JavaScript is disabled
Our website requires JavaScript to function properly. For a better experience, please enable JavaScript in your browser settings before proceeding.
Well I finally took my scratch made .308 out last weekend and tried to break her in, shes having a couple issues though.
Rough/sticky extraction. Which I'll double check the headspace on and then polish with some J-B.
The issue im most concerned with is the bolt/carriers seems to just be BARELY stripping rounds off the mag. I tried 2 pmags and two different lancer mags. All with the same issue. Im worried my lower has the mag release machined to low and the mags arent sitting high enough.
And no the upper and lower aren't matched. The upper is a Aero M5E1 with a toolcraft BCG. The lower shall remane nameless.
I know, big gamble getting 308 receivers mix matched but thats what it was.

Any advice? And does anyone have any quality .308 lowers that they could take a couple measurements from the top deck of the lower to the top & bottom of the mag release latch?
As hi-lighted in the pics.
Pref. DPMS OR AERO, but as I know these arent "mil spec" rifles any measurements are welcome.

TIA!

DPMS-308-LR-05K_00.jpg APAR308003_00.jpg
 
i have an aero style lower which measures .660 from the top of the slot to the top of the receiver. the slot is .250 top to bottom. the upper and lower are of different generations(do not match perfectly), but function is 100%. i only have ASC magazines. i use 43 gr. imr 4895 with 150 gr. fmjbt .
 
Will it lock back on last round/empty mag? If not, ya need more gas/less mass
Yes I believe it will. I think every time IIRC. I got a little frustrated and got the adjustable gas dialed in fairly close to where it was mostly cycling. Then was running out of time so i moved to the pistol range to test a bevy of loads i worked up.
I'll be heading back out labor day weekend for sure. I have tons of stuff to iron wrinkles out of.

Thanks for help.
 
barrel? gas length, buffer? buffer spring

can you cycle it by hand

will the mag lock in the lower? gripping the mag and shaking it will it fall out?
Ballistic advantage modern series, 20" HBAR, RLGS, JP adj gas block .750" (seems like it needed the gas opened all the way completely)
JP SCS buffer with two tungsten weights and i think a medium spring. I have a set of springs and will be swapping the current on out for a lighter spring.

Rounds seemed to be sticking in the chamber so I'm going to have to inspect every thing real closely when I clean it this weekend. Some i could barely get out by hand they were really grabbing. And then others seemed to come right out as they should.

Ill have to take some measurements and clean/inspect and report back.

I also have a "regular" non small firing pin size bolt to try in that carrier as well.
One thing to keep in mind is this BCG has double ejectors as well. Which may also be part of the issue, i wouldnt exclude it yet.

I also need to make some dummy rounds, or buy some.
 
Ballistic advantage modern series, 20" HBAR, RLGS, JP adj gas block .750" (seems like it needed the gas opened all the way completely)
JP SCS buffer with two tungsten weights and i think a medium spring. I have a set of springs and will be swapping the current on out for a lighter spring.

Rounds seemed to be sticking in the chamber so I'm going to have to inspect every thing real closely when I clean it this weekend. Some i could barely get out by hand they were really grabbing. And then others seemed to come right out as they should.

Ill have to take some measurements and clean/inspect and report back.

I also have a "regular" non small firing pin size bolt to try in that carrier as well.
One thing to keep in mind is this BCG has double ejectors as well. Which may also be part of the issue, i wouldnt exclude it yet.

I also need to make some dummy rounds, or buy some.
The double ejectors may very well be a culprit. I remember seeing them listed for 6.5 creedmoor, stating specifically they may cause issues with .308. Don't know why
 
My M5 that's handy is 0.665" top to slot and 0.250" slot, but it's a non-factory finish. If you need measurements for a stock M5, I could pull one out. Here's a print that might help: Noreen 80%
Thanks for the measurements AND the link.
After looking closely at the drawings they have there it looks like none of the mag catch measurements are referenced.
A drawing like that with the takedown pin as the reference dimension would be ideal. I know Ray-Vin has them listed for the -15.

Man i really wish these things were mil spec'd out years ago.
 
