Burn rate question

[RM44]

Does a faster burn rate powder improve the performance of a short barrel 6.5G? Specifically a 12" barrel.

I am looking to hop the speed up a bit from the 123 gr Hornady Black. I'm thinking 2400 fps range.

Thanks

[A5BLASTER]

Only 2 powders I know of that could get you there cfe223 or leverevolution. But your going to be running very hot and high pressure too get there and probably will break something very soon running that hot.

You can safely hit around the 2350 mark but the 2400 mark is going too be pushing high pressure.

Let the bc work for you. If you need more speed drop down too a 108,107 or 100 grain pills and load up with cci450 primers and h335 powder.

[grayfox]

I don't think you will see 2400 from a 12" in 123 bullets. Need to drop down to 110 or 100-107 wts.
As to burn rate, CFE and Lever are actually slower than the faster powders that work for the Grrr. Think H335, Xterminator, 8208XBR and/or Tac -- these are more in the "faster burn" section.

[LRRPF52]

Factory Federal 120gr OTM Match does 2384fps average from my 12" Grendel, with some of the highs being 2411, 2398, 2397, and 2406fps.

My 47,302psi CFE223 load under a 123gr A-MAX at 2.275" COL did 2502fps from my 16" AA barrel when I ran my first CFE223 ladders with the 123gr A-MAX.

I have no doubts that I can hit 2400fps with a 123gr from the 12" barrel with CFE223, but since the BC does more work for you than a 25fps increase, I will focus on accuracy and babying my brass rather than chasing raw speed when there is no clickable or reticle increment advantage for a few fps.

[Klem]

RM,

So the theory goes.

The slower the powder the more bulky it is until the available space becomes the limiting factor. You end up with an inefficient load because some of the slow powder is not completely burnt by the time the bullet exits, and that is wasted potential velocity.

With fast powders, peak pressure becomes the limiting factor. You end up with space left in the case which is wasted potential capacity/velocity.

With an auto loader there is also the issue of how much pressure is available to cycle the action when the bullet passes the port. Not such an issue in the Grendel but this is well known in the 300BLK community when hand-loading subsonics.

Ammunition manufacturers choose powder for the average length of likely barrel. 12" is shorter than the average Grendel so Hornady will have chosen a slower powder, or powder blend than is best suited for your gun. This might mean there is more flame out of the end of your short barrel (unburnt powder) or less precision on the target than longer barrels (unburnt powder gives wider velocity spreads). Likely you will be able to load more accurate and with less flame by trying faster powders but with max peak pressure being the limiting factor in your case, don't expect a huge increase in velocity. In fact, if you load to the same peak pressure as your factory ammo you might not increase your velocity at all.

A word of caution... How do you measure peak chamber pressure if you don't have the same expensive equipment that manufacturers use? All the more important in our light-weight relatively fragile AR receivers. By the time the cases are bulged, primers flattened or cratered it is too late. Use a strong, stiff primer like CCI450 and there's even less feedback. No sticky bolts on an AR to help you either. It's like reading tea leaves. If you load to 2,400fps you will damage your gun.

[grayfox]

'52 I'd say you have a fast barrel there!
I looked back at my 12.5 and 12.7" data from my chrony, the 123's are 2240-2285, one set of 110 control chaos was 2402, my 100 eldm's were 2400-2460, some tnt 90's factory, 2587-2628. I spoke from this data set out of my short-guys.

[thegunman96]

Do any of you have a good recipe for the 12.5" barrels using Leverevolution with 123gr bullets?

[slip357]

I would go with 107 gr. and H-335 or imr 4895 , im using 30 gr. H- 335 with the 107 tmk . Its a hot load but is very accurate out of my 20 inch. Im talking 1 1/2 inch groups at 300 yrds

[LRRPF52]

'52 I'd say you have a fast barrel there!
I looked back at my 12.5 and 12.7" data from my chrony, the 123's are 2240-2285, one set of 110 control chaos was 2402, my 100 eldm's were 2400-2460, some tnt 90's factory, 2587-2628. I spoke from this data set out of my short-guys.

Hornady 123gr, yes. But you didn't chronograph 120gr Federal Match, which is a faster load both in the 12" and 18" Grendels.

The AA 123gr Scenar factory load did 2330fps from David Fortier's 12.5" Grendel over an Oehler 35, 15ft from the muzzle, in 30˚F weather.

My numbers are 15ft from the muzzle as well, so mv is actually higher.

90gr TNT does 2670fps average from my 12" unsuppressed, 2683fps suppressed with a .30 TBAC Ultra 5.

Manufacturers have different powders they use, different bullets, and therefore different speeds.

Barrels have different rifling profiles as well, but none of the numbers I'm seeing are out of the ordinary except for one guy's speeds I saw posted on AR15.com, which were extremely low.

