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View Full Version : which H buffer for mid length?


coltn46920
05-27-2009, 5:19 PM
Which heavy buffer should I use for my mid length AR?

CHS
05-27-2009, 5:32 PM
What leads you to believe you need one at all?

What kind of functional problems are you having that you think an H buffer will fix?

aplinker
05-27-2009, 5:46 PM
Contrary to what's on the intardwebz, there's no secret formula for determining what buffer to use.

The best thing to do is to have them all and figure out which works with your preferred loading.

Good mid-lengths should be perfect with a standard carbine buffer.

missiontrails
05-27-2009, 5:53 PM
Won't a H buffer "smooth" things out a little bit in a mid-length? I put an H in my new mid-length build, not for feeding reliability.

Ishoot
05-27-2009, 5:57 PM
Should just be the standard buffer..unless you are having issues with FTE. Try it out first before moving up to the "H" weight class. :)

sreiter
05-27-2009, 6:01 PM
Contrary to what's on the intardwebz, there's no secret formula for determining what buffer to use.

The best thing to do is to have them all and figure out which works with your preferred loading.

Good mid-lengths should be perfect with a standard carbine buffer.

I bought a BCM mid length (16") I asked BCM which buffer - they said regular or H buff

sreiter
05-27-2009, 6:05 PM
Should just be the standard buffer..unless you are having issues with FTE. Try it out first before moving up to the "H" weight class. :)

interesting, I would have thought the opposit

the H is heavier, so it will slow down the carrier when moving back/make the rear stroke shorter....

i would intuitively guess the longer the stroke, the better for extraction. short stroking would play havoc on extraction

just like using heavy springs with wad cutter load in a 1911 - the slide isnt traveling back far enough for extraction

aplinker
05-27-2009, 6:12 PM
It's more complicated than that...

The biggest threat of FTE is trying to extract when pressure is still high in the brass, i.e., before it's had time to contract. Adding mass increases lock time before the carrier starts to move.

It's all a little fuzzy.

BCM should be drilled for a standard buffer - they're pretty smart cookies. An H-buffer would be a good choice if you're planning to run, say, Mk262.

interesting, I would have thought the opposit

the H is heavier, so it will slow down the carrier when moving back/make the rear stroke shorter....

i would intuitively guess the longer the stroke, the better for extraction. short stroking would play havoc on extraction

just like using heavy springs with wad cutter load in a 1911 - the slide isnt traveling back far enough for extraction

missiontrails
05-27-2009, 6:18 PM
Don't complete factory Noveske mid-length rifles come with H?

sreiter
05-27-2009, 6:34 PM
It's more complicated than that...

The biggest threat of FTE is trying to extract when pressure is still high in the brass, i.e., before it's had time to contract. Adding mass increases lock time before the carrier starts to move.

It's all a little fuzzy.

BCM should be drilled for a standard buffer - they're pretty smart cookies. An H-buffer would be a good choice if you're planning to run, say, Mk262.

interesting...again...pure intuitive logic tells me that the heavier buff isnt going to move back into extension as far, therefore "time until extract" is going to be short, therefore the brass wont have as much time to contract

i'm not arguing or even saying i'm right, i'm just sound boarding what my intuition is telling me.

cmace22
05-27-2009, 7:43 PM
It's more complicated than that...

The biggest threat of FTE is trying to extract when pressure is still high in the brass, i.e., before it's had time to contract. Adding mass increases lock time before the carrier starts to move.



Is this what you mean?

More weight = more psi to move it = longer lock time.

Or does it help bleed off gas/psi before trying to unlock.

interesting...again...pure intuitive logic tells me that the heavier buff isnt going to move back into extension as far, therefore "time until extract" is going to be short, therefore the brass wont have as much time to contract



I think your right if you are running a really heavy buffer. If the BCG doesnt move far enough back into the buffer tube, then you could run into many malfunctions including FTE's and FTF's. This is what you tend to see in a wrong gas/buffer combo.

aplinker
05-27-2009, 7:59 PM
interesting...again...pure intuitive logic tells me that the heavier buff isnt going to move back into extension as far, therefore "time until extract" is going to be short, therefore the brass wont have as much time to contract

i'm not arguing or even saying i'm right, i'm just sound boarding what my intuition is telling me.

If the rifle is cycling properly, the buffer bottoms out. That's what it's there for.

You're missing the point that time to extract is a delay between when the primer is ignited and when the casing is pulled, not the time it takes to be extracted.

Desert_AIP
05-27-2009, 8:43 PM
I run an H buffer in my midlengths and an H2 in my carbine gas weapons.

