Load testing for my CZ527

[Buck2732]

Bolt action loads please do not use in your semi/fully automatic wpn.

Hello the hoard some results from last Sat on the range.

All loads are in Hornady brass, CCI450 primers, CFE powder and 123g SST.
All readings taken 15 foot from my muzzle. All strings are ten rnds
Weather 20deg C, 79 Ft above sea level. 979mb

The rife CZ527, 22 inch tube, with my moderator and vortex scope.

The following all had a COL of 2.255

30.9 Average fps 2586.9
31.2 Average fps 2612.3
31.5 Average fps 2628.3
31.8 Average fps 2664.5
32.1 average fps 2700.4

The following all had a COL of 2.285

30.9 Average fps 2578.5
31.2 Average fps 2634.7
31.5 Average fps 2641.5
31.8 Average fps 2675.7
32.1 Average fps 2684.2

I also shot a control of ten rnds factory load before the above which gave an average fps 2532.4.

I still have not processed the empties, there is not much in the way of any indication of any problems. So if you would like a photo please ask.

I have images of the groups but I was more concerned with not shooting the Chronograph.

Bolt action loads please do not use in your semi/fully automatic wpn.

[SHORT-N-SASSY]

Buck2732,

Thanks for sharing this interesting experiment.

What is the inside length of the CZ527 magazine?
What is the maximum COL at which point the bullet jams into the lands of your present throat?

[Buck2732]

Buck2732,

Thanks for sharing this interesting experiment.

What is the inside length of the CZ527 magazine?
What is the maximum COL at which point the bullet jams into the lands of your present throat?

The inside length of the magazine is 2.327.

I did not measure the max COL for the 123SST but for the 107SMK it is 2.344.

I hope that helps.

[SHORT-N-SASSY]

The inside length of the magazine is 2.327.

I did not measure the max COL for the 123SST but for the 107SMK it is 2.344.

I hope that helps.

My questions are prompted by the Report on the Internet that 2,650 - 2,700 fps, with the Lapua Scenar 139-grain bullet, has been achieved with the bolt-action CZ527, with a 22-inch barrel, chambered for the 6.5mm Grendel (http://www.ar15.com/forums/t_3_121/5...age=1#i5517109). One would expect that a longer-than-factory-loaded COL was used --- and, perhaps, a longer chamber throat --- to obtain those velocities.

[LRRPF52]

Those loads were fine for me in my 16" Grendel. I pushed past them to see where the departure would occur, which was at 33.2gr of CFE behind the 123gr A-MAX.

Hornady's 9th lists 31.7gr as max for the 129gr cup and core pills, like the 129gr SST, 129gr IB, and 129gr SP.

Your 22" velocities compared to my 16" velocities make sense, and average

Examples:

[B]
16" 6.5 Grendel AR15[/B]          [B]22" CZ527[/B]      difference
31.1 2489                      31.2  2612      123fps
31.4 2520                      31.5  2628      108
31.7 2532                      31.8  2664      132
32.0 2553                      32.1  2700      147

When I run the numbers through JASmith's velocity estimator, to include the change in powder weight from 32.1gr to 32.0gr, and from 22" barrel to 16" barrel, it gives me an estimated velocity of 2555fps, 2fps off from my real world mv of 2553fps.

http://shootersnotes.com/calculator/velocity-estimator/

I loaded to 2.275" for my batch when I did those ladder tests. You should be able to easily get 2800fps with the 123gr SST. I'll show you what your next loads will register:

CZ527 22" 6.5 Grendel Estimated MV
32.6gr ~2738
32.9gr ~2761
33.2gr ~2784
33.5gr ~2806

If it were mine, I would continue to do as you have, push the COL out some more to where you are just off the lands, and see where you can go. You really should not have problems reaching 2800fps with the CZ bolt gun.

For a 22" AR15, I would not mass produce a load over 32.2gr of CFE under a 123gr, given that 31.7gr is the max under a 129gr. Even there, you have speeds that are around 2700fps, which is plenty fast. CFE223 has proven to be a very forgiving powder for me, creeps up predictably, no surprises, no spikes, just a nice gradual velocity increase that behaves well with the case capacity of the Grendel.

Thanks for your detailed report. I want a CZ527 badly, chambered in 6.5 Grendel.

[NugginFutz]

Thanks for your detailed report. I want a CZ527 badly chambered in 6.5 Grendel.

