powders, primers

[Nukes]

Clean burning, relatively temperature insensitive, accuracy from a 6.5 Grendel 20" barrel—Which powder wins?

What primers do 6.5 Grendel accuracy fanatics prefer?

[babaganoush]

Clean burning, relatively temperature insensitive, accuracy from a 6.5 Grendel 20" barrel—Which powder wins?

What primers do 6.5 Grendel accuracy fanatics prefer?

The two powders I have tried are IMR 8208-XBR and Ramshot TAC. 8208 is very stable, and burns very clean. In my BHW barrel, I only need 3 wet patches and a dry. No brushing needed. TAC seemed a little touchy about the temps, so I gave up on it. I have heard very good things about CFE223, but availability prevents me from evaluating it.

CCI-450 primers are what I hear about most commonly (my choice, as well), but I hear very good things about Wolf Primers, with respect to their consistency and applicability to the demands of an AR's floating firing pin.

As I've recently posted, with 28 gr of 8208, CCI 450's, HDY cases and 123 Amax, I'm getting 1/4 - 3/8 moa and 2615 fps from a 22" BHW barrel.

David

[Nukes]

Impressive. Isn't the IMR 8208-XBR also used for .308?

When you say "demands of the AR's floating firing pin," do you mean the Wolf primers are more resistant to slam fires?

[Michael]

CFE 223 seems to be pretty clean burning in the loads I have made...get pretty good consistency on the chrony. Not sure on temp stability, I usually shoot early in the AM or late in the evening. Still fine tuning in my spare time. WIN 748 is kind of dirty, but meters well and gives pretty good consistency as well, just lower velocity than CFE 223.

I use CCI #41s in all my ARs. Not that I am so worried about slam fires...my understanding is that if you aren't firing full auto, it's less of an issue...could be wrong on that, still a free floating pin. I just got a hell of a deal on 5000 of them last summer.

[bwaites]

8208 can be used in .308, .223, and the Grendel, and gives good results in all of them.

However, its got a sharp edge, go a little heavy on the load and it will bite you. It goes from OK, OK, OK, OK, to Oh NO, really fast!

[mwilkins]

8208 can be used in .308, .223, and the Grendel, and gives good results in all of them.

However, its got a sharp edge, go a little heavy on the load and it will bite you. It goes from OK, OK, OK, OK, to Oh NO, really fast!

One thing I have not read about powders is if the burn rates are pressure sensitive. In other words, does the burn rate increase with the more internal pressure.

I have a lot of experience with Ammonium Perchlorate formulas for rocket motors in all forms being single, bi and tri modal formulations. The different sized particles all have different amounts of surface area that burns. That surface area has a particular burn rate but that burn rate changes with pressure. Any voids or un accounted for surface area within the motor can create pressure spikes. Those pressure spikes in turn increase the burn rate which in turn increases the internal pressure. It creates an ever increasingly problem for the perceived characters of the motor and end result is not pretty.

Powder and AP have similar properties that when either fuel if you will, burns at a slower rate when not in a confined area but when put into such an area, be it a brass case or aluminum rocket motor, burn characteristics change rapidly.

I may be way off in left field here but the gears just started turning in my head and thought that I have not read any literature relating to burn rate profiles. Guess that would be more along the lines of internal ballistics.....

[Drifter]

Not the cleanest, nor the dirtiest, but easily the most accurate propellent I've used in numerous Grendel barrels is AR-Comp. I prefer CCI #41 primers, but the powder doesn't seem too picky, and is seemingly very temp stable. 27.7gr behing a 123gr pill seated to appropriate COL is magical. And FWIW, it's less likely to short-stroke in barrels with RLGS versus 8208 powder. I've burned through ~25 lbs of AR-Comp, and currently looking to buy at least ~16 lbs...

[sneaky one]

[babaganoush]

Impressive. Isn't the IMR 8208-XBR also used for .308?

When you say "demands of the AR's floating firing pin," do you mean the Wolf primers are more resistant to slam fires?

From what I hear, 8028 is a good powder for .308, as well. It seems to perform well in a number of calibers, as does CFE223. I personally use Varget in my CZ-550 .308, which shoots 2700 fps at < 1/8 moa. (No sense in fixing what isn't broken.)

As far as the temperature stability of IMR 8208-XBR goes, I shoot the same load anywhere from 30'F to 100'F. Velocities are very consistent (+/- 25 fps), and I've never seen over pressure indications.

As far as the Wolf primers go, yes - the cups are harder than most, and are nigh immune to slam fires.

David

[babaganoush]

8208 can be used in .308, .223, and the Grendel, and gives good results in all of them.

However, its got a sharp edge, go a little heavy on the load and it will bite you. It goes from OK, OK, OK, OK, to Oh NO, really fast!

I can't comment on the sharp edge you're referring to, Bill. My load workup was very gradual, with attention paid to the vertical stringing, as well as pressure signs. At 28.2 grains, where I stopped, I noticed nothing that alarmed me; cases are clean, straight and true. Primer pockets are tight, and no cratering or primer flow noticed. It also seemed to me that anything over 27.5 grains was a compressed load, with the 123 grain Amax squeezing in there.

I am curious where the "oh no" threshold you refer to occurred in your testing. It would be good to know how close the 28.0 I'm at is to that threshold. This is, of course, with the understanding that our two rigs would have their differences.

David

[babaganoush]

I may be way off in left field here but the gears just started turning in my head and thought that I have not read any literature relating to burn rate profiles. Guess that would be more along the lines of internal ballistics.....

I am, by no means, an expert in the burn properties of powders, but I am aware that many powders don't like temperature swings. As a result, case pressures will increase and often with negative consequences. Some of the more stable powders are identified as such - Hodgdon identifies their stabilized powders as "Extreme". These powders (Varget and H322 among them) are known for their consistent performance across wide temperature ranges.

If you shoot in relatively consistent conditions, powder choices can be less critical. As a "varminter" shooting in the high desert, I strive to use powders with good temperature stability since I shoot in a climate where the morning can be in the low 40's and end up in the high 80's or 90's pretty easily.

I'm sure (hope?) the people with greater knowledge will chime in with information on how to determine the relative stability of the various powders.

David

[Nukes]

[ricsmall]

Nukes, the wolf SRM primers are the ones most guys on here are using. I'll second the frustration on finding components!

[Drifter]

Wolf makes a small rifle and a small rifle-223 primer. I assume you are using the plain small rifle primers.

I prefer the harder cup of Small Rifle Magnum (SRM) primers when using Wolf in a Grendel AR-15.


As for current availability, 5k Wolf SRM's delivered for $200 (includes shipping and hazmat) on this link:

http://www.ammunitionstore.com/products/small-rifle-magnum-primers-wolf-performance-5-000-pc-box-free-shipping.html

[babaganoush]

I prefer the harder cup of Small Rifle Magnum (SRM) primers when using Wolf in a Grendel AR-15.

+1

I was referring to the SRM. Forgive me for not being clear, Nukes.

David