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SHAKEWELLBEFOREUSING

Aero Precision m5 short stroking

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I just built an M5 using all new AP parts:

18" complete upper with rifle gas system

m4 carbine complete lower (came with 7" receiver extension tube, 11" buffer spring, 2.5" buffer at 3.8oz)

AP BCG

 

-The gun does not chamber the proceeding round and will not catch on the magazine on the last round fired.  I'm using federal premium retail ammo.

-The gas port is 3/32"

-The gas tube lines up with the middle of the cam route out.

-The gas block does not seem to be leaking.

-The bcg gas key is tight and staked; shows no signs of leaks.  

-gas rings aren't lined up or damaged

-I've tried the sprinco orange spring and it does not improve anything in this instance.

 

My assumption at this point is that the 11" 26 coil buffer spring is too stiff and/or long?  

I can lock the bolt back manually.  The bolt face is flush with the magazine well rear wall. It does not go farther back.

 

Issue persists with multiple magazines.  The next round always gets scratches from the bolt scraping across its side.  

 

I submitted a ticked to AP,  but I'm sure they're busy right now...

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28 minutes ago, shooterrex said:

I see that when compared to ar10 specs but I don't want to compound a short cycling issue with a heavier buffer at the moment.  I'm not sure how a heavier buffer will help?

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How many rounds have you fired? These large frames needs lots of lube and sometimes a few boxes of ammo to start cycling correctly. 

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5 minutes ago, jtallen83 said:

How many rounds have you fired? These large frames needs lots of lube and sometimes a few boxes of ammo to start cycling correctly. 

About 25...maybe I just need to be patient.

 

I have an AP m4e1 that just friggin runs like a top no matter what. 

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The BCG moves too fast to strip the next round when your buffer is too light.  3.8 oz is too light.  I would fix that first and use the orange spring.  Then lube it up and shoot it.

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I think the 3.8oz buffers are the root of the problem with all the undersized gas ports out there. They tried to lighten the gas to make up for the lighter buffer....nothing but issues as has been proven over and over on this board. I’m sure there are plenty out there that work, but the right port with the heavier buffer seems to be pretty friggin reliable. 

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2 hours ago, Armed Eye Doc said:

The BCG moves too fast to strip the next round when your buffer is too light.  3.8 oz is too light.  I would fix that first and use the orange spring.  Then lube it up and shoot it.

I believe it but the bolt not locking back on the last round confuses me.  

I've got another buffer tube coming.  I'll use my spare h3s and orange spring.  In the mean time I'm gonna manually cycle it until the spring shows a decrease in length and lube it like a threatened catfish.

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31 minutes ago, SHAKEWELLBEFOREUSING said:

I believe it but the bolt not locking back on the last round confuses me.  

I've got another buffer tube coming.  I'll use my spare h3s and orange spring.  In the mean time I'm gonna manually cycle it until the spring shows a decrease in length and lube it like a threatened catfish.

It's running too fast, because the buffer is too light.  It's running so fast that the bolt catch can't even grab the BCG.

Is your new receiver extension 7 5/8" internal depth?  It needs to be, if you're gonna run a AR15 Carbine H3 buffer in it (3.250" long).  You'll need the Sprinco RED spring for that, or you'll need the Armalite EA1095 spring for that.  That's the proper setup, anyway.  7 5/8" internal depth extension, AR15 H3 buffer (5.4oz) at 3.250" length, EA1095 spring (or Sprinco RED spring).  Lube the hell out of it, shoot it, report back. 

This will spell it all out:

 

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12 hours ago, 98Z5V said:

It's running too fast, because the buffer is too light.  It's running so fast that the bolt catch can't even grab the BCG.

Is your new receiver extension 7 5/8" internal depth?  It needs to be, if you're gonna run a AR15 Carbine H3 buffer in it (3.250" long).  You'll need the Sprinco RED spring for that, or you'll need the Armalite EA1095 spring for that.  That's the proper setup, anyway.  7 5/8" internal depth extension, AR15 H3 buffer (5.4oz) at 3.250" length, EA1095 spring (or Sprinco RED spring).  Lube the hell out of it, shoot it, report back. 

This will spell it all out:

 

Noted, that makes total sense.  After all if a round can't make it into the chamber then why would the magazine be fast enough to stop the bolt.. don't know why I thought otherwise.

The current setup is all AP m4 standard 7" buffer tube,  308 buffer spring, and the 2.5" buffer ~3.8oz.  I'll pickup the red spring to match the 7 5/8" internal depth extension buffer tube and h3 buffer.  If that doesn't work then I'm going to just get a full fixed stock system.  This gun would probably be better balanced with that anyways since it has a heavy ss barrel on it.

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Is your tube 7” or 7-5/8”?  I was confused by your post above. That will make a difference on what your solution is. 

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11 hours ago, SHAKEWELLBEFOREUSING said:

The current setup is all AP m4 standard 7" buffer tube,  308 buffer spring, and the 2.5" buffer ~3.8oz.  I'll pickup the red spring to match the 7 5/8" internal depth extension buffer tube and h3 buffer.  If that doesn't work then I'm going to just get a full fixed stock system.  This gun would probably be better balanced with that anyways since it has a heavy ss barrel on it.

That's the exact same as running a fixed stock system/Rifle Recoil System.  If that doesn't work - it means your gas system is jacked up. 

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On 9/15/2020 at 10:54 PM, 98Z5V said:

That's the exact same as running a fixed stock system/Rifle Recoil System.  If that doesn't work - it means your gas system is jacked up. 

