Slightly short chamber, fixed by AA CS

[worthen86ford]

Took my brothers new build out to the range yesterday. Shot well but notice that we had to use the FA several times on mag changes. Went to clear the rifle on a cease fire and had to motar the charging handle to get the round out. It pulled the bullet, powder got everywhere, and had to clear the bullet with a cleaning rod. Decided to hang it up for the day until i could get some chamber guages, but checking the bolt face depth it looks like i might have found the issue. At least i hope.

We put an underground tactical type2 bolt in it; barrel is an Alexander Arms 16" lite. Face depth on bolt using a dial caliper is .134" or so. I'll try a depth mic on it tomorrow at work but i'm thinking that .002" or so could be enough to cause this on a long for tolerance round. Ammo was hornady black btw.

Also notice the case necks were dented on the end of the case opposite the ejector marks. Maybe over gassed? Maybe related to the headspace issue? I'm using a spikes t2 which did good in my grendel.

Here is some pics. Second one is the bullet removed showing the marks i think the rifling left on the round. That ring on the nose is from the cleaning rod.

What y'all think? Am i missing something? Still buy guages?

[LRRPF52]

None of the conditions you are showing are headspace. Headspace is the distance from the bolt face to the shoulder where the cartridge stops from going anymore forward.

What you're showing are signs of jamming the lands.

Your case neck dents are normal and very slight. When you re-size, they come right out.

Your main issue is jamming the lands. What's the COL on those cartridges, from base to tip?

[worthen86ford]

Not sure but i'll find out. Its the new hornady black 123 gr factory ammo that came out. I had a couple of sst rounds, factory as well, that i compared to and by the eye they seemed about the same coal. Brother has the rest of the unfired rounds so i'll have to get them from him to measure.

So a couple extra thou on the bolt face wouldn't jam the lands? I'm not asking to be a smart arse just never had this happen. I should have also mentioned that my jp bolt and AA hard use bolt measure around .136-.137" using the same dial caliper.

[LR1955]

Not sure but i'll find out. Its the new hornady black 123 gr factory ammo that came out. I had a couple of sst rounds, factory as well, that i compared to and by the eye they seemed about the same coal. Brother has the rest of the unfired rounds so i'll have to get them from him to measure.

So a couple extra thou on the bolt face wouldn't jam the lands? I'm not asking to be a smart arse just never had this happen. I should have also mentioned that my jp bolt and AA hard use bolt measure around .136-.137" using the same dial caliper.

WF:

LRRP52 is correct. Not a headspace issue. If you want to do a quick check, pull a bullet from the Hornady ammo that jammed and drop the case into the chamber, let bolt go forward and extract. It will extract easily is my bet. Not a headspace issue.

The ogive of the bullet is engaging the lands too much is the problem. A few turns with a finishing reamer will solve the problem.

It will eventually disappear as you erode the throat from shooting but a finishing reamer is a better option.

Or you can seat the bullet a bit deeper. Looking at your picture, I believe this is a viable solution as well, but seating bullets deeper brings with it risk, IF the factory loaded it to a maximum pressure. I doubt any factory load comes near maximum pressures due to liability issues. I would try seating it until it doesn't hang up anymore then shooting one round and if that shot seems to give more recoil, doesn't sound right, and or the primers are flattened / backing out, then the only solution will be a finishing reamer. If you aren't experienced in these sorts of intuitive and observational judgments, go with the finishing reamer.

LR55

[ricsmall]

These companies need to start getting these chambers right. Some folks will take these screw ups and run with it on the web and ppu won't be the only one dropping ammo lines for the Grendel. The reamer may be the problem, but the barrel seller needs to check this stuff.

Richard

[worthen86ford]

Ok i was able to take some COAL on the three factory loadings i have, hornady black 123gr eld, hornady 123gr sst, and wolf 100gr steel case. I took 5 measurements from 5 rounds of each.
ELD: 2.248", 2.247", 2.245", 2.247", 2.248"
SST: 2.239", 2.240", 2.239", 2.238", 2.238"
Wolf: 2.196", 2.200", 2.203", 2.197", 2.201"

I also brought a depth mic home and measured the face depth of the three grendel bolts i have:
Underground Tactical: .1325", .133", .133"
Alexander Arms: .134" all three spots
JP Enterprise: .135", .135", .135"
I think the mic needs to be recalibrated against a standard but it replicated what my dial caliper showed pretty much. The underground tactical bolt is short a thousandth or two compared to the others. Something else i noticed was the extractor on the UT bolt is proud to the bolt face. The other bolts have the bolt face proud to the extractor. Comments?

