Spring/buffer for premature ejection problem on suppressed AR10

[mtrmn]

Using peak carrier velocity and two buffer weights, excluding and ignoring all other frictional forces(drag/hammer, etc.), you obtain the same or very similar KE between a +5.3 oz buffer and an 8.5 oz buffer(plus bcg @20 oz) with only a 6.5% reduction in peak carrier velocity alone. Carrier velocity is not constant in the cycle, the contributing factors are spring(weight) and buffer(weight) differences, if you add buffer and it slows the peak carrier speed down the release of the PE and the creation of KE is less(less felt recoil). There are also naturally occurring speed changes in the cycle of the reciprocating mass when the gun fires(to keep this simple just ignore that). The buffers job is to buffer the initial force on the reciprocating mass, and to slow it and give the spring a chance to absorb and control, then return. The full weight of the reciprocating mass should be considered(bcg & buffer). Full mass ar10 BCG's can vary 2-3 oz from brand to brand(5.3oz could quickly become 8.5 oz and really at that point its not a heavy buffer as its making up for a light carrier possibly).

The other acting force is PE and that relates to the spring, but for this lets say the spring stays the same in both comparisons with two buffer weights. If the carrier is moving faster it has more energy and carries that further rearward where the spring is storing more energy; going slower it travels less and stores less. Hooks law, force needed to compress scales linearly.

If you throw a racket ball against a wall at 50 mph its return force will be X, if you throw it at 75 mph it will be more than X.

With 20 oz carrier figured in:

 

[mettee]

Recoil isn’t a measure of force. It is an Impulse. We also have no idea what carrier velocity is as play here. These numbers have no meaning. It is the de facto experience that having a lighter operating system equates to less recoil than a heavier system, if both are adjusted to cycle correctly.

What is impulse?

So measuring forces play no part in figuring out what's going on, got it, I'll mark that down here in my learning book.

...the figure 12.8 is taken from slow motion camera measuring an ar10 bolt speed.

I'm not arguing how a lighter operating system feels vs a heavy.

 

[mettee]

Use your words.

We could back calculate these numbers...

 

[mettee]

Nobody is going to read that. I didn’t.

It does hurt to think sometimes

 

[USK308]

It does hurt to think sometimes

? Sometimes ? (damn, it hurts my head to think all the time...but then, I suppose that is what I get for riding submarines for a living for 10 years, then working in the Tech Sector for 30+ years! )

 

[mettee]

? Sometimes ? (damn, it hurts my head to think all the time...but then, I suppose that is what I get for riding submarines for a living for 10 years, then working in the Tech Sector for 30+ years! )

Did you work next to the reactor?

 

[Cascade Hemi]

All the major manufacturers have been sciencing wrong.

 

[Shoots 700's]

Switch barrel over to rifle length

 

[mtrmn]

Use your words.

We could back calculate these numbers...

I used the smilies to let you know it was all in fun. The Joe Biden meme was to let you know that facts and/or truth won't have any effect on many here.

 

[FredHammer]

@Squad51 - I've multiple 18" midlength gas BA barrels in 308.
Make sure your buffer spring has 29-30 coils. AR15 springs have 25ish.
Aero sent me AR15 springs in the M5 lower parts kits, so I swapped them for some cheap Anderson Arms 30 coil springs $7 and combined with a 5.3oz buffer, the ejector swipes/gouges went away. I should think this would be the easiest and cheapest route of correction.

On the Superlative GB - I find they aren't the best restrictive GB. I think they do bleed off the best. I should think the bleed off mode is where you would want to be if firing suppressed.

 

[mettee]

All the major manufacturers have been sciencing wrong.

That or they don't build a rifle with the consideration people will make hotter loads for them or add attachments that effect their initial engineering.

 

[mettee]

@Squad51 - I've multiple 18" midlength gas BA barrels in 308.
Make sure your buffer spring has 29-30 coils. AR15 springs have 25ish.
Aero sent me AR15 springs in the M5 lower parts kits, so I swapped them for some cheap Anderson Arms 30 coil springs $7 and combined with a 5.3oz buffer, the ejector swipes/gouges went away. I should think this would be the easiest and cheapest route of correction.

On the Superlative GB - I find they aren't the best restrictive GB. I think they do bleed off the best. I should think the bleed off mode is where you would want to be if firing suppressed.

