Light weight bolt carriers effect on felt recoil

[hkmp5ks]

For those who have actually experimented with reduced mass or light weight bolt carriers, how much difference in felt recoil is there from reducing the bolt carrier weight by 2 ounces? Can you actually tell the difference?

Assuming acceleration of 100m/s2, a 2 ounce mass will produce about .57 kilogram-force which sounds like it would be a discernible difference in felt recoil but without real world experience, it's hard to say.

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For context, I currently run a JP Ultra LMOS aluminum bolt carrier in a competition rifle with tuned gas system and JP captured recoil spring and am wondering what would happen, exclusively from a felt recoil perspective, if I go to a titanium bolt carrier that is 2oz heavier. I know I would have to re-tune the gas system and potentially the recoil spring. That's fine. Just wondering how much impact it would have on felt recoil from adding the 2 ounces.

 

[TonyTheTiger]

It's noticeable. In one rifle I went from aluminum carrier to skeletonized TI to full mass TI with gas adjustment each time. Going from memory, the AL carrier was 3.3ish OZ and the full mass TI was 5? OZ with the skeletonized one somewhere close to the AL weight. Doubles were slightly closer and sight picture in recoil just the tiniest bit more stable with the AL carrier. Recoil was definitely softer.
None of these things would affect my scores at any match though, it's just not that important. The AL carrier also died in under 4k rounds too. Might have been sub 3k, I'd have to look in my notes.

 

[hkmp5ks]

It's noticeable. In one rifle I went from aluminum carrier to skeletonized TI to full mass TI with gas adjustment each time. Going from memory, the AL carrier was 3.3ish OZ and the full mass TI was 5? OZ with the skeletonized one somewhere close to the AL weight. Doubles were slightly closer and sight picture in recoil just the tiniest bit more stable with the AL carrier. Recoil was definitely softer.
None of these things would affect my scores at any match though, it's just not that important. The AL carrier also died in under 4k rounds too. Might have been sub 3k, I'd have to look in my notes.

Which one did you end up keeping in your gun? That's exactly what I'm trying to decide... skeletonized TI is close to alum weight but eliminates the forward assist, which I prefer to have. Full mass TI is 2oz heavier than skeletonized TI. So I've been leaning towards full mass TI to retain the forward assist functionality, but wonder if the cost in recoil is worth it... leaning towards "yes" because these guns don't recoil that hard to begin with, even while shooting cardboard target arrays off hand at high speed in 3gun competitions.

 

[reelserious]

If you are looking for an AR for like 3 gun etc it is the way to go for sure. If you use a 3 or 4 port brake and a light weight BCG it will be amazing and shoots so flat you will love it. If you combine it with an adjustable gas block its even better. a 2 OZ difference can be felt

 

[TonyTheTiger]

Which one did you end up keeping in your gