MK109 PWS 300 blk upper

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lugetron
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MK109 PWS 300 blk upper

Post by lugetron »

Finally got my 9.5" MK109 PWS 300 blk upper
It is super light and the rails are very smooth, this upper is the nicest I have owned
I have it installed on a new SBR'd lower which has a standard carbine buffer.
I also used a YHM Phantom .308 can.
I put 90 rounds through it, ran most of them suppressed both sub(A1680) and super(H110) and my subsonic (Hornady 208gr AMAX with 10.5 gr A1680 with OAL of 2.06") reloads unsuppressed must be short stroking because I had to manually rack a round each time. I also shot a box of factory Remington 300Blk Sub 220gr ammo suppressed so I am not sure if they would have locked the bolt back unsuppressed.

Also I had assumed that because this is a piston upper it would be cleaner than gas, I know I should not assume. I had read so many good reviews about its design and that others said it was easy to clean, maybe they shot it unsuppressed?
I noticed that because the piston is attached to the bolt carrier and that the piston gas tube dumps directly in to the bolt area instead of externally pushing back a separate operating rod, it filled the bolt and bolt area with sludge that made it all the way back into the buffer tube that was filthy after the 90 rounds. The single hole that vents gas down on to the barrel had very little build up if any compared to the inside of the upper which makes me think the piston/bolt never moved far enough back to vent the gas downward which forced it around the piston and into the bolt area.

I use the same YHM Phantom on two 16" POF piston AR's and an 11.5" Adams Arms and the POF bolts both get the black watery suppressor juice on them while the Adams stays impressively squeaky clean and and never have I had to clean out the buffer tubes on any of these three.

I know I need to work on some different sub loads but do I need a different buffer weight?
Any other suggestions??

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"You don't need any more cans" -My Wife:)
nolwark76
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Re: MK109 PWS 300 blk upper

Post by nolwark76 »

This is the exact upper that I am saving for. I just ordered a stripped lower to start the SBR build process. I saw this post so I just called and talked to PWS. They answered right away, I wasn't stuck in a phone tree. I have no experiance with PWS but that right there tells me a lot. Unlike Para Ordnance's customer service...still dealing with them after a year...anyway.

The technical support guy I talked to said that UNsuppressed they had a guy torture test a Mk107 rifle and it went something like 11,000 rounds with only a bore snake through it every 1,000 before it got dirty enough to have a malfunction. No lube on the BCG, just the snake. Wow.

Here's what he said about the dirty BCG. With a suppressor on, the can creates backpressure and gas gets blown back into the chamber through the barrel. It's not from the piston system it's the can. I'm not insulting you but have you looked at the difference between supressed and unsupressed with a DI system? Big difference from my experiance. My DI rifles are mildly dirty without a can, but down right filthy with one on. I thought it was more gas coming back through the gas tube but I guess not.

The other thing he said is that in all Mk1 rifles, you shouldn't feel the gas venting so mounting any goodies or holding it anywhere should not be a problem.

Thanks for the post, I was curious myself. He said he would recommend anyone with a question to give them a call and then post their expericanes with the fix to the forum. I'm sure you've gotten crazy replies to questions posted on forums just like I have.
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lugetron
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Re: MK109 PWS 300 blk upper

Post by lugetron »

nolwark76 wrote: Here's what he said about the dirty BCG. With a suppressor on, the can creates backpressure and gas gets blown back into the chamber through the barrel. It's not from the piston system it's the can. I'm not insulting you but have you looked at the difference between supressed and unsupressed with a DI system? Big difference from my experiance. My DI rifles are mildly dirty without a can, but down right filthy with one on. I thought it was more gas coming back through the gas tube but I guess not.

Hi Nolwark
It is a very Nice upper machining is very smooth, no sharp edges and best of all very very light! I talked to them Tuesday and Stacy was not there but yes I agree they were very easy to get in touch with and very willing to help out which is nice to know for anyone else want to purchase in the future.
Right now I have just been shooting my own hand loads with primarily A1680 and and more recently H4198, which I have been told is cleaner, so i think it could be due to the powder being dirtier.
and of course cans make things much more messy. My DI upper with a can was really bad so I bought a POF upper and its piston system and has a completely separate operating rod that pushed on the BCG. when shot with a can the only thing that gets dirty is the bolt around the lugs from the suppressor juice streaking back toward the BCG. this is due to the additional back pressure from the suppressor. based on what he said one question I have is why do my three other piston systems have adjustments to greatly reduce the amount of gas pressure on the piston when using a suppressor?


