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The ultimate spring, for this application, would be a mil spec spring that has been upgraded by being shot peened and electro polished. I don't feel that is necessary but if I were trying to create a $20 spring that is what I would do.
17-7 wire costs 2.75x as much as chrome silicon valve spring wire so no one picked it to save money.
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100K+ or several barrels...that's pretty impressive. I've never seen anyone recommend going that long before changing a buffer spring. I've read more than once they should be changed at 8k-10k rounds.
SS does not make a better spring than CS. If, in fact SS is Mil-spec, it must be for other reasons: corrosion, wearing inside RE, galvanic reaction, etc.. But, IMO, I can't imagine the best spring lasting 100K.
But maybe it's just me...
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Yes, music wire is better springiness than 17-7 PH. Mil spec was probably picked for corrosion resistance.
I did not recommend changing the spring at 100k or after several barrels. I said it may last that long. I change them when they no longer meet the force specifications for a new spring.
It is easier to tell people to replace them every 5, 8, or 10K rounds than explain how to test them for remaining life. A good analogy is telling people to change their engine oil every 3K miles rather than have them sample and test the oil.
skimming through, i didn't see this mentioned... in my opinion and experience, XP springs are good for troubleshooting problem guns. i have an extremely over-gassed gun (due to an un-requested port modification at a shop :mad:) that runs too hot with an H2 and standard spring with NATO ammo, too slow with an H3 and standard spring with SAAMI ammo, but runs just right with all ammo with an H2 and XP spring.
for example.
don't put XP spring in guns that function fine. same for "enhanced" bolts and carriers, and some other things.
I also agree that spring modifications have potential merit. If we look at how the AR system operates from an engineering point of view, the buffer spring is partly responsible for slowing down the BCG as it comes back, but perhaps more importantly, it is also responsible for sending the BCG forward and ensuring that the bolt is in battery. Weak buffer springs will not only be less likely to lock the bolt into battery (particularly if sand or other particles are creating more friction than normal), but will also increase the cyclic rate of the BCG. Couple this with a weak magazine spring and some hot ammo (and if you really want to mess things up, an oversized gas port as may be common from lower-tier commercial AR manufacturers), and you have the potential for the bolt closing on an empty chamber because the magazine spring cannot push the round up fast enough to deal with the increased cyclic rate of the BCG.Quote:
Originally Posted by BufordTJustice
In the AR system, timing is very important for reliable function and durability, particularly at the extreme edges of operation. What heavier buffers are supposed to do is slow down the BCG’s movement to the rear to bring guns running more gas (or gas at higher pressures) in line with the appropriate timings for bolt unlocking and soforth. Another reported advantage is increased parts life and reduced recoil, since the BCG moving more slowly to the rear will move more slowly forward (thus reducing the impact forces of the bolt slamming into battery), although admittedly, testing the lifespan of parts can be very difficult.
Now where do I see a spring playing into all of this? Really, I would expect a heavier spring to be a valid substitute for a heavier buffer if done correctly. If done correctly, this will slow down the BCG appropriately as an H buffer would, but unlike just simply putting a heavier buffer in, a heavier spring would also increase the likelihood of the bolt going into battery under conditions where it might not (dry gun, excessive sand, etc). Thus, in theory, using a different spring in the end will result in a more reliable gun as compared to using a heavier buffer.
However, in practice, this is pretty difficult to achieve. A stronger spring can, like anything else, create potential problems. Short-stroking would result if the spring is too strong. Reliability and durability could be affected by springs that aren’t properly treated or have poor QC. Each gas system and barrel length (therefore different pressures and dwell times) would require different spring setups, and running suppressed would affect reliability and durability as well. Spring wear over time would result in changes in the forces involved during rearward and forward movement of the BCG. Bolt bounce, particularly on FA guns (especially SBR’s), could be exacerbated because of the increased velocity of the BCG on its forward return due to a stronger spring. The gun may also be reliable with higher-pressure ammo, but weaker ammo may not be strong enough to overcome the increased resistance caused by a strong buffer spring (and of course, this would change over time as the spring wears out and becomes weaker). Then we have to remember that just because a gun works now doesn’t mean it’s running optimally, and if it’s not, it may work in most cases, but may fail in extreme cases where an optimized gun (in pressure, dwell time, unlock timing, etc) will continue to function.
It’s akin to saying that Bushmasters and Rock River’s are great AR’s. I mean they work for most people right? But why do we consider them lower tier manufacturers even though these guns will work for most people? Because we understand that the engineering and manufacturing processes used in higher tier guns are important for the reliability and durability of the AR platform in relatively extreme cases for most civilian shooters. Most shooters don’t send thousands of rounds downrange every year and don’t depend on their rifles on a daily basis. Thus, many won’t experience problems with their guns for a long time. But even though these guns may work for most people, we understand that they are not on the same level as other manufacturers. The same applies here. Just because your gun may work with a certain setup doesn’t mean it’s running optimally, and just because it works now doesn’t mean it’ll work later at a point where a properly set up AR should be running.
While I think changing springs can theoretically increase the reliability of the AR platform, in practice, with all of the different setups (barrel length, gas system, suppressors, etc) available, it’s just not worth the trouble at this point. Without consistent QC from a spring manufacturer, multiple springs that will be optimal for the multitude of different AR setups available, and the engineering reviewed to ensure proper timing with different spring setups, it’s, in most cases, not worth it to deal with aftermarket springs. Yes, it can work, but it’s much tougher than switching buffers out and requires a lot more finesse. I run a standard spring with an H buffer in my BCM midlength for that very reason, and will generally only suggest buffer changes to deal with timing issues. Different springs can work, and while they can offer more advantages than switching a buffer out, it’s also much easier to screw up. YMMV.
While it's true the heavier buffer will slow down the speed of the reciprocating mass, it's also true it now has more mass. More mass means more kinetic energy. It's likely the slower but more massive reciprocating mass is just as stressful on part life.
Heavier BCGs don't reduce recoil. The only thing it can do increase the duration of the recoil impulse and reduce it's peak- softening a sharp jab to a longer push. Free recoil energy will be the same but felt recoil will be different