6.5 LRM



  • I've been working on a fun project lately!

    6.5 LRM

    Guys have been having great fun with 6.5SAUM, but those tend to not feed very well out of unmodified DT magazines. So in response, I wanted to find a good candidate in the 6.5 magnum variety for DT users. We've chambered a few in 26 Nosler, and they've been absolute hammers. I think if someone wanted a turn-key hardcore 6.5, the 26 nosler is probably the go-to in a SRS or Covert. However, all that speed comes at a price. There is no denying that the 26 nosler is a barrel burner.

    I'm running a 30" 8 twist TS Customs barrel with heavy contour. I have this same configuration in a 7LRM barrel.
    geKomJgh.jpg

    I start out with factory Gunwerks (hornady) 7LRM headstamp brass. Upon close inspection, the neck has about .0015 to .002" of brass thickness taper from the neck/shoulder junction to the top of the case mouth. That's quite a lot of thickness variation that I didn't care for, so I got a batch of brass turned to .0145"-.0150" uniform thickness. That gave me a barely measurable uniformity variance from shoulder to mouth of about half a thousandth with the necks around 80%+ cleaned up. Some cases were absolutely horrible... but given the very proprietary nature of this cartridge, I can forgive that. Runout on the case mouth ran from .0015 to as much as .005" with most of the cases being in the .002-.003 range.

    Sadly I don't yet have a FL die for the 6.5LRM, so I used a 7LRM bushing die to size the necks. This unfortunately left the case largely unsupported, which induced as much as .008" of runout with an average of about 5 thousandths. After scavenging a 6.5mm expander I was able to get that down to about .003 which isn't the end of the world. On the turned brass, a .291 bushing turns out to be the right stuff. I stepped it down in two op's, with the first pass at .305 and the second pass with the .291. I think 3 passes with smaller steps in diameter would have helped with the runout issue. The 7LRM brass starts off at about .315 to start with... so going to .291 is a 24 thousandths squeeze and I usually don't like to take bigger than about .008" steps when sizing down without a custom FL die. In any event, I cruised through that discovery process and got a sizing method down that was acceptable.

    First I went to work with 140gr Berger VLD's. I was met with dismal results. I threw everything but the kitchen sink at it. Over a hundred twenty thousandths + of seating depth, 4 different powders, neck tension... on and on. Nothing would get those picky VLD's to behave. Then I grabbed some Berger 140 Hybrids... and boy oh boy did it come alive. Quarter MOA groups and better, and it really didn't much matter where they were seated or what charge weight of whatever powder I tried. I settled on a BTO of 2.720", putting me about .010" off the lands. H1000 seems to be a winner.

    GYSumzkh.jpg

    Here are some velocities at varying charge weights:
    H1000 velocity
    62gr - 2895
    64gr - 3040
    66gr - 3108
    68gr - 3190 - pressure just starting

    IdLfEcph.jpg

    It isn't as if this cartridge will be creating a revolution like the 7LRM has done, although it is certainly a neat option for folks looking for something a little different than the available offerings. So far I seem to be settled in right around the 66gr mark, but there's more work to be done. I've got just over 135rnds down this barrel, so it will be interesting to see what goes on with velocity as things settle in. Feeds like a dream in my DT SRS-A1 and gives me some solid performance with the expectation of reasonable barrel life.



  • I like the idea of this round...but it does not appear to remain super sonic any farther out than the 7LRM...and I will bet it burns barrels faster than the 7 LRM as well. Is my assessment correct or am I missing something?



  • You're pretty well locked on I think. It's basically equal to the 7lrm in terms of both wind and drop, though it gives up energy, which also means it recoils less. The 6.5lrm is a little flatter to a grand. About .2-.3 tenths is all. They are identical in the wind. 6.5LRM has about 300ft/lbs less energy at 1000yds.

    Less recoil is nice.



  • I'm doing the same research for a LR hunting build as I mentioned in @dddoo7 s "which barrel thread." So far I think I'm settled on what I want to do, but I'm throwing this out for the consideration of the group.

    What about a 6.5 SAUM? Allegedly those have good barrel life (3000ish according to GAP) due to lower pressures and can push a 140 around 3100 fps from a 24 inch barrel.

    Only downside I've heard of is they can be funny to feed in a standard rifle. Not sure about a DT system.



  • @ragnarnar

    I've got a friend building one...but is not far enough along to know what it will do.



