Looking For Help Troubleshooting Aero Precision 6.5 CM

[mccannicalbob]

I've recently started having problems with my AP 6.5 Creedmoor. Two issues, may or may not be related. Note that these problems started after approximately 300 trouble-free rounds.

First, with ammo I've been using since I put the gun together, I'm now getting fairly frequent blown primers--3 or 4 per box of twenty. Factory loaded Hornady 140g and 120g ELD-M and Winchester 140g Match. Cases with blown primers have a severe burr from the ejector. Cases without a blown primer look OK, with somewhat flat primers.

Second, with Federal GMM 130 Berger factory loads, I haven't had any blown primers (out of 60 rounds) but frequently (2-4 out of 5 rounds) after firing the bolt will not go all the way into battery for the next round. If I don't notice, I can pull the trigger and get a click; if I do notice, I can typically just push the bolt forward with my fingers (no FA).

Since the Federal ammo is so freaky accurate, I intend to stick with it and figure out that problem. However, I'd like to figure out why I all of a sudden am blowing primers.

Build is: Aero Precision matched upper and lower, Ballistic Advantage 20" rifle length gas barrel, SLR adjustable gas block, JP HP bolt and silent capture recoil spring, can't remember bolt carrier brand, but it hasn't been a problem, Geissele SSA-E trigger. When I first put the 6.5 CM barrel on, I had severe cratering and some piercing with the Hornady ammo, but the JP bolt fixed that.

I've switched to the heaviest JP SCS spring I have (red/blue) thinking it might be unlocking too soon, causing the blown primers. That didn't make any difference.

With the bolt out of the BCG, the BCG slides effortlessly back and forth. With the bolt in, it slides very smoothly, with just a bit of a hitch when the bolt rotates to lock into the lugs, but it's very little.

Any suggestions?

 

[mtgale00]

Did you get your cam pin and firing pin from JP with your bolt assembly?

Have you seen this warning at the bottom of this page: JP Bolt Compatibility

 

[mccannicalbob]

Did you get your cam pin and firing pin from JP with your bolt assembly?

Have you seen this warning at the bottom of this page: JP Bolt Compatibility

I did get the firing pin with the bolt, but not the cam pin.
The linked warnings don't seem to apply; the ammo is factory loaded so I presume isn't an excessive load. The other warning is for the JP BCG and non-DPMS uppers. I don't have the JP BCG, only the bolt and firing pin, and my upper receiver is the DPMS format.

 

[DrainTheSwamp]

Tagged
Havin same issue on a APF 6.5 creedmoor suppressed with adjustable gas block

 

[Triggs75]

Have you changed anything in your rifle from day one? Adjustments or parts?

 

[mccannicalbob]

Have you changed anything in your rifle from day one? Adjustments or parts?

Only the bolt, when I changed to the JP bolt, but it ran fine for around 300 rounds after that.

The problems started after I cleaned the rifle, but for the life of me can't figure out how that would have caused these problems.

 

[10ring1]

Since you have made no changes and this started occurring after 300 rounds without issue, Have you cleaned the barrel/chamber really well? Just thinking maybe carbon buildup in chamber may increase pressure

 

[mccannicalbob]

Since you have made no changes and this started occurring after 300 rounds without issue, Have you cleaned the barrel/chamber really well? Just thinking maybe carbon buildup in chamber may increase pressure

I thought that too. But the problems started after cleaning. Just to be sure everything was right I scrubbed the heck out of the chamber again yesterday, with no change in performance.

 

[Cavitation]

Firing pin out of spec? I know it worked for some time before these issues but I read that a 6.5 or 260 need a different size firing pin than a 308 and stranger things have happened. PSA had issues in the beginning and Aero has had a few as well. The failure to load sounds like it could be a magazine issue.
Food for thought.
Keep chugging you will get it right.
AL

 

[mccannicalbob]

Firing pin is the JP pin that came with the bolt. I can't switch to a non-JP pin because the firing pin hole through the bolt face is too small. I have not tried an entirely different bolt--the old bolt that often led to pierced primers or huge craters. I have not tried a different magazine, though I don't have the failure to load problems with all ammo; only Federal GMM. Other, hotter factory loads don't seem to have that problem. They just blow primers.

