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New 20" barrel, now it short strokes


Dracomeister
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Might not be the complete OAL, end to end, but the shoulder on the firing pins will definitely be in a different location, for longer bolt and shorter bolt.  That shoulder on the firing pin is what hits the back of the bolt tail when you fire the round, and it's location determines how far that firing pin protrudes through the bolt face, and how much of it goes into the primer surface.

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11 hours ago, 98Z5V said:

Might not be the complete OAL, end to end, but the shoulder on the firing pins will definitely be in a different location, for longer bolt and shorter bolt.  That shoulder on the firing pin is what hits the back of the bolt tail when you fire the round, and it's location determines how far that firing pin protrudes through the bolt face, and how much of it goes into the primer surface.

Measured the firing pins;

Wilson pin is 3.9435" overall and .665" from the back to the face on the shoulder.

AR-10 is 3.942" overall and .591" to the face of the shoulder were the spring is seated. The spring may be a factor here as well.

The wilson does seem to put a pretty good divot in the primer compared to everything else I run so it has good protrusion from the bolt.

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  • 1 month later...

Got these measurements from a Fulton Armory NIB HP BCG (DPMS pattern). Thought it was worth adding the extractor has the same setup as the Armalite, spring with a plug and a doughnut ring on it.

http://www.fulton-armory.com/boltcarriergroupcompletetitanincludesboltcomplete-2.aspx

BC face to Charging Handle notch   ------ -----------------     0.376"

Bolt Length ( AR 10 & spring loaded FP may be different ) --  2.926"

BC face to Gas Key ( interface with Gas Tube ) --------------  0.288"

BC face to end of Gas Key Base ------------------------------  2.764"

BC face to inner Cam Pin slot ----------------------------------- 1.156"

BC face to outer Cam Pin Hole ----------------------------------- 0.462"

Bolt Face to BC face ( locked position , BCG assembled )---- 0.587"

Complete Gas Key Length ( rear base to where Gas Tube enters--2.464"

Edited by jtallen83
added extractor details
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  • 5 weeks later...

When all this sorts out and I have my new(est) gun built, I'll have pics and dimensions of the Fulton Armory chromed BCG (DPMS part), the DWilson BCG, and the Armalite AR-10 BCG, all compared together, and against the standard AR15 BCGs.

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  • 6 months later...
On ‎5‎/‎26‎/‎2017 at 5:40 PM, jtallen83 said:

Got these measurements from a Fulton Armory NIB HP BCG (DPMS pattern). Thought it was worth adding the extractor has the same setup as the Armalite, spring with a plug and a doughnut ring on it.

http://www.fulton-armory.com/boltcarriergroupcompletetitanincludesboltcomplete-2.aspx

BC face to Charging Handle notch   ------ -----------------     0.376"

Bolt Length ( AR 10 & spring loaded FP may be different ) --  2.926"

BC face to Gas Key ( interface with Gas Tube ) --------------  0.288"

BC face to end of Gas Key Base ------------------------------  2.764"

BC face to inner Cam Pin slot ----------------------------------- 1.156"

BC face to outer Cam Pin Hole ----------------------------------- 0.462"

Bolt Face to BC face ( locked position , BCG assembled )---- 0.587"

Complete Gas Key Length ( rear base to where Gas Tube enters--2.464"

I will say... My PSA PA10 GenII supplied BCG is a dead on visual ringer to the Fulton Armory one you linked to.

Same amount of forward assist cuts, and visually indentical.

 

Here are its measurements as best I can...

PSA NIB OEM BCG Measurements ( DPMS Pattern ) as supplied by PSA July 2017

BC face to Charging Handle notch   ------ -----------------     .3845"

Bolt Length ( AR 10 & spring loaded FP may be different ) --  2.925"

BC face to Gas Key ( interface with Gas Tube ) --------------  0.307"

BC face to end of Gas Key Base ------------------------------  2.7685"

BC face to inner Cam Pin slot ----------------------------------- 1.156"

BC face to outer Cam Pin Hole ----------------------------------- 0.4575"

Bolt Face to BC face ( locked position , BCG assembled )---- 0.5865"

Complete Gas Key Length ( rear base to where Gas Tube enters--2.4645"

 

So very slight differences... And some of the longer measurements could just be the coating wearing down, IMHO

 

Ooops... and my BCG doesn't have forward assist cuts clear to the cotter key hole like a WMD .308 Nib BCG.... the various holes are similar... but FA may have spec'd less assist cuts on theirs.

 

 

Edited by bfoosh006
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2 hours ago, Hotwrench said:

Thanks bfoosh006.  Does this mean, in your opinion that FA BCG parts (rings, firing pin etc.) will fit the PA10 bolt?  Anyone else with an opinion on this, chime in please.

