View Full Version : I found out the Massoud rifle has a 4 lug bolt
i believe it looks like a 4 lug bolt unless someone can provide more accurate information.
Why don't all new 5.56mm and 7.62mm rifle use symmetrical bolt lugs? Why can't manufacturers get rid of the 7 lug bolt and use a stronger and larger 2-4 lug bolt? (it's not like you can use ar15 bolts in the new rifles that use a 7 lug bolt....can you!?!?).
I was reading on arfcom a thread about parts breaking in carbine courses and There was this bit of info in one of Pat's posts.
"We have seen bolt lugs crack at appx the 10k mark, and the SOPMOD ST 23-31-1 Annex F Para a sub 4 states that "Bolt locking lugs generally have detactable cracks by 5000 to 10,000 rounds and may break at some point between 10,000 and 20,000 rounds".
http://www.ar15.com/forums/topic.html?b=3&f=118&t=360169&page=3
At around 20,000 rounds? That's unacceptable. A bolt shouldn't break that early. All these improvements seen on these new rifles with the rails, ergonomics, modularity, etc, some companies have caught on, while others have still stuck to the 7 lug bolt. It's time to move on.
The website i got these from say they are SMGLee's pics.
http://www.gun-world.net/usa/magpul/masada/dscn1715.jpg
http://www.gun-world.net/usa/magpul/masada/dscn1717.jpg
Why don't all new 5.56mm and 7.62mm rifle use symmetrical bolt lugs? Why can't manufacturers get rid of the 7 lug bolt and use a stronger and larger 2-4 lug bolt? (it's not like you can use ar15 bolts in the new rifles that use a 7 lug bolt....can you!?!?).
It looks like Magpul had the right idea when they decided to use larger locking lugs, but the bolt design still incorporates the cam pin hole in the bolt which is weak point of the design. They should have done what Robinson Arms did with the XCR which is address both the weak locking lug problem, and the weak point created by the cam pin hole:
XCR 3-lug bolt compared to M4 7-lug bolt:
http://i480.photobucket.com/albums/rr169/sgalbra76/boltarxcr.jpg
XCR solid bolt compared to M4 bolt with cam pin hole:
http://i480.photobucket.com/albums/rr169/sgalbra76/boltarxcrtopview.jpg
The third issue that Magpul "could" have addressed was using the spring loaded M16 style ejector, but they didn't. It's not a bad design provided that it doesn't get dirty, and that you change the spring at appropriate intervals. The XCR design went with a solid ejector like the Kalishnikov. Hopefully the Massoud will even hit the civilian market before 2010.....but it probably won't. The new XCR-M which will be chambered in .308 will likely be available for civilian purchase this summer.
Jay Cunningham
02-14-09, 11:49
How many Colt bolts have you seen break? And at what round count?
Failure2Stop
02-14-09, 13:04
How many Colt bolts have you seen break? And at what round count?
I have seen 5 or 6 break- at somewhere between "a lot" and "a whole lot" of rounds- the guns didn't have round counts associated with them at the time- they were M4A1s, about 4 or 5 years old by the time I got my hands on them (2005).
They all broke at the lug, none of them at the cam-pin hole. The only guns I have seen break at the cam-pin hole are the denizens of the right side of the chart. Not saying that no Colts have broken at the cam-pin hole, just none I have personally seen.
Jay Cunningham
02-14-09, 13:07
at somewhere between "a lot" and "a whole lot" of rounds
Right. Don't forget that AR-15 bolts are subjected to heat cycle stresses that bolts on other platforms are not subjected to.
In Colt 5.56, I've personally seen two bolts with cracked or broken lugs at under 20K rounds, and one broken at the cam pin hole at about 30k rounds. I've seen about a dozen pictures of other Colt and FN bolts breaking in those locations from FLETC armorers at under 30k rounds. I don't really have much experience with non 5.56 AR type rifles though. A lot of the FLETC guns are select fire if that makes any difference.
How many Colt bolts have you seen break? And at what round count?
I've never experienced or have seen first hand any failures. But I've seen them all over the net. 100% of the time, it was an ar15/m16 family bolt that broke in two or sheared some lugs.
I would really like some documentation on piston operated rifles of all kinds using the 7 lug bolt and how do those bolts perform in comparison to the bolts using in the DI ar15/m16 family of rifles.
I understand that the ar15 bolt does undergo "long term heat treatment" obviously because of the DI system, and can cause lugs breaking off. But before the cam pin hole goes out? The back of the ar15 bolt gets more heat build up than the head because the gas is being dumped into the carriers little chamber, using the back of the bolt as leverage to unlock and cycle.
When you have lugs breaking off before the cam hole, you know something's wrong with the design.
I want to know if the ar15 bolt's problem is shared with rifles like the ar18, L85, AUG, hk416, m96/stoner 63, etc.
