Suggestions for cycling issue on 12" Faxon Barrel pistol build?

[Dcommoncents]

Dearest Horde:

I recently took my new 6.5G pistol build to the range for a test run but encountered some issues I would appreciate your suggestions to help resolve. First, the pertinent specifications:

- 12" Faxon group buy barrel (carbine length gas system and I believe .075 gas port)
- Ergo adjustable gas block (bedded with blue loktite)
- Muzzle device is flash can with krinkov type brake (think Noveske flaming pig)
- Standard carbine buffer and spring in kak shockwave blade buffer tube

So I set out to adjust my gas block by loading one round in a magazine to see if the bolt locked back on the empty mag. Starting with the gas block about half way open, I fired two rounds of Hornady black and the bolt properly locked back both times.

When I moved on to Wolf steel cased ammo, the bolt only locked about 3/4 to 2/3 of the way back. I wasn't terribly surprised, and figured I would just gradually open the gas block until it functioned properly with the Wolf. To save a long and frustrating story of subsequent adjustments, I ended up with the gas block fully open with no apparent improvement with the Wolf. I did intermittently try the Hornady again, which continued to lock the bolt back on all settings, as well as several different Elander mags to make sure it wasn't an issue with how the Wolf feeds from a specific mag. When I loaded 5-10 rounds of Wolf at a time it would feed, but something like 20% of the time a round would not be stripped from the mags at all.

My hypothesis is that I was short stroking with the less powerful Wolf. When I got home I realigned the gas block with the barrel gas port using the toothpick method. The gas block is in a slightly different position now, not so much so that it was clearly misaligned enough to cause the short stroking, but that is my best guess at the moment.

Has anyone experienced this problem with a similar setup or do you have any suggestions as to other culprits? Perhaps the Wolf was resisting extraction and thereby slowed the BCG's rearward travel? Any ideas as to what else I can look at before I make another trip to the range will be appreciated.

[LRRPF52]

This may sound counter-intuitive, but you could try a heavier buffer.

If the carrier moves too early, expansion in the gas chamber behind the bolt is rapid, then it vents after a certain amount of travel.

If you allow more gas pressure to build in there over a longer period of time, you might be able to initiate a more energetic carrier inertia.

Aside from opening the port, spring weight and carrier weight are your options.

You'll probably end up opening the port and dialing in for the Hornady load.

[Tex Nomex]

Yep.
Try heavier buffer and a large-hole non-adjustable gas block before drilling. Some adjustable blocks are restrictive even when full open.

[Dcommoncents]

Thanks. I had considered a heavier buffer, only in terms of allowing more time for pressure to die down in the chamber to aid in extraction. I had H1 and H2 buffers with me at the range too, but dismissed the idea because I figured the steel Wolf cases didn't need the additional time to rebound and the Hornady ones extracted just fine. I hadn't thought about the heavier buffers allowing more time for pressure to build between the bolt and BCG but it seems obvious now.

I'll give the heavier BCGs a try with the adjustable gas block in its current alignment and full open. If that doesn't work I'll try a non adjustable block. And if none of that works I don't know what I'll do because I really want to run Wolf in this thing, but really don't want to ream the gas port because although I have the equipment for it I worry (perhaps unnecessarily) about removing the protective nitrided layer of steel inside the port.

Anyway, I'll report back once I figure this out.

[Tex Nomex]

And, since you're looking for every bit of gas pressure, might as well check your gas key and bolt rings as well.
Is the brake a true, functioning krink or is it just krink-like?

[Dcommoncents]

And, since you're looking for every bit of gas pressure, might as well check your gas key and bolt rings as well.
Is the brake a true, functioning krink or is it just krink-like?

I'll confess that I don't know what the criteria are for a true krink. But what i have is a cylinder that attaches to the muzzle threads and then a krink type cone threads into. The only place the muzzle gasses have to go is through an approximately 30 cal hole at the base of the cone. One of the biggest reasons i got it was to hopefully compensate at least a little for the short dwell time on the 12" carbine gas barrel.

