View Full Version : JP Low Mass bolt carrier with VLTOR A5?
I'm working on a new build for 3 Gun. I was planning on using a BCM BCG along with a VLTOR A5 tube and buffer, and an adjustable gas block. I have another rifle set up this way and it works very well. For the new build I was considering a JP low mass carrier (6.68 oz) Will it work ok with the A5 system? Doesn't seem like many 3 gunners use the A5, so I'm not sure how it works with lighter carrier groups. Anyone using this combo? Also is the low mass carrier worth the extra $? Seems like a middy with an A5, adjustable gas block, and good comp is going to shoot pretty soft as is.
I have no direct experience using that combination, however, my instincts tell me there isn't likely to be enough mass in that BCG to work properly with an A5 setup. Hopefully someone with direct experience can give you the real scoop.
My reason for posting is that "I" think you'll be better served by shooting a "real" rifle in those games. When I shot IDPA, I always shot a bone stock USP45c in the service pistol class. I didn't do a lot of winning, but I learned to use the tool very effectively. What are you really going to win anyway? In my view you can get valuable trigger time competing in those games, but only if you don't make it like you're not actually shooting a real gun.
YMMV
I haven't used the A5 system but I can tell you that the JP LMOS bcg is designed to use lightweight buffers like JP's own buffer system, a carbine buffer, lightened rifle buffer or taccom's lw setup.
I would consider using the JP buffer system as it works very well with their LMBC and a adjustable gas block to tun the rifle.
Thanks for the replies. I think I'll just run the BCM BCG for now. I'd rather it be 100% reliable as opposed to running it on the ragged edge of what will work. I also have an AR15 carrier I can use in place of the M16 carrier, that will shave at least a little weight off the carrier.
100 percent reliable is hard to beat in real life or 3gun.
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There are some indications that in the balance of total reciprocating mass being the same and properly done for a given system, that maximizing buffer mass while keeping total mass the same by reducing carrier mass may have some merit. Adding mass to the buffer while reducing the same mass from the carrier has shown advantages, total mass stays the same.
I have run a JP Low mass carrier with an A5 on a KAC SR15 upper. I also used it with carbine, H, and H2 buffer set ups, and a lighter A5 (3.X .oz) buffer a I made and used when running the A5.
It worked, I used it as a way to further lighter the reciprocating mass as a whole (bcg+buffer), I had trouble with my SR15 cycling some lighter loads with a full weight mil-spec carrier and even a carbine buffer. Since I couldn't go any lighter on the buffer I had to remove weight from the carrier. The effect was as desired, to 'tune' it I actually ended up going up to an H buffer, which still had a lower total reciprocating mass than a milspec carrier+ carbine buufer.
The way I think about it is total reciprocating mass, that is where the majority of the effect of cycling will be. With some exception.
There are some indications that in the balance of total reciprocating mass being the same and properly done for a given system, that maximizing buffer mass while keeping total mass the same by reducing carrier mass may have some merit. Adding mass to the buffer while reducing the same mass from the carrier has shown advantages, total mass stays the same.
I would to like hear what the mechanics of this are and the effect you are referring to? It is a subject I wish I knew more about. At this point I removed the carrier from that gun, and replaced it with a LMT enhanced BCG. The gun still doesn't really like those light rounds with the enhanced carrier, so I have decided to just run real ammo.
The only reason I ditched the JP carrier, which in ways worked better was because of potential reliability issue that it could cause. I had read, and based on physics it made sense to me, that for extraction it is better to have the weight from the total reciprocating mass be in the carrier. The theory behind this is because the buffer is not connected to the bolt and there for the case its inertia does not help to pull the case from the chamber. What do you think of this?, what was your idea of the positive could be?
I'd ultimately like to put that JP carrier back in that KAC rifle as otherwise I have no real use for it. Were my concerns unfounded, could I actually benefit in a way I don't know?
Thanks.
Out of the few plausible times that the buffer face doesn't maintain tension to the carrier, it couldn't really apply when talking about sane carrier velocities for 99.9% of users with an A5 during extraction. The internal piston of the BCG pushes the carrier back, resistance to unlocking and extraction does not stop or really slow down the carrier at that point in a normal system. If the system runs into more resistance in those points, the action will not have full travel in its range of operation in a balanced system.
