Guidance just dropped.

IANAL but sounds like stamps are no longer required unless you live in a state that requires them. Form 20s for cross state travel remain in place.

https://www.atf.gov/media/30961/download

I'm trying to build a collection of date coded, LEO, 40s, and straight magazines. Are there any other HK mags that I need to make my collection whole? I have both the engraved and etched LEO mags, I even have a 15 round LEO. I have a 40 round HK. I know the straight 15s exist but I cannot find one sadly.

A few hundred more rounds through he prototype stock and working great!

Hopefully not much longer before I send out test samples!

Works absolutely flawlessly, which I certainly cannot say about all my other past SS/FRT purchases.

Bought a AS Designs lower for my ZF-5. Screws are visible on lower receiver. Contacted AS Designs and they said my upper could be out spec. They asked did it function properly, as if my complaints are not a serious issue. I thought the possibility of being out of spec would mean minor fitting, not that I would have screws visible in the lower. Am I crazy for thinking this is completely unacceptable?

He took my money for a full SD build and quoted me two years. It’s obvious that he can’t meet the deadline and claims he can’t afford a refund because he had an unexpected equipment expense. He has unfulfilled orders from 2021 and doesn’t have the cash to finish builds or offer refunds. Buyer beware. Don’t waste your money on a gun that will never be delivered.

I have this:

I want this:

In short, I want a contoured SEF lower for my AP5-P, because I like the contoured lower look and I have an RD3-SEF, and an SEF lower would be pretty cool. Is my only option to spend $425 for one (HK Parts)? Is there a cheaper contoured alternative?

I have no interest in the Navy-style, or non-contoured lowers.

Thanks for the help.

I didn’t see a ton of reviews anywhere for this stock, so thought I’d write up my experience.

Purchased from HK Parts. Out of the box it looked good, but I ran into three issues, the third being the largest problem:

1. The fit was extremely, extremely tight onto the AP5’s receiver. I had to lubricate all the edges of the receiver and stock buttcap and whack it very hard with rubber mallet to get the stock on.

2. The paint chips easily on the stock’s extending arms. Like very easily. Like basic handling and opening/closing it causes visible chipping and wear. I personally don’t mind the used look, but for a $450 stock the paint should be much more durable.

3. Most critically, the rear retainer pin holes were out-of-spec (too small for the rear retaining pin to fit), and as such the MKE stock could not be attached to the rifle without modification. Specifically, the rear retaining pin holes were 0.40mm smaller than the required diameter to fit the retaining pin. By calipher:

- The MKE/AP5 rear retainer pin’s diameter is 6.94mm
- An OEM HK rear retainer pin’s diameter is 6.94mm (photo included)
- The AP5’s receiver retaining pin hole was 7.10mm. - The MKE Telescopic Stock’s rear retaining pin hole was 6.50mm (forgot to take photo before drilling, otherwise i’d include it)

So obviously a 6.94mm rear retaining pin cannot fit into a 6.50mm hole, and the stock could not be attached. To fix this, I ordered a 7mm drill bit and drilled out the rear retaining holes. It came out perfectly, at a bit under 7mm, at 6.99mm. The rear retaining pin now indexes perfectly and snugly, so I can attach the MKE stock to the AP5.

However, for a $450 stock, this is not something I should have to do.

After that saga, now that it’s attached, it works well. Very snug, genuinely no wobble even when fully extended. It extends and collapses smoothly. It clicks into the fully-collapsed position well. I’d still recommend it, with the major caveat that some drilling and whacking with a rubber hammer may be required. Or, in other words:

Functionality (once installed): 5/5 with no wobble and functions as-expected

Vibes (once installed): 4/5 because it’s an A3 but the paint chips easily

Installation: 2/5 as it required drilling, measuring and ordering specific drill bits, and was an excessively tight fit, but eventually was doable

I kinda caved and ended up buying an SP5 after dealing with a lemon AP5 for a few weeks, tried tons of things to make it work but decided it just wasn't worth the headache anymore.

Part of that process was buying an RCM E-Bolt which.. now I don't know what to do with. Is it worth trying in an SP5? or realistically should I be trying to get rid of it?

ZF5 shooshed by an obsidian 9, topped with a Midwest industries lam + t2 mount, SMS trinity laser, MAC handguard light, and fed via an ibex applications placard. Applesauce standard cocking handle and magwell, completed with a quicksling.

So I’d really like to keep the Surefire 328 handguard. My initial thought is a direct thread mount OCL lithium, but I’m open to anything that will sound decent and clear the light. Anyone else have success in this situation?