CHS
05-27-2009, 9:36 PM
I run an H buffer in my midlengths and an H2 in my carbine gas weapons.

Specifically, what operating problems did that fix?

gemini1
05-27-2009, 9:44 PM
I'm using an MOE stock with regular buffer/spring on my 16" BCM. 200 rnds of wolf ammo so far, and no problem. Recoil is also bearable, especially for a small shooter like me.

ar15barrels
05-27-2009, 9:57 PM
Which heavy buffer should I use for my mid length AR?

You should not need an H buffer in a mid-length gas system gun.

ar15barrels
05-27-2009, 9:59 PM
The biggest threat of FTE is trying to extract when pressure is still high in the brass, i.e., before it's had time to contract.

Never going to happen in a mid-length unless the barrel was like 20" long.

ar15barrels
05-27-2009, 10:04 PM
interesting...again...pure intuitive logic tells me that the heavier buff isnt going to move back into extension as far, therefore "time until extract" is going to be short, therefore the brass wont have as much time to contract

No matter the weight, the buffer travels all the way until it stops against the end of the buffer tube.
The buffer rebounds off the inside of the tube and then the spring returns it and the carrier forward.
In extreme cases of short stroking, the buffer is no longer hitting the end of it's stroke.
In these same cases you also see failures to feed from the magazine.
If the buffer is not hitting the end of it's stroke, there's not enough time for the ammo stack to advance and the bolt to strip the next round.
There's only 1/4" more stroke in the bolt carier group than is necessary for the bolt head to get behind the next cartridge in the mag.
The time the bolt spends moving past the cartridge head, hitting it's stop and then rebounding is the time that the cartridges have to advance upwards to be stripped off the mag.

sreiter
05-28-2009, 7:38 AM
If the rifle is cycling properly, the buffer bottoms out. That's what it's there for.

You're missing the point that time to extract is a delay between when the primer is ignited and when the casing is pulled, not the time it takes to be extracted.

re-thinking this.....

either way, the case will have more time to cool (but does it really make a diff?)

heavier will cause it to move back slower (unlocked), therefore, it longer until extractor pops out shell -

BUT does fractions of seconds really make a difference in cooling?

again, pure intuition tells me the reason for heavier buff is because you dont want the BCG slamming into the extension too hard/fast

even if lock time was greater, its still fractions of sec's. it takes longer then extract time for brass to cool -

has anyone really ever measured the rate brass contracts and how much it does

sreiter
05-28-2009, 7:39 AM
No matter the weight, the buffer travels all the way until it stops against the end of the buffer tube.
The buffer rebounds off the inside of the tube and then the spring returns it and the carrier forward.
In extreme cases of short stroking, the buffer is no longer hitting the end of it's stroke.
In these same cases you also see failures to feed from the magazine.
If the buffer is not hitting the end of it's stroke, there's not enough time for the ammo stack to advance and the bolt to strip the next round.
There's only 1/4" more stroke in the bolt carier group than is necessary for the bolt head to get behind the next cartridge in the mag.
The time the bolt spends moving past the cartridge head, hitting it's stop and then rebounding is the time that the cartridges have to advance upwards to be stripped off the mag.

makes total sense (after rethinking) - FTF would be the problem

missiontrails
05-28-2009, 7:59 AM
re-thinking this.....

either way, the case will have more time to cool (but does it really make a diff?)

heavier will cause it to move back slower (unlocked), therefore, it longer until extractor pops out shell -

BUT does fractions of seconds really make a difference in cooling?

again, pure intuition tells me the reason for heavier buff is because you dont want the BCG slamming into the extension too hard/fast

even if lock time was greater, its still fractions of sec's. it takes longer then extract time for brass to cool -

has anyone really ever measured the rate brass contracts and how much it does

That's why I have an H in my mid-length, to slightly decrease the amount of trauma to the upper. I shoot only full power XM193, not bargain .223 stuff, so short stroking will not be an issue with the good rounds.

CHS
05-28-2009, 8:14 AM
That's why I have an H in my mid-length, to slightly decrease the amount of trauma to the upper. I shoot only full power XM193

Again, what feeding/operational problems were you having that the H buffer fixed?

You realize that the platform and gas system was DESIGNED for the full-power 5.56 stuff using a standard carbine buffer, right?

ar15barrels
05-28-2009, 8:21 AM
re-thinking this.....

either way, the case will have more time to cool (but does it really make a diff?)

heavier will cause it to move back slower (unlocked), therefore, it longer until extractor pops out shell -

BUT does fractions of seconds really make a difference in cooling?

cooling is not the issue.
The timing we are working with is in milliseconds.
The issue is getting the bullet clear of the muzzle and the chamber pressure dropped before the extraction begins.