 

[padom]

I've built at least 10 6.5cm semis over the past few years. I had similar blown primer issues with my first custom Bartlein 22" barrel with rifle length gas and anything other than a mild handload.... Very very accurate tack driver, but blown primers with factory Hornady or anything other than a mild load. I would get a blown primer every 4 or 5 shots. All my 6.5 semi barrels used after that first barrel have all had +2 gas with a JP barrel extension headspaced to a JP or Rubber City High Pressure Bolt.

I would and only use JP or Rubber City High Pressure bolts with 6.5/260/6mm semis. Also, I personally would never just grab and swap out bolts. Some dont care, but I personally dont shoot 6.5cm semis that havent had the bolt properly headspaced to the barrel Im using.

I had to do extensive testing and swapping out of springs and tungsten weights using the Spring pack to find the perfect combo and gas setting where my brass was not getting beat up. I am using 2 tungsten weights and I believe the 2nd heaviest spring in the pack. My brass now comes out virtually spotless. No burs or swipes on the case head...

 

[Niles Coyote]

Sounds like you are getting bolt bounce on the Federal ammo. My build had this early on and I found that by moving to a light weight carrier stopped the issues along with use the heaviest spring on the JP SCS.

On Hornady, all of your observations indicate that the load is way over pressure for your gas system. Is the ammo that is giving you problems now from the same lot # you started with? If is isn't the new lot my be loaded different than the last. If it is the same Lot # It could be copper fouling may be restricting your bore slightly and causing a higher pressure, the only other thing I can think of is that you gas system may have fully sealed and you are now getting more pressure through the system.

JP now makes a heavy SCS http://jprifles.com/buy.php?item=JPSCS2-10H2 it my assist you with the bounce you are seeing with Federal and will also slow down opening with the Hornady. I'd go that direction first before trying a lighter carrier since your using a rifle length gas system.

 

[mccannicalbob]

Sounds like you are getting bolt bounce on the Federal ammo. My build had this early on and I found that by moving to a light weight carrier stopped the issues along with use the heaviest spring on the JP SCS.

On Hornady, all of your observations indicate that the load is way over pressure for your gas system. Is the ammo that is giving you problems now from the same lot # you started with? If is isn't the new lot my be loaded different than the last. If it is the same Lot # It could be copper fouling may be restricting your bore slightly and causing a higher pressure, the only other thing I can think of is that you gas system may have fully sealed and you are now getting more pressure through the system.

JP now makes a heavy SCS http://jprifles.com/buy.php?item=JPSCS2-10H2 it my assist you with the bounce you are seeing with Federal and will also slow down opening with the Hornady. I'd go that direction first before trying a lighter carrier since your using a rifle length gas system.

That's what I've been thinking will be my next move. Thanks.

 

[mccannicalbob]

I've built at least 10 6.5cm semis over the past few years. I had similar blown primer issues with my first custom Bartlein 22" barrel with rifle length gas and anything other than a mild handload.... Very very accurate tack driver, but blown primers with factory Hornady or anything other than a mild load. I would get a blown primer every 4 or 5 shots. All my 6.5 semi barrels used after that first barrel have all had +2 gas with a JP barrel extension headspaced to a JP or Rubber City High Pressure Bolt.

I would and only use JP or Rubber City High Pressure bolts with 6.5/260/6mm semis. Also, I personally would never just grab and swap out bolts. Some dont care, but I personally dont shoot 6.5cm semis that havent had the bolt properly headspaced to the barrel Im using.

I had to do extensive testing and swapping out of springs and tungsten weights using the Spring pack to find the perfect combo and gas setting where my brass was not getting beat up. I am using 2 tungsten weights and I believe the 2nd heaviest spring in the pack. My brass now comes out virtually spotless. No burs or swipes on the case head...

Thanks. I think I'll try getting some of the tungsten weights. Actually, I'll try calling JP first and asking if they feel that will help.

