove it other than what EC touched on ejection pattern. When shooting them the following summer the ejection changed.
When I shot those 335 loads in the hot summer my brass was hitting the guy to my right up near his rifle and left arm usually this gun dumps brass at 4 o'clock.
Now I don't know if pressure increased or not but forward ejection is generally a sign of over gassed.
I am not sure but I believe you could have a over gassed problem and still have safe pressure?