H4350 dpms lr-260

STI_1911_Guy

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Hey guys, i have been running H4350 in my DPMS LR260 right at 44.2 gr with the 123 amax and the brass is getting significant ejector marks. I do have an adjustable gas block (JP) set to just reliably lock open on the last round. I have read a couple instances where they say H4350 may not be the best choice for a gas gun, is this true? Or are my loads on the higher end? Or what are some of the loads everybody runs with the 123 range bullets? I can obviously drop back down however accuracy is much better above 44, im not sure how far down i would need to go to get to the next node but i would like to drive the bullets a little faster than 2800 ish, and currently my chrono says right about 2890-2920.
 

Ledzep

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    Is the gas block made of aluminum?

    I had a JP adjustable gas block on my LR260 and after adjusting the gas down to cycle how I wanted, the gas ate through the aluminum around the screw and opened it back up. YMMV.

    I was loading 140 Amax's and with light loads it would blow gas around the primer (etched a ring in the bolt face), with heavy loads it was ejector swiping. There was a very narrow band that I could use that would not wreck something.

    Long story short, I sold it and gave up on using "semi-auto" and "precision" in the same sentence. Life is much simpler now.
     

    Blazin

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    Thebelly

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    significant ejector marks could mean you're getting to the edge.

    What is the rest of the load data?
     

    STI_1911_Guy

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    What kind of velocity are you getting with 43 grains? And the lowest i have gone is 43.5 with the same results. Ideally i wouldnt like to go lower but i may need to. Here is what hodgdon says
     

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    verdugo60

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    Are you shooting 123 Amax's though? Heavier bullet obviously=more pressure w/ same powder charge.

    Based on my experience with several 260s, 44.2gr of H4350 is real hot. My H4350 loads max out in bolt actions at 42.8-43.0.
     

    morganlamprecht

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    Based on my experience with several 260s, 44.2gr of H4350 is real hot. My H4350 loads max out in bolt actions at 42.8-43.0.

    most everyone i shoot with runs 43-44 grains under 140s...OP shouldnt be that hot with 123s...my DPMS LR 6.5 creedmoor leaves swipes on every factory ammo and reload ive shot thru it
     

    supercorndogs

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    pressure = velocity looking at the hodgdon data and your chrono data ses you should be over pressure if you are getting 2920 when you should be at 2860 unless you are using a longer barrel than they did. if your gun leaves swipes on everything there is something wrong.
     

    FALex

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    I'm running 41.7 of H4350 in my 22" LRP with 139 Scenars. Sure, the velocity is not there, but the thing shoots straight as can be and functions reliably. The impact on brass has been negligible thus far.
     

    pby5cat

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    Im shooting 41.5 H4350 140 AMAX out of a 24in 6.5 creedmoor DPMS LR type. i get ejector swipes and primer flow on that recipe and hornady factory ammo. using some ones crono i got 2660 AVG from my gun.
     

    DT1

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    significant ejector marks could mean you're getting to the edge.

    What is the rest of the load data?

    Good question. OP, what is your COAL? If you have the room to load your rounds a little longer, even a few 100th's, it could relieve the pressure on the brass.

    44.2gr of H4350 is definitely on the warm side for 123's in 260. John Paul (JPE) will be the first one to tell you that gas guns are generally not the best platform to experiment with max loads in any of the 6.5mm or 6mm cartridges. Too many things going on with the pressure/cycling equation.

    If you can't load a little longer, try backing off a couple of 10th's on powder until you're comfortable with how your brass looks. If you can't get the results you want with H4350, you might try working up a load with H4831SC. It is a slower powder that can produce good results with 6.5mm cartridges. Good luck!
     

    jh26

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    With H4350 I would agree getting close to the edge. In my DPMS .260 I run it on the low side, but very accurate. With RP brass and 123 scenar's, 42.6 2750-2775. I also shoot 140 smk's and 140 Amax's with Lapua Brass [email protected] The 140's ended up being more accurate than the 123, but very slight difference. Both have faint ejector marks. As far as H4350 in a gas gun, been running it for 3yrs, both me and my brother never an issue. I have also read where folks think its a bit slow for a gas gun and run varget or H4831C. I just never had a reason to try the others.
     

    STI_1911_Guy

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    2.808" overall is the length. Not really any room in the mag at that point. I did try backing it down and at 43.8 i am not seeing nearly the swipes i did. I did have to open the gas block a little to get it to lock open on the last one. I have not checked velocity yet.
     

    Thebelly

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    I use 41.0gr of H4350 and get 2700fps with the 120 AMAX loaded to 2.804"

    I think your charge may have just a little too much stank on it.
     

    Fly_True

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    I'll echo others so far but 2900 range is pretty hot for a 260 running H4350. What length barrel are you running in your setup? Likely be wise to drop down a node or two until you have no preasure signs at all. Not worth burning the barrel up or shortening brass life span for a few extra fps.
     

    SharpsNitro

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    Try Varget if you can, the faster burn rate should help. That's where I ended up when I was developing loads for my 6.5CM MATEN.

    Edit: The highest I went was 39.0gr of Varget with a magnum primer pushing the 123gr Amax, accuracy seemed good. This load gave around 2825fps and showed swipes on about 30% of the cases that were big enough that a burr was starting to develop, this was better than anything H4350 gave me, the burrs were much worse with that powder at lower velocities. The 140gr Amax looked like a non-starter, the Hornady factory loads had severe cratering and burrs.
     
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    LRRPF52

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    Based on my experience with several 260s, 44.2gr of H4350 is real hot. My H4350 loads max out in bolt actions at 42.8-43.0.

    I was thinking the same, depending on the brass being used. I'm pushing pretty hot loads at 41.0gr of H4350 with the 130gr VLD, and that was with Winchester 7mm-08 brass necked down, which has a lot more case capacity than Lapua brass.
     

    Ledzep

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    Do y'all crimp your rounds. If not how do you keep them from hitting the rifling?

    Most target bullets lack a cannelure, so I'm not sure exactly what positive effect crimping would have. I would be afraid of damaging the bullet if you crimp too hard.

    Either way, I played pretty extensively with this in my 6.5 Grendel AR-15 recently. I tried using .002" of "neck tension" with redding S bushing dies, and I tried with .004". I ran 10 rounds of each through a magazine with 3 rounds above them, measuring before they were loaded, when they were "next in line" to go into the chamber, and after they had chambered. There was no difference discernable difference in any of the numbers.

    I was using Amax's, so in the magazine the polymer tips crushed about .005", then when chambered, the bullet moved forward about .008" from original. I was seating them about .010" off the lands and it was very often that they would touch the lands and spike pressure. My solution is just to put them .025" off of the lands. No more pressure spikes.

    Then the "No shit" moment hit me. Chasing lands in a semi-auto is stupid.
     

    lte82

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    I shoot 139 scenars out of my 24" Dpms lr260 @ 2750 using 2000mr. It's closer to varget burn rate wise and pretty soft on brass. H414/H4350 speed powders were popping holes in primers when I got near max.

    For what it's worth, Sherri Gallagher won a national championship at Perry with a 260 rem using varget and 142 smks. Don't fear the faster burning powders.
     

    Thebelly

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    . If not how do you keep them from hitting the rifling?

    I load a tangent-profiled bullet (123gr Nosler CC or 120 AMAX). This allows me to seat off the lands where the gun likes it and still maintain an OAL that fits in a PMAG.
     

    kyhuntclub

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    My fathers DPMS LR-260 shoots great at 41.0 grains of H4350 with 120 SMK. My opinion is your pushing the edge and you should try to find a node on the bottom side.