The double ejectors may very well be a culprit. I remember seeing them listed for 6.5 creedmoor, stating specifically they may cause issues with .308. Don't know why
I know one of the fancier semi auto .308's has them as well. They may be too stiff? My buddy has the exact same BCG and its puts a decent size dent in the brass when it chucks it.
I put dbl sided foam tape and Soft velcro on my deflector.
 
i have an aero style lower which measures .660 from the top of the slot to the top of the receiver. the slot is .250 top to bottom. the upper and lower are of different generations(do not match perfectly), but function is 100%. i only have ASC magazines. i use 43 gr. imr 4895 with 150 gr. fmjbt .
Well i just measured two of these lowers, i forgot i have one thats scrap that i should probably destroy or go boating with.
But BOTH measured .695" +/- .001". so.. Idk I'd say thats def. Enough to make a difference, even if its small. Its only what .03" from what you guys have reported so far. (AND THANK YOU IMMENSELY FOR YOUR INPUT)

These uppers and lowers also didnt fit out of the gate i had to file out some of the rear radii to the buffer tower and its still kind of a tight fit. So ontop of the +.03" spacing on the mag release the upper is tight being pushed up. I was hoping to have a nice tight custom hand fit upper and lower but seems thats not in the cards now.
Not terribly happy with 5D ATM.
I think I'll be writing them an email soon.

Can anyone recommend a good 80 that they have had success with. Im going to want to sort this out asap.

Thanks again for everyones input.
 
Semi auto guns that are having problems are typically gas issues more than anything. First step I would do for testing is using 1 round and a magazine, seeing if the BCG locks behind the bolt catch reliably shot after shot, if it doesn't do that, it's a gas/mass issue.
 
To clear up the issue. What I'm seeing is that from a bolt thats locked back and released from the BHO will half way feed the round and then ride over the round and crush it when its barely in the chamber.

Beyond that I'm fairly certain the gas won't fix this issue. Not trying to be snide but the issue will remain regardless of gas.

And I Def. Do appreciate all feedback. Just trying to be as clear and concise as possible.

Like most issues (especially with custom guns like this) it's probably a multitude of small(ish) issues adding up to tolerance stacking or "non sympatico" stacking.
 
To clear up the issue. What I'm seeing is that from a bolt thats locked back and released from the BHO will half way feed the round and then ride over the round and crush it when its barely in the chamber.

Beyond that I'm fairly certain the gas won't fix this issue. Not trying to be snide but the issue will remain regardless of gas.

And I Def. Do appreciate all feedback. Just trying to be as clear and concise as possible.

Like most issues (especially with custom guns like this) it's probably a multitude of small(ish) issues adding up to tolerance stacking or "non sympatico" stacking.
You'd be surprised how it crushing rounds like that can be related to numerous factors, that happened to me with a .223 AR and I deduced the BCG was too grimey and it wasn't stripping rounds from the magazine fast enough and the less than efficient round strip was allowing the cartridge to flop out of the magazine at angles it should not have been. I cleaned off the BCG from all the grime and the cycling problem cleared right up.
 
Trying multiple magazines and seeing if the problem persists across all of them, or only 1 of them, would be scientifically helpful.
Tried 2 pmags and two lancers. Gun was brand new and freshly lubed.
Also tried 2 types of ammo some lake city m118 white box, and some federal xm80 149gn FMJ - which i must say was really impressive accuracy wise, i couldn't believe it like that better than the "official internet sniper round" ;) shows promise in this barrel for handloading down the road shortly.
Bottom right is the 762. I measured run out before shooting and it was pretty low and consistent @ .05mm (I know mm wtf weirdo!) Out six shots 4 clover leaf @ .42 moa. Shot at 100yrds. The other groups are sighting in and frustration groups just adjusting the gas etc. So not reliable to go off of.

20210824_120742_HDR.jpg
 
Last Edited:
My friend had two sequential serial aero m5 lowers that were out of spec (magazines would fall out). Called up Aero, he had an RMA same day, and they replaced the lowers without any questions
 
My friend had two sequential serial aero m5 lowers that were out of spec (magazines would fall out). Called up Aero, he had an RMA same day, and they replaced the lowers without any questions
It happens.. But these are NOT Aero, i wish they were; these are el cheapos. Bought from the same place two seperate dates. Both are the same dimension within a thou. So that kinda tells me it wasnt a mistake.
 

Upcoming Events

Tillamook Gun & Knife Show
Tillamook, OR
"The Original" Kalispell Gun Show
Kalispell, MT
Teen Rifle 1 Class
Springfield, OR
Kids Firearm Safety 2 Class
Springfield, OR

New Resource Reviews

New Classified Ads

Back Top