If that's the case, I know of at least one place where you can get it badly chambered in 6.5 Grendel. Me, on the other hand, I'd really like one properly chambered in 6.5 Grendel. Unfortunately, the one CZ-527 I had was chambered in .223 Remington, and was not a terribly accurate shooter. It was sold to finance another project. I can always start again, though.

(commas are deadly)

[Nukes]

As some of you may already know, I bought a CZ527 Carbine in 7.62x39 for my youngest (8) son's Christmas gift last year, intending to convert it to 6.5 Grendel... but the younguns (pun intended) had so much fun shooting inexpensively that I have not gotten around to the conversion. Last weekend we went out to play in the desert and everyone (well, all the guys anyway) got first round hits on IPSC steel at lasered 503yds out of that 16" lightweight using Silver Bear ammo. The two oldest did it offhand.... At this point, the conversion is waaaaay down the priority list. Eventually... but it is costing me less to shoot the CZ527 than anything else we own.... including the rimfire that loves Lapua Midas+.

[Nukes]

....I want a CZ527 badly chambered in 6.5 Grendel.

Wouldn't you rather have a CZ527 well-chambered in 6.5 Grendel?

[LRRPF52]

Comma added. There's steel case 6.5 Grendel now if economy ammo is what you are looking for.

When my daughters move from rimfire to centerfire, I want it to be done on the 6.5 Grendel in a micro action.

Mv's of 2750-2800fps with 123gr is right at the heels of a .260 Remington, with 10gr less powder.

[Variable]

Man, it's a rough crowd around here sometimes.LOL

I also wish CZ would release a 527 properly chambered in Grendel.

I have a thing for mannlicher stocks, so I want a factory CZ 527FS in 6.5G to go with my other one in .223 caliber.

I know I could get one built, but I don't want to waste the money. Grendelizing would be so dang easy for CZ to do, I want them to follow through with it (after the poll they took previously).

[Buck2732]

Thanks for your detailed report. I want a CZ527 badly, chambered in 6.5 Grendel.

I will trade you, yours for mine. Though, I guess I might get in to trouble if I did.

[Nukes]

...For a 22" AR15, I would not mass produce a load over 32.2gr of CFE under a 123gr, given that 31.7gr is the max under a 129gr. Even there, you have speeds that are around 2700fps, which is plenty fast. CFE223 has proven to be a very forgiving powder for me, creeps up predictably, no surprises, no spikes, just a nice gradual velocity increase that behaves well with the case capacity of the Grendel...

Usually I load 8208XBR, but this testimonial prompted me to load some CFE223 charges under some 123gn SMKs. 31.2, 31.3, 31.4, and 31.5gn all obtained nearly identical velocities of ~2525fps out of a 20". Apparently reaching a plateau. I infer I should not step to any higher charges.

[LRRPF52]

Usually I load 8208XBR, but this testimonial prompted me to load some CFE223 charges under some 123gn SMKs. 31.2, 31.3, 31.4, and 31.5gn all obtained nearly identical velocities of ~2525fps out of a 20". Apparently reaching a plateau. I infer I should not step to any higher charges.

That's only a net increase of .3gr, so it doesn't surprise me that your velocities are tight. There aren't a lot of scales that can accurately duplicate .1gr increments, especially in a contaminated environment, particularly with the presence of RF interference nowadays. It also might indicate an accuracy node for you. Work it up in .3gr increments and see what you get, always checking the speed increase relative to the charge weight. If you get an increase that exceeds 30fps, I would look at that as a likely ceiling.

When I did my pressure ladders with CFE, I was getting very consistent 12-21fps increases per .3gr of charge. I keep electronics with RF away from the load bench, and I'm pretty OCD about my charge weights. I didn't use a powder measure with those, but did them all by hand. My 31.2gr load that I produced is very accurate, proving so in a new Grendel shooter's hands at 500yds on a KYL plate rack, which he cleaned.

[Nukes]

[LRRPF52]

I'm not going to advocate anyone push past a point they aren't comfortable with, but there are some barrels that will hit 2700fps with CFE and 123gr in the AR15.

Heck, Bwild97 got 2662fps with the 129gr SST from a 24" AR15 using 31.0gr of CFE.

I think 2700fps is child's play in a bolt gun with CFE and 123gr. Some barrels will produce more speed than others. I would be happy with a 20" in the mid-2500fps range though, especially in an accuracy node.