[Frontier Gear]

My bet is on the gas block. Just out of curiosity, which gas block are you using?

[Tex Nomex]

I'll confess that I don't know what the criteria are for a true krink. But what i have is a cylinder that attaches to the muzzle threads and then a krink type cone threads into. The only place the muzzle gasses have to go is through an approximately 30 cal hole at the base of the cone. One of the biggest reasons i got it was to hopefully compensate at least a little for the short dwell time on the 12" carbine gas barrel.

If there's a bit of space between the funnel base and the barrel crown and your expansion chamber is big enough, your krink should be working just fine.

[Dcommoncents]

My bet is on the gas block. Just out of curiosity, which gas block are you using?

This one:
https://www.ergogrips.net/shop/ergo-750-...gas-block/

[Dcommoncents]

I'd say there's about 3/8 between the crown and bottom of the funnel. Seems like plenty for gasses to escape into the chamber. It also works pretty well. This pistol has objectively less recoil and muzzle blast than my 18" 6.5g with a hbar fluted profile.

[Lastrites]

As mentioned check your key, spray some clp on it and and pressurize it with a compressor. If you see tiny bubbles you have an issue.

[Dcommoncents]

Update: I realigned my gas block, grabbed carbine through h2 buffers, and headed to the range this weekend. There was a big improvement with the Wolf steel cased ammo from the first shot, as the bolt fully locked back probably 12 consecutive times (using 2 elander 24 rd mags and one 17 rdr).

Quite happy, I proceeded to plink some steel, only to find that the bolt began to fail to lock back intermittently. I tried all 3 buffer weights without any noticeable improvement -- it just seemed like no matter what every other time the bolt would not lock back on an empty mag, with no pattern as to which mag I was using. It's hard to say with the sample size I have, but if anything the H2 buffer made it worse and perhaps the H was perhaps slightly better than the carbine.

Other than the locking back issue, wolf fed flawlessly. Hornady Black was again 100%. So, on to the next steps: swapping in a free flowing non-adjustable gas block and checking the gas key for leaks.

[CastorTroy]

out of curiosity do you have a bad lever on your gun?

[Dcommoncents]

out of curiosity do you have a bad lever on your gun?

No, not on this lower.

[Lastrites]

Just a thought have you looked at your bolt catch real close? You have enough leg on the follower?

[Dcommoncents]

Just a thought have you looked at your bolt catch real close? You have enough leg on the follower?

I haven't, but I'll take the idea and give it a look. Would that problem make sense though, given that it locks back after the last round of hornady?

[bj139]

Do you have enough lube on your BCG? With a new build there is more friction until the rough spots are worn away.

[Dcommoncents]

Do you have enough lube on your BCG? With a new build there is more friction until the rough spots are worn away.

Hard to say, but I tend to be generous though not sloppy with slip2k. I imagine some more breaking in will help though. It is a bcg and upper previously used on other franken guns, albeit not together.

I'm really hoping a non adjustable gas block does the trick, as I don't want to enlarge the gas port or rely on heavy doses of lube. I want to feel comfortable relying on this thing for everything from home defense, to a truck gun on hand if shtf because once I get it to that point I'm probably going to sell my tavor which fills that role to my brother.

[Dcommoncents]

Problem solved at last. I finally decided to drill out the gas port a little bigger. Using a 5/64" bit I stepped up from .075 to .077 and that little bit did the trick. Running the adjustable gas block full open this Sunday, I fed steel wolf in single mags to test the lock back and did some rapid fire from mags loaded with 5-10 rounds without a single hiccup. I should have done that sooner.

This pistol is awesome now! Although I didn't shoot any groups I had no problem getting rapid hits on steel at 50 and 100 yards with both the Wolf and some Federal soft point.

I hope this helps anyone else who has a similar problem.

[GREYBUFF]

What are the possible problems with a bad lever? Thxs......paul