AR-Comp Burn Rate ?

[deadduck357]

Where's the burn rate for AR-Comp? I've searched all the burn charts and can't find. Found an old thread here from back in 2011 asking the same question and Alliant finally responded that it is similar to IMR 4895. It's 2018 and still not added?? Is it a secret or am I missing it somewhere?

 

[mike06]

Real close to Reloader 15 I find it a bit faster. Best part is that it temp changes does not seem to make speeds vary.

http://bulletin.accurateshooter.com/2011/03/new-ar-comp-powder-from-alliant-details-revealed/

 

[Rodney]

I’ve used AR-Comp for a couple years and in a few different calibers. H4895 seems the closest comparison that I can find. Have even used the recommended start loads to work up loads for calibers that have no load data for AR-Comp. It’s faster than Varget for sure. It’s a great powder for 223 and 308, but I’ve found uses for it in other cartridges as well.

 

[deadduck357]

Real close to Reloader 15 I find it a bit faster. Best part is that it temp changes does not seem to make speeds vary.

http://bulletin.accurateshooter.com/2011/03/new-ar-comp-powder-from-alliant-details-revealed/

Yeah I found that too but why isn't it included in any burn rate charts (that I can find anyway)?

 

[deadduck357]

I’ve used AR-Comp for a couple years and in a few different calibers. H4895 seems the closest comparison that I can find. Have even used the recommended start loads to work up loads for calibers that have no load data for AR-Comp. It’s faster than Varget for sure. It’s a great powder for 223 and 308, but I’ve found uses for it in other cartridges as well.

I read that it was very similar to 4895.

 

[swadiver]

H4895 from my use with it

 

[brantfredrickson]

I read that it was very similar to 4895.

AR-Comp is a Bofors powder, I believe produced in Karlshoga, Sweden for Alliant, And doesn't get included in the Hodgdon's burn chart. However in the Alliant load quide you can get a feel for the burn rate against other Alliant powders by comparing the velocities of different powders for a specific cartridge and bullet weight at the maximum pressure. Usually the slower powders have the higher velocity when cartridge, bullet weight and maximum pressure are constant.

I shot this powder in a .308 cartridge with a 155 grain SMK 2156 palma bullet out of a 30 in barrel at 3010fps. Very clean burn with good brass life for a couple of years and found it temperature stable from 50 to 90 degrees. I consider it wonder stuff.

 

[avidflyer]

AR-Comp is a Bofors powder, I believe produced in Karlshoga, Sweden for Alliant, And doesn't get included in the Hodgdon's burn chart. However in the Alliant load quide you can get a feel for the burn rate against other Alliant powders by comparing the velocities of different powders for a specific cartridge and bullet weight at the maximum pressure. Usually the slower powders have the higher velocity when cartridge, bullet weight and maximum pressure are constant.

I shot this powder in a .308 cartridge with a 155 grain SMK 2156 palma bullet out of a 30 in barrel at 3010fps. Very clean burn with good brass life for a couple of years and found it temperature stable from 50 to 90 degrees. I consider it wonder stuff.

ever try it with a heavier bullet 185-200? Understand why the 155

 

[jsthntn247]

ever try it with a heavier bullet 185-200? Understand why the 155

Havn't tried it but it would work well if your throated appropriately in the .170-.200 freebore range. I used it in a 223 and it was about .3gr faster than 4895 and filled the case considerably more.

 

[Fotheringill]

IIRC, when you see a manual listing that powder and the bullet you are shooting, the faster burning powder on the list is always the first listed and not at all relevant to the "best" for the caliber and bullet.

 

[Laurie]

Here is what Alliant said to Accurate Shooter when it was first introduced:

http://bulletin.accurateshooter.com/2011/03/new-ar-comp-powder-from-alliant-details-revealed/

ie that it's a modified form of Re15, and it's a bit quicker than that powder making it similar to H. VarGet, actually slightly slower. As others have said though, actual loads suggest it's rather quicker burning than that, so I thought I'd have a look at Alliant and Sierra data for the 224 Valkyrie with the 90gn SMK. Being a new cartridge, the data tables should be comparable in that they'll all be recent, and with Federal brass being first on the scene for the Valkyrie, it is another common feature.

Alliant gives a max charge of AR-Comp of 22.7gn AR-Comp for 2,574 fps MV, and 25.2gn Re15 for 2,679 fps suggesting that AR-Comp is significantly quicker, not 'slightly'. MVs are for a 24-inch barrel.

Sierra's datasets also use Federal brass and a 24-inch barrel. Its max for AR-Comp is a low 20.5gn and a disappointing 2,400 fps. The nearest equivalent load here to the Alliant data is 22.5gn H4895 (maximum) for 2,500 fps.

Varget appears to be significantly 'slower' than AR-Comp in this table in terms of maximum / achievable MVs, but even when comparable MVs (ie 2,400) are looked at, the Hodgdon powder needs an extra 1.6gn to get there. Even H4895's 2,400 fps (below maximum) charge weight is above AR-Comp's at 21.4gn, 1.1gn higher.

Burning rate isn't a fixed metric and can vary between cartridges, so data for others might change this, but it does seem on the face of it to be quicker than Alliant originally stated.

Interestingly, Sierra uses the convention of quickest powder at the top of the table, slowest at the bottom. It slots AR-Comp in between VarGet (quicker) and IMR-4166 (slower). That in itself is a slight puzzle as I've always seen 4166 as quicker than VarGet.

https://sierrabullets.files.wordpress.com/2018/03/224-valkyrie1.pdf