Is my 6.5 grendel over gassed

[Jtod]

Hello, new to the forum, new to the 6.5 grendel.
I put together a 6.5 grendel with a

16” liberty barrel(carbine length gas) and came with a bolt
Non adjustable gas block
Carbine spring and buffer

Took it out shooting today and tested
123 sst with cfe223.
The loads ranged in .3 grain increments starting at 30.9 and up to 32.5
All loads ejected about 4-6 feet away and at 1 o’clock. All brass had a nick where the extractor holds the rim. Not a horrible nick, but noticeable. I’m wondering if any of you guys can help verify by the info I gave if it sounds over gassed. I think it is. If it is over gassed, what’s the best solution? Heavier buffer?, heavier buffer and spring?, or just get an adjustable gas block.

[A5BLASTER]

Try a heavier buffer and see what it does.

Only change one thing at a time and test it before you change something else.

[Jtod]

Will do, and thank you for the reply. Your advice makes much sense.

[Jtod]

Wow! I just finished cleaning my rifle and thought the buffer was sitting a little funny in the tube. I removed it and it is in 2 pieces. The threads from the body to the head are stripped. I’ve never seen or heard of this before. I think I’m going to put a functional carbine buffer in it and try that out before going to a heavier buffer.

[VASCAR2]

Your CFE223 load is over max according to my Hornady manual. I’ve never seen many people get over 32.0 grains CFE223 with a 120-123 grain bullet. I get factory equivalent velocity with 31.0 grains CFE223 and CCI450 primers with 123 grain bullets with Lapua/AA or Hornady brass. Hornady manual max load is 31.2 grains CFE but that includes a 120 grain GMX monolithic bullet which usually produce more pressure than cup and core bullets like the 120 or 123 grain A-Max.

I’ve read on other forums where people have expirienced defective carbine buffers. If I were you I’d check and see if your ammo sticks in the lands of the barrel. Loading bullets jammed into the lands can spike pressure. Unfortunately short chambers and short throats are not uncommon with the 6.5 Grendel. Just something to aware of.

[Jtod]

Yes, I have the Hornaday #9 and 10. I did realize that my loads are over book max, but like you said the gmx bullet is included. I was trying to push towards an initial pressure sign so that I would know where it was at. Never did see any pressure signs all the way to 32.5. According to my measurements with the Hornady COL tool I don’t hit the lands until 2.330. I can only load to 2.265 or so, but the ammo I used today was at 2.250 so it should have had to jump 0.080”.

[Klem]

According to Quickload the pressures at 32.5gns CFE are;

2.25"OAL, 65.670 lbs peak pressure.
2.65" OAL 63,748lbs
SAAMI for Grendel is 52,000lbs.

It's not a lot above SAAMI and QL is conservative but to be fair it is hot.

Pressure signs are subtle and by then it is too late. You are doing incremental damage to the gun until something obvious fails, like a bolt lug. Your buffer might be the canary in the coal mine.

[Jtod]

Ok, thank you guys. I normally push towards the first pressure signs like flat edges on the primer or where it just begins to crater the primer in the firing pin hole on everything else I’ve reloaded so that I can set an upper limit 1 grain below that. Maybe the grendel is different in this aspect and won’t show pressure signs? The 16” barrel I got from satern is running 2360 FPS at book max load with cfe223, It seems a little bit slow.

[Lastrites]

Post a photo of the broken buffer, never heard of one that had threads/body screwed to the bufferhead, less we are talking about the receiver ext.

[Klem]

Ok, thank you guys. I normally push towards the first pressure signs like flat edges on the primer or where it just begins to crater the primer in the firing pin hole on everything else I’ve reloaded so that I can set an upper limit 1 grain below that. Maybe the grendel is different in this aspect and won’t show pressure signs? The 16” barrel I got from satern is running 2360 FPS at book max load with cfe223, It seems a little bit slow.

Jtod,
I have to say that's a dangerous way of determining a safe load in a pressure vessel. I recommend sticking with internal ballistics programs, loading manuals and online powder charts (better still, a combination of all three). Clearance around firing pins and different primer thickness/hardness will give you false comfort until something gives. Even at one grain less than what you think is too much you might still be hammering your gun to pieces.

[Jtod]

Roger that Klem. So far I’ve loaded for 30-06, .270, 308, 5.56, 277 wolverine and a few more and haven’t had any trouble detecting pressure signs. This Grendel never even showed flattening of the primer. I do think I was treading into dangerous territory though. On the buffer, it was a cheap carbine buffer with no roll pin holding the buffer tip. I’ve since scoured the internet and found many instances of failure with those cheap buffers. I think mine came unthreaded, however on a proper buffer the head is not threaded to the body. I’ve replaced it with a mil-spec buffer and shot the rifle today with 31.2 cfe223/123sst @2.250” and still had dents in the brass and 1 o’clock ejection even with an H buffer. I may try an adjustable gas block. The good news is the group size I’m getting is ridiculous. .425” 3 shot groups that only have 2 visible holes. I don’t really plan on shooting other bullets than the 123 sst, so I’ll most likely just get an adjustable gas block and set it and forget it.