  • Maybe If someone would come out with a heavier match grade bullet this might be worth it.

    Something like 155 or 160 grain with a g1 around .7

    I doubt there is a lot of demand for that though.



  • Short mags don't feed well at all from DT's. I take a call a week at least from guys that were sold one by some other company and can't get it to work. ... yet those dumb assholes continue to sell them and continue to say how awesome they are online. Oh well, I get those customers eventually.



  • @rhyno said:

    Maybe If someone would come out with a heavier match grade bullet this might be worth it.

    Something like 155 or 160 grain with a g1 around .7

    Matrix has a 160.



  • @orkan looks like Matrix has been sold, nothing on their webpage. Never knew about them



  • Well I'll be darned. They had some fairly good bullet options.



  • I looked into this when I was going back and forth on SAUM or LRM

    It seems that they're going to reopen for business shortly according to their website.



  • Be curious to see what the new Hornady 147 ELD-M will do out of this.



  • Playing devil's advocate...It seems that for a great deal of powder the speed increases are marginal. For example, I can shoot the 142gn Nosler ABLR out of my 6.5x284 out of 26" barrel at around 2980fps with 49.5gn of Hyb100V. With a little more than 16 additional grains that load only gains 130fps in speed. I know you are using a different powder, but 66gn is a lot of powder for a 6.5mm bulelt. My 6.5CM shoots the 123gn AMAXs at 3050 with 44.9gn of H4350. I guess I was expecting to see a much more significant gain in speed with all that additional powder and the 140gn bullets. I guess I am not seeing a significant benefit out of that caliber and load. Just my thoughts.



  • When I get adequate rounds through this thing for it to stabilize, I'll give a report on the final velocity. It was still building FPS last time I shot it.

    My go-to big 6.5 is the 26 nosler. The only justification I needed for this project was that I wanted to do it. All other concerns were secondary. This project was not a quest for efficiency. It was a quest for knowledge, as is the case with most of my work. We can continue going down the line, arguing that it's not beneficial to have so much powder. 26 nosler to 6.5x284 to 6.5 creedmoor to 6.5 grendel. That doesn't change the fact that every increment you move up, it gets flatter and better in the wind. Suffice it to say, your 6.5x284 is never going to approach the speeds I'm getting from the 6.5LRM... no matter what you do.

    Given statements I've previously typed like this: It isn't as if this cartridge will be creating a revolution like the 7LRM has done

    ...what exactly is there to be a "devils advocate" of? Doesn't someone have to advocate before you can be a devils advocate?



  • @orkan No worries Greg, I did not mean to come off the wrong way. I was just offering some thoughts on the results so far. If you are doing this to gain knowledge, more power to you. People like me that are here to learn have to ask question and offer thoughts to learn as well. Since the reasons for doing the project were not stated, I made assumptions thinking you were after a speedy, flat shooting load, hence my thoughts. My bad for that assumption.



  • @ramirojpc said:

    Since the reasons for doing the project were not stated, I made assumptions thinking you were after a speedy, flat shooting load

    5.7 mils to 1000yds. That's pretty damn flat.



  • My custom whidden die set came in, so I started working with the 6.5LRM again today. I was hoping to be able to take the turned 7LRM brass down in one shot, but early attempts failed miserably. I was seeing .015 to .020 of runout. Absolutely horrible. I tried every trick I knew. Nothing made it significantly better. So, I came up with a new trick.

    I ran the expander mandrel way up inside the die, leaving just enough room for the neck to get around to be squeezed down. Then I would raise the expander up until it made contact, and then retract the case, expanding the neck. By doing this I was able to get the runout down to .004-.008 and size the brass in one shot. Didn't take long at all once I got it worked out. Lots of "feel" involved there. ;)

    25DGB4Qh.jpg

    I never fully commit to a process without completely validating it however. New dies always take quite a few cycles to completely wear in and you can never trust if the dies are correct until they prove themselves. I needed to confirm if this runout was going to stay, or get worked out through fire forming. Fired brass showed .003 or less, and after running it through the sizing die again brought it down to less than .001. After that little test I was confident enough to go through the rest of this batch. Got them squeezed together in short order once the brass work was done.

    25mDZDmh.jpg



  • @orkan I like this. Using the expander mandrel to aid in alignment at the top of the stroke. Kudos!



  • Just got to be careful when doing it, or bad things may happen....


 

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