I just got the new JP 9mm BCG in today and the 9mm Silent Spring should be here tomorrow so I decided to compare it to the CMMG 9mm BCG I currently have.  At first glance they look identical, the finish is pretty much the same on both of them, but I just cleaned and oiled the CMMG yesterday so it's the shiny one in the pics.  The differences I have found are minimal but I will list them anyway.  The pin holding the extra weight in the back of the JP is actually a coiled spring pin and the CMMG is just a hollow roll pin.  This should make the JP less likely to break and accidentally work its way out since it has some extra tension holding it in place.  The other difference I notice is the extractor is silver colored on the JP and black on the CMMG, not sure if it's just the color playing tricks on my eye, but the JP extractor looks a little bigger and the bolt face is shaped a bit differently.  The only other difference I see is the bottom surface of the bolt that provides a contact surface is considerably narrower on the JP, you can see this in the last 3 pics.  The JP measures about 0.25" wide and the CMMG is about 0.33".  This would explain the JP bcg being a tad lighter at 15.6 oz and the CMMG is 15.8 oz. I'm not sure what, if any effect this will have on cycling. Anyone got an idea?

Overall it's a very nice bolt that's not much different from the CMMG.  The CMMG will work with the Silent Spring since you can remove the weight at the rear, so don't feel the need to run out and buy the JP if you already have the CMMG and want to get the Silent Spring.  I haven't decided if I want to keep the CMMG as a spare or just sell it, I will hopefully get to test out the whole system this weekend.

JP is the one on bottom or the right in the pics






This pic probably best illustrates the difference in width of the bottom contact surface

Actually now that I have flipped it over there is a noticeable difference on the left side.  There is a small channel cut out at the front of the JP on the left side.  I have no idea what that could be for????

Just a guess but the slot cutout looks like it is for a non-reciprocating side charging handle

This. Had to put the same cut in my CMMG for the American Spirit Arms upper.

Ah, that makes sense.

Looks like the bottom of the JP bolt may be narrowed for use with Glock mags?

Yes, the JP Bolt has been milled to work with Glock Mags

I got the JP 9mm Silent Spring in today and compared it to my AR 15 silent spring, the 9mm version weighs 13.1 oz and the AR 15 weighs 7 oz.  Overall they are the same length, but the 9mm has more weights on it.  Also the spring on the 9mm is considerably stiffer, probably to make up for removing the extra weight from the BCG.  The whole system with the JP BCG & Silent Spring weighs 25.3 oz and the CMMG BCG, carbine spring & ST-9X buffer weighs 25.1 oz.  If you are using a CMMG buffer the weight is around 23oz I believe.  Hopefully I will get to shoot it tomorrow or Sunday.

9mm on the left

So the JP came ready to go for a GLOCK mag system?  No additional milling required?

No additional milling required.

In what part of Texas do you live dvp18? It's a big place and the chances of us living close to one another are remote, but I'd love to get together and compare your JP captured spring system and my home built version. I built mine well before JP made their 9mm version available and just kind of winged it buy trying to match up the mass of the new verses the old (it had a Spikes ST-9X and CMMG bolt with weight) as close as possible and then trying different spring rates.

Thanks for the comparison. I am going to be building one shortly and I may just sell my cmmg and order the JP instead. Guess I will compare the total price and see how it looks.

It's definitely more expensive than a CMMG BCG and standard buffer. I sold a spare CMMG BCG, buffer and Spikes ST-9X buffer to partially fund the swap.  If I sold my remaining CMMG BCG it would be a wash, but I may keep it as a spare.  Hopefully it will be worth it, I love the one on my 300 blk SBR.  I didn't get to shoot it this weekend, but I should be able to next weekend.

Have you shot your JP and Captured Spring setup yet?  I just ordered the Captured spring to go with my JP 9mm Carrier.

Not yet, I'm in the process of swapping the CMMG lower to a DDLES.  Hopefully I will get to shoot it this weekend though.

I bought one of the silent captured springs and tried it out today.  Worked good, reduced the sound, ejection seems more consistant but that may be from a cleaner bolt.  When I removed the weight from my bolt, I took it all the way apart and deep cleaned the extractor.

Any more reports on function?  Were you able to save any weight compared with a weighted bolt and heavy buffer(Slash)?

Can someone explain the silent spring.  Where to find one and cost?   I'm assuming it does what it says.   I have the spikes heavy buffer and spring, and when I shot mine the first time this weekend suppressed, I could hear the spring.  I'd like to address this

You can order it from Brownells or JP directly.

Ya I did get to shoot it a couple weekends ago, the overall weight of the buffer system is virtually the same as the normal heavy BCG and CMMG 9mm buffer.  I suppose it would be a few ounces lighter than one running of the heavier buffers.  I was trying to fix some feeding issues it was having and it got dark on me by the time I think I got it sorted out, so I wasn't paying a lot of attention to how it felt while shooting it.  It was pleasant to shoot for the most part, but I really need to put the gas deflector on it. with the can and being left handed I get a shot of gas right in the face,  I should have some time to shoot it more this weekend.