Using a higher ratio of buffer mass can improve control carrier bounce and other items, given the same total reciprocating mass.
I would be careful, make sure you use an E3 bolt with an E3 BE in your LMT enhanced BCG.
Tuning for junk ammo isn't a game I want to be in. I prefer to work with something that myself would be more normal.
Thanks for the replies. Am I correct in thinking if I want to use the LM carrier w/ the A5 I probably need to reduce the buffer weight? I currently have the A5H2 (5.33 oz). I was thinking maybe the A5H0 (3.8) would work for my intended use. JP sells a rifle buffer that is 3.0 oz for use with LM carriers, so I think 3.8 would get me pretty close and then I could tune the gas from there.
What's your desired outcome with both the lightweight BCG and the A5 system?
With a light BCG/buffer, a heavier recoil spring, and adjustable gas block (or key) should be used. You have to change the whole system. Your bolt carrier velocity will increase...and your gas should be tuned for the ammunition you'll be shooting.
Adding an A5 will increase the distance it has to reciprocate... I'm not sure what the benefit there is (by adding the A5), in combination with the light BCG.
I'm building a 3 gun rifle and I want to get it as soft-shooting as possible within reason. I am using an adjustable gas block. Reciprocating distance stay the seems regardless of the buffer system, so that shouldn't be an issue.
What's your desired outcome with both the lightweight BCG and the A5 system?
With a light BCG/buffer, a heavier recoil spring, and adjustable gas block (or key) should be used. You have to change the whole system. Your bolt carrier velocity will increase...and your gas should be tuned for the ammunition you'll be shooting.
Adding an A5 will increase the distance it has to reciprocate... I'm not sure what the benefit there is (by adding the A5), in combination with the light BCG.
What's your desired outcome with both the lightweight BCG and the A5 system?
With a light BCG/buffer, a heavier recoil spring, and adjustable gas block (or key) should be used. You have to change the whole system. Your bolt carrier velocity will increase...and your gas should be tuned for the ammunition you'll be shooting.
Adding an A5 will increase the distance it has to reciprocate... I'm not sure what the benefit there is (by adding the A5), in combination with the light BCG.
The A5 will not increase the distance the system reciprocates. What it may do is increase the duration of time it takes for the BCG to complete its operations, that can be advantageous for many.
Light recoil due to a reduced reciprocating mass does not mean that the components play well with each other. In fact, much of the opposite is true. In a fun gun, it's just that, you can play with all of the race gun only stuff. In a gun that may see serious use, It's preferable to have that mass in a range that that allows the system to work better overall.
Tom, am I correct that if I reduce carrier mass, I should also decrease buffer mass to make up for it? Provided I'm tuning the gas system properly of course. My thought was that the 5.33oz A5H2 buffer might not work well with the LM carrier. The A5H0 is a bit lighter at 3.8oz, so maybe that would get it close to where it needs to be.
For a fun gun, go ahead and try it out. For a possible serious use gun, then no.
Yeah, definitely a fun gun. I have plenty of others for serious use. For now I'm going to run the BCM BCG with the standard A5 set-up. I'll try the LM carrier and lighter buffer later on when funds permit. I assembled most of the rifle yesterday and it came out great. I pick up my Razor HD 1-6 tomorrow. Then I just need a good brake and it's done.
For a fun gun, go ahead and try it out. For a possible serious use gun, then no.
I stand corrected, the longer buffer prevents that from happening (and the geometry of the rest of the rifle), but this still doesn't make sense to me...
My super light (all light weight reciprocating mass) increased in recoil, until I put a muzzle brake on it... Which is annoying, but effective.
Were you using an adjustable gas block by chance? I would think that just using lightweight reciprocating parts without reducing the gas would make for more violent operation in general and thus increase felt recoil.
I stand corrected, the longer buffer prevents that from happening (and the geometry of the rest of the rifle), but this still doesn't make sense to me...
My super light (all light weight reciprocating mass) increased in recoil, until I put a muzzle brake on it... Which is annoying, but effective.
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