My first PDW build with Range report

[AbHobbyist]

Hello all!!

I Just wanted to share with you my latest build, which happens to be my first PDW.

For the most part I have shied away from these types of build as I simply failed to see the worth while purpose.

That being said, my good friend Rottwielerboy asked me to build a PDW for him.

We discussed the carbines specs and purpose in detail, and settled on the 7.5" barrel length.

Opportunity was kind to us, and we were able to get all the required parts in short order.

Fist the pictures, with the specs to follow:

Upper

• ATRS Eliminator with Crush Washer
• Noveske 7.5" Heavy profile barrel with 1/7 twist, M4 cuts, and Noveske pinned Low profile gas block with Barrel nut
• Pistol length Gas tube
• Troy Carbine length quad rail
• Areo precision flat top upper reciver w/ FA & DC
• NEA F/A B&C
• Charging handle
• Centurion Diopter sights
• Magpul AFG (Gen 2)

Lower

• Aero Precision Lower
• DPMS Lower Parts Kit (with undesirable parts replace with higher quality spares)
• Ambi-Selector
• Moe Grip+ (rubberized)
• Gapper
• KNS Anti-rotation pins
• Standard Mil-spec Carbine buffer assembly (complete)
• 3H buffer
• Magpul CTR mil-spec carbine stock

There is one note I would like to make. I appreciate that the trend these days is towards slimmer more modular/Key-Mod style free float tubes.

However in this case both Rottwielerboy and I prefer the more substantial older style full quad rail.

Things went according to plan, and we had the opportunity to test this one. The range report will follow.

Thanks for reading my post

AbH

 

[AbHobbyist]

Range Report - Preamble:

Before building one of these PDW/Miro-Barrelled AR’s I did a lot of research. The research seemed to indicate that many individuals were finding several quirks particular to this style of carbine. The general issues found with them are (in no particular order)

-when used in an indoor range, the report will be very loud (make your ears bleed)

-Standing/shooting next to such a carbine will be unpleasant due to concussion/muzzle blast slap, therefore making them a poor choice for two and four man team use/drills

-this style of carbine will have a HUGE muzzle flash (hence the description of being a fire-breather),causing target wash-out, and making it a poor choice for low-light manoeuvres and/or training

- They are very particular about the ammo you feed them, and as a result are unreliable.

At the range

With the above in minded, Maple Leaf Pilgrum, Rottwielerboy, and myself headed off to the Red Deer Shooting Centre to spend most of a day either confirm or disprove the above.

I brought two styles of ammo for testing purposes.

-An ammo can of 62 grain IVI ball ammo I had been saving for just such a purpose

-A partial can of Federal Black box 55 grain ammo (what I basically consider commercial ball ammo)

As for mags the three of us had brought:

-5/30 Mil-spec metal mags

-5/30 P-mag (Gen 2 & Gen3)

-10 round Metal Lar mags (both grey and black finish, with and without mag extensions)

I also brought along my 16" course carbine to act as a control/test carbine. I built this one to be reliable, and is my go-to carbine. So far it has never let me down regardless of what I feed it. It’s current round count is at 1000 rounds fired with out being cleaned, and still going strong. To this point I still lube it, but I have not even wiped the bolt down yet!!

So before we began testing the PDW, I ran one mag full through my 16" course carbine of each of the different styles of magazines and ammunition we brought to make sure there were no magazine to ammunition issues. As expected, my course carbine functioned flawlessly regardless of what style of ammo or magazine was used. While this simple test is not scientifically conclusive, it is in my mind, sufficient for our purposes to demonstrate that there are no magazine to ammo use and fit issues.

Testing the PDW

Testing time had finally arrived. I stepped to the line, slapped in a full LAR mag, pulled the charging handle, let the bolt fly home, and on the third round I had a stoppage.

(The following is my mental process)

Ok no big deal, malfunction drill time. Inspect the chamber, looks like a double feed.
Lock the bolt back, depress mag release, rip out the mag, rapidly actuate the charge handle and shake the carbine.
Stoppage cleared, slap in fresh mag, hit the paddle, were good to go.

Pull the trigger, another double feed. Same drill, another double feed. Time for closer inspection.

Hmm...looks like the extractor on the NEA B&C group is ”jumping over” the spent round rim, travelling back stripping a new round, and jamming the fresh round in to the back of the spent round that’s still in the camber. Must be a week extractor spring, or simply a bad bolt.

Darn NEA .....(many bad words later, and a vow to bring this to SFRC attention as they sold it to me).......well how do we fix this so we can continue testing?

