More cycling issues

[nathan197]

I have a 20 inch Odin works barrel and bcg and their "tuneable" has block, all of which is in an Anderson upper. I have gone in and used a dremel to polish my feed ramps. Sometimes I cycle ammo reliably, little to no failures to eject or feed. This has been with factory ammo using both elander mags and asc mags.( better results with the elanders). Today I was shooting reloads (129 gr interlock over 24.5g of imr 8208 with cci 450s). Out of 50 rounds approximately 35 times the next round did not cycle. The spent round was ejected but no new round. I had the gas block in a position that previous worked and locked the bolt back on empty but today could not get it to lock back. I have a standard carbine buffer and spring. The barrel does has a rifle length gas system. Upon adjustment I still couldn't seem to find a sweet spot that would lock the bolt back but it did eject the round. Could my load be so low on pressure that it wouldn't cycle the next round but eject the round? I started low since I had little data for the round. Hornady says max of 26.2 of imr but that's with small rifle primers not magnum. Frustrating because I really dig the grendel.

[grayfox]

cci 450 primers are the most-often used primers here for the Grendel as far as I can tell. I do have some 205M's but only for my bolt action. I have not shot any 8208 with the 129 class, but have done CFE in the 30-4-30.8 range, ~low 2400+ range for the 129 sst.
1. Did you try a ladder with 8208 or is that the only load. 24.5 looks mid-range so you ought to have some room to increase. I use the ladder to get a graphic picture of MV vs load. An initial ladder can be done via slow-fire, one round at a time, lowest load start then go upwards. this way you can usually identify issues before getting too hot. Take some time during this ladder.
2. How many rounds so far, many Grendel barrels seem to need about 50-100 rounds to break in. I had one that had cycling issues until I got to 50.
3. For initial shooting leave the GB all the way open. Once broken in and you have a load you really like, then tune (I do it by tweaking it down).

[nathan197]

I did not try a ladder with 8208. This was my first 50 reloads ever so I wanted to start low and be safe verifying all my previous steps were done correctly. 49/50 shot, one had a light primer strike. I could hear powder moving when I shook the round so I am not compressed at all and have more room for powder. I did make my C.O.L different for groups of 10 to see if a certain length feed better( none did with this charge) from 2.245-2.260.

I have about 180 rounds through the gun. 130 of them were factory (black, sst, federal begers). The last 2 outing before yesterday's (50 rounds combined) I had little to no failures cycling. Maybe 3-4.

I have had my gas block adjusted to what previous was working and since have adjusted it during yesterday's shooting but had no luck. I'll run it wide open the next time and let it get completely broken in.

Max charges I'm seeing are at 26.2 for 8208 but not with 450s. Maybe the next charge will be from 25.3- 26.0 or so.

[sundog]

I might be tempted to put 10-20 rounds over a chrono.

[BCHunter]

I had a similar experience with IMR 4198 and 95 v max. would not cycle the starting to mid loads. But would on the top end of the ladder. I would finish your load work up continue from 24.5 in 0.3 increments from where you left off. 3 to 5 rounds of each. Up to 26.0 if it doesn't cycle at the top end then I would investigate the rifle setup further. Also a chrono would help to compare velocity of factory to your loads. Would rule out a minimum velocity to cycle your firearm.

[nathan197]

A chrono is next on my to buy list. I may be able to borrow one at the range. I felt that my relationship reload felt way underpowered compared to a factory load. There was nothing at all that hinted to much pressure so I plan on doing a ladder work up and see if that helps cycling. I'm gonna get another box of factory ammo too and verify that it cycles still.

[VASCAR2]

I’ve seen AR-15’s which would eject the fired round but the bolt/carrier doesn’t move far enough to the rear to pick up the top round of the mag to start to feed. Most times this is because of gas leakage/insufficient gas or an under powered round. In a brand new rifle it takes more gas to cycle the action. A well lubed worn in rifle generally needs less gas to cycle than a brand new rifle. One of the advantages of an adjustable gas block is you can tune the rifle as it wears in, you change ammo or use a suppressor.

One other thing to remember is that different powders have different burn rates and dwell time. I have a 16” carbine length gas system 6.5 Grendel which will short stroke on 120-123 grain bullets loaded with CFE223 powder. The rifle has functioned with all other loads but apparently the slower burn rate CFE223 doesn’t build enough pressure in the short gas system to cycle. This same load has functioned in all other 6.5 Grendel AR-15’s I tested (7 or 8 other 6.5 G AR-15’s). Solution is I just don’t use that load in that particular 6.5 Grendel AR-15.

[Lastrites]

My sample of one Odin has about the nicest looking ramp/barrel extension that I've come across from a production barrel, surprised you had to buff yours. Beside whats been mentioned above I would also be looking at the bcg key fit to the gas tube and if the bcg is dragging excessively on the hammer. Also check to see if the face of the bolt is just forward of the back edge of the ejection port by 1/8" to 1/4" when manually pulled all the way back, have seen some odd ejection failures when the bolt disappears past the port edge.

[nathan197]

After manually cycling my bolt back I had 1/8"-1/4" showing. Ejection hasn't been an issue but it does seem to have the correct amount showing. I looked at the bottom of my bcg( which is black) and didn't see any major wear signs. There was a track down the middle that had some of the black finish slightly worn off from naturally pushing the hammer down but it didn't seem to be anything excessive. I did pull out my buffer spring and measured and it was 11 and 3/8" long. Online I found a site claiming carbine springs to be around 10.5 " and rifle to be around 12". (Maybe an odd ball midlength spring?) I swapped it for another that measured 10.5". Also noted that I have an end plate by the castle but with a QD point on it. The top of the end plate seemed to just barely (eyeballed it) stick above the lower. I figured this could cause the charging handle to be dragging across it and did seem 2 scuffs. I filed the end plate down with a dremel and now it does not protrude. I reconfirmed that my gas port and block line up. Odin works puts a notch in the barrel and block that line up and seem to be close to if not right on. I repined the gas block and confirmed the fit of the other end into the bcg. Everything seems to be doing what it's designed to do. It is currently reassembled with the gas block wide open and I am finishing my ladder work up. Hoping for good results this weekend.

Anyone used loctite 620 for their gas block? It's their "retaining" compound version so I was thinking it could create a better deal by the gas port/block. I was also thinking that if it needed extra sealing around it I might need a different gas block because I'm sure overtime loctite will fail and I'll be back to square one.

[VASCAR2]

I don’t think the Loctite will fail, I used blue Permatex on my gas blocks and have never had an issue. Normally carbon builds up over time to any leakage areas and eventually seal off. I don’t normally do mag dumps but I’ve had my rifles smoking hot a few times and never encountered my gas blocks coming loose.

I did have a Friends gas block come loose. He didn’t Loctite the threads on the screws or bed the gas block. I’m not sure he even remembered to tighten the gas block screws securely. I can now say I’ve fired a single shot AR-15.

[grayfox]

I use Permatex loctite, it's the 242 or "Blue" version, for sealing around the gas port and for the screws. I tried Rocksett once, BIG MISTAKE!!! never got that one off... Unless you're going full auto or getting it "smoking hot" that should be all you need. You can loosen blue with a butane lighter/torch or just some good twisting -- I recommend the heat though 'cause it won't strip so badly! The loctite's are color coded as to usage, torque and strength, you can google them and read up on them. I personally haven't seen any need for me to use anything stronger than the blue.

ps, you can speed up the cure by throwing the (all metal) upper into the oven at 175 *F for 15-20 minutes, that will set it up faster than just overnighting it... Make sure Momma doesn't care though just in case!!!