 

[mccannicalbob]

Update: spoke with a support person at JP this morning. He suggested using 2 of their tungsten weights in my SCS to keep the bolt closed a little longer. He also thought the not going into battery issue is bolt bounce and thought the heavier buffer and a lighter spring would fix this. He did say I'd probably need to adjust gas when switching loads, which I expected. Finally, he said the SLR gas block has fairly large changes between clicks, so it's possible one click open from too little gas changes it enough to become over gassed.
When asked why I would suddenly start blowing primers he suggested a different lot of ammo may be just different enough to start the problems. I guess that's possible.

It was an interesting discussion and hopefully helpful. I ordered the tungsten weights for my SCS and will report back.

 

[Snuby642]

Been watching 6.5cm threads for a while, seems like one common part always mentioned is
The jp scs.
Has anyone tried a more standard spring as opposed to tuning the scs repetitively?
I was going to try a scs on my 300 blk but seems I will wait on that, my spring twang may just stay.

 

[padom]

I've run 6.5cm 22" semis for years. Always used a 308 Rifle Length Buffer and rifle buffer spring. Reliable yes. But brass beat to shit even with gas adjusted to bolt hold open...

I switched last year to the JP SCS Heavy with their spring pack. It took some tuning but after tuned it's night and day. Softer shooting and brass comes out with no case head damage. No smears, burs anymore.


I don't have and never did have bolt bounce or reliability issues in any of my many 6.5cm semis.

I also have had all custom built Bartlein barrels, BAT and JP barrel extensions, proper feed cones on the chamber mouth, properly tuned gas blocks and and ammo with proper load development done to each of them. I have always head a JP HP Pressure bolt and it was headspaced to every barrel. I always use JP LMOS bolt carrier.

 

[Snuby642]

Thanks, I have not ever reloaded for semmi's before, just bolts and pistol.
So i looked at some saved brass, got dinged shoulders and smeared necks, mixed..
Not sorted per gun.
Guess I will have to learn to tune the buffer/spring .
That sucks because they all run fine right now.
At least it changes out quick and bring original to the range as backup.

 

[padom]

Thanks, I have not ever reloaded for semmi's before, just bolts and pistol.
So i looked at some saved brass, got dinged shoulders and smeared necks, mixed..
Not sorted per gun.
Guess I will have to learn to tune the buffer/spring .
That sucks because they all run fine right now.
At least it changes out quick and bring original to the range as backup.

When I build a new one I take the gun to the range with the JP SCS and the additional spring pack and Tungsten weights you can buy separately. I then tuned the gas block to feed properly and lock back on mag. I then start swapping heavier springs and adding tungsten weights one at a time testing all springs then moving on to a 2nd tungsten weigh and retesting springs till I find the perfect combination of soft recoil and no brass damage meaning the boly is not unlocking early.

From there Ill put 50 rounds through the gun in 10rd clips to make sure I am feeding, ejecting and locking back on last round every time. In doing that you may find you need to re-adjust the gas block after swapping out the different weights and springs.

 

[bfoosh006]

Been watching 6.5cm threads for a while, seems like one common part always mentioned is
The jp scs.
Has anyone tried a more standard spring as opposed to tuning the scs repetitively?
I was going to try a scs on my 300 blk but seems I will wait on that, my spring twang may just stay.

I haven't tried the JP SCS at all... I eliminate spring noise with grease on the recoil spring.

I run a 20", rifle length gas, with a SLR adjustable GB, Tubbs .308 recoil spring and rifle length- .308 9.3oz buffer... I guess I am a lucky guy because I have had no real issues with "pressure signs" after adding the above. ( only one over pressure ammo out of 20+ OEM types , Eagle Eye )

Prior to that and in its OEM configuration, IMHO, the firearm was over gassed and pre-maturely unlocking... ejector smear and generally roughed up brass.
Factory standard .308 "HP" bolt , with normal sized FP hole.

YMMV.

 

[SFree]

With time the bugs and problems will get worked out with the 6.5 platforms, but with the extra hassle just to make a gas gun run reliably why go through the hassle? Makes me wonder if keeping my big frames .308 isn’t the thing to do. I’m talking “battlefield “ reliable...

 

[Subwrx300]

Sounds like you are getting bolt bounce on the Federal ammo. My build had this early on and I found that by moving to a light weight carrier stopped the issues along with use the heaviest spring on the JP SCS.

