How To Determine The Round Count On A Used AR-15 (not 56k friendly) - Page 2

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[ARCHIVED THREAD] - How To Determine The Round Count On A Used AR-15 (not 56k friendly) (Page 2 of 2)

Posted: 10/17/2006 8:18:51 AM EDT

[#1]

Quoted:
Finally I have some time to upload some pics as I´m recovering of knee surgery...

Great pics! Thanks for sharing those. What kind of lube are you using just out of curiousity? Your low-round count bolts seem to be wearing less on the ring behind the extractor.

That 12k bolt looks like it is getting pretty close to the end of its life with the pitting on the bolt face. Are you going to run it to destruction? I'm curious how much more it has in it.

Posted: 10/17/2006 9:20:10 AM EDT

[#2]

Quoted:

Great pics! Thanks for sharing those. What kind of lube are you using just out of curiousity? Your low-round count bolts seem to be wearing less on the ring behind the extractor.

Thanks. I´ve been using Break Free CLP tad over decade now and I´m not going to change since I have almost endless source...

That 12k bolt looks like it is getting pretty close to the end of its life with the pitting on the bolt face. Are you going to run it to destruction? I'm curious how much more it has in it.

To the bitter end is my goal but still going strong... So far I have only changed gas rings [once], one Wolff EP extractor spring and two buffer springs [every 6000 rds].

Pitted bolt face isn´t reason to reject, I´m more afraid of crack in Cam Pin area.

Pictures taken from the barrel around 10K.

Picture of 10 shot group of 69gr SMK @ 150 meters. Group size 1.260 MOA.

Picture of 10 shot group of 77gr SMK @ 150 meters. Group size 1.673 MOA.

ETA: fixed links

MN

Posted: 10/21/2006 6:24:43 PM EDT

[#3]

see, this is why I only surf this site nowadays.

excellent job.

Posted: 10/28/2006 5:26:16 AM EDT

[#4]

'This presentation (pgs. 43-52) notes that bolts in the M4 carbines subjected to harsh firing schedules show initial cracking at either the cam pin hole or the bolt lugs between 3,000 and 6,000 rounds'

Would this problem also affect regular semi-auto bolts (if there is any difference)? I never heard of such a short life-span for an AR bolt.

Posted: 10/28/2006 9:58:10 AM EDT

[#5]

Quoted:
Would this problem also affect regular semi-auto bolts (if there is any difference)? I never heard of such a short life-span for an AR bolt.

There is no difference between an M16 bolt and an AR15 bolt (unless you figure that the M16 bolt was probably held to certain specs and the AR15 may or may not have been). On the other hand, keep in mind that this was under a "heavy" firing schedule for SOPMOD. I have no idea what SOPMOD considers heavy; but I'm confident that even their "moderate" firing schedule is a long way past the usage that most of us give our ARs.

Posted: 10/29/2006 7:16:08 PM EDT

[#6]

Quoted:

Quoted:
Would this problem also affect regular semi-auto bolts (if there is any difference)? I never heard of such a short life-span for an AR bolt.

There is no difference between an M16 bolt and an AR15 bolt (unless you figure that the M16 bolt was probably held to certain specs and the AR15 may or may not have been). On the other hand, keep in mind that this was under a "heavy" firing schedule for SOPMOD. I have no idea what SOPMOD considers heavy; but I'm confident that even their "moderate" firing schedule is a long way past the usage that most of us give our ARs.

Actually the military defines a "heavy" firing schedule as anything that exceeds the sustained rate of fire 12/15 RPM.

Posted: 10/29/2006 7:18:42 PM EDT

[#7]

Quoted:
'This presentation (pgs. 43-52) notes that bolts in the M4 carbines subjected to harsh firing schedules show initial cracking at either the cam pin hole or the bolt lugs between 3,000 and 6,000 rounds'

Would this problem also affect regular semi-auto bolts (if there is any difference)? I never heard of such a short life-span for an AR bolt.

Colt Armorers course says bolt life is 5,000 rounds if you exceed the military recommended sustained rate of fire of 12/15 Round per minute.

Posted: 10/29/2006 8:57:48 PM EDT

[#8]

Thanks. I will use this info at the next gun show.

Posted: 10/30/2006 12:45:13 PM EDT

[#9]

Actually the military defines a "heavy" firing schedule as anything that exceeds the sustained rate of fire 12/15 RPM.

Exceeds that rate of fire for how long? If you exceed 12-15rpm for 5,000 rounds, then I wouldn't be surprised to hear that barrel erosion and bolts breaking is a serious problem.

Posted: 11/7/2006 7:52:06 PM EDT

[#10]

Great post and an excellent service to the ARFCOM faithful. Thanks!

CWO

Posted: 11/9/2006 11:34:36 AM EDT

[#11]

i agree with some of the later posts, carbn build up just means you are lousyat cleaning your gun, and there are cleaners out there that desolves the brass build up on the extractor and bolt face, and wisk it away, i use these lubes everyime i clean mine.

the smoother worn bolts are clearly more tale-tale of a heavily used weapon, what you should really be looking at is the tolerances on the bolt, mic the sucker down to .0001" and see what the differnce is.

Posted: 11/11/2006 7:36:27 AM EDT

[#12]

Great Pictures! This has been VERY helpful!

Posted: 11/23/2006 4:32:19 PM EDT

[#13]

+1.. I've been an AR fan for years, and never been priveleged to learn what I'm learning now thanks to ARFCOM and tech articles like this. Many thanks, Mr. Roberts

Posted: 11/23/2006 6:46:32 PM EDT

[#14]

I cant believe I missed this thread................Excellent work!

Posted: 11/26/2006 7:55:50 PM EDT

[#15]

tag

Posted: 1/4/2007 7:59:29 AM EDT

[#16]

bumping it to keep it 30 day visible for the new members.

[ARCHIVED THREAD] - How To Determine The Round Count On A Used AR-15 (not 56k friendly) (Page 2 of 2)

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