Gunsmithing AR Reliability type question

[AlterEgo]

Guys,

I was reading a report from the 60's or whatever on the HK G3 a while back and something in the report raised a question. Basically the report said that one of the contributing factors to the HK's reliability was that the bolt group had a lot of available overtravel before the carrier hit its rearmost stop. This allowed the rifle's mechanism to deal with shot-to-shot cycling variations within the stroke available to the buffer spring and thus not experiencing bolt bounce (or it would remain 'on the spring').

What this has to to with AR's is that if one were to use a heavier carbine buffer with a rifle length spring in a rifle buffer tube I would think that this would have the same net effect as outlined in the HK above.

This might necessitate having to shim the buffer spring (I would guess at the back of the tube) to get the correct installed spring height, but so what 5 min on the lathe to make a shim.

What do you guys think?

Anyone played around with something like this?

 

[Hellbender]

Re: AR Reliability type question

The buffer length is what keeps the BCG from going too far rearward and striking the buffer tube & lower receiver with the gas key, quickly destroying the lower receiver if allowed to happen.

Are you having functioning problems?

 

[DP425]

Re: AR Reliability type question

There are a great deal of options that a carbine length buffer system already has- you have three standard weight buffers (or is it four?), Spikes makes a tungston powder filled buffer if you want super heavy, there are different springs available. You can even install a regulator gas block. If you can't find a solution to your issues with all of these available combinations, you have a problem beyond what buffer solutions can solve.

The reliability of the AR platform has never came down to insufficient reward travel of the BCG as a design flaw. And as the above post said, you're limited by the gas key's interference. Having just checked one of my AR's, I can tell you that there's only about 1/3" "unused" travel before the gas key contacts the rear of the charging handle.

 

[Hellbender]

Re: AR Reliability type question

The charging handle won't stop a BCG with a carbine buffer in a rifle length tube, it'll pop the CH right back, no problem!

 

[DP425]

Re: AR Reliability type question

Hellbender- that is a good point- it would likely dislodge the the catch. Either way, that makes it only about 2/3" till it hit the lower.

 

[sobrbiker883]

Re: AR Reliability type question

While I like to call the AR platform "lego's for big kids" they are still firearms, and fiddling with the basic operating principles and design should be left to folks that know what they are talking about.
At least you got good info before you tried it at home and dicked up a perfectly good part.

If this is a cure to issues you have, I tend to believe that diddling with buffers (aside from controlling rate in FA) is a bandaid for a gas/timing problem.

oh, and fill out your profile.

 

[DP425]

Re: AR Reliability type question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sobrbiker883</div><div class="ubbcode-body">
If this is a cure to issues you have, I tend to believe that diddling with buffers (aside from controlling rate in FA) is a bandaid for a gas/timing problem.
</div></div>


Agreed- Kinda of like what I mentioned- gas regulating block- if you've got an issue, install a new gas tube, clean out the gas port and install a regulating gas block- make your adjustments to cure cycling problems there. As a plus, if you were over gassed before, you'll end up with a cleaner gun.

 

[scotharr]

Re: AR Reliability type question

I did not see you state the "problem" you are trying to solve with this proposal. I really don't know of anyone with a quality AR that has any reliability issues in need of fixing. One reason you would not want to do what you suggested is you will give the buffer/bcg more of a running start at the bolt stop: resulting in broken bolt stops. This is a problem on the larger AR-10s and is "fixed" by reducing the overrun, not increasing it.

 

[AlterEgo]

Re: AR Reliability type question

I have no issues with my AR's just was a question out of curiosity.

I brain-faded the carrier key hitting the charging handle, but there's always piston uppers...

The thought was to lighten the BCG assembly, provide more travel (and use it) to keep cycle time long with a wider window of port pressures.

Basically there's a balance b/t reciprocating mass, spring, port pressure. Just a different way to look at it.

 

[DP425]

Re: AR Reliability type question

I Don't think a piston upper would do much to change the situation- They replace the gas key with a contact point for an op-rod. So you still have the block of steel bolted to the bolt carrier in the exact same spot.