    Only way to know is to try them . I had an issues , as has a couple others, with the BCG's we got from a Manufacturer that used to sell his products here . My issue was with a new build ,18" Criterion Hybrid bbl. , I had FTE issues till I changed his Extractor out with an DPMS made Extractor & had no issues after that . Thinking it could be just a Bad Extractor , I used another one from this same manufacturer , it was supposed to be better or a newer gen. , but it had the same issues as the original , so I put the DPMS one back in & all issues with FTE went away .

   There was another here that had issues with same manufacturers BCG & he changed out the Ejector out with an AR 10 one I believe & his issue went away . Many others here had no issues with this Product & its really well made , good looking BCG's , but because of some kind of tolerance stacking between this product & the particular Rifle it was used in , just had issues . 

   Not saying you will have issues with FA products , because I have & still use their components , but you never know with these non spec. builds or rifles, just have to try them & if they are spares , make sure you put them in service for a minimal round count , so you know you can depend on them . 

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46 minutes ago, survivalshop said:

 There was another here that had issues with same manufacturers BCG & he changed out the Ejector out with an AR 10 one I believe & his issue went away

Yep, Armalite ejector spring and the problem went away.

The FA BCG I recently handled was a bit different, the measurements are in the Buffer parts thread recently rediscovered.

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Yeah I saw that thread, great information but no help to me on component size, like rings etc. You are right though I need to try and test, and what works now may next time. This .308AR thing sure keeps life interesting.

Edited by Hotwrench
spell check
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I am going to order a ToolCraft nitrated .308 complete BCG to try in my PSA ... since PSA sells a Cryptic Coatings BCG.. and CC uses Toolcraft, I am "assuming" it will work, but as mentioned earlier... hands on results are ( and measurements ) will produce facts.

I want another spare BCG anyway.... ;)

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  • 9 months later...

Standardization and compatibility is continuing problem?  I have a mutant 24” 6mm Creedmoor R+2 rifle.  Original position of gas tube was like that in Dracomeister’s picture.  First 14 rounds thru barrel became eventful.  Initial three used ADK Defense BCG, seemed to function, switched to KAK BC with Davidson Defense NIB Bolt which was used to set barrel extension.  Rifle failed to eject fired casing on last round of a group.  Dropped it in receiver with bolt in hold back cleared by hand.  During next group it did it again but unnoticed which resulted in casing jam pushing gas tube further forward as shown.  After some zealous advice by members here I purchased a custom length proper gas tube from WOA, third picture.  With new gas tube installed, ADK BCG would not fit in receiver enough to close.  KAK-DD did fit but operated very tight.  Both of these BCGs work in 6.5CM shown in fourth picture.  So I purchased an Aero Precision BCG in hopes it would properly match receiver with new WOA precise located gas tube.

gas tube history.JPG

This thread has a wealth of information exploring issues of a non-standard design.  Seeing the side by side picture here I examined mine the same way.  ADK gas key appears longer.  Is it long enough to prevent receiver closing with new gas tube?  So I thought I’d organize the data in this thread to see where my stuff stands.  First I organized dimensions being collected and then built a matrix of data.

25072488_BCGMeasurementskeyv2.thumb.JPG.c235d00b2d29f728825746e9c416ec4f.JPG

2020519135_BCGmeasurementmatrixV2.thumb.JPG.0557d08f7256dd22660fbb28f2792e53.JPG

Yes, ADK gas key is longer by 0.02, slot is deeper by about 0.05, and bolt closes smaller.  So what does it mean?   What is keeping ADK BCG from seating properly in order to close 6CM AP M5E1 receiver?  AP BCG is fully functional in AP M5 6.5CM and now M5E1 6mm receivers.  ADK is working in AP M5 6.5CM, and the KAK-DD in the M5E1 6.5mm.  So all is well for now.  Why do they work in this one versus that one I don’t know but if it is not broke don’t fix it.

Edited by Phantom30
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  • Matt.Cross pinned this topic
  • 1 year later...

Unless you have chipped brass on the inside of upper, or your bcg is having or causing interference, it's gonna be gas block, especially 80% .... have trust in ODIN...see I have a creedmoore I built and going longer...barrel.... gas can't reset bcg accurately according to grain size...soo your correct length gas tube and say Odins adjustable gas block having correct size needed, can and most def will help with a lot of problems guys think is on the internal inside and it smack in front of their narrow sighted 'viso' !

Forum is to learn even if we think we know, were jus half way there!

Thanks for all the feedback..knowledge is power..

J

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  • 1 year later...

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