I bought this because piston systems I own are much cleaner than DI and the AK piston system is proven. Best of everything. I even bought a YHM titanium can to complement how light the PWS upper is.

http://www.pof-usa.net/technical/gasplusorientation.htm
http://www.youtube.com/watch?v=a1gBnGOi ... re=related

Between the first and second trip to the range I installed a small rubber o-ring that sat just in front of the charging handle. after checking to make sure it would not interfere with operation of the piston or charging handle i put about 250 rounds through it and the BCG was much cleaner and you can see in the pic were the o-ring sat and where the build up was just forward of it.
Overall it operated great! no problems other than the brass catcher getting to full. upping the powder in the sub loads made all the difference while suppressed!
I plan on calling them to find out specifically what ammo they used.
Thanks for the info!!
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"You don't need any more cans" -My Wife:)
nolwark76
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Re: MK109 PWS 300 blk upper

Post by nolwark76 »

Ver cool. I can't wait to get my SBR and start shooting it. I'm impressed at the support for this new caliber. It's a new ninja commando caliber that kicks but, can be found loaded for a reasonable price and there is also loaded ammo for HD use in tons of flavors! So glad I came across this caliber. I'm eager to learn as much about the right components so that I can maximize my dollars.

I'd like to find ammo my rifle will like as soon as possible and then stock up. I am not buying a 9" rifle to shoot groups with. I have other precision toys for that. However, what kind of groups are you getting with your 9" upper? Are you holding 2 MOA or better?

I'd like to find a good training load/round, a good hunting/self defense load and round, and a good sub sonic load and round. Hopefully I won't end up with a ton of different loads and bullets. I'd like to basically have a super and a sub sonic zero. This is the problem we all face with AR type rifles as there are so many choices out there finding one or two so that you can actually be effective with the rifle is a chore...but a fun one!
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lugetron
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Re: MK109 PWS 300 blk upper

Post by lugetron »

nolwark76 wrote:Ver cool. I can't wait to get my SBR and start shooting it. I'm impressed at the support for this new caliber. It's a new ninja commando caliber that kicks but, can be found loaded for a reasonable price and there is also loaded ammo for HD use in tons of flavors! So glad I came across this caliber. I'm eager to learn as much about the right components so that I can maximize my dollars.

I'd like to find ammo my rifle will like as soon as possible and then stock up. I am not buying a 9" rifle to shoot groups with. I have other precision toys for that. However, what kind of groups are you getting with your 9" upper? Are you holding 2 MOA or better?

I'd like to find a good training load/round, a good hunting/self defense load and round, and a good sub sonic load and round. Hopefully I won't end up with a ton of different loads and bullets. I'd like to basically have a super and a sub sonic zero. This is the problem we all face with AR type rifles as there are so many choices out there finding one or two so that you can actually be effective with the rifle is a chore...but a fun one!
I read on here that the hodgdon load data center has 300 AAC Blackout so I started with that for the supersonic http://data.hodgdon.com/cartridge_load.asp

all of these were shot at 50 yds with just the Eotech no magnification
My best load is:
110 GR. HDY V-MAX Hodgdon H110 2.040" 19.8gr $6 per 20
125 GR. NOS BT " " 2.060" 17.7gr $8 per 20
Compare that with the $36 a box of 20 for the rem 125gr OTM :shock:

I bought some Hornady 225gr BTHP and I will post all of my subsonic results for the 208 gr and 225 gr soon
I also bought a spikes ST-T1 buffer since the 208subs did not like the T2 buffer


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110gr Vmax (not 115gr Amax as seen in pic)
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USBP379
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Re: MK109 PWS 300 blk upper

Post by USBP379 »

Are you pleased with the purchase, overall?
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lugetron
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Re: MK109 PWS 300 blk upper

Post by lugetron »

USBP379 wrote:Are you pleased with the purchase, overall?

Yes
"You don't need any more cans" -My Wife:)
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USBP379
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Re: MK109 PWS 300 blk upper

Post by USBP379 »

lugetron wrote:
USBP379 wrote:Are you pleased with the purchase, overall?

Yes

Cool. Mine's been on order for a short while and is scheduled to arrive Wednesday. I'm looking forward to it.
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