Be careful with LeverEvolution - broken extractor

[grendelnubi]

So far I have only used LVN in my RAP with awesome results. Generally getting on average 100 fps faster than using my developed loads for my AR's. Decided to try and do a load workup for my Odin Works DMR 18" using Hornady 129 Interlocks and LVR.

I need to give you a little back history. The first load I ever developed for this 18" was using AR Comp and the 129 ABLR which was my hunting load for several years. They would run about 2350 fps with 26.9 grains of ARComp. I noticed however, in colder temperatures, I would experience short stroking, so I opened up my gas block 1/2 turn and problem was fixed but when using other loads and different powders, it was generally over-gassed. I believe this could have contributed to my problem I am sharing with you today.

I started my 129 Interlock and LVR load at about 29.5 in .3gr increments. Temperature was 70° that day. I was watching for pressure signs and everything seemed to be OK. I never planned to shoot the 31 grain load but I did not see any outstanding signs of pressure so I continued and shot it.

First 31 grain shot was only slightly faster than previous 30.7 but I noticed a double feed. Also my brass was not in the brass catcher.......... I pulled the mag, removed the double feed and discovered the shot round still in the chamber. After cycling a few times I removed the BCG and noticed a broken extractor. I was using a JP bolt.

I guess I must have pushed it a little too hard. LVR is sneaky and its such a slow burning powder, pressure signs can be hard to see. Be Careful with it.

Went ahead and purchased a couple extractors from SixFiveOutfitters and I'm back on the road again!

BTW, thanks BFT for everything you do! Both of these new web sites are awesome!

I will do more testing with the 30.4 grain load.
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[VASCAR2]

Being over gassed can contribute to extractor wear which I encountered on a 16” carbine length gas 6.5 Grendel. If the receiver face is not square with the bolt this can contribute to uneven bolt wear and reduced extractor life. I have a friend with a lapping tool and lathe and I have him check all my upper receivers before assembly.


I read where there was a temperature test conducted on AR-Comp powder. To my surprise the pressures increased with colder temperatures with AR Comp powder. At higher temperatures AR Comp was more stable. This is the opposite of ball powders like LeveRevolution, CFE223 and Accurate 2520. AR Comp is manufactured in Sweden and even at lower temperatures the velocity increase wasn’t as much as the change in velocity in temperature from zero to 110 degrees with CFE223. Normally I test ball powders at the hottest temperature I’m likely to shoot, mid to high 90’s to see if they are safe. Normally ball powders are safe at cooler to cold temperatures than what I tested in the 90’s. I have AR Comp which I have yet to load but I might test it in colder temperatures when I do my initial test.

The colder temperatures might have increased the pressure of the OP’s load which in turn can affect the dwell time and cycle timing.

[LRRPF52]

What’s your gas system length? Is it the Intermediate Length Odin uses? That should help prevent this from happening.

It’s funny that over all these years, I have never had an extractor or bolt break, and I shoot Grendel a lot.

My go-to bolts/extractors are the Monster logo and Rexus models over the past 7 years, but I’m still shooting my 17.6” with a Maxim bolt I got from Precision Firearms.

I’m using Bootleg Adjustable Gas bolt carriers to keep my cyclic rate under control and preventing early extraction/unwanted torsional loads on the lugs and extractors.

[Klem]

Those are hot loads for LVR and that bullet, even at a long OAL like 58mm.

I have not used this powder but would not go over 29.5. Unless you are OK with changing out parts if something breaks (I am being serious here, I carry a spare bolt in the buttspace).

They are also compressed loads - all of them.

[grendelnubi]

It is the Intermediate Length that Odin uses. I realize it was over pressure now, hence the warning. LVR does not exhibit the typical over pressure signs typically seen in my setup. IE... once I see an ejector and extractor swipe, I do know to stop. Flatten primers are pretty typical.

One of the first things I do when starting load development is check the load density for that specific powder, relative to the seating depth of the projectile I am using.

In this instance using a 129 Spire seating depth of 2.21 (1.702), at 100% LVN charge weigh is 30.3 gr. using Hornady brass. So at 31 grains, my case fill was 102.3%. Not really too compressed, but yes compressed. Not near what I run my AR Comp loads to which is typically 110% of power fill.

[LRRPF52]

Here’s Hodgdon’s published load data for that powder and bullet:

Hornady 129gr SP, Hornady case, Fed 205 SRP

Hodgdon

LVR

2.245"

26.0

2,268

42,500 PSI

29.0

2,468

50,000 PSI

[Fess]

It is important to know that you can't use typical pressure signs do develop loads with the Grendel for AR15's. The Grendel's SAAMI max pressure of 52,000psi is set that low to prevent bolt damage with a standard sized AR15 bolt*. By the time you seen pressure signs, the pressure is high enough to damage your bolt, although the extractor often fails before you lose a lug.
With other rifle designs that have stronger bolts, you can run higher pressures. The 6mm ARC is related to the Grendel, and Hornady publishes two sets of reloading data: one set for "gas guns" at 52,000psi and another for "bolt guns" at 62,000 psi.

*There are some beefed up bolts with a larger outer diameter, like the CMMG Mutant bolt, but they require a non-standard barrel extension.

[LRRPF52]

You can beat LVR with CFE223 under a 129gr and do it with less chamber pressure as well.

129gr Hornady SP

Hodgdon

CFE 223

2.245"

27.4

2,263

39,900 PSI

30.3

2,495

49,600 PSI

[grendelnubi]

I tried CFE223 with the 123 SST and I can't run anything hotter than 30grs without extractor and ejector swipes. It shot really accurate but don't care to tear my brass up so I stopped with CFE. With this 18" platform, out of the 123 SST loads I have, 8208 is the overall velocity winner, and AA2520 is a close second. I seem to have an accuracy node about 2400 fps with the 120-123 grain projectiles so that is where I usually end up.

The main reason I have alerted everyone of the risk with LVR is the fact that (in my experience) it does not exhibit traditional pressure signs, whatsoever, outside of flat primers which I have came to expect with the Grendel.

[mulyhuntr]

I tried CFE223 with the 123 SST and I can't run anything hotter than 30grs without extractor and ejector swipes. It shot really accurate but don't care to tear my brass up so I stopped with CFE. With this 18" platform, out of the 123 SST loads I have, 8208 is the overall velocity winner, and AA2520 is a close second. I seem to have an accuracy node about 2400 fps with the 120-123 grain projectiles so that is where I usually end up.

The main reason I have alerted everyone of the risk with LVR is the fact that (in my experience) it does not exhibit traditional pressure signs, whatsoever, outside of flat primers which I have came to expect with the Grendel.

I've found that cfe223 and LVR run nearly identical velocities at the same powder charges. Things start to get a little hot (mild ejector marks) at 31gr of each with starline brass, cci450, and 123 eldm. 60 degrees. LVR is consistently more accurate in my rifle.