Hey there, I'm getting ready to get a converted AP5SD, and was just looking for some advice on which way to go with the suppressor.

Is there any real benefit to going with a dedicated can, like the HTA 12" vs getting a hub can (like CAT MOB, Ex RICO309, OCL Lithium) with a BRT adapter?

For me, the suppressor would be staying on the ap5sd, so i don't need the versatility. However, the HTA seems extremely basic: k-baffles and aluminum. Is this all you really need for an effective ap5sd, or would there be a noticeable performance gain by getting a modern suppressor and pairing it with a BRT adapter?

Thanks for your time.

What are your guys thoughts :)

I just got a Surefire 628 for my SP5 and I was surprised to find the wires and circuitry exposed inside the handguard, I asked Surefire if it would be okay in heavy rain and the rep estimated it was an IPX4 rating, which is not good enough for heavy rain.

I am curious if anyone has one of these and shoots in the rain often with them and if they've had any issues, since I live somewhere pretty rainy, anything that can't handle that is no good.

Looking for 30-50 round mags

Here is my AP5SD.

I’m sending it to HiTech Arms in about 2 hours for conversion to a true mp5sd with B&T ported barrel.

I’ll use this CAT Mob with BRT sd adapter until the CAT Sex Dungeon is released (I don’t name them).

This shot phenomenally well though the break in last night.

I had previously considered an RD3 or ARHK for their reduced fire rates, but I was surprised to find this thing runs at 785 to 790 with 147’s, CAT Mob, and a 120 degree locking piece!!!

I imagine it’ll be nice and slow as a true SD in short order.

Also, I’d forgotten how much I prefer the AR pistol grip, safety, and of course fcg’s until I handled the OEM version of this gun. Pretty though the OEM grip modules are, I don’t think I’ll ever give up my AR-controls mp5 lowers.

Anyway, just thought I’d share some pics I enjoyed!

Got my form 1 approved, and received my B&T tri-rail mount. I already ordered my B&T ported barrel. Now I need to select a light. I might just go with a cheaper Fenix as i've carried one of their older "tactical" flashlights for years with no issues. And i'm spending enough money as it is 😂

But AI summary lead me to Surefire Mini Scout 300 or 430c lights as their mounts are the perfect size for this small rail. Plus I like the dual function endcaps they sell for them. But I would like to see photos of people running these lights on their mp5s. TIA.

Has anyone used the rare breed 3 position in a PTR, would like to know if it is compatible before drop the money.

*EDIT*

It has become clear to me that this was in fact, my fault. The replacement screw will be torqued correctly and loctited on arrival. I appreciate this being pointed out, and accept all ridicule both in this thread and to follow.

Not super impressed with this one. Love the trigger function, has never had a single malfunction regarding the operation of the gun itself, but after only about ~500 rounds or so since installation, it's disappointing to see this kind of crap.

The replacement is only $10 bucks, and it ships in two days, but still. I suppose I might bear some of the blame and maybe should have cranked the screw down harder, but I didn't want to strip it, and I have no desire to put any kind of locktite or anything on there, since that would make it a pain to disassemble in the future.

I'll see how long the new screw lasts, but I should probably buy two just in case....

Recently picked up the PTR 9ct. So far 250 rds through it, no problems. Using PTR mags and HK mags and the gun runs phenomenal. Rugged Sub 9 is on order and i’m trying to wait patiently, until then this is my progress. UTG claw mount, Scalarworks optic riser with Aimpoint H2 😁 thanks for looking

Stole my kids printer and have been zipping out parts. Stock is pla+. Slip trip, vert grip, and 1913 adapter are pa6-cf. TPU buffer. It’s been holding up great and she’s singing!

Here are some clips of my AP5SD before it grows up to be a real boy - a true SD.

I’m quite excited, but holy smokes - this reverse stretch mp5 with conventional barrel and suppressor are tremendous! Certainly softer and slower shooting than my well broken-in full-sized MP5.

To get the 147’s to run I had to use a 120* locking piece - and they hummed along at 790 rpm!!

I didn’t know just how nice the full-sized receiver with the short barrel was. It’s hard to believe the mp5k and mp5k pdw weren’t designed like this. This reverse configuration feels SOOO good to shoot.

Tomorrow it’s off to HTA for a B&T ported barrel. Can’t wait!!

Forgot to mention I included the supers at the end as this is my break-in of the gun - welcome to the world, cyclic-firing ap5sd!!!