I take it that you have not read this yet: www.ar15barrels.com/prod/operation.shtml

It's all explained in there.

PTK-SoCal
05-28-2009, 8:51 AM
Then why does Noveske use H buffers on their Recces?

joe_sun
05-28-2009, 9:04 AM
I use a standard buffer on my BCM upper and so far I've had no extraction issues.

Something strage is with my middy I can't hear the "sproing" like I did with a carbine.

missiontrails
05-28-2009, 9:07 AM
Then why does Noveske use H buffers on their Recces?
+1

I brought that up earlier in this post.

missiontrails
05-28-2009, 9:10 AM
Again, what feeding/operational problems were you having that the H buffer fixed?

You realize that the platform and gas system was DESIGNED for the full-power 5.56 stuff using a standard carbine buffer, right?
If you read my posts, I did not employ the H for feeding/functional issues. Do you think Mr. Noveske employs them in his RECCE's for feeding/funtional problems?

CHS
05-28-2009, 9:21 AM
Do you think Mr. Noveske employs them in his RECCE's for feeding/funtional problems?

Nope, of course not. However, he's the one who specified the gas-port size and is tuning his rifles accordingly, not you.

sreiter
05-28-2009, 9:33 AM
cooling is not the issue.
The timing we are working with is in milliseconds.
The issue is getting the bullet clear of the muzzle and the chamber pressure dropped before the extraction begins.

I take it that you have not read this yet: www.ar15barrels.com/prod/operation.shtml

It's all explained in there.

thanks -

ucla plinker posted something about time for brass to contract - heat expand/cold contract

ar15barrels
05-28-2009, 9:34 AM
thanks -

ucla plinker posted something about time for brass to contract - heat expand/cold contract

the pressure causes the expansion, not the heat.

BigBamBoo
05-28-2009, 9:39 AM
...........

ar15barrels
05-28-2009, 9:50 AM
Randall....have you used or have input on the low mass buffers?

I use and recommend a low mass buffer for 3gun builds where minimized recoil and muzzle flip is desired.
The gas port or gas block needs to be tuned for the ammo and buffer choices.

I modify A2 buffers by removing some weights and re-spacing what's left.

http://ar15barrels.com/tech/buffer-construction.jpg

aplinker
05-28-2009, 10:19 AM
I borrowed a gun with a LW carrier... it's shocking how much of a difference it makes on keeping on target. It made a light gun react like it was twice as heavy... in other words, the light gun didn't move at all, just like my big, heavy bull barreled gun.


Never going to happen in a mid-length unless the barrel was like 20" long.

Of course - it's one of the main reasons for going to mid-length.

My statement was general, not about mid-lengths.

ar15barrels
05-28-2009, 10:27 AM
double-tapping is for post whores.

ar15barrels
05-28-2009, 10:28 AM
double-tapping is for post whores.

:chris:

818gtiguy
05-28-2009, 10:33 AM
double-tapping is for post whores.

ROFL!

PTK-SoCal
05-28-2009, 10:40 AM
Okay so...

Noveske tunes his Recce Middies to run with an H buffer? Is that a fact bdsmchs?

Then if BCM middies work equally well with H buffers does that mean BCM middies are tuned the same way?

So...
BCM and Noveske middies are tuned for H buffer, but that doesn't mean that every middy is tuned for an H buffer? Then it's only okay to use an H buffer on a Noveske or BCM.

Or...
All middies are tuned for an H buffer? Then it's okay to use H buffers on any middy build.

ar15barrels
05-28-2009, 10:45 AM
Noveske tunes his Recce Middies to run with an H buffer? Is that a fact bdsmchs?

Then if BCM middies work equally well with H buffers does that mean BCM middies are tuned the same way?

So...
BCM and Noveske middies are tuned for H buffer, but that doesn't mean that every middy is tuned for an H buffer? Then it's only okay to use an H buffer on a Noveske or BCM.

Or...
All middies are tuned for an H buffer? Then it's okay to use H buffers on any middy build.

Given the known facts, none of these statements can be proven to be correct or incorrect.

missiontrails
05-28-2009, 10:48 AM
Nope, of course not. However, he's the one who specified the gas-port size and is tuning his rifles accordingly, not you.
You sure you don't want to edit that comment? Unless you have some "inside" knowledge about how Noveske "drills" or tunes his gas ports..... Well you get the point. Also, I thought I had some decision making capability at Noveske....

PTK-SoCal
05-28-2009, 11:02 AM
Okay so given the know facts from your article (ar15barrels)

Is it okay to use an H buffer on a middy? Yes or No or it depends?

ar15barrels
05-28-2009, 11:04 AM
Unless you have some "inside" knowledge about how Noveske "drills" or tunes his gas ports.....