The G36 uses a 6 lug bolt, but uses the same old setup of having a campin go into the bolt. I wonder why HK didn't use a 6 lug in the hk416.
ar18 bolt--------g36 bolt
http://www.gun-world.net/german/hk/g36/bolthead.jpg
hk416 bolt
http://www.gun-world.net/german/hk/hkm4/hkb0038.jpg
Didn't KAC design their new E3 upgrades to change the geometry on the bolt to strengthen the lugs? I know they use a proprietary bolt and barrel extension - there is a radius where the lug meets the bolt body to increase the strength.
Spooky
While we are on the subject of bolts, I have a question about the bolts in the 20" barreled ar15's.
I've read that the 20" rifle bolts don't have near the amount of problems that the shorter M4's have. What exactely is the 20" rifles better at doing? Preventing early lug breakage or early cam pin hole breakage? Or both?
Jay Cunningham
02-16-09, 16:10
While we are on the subject of bolts, I have a question about the bolts in the 20" barreled ar15's.
I've read that the 20" rifle bolts don't have near the amount of problems that the shorter M4's have. What exactely is the 20" rifles better at doing? Preventing early lug breakage or early cam pin hole breakage? Or both?
Off-topic but here ya go: http://m4carbine.net/showthread.php?t=3807
Off-topic but here ya go: http://m4carbine.net/showthread.php?t=3807
Good looking out man, that's one hell of a thread.
variablebinary
02-16-09, 17:44
Good move on Magpul's part.
Provided the metals and heat treatment are good, fewer, beefier lugs will obviously offer more strength and longer life than the AR15's 8 lug design.
I was instructed that the more lugs you had, the more positive lock-up the bolt had, and since the tolerances were so tight thats what made the M16 so accurate.
This of course coming from the same Gunny who said the giant recoil spring in the M16 eliminates recoil.
I don't know why manufacturers aren't going for more triangular bolts. Seems like the perfect solution to the lug breaking problems.
http://www.olarmyjoel.com/images/T2MK5/bolt%20head.JPG
I don't know why manufacturers aren't going for more triangular bolts. Seems like the perfect solution to the lug breaking problems.
http://www.olarmyjoel.com/images/T2MK5/bolt%20head.JPG
What does that bolt go to?
SinnFéinM1911
02-16-09, 21:50
How long do you think bolts should last? Also, are you talking com. semi, or Mil work up's and operational firing schedules? Im not sure you are comparing apples to apples here.
What does that bolt go to?
http://www.olarmyjoel.com/Virtual%20Arms%20Room/australian_leader_dynamics_t2_mk.htm
How long do you think bolts should last? Also, are you talking com. semi, or Mil work up's and operational firing schedules? Im not sure you are comparing apples to apples here.
I don't think I'm comparing apples to apples either. But when I read something how M4 bolts can have lugs break off at about 10-25k, I find that a bit concerning.
There are reasons why the XCR has a 3 lug bolt, the massoud is designed with a new 4 lug bolt, and why the SCAR has a 6 lug bolt, as you corrected me in the other thread. I should ask, "Why does the SCAR use a 6 lug bolt?", but I think the answer is obvious.
Those reasons are to increase the life of the bolt, regardless of the barrel length (in relation to the gas port) , regardless of gas port erosion, etc. The idea is create a forgiving bolt design that can be made of material that's "good enough" and still handle rigorous firing schedules. Or am I wrong?
Finally, how long should a bolt last (lugs and cam pin hole, if a particular rifle doesn't have a milled cam lug). Regardless of the firing schedule, I think a bolt should last up to 100k rounds fired. But I'm no metallurgist or mechanical engineer, so I may be demanding something ridiculous. Then again, this is all purely for educational purposes for me.
As I understand it, most rotating bolt MG's out there have a big 2 or 3 lug bolt. Interesting....
variablebinary
02-17-09, 01:55
Regardless of the firing schedule, I think a bolt should last up to 100k rounds fired
I think that would be a good number, especially for guns with QD barrels.
No one knows for sure when XCR bolts must be replaced. No one has broken an XCR bolt yet.
Robinson's 666 test/demo gun has a round count of 300k on the same bolt, ejector and extractor.
I tried to get Magpul to put a KAC style bolt in the Masada but they didn't listen. :confused:
I think going for 100k round bolt is a stretch. If you also designed the rest of the weapon for 100k rounds (meaning no parts replacement until 100k rounds), it would end up being a semi auto machine gun. The weight necessary to acheive that level of longevity makes the whole weapon impractical. The converse is true: you could also have an AR that weighs 3 lbs. It will probably break at 2000 rounds or the first time you ran through an obstacle course. At some point we have to accept the trade off. Nothing is ever free.
Personally, I'd like the parts to be replaceable in increments that make sense for the user and in quantities that can be done at the same time. Make all the armorer/depot level items replaceable at say 25k or 30k rounds so the user turns the weapon in once every few years for a major overall, rather than every year for just a few components. User level items can be changed out more frequently, but also at similar increments.
To make it easier, as the manufacturer, I'd sell the items in kits, i.e. a 5k round kit would have a couple of springs in it and an extractor insert. The 30k round kit would have a barrel, bolt, and piston in it.
And lets face it, unless you are military or LE, there is little chance you will reach 100k rounds before you sold it off to get the new hotness. If you shot 25k rounds, that's close to $10,000 in ammo alone. Paying for a $100 bolt is small potatoes next to that.
MarshallDodge
02-17-09, 11:48
I think going for 100k round bolt is a stretch. If you also designed the rest of the weapon for 100k rounds (meaning no parts replacement until 100k rounds), it would end up being a semi auto machine gun. The weight necessary to acheive that level of longevity makes the whole weapon impractical. The converse is true: you could also have an AR that weighs 3 lbs. It will probably break at 2000 rounds or the first time you ran through an obstacle course. At some point we have to accept the trade off. Nothing is ever free.
Personally, I'd like the parts to be replaceable in increments that make sense for the user and in quantities that can be done at the same time. Make all the armorer/depot level items replaceable at say 25k or 30k rounds so the user turns the weapon in once every few years for a major overall, rather than every year for just a few components. User level items can be changed out more frequently, but also at similar increments.
To make it easier, as the manufacturer, I'd sell the items in kits, i.e. a 5k round kit would have a couple of springs in it and an extractor insert. The 30k round kit would have a barrel, bolt, and piston in it.
And lets face it, unless you are military or LE, there is little chance you will reach 100k rounds before you sold it off to get the new hotness. If you shot 25k rounds, that's close to $10,000 in ammo alone. Paying for a $100 bolt is small potatoes next to that.
Very well said! I like the 30K barrel kit idea.
I don't see the point in trying to make bolts that outlast barrels by a factor of three.
I don't see the point in trying to make bolts that outlast barrels by a factor of three.
Because it would be one less thing to worry about.
Jay Cunningham
02-17-09, 21:30
Because it would be one less thing to worry about.
A high pressure tested and magnafluxed Colt bolt is very very low on my list of things that I worry about.
Gents,
Keep in mind the Massoud is still a prototype. In fact, that bolt was just one of a number of bolt designs that have been developed. There are advantages and disadvantages to using a greater or lesser number of lugs. Which one is best for your application depends on how much rotation you're working with, bolt thrust, bearing area needed, etc etc. The final version of the Massoud may be just like the pic, or something completely different.
J
Magpul R&D
Massoud,
I take it you are in the loop with Magpul.....
Is there any chance you guys would consider making the receiver and barrel of the Massoud a little longer? My experience with .308 carbines with 16" barrels has been excessive muzzle flash(even with a Vortex), excessive blast, and there is a considerable velocity loss in the .308 cartridge with the shorter barrel. Some cartridges do better with short barrels than others.
That is something I haven't been to crazy about with the new and upcomming wave of .308 rifles. They are all designed around the 16" barrel with a short receiver.
Littlelebowski
02-17-09, 22:33
Massoud,
I take it you are in the loop with Magpul.....
Is there any chance you guys would consider making the receiver and barrel of the Massoud a little longer? My experience with .308 carbines with 16" barrels has been excessive muzzle flash(even with a Vortex), excessive blast, and there is a considerable velocity loss in the .308 cartridge with the shorter barrel. Some cartridges do better with short barrels than others.
That is something I haven't been to crazy about with the new and upcomming wave of .308 rifles. They are all designed around the 16" barrel with a short receiver.
Spot on. 18" should be the standard.
I wouldn't count on the receiver getting any longer, the quad rail does extend rail length though. The barrel length we are working with now is 18". Our primary purpose of this rifle is precision work, like a DMR type rifle, that can also serve as a shorty if needed. I have fired a 13.5 with a muzzle brake and the blast is substantial, yet there are organizations asking for them.
J
variablebinary
02-18-09, 00:01
Massoud,
I take it you are in the loop with Magpul.....
Is there any chance you guys would consider making the receiver and barrel of the Massoud a little longer? My experience with .308 carbines with 16" barrels has been excessive muzzle flash(even with a Vortex), excessive blast, and there is a considerable velocity loss in the .308 cartridge with the shorter barrel. Some cartridges do better with short barrels than others.
That is something I haven't been to crazy about with the new and upcomming wave of .308 rifles. They are all designed around the 16" barrel with a short receiver.
18" sounds like a nice balance. I agree with 16" being a little on the short side.
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