[Klem]

Obviously the 1 O'clock is too much pressure in the gas system. That does not necessarily mean the loads are too hot however, you may be OK. The case dents are also not necessarily a sign of over-pressure and is fixed by cutting a couple of coils off the ejector spring. I agree, an adjustable gas system will give you control of that gas at the source.

Those other guns you reload for are mostly bolt guns, yes? In that case you can be fairly cavalier about pressure given good quality/reputable receivers can take more than SAAMI. We used to deliberately overload Rem700 actions to reach 1,000 yards with .223. Those receivers took the punishment without a problem. In that situation the brass is the weakest link and you see signs of overpressure with flat primers and hardening of brass but without damage to the rest of the gun. In an AR we don't have that luxury. It's a flimsy, light-weight receiver with smaller bolt lugs. Overpressure will break bolt lugs before it shows up on brass...Just saying.

[Jtod]

I appreciate the info Klem. I need to adjust my attitude towards the AR platform. Everything I’ve ever loaded with exception to the .270 shot best under max. I think I’m just trying to push this 16” grendel barrel to do something it isn’t going to do. I had a lofty goal of 1000fpe@400 yards.
Quick question Klem, I have 8208xbr and cfe223. So far I’ve only loaded up cfe. In a 16” barrel, which one is more likely to produce highest velocity with safe pressures? My barrel has the Grendel II chamber. Thank you,

[Jtod]

I tried to upload a photo from my phone and keep getting a file size too large error. The buffer I had screws together where the head meets the body and doesn’t have a roll pin thru the buffer tip. I’ve looked at a proper buffer vs the one that broke on me and the difference is very obvious. I’d suggest only a 1 piece buffer body tube with roll pin thru buffer tip

[Jtod]

I went out today with 123 sst loads with XBR8208 and an H buffer. They ranged between 27.2 and 28.5. I am happy to report that I’ve reached my velocity goal between 28.2 and 28.5. The gun feels smoother with that powder too. I’ve also located the source of my dented cases. It is coming from where the ejection port transitions to the deflector. I’m running an aero upper and it has a 90 degree squared off sharp step between the two. All my other uppers have a rounded transition. The XBR powder has also cut the denting down to a minimal amount. For now I’m happy. In the future I may take a look at smoothing out and repainting that transition to the deflector. Sorry that I can’t upload pictures.

[VASCAR2]

All my 6.5 Grendel brass get a small ding/dent in the side on ejection. Has never been an issue and is very common. You can shorten the ejector spring or put a piece of loop velcro on the deflector to lessen dings to brass.

[Klem]

I had a lofty goal of 1000fpe@400 yards.
Quick question Klem, I have 8208xbr and cfe223. So far I’ve only loaded up cfe. In a 16” barrel, which one is more likely to produce highest velocity with safe pressures? My barrel has the Grendel II chamber. Thank you,

Unless I'm missing something here 1,000fps at 400yds is perfectly doable with a 16" barrel. In fact you might find it will be above 1,500 and above 1,000fps for a lot further. Someone else with a 16" barrel can chime in here.

The difference between 8208 and CFE is 8208 is a single-based extruded powder and CFE is a double-based ball powder. Double-based powders are more energetic so you will get a little more velocity for the same peak pressure. Double-based are however a bit more temperature unstable so if you are into precision competition with a match bolt gun this would be a concern but with your platform and intended use you might not even notice it. I would be cautious however if you load on the raggedy edge settling on a hot load in winter and then in summer blazing away with the same load. The other way round is of course, fine or just adjust it for the heat.

I only use 8208 in loads below 120gns. 120 and above I use H4895 (I don't use CFE but others here do). Slower powders than 8208 are more efficient with heavier bullets.

As for a powder that removes copper fouling - 'Copper Fouling Eraser'. I prefer copper left in the micro pores of the barrel as it makes my shooting more accurate. I also don't clean my guns as much as I used to and find it's more useful to retain the previous zero with a fouled barrel. Modern primers don't corrode barrels like they used to and anti-corrosion tabs and desiccant in my gun safes ensure there's no damage being done by leaving the gun dirty (it also lessens the damage caused by scrubbing). The rest of the gun gets cleaned, just not the barrel every time. Bottom line, I have no use for a powder that removes copper.

[Jtod]

Klem, I was looking for 1000 fpe (foot lbs energy) and luckily I will have over 1800 FPS as well. The possibility of the temp instability coupled with me wanting to load this cartridge close to max is why I gave the 8208 a try as I will shoot the Grendel anywhere from 0-95 degrees. I have also noticed the same thing you have with cleaning rifles and purposely leave them fouled after checking zero before a hunt. I’m not sure what is going on with my testing for cfe and 8208 right now, but I clocked 80 FPS more with a max load of 8208 than I did with cfe. I was guessing that the cfe would have been 50-60 FPS faster? Go figure, I still have to see if the 8208 will have the same accuracy as the cfe.

[Klem]

That is unusual. QL tells me that you should be 50fps higher with CFE than 8208 at max SAAMI with your COAL and barrel length. I suspect either a chrony fault or your two loads are not at equal peak pressures. Your 32.5 CFE load is definitely going to hammer your gun. It is also 104% of the available case volume which is getting into compressed load territory.

How many grains of 8208 are you loading?

[LRRPF52]

What gas port diameter do you have?

What buffer uses threads? Standard carbine buffers don't have threads anywhere on them.