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What Length barrels would you like offered for this caliber?

What Lenght barrels would you like offered for this caliber?

6551 Views 27 Replies 16 Participants Last post by  MickeyC
Alex, of Robinson Armament, was asking in a thread tonight what we users would like to see offered in the way of barrel length. I have started this poll, (and I'm still in awe that we get to give feed back to the maker of our firearms system) so that we can let Alex know exactly what we want, and how we want it.

You can have up to 3 votes in the poll, and please don't vote for the same thing 3 times. We need a true reflection of what we want.

So, that being said, have at it!

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I view the 6.5 as a long range cartridge, so I would opt for the 18.6" heavy fluted myself. I don't know much info on 6.5 ballistics yet, so I don't know how it performs from 16/18/longer barrels-but I would tend towards the longer barrels.

Anyone wanna post some info on the cartridge?
Good info there... That was with 20" barrel so I'd assume the longest xcr barrel would be best to keep the round's advantages intact...
18.6" (or more...) and heavy. I still consider this chambering as a .308 substitute and want ballistics as good as possible for 600yds. or more.

Make it long and (reasonably) heavy!
I'm not sure that this would replace the .308. I guess I'm biased as I have been shooting .308 for 20+ years and I know what it can and can't do, if you know what I mean? Still I'm open to change, for the better that is!
it won't replace the good old 308, but it does give you results that are close without the recoil and weight penalties of the 308. reasons given for changing to 5.56 was the ability to carry more ammo with the same weight as the load out for 7.62 although you would lose penetration at longer distances. since jungle fighting was all about short ranges, this was considered an acceptable trade off. the 6.5 and 6.8 are both a step up from 5.56, but neither are going to be as good at some things as the 308. just my 2 cents. YMMV.
Some of the guys I know in the Australian SAS used to say: "with the 308 it was One Shot One Kill, but when the went to 5.56 they said One Mag One Kill"
The Grendel isn't a super round that can meet all mens needs all the times.....alas.... :D

What it is, is a round with a good and high Ballistic Coefficient meaning that it can stay stable and supersonic out to 1000 mtrs.

One of the drawbacks, at least for short range ( 0-300 mtrs) is that due to the stability, tumble and yaw is inherently minimised..... :'(
The Wolf soft point ammo may well help to obviate this, would be interesting to see a "Box O'Truth" testing for this.

Now you can get the 6.5 round in a wide range of weights from 90gr to 130+gr and the round responds well (according to the www.65grendel.com folks) in a 16" barrel with retained energy in the 500 ft/lb range at about 900 yards.

To sum it up, this is not a direct 1:1 replacement for the 7.62 NATO but allows you to carry similar ammo loads as a 5.56 with near to 7.62 NATO peformance in the same XCR platform as our 5.56's. One additional advantage is that optics ballistically calibrated for 7.62 NATO are a nie on perfect match with the Grendel.

I do see this as a round that will also lend itself to handloading and tweaking quite well.
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a quick note about handloading the 6.5 grendel. there have been some issues about the bolt breaking in the stoner designed action in ar15's because some people were pushing the envelope of the grendel cartridge. please be careful in your workups, follow posted limits and tables. if loaded within acceptable limits, the grendel is a sweet little round. if you push too hard, the results could wind up in your face. i know, i know, some of you will say the design of the XCR is so much stronger than the ar15 that you can get away with a "little more." don't do it. the end result isn't worth risking life and limb.
Hey Guys,

I will close voting on this topic next Sunday night so that I can relay this information back to Robinson. So, if you haven't voted yet, get in and vote because this may be your only say in barrel lengths for this caliber.

Thank You!

Link to Alexander Arms data on ballistics and barrel length over a range of 4 different bullet types and weights. Doesn't include the Wolf ammo, still trying to find the data


Should help people to decide on length based on their personal needs
2 XCRs in the safe.
more on that at a later date.

I've got 4 Grendels.

24", 19.5", 20" and a 10" pistol in Grendel.
Over 1000 rounds downrange with MANY bullet types.

I used the 24" to take a cow elk 3 years ago (at the time, I only had the 24").
The 19.5" will give 95%+ of the velocity of the 24" for most (useful) bullet weights.

There is plenty of reload and performance data on the 65grendel website for many
bullet weights and barrel lengths.

I plotted bullet velocity vs barrel length for most bullet weights, and I found the
"knee" in the curve at the 18-19" barrel length, indicating that the optimal barrel
length would be ~18-19". I can post this plot if anyone is interested (and I can
find it again!).

Remember that the Grendel case only holds about 30 grains of powder and exceeding
50,000psi is a big no-no for the Grendel, particularly in an AR-15. Shooting anything
greater than ~130 grains yields low velocities. This varies by bullet type & construction,
etc - but generally speaking, the Grendel shoots lighter bullets best.

This brings me to the XCR-M. Is there an option for a .260 barrel? The .260 will
launch 130+ grain bullets with better ballistic performance than the .308 with much
lighter recoil.

In short, I'd love to see an XCR 6.5 barrel by hunting season. Who can I bribe to
make this happen? ???
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18.5 barrel would be excellent. Maybe a heavy fluted profile.

Am very excited about having this option for my XCR. Already own one Grendel, so I've got some mags and a bunch of ammo already. It is an excellent round. Accurate and offers performance nearly as good as 308 in a smaller, lighter, softer recoiling package. Although ammo can be hard to find an pricey, there is decent quality Wolf that is somewhat reasonable in price.

thanks for the input. I haven't had anything to do with this round. I have used the 65. x 55 in the past and it was a flat, fast shooting round but as you said ammo was a problem.

OK guys and girls, just a reminder to cast your vote before midnight on Sunday as I will be closing the vote and giving the results to RobArm. So far it seems like not too many people are interested in voting. How are we going to convince Alex that this is what we want unless we can give him some good figures. I think only around 13 people have voted to date, so get those fingers moving and make you vote count. This might be a last opportunity to influence this weapon design at this level.

It's your choice. "Do it, do it now" ;D
To Aussie Arms and the rest. Thanks!!!

I want to get some 6.5 barrels ordered this week with hopes of having them here before Christmas.

I'm thinking I'm going to do a run with the 18.6" barrels. Possibly (and I mean Possibly) in Stainless. Heavy Profile but not fluted. Because of the larger bore, they're not so heavy. In this way I can cut them down to 16" with no problem for those who want the shorter barrels.

I may be able to get them fluted but it would be hard to cut them back to 16".

I'm not sure I can do the stainless or not. They may be chromemoly.

Anyway, I need feed back on the following also:

For 6.5 do you prefer chrome lining, stainless, or chromemoly? I need to place and order in the next two days.


Alex Robinson
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I'd be all for chromemoly. Stainless simply isn't necessary. I can take or leave the chrome lining. If they have it, great. If not, no big deal.

18" and heavy, though, I'll be all over that.
Order of preference based upon my expected use, long range target, relatively light usage, cleaned well after use, mostly range not brush usage.

1. Stainless Steel Most accurate, easiest to clean
2. Chromemoly Almost as accurate as SS, needs more care and attention, wears quickest
3. Chrome lined Least accurate, longest life, least erosion

With good barrels, variance in accuracy should be small-ish.

Would prefer the 18.5, would like fluted but not too worried.

You are most welcome. I would be all over a Stainless 18.6 for my Christmas stocking.

I like the idea of fluting and durability of the chrome lining, but I don't have strong feelings about it. Basically, I'd be happy with an 18.6 inch "whatever" in 6.5.

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