I cycled the three different cartridges by hand with the UT bolt in the same chamber and found that the wolf had no indications of jamming on the lands. One or two of the sst rounds did show an indication maybe but not bad. Every eld showed indications like i had at the range. I bet the hot chamber shrunk on that round at the range which kept us from clearing it with the CH. i also remeasured the ELDs and they all seated a .001 or so more after being cycled through.

I swapped the UT bolt with the AA and it still had some indications on another 3 rounds of ELD cycled through. But none notice on sst or wolf. I cycled the ELDs through my other AA 16" lite with the JP bolt and it had some signs of jamming lands as well.

I think i am just going to move the UT bolt into my 10.5" grendel with the anderson barrel as i only intend on shooting wolf through that pistol. I also believe that we will stick with the sst loading for now for hunting/grouping and maybe try the ELDs later after the lands are a little more eroded. What y'all think? I'm reading more and more similar cases happening to others with AA barrels. I think if Bill reads some of these threads it might be something to look into on his end. I'm not disappointed enough to send the barrel back because it shot so well and may be bolt related, but it is concerning that others are having similar issues.

Also, does this look like flattened primers i read about? One on the right unfired; the other three are some spent cases from the rifle in question. Flattened primers mean overpressure right? Jamming the lands would cause this correct?

[worthen86ford]

I'm still learning here but its easy to say the cartridge base to ogive measurement is longer in the eld loads than the others, right? Do bullet manufacturers publish the ogive from bullet base or anything? I havent seen this in my hornady loading book. Thinking about when i do start reloading.

[Texkitch]

Lots of threads on this topic lately. Thanks for those measurements. I have only shot handloads so I didn't know the factory COALs. Those are close to the measurements to the lands I took in my 16" AA Lite chamber I just got in January. I'm going to go with it because it shoots good if I load to stay about 10 mils off of the lands. I'm still experimenting with the jump distances. My measurements are shown in the picture below.

[Jakal]

Yes jamming the bullet into the lands can cause over pressure. But even with longer throated barrels, factory loads will still sometimes run hot and show flattened to near flattened primers. Seat your bullet a little deeper and about .5 (1/2 grain of less powder from your minimum load and see if you still have the issue, 3 rounds should do it.

The factory Hornadys are loaded short, kind of a known fact. So if you are jamming with factory sst, then i would take the advice of a finishing reamer.

[worthen86ford]

Im bringing up my old thread because hornady AG is jamming the lands as well. Is there anything i can do about this without pulling the barrel out of the reciever? I really dont want to remove the barrel because the rifle shoots so well. We have been just firing the last round rather than clearing with the CH but we kinda wanna give 3 gun a try which will require clearing live rounds without firing. Almost would rather build another upper maybe even in 5.56 if the fix gets too costly. Could just leave this upper for hunting purposes only. I dont expect AA to do anything given the time that has passed which I accept the responsibility for.

[rabiddawg]

Contact AA, tell them your story. They may just surprise you and take care of it for you. This was especially true when Bill was there.

I have never used a finish reamer. I think you can rent one from Reamer Rentals.

[VASCAR2]

With this being a SS Alexander Arms barrel a finish reamer could be used. I suggest you contact AA as they did have a few out of spec barrels slip out around that time period. If AA won’t help you out you could do what a Friend did with his short chamber 6.5 Grendel. His barrel was very accurate and he didn’t want a refund or exchange. He seated the factory ammo bullets a few thousandth deeper where they would extract. He chronographed the ammo and saw no difference in velocity or any indication of higher pressure.

If A-Max or ELD-M factory function and can be ejected but the Hornady American Gunner won’t eject could be the slight profile difference in the bullet causing the problem. I’d suspect after a few hundred rounds the throat would wear enough the factory ammo would eject. The short chamber was a non issue for my friend since he didn’t shoot much factory ammo and he only owned one 6.5 Grendel.

[worthen86ford]

Called AA and they told me to send in the upper and they would ream it out. Shipped this morning so we’ll see how it goes. Surprised they were willing since it’s been 2 years since i bought it. Great company imo.

[Sticks]

I did a seating test on some ELD and HAG ammo. Pushed them all the way back to 2.10 COAL in .005 increments (started at a pulled 2.26 +/-) No appreciable change in velocity, the averages tended to lean towards dropping with the deeper seating. I don't remember how the SD and ES trend went, nor accuracy.

[worthen86ford]

Got the upper back today. AA smith called after he finished reamed it. Said it just needed a little material removed. Unfired rounds will now fall free from the chamber with a light tap. Really impressed with the CS. I honestly didn’t expect them to do anything and they made this right. Definitely will be doing business with AA in the future.

[VASCAR2]

Thanks for the update! Good to hear they took care of you.

[Jakal]

Sometimes resurrection is a good thing. Glad AA took care of this for you. Lettuce know how it shoots!