Velocities seem low for my AR loads

[bbowles]

Been loading for a Daniel Defense AR 5.56 chamber (16" mid) for about 6 months. I have worked a few loads up with different powders mainly and the seem to be considerably lower than manuals say. Not really all that concerned but curious since shoots well anyway.

I have worked up loads to max charge (according to 2 or 3 loading manuals) watching for pressure signs and through a chrono. They seem low but knew they would be lower than published since my AR is only a 16" and most manuals use test gun with 20" or 24". I get that for every 1 inch of barrel I will lose approx 25 fps. Therefore, if published with 20" I should expect approx 100 fps less.

My loads have been using LC 13 brass, CCI BR4 & Rem 7 1/2 primers (usually the Rem's are about 25-50 fps slower), Sierra 69 Matchking with following powder charges and approx fps:

Powder Charge My FPS Published FPS

Varget 26.3 * 2670 3010
CFE 25.8 2575 3029
H335 24.0 2525 2960
AR Comp 23.5 ** 2630 2969

* 0.3 past max published and had some light ejector rings only (.0005 casehead expansion)
** 0.3 past max published but No pressure signs at all but think getting close to my max

 

[godofthunder]

I don't think they are that low. I would probably only be expecting somewhere around 2700fps with 69SMKs and 16" MSR. You'll lose a little more velocity with it being a gas gun as opposed to a bolt gun on top of the bbl length difference.

 

[lancetkenyon]

I have a 24" barrel on my AR.

My recipe:
LC 12 brass
Rem 7 1/2 BR Primers
25.0gr. Varget
69 SMK
3033fps.

I am amazed you can load 26.3gr. of Varget. I had slight signs of pressure at 25.5gr. in my rifle, so dropped to 25.0. But 25.0 was also in my accuracy node and produced the best groups and most consistent velocities.

My 16.5" barreled Carbine shoots the same 69 SMK load at 2598fps. Very similar to your recorded velocities. So I reserve the carbine for shooting 50gr. V-Max loads at 3022 fps. Vs. the 3403 fps out of my 24" barrel. I see about 54fps difference per 1" of barrel length in my two ARs with the 69SMK, and 47fps with the 50 V-Max.

 

[bbowles]

Thanks guys. That seems reasonable now. My rifle likes Varget but is a compressed load to get those velocities. 25.5 gr of Varget is really upper end for me too. Hate the compressed loads too.

Tried the AR Comp recently and am liking this! Velocities are pretty good and not compressed. If grouping and SD is good that will be my new load. Hope so cause I just had 4 lbs of Varget getting ready to ship today from backorder but turned it down since just bought 3 lbs of AR Comp. Hope I don't regret since Varget so hard to get.

You guys that want Varget might check with Midsouth Supply. They might have that available but prob someone else in line. Thanks.

 

[Tx_Flyboy]

bbowles,

Where did you get ur ar-comp & varget from?

 

[bbowles]

AR Comp locally in SW MO. Varget was coming from Midsouth Shooters Supply but I rejected my backorder. Hope won't regret.

 

[MarkCO]

Just an FYI, I have seen much higher barrel temps and wear using Varget in the 14.5 and 16 inch ARs. A little more in the 18s too. It is a bit slow for the shorter AR barrels so you will get more gas port erosion.

 

[bbowles]

MarkCO,
Makes sense. Hope the AR Comp will work.