FTF, FTE 500 Rd Old Custom AR

[docgary]

DPMS Lo-Pro upper recr (no FA)
Krieger 26" brl, SS 1:9 fluted, .960
RRA lower, 3-4 yrs old,
B/C from original RRA carbine

upper and barrel about 500-600 rounds old
Barrel break-in no problems - early accuracy (100-200 rds) OUTSTANDING!
frequent .6xx MOA with occasional .5xx and one .4xx , all @ 100yds.

Around 500 rds, the following problems arose:

1. FTF with a second round positioned behind the first, out of the mag, in the receiver.
... I dropped the mag, with the loose rd falling out -
CLOSING THE BOLT, the rd in the chamber fired fine.

2. Failure to Eject with bolt NOT locking back on last rd.

Ammo - all Black Hills -either red or blue box - 68 and 69g

Mags - OLD Colt (Hartford,Conn) and NHMTG S/42 all 20 rds (no levelers, orig follow plates)

Problems happened in all mags (5) but 1. Never in 30 rd mags.

A couple of observations at the time of the above problems

1. I started to use Break Free's "BORE CLEANING FOAM "
Great stuff but concerned that it gummed up the gas tube resulting in deceased back pressure.
I have pipe cleaned the tube and sprayed with POWDER BLAST CLEANER but problems continued....

2. I noticed that the new Mcfarland 1 piece gas rings was dragging in the carrier - swapped out for the original -
Also noticed that the firing pin retaining pin was not completey pushed in the bolt carrier
resulting in contact and friction with the carrier. I have not shot since then.

3. I have never took apart or cleaned ejector.

AREAS OF CONCERN

1. MAGs ARE OLD - have seen better days ( mags were cleaned and
inadvertantly used rem oil on springs and inside of mag body.)
NEVER OCCURRED IN 30 RD MAGS.

2. ejector needs cleaning/replacement

3. gas tube still gummed up -


help....what says you??

Also, I'd like to swap in a new bolt and carrier....can i just replace it with any mil spec
B/C or must I do a headspace and other measurement check?

TIA
DOCGARY

 

[Bartholomew Roberts]

I think you are making too many changes at once. You could be introducing new problems but not know it because you've made too many changes in too short of a time. The first thing I would do is start trying to isolate the problem by changing only one thing at a time until I get a response.

I doubt the gas tube is the issue since even with high calicium carbonate ammo you wouldn't have gunked up the gas tube in 500rds (unless you have been sticking/squirting stuff in there - in which case all bets are off).

First thing I would look at is the 20rd mags. We know they are old and double feeds are commonly a result of worn-out mags. May be time to replace the mag springs at least.

Second thing to check is the ejector. It may be bound up with tiny brass shavings. Disassemble the bolt per the manual and clean out the hole and check the ejector spring. Keep an empty .223 case handy to reinstall the ejector. Also do this in a nice, open area because it isn't fun to play "look for the ejector and ejector spring" in your cluttered garage/workbench area if it gets loose during the reinstall.

I am not fond of playing with the ejector and a new ejector spring is cheap (and I already have a few on hand), so I generally change the ejector spring anyway if I have to mess with the ejector or if I think there is a problem there.

 

[KC&97TA]

The extractor spring or extractor shouldn't be worn out after such a low round count, and I wouldn't think you leave this rifle loaded while stored to put added stress on the extractor... it should be fine, since the bolt isn't locking back I'm looking more towards the mags or gas system. Being that it is 3-4 yr old, the extractor, spring and little buffer pad's aren't too expensive, if you want to give it a try, wouldn't be a bad idea.

I've heard some wives tales about barrels 20"+ haveing issues with carbon build up. I'd remove the gas tube and take a look at it, clean it with brake cleaner since it's off. But... I've heard of a few dirty gas systems, but I wonder if it wasn't from excessive "oil" being put into the gas system by the owners. There's aproximately 40-60,000 psi of chamber presure, even if you figure on 1% of that presure going in the gas tube that is still 4-600 psi of presure in tiny tube.

Stick with the standard 3 gas rings. The little bit of friction that could have been caused from the fireing pin retaining pin, was so minimal it's not even a concern.

