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Discussion Starter · #1 ·
Hello,
I'll start my first post by introducing myself. I am a retired 101st AB vet. of 22 yrs., 5 yrs. Private security. To be perfectly honest I have done nothing for the past 3 yrs. but set on my bottom and build hot rods and guns. Somehow sex seems to be low on the priority list now days, but manage to have a good time with my hot rods, guns and kids. My short intro.

The Problem and questions I have from the beginning, I purchased a PTR K3P PDW from Atlantic fire arms that I received this morning, #AW20412 , The gun has a perfect fish and bolt gap [email protected] .016 out of the box. I am not new to the roller lock delayed blowback weaponry by no means, but this one is eating my lunch. After checking the bolt gap, I disassembled the weapon and cleaned the bore and chamber with solvent and soft patches. After reading several other posts, I decided to break in my weapon using a few different brands of ammo. I loaded 10 ,20rnd mags, 2 w/ZQI, 2 w/magtech, 2 w/fed lake city 149 gr., 2 w/Hornaday .308 150 gr., and 2 w/Hirtenberger 146 gr.
I lightly oiled my carrier assy. and started my break in process. to make a long story short after 200 rnds, cleaning bore and chamber after every 5 from start, the every ten to every mag. the weapon only cycled 4 rnds without an FTE. after the first 2 mags The bolt gap was a tight .015, after 100 rnds the bolt gap was at .014 where it is at know after all 200 rnds. The different ammo didn't seem to make a difference, and I have repeatedly cleaned the weapon ,and BCG. came from the factory with a#7 locking piece and the chamber flutes look to be deep and clean.
I have repeatedly tried to call PTR , only to get a recording on all lines. Just asking for advice, maybe something I am overlooking. I have found that after being aggravated for several hrs straight, I sometimes overlook obvious problems. Any advice welcome.
Travis
 

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Did you:
Clean under the extractor?
Clean the slot in the bolt head where the ejector slides?
Lube the ejector in the trigger group so it moves easily?

The bolt gap sounds fine.

Describe FTE. Are the fired cases in the chamber or getting jambed in the receiver by the bolt group?
 

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Put another 200 rounds through it, then buy appropriate rollers to adjust bolt-gap up to around .018-.022" If I start with a bolt gap thats in-spec, I don't sweat it until I've broken in the gun, usually 400-500 rounds.
 

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Discussion Starter · #4 ·
I cleaned the bolt completely after the first 4 mags, under the extractor too. and the trigger pack well lubed.
 

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Discussion Starter · #5 ·
I cleaned the bore with solvents, and the chamber with a brush and solvent, loaded up 5 more mags with only Lake city M80, and it's cycling better now. I'll put 100-200 more through it tomorrow and post an update.
 

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I agree with the others about running some more rounds through it before worrying too much. Did you check the tension of the extracter spring? You shouldn't be able to move the extractor with your finger.

One suggestion though is to not over share as far as personal information goes.
 

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Does the gun have a BCG that's made in the US, or imported? If it's US made, I'd try to borrow a properly made imported BCG first. If that works fine, you know what the problem is. GARY
 

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Discussion Starter · #8 ·
Gary,
I ran ran another 300 rnds through the weapon with the US BCG only to continuously experience the same results, Given not as often but still at least twice in every 20 rnds. . After reading your post, I assembled a BCG using a Rhinemetall carrier, a RCM #18 locking piece, and German bolt with standard rollers,German firing pin and spring. Fired 20 rnds. and would not cycle. After a thorough cleaning of the bore and BCG again, I dropped the BCG back in using a new German #7 locking piece, that yielded a .019 bolt gap. I ran over 300 rnds, using 4 different brands of FMJ ammo without a single issue.
After adding up the BCG cost @ $723 and $1300 for the weapon, and the $$ammo I shot up, I could have had PCS build me a G3K with a German trunion and RCM barrel. Lesson learned.. Thank you Gary
Travis
 

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Well, I am glad to hear you got it running.

The #7 LP you're using is 55deg. The #18 LP is only 50deg. The higher the degrees, the faster it unlocks. So it makes sense to me that you're cycling better with a #18. That LP is intended for 5.56/.223 platforms, so one thing to watch for is roller dimples at the rear of the receiver. Too much recoil and you can cause the rollers to be forced out against the receiver rails at the back.

What ammo were you using?

With regards to cost- in my mind, you just bought yourself some good spares. When you start playing with roller size and locking pieces, you can change too much at one time and chase your tail. Also, shop around when pricing parts. At HKParts.net, I am seeing $590 for all the parts you listed, shipped.
 

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Discussion Starter · #10 ·
The German complete bolt head $389, German #7 locking piece $149, German firing pin and spring $20, Rhinemetall carrier $169, = $727. The RCM locking piece wasn't that bad about $50 or so. These are parts I have purchased over the last few years from Adam, Robert, Midwest, and Brownells. They were upgrades and spares for my German weapons, and all good investments.
Most of my ammo was Federal lake city M80, ZQI from wally world, and Hirtenberger.
 

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The German complete bolt head $389, German #7 locking piece $149, German firing pin and spring $20, Rhinemetall carrier $169, = $727. The RCM locking piece wasn't that bad about $50 or so. These are parts I have purchased over the last few years from Adam, Robert, Midwest, and Brownells. They were upgrades and spares for my German weapons, and all good investments.
Most of my ammo was Federal lake city M80, ZQI from wally world, and Hirtenberger.
Ahh, I was under the impression you went out and purchased these parts specifically for fixing the K3P, I felt bad for you. But yes, that is a good collection of spares to have on hand, especially if you own more than 1 HK roller-lock rifle.

Are you shooting with or without a suppressor?
 

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Discussion Starter · #13 ·
Ahh, I was under the impression you went out and purchased these parts specifically for fixing the K3P, I felt bad for you. But yes, that is a good collection of spares to have on hand, especially if you own more than 1 HK roller-lock rifle.

Are you shooting with or without a suppressor?
No suppressor.
 
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