I think you have something here, this is similar to the rifle 308 spring in the 7-5/8" extension.....

a little longer spring in the same constraint, which elevates the bolt in battery spring pressure by a X(I think springs are from 1.6 to 2.0 lbs per inch?)

If you can not get a spring to handle that initial force and still have it function correctly is that where you would change buffer weights?

 

[hkguns]

Based on what time I have spent here, it seems there should be a separate section for diagnosing screwed up "AR10" builds.

Seems like one a week on here with some kind of gas / build issue.

Do your research before you buy, ask your questions before you build. It really isn't rocket science and isn't as hard as some people seem to make it.

 

[thehun]

Based on what time I have spent here, it seems there should be a separate section for diagnosing screwed up "AR10" builds.

Seems like one a week on here with some kind of gas / build issue.

Do your research before you buy, ask your questions before you build. It really isn't rocket science and isn't as hard as some people seem to make it.

THIS!

 

[Cascade Hemi]

Some days I read forum responses and wonder if I'm taking crazy pills. It's like opposite world. I guess that's just the Internet for you.

I probably just need to science harder.

 

[FredHammer]

I think you have something here, this is similar to the rifle 308 spring in the 7-5/8" extension.....

a little longer spring in the same constraint, which elevates the bolt in battery spring pressure by a X(I think springs are from 1.6 to 2.0 lbs per inch?)

If you can not get a spring to handle that initial force and still have it function correctly is that where you would change buffer weights?

I found for the 7" deep Aero receiver extensions, the 2.5" 5.3oz heavy buffer with the 30 coil spring smooths out the system noticeably, if not perfect. Prior to the spring discovery, the 25 coil spring with the 5.3oz buffer was producing fire & forget brass due to the ejector smear/gouge combo. I was looking for heavier buffers when I came upon my discovery of the spring differences. I figured I'd try the 30 coil and it was the ticket. So, to answer your question, yes a longer/proper length spring will hold the bolt for those nano seconds longer to operate the system better.

The rifle length spring in a 7-5/8" would be something I would try with a 3.8oz carbine buffer first, with a 5.3 on standby. If that is how the 7-5/8" buffers run. I have only experimented with the Aero stuff.

 

[mettee]

Some days I read forum responses and wonder if I'm taking crazy pills. It's like opposite world. I guess that's just the Internet for you.

I probably just need to science harder.

View attachment 8313259

If you "scienced" harder you wouldn't have so many unused springs/parts laying around not in functioning rifles.

Sorry I had to.

I will give you $10 for that heavy buffer

 

[mettee]

I found for the 7" deep Aero receiver extensions, the 2.5" 5.3oz heavy buffer with the 30 coil spring smooths out the system noticeably, if not perfect. Prior to the spring discovery, the 25 coil spring with the 5.3oz buffer was producing fire & forget brass due to the ejector smear/gouge combo. I was looking for heavier buffers when I came upon my discovery of the spring differences. I figured I'd try the 30 coil and it was the ticket. So, to answer your question, yes a longer/proper length spring will hold the bolt for those nano seconds longer to operate the system better.

The rifle length spring in a 7-5/8" would be something I would try with a 3.8oz carbine buffer first, with a 5.3 on standby. If that is how the 7-5/8" buffers run. I have only experimented with the Aero stuff.

From what I have seen the 7-5/8 set up is similar in its function with that 308 rifle spring.

When your rifle was beating up brass did you happen to try and resize any of that brass?

Shooting suppressed or not?

 

[FredHammer]

From what I have seen the 7-5/8 set up is similar in its function with that 308 rifle spring.

When your rifle was beating up brass did you happen to try and resize any of that brass?

Shooting suppressed or not?

I did not. I noticed the primer pockets enlarged also and trashed them for that reason as well. I checked the newly fired cases with the longer spring and primer pockets are ok with no ejector smear. It’s like magic. Lol I haven’t sized them yet.

 

[Jdowns0415]

I did not. I noticed the primer pockets enlarged also and trashed them for that reason as well. I checked the newly fired cases with the longer spring and primer pockets are ok with no ejector smear. It’s like magic. Lol I haven’t sized them yet.

what spring and buffer did you end up going with? I have the JP SCS in my 6.5 creedmoor and I always have ejector smears and ejection problems no matter what setting i put it on with my superlative arms gas block...