Mags... Mags... the Magazine is usally the weakest link in any auto feed weapon. I'd rebuild 2 of the 20 round mags, with new springs, clean them out with some brake cleaner so they're completely dry on the inside and see what happens.

On the topic of head space... if you retain the same bolt and replace the carrier, no headspaceing needed. If you replace the bolt; other opinions say, "no", "yes" and "there is no way to headspace an AR, all the guages are worthless".

Personally I've had the headspace of all rebarrels and builds checked with M16 guages... they all checked out good, and I've even tested this with a worn out bolt vs. brand new bolt, I've even had good results on new barrels, old barrels and the inbetween. I have access to the gauges that's why I do it, if I didn't have access to the guages, I wouldn't bother... just cringe and duck the head a little on the first trigger pull.

 

[docgary]

Thanks for the timely responses!

Just to clear up....
The barrel and upper are new...+/- 500 rounds.
The lower AND B/C are several years old.


While waiting for responses, I checked the cycling on the mags in question..
Taking out the firing pin while in my basement, I loaded up each mag with 4 rounds.
While manually cycling with the CH, 2 mags, consistently, caused the problems described!
One round in the chamber with another LIVE round out of the mag,
behind the chambered round with the bolt pressing against it.
Perhaps the problem can be corrected by replacing/rebuilding the mags!!

EASY ENOUGH!

Bartholomew Roberts

First thing I would look at is the 20rd mags. We know they are old and double feeds are commonly a result of worn-out mags. May be time to replace the mag springs at least.

I concur, sir...

Second thing to check is the ejector. It may be bound up with tiny brass shavings. Disassemble the bolt per the manual and clean out the hole and check the ejector spring. Keep an empty .223 case handy to reinstall the ejector. Also do this in a nice, open area because it isn't fun to play "look for the ejector and ejector spring" in your cluttered garage/workbench area if it gets loose during the reinstall.
I am not fond of playing with the ejector and a new ejector spring is cheap (and I already have a few on hand), so I generally change the ejector spring anyway if I have to mess with the ejector or if I think there is a problem there.

I have never checked/cleaned/replaced the ejector spring since
i dont have a tool for the removal/replacement of the roll pin!:banghead:
Although I DO have all replacement parts....What tool(s) are needed?THANKS, BART!
__________________
KC&97TA

Posts: 662 The extractor spring or extractor shouldn't be worn out after such a low round count, and I wouldn't think you leave this rifle loaded while stored to put added stress on the extractor... it should be fine, since the bolt isn't locking back I'm looking more towards the mags or gas system. Being that it is 3-4 yr old, the extractor, spring and little buffer pad's aren't too expensive, if you want to give it a try, wouldn't be a bad idea.

Actually, the bolt and carrier are 3-4 years old...
its the barrel and upper that are relatively new (500+ rounds old)
I've replaced the extractor spring, extractor and insert.

Stick with the standard 3 gas rings. The little bit of friction that could have been caused from the fireing pin retaining pin, was so minimal it's not even a concern.

Couldn't agree more!

Mags... Mags... the Magazine is usally the weakest link in any auto feed weapon. I'd rebuild 2 of the 20 round mags, with new springs, clean them out with some brake cleaner so they're completely dry on the inside and see what happens.

The mags are so banged up I think replacement is in order...
I got them off the internet and pleased for the price....I believe I got my monies worth!

On the topic of head space... if you retain the same bolt and replace the carrier, no headspaceing needed. If you replace the bolt; other opinions say, "no", "yes" and "there is no way to headspace an AR, all the guages are worthless".
Personally I've had the headspace of all rebarrels and builds checked with M16 guages... they all checked out good, and I've even tested this with a worn out bolt vs. brand new bolt, I've even had good results on new barrels, old barrels and the inbetween. I have access to the gauges that's why I do it, if I didn't have access to the guages, I wouldn't bother

Thanks, your take on this seems to be the consensus

... just cringe and duck the head a little on the first trigger pull.

Love it....ROTFLMAO
Thanks, KC&97TA

Thanks, guys!!

docgary

 

[asknight]

Always use a new bolt with a new barrel. SOP there.
Beef up the extractor to the latest spec, perform a thorough cleaning of your gas tube, and rebuild those mags with fresh springs. I'd then bet it will run like it should.