On Hornady, all of your observations indicate that the load is way over pressure for your gas system. Is the ammo that is giving you problems now from the same lot # you started with? If is isn't the new lot my be loaded different than the last. If it is the same Lot # It could be copper fouling may be restricting your bore slightly and causing a higher pressure, the only other thing I can think of is that you gas system may have fully sealed and you are now getting more pressure through the system.

JP now makes a heavy SCS http://jprifles.com/buy.php?item=JPSCS2-10H2 it my assist you with the bounce you are seeing with Federal and will also slow down opening with the Hornady. I'd go that direction first before trying a lighter carrier since your using a rifle length gas system.

I was thinking the same thing as NilesCoyote. In my experience with factory Hornady ammo, its actually VERY hot in most guns. I've got to imagine they use a powder and charge designed more for 22-26" bolt guns rather than gassers. I've run the factory 140s and 123s along with max handloads with same bullets using H4350 and Varget. I tuned gas block to eject 4-430 with handloads and then fired factory with same setting. Both factory lots ejected to 12-1 o'clock with very high recoil and, early in rifle life, had issues with bolt bounce and stove piping as it was waaayyy over gassed. Federal GMM130 Hybrid we're definitely hotter than handloads but not as severe as Hornady, ejection was around 2-3 o'clock and noticably harder recoiling.

I think the 300round count is more coincidental due to metal smoothing in and rifle having lower operating friction. If bolt becomes easier to rotate/unrotate, and spring starts to relax a bit, it seems those would make it easier for bolt bounce to occur. I wonder if the two issues may actually be related more than you think: if your having out of battery issues with Fed, you may be getting similar with Hornady. I've had an out of battery discharge where bolt was 75% engaged and it fired, galling/smearing lugs slightly. Primer went dead flat compared to others.

In a normal box of Hornady 140ELDM Match and 123 ELDM, about 25% of the primers are dead square flat and the rest are between normal and flattish. With slower powder (for Hornady to max speed in longer bolt systems) peak pressure could occur later than optimal with a DI system.

Have you shot with gas system completely off to see how the primers look in "bolt gun mode"? Have you completely reset gas system? Retune gas key one shot at a time until bolt just locks back?

I think maybe you have gone the wrong way with the springs: go to a lighter spring with lighter weight and tune gas system waaayyy down.

Next I'd try a softer load. Not too sure here but I've had more issues with factory ammo than any handloads. Perhaps you load some medium loads with same bullets and see if you get the same results. Would be worth a look.

Good luck and keep posted on results!

 

[Snuby642]

I have to apologies for dragging my minor brass beatings into you thread.
I hope you stop blowing primers, and figure that brass is probably toast.
I will for now just eat the brass, and enjoy the noise of my spring.
As for old school greased springs, my sons went to war in the sandpits,
They chastise me for every drop of oil I use?

I may just dry hump my ar's and see if they outlast me, it's thier enheritance anyway, lol

 

[mccannicalbob]

I was thinking the same thing as NilesCoyote. In my experience with factory Hornady ammo, its actually VERY hot in most guns. I've got to imagine they use a powder and charge designed more for 22-26" bolt guns rather than gassers. I've run the factory 140s and 123s along with max handloads with same bullets using H4350 and Varget. I tuned gas block to eject 4-430 with handloads and then fired factory with same setting. Both factory lots ejected to 12-1 o'clock with very high recoil and, early in rifle life, had issues with bolt bounce and stove piping as it was waaayyy over gassed. Federal GMM130 Hybrid we're definitely hotter than handloads but not as severe as Hornady, ejection was around 2-3 o'clock and noticably harder recoiling.

I think the 300round count is more coincidental due to metal smoothing in and rifle having lower operating friction. If bolt becomes easier to rotate/unrotate, and spring starts to relax a bit, it seems those would make it easier for bolt bounce to occur. I wonder if the two issues may actually be related more than you think: if your having out of battery issues with Fed, you may be getting similar with Hornady. I've had an out of battery discharge where bolt was 75% engaged and it fired, galling/smearing lugs slightly. Primer went dead flat compared to others.

In a normal box of Hornady 140ELDM Match and 123 ELDM, about 25% of the primers are dead square flat and the rest are between normal and flattish. With slower powder (for Hornady to max speed in longer bolt systems) peak pressure could occur later than optimal with a DI system.