(Report continued in next post)

 

[AbHobbyist]

(Continued from above post)

One thing that I did night before I left for testing was to re-check head space on the PDW both with the NEA B&C, and my course carbine B&C installed in the PDW. This way I could swap B&C groups should there be an issue with either carbine.

As such I removed the NEA bolt and carrier group, tossed it unceremoniously into my tool box (you guys bring tools to the rang right?), and installed the B&C group from my course carbine.

Good to go. Stepped to the line, and emptied three magazines. Ok great, ejection issues solved. The only other issue was a single lack of “bolt hold open on last round” with a one of the metal mags.

I am pretty sure I know what the issue is here........ So I pulled my course carbine B&C group, and installed a brand new Daniel Defence B&C group that I had purchased and prep’ed from the RDS earlier that morning.

For the next 300 to 400 rounds each of us took turns emptying a variety mags as fast as we could get the sights on target. There was not a single issue, and 100 of those rounds was the 55 grain Federal ammo I had brought along. You know the stuff that’s not supposed to work very well in a PDW carbine.

OK great, the carbine works, but what have you learned....

All three of us learned, that in its current configuration:

- with the ATRS Eliminator/Spex style break, Muzzle flash and blast concussion are well directed down range. This give the perception of less muzzle report, and removes the concussion from shooters standing close by. As such I felt confident that this carbine would not adversely effect/distract other shooters should we be working together in a team drills

- with regards to muzzle flash, the internal geometry of the muzzle treatment work well to dissipate it. With the 62 grain ammo, there was no flash, but more like a cone of sparks that emerged from the muzzle. These sparks were simply burning powder granules. With the 55 grain ammo, the effect was similar, but there would be a significant flash every fourth to fifth shot. Both of the above mentioned effects on muzzle flash were confirmed, when the lights were turned out. As such, should night or low-light training be on the agenda, one needs to carefully consider the ammo to be used, so that flash signature is minimized.

-With regards to reliable functioning coupled with magazine and ammunition choice, there really seemed to be no issues. Simply use what you got!!

Alright, the carbine functions well, what’s next....

There are a couple of additional points that my research brought to light that I would like to explore.
(The following excerpts are taken from a conversation with Maple Leaf Pilgrum)

The first point

PDW ARs are solely for defensive use at distances out to 40m or so. In many iterations the round may not have sufficient velocity/energy to tumble once it strikes the target. This makes the weapon ammunition sensitive and they tend to prefer heavier rounds (62-77gr) using a faster burning powders.

The second point

However well made PDWs, with their short stubby barrels, have proven to be boringly accurate out to 300m.

With the above in mind I think the next logical steps would be to test for the validity of the above points. As heavier grained ammunition (above 62 grains) is not common, I for see spending some time at the reloading bench to replicate the “ball style” ammunition, test them again for function, as well as this time include some simple penetration tests, and accuracy tests out at distance.

These are my thoughts and experiences on the above. I will do my best to field any questions comments or concerns, and I look forward to any and all constructive comments you might have

regards and all the best

AbH

 

[AbHobbyist]

Edit: Course Carbine Spec's

I have had at lease one individual ask me for spec’s on my course carbine. This is really a plain, but dead nuts reliable carbine.

As promised here are the pictures, with spec's to follow:

[

Upper

• A2 flash hidder with New crush washer
• DTI 16.1 " Light contour barrels1/9 twist, M4 cuts Chrome lined, A2 front sight assembly
• Carbine length Gas tube with pin
• Good shape but used KAC M-4 Ras (carbine length)
• Delta Ring assembly
• Tango down stubby vertical grip and locking rail panels (FDE)
• Mid West Industires A-2 front sight block flash light mount
• Surefire Mini-Scout 300 weapons light
• Stag S/A Bolt & Carrier group
• Areo Precision flat top upper receiver with Forward Assist & Dust Cover
• Badger Ord. Ambi Charging handle
• Kac Flip up sight (300)
• Aimpoint Comp M4 on a Larue mount

Lower

• Aero Precision Stripped Lower
• Select small parts & spring group
• Colt mil-spec Hammer & Trigger
• Ambi Selector
• Norgon Ambi Mag release
• Magpul Moe+ Grip (FDE)
• Mil-spec 6 position carbine buffer tube assembly
• Magpul ASAP sinlge point sling attachment point
• New Armalite carbine Spring
• 2H buffer
• Magpul ACS carbine stock (FDE)
• Magpul M3 single point sling (FDE)

Mags

• 10 round Lar Mags with extensions

Thx for your interest

AbH

 

[Suputin]

Did you try to run the NEA BCG in a known good rifle to make sure the issue is in the NEA bolt? Did you disassemble the bolt to see if there is a rubber stopper inside the extractor spring?

PDW ARs are solely for defensive use at distances out to 40m or so. In many iterations the round may not have sufficient velocity/energy to tumble once it strikes the target. This makes the weapon ammunition sensitive and they tend to prefer heavier rounds (62-77gr) using a faster burning powders.

The terminal effects issue with a short barrelled carbine is limited to MIL FMJ ammo. As none of you are MIL personnel constrained by the Hague Convention why limit yourself to MIL FMJ ammo? Running heavy bullets in a short barrelled carbine may cause stability and thus accuracy issues because the bullet doesn't reach a high enough velocity to become properly spin stabilized. A better solution would be to go to lightweight varmint style bullets like the VMAX or Ballistic Tip which will not have flight stability issues and which will produce serious terminal effects. In the end this is kinda of a moot argument as this and most other CDN AR15's will only ever be used to punch paper.

 

[AbHobbyist]

Suputin

Thx for stopping buy, and I will try to discuss this your points in your text

Did you try to run the NEA BCG in a known good rifle to make sure the issue is in the NEA bolt?

This is an interesting comment and I want to make sure that I am being clear.

I purchased a pair of brand NEW NEA B&C groups from SFRC.

I used one of them in this build, and upon testing it failed to extract the spent casings properly.

Subsequently a used Stag, and then a New Daniels defence B&C group were substituted, and the issue was resolved.

To my way of thinking the issue was with the NEA B&C group

I have since contacted SFRC, it seems this is a known issue with the batch purchase, and they are sending a new replacement B&C group.

Now from a trouble shooting you are correct, I should have tried the NEA B&C group in a proven carbine like my course carbine.

However, I did not bring my headspace gauges along, and did not feel comfortable swapping bolts with out first checking.

In future I will make sure those gauges are in the tool box.

I will however be testing the second B&C group in the bin to ensure that is does not suffer from the same issues.

Did you disassemble the bolt to see if there is a rubber stopper inside the extractor spring?

I am not aware of any new factory B&C groups that come with the Crane O-ring up grade.

It's my understanding that:

-that upgrade is reserved for well used and worn Bolts or B&C groups.

-applying this upgrade too early may well result in torn case rims amount other things.

Now if your talking about the black plunger that goes inside the spring, at this point I have not taken that bolt apart but will check when I do so.

To be honest, in all the builds I have done, I have not had to trouble shoot a brand new bolt or B&C group.

The terminal effects issue with a short barrelled carbine is limited to MIL FMJ ammo.

As none of you are MIL personnel constrained by the Hague Convention why limit yourself to MIL FMJ ammo?

Running heavy bullets in a short barrelled carbine may cause stability and thus accuracy issues because the bullet doesn't reach a high enough velocity to become properly spin stabilized.

A better solution would be to go to lightweight varmint style bullets like the VMAX or Ballistic Tip which will not have flight stability issues and which will produce serious terminal effects.

In the end this is kinda of a moot argument as this and most other CDN AR15's will only ever be used to punch paper.

This is an interesting point, and I must admit, I had never considered getting proper "velocity envelope" defiintions of the various bullets I planed to use.

I had also not considered using "55 grain and lighter bullets" as a steady diet for this carbine.

However, what your saying makes a lot of sense, and will bear out further testing.

I look forward to spending some time both at the reloading and shooting bench to see how turns out

Thanks for the constructive comments, please keep them coming

regards

AbH

 

[rottweilerboy]

I should add a couple of things to this , Abhobbyist has built a couple of rifles for me in the past , and done some upgrades to one more , they always function flawlessly . So when I decided I really wanted a 7.5" AR built as well there was no question about who was going to get his hands dirty - we'd chatted about this idea some time ago , and I knew he researched the pros and cons of pistol length carbines. As in the previous builds testing proved that again , aside from the bolt and carrier group issue - which was rectified within five minutes - this thing ran like a top . Couldn't be more pleased . Thanks again AbH.

 

[Trinimon]

Cool. Glad you figured out the gremlins easily.

B&C Group... I just call 'em a BCG.

 

[Clobbersauras]

[SUP][/SUP]Great post, thanks for taking the time Ab.

 

[bilkathegerman]

Yep thanks for the post.

 

[redddogg69]

Suputin

Thx for stopping buy, and I will try to discuss this your points in your text



This is an interesting comment and I want to make sure that I am being clear.

I purchased a pair of brand NEW NEA B&C groups from SFRC.

