JP low mass BCG

[hitman]

I was thinking about doing a JP low mass BCG in my next rifle and I wanted to try their silent capture spring but I was curious how they function together. The DD is a little overgassed and ejects around 1-2 o'clock, so I was thinking the low mass carrier may help with the SC spring.

 

[padom]

I've built 12+ 6.5cm gasser with this very combo! Make sure you get the SCS Heavy with the optional spring pack.

I run LMOS and JP HP bolt, PVA 22" rock cut rifled 6.5cm barrel, Superlative tuned to bolt hold open on mag, SCS heavy tuned with second most heaviest spring. Tack driver, super soft shooting and brass looks like it was fired in a bolt gun.

 

[TonyTheTiger]

If it's overgassed now it'll be worse with a lighter BCG. An adjustable gas block is what you need. If you pair that with the low mass carrier you may feel a shorter recoil impulse, which most people describe as less recoil.
The SCS is overrated. It's nice for ease of buffer weight adjustment but it's nothing you can't do with a standard buffer, some different springs and some experimentation. This is all for an AR15 by the way, AR10 could be a different story.

 

[pugnado]

I've built 12+ 6.5cm gasser with this very combo! Make sure you get the SCS Heavy with the optional spring pack.

I run LMOS and JP HP bolt, PVA 22" rock cut rifled 6.5cm barrel, Superlative tuned to bolt hold open on mag, SCS heavy tuned with second most heaviest spring. Tack driver, super soft shooting and brass looks like it was fired in a bolt gun.

I’m gonna try this with my VMOS BCG with steel rings instead of tungsten. What does the LMOS weigh?

 

[SLG]

I'm an issued M4 kinda guy, since that works the best and is the most proven. So with that said, my JP 224V has the SCS buffer setup and it is really nice. Hard to think the old setup is better. The whole gun is just incredibly silky and solid.

 

[Forrest84]

Best combo you can get, but Tony the Tiger is right about needing an adjustable block

 

[pugnado]

Okay I just put the medium 'blue' spring in the heavy SCS and put steel weights on the VMOS BCG.
The VMOS BCG at it's heaviest with two tungsten weights weighs 16.2oz, and 12oz without any weights at all.
My scale died before I could weigh the BCG it with the steel weights, I would imagine maybe 14oz?
The LMOS BCG is 10.8oz according to JP's website.

 

[padom]

I’m gonna try this with my VMOS BCG with steel rings instead of tungsten. What does the LMOS weigh?

Per JP website.

LMOS carrier is 10.86oz.
VMOS Standard (3 Steel Weights) 14.40oz
VMOS Heavy (1 Steel & 2 Tungsten) 16oz

 

[pugnado]

Per JP website.

LMOS carrier is 10.86oz.
VMOS Standard (3 Steel Weights) 14.40oz
VMOS Heavy (1 Steel & 2 Tungsten) 16oz

Thanks! Hopefully I'll be able to get out and tune the gas block again and see how it shoots.

 

[thesteed]

I've built 12+ 6.5cm gasser with this very combo! Make sure you get the SCS Heavy with the optional spring pack.

I run LMOS and JP HP bolt, PVA 22" rock cut rifled 6.5cm barrel, Superlative tuned to bolt hold open on mag, SCS heavy tuned with second most heaviest spring. Tack driver, super soft shooting and brass looks like it was fired in a bolt gun.

I was wondering if I could pick your brain. I have a similar setup. 6.5 creedmoor with JP scs with 3 spring kit, superlative agb, JP lmos bcg with high pressure small firing pin. I shot it for the first time a couple weeks ago. Had the gas block adjusted to hold bolt open on an empty mag, by following the provided instructions. I used the first spring JP suggests.
My problem was that my brass was ejected at about 2 o'clock. It also had a dent about 1/2 way down the case. I have replaced the 2nd heaviest spring. I am planning on a range trip tomorrow. I expect to have to adjust the gas block again to hold open the bolt on an empty mag. Do you have any other suggestions?

 

[BLDTYLRY]

If you are ejecting at 2-o'clock then you are over gassed. Turn down your AGB a click at a time. Make sure your BCG is well lubed in the first 500 rounds.

 

[pugnado]

I was wondering if I could pick your brain. I have a similar setup. 6.5 creedmoor with JP scs with 3 spring kit, superlative agb, JP lmos bcg with high pressure small firing pin. I shot it for the first time a couple weeks ago. Had the gas block adjusted to hold bolt open on an empty mag, by following the provided instructions. I used the first spring JP suggests.
My problem was that my brass was ejected at about 2 o'clock. It also had a dent about 1/2 way down the case. I have replaced the 2nd heaviest spring. I am planning on a range trip tomorrow. I expect to have to adjust the gas block again to hold open the bolt on an empty mag. Do you have any other suggestions?

So you went from not holding the bolt back, to holding the bolt back to ejecting rounds at the 2'oclock?
Maybe go back to a fully closed gas block and work your way up to ejecting with smaller turn increments of the adjustment screw?
(A few clicks, maybe like 1/8th of a turn at a time...)

I think what might be happening is that you are over-gassed and the extraction is so violent that it slams the case against the deflector (which is probably the source of your dent - check it for brass residue) and then the case ricochets off that to the 2'oclock position.

I was able to tune the lighter configured version of the VMOS BCG and the medium spring on the heavy SCS to throw brass at 4'oclock.

 

[Sniper266]

I run a jp scs, lmos carrier with hp bolt and an slr gas block. Id never run anything else unless i was going suppressed. You cant beat the adjustability of the set up.

 

[thesteed]

So you went from not holding the bolt back, to holding the bolt back to ejecting rounds at the 2'oclock?
Maybe go back to a fully closed gas block and work your way up to ejecting with smaller turn increments of the adjustment screw?
(A few clicks, maybe like 1/8th of a turn at a time...)

I think what might be happening is that you are over-gassed and the extraction is so violent that it slams the case against the deflector (which is probably the source of your dent - check it for brass residue) and then the case ricochets off that to the 2'oclock position.

I was able to tune the lighter configured version of the VMOS BCG and the medium spring on the heavy SCS to throw brass at 4'oclock.

Thank you for your input. That was what I was thinking. I don't get to shoot much. Can't wait to get this dialed in.

 

[thesteed]

If you are ejecting at 2-o'clock then you are over gassed. Turn down your AGB a click at a time. Make sure your BCG is well lubed in the first 500 rounds.

Thank you for your advice.