I step in here with great trepidation.  The experienced hands are working on this.

Have you, or others, thought about the barrel drilling for the barrel gas port?  The comments I have seen so far are very systematic about checking tolerances along the gas flow route, but I haven't seen any comments so far on the barrel gas port size, not just external barrel size but through and through.

Thank you for posting this in such a transparent way.  This is a tough, but sort of bread and butter problem that many may learn from.


Regards,

Rick

According to Jim Eden from Bushmaster, the 20" and 24" H-Bars (0.75" OD) should have gas ports that measure 0.093"

I have verified that my Bushmaster 24" H-Bar has a gas port that measures 0.093"-0.094"

I've been following this thread with great interest as my new AR is doing the exact same things.  I gather this is a "underfunction" (not enough gas) as opposed to an "overfunction" (too much gas)?  Seems like hot nato spec rounds work great and anything loaded less are iffy.  Any new info on this Rifle?  Thanks, Rob.

Originally Posted By skunkhound: I've been following this thread with great interest as my new AR is doing the exact same things.  I gather this is a "underfunction" (not enough gas) as opposed to an "overfunction" (too much gas)?  Seems like hot nato spec rounds work great and anything loaded less are iffy.  Any new info on this Rifle?  Thanks, Rob.

I plan to go to the range very soon and try M855PD and Wolf 62 gr FMJ. The only things that I can think of that would continue the short stroke effect are:
* undersized gas port (but its 0.093" already, may need to drill it to 0.100"?)
* rough chamber (send it back to Bushmaster I suppose)

1) 62 gr FMJ, 2005 Lot
2) AR-15, Bushmaster 24" NM H-Bar (5.56N chamber), chromed bore/chamber, 1/9 twist, Ameetec lower, RRA everything else
3) 120 rounds fired, single loads only (basically testing the bolt hold open 120 times).

EXCELLENT ACCURACY. Was experiencing 0.3"-0.4" at 25 yd in 3 shot groups, and about 0.5"-0.75" 5 shot groups at 25 yd. This stuff was comparable if not better than XM193 through the same rifle.

Wolf and consistency usually don't go together, but I found that I could improve my groupings by shooting one way versus other ways (gently squeezing trigger w/o jolting rifle, holding the stock steady, etc...) and it helped the groupings.

I was doing function testing with the AR-15. It previously would NOT cycle 55 gr JHP Wolf (lacquer coating) at all. I tested some modifications/changes I made and it cycled the Wolf 62 gr polymer coated ammo 97.5% of the time.

Out of 120 trials, only 3 experienced improper last-round BHO. 1 was most likely the cartridge (used a known working USGI 20rd mag), 2 may have been because of 1 T-65 mag that had some issues holding the Bolt open when manually pulling the CH.

Regardless, 3 "failures" out of 120 was better than 80 "failures" out of 80!

Wolf has stated they plan to modify the powder charge for more velocity and chamber pressure and implement it as a running change w/o any difference in packaging or markings.

The reason for my function test is because I want to know my rifle can cycle Wolf. If zombies started attacking and I ran out of the "good" stuff, I want to know that I can fight my way over to the local Meijer/Walmart and load up on .223 ammo regardless of brand. I fired 1 XM193 round just to see if the rifle worked with a much hotter load, and it did (possibility of overpressure/overaction)

What I did to the rifle thus far:
replaced Wolff XP Action Spring w/ standard RRA A2 action spring
replaced MacFarland 1 piece gas ring w/ standard 3 piece gas ring
lapped gas key and applied threadlocker as a sealant, torqued and staked gas key bolts
polished chamber using 1000 grit and 2000 grit sandpaper and nylon bore brush.

I examined each spent case and did not see any unusual scuff/scratch marks. I kept the Wolff XP extractor spring and removed the rubber insert (same as what Mongo01 does) and all the cases show a single "scratch" mark where the extractor clips the rim. I'm not sure if this is bad or what, but luckily I did not experience any FTEx/FTej.

Hey guys, been along for the ride whole post, metroplex is driving and im riding shotgun (no pun intended)
My XM15 E2S  14.5" phantom is doin it also, altho I can say this, depending on how exactly I clean and lube, there have been days where its  gone thru the 40 the la belle the thermold  and the mil 30s with no FTF FTC using multiple types 5.56 and multiple .223, and there are days where it dont matter if I pray for a miricle it jams um slams um and no gos reduced to operator cycle only no matter what mag/ammo

It did it brand new, it did it more after wolff +10 installed all the way around, still did it after putting stock recoil buffer spring back in, and still does it after replacing all internals bolt/carrier/trigger assy, and pins with delton chrome. I have become quite an expert shot with my G22 as more often than not I put the M4 back in the case after field cleaning and having it last for a clip or 2 and then go right back to FTF FTC. Its an awesome rifle I love shooting it but a she can be a finikee*itch its very frustrating.
I could not imagine being a RANGER and being issued one that does this.