I used one of them in this build, and upon testing it failed to extract the spent casings properly.

Subsequently a used Stag, and then a New Daniels defence B&C group were substituted, and the issue was resolved.

To my way of thinking the issue was with the NEA B&C group

I have since contacted SFRC, it seems this is a known issue with the batch purchase, and they are sending a new replacement B&C group.

Now from a trouble shooting you are correct, I should have tried the NEA B&C group in a proven carbine like my course carbine.

However, I did not bring my headspace gauges along, and did not feel comfortable swapping bolts with out first checking.

In future I will make sure those gauges are in the tool box.

I will however be testing the second B&C group in the bin to ensure that is does not suffer from the same issues.



I am not aware of any new factory B&C groups that come with the Crane O-ring up grade.

It's my understanding that:

-that upgrade is reserved for well used and worn Bolts or B&C groups.

-applying this upgrade too early may well result in torn case rims amount other things.

Now if your talking about the black plunger that goes inside the spring, at this point I have not taken that bolt apart but will check when I do so.

To be honest, in all the builds I have done, I have not had to trouble shoot a brand new bolt or B&C group.




This is an interesting point, and I must admit, I had never considered getting proper "velocity envelope" defiintions of the various bullets I planed to use.

I had also not considered using "55 grain and lighter bullets" as a steady diet for this carbine.

However, what your saying makes a lot of sense, and will bear out further testing.

I look forward to spending some time both at the reloading and shooting bench to see how turns out

Thanks for the constructive comments, please keep them coming

regards

AbH

Check your DD BCG, my DD MK18 BCG has the oring around the extractor spring.

 

[AbHobbyist]

Redddogg69

Thanks you for the heads up, I will have to do that!!

I know that Daniel Defense have really stepped up their game, and perhaps now I have an additional reason to put them on the "preferred to use" Parts list.

To be honest, I was very impressed with how their BCG ran in this shorty, and was thinking of using them in future builds.

Regards

AbH

 

[AbHobbyist]

Hello all!!

I received a very good question via PM, and thought I would share it.

The question was

Anti-Walk pins (also known as anti-rotation pins)

I was just reading your PDW thread.
I noticed that you used them on this build.
I was hoping that you could advise me on whether or not to get some.
Are they necessary or are they a "nice to have" item?.
Thanks in advance.

My general philosophy with small parts when working on AR-15 lowers is individual small part-to lower fit.

Keep in mind that with all manufacturing, there are always tolerance discrepancies, and what may work well in one lower, will not always work or work as well in another.

For example, in this particular 7.5" barreled build I was using a DPMS lower parts kit (they make fine LPK's by the way). However I was replacing parts and springs from my own personal stash when I did not like the fit, or felt something was suspect. In this particular case, I preferred the fit of KNS anti-rotation pins to the fit of the standard trigger and hammer pins.

However when I was building my personal 16" course carbine, I selected small parts from a variety of LPK's and lone parts I had on hand. I found some standard pins that gave me excellent fit, and as such found that an anti-rotation pin set was not needed. This was further proven by participation in a course, and a round count to date of 1k with out issue or cleaning!!

The "feel" for parts fit simply comes with experience, and lacking that, simply trial and error coupled with good note taking!!

So to answer your question, if the pin fit is solid in your lower, and you are confident of this, then by all means use standard pins.

However, if you find that your pins are "walking" then it may be time to replace something, and anti-rotation pins MAY be the answer.

Further, I know that there are a variety of different brands of anti-rotation pins on the market. To date, I have had very good success with the KNS anti-rotation pins, and I prefer the latest generation. They are low profile and unobtrusive.

I hope the above was helpful and informative.

regards and all the best

AbH

 

[Zdragunov]

very informative write up.

 

[AbHobbyist]

Course carbine pictures added!!

 

[redddogg69]

Redddogg69

Thanks you for the heads up, I will have to do that!!

I know that Daniel Defense have really stepped up their game, and perhaps now I have an additional reason to put them on the "preferred to use" Parts list.

To be honest, I was very impressed with how their BCG ran in this shorty, and was thinking of using them in future builds.

Regards

AbH

Just pulled apart my new noveske BCG and it had the oring as well.

 

[heckler]

Good write-up Ab.
I too have over the years went away from the "shorty" but my hankering for another one some day has been perked. My main reason for departure was because of sight picture washout and fellow shooter pity. My other reason is I felt that although useful in some situations, a longer 10.5 -14.5 inch barrel was just easier on all the related parts. A 7.5" just handles so darn nice though in small spaces.

With all that said,..... Nice build. Great details in your write up.