I do.

Here's about 215 barrel profile drawings with gas port diameters:

http://ar15barrels.com/gfx/drawings.jpg

Most have multiple gas port measurements noted because I measure and record every barrel that comes through my shop for service work.

ar15barrels
05-28-2009, 11:09 AM
Okay so given the know facts from your article (ar15barrels)

Is it okay to use an H buffer on a middy? Yes or No or it depends?

It depends.

All these play a factor:
port size
barrel length
barrel diameter
lubrication
ammo
carrier weight
spring force
gas block fit
gas tube wear
shooter's position
weather

missiontrails
05-28-2009, 11:25 AM
Randall, I'm gonna start calling you mr. Britanica, you are like a walking encyclopedia.

PTK-SoCal
05-28-2009, 11:26 AM
Putting all of these variables in to account, how do you know when you have the optimum set up for your given gun?

It goes bang, it extracts, it ejects, it loads again with predictable reliability. What evidence would you have other than "it works"? But it might be slightly under gassed or over gassed.

How do you determine the sweet spot?

Do you look at the effects on the brass and how it ejects?

ar15barrels
05-28-2009, 11:27 AM
Randall, I'm gonna start calling you mr. Britanica, you are like a walking encyclopedia.

When I was about 8 or 9, I got in trouble with my mom for staying up late and reading encyclopedias under my blankets by flashlight.
I was on about C or D before she figured out why I was so tired in the morning.

ar15barrels
05-28-2009, 11:30 AM
Putting all of these variables in to account, how do you know when you have the optimum set up for your given gun?

It goes bang, it extracts, it ejects, it loads again with predictable reliability. What evidence would you have other than "it works"? But it might be slightly under gassed or over gassed.

How do you determine the sweet spot?

Do you look at the effects on the brass and how it ejects?

The best way is to start with an undersized gas port and test fire in the conditions you plan to use the barrel.
Then you increase the port size a few thousandths at a time until you obtain proper function.
Then about 0.003" more for good measure.
The sweet spot is when short stroking JUST dissapears.

I also check for free-recoil function as this is different than when the gun is shouldered.
That's where the extra 0.003" helps.

Desert_AIP
05-28-2009, 11:31 AM
You realize that the platform and gas system was DESIGNED for the full-power 5.56 stuff using a standard carbine buffer, right?

Not exactly.
The 5.56 was designed to work with the rifle length gas system in a 20" barrel.

When they went to design a carbine they just cut the barrel and the buffer down to fit into the collapsible stock which itself was just cut down from a rifle size.

Years later, there has been a lot of study, including the thourough one the Navy did, regarding damage imposed to internal parts by the violent action of the carbine gas system. Among other things it was determined the carbine buffer is too light for the carbine gas system.

That is why there the heavier buffers were developed and why all military carbine gas systems run at least an H buffer.
M4s run H buffers and the full auto M4A1s run H2.

In a carbine gas system, the H buffers reduce damage to internal parts.

It's cheap insurance.

PTK-SoCal
05-28-2009, 11:46 AM
The sweet spot is when short stroking JUST dissapears.

Thanks.

But, Most people are buying already built uppers. We wouldn't be fiddling with gas ports.

What would give you an indication that your gun is in the sweet spot for the type of ammo, action spring, and buffer that your are using?

Does the direction of brass ejection and markings on the brass give an indication that you're in the sweet spot?

ar15barrels
05-28-2009, 11:51 AM
Thanks.

But, Most people are buying already built uppers. We wouldn't be fiddling with gas ports.

Look into adjustable gas blocks and adjustable gas tubes.
ANY upper can have all the benefits of a tuned gas system.

Guns with tuned gas systems run real clean too because the excess gas is all flowing out the muzzle instead of into the reciever. :thumbsup:

PTK-SoCal
05-28-2009, 11:57 AM
What adjustable gas blocks or tubes do you recommend?

And what if we are limited to our current set-up? Meaning, we can't change the gas blocks, what then? How can we tune for the sweet spot and what gives the indication that we are in the sweet spot. That's the bottom line.

ar15barrels
05-28-2009, 12:05 PM
What adjustable gas blocks or tubes do you recommend?

And what if we are limited to our current set-up? Meaning, we can't change the gas blocks, what then?

Then change the gas tube.

There's two ways to tune.
Decrease the gas or increase the buffer/carrier weight.
Increasing the buffer weight also increases recoil impulse and muzzle jump.
Decreasing the gas reduces recoil impulse and muzzle jump.