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Old 03-17-2017, 01:14 PM
CB900F
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6.5 Grendel Oddities



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Fella's;

I don't own a Grendel, but due to all the hoopla recently voiced on several sites, I decided to take a look at the reloading information. I looked at the Hornady X and Noser 8, manuals as well as the 2016 Hodgdon magazine and Western Powders 6th edition publication.

Hornady shows that their data was developed in an Alexander Arms rifle with an 18" barrel. I'm supposing that this is an AR platform derivative as that's what Alexander Arms created the round for. Nosler states that all their data was found with a 24" Pac-Nor barrel. Hodgdon also says that they used a 24" barrel, but not whose. Western used a 20" barrel & specifically stated that the round is for AR-15 style guns. Due to the sheer amount of data available, I limited my information gathering to 120 and 123 grain bullets. It's also worth noting that Hornady does not give actual velocities of a load, they use 100 fps increments. So if they say 2600 fps, I'm presuming that's not what the true velocity was, just that it's somewhere in that 2600 fps window. If they include 2591 fps, or cap at 2650 fps, I don't know and don't see an easily found explanation in their manual.

None of the data showed a consistent power/bullet combination across the board. Benchmark was the most common, but of course, Western didn't provide data as it's not their powder. TAC and Accurate 2460 were both used by Nosler and Western. Reloader-15 was used by Hornady and Nosler

What I've found to be interesting though, is that barrel length appears to make very little difference in velocity across the information supplied, regardless of the source.

Hornady says top velocity for a 120-123 grain bullet is 2500 fps. That's with only one powder CFE223. TAC and RL-15 top at 2400, with Benchmark at 2450 fps.

Nosler provided data for 120 grain bullets separately from 123-125 grain bullets. There, max velocity for a 120 grain bullet was 2520 fps, using RL-15 and 2484 fps using Accurate 2520. Benchmark was 2431 fps with the 120 and not used with the heavier bullets. RL-15 produced a top velocity of 2398 with the 123/125 grain Noslers. Six inch longer barrel but only minor increases in velocity. However, RL-15 showed what I'd think is a significant drop in velocity for, at maximum, a 5 grain increase in bullet weight.

Hodgdon uses only their own powders of course, but many different bullets, also in a 24 inch barrel. The Barnes 120 grain TSX topped at 2419 fps using IMR8208 XBR, and Benchmark was 2401 fps. The Sierra 123 grain bullet topped at 2508 fps using H335. Benchmark was 2460 fps.

Western used a 20 inch barrel in an AR type platform. With Accurate 2460, the Sierra 120 grain max'd at 2429 fps and the 123 was only slightly behind at 2420 fps. TAC showed the same two bullets at 2449 and 2424 fps respectively.

I find it rather odd that up to a six inch differnce in barrel length among several reputable sources also shows very little variations in velocity. That makes me wonder if there isn't further load development to be done by these programs, perhaps using slower powders in bolt action guns, such as the forthcoming CZ527 and the current Howa.

900F

Last edited by CB900F; 03-17-2017 at 01:21 PM.
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Old 03-21-2017, 08:09 PM
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Those are indeed interesting observations. I am going to keep an eye on this one as I plan to start reloading for my Grendel AR once I get some time to play.
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Old 03-21-2017, 08:16 PM
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I dont know about the reloading manuals being a good guide on barrel length. In general any of the larger bore ar-15 rounds are under capacity or expected to develop most velocity in 16 inches. The 6.5 mm might be a marginal call. These rounds just dont hold enough powder to be worth the weight and bulk of going over say 20 inches and shorter is better for the 450/458/50 rounds. I cannot say from experience, but; this seems like the conventional wisdom. That 20" is consider a LONG barrel for the 6.5

It is a shame CZ chose to go with a 24 inch barrel in the 527. Put me in a wait and see mode for a carbine to follow.
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Old 03-21-2017, 09:26 PM
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The CZ barrel should be overbore for the Grendel, making it quite and really low recoil, ideal for a suppressor or for a child's first rifle.
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