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ArmaLite Patented Bolts?
6/28/2010 8:38:38 AM
I read somewhere not too long ago that ArmaLite has a patented bolt design for their AR-15's. Is this true? And if so, what is special about them? Thanks. 
6/28/2010 8:52:50 AM
Yes it's true. They have a relieved bolt lug.
TR
TR
6/28/2010 2:04:43 PM
Originally Posted By ArmaLite:
Yes it's true. They have a relieved bolt lug.
TR
Yes it's true. They have a relieved bolt lug.
TR
Gotcha. Thanks!
6/28/2010 6:34:48 PM
The bolt lug opposite the extractor is relieved slightly, in order to reduce the force on the lugs adjacent to the extractor.
6/28/2010 8:18:31 PM
How did they get that patented? There's got to be more to it than that. People have been talking about relieving that lug and relieving that lug for a long time.
6/28/2010 8:24:12 PM
Originally Posted By Essayons:
How did they get that patented?
How did they get that patented?
They filed for it.
For a long time the patent office would issue a patent for almost anything. They gave Amazon.com a patent for "one click shopping", where clicking your mouse would make a purchase, even though untold thousands of websites had offered online shopping before. Now everyone else has to have another webpage after you place your order to "confirm" your order.
Someone filed an application and received a patent on the human neural synapse. So if you think, you are violating his patent.
Someone in silicon valley got a patent on the "enter" key on a keyboard. The list of insane and obvious patents was extensive.
I'm not claiming this patent is frivolous, but at the time it was not difficult to patent almost any concept regardless of prior use.
7/2/2010 7:52:14 PM
May 7, 1996
TECHNICAL NOTE 13: IMPROVED RIFLE BOLT
SUMMARY: The ArmaLite AR-10 rifle bolt bears an unusual improvement which may be mistaken for a
defect: the locking lug opposite the extractor is deliberately relieved at the rear so as not to contact the
locking lug of the barrel extension. This feature strengthens the bolt.
FACTS
1. ArmaLite bolts bear 7 locking lugs, each 22.5 degrees apart from the next. At this angle there should be 8
lugs in a circle, but one lug has been removed to provide space for the extractor.
2. The missing lug creates an asymmetry, or imbalance, in the bolt. When the rifle is fired the pressure of the
cartridge presses the bolt rearward, and the lugs transfer this energy to the matching locking lugs of the
barrel extension. The bolt flexes at the rear inside corner of the lug during this process. Because one lug is
missing, the deformation is greatest in the area of the missing bolt. A series of engineering analyses have
disclosed that the lugs on either side of the extractor each receive 40% of the recoil load.
3. Relieving the rear of the lug opposite the extractor "balances" the loading of the bolt by restoring
symmetry. The load placed on the bolt is spread more evenly over the six remaining lugs. Peak lug loading is
reduced.
4. Relieving the lug opposite the extractor reduces peak loading on the lugs neighboring the extractor from
40% to 24% each. It is not reduced to 16 1/3% (1/6 of the recoil load) because a small asymmetry remains: the
lugs neighboring the extractor are slightly undercut for the extractor, which results in continued relative
weakness at those lugs. Nonetheless, the load on the weakest lugs is reduced 40%, compared to the
standard M-16 design, by spreading a portion of that load to the other 4 lugs.
5. In addition to the relieved lug, the AR-10 bolt bears tapered lugs with wide roots. This puts added
strength exactly where stresses are at their greatest. The AR-10 bolt is significantly stronger than the similar
M-16 bolt. A patent covering both bolt and barrel extension relief is pending.
MAW
Copyright © 1998 ArmaLite, Inc.
TECHNICAL NOTE 13: IMPROVED RIFLE BOLT
SUMMARY: The ArmaLite AR-10 rifle bolt bears an unusual improvement which may be mistaken for a
defect: the locking lug opposite the extractor is deliberately relieved at the rear so as not to contact the
locking lug of the barrel extension. This feature strengthens the bolt.
FACTS
1. ArmaLite bolts bear 7 locking lugs, each 22.5 degrees apart from the next. At this angle there should be 8
lugs in a circle, but one lug has been removed to provide space for the extractor.
2. The missing lug creates an asymmetry, or imbalance, in the bolt. When the rifle is fired the pressure of the
cartridge presses the bolt rearward, and the lugs transfer this energy to the matching locking lugs of the
barrel extension. The bolt flexes at the rear inside corner of the lug during this process. Because one lug is
missing, the deformation is greatest in the area of the missing bolt. A series of engineering analyses have
disclosed that the lugs on either side of the extractor each receive 40% of the recoil load.
3. Relieving the rear of the lug opposite the extractor "balances" the loading of the bolt by restoring
symmetry. The load placed on the bolt is spread more evenly over the six remaining lugs. Peak lug loading is
reduced.
4. Relieving the lug opposite the extractor reduces peak loading on the lugs neighboring the extractor from
40% to 24% each. It is not reduced to 16 1/3% (1/6 of the recoil load) because a small asymmetry remains: the
lugs neighboring the extractor are slightly undercut for the extractor, which results in continued relative
weakness at those lugs. Nonetheless, the load on the weakest lugs is reduced 40%, compared to the
standard M-16 design, by spreading a portion of that load to the other 4 lugs.
5. In addition to the relieved lug, the AR-10 bolt bears tapered lugs with wide roots. This puts added
strength exactly where stresses are at their greatest. The AR-10 bolt is significantly stronger than the similar
M-16 bolt. A patent covering both bolt and barrel extension relief is pending.
MAW
Copyright © 1998 ArmaLite, Inc.
7/3/2010 3:55:14 PM
Wow, that tech note goes so far back that the patent was just pending at the time.
We never heard talk of relieving that bolt back in the day that we initiated the patent, but surely have since we announced it. The idea was generated by the results of a Finite Element Analysis of a bolt failure in the old Eagle Arms days.
We'll update the tech note and put the word about this feature so folks will understand it.
We never heard talk of relieving that bolt back in the day that we initiated the patent, but surely have since we announced it. The idea was generated by the results of a Finite Element Analysis of a bolt failure in the old Eagle Arms days.
We'll update the tech note and put the word about this feature so folks will understand it.
7/4/2010 11:40:43 AM
To be fair to Armalite, the OP makes it sound like this happened recently. Armalite's post, above, clarifies things a lot.
8/17/2010 8:43:54 AM
Originally Posted By ArmaLite:
Wow, that tech note goes so far back that the patent was just pending at the time.
We never heard talk of relieving that bolt back in the day that we initiated the patent, but surely have since we announced it. The idea was generated by the results of a Finite Element Analysis of a bolt failure in the old Eagle Arms days.
We'll update the tech note and put the word about this feature so folks will understand it.
Wow, that tech note goes so far back that the patent was just pending at the time.
We never heard talk of relieving that bolt back in the day that we initiated the patent, but surely have since we announced it. The idea was generated by the results of a Finite Element Analysis of a bolt failure in the old Eagle Arms days.
We'll update the tech note and put the word about this feature so folks will understand it.
By any chance have you had a chance to put together the new tech note?
Ive been wanting to here more about the Armalite improved bolt and its testing for ten years.
TIA
8/19/2010 12:09:05 PM
I emailed the powers that be to look into the update.
TR
TR
8/19/2010 3:08:36 PM
Thanks TR.