Have you shot with gas system completely off to see how the primers look in "bolt gun mode"? Have you completely reset gas system? Retune gas key one shot at a time until bolt just locks back?

I think maybe you have gone the wrong way with the springs: go to a lighter spring with lighter weight and tune gas system waaayyy down.

Next I'd try a softer load. Not too sure here but I've had more issues with factory ammo than any handloads. Perhaps you load some medium loads with same bullets and see if you get the same results. Would be worth a look.

Good luck and keep posted on results!

Thanks for the input.
I have shot it with the gas closed; primers are flattish, but not alarmingly flat. I've seen worse in bolt guns. From there I did, several times, try to get the gas set correctly, opening a click at a time until the bolt would lock back on an empty mag. With Hornady ammo, when I get it to reliably lock the bolt back, I also get the frequent blown primers. Closing up one click and it won't lock back. With the Federal ammo, once I get it to reliable lock the bolt back, I'll get frequent failures to lock into battery.

I had been using the lightest SCS spring and went heavier thinking that would keep the bolt shut longer. Between gas, buffer weight, and spring rate there seems to be a balancing act that I'm so far not able to manage. I'm hoping the heavier buffer weights will make a difference.

I'm not set up to reload for this cartridge, so I'm kind of limited to factory loads. I've tried the American Eagle ammo and 10-X ammo, with similar results.

Again, thanks for your input. I'll post results in a couple weeks when I get the tungsten buffer weights and get a chance to try it out.

 

[mccannicalbob]

UPDATE:
The JP tungsten SCS weights came in and I got a chance to shoot the gun today. The added weight made the Federal 130g GMM run really well, with no failures to return to battery, or bolt bounce, or whatever the problem was. They run good now.
No change with Winchester 140g Match or Hornady 140 ELD-M. 1 of every 3 or 4 blew the primer. With Winchester I started with a closed gas block and kept opening until it would lock back on an empty mag. None of those blew a primer. Then, when feeding multiple from a mag, I'd get a blown primer every third or fourth shot. Same issue with the Hornady. These were all with 2 tungsten weights and the heaviest JP spring I have (red/blue).
I did try going to a lighter spring with the Hornady but had the same problem. However, (too late) it occurred to me I should have turned the gas back a click or two.

A couple things I noticed with the brass. First, on the rounds that blew primers, the bolt did not lock back (if it was last in the mag), or it failed to properly feed the next round (if not the last in the mag).

Second, the non-blown primers were, as usual, somewhat flat, but the base was in very good shape with no marks, and the brass was clean. The cases with blown primers always have huge burrs peeled up from the ejector, and the entire case is pretty sooty. Burrs big enough to easily cut your finger on them.

I don't think I can add more weight to my first generation SCS. If the cause is still unlocking early, I may need to go another route with a more standard, but even heavier, buffer. Or just not shoot that ammo. Problem is, I have a bunch of it, since it never had this fu#*&ng problem before!!!

Open to suggestions!

 

[JZimm9mm]

Something really cheap you can try that has worked for me is make sure the chamber is squeaky clean and free from any solvents or oil. I have personally experienced a perfectly safe load display all sorts of pressure signs and then be remedied by cleaning the chamber with an alcohol soaked patch wrapped around the appropriate sized brush followed by a dry patch to ensure the chamber was clean and dry. I was stunned at the difference this made. I think even just storing the rifle muzzle up after cleaning can allow residual solvent or oil to seep back into the chamber. Might not solve your problem, but it won't cost you much to try.

 

[mccannicalbob]

Something really cheap you can try that has worked for me is make sure the chamber is squeaky clean and free from any solvents or oil. I have personally experienced a perfectly safe load display all sorts of pressure signs and then be remedied by cleaning the chamber with an alcohol soaked patch wrapped around the appropriate sized brush followed by a dry patch to ensure the chamber was clean and dry. I was stunned at the difference this made. I think even just storing the rifle muzzle up after cleaning can allow residual solvent or oil to seep back into the chamber. Might not solve your problem, but it won't cost you much to try.

While I'm pretty sure my chamber is clean and dry, I'll give this a shot. As you said, it's cheap! Thanks!