I personally don't see 2400fps being unachievable at safe pressures from a 12" with my Faxon group buy barrel that has the 5REE rifling, and the numbers I'm getting aren't anywhere out of what is to be expected.

I will load to a longer COL which allows more case capacity and more instantaneous start pressure, without jamming the lands. I make dummy cartridges to test rifling engagement before setting in my dies, giving myself leeway for ogive variances in the manufacturing process, especially with more secant nose profiles.

Looking at my pressure-tested loads with the 123gr A-MAX, my 2.275" COL 31.1gr CFE223 load should generate an average of 2352fps from the 12" barrel.

CFE223 is one of the slower burning powders for 6.5 Grendel that fills the case over 100% without peaking the pressure past MAP with 120-123gr bullets.

I've been looking at loading the 107gr SMK over 8208XBR for the 12" though to punt it out and have reduced muzzle climb, with expected 2430fps mv extrapolated from what I'm getting with one of my nodes from the 17.6" Lilja barrel.

8208XBR and the 107gr SMK are a great combo in 6.5 Grendel.

[A5BLASTER]

While my loading skill set is much less then the more experienced members that have responded here I will add this.

I stand by my first post and klems and grayfix's post. If you want 2400 fps at the muzzle drop down in bullet weight too around 100 grains and run it with h335 powder.

I really don't think it will be a safe load at 2400 fps muzzle velocity and a 123 grain bullet. I would make sure you fire each and every single round over a chonagraph during load work up

But I have been wrong more then once before in life.

[sneaky one]

I would try a few pals Chrono's to verify accuracy , of data. I had 2 chronos that made numbers up as it went along at the range.

Nothing is perfect, the designers do try tho.

The $200 Magneetospeed has been great.




Sorry, back to orig post---Try 8208 & H335, as a start point with the short bbl. It's quite the fireball out of the 16" using H335, without the

A2 flashhider. BFT was there... Wow! Almost like a small tank bbl blast.

[RM44]

Thank you all for the replies. I reload like I cook; as long as I have a good recipe, I do all right. When I go off the reservation, the good Lord only knows how it will turn out.

It seems like 2400 might be pushing it a little. I don't want to cause a premature barrel burnout, stuck cases with bulging primers, or a hot load that bangs up the weapon. I do want to stay with the 120-123 gr bullets; the heavier bullets with better terminal ballistics and barrier penetration than 5.56 are what is drawing me the the 6.5G.

[A5BLASTER]

Thank you all for the replies. I reload like I cook; as long as I have a good recipe, I do all right. When I go off the reservation, the good Lord only knows how it will turn out.

It seems like 2400 might be pushing it a little. I don't want to cause a premature barrel burnout, stuck cases with bulging primers, or a hot load that bangs up the weapon. I do want to stay with the 120-123 gr bullets; the heavier bullets with better terminal ballistics and barrier penetration than 5.56 are what is drawing me the the 6.5G.

For the 123 and heavier bullets cfe223 and leverevolution seem to make the best speeds but they are a fast burn rate powder and can be a lil temp sensitive

[Klem]

It seems like 2400 might be pushing it a little. I don't want to cause a premature barrel burnout, stuck cases with bulging primers, or a hot load that bangs up the weapon.

RM,

It won't be that dramatic at 2400. It will work until a bolt lug breaks off. That seems to be the universal weak spot for hot loads. This might not happen for several hundred rounds. If you carry a spare you might even be ok with this.

[LRRPF52]

I asked a very prominent 6.5 Grendel rifle manufacturer about broken bolts at SHOT last week. He said he had 3 he can recall over the past year from customers, and in every case, they were hand loads.

One of the guys was loading a 123gr to over 2800fps, which is 6.5CM territory really. After 600 rounds, he finally broke a bolt. 2800fps with a 120-123gr class bullet in the Grendel has got to be in the 60,000-67,000psi or more region with such a small case.

We had a former forum member who did the same with the 120gr Barnes TSX. He simply looked online for a random hand load someone posted somewhere else under a 120gr cup and core bullet (not knowing that cup & core and solid bullet data is not interchangeable), then immediately used that data for the Barnes 120gr TSX without any work-up. He was getting 2820fps from a 24" Liberty barrel with the 5R rifling. When advised to cease shooting that load, he refused and said we were handicapping the full potential of the 6.5 Grendel, and that the 5R rifling was allowing him to safely shoot a 120gr solid copper monolith at over 2800fps all day long, no pressure signs!

We explained that 2820fps with a 120gr Barnes solid IS the most important dangerous pressure sign, followed by accusations that we were lying, haters, trying to cheat him from his brilliance and special achievements.

If you use Joe's internal ballistics calculator that is calibrated for 6.5 Grendel, you can get a very good idea of where your results will be, as it has usually been within 10fps of my actual readings over the years.

Shooter's Notes 6.5 Grendel Internal Ballistics Calculator