 

[Bartholomew Roberts]

I'd try the mag rebuild first and see how that works for you. If that doesn't fix it, then you'll need a 1/16" (I think) punch for the ejector roll pin. You can also use a bullet tip to get it started and then pull it the rest of the way out if it isn't too tight.

 

[docgary]

asknight

Always use a new bolt with a new barrel. SOP there.
Beef up the extractor to the latest spec,
perform a thorough cleaning of your gas tube,
and rebuild those mags with fresh springs.
I'd then bet it will run like it should.
_______________________________________

Today, 07:09 PM
Bartholomew Roberts

Posts: 9,157 I'd try the mag rebuild first and see how that works for you.
If that doesn't fix it, then you'll need a 1/16" (I think) punch for the ejector roll pin.
You can also use a bullet tip to get it started and then pull
it the rest of the way out if it isn't too tight.
__________________

Thanks, guys.....As far as a new bolt, will any mil-spec bolt do?
Any suggestions as this rifle is a dedicated bench rester with big plans
ie "Young" , special surface ion/electromagnetized/tension deflecting stuff?

If it goes as expected, will I be able to use the same roll pin?
What is the up-to-date extractor spec? from where -manuf?

Much appreciated!!!

docgary

Just started reloading first batch of .223 on my new Dillon 550....
Primers went in purfect!!
past up on the powder - waiting on the scale..
seating die set up perfect....
even played with the crimp die (dillon) just for gettin use to the press...

Does anyone use the Hornaday OAL gauge with modified case to determine
free bore? It seems that whenever I see recipes for 223 the OAL is a constant 2.260...(max for mags) does anyone consider shortening the OAL for 'jump' consideration?

 

[taliv]

given your krieger barrel which i assume was chambered by whoever rebarreled it... you could just ask them instead of spending the money on the tool.

it also sounds like you already know that in order to seat into the lands or anywhere close, you'll go well past 2.260" which means you're single-loading. from your bench comment, that may not be an issue for you, in which case, knock yourself out!

even so, i'd wager you won't be able to seat anywhere near the lands even with a long bullet. so since you're already jumping so far, that no, it wouldn't make any difference at all. however, moving it in and out would change the neck tension

but if you want to try, you might consider the sinclairintl tool, as it has a couple advantages over the hornady version.

and if you achieve some measure of success, be extra careful, as you will have VERY little hold on those bullets, which means when you're just getting ready to squeeze the trigger, the RO will call a cold line and make you unload. You'll eject the brass, leaving the bullet embedded into the lands, and pouring powder in your chamber, extension and lower.

 

[Bartholomew Roberts]

The use a new bolt with a new barrel is a good practice; but I wouldn't worry too much about using an older bolt with a new barrel either so long as it was under say 6k. In theory you could create excessive headspace; but in practice you hardly ever see it unless you are swapping a heavily used bolt into a heavily used barrel (or the part was out of spec to begin with - in which case you usually notice it right away )

If you are going to go with a new bolt, Young has an excellent reputation. I haven't used the coatings you mentioned so this comment is made in total ignorance; but I would be skeptical that they would provide much benefit for benchrest shooting.

On the extractor, typically people will upgrade to a heavy duty extractor spring and add an O-ring or D-fender around the extractor spring to increase extractor tension. There isn't much you can do to upgrade the actual extractor itself without going to a non-standard bolt design.

 

[docgary]

thanks for replies....

good thing I asked....my understanding of measuring the free bore was to shorten the bullet seating -
with the goal to be at least 0.020-0.040inches short of the lands/grooves.
Yes, I did read that being "in the jump" or " on the jump" is used by benchresters,
but the rule of thumb was to be short of the lands should produce better accuracy overall.
Either way, I'm just staying with 2.260 max to trim to 2.250 and concentrate on learning good reloading technique.

On the extractor, I change out the extractor, spring and insert every Spring (2-3 times on this bolt).
Other than the original problem which im convinced is mag related, I have had no extractor/ejector problems.

Thanks again, guys!

docgary