I ended up skipping the red spring and getting the complete rifle buffer kit for the 308.  I should have probably just built a fixed stock from the get-go to match the barrel length and gas system.  No doubt it should work at that point.  

Ap customer service did get back to me and made the same suggestions with regards to the specs since I'm mixing a m4 buffer system with a rifle gas system.  They immediately suggested a heavier buffer.  

Since encountering the issue I learned that a rifle length stock and buffer could shoot a lot smoother than m4 carbine so I began to see the positives in the A2 buffers.  That really made me prefer that over just using a heavier buffer.  

I will report back on results after install.

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9 hours ago, SHAKEWELLBEFOREUSING said:

I ended up skipping the red spring and getting the complete rifle buffer kit for the 308.  I should have probably just built a fixed stock from the get-go to match the barrel length and gas system.  No doubt it should work at that point.  

Ap customer service did get back to me and made the same suggestions with regards to the specs since I'm mixing a m4 buffer system with a rifle gas system.  They immediately suggested a heavier buffer.  

Since encountering the issue I learned that a rifle length stock and buffer could shoot a lot smoother than m4 carbine so I began to see the positives in the A2 buffers.  That really made me prefer that over just using a heavier buffer.  

I will report back on results after install.

If you think that, then you're not understanding the mechanics and physics behind all this...   Rifle Gas Systems don't mean you need to run Rifle Recoil Systems - the two systems are independent of each other, completely.  However, both systems need to be balanced.  I've written extensively on this topic, right here on this board.  If you have Carbine Gas - you can run a Rifle Recoil System.  If you have Rifle Gas - you can easily run a Carbine Recoil System.  It's proven.  I've proven it extensively, just on the builds that I have done, for my own personal guns.

Don't believe the hype that you'll read, all over the internet, on this topic.  Most people on the internet are full of shiit.  They haven't done it, tried it - but THEY READ ABOUT IT!...   :laffs:  Right after that, they regurgitated it, on every board that they could find.  :bitchslap:  Just because they READ about it, made it FACT...  Don't believe the hype - there's ALOT of bullshiit out there. 

And you seem to be caught up in it, based on what you're posting here.

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13 hours ago, 98Z5V said:

If you think that, then you're not understanding the mechanics and physics behind all this...   Rifle Gas Systems don't mean you need to run Rifle Recoil Systems - the two systems are independent of each other, completely.  However, both systems need to be balanced.  I've written extensively on this topic, right here on this board.  If you have Carbine Gas - you can run a Rifle Recoil System.  If you have Rifle Gas - you can easily run a Carbine Recoil System.  It's proven.  I've proven it extensively, just on the builds that I have done, for my own personal guns.

Don't believe the hype that you'll read, all over the internet, on this topic.  Most people on the internet are full of shiit.  They haven't done it, tried it - but THEY READ ABOUT IT!...   :laffs:  Right after that, they regurgitated it, on every board that they could find.  :bitchslap:  Just because they READ about it, made it FACT...  Don't believe the hype - there's ALOT of bullshiit out there. 

And you seem to be caught up in it, based on what you're posting here.

 

I don't doubt that you can tune a m4 carbine system to work, but I was taking the previous suggestion to use a rifle system for simplicity as well.   I tried to order a heavier buffer to start with initially but ordered two h3 carbine size buffers on accident, which are too long lmao.  At least I got enough tungsten to replace the steel weights in the rifle buffer.  

 

I got the rifle buffer system in today and the bolt face pulls back behind the magazine bolt catch.  It does not do that with my M4 carbine buffer system.  The bolt catch just catches on the bolt body so that the bolt face is even with the magazine well.  I assume the the M4 carbine buffer system may have other issues than just buffer weight if the bolt can't move far enough back?  

I did take it to the range today with the stock AP rifle buffer weight of 5.6 oz.  It performed a bit better but would only shoot about 3 rounds before missing the next.  Definitely needs a heavier buffer than 5.6oz IMO.  In that sense, I'm happy I didn't order the 2.5" 5.4ox kak buffer.  

 

Progress is progress?

 

 

 

Edited by SHAKEWELLBEFOREUSING

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On 9/19/2020 at 1:40 PM, SHAKEWELLBEFOREUSING said:

I got the rifle buffer system in today and the bolt face pulls back behind the magazine bolt catch.  It does not do that with my M4 carbine buffer system.  The bolt catch just catches on the bolt body so that the bolt face is even with the magazine well.  I assume the the M4 carbine buffer system may have other issues than just buffer weight if the bolt can't move far enough back?  

I did take it to the range today with the stock AP rifle buffer weight of 5.6 oz.  It performed a bit better but would only shoot about 3 rounds before missing the next.  Definitely needs a heavier buffer than 5.6oz IMO

 

 

#1.  Something was definitely wrong with the selection of parts for your carbine recoil system, if it would NOT catch the bolt face.  I'd like more details on exact dimensions of those parts, if you'd like to provide them.  Something was WRONG with the parts, if it would not catch the face of the bolt, and only the body of the BCG.

Rifle buffer weight is 5.4 oz, not 5.6oz, I don't care what any manufactorer is telling you - weight it.  If your rifle WILL NOT FUNCTION with a 5.4oz buffer, in the appropriate receiver extension, with the appropriate recoil spring...

 

 

...   Then you have a gas system problem.

Edited by 98Z5V

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