6 Grendel 107 SMK Load data

[Klem]

Just realized this is for a 6mm Grendel not 6.5...I have amended my post above.

Klem

[Lawrence97]

[Lemonaid]

I am jumping .027-.030 so that I can get 2.260 COAL to fit in my magazines.

At some point I would try seating at 2.290, 2.285, 2.280, 2.275, 2.270 and see what happens. There are Magazines that will allow it.

[Klem]

Lawrence,

The twin manual chambering does seem to coincide with a different MPI relative to all the other single manual chamberings or auto-loading. As you know, a bullet at the top of the stack sits above the forward wall of the mag so usual OAL limits do not apply. It could have moved forward twice and still able to be fed from the mag. Maybe a bullet sitting against your lands on start goes low, although the opposite was my experience.

If the bullet is moving on chambering the final OAL could also be shorter from being pushed back, twice as short for that particular round.



It's unsurprising that a new barrel displays higher pressures due to being a bit rough, or at least until a few firings have lapped it. The TBox may also be a tight barrel.

You list 30.5gns of water for the 6AR in your QL analysis. Is this correct for your cases? I don't shoot the 6AR but if you believe Wikepedia it's 36gns of case capacity, same as the Grendel 35-36gns. If it's a Grendel case necked down I wouldn't think there's a full 5gns difference. Certainly make a big difference in your pressure predictions.

[Lawrence97]

[Lawrence97]

[Lawrence97]

Grayfox,
I agree with you that 0.5 gns might be too course for this particular case size. I tested in 0.5 increments to find the upper limit with minimal components and firing 5 rounds allowed me to gather some velocity data vs just using 3 round groups or a ladder test that might not repeat. Now that I have narrowed down some powder ranges I will test within those limits using .2-.3 gn increments for fine tuning.

[Lemonaid]

I think the normal magazine that allows the the longest OAL is ASC. I routinely load to 2.290 in them. Next is C Products Defense and shortest is E-lander. I have been thinking of modifying my E-lander into something like in the link below.

https://www.cavitybackbullets.com/product-p/cb-pri-mod-mag.htm

https://www.precisionfirearms.com/48m8/magazines/6-5-grendel-mags.html

https://www.cheaperthandirt.com/parts-and-accessories/parts-by-gun-model/ar-15/accessories/magazines/?q=grendel

[Bat Rastard]

https://gunmagwarehouse.com/asc-6-5-grendel-5-round-stainless-steel-magazine.html

[flatland1]

Lawrence97,

I've been shooting AR15s & bolt rifles chambered for 6RAT for several years, although I don't recall shooting at 100yds for group with any of the heavier bullets. All but one of my bbls were 24" long (the exception being a Bartlein 28" on a match rifle upper), and most liked Berger 105VLDs better than S107MKs. Just reviewed chrono data, and even in the 28" bbl, best velocities/best accuracy were with H4895 at 2750fps. I ran as much as 30.1grs of RL15, but that gave obvious pressure signs, at an avg vel of 2840fps. I used this upper in XC Hi Power matches, so max range was 600yds, and this is the distance I normally tested all my heavy bullet loads at. Since 600yd stage is slow prone, all the heavy bullet loads for this upper were seated w/o regard for mag length limitations, and single loaded with a SLED.

I have had good shooting with S95MKs (not the poly-tipped version), seated to mag length, mostly out of a 24" Krieger 1-8tw bbl I contoured & chambered for a series of practical/tactical matches, where all ammunition was mag fed. RL15 & Wolf SRM primers gave VG accuracy at just under 2750fps; I've seen these bullets perform pretty well with other powders, but believe RL15 gave best accuracy. Downside is that RL15 is temp sensitive. Even in a Howa Mini bolt rifle with a 24" Bartlein, I'm not getting significantly higher velocities, although this little rifle has shot consistently better groups at 600yds than any of the several AR15 6RATs I've built & shot. As you're probably aware, the RAT has the body blown forward about .700", and with reduced body taper & 40* shoulder, probably has from 3.5 to 4grs more case capacity than your 6 Grendel, so this is hardly an apples-to-apples comparison. Just wanted to toss this out there to perhaps mitigate your apparent disappointment with lower velocities than expected, if that indeed is the case.

[Javman]

You need to get the PRI modified mags!!!

[Javman]

You need these! Bought the ones for my 6.8 and have worked great in my 6.5GR.

https://www.cavitybackbullets.com/product-p/cb-pri-mod-5.56.htm

[A5BLASTER]

You need these! Bought the ones for my 6.8 and have worked great in my 6.5GR.
https://www.cavitybackbullets.com/pr...i-mod-5.56.htm

I can do the same thing to a grendel mag with a hacksaw, needle nose plyer's and a round file in 5 mints or I can do it quicker with the dremel and a cut off wheel.

[Javman]

I can do the same thing to a grendel mag with a hacksaw, needle nose plyer's and a round file in 5 mints or I can do it quicker with the dremel and a cut off wheel.

Tried that myself and found the mags weren't as sturdy.

[Lawrence97]