Im down in Auburn, lived  at north end of lake W all my life - lfp kenmore ballinger lake city and so on
No H buffer for the AR

RGR that
Shot yesterday, couple hundred rounds of xm193 and tracers,  the delton chrome carrier has a nice smooth action and trigger is nice and tight, no ftf ftc still holding breath.....

I only got a chance to shoot about 30 more rounds thru the AR-15 (focused more on Glock)... no FTFs or short stroking. It was cycling Wolf like a champ. the cases were being ejected to the same location as XM193! The M855PD cases were ejecting to the front though but the POI @ 25 yd was the same as Wolf 62 gr. XM193 POI was about 1"-1.5" higher at 25 yd.

But now that I have the AR working... Wolf prices just went up.

H buffer here tomarrow,  DPMS A3 upper 16" preban M4 type with 5.5" suppressor also, should pick up some distance/accuracy
Im pretty sure the ammo was major factor on those FTF FTC, was useing that USGI 55g frangible from ammoman, was noticing both condensation in the upper along carrier groove and thick black smoke out the barrel each shot after getting hot, in fact I had all the symptoms useing that ammo FTF FTC doubles and super slam jams, the winchester 55g sbt is flawless (and spendy), the Sellier&Bellot czech 5.56 SS109 greentip perfect, and now ammoman lake city federal XM193 is 99 of 100 I still dont care for the reused brass complete with dings and the lake city definately has a little more pop, the winchester and S&B are cleanfire, the lake city still a little dirty really shows up on the delton chrome carrier and bolt
At 100m 16x16 florescent orange on white bull 30 of 30 pulling trigger almost as fast as I can, small cheat tho both the comp ml2 2x and ARA2 laser (well, I got some skills) but im very happy she gettin it done now


I stand corrected on ammo responsible see below

UPDATE

Installed the H buffer per Tweak (ordered H buffer received H2 buffer)
(stock 2.95oz H 3.77oz H2 4.7oz) Replaced BM A2 14.5" 1.5" phantom2 with DPMS pre-ban A3M4type 16" threaded with 5" suppressor, and the much awaited back ordered rear takedown tension pin that works exactly as expected, you can watch the 3 thousandths gap dissappear between upper and lower and regain the solid no slop feel. After quickly attaching the trijicons it was off to the range. Pure luck the fresh install provides a 50 zero, im snapshottiing bulls with the reflex II. I can feel every aspect of the action, precise, predictable, perfect. 300 rounds of multiple 5.56 and .223, multiple different supplier mags, allowing sufficeint cooling between for break in of the fresh chrome lined, finally a killer day at the range.
I am proud to say  this rifle is now combat ready, i'd bet my life on it.

Unfortunately the brand new Bushmaster XM15 E2S off the showroom floor is not combat ready, however after a few modifications it can be. (Advised from armourer and ex-military at my local store the alignment of gas tube thru barrel nut, not necessarily the ID and OD of tube and key, to test this barrel muzzle 90 degree to floor let carrier fall freely, any binding between tube and key good indicator, also carbon and gas will be seen built up in primary direction of leak if thats the problem, the BM is inherant FTC and FTF the stock gas system is "cheap" and should be revised)

The $100 question, does it cycle Wolf? My AR-15 could cycle SAAMI .223 loads w/o much difficulty but couldn't cycle Wolf (loaded to about 10,000 psi below SAAMI spec). Once I got it to cycle Wolf properly, it was cycling everything else w/o difficulty.

After reading numerous posts the majority falls on wolf not being desirable ammo to use, therefore I wouldnt get it just to see if it cycles properly. I am $ concious but I try to get what performance I can for the best dollar - Ill spend a little more for piece of mind than go dirt cheap and worry. I get S&B greentip
4.59$ (20) no failures thats good enough for me and the Lake City 55g @ 109$ for 500 new ammo with reused brass I wont get again that brass is too soft

Ok, but Wolf isn't crap. the people that have probs with Wolf are just complaining (sour grapes) and going with higher pressured ammo which will work, but it masks and underlying problem with the rifle.

There's probably a specification or requirement for the military M16/M4 to properly cycle an underpowered and overpowered cartridge (low test/high test) to verify the rifle meets the spec. Wolf is around 40,000 psi, while SAAMI .223 is something like 55,000 and the M193/M855 is around 60,000+. Quite often the rifles that can't cycle Wolf operate fine with M193/M855.

