Does anyone know if the buffer spring has a specified spring weight? Like a 15 lbs spring for example or does the TDP just go by length?
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Does anyone know if the buffer spring has a specified spring weight? Like a 15 lbs spring for example or does the TDP just go by length?
"Action Spring" . . . I was about to say the buffer has no spring.
Anyway, the spring particulars are:
At a compressed length of 6.90 inches, the spring should develop 5.96 +/-1.0 lbs
At a compressed length of 2.98 inches, the spring should develop 12.12 +/- 1.0 lbs
(You can calculate the spring rate from these two points.)
I never liked terms such as " a 15 pound spring", as it doesn't tell you much, but generally is the load developed at solid height, or the maximum force it can develop. Not very useful. (This would be a 12 pound spring) To confuse things, sometimes the term is used to denote the spring rate, (in which case the action spring would be around 1.5 pounds).
EDIT: That is for the 10.70 inch long, 38 coil, standard carbine spring.
deleted post (it was in error)
Thank you for the numbers and the explanation.
I was trying to do the same thing figuring out the compressed weight of the standard spring vs a flatwire spring. I wanted to get the same weight out of a cut down flatwire to reduce the closing force but still have the longer lasting of flat wire. I was using a rifle buffer extension and a fish scale to pull the spring compressed but the fish scale was not high enough and my bow scale started to high to measure.
Not for nuttin... but why not just buy some extra Colt springs?Quote:
Originally Posted by joedirt199
Cutting coils off a spring increases the spring rate.Quote:
Originally Posted by joedirt199
The standard carbine spring holds the bolt close with about 6 pounds force, when the bolt is fully to the rear the spring develops about 11.5 pounds.
If you clip off two coils, the force holding the bold closed drops to around 4 pounds, and the force with the bolt fully to the rear is about 10.2 pounds.
Your closing force drops a bit, but the force holding the bold closed drops substantially more. It is not something I would not recommend.
Flat wire springs have a lower spring rate than standard spring, they are just considerably longer, so the develop the same pre-load (~6 lbs). Chopping a flat wire spring off gives you the troubles of the reduced coil standard spring (low holding force), and the disadvantages of the standard length round wire spring (high spring rate). Why would you want to do that?
I use this setup and it measured exactly what you said it would in a prior post above, +/- compressed to 3". The length of the cutoff buffer tube measured internally. These pics are about 2 years old from my archives.Quote:
Originally Posted by lysander
https://i.imgur.com/Ri15S8T.jpeg
https://i.imgur.com/ancfRFX.jpeg
A regular uncut receiver extension with buffer installed will measure the other point (6.75").
Pretty cool rig, but again.... why not just buy in spec springs and change them out periodically???Quote:
Originally Posted by the AR-15 Junkie
Because humans are meddlesome creatures.Quote:
Originally Posted by markm
I already owned the gauge for checking Motorcycle valve and clutch springs, so decided to see for myself. And how do you know a spring your buying is in spec?Quote:
Originally Posted by markm
Use a trusted source?
Agreed. The confusion comes from that nobody cares to ask for a precise definition. I tried and got different answers from different people who were supposed to know (spring manufacturers). When pressed, they all ended saying "I'm not sure". Finally I got a good answer from an old timer. The spring's poundage is product of its Hook's constant (lbf/inch) and its natural length. Or it is 100x of the pound force produced for each percent change in length.Quote:
Originally Posted by lysander
The carbine spring in your example
Lo = 10.7", K=1.53 lbf/inch
K*Lo=16.3lbf, or it is a 16 pound spring per this definition.
With that calculation actually becomes even simpler. Again for the same carbine spring, as per the forces given, the install length is 6.8", and the compressed length is 3.2".
1.53*(10.7-6.8)=6 lbf
1.53*(10.7-3.2)=11.5 lbf
Or
16.3*((10.7-6.8)/10.7)=6 lbf
16.3*((10.7-3.2)/10.7)=11.5 lbf
Note that the poundage is independent of the spring's natural length, unlike K, which is handy for calculating shortened spring.
2 coils off 38 coils. The new natural length is
36/38*10.7=10.1"
16.3*(1-6.8/10.1)=5.4 lbf
16.3*(1-3.2/10.1)=11.1 lbf
You can arrive at the same figures with the K method.
The force is weaker, but not really alarming. Actually in a quest to make a "gas assisted straight pull action" I cut the spring of an AR -10 pretty short. No problem, not that anyone should try though.
Does solid height mean compressing spring till it coil binds(cannot be compressed anymore)? According to the old timer who explained spring poundage to me, one should avoid that in use. It could pass the spring's limit and it could take a permanent set. There should be limiter in design that keeps this from happening.
-TL
Sent from my SM-N960U using Tapatalk
NOTE: When counting coils, only count active coils.Quote:
Originally Posted by tangolima
The action spring has closed ends, so the last coil on either end doesn't count - 36 active coils.
Solid height (or solid length) is simply, the number of coils (active and inactive) times the wire diameter, it is as short as the spring can physically be (action spring = 2.74"). If you want your spring to last a long time, you should stay at 130% of the solid length for maximum service defection. For the action spring, this would be 3.56", so its design is a little over-compressed. (Just about all gun recoil and magazine springs are. That's why they have relatively short lives, compared to, say car suspension springs.)
Trust but Verify? Ronald ReaganQuote:
Originally Posted by Uncas47
Is Sprinco a trusted source?
Not for me.Quote:
Originally Posted by the AR-15 Junkie
This is starting to remind me of the grip screw spec thread.
Thanks for the reminder because I've been meaning to ask, has there been any new developments in grip screws lately? I hope not, because I'm pretty settled at this point. ;)Quote:
Originally Posted by Waylander
Do you think self locking thread inserts (HelicoilsŪ) are necessary?Quote:
Originally Posted by 556Cliff
Unless someone stripped out the threads, not really... At least not for the grip screw. I'd like to go with red Nylok patches on all my grip screws (like they have on the mil-spec stock screws), but that would be one heck of a custom order to make. Personally I'm not really a fan of the star lock washers.Quote:
Originally Posted by lysander
I know some manufacturers of FF handguards go the Heli-Coil route for their mounting screws because small diameter threaded fasteners combined with 6061 aluminum threads is a recipe for disaster.
Trijicon also used Heli-Coils on their ACOGs and VCOGs which are 7075 aluminum, but because of people that went to change out the factory mount having issues with the Heli-Coils coming out with the screws due to the threadlocker that Trijicon was using on the screws on installation, they eventually ended up switching to Spiralock thread inserts so they didn't have to use any liquid threadlockers. Of course the torque specs changed along with that change.
I actually use aeroshell, just like barrel nuts. Snugs right up and doesn't back out, also use star washers. Use the same on castle nuts and receiver extensions.
I have considered using the same moly paste I use for barrel nuts, castle nuts, receiver extension threads and muzzle threads on the grip and stock screws. I did use Slip2000 EWG for grip and stock screws at one point, but it was too much of a pain to clean it out of those small 1/4" diameter threaded holes, so moly would be worse yet when it comes to the mess it leaves behind.Quote:
Originally Posted by Uncas47
Currently I just use a heavy dose of Break Free Synthetic Gun Oil for installation of grip and stock screws. Seems to do well with the light installation torque values being applied and there's no mess to clean up if/when I go to take things apart. Oil just blows out with more oil and a blast of air from the air compressor.
I've also tried Loctite blue 243 threadlocker on grip and stock screws. I can't say I was a fan of the removal effort, but those screws certainly wouldn't be coming loose on their own.
I also apply it to the face of the endplate against the castle nut, torque and stake.
https://i.imgur.com/FoKorkW.pngQuote:
Originally Posted by 556Cliff
There were over 250,000 Heli-Coil inserts in every space shuttle. Why? All of the above use lightweight, exotic materials and need strong threads.Quote:
Originally Posted by 556Cliff
https://www.chicagotribune.com/wp-co...5MMY.jpg?w=535Quote:
Originally Posted by the AR-15 Junkie
What about the other 100+ successful flights lol? One blew up due to O ring failures, the other to heat tile failure, nothing to do with heli coils. So really what is your point?Quote:
Originally Posted by markm
Ah, that's actually fairly typical with me. I'm not quick to get a joke. :sarcastic:Quote:
Originally Posted by lysander
Now that's a lot of Heli-Coils.Quote:
Originally Posted by the AR-15 Junkie
Good practice, I do the same. I also apply it to the FSB facing side of the barrel extension flange so that the contacting portion of the barrel nut slides instead of drags against it... It's really a critical step in the assembly process.Quote:
Originally Posted by Uncas47
Yep, couldn't agree more.Quote:
Originally Posted by 556Cliff
Just being a wise ass in that citing the Space shuttle program as any sort of example of excellence is laughable. I mean I remember the tiles falling off on re-entry. Two of them kaboomed, etc. Just classic American Half Ass mediocrity.Quote:
Originally Posted by the AR-15 Junkie
"Hey Bill, it's a little cool out for those shit orings to hold!" ... "Shut up and lauch it Bob. It'll probably be ok!"
As are Sprinco SpringsQuote:
Originally Posted by markm