I would imagine if the problem is indeed a faulty gas system, its gonna fail with any ammo, true maybe not as often with higher psi ammo, eliminate the gas system failure and see what kinda results ya get with any ammo

My AR-15 cycled fine with XM193 and M855PD, never had a problem.
With SAAMI 223, it cycled fine, but was on the verge of not cycling properly on the lighter loads.
With Wolf, it was a bolt-action rifle that would occaisonally jam!

It's just peace of mind to have the rifle cycle all different kinds of ammo. In case zombies attack and you run out of ammo, the closest store that has .223 Remington only have SAAMI 223 and Wolf. You finish up the SAAMI stuff and woops, your rifle can't cycle Wolf because it's "crap and you will only shoot XM193".

I had the same exact problem.  When I had my first AR delivered I wanted to test the mag and the rifle so I pulled the firing pin out, loaded a mag and tested the feed.  I had the same problem with the round poping the nose up too far and the bolt slamming into the case of the round.  I found the mag was the problem.  Changed mags and everything ran great!!  I don't know the exact specifics of why, but can only speculate that the mag catch was too low causing the mag to sit too high in the receiver making the bolt drag on the rim of the round.  Or that the lip on the right side of the mag was off.
You can check and see if this info helps:  in a safe place!!! mark the rounds so you know which are on the left side and right side when loaded into the mag, load 4 rounds into the mag, pull the firing pin out, and cycle them through by hand and see if the round pops out of the mag and is loose in the receiver when the bolt comes back.  I found that the right side pops out and the left side didn't.
I still use the other sa80 mags, I just don't use that one any more, and ran a thousand rounds through them with no problems.
Terry

metroplex,

Please help me out here.  Between 8-12-05 and 8-13-05 somthing happened.  I have read the thread 3 times and am slow to comprehend.  My apologies.  

Was it lapping the gas key that fixed your problem?

What happened?  Fire polishing the chamber?

Glad it works.

Regards,

Rick

Originally Posted By Rick_Lind: metroplex, Please help me out here.  Between 8-12-05 and 8-13-05 somthing happened.  I have read the thread 3 times and am slow to comprehend.  My apologies.   Was it lapping the gas key that fixed your problem? What happened?  Fire polishing the chamber? Glad it works. Regards, Rick

I had done a few things (Tweak's suggestions):
1). Lapped gas key (used 1000 grit sandpaper on a flat/true metal surface), applied red loctite as sealant for the gas key, torqued gas key bolts, re-staked gas key bolts

2). Polished chamber by wrapping 2000 grit paper on a 30 cal nylon bore brush and used a cordless drill to just smooth things out.

I think the first one was "it". I did a few other things:
1). Swapped out wolff xp action spring for stock action spring.
2). Swapped out MacFarland gas ring for standard 3 piece gas rings

Thanks!

R

i have a new dpms lr-308 with a 24in ss fluted bbl. it is short stroking and not picking the next round up out of the mag. it ejects the spent brass just fine. my gas block has side to side twist movement and front to back movement. both directions about a 1/16 of an inch and am getting blowby around the gas block. any suggestions on how to fix the problem, cause i really like this rifle, it'll shoot with high dollar bolt rifles. my e-mail is [email protected]
                           thanks
                           blackhawkkid223

i am also having simular problems im very new to ar's got my first one used fired 60 rounds of wolf through a used mag no problem spent 6 months in new orleans due to katrina bought dpms new uppers from gunbroker and rra lowers from a gun show put 2 more togher and replaced the lowers components from my original ar followed instructions from book                                                                                                                                                                                                                                                                                                                                 #1 (used) m4 with new cheaper colapseable stock sometimes fired 2 rounds with one trigger pull sometimes loaded next round but didnt reset trigger sometimes didnt load next round at all with both wolf and rem ammo


#2 new pistol upper new pistol marked lower collapseable stock buffer tube(modified so stock can not be put back on) same problem as above

#3 new a3 20in dpms upper new rra lower new choate collapseable stock would eject spent casing but did not feed next round

all problems occoured with wolf and rem ammo they also occoured with new usgi grey mags with green followers 'used mag and new beta mag any help would be appreciated ive been told i need heavier buffers and not to use wolf ammo also any extra info on ar's would be appreciated im very new to them emphasis on very
thanks  

Originally Posted By sharpshooter8026: i am also having simular problems im very new to ar's got my first one used fired 60 rounds of wolf through a used mag no problem spent 6 months in new orleans due to katrina bought dpms new uppers from gunbroker and rra lowers from a gun show put 2 more togher and replaced the lowers components from my original ar followed instructions from book                                                                                                                                                                                                                                                                                                                                 #1 (used) m4 with new cheaper colapseable stock sometimes fired 2 rounds with one trigger pull sometimes loaded next round but didnt reset trigger sometimes didnt load next round at all with both wolf and rem ammo #2 new pistol upper new pistol marked lower collapseable stock buffer tube(modified so stock can not be put back on) same problem as above #3 new a3 20in dpms upper new rra lower new choate collapseable stock would eject spent casing but did not feed next round all problems occoured with wolf and rem ammo they also occoured with new usgi grey mags with green followers 'used mag and new beta mag any help would be appreciated ive been told i need heavier buffers and not to use wolf ammo also any extra info on ar's would be appreciated im very new to them emphasis on very thanks

#1 sounds like a FCG issue and possible short stroking.
#2 sounds like short stroking
#3 sounds like short stroking

How do the chambers look? Are the gas keys tight? How does the gas tube look?
Make sure you are using stock buffer springs and stock buffers (no XP stuff).

I had the same problem in my Bushmaster.  Read this thread and went back to the range to check out my mags and bolt carrier group.  I happen to have two other Bushies so I put a known good complete BCG in and WallA! functions flawlessly.  Conclusion:  Bolt Carrier, not the bolt was the problem.  I had installed a new Bushy bolt in the old carrier and still had the same probem.  So, solution is, I need a new bolt carrier, not a bolt.  My thought is that an extra BCG is a good thing to have since it is the heart of the whole system.

I had the same problem in my Bushmaster.  Read this thread and went back to the range to check out my mags and bolt carrier group.  I happen to have two other Bushies so I put a known good complete BCG in and WallA! functions flawlessly.  Conclusion:  Bolt Carrier, not the bolt was the problem.  I had installed a new Bushy bolt in the old carrier and still had the same probem.  So, solution is, I need a new bolt carrier, not a bolt.  My thought is that an extra BCG is a good thing to have since it is the heart of the whole system.

The gas key also happens to be attached to the BC. Perhaps your now functioning rifle has a BC with a tight/properly installed gas key?

BTW

My AR-15s are now functioning 100% with Wolf ammo. I was rapid-firing with my 16" M4 and didn't run into a single malfunction.

help i nedd a compotent ar guy in central fl to teace me how to trouble shoot my ars stopped at local gun shop and was told 100 per rifle ant thats times 4 and they wont show me so i can learn myself i was scolded and told i should have bought complete guns instead of trying to buy kits helppppppppppp

Originally Posted By sharpshooter8026: help i nedd a compotent ar guy in central fl to teace me how to trouble shoot my ars stopped at local gun shop and was told 100 per rifle ant thats times 4 and they wont show me so i can learn myself i was scolded and told i should have bought complete guns instead of trying to buy kits helppppppppppp

What are you trying to troubleshoot? Short stroking? failure to feed, failure to eject, or failure to extract, etc...?

#1 ar pistol : extracts spent round but seems like it doesnt reset the trigger when i break the rifle down and manually set hammer it sticks like normal


#2 ar m4 16 in barrel it doesnt always extract and when it does the trigger doesnt reset


#3 ar m4 6.8 16 in barrel same as #2


#4 ar a3 with 20 in barrel doesnt eject

#1 ar pistol : extracts spent round but seems like it doesnt reset the trigger when i break the rifle down and manually set hammer it sticks like normal


#2 ar m4 16 in barrel it doesnt always extract and when it does the trigger doesnt reset


#3 ar m4 6.8 16 in barrel same as #2


#4 ar a3 with 20 in barrel doesnt eject

I'm having the same problem in my Colt 20" HBar. I floated the bbl, installed a spiral gas ring and the accu wedge. Today was the first time I've shot it since the mods and the first time I've ever had a malfuntion. Short stroked, FFTF, 20 out of 24 rounds.
The four that worked were reloads, most of the rest were Black Hills 68GR. blue box.
I guess I'll try switching back to the original gas rings as the new one is pretty tight.
Great site guys, thanks for the info.

Alright guys, my build is done, and it's short stroking.  The only not name brand part is the Collapsible stock and buffer.

1/9 Twist 16 inch M4 barrel.
RRA BCG
Mega Upper
Mega Lower
DPMS LPK.


I was shooting Remington 55 grain JSP.

It failed to lockback on the last round every time.  out of 40 rounds it only chambered a second round after firing 5 times.  And the last 3 rounds I fired went perfectly.

Could it just be that it's new and wearing in? Or Likely the no name buffer spring?

To save the information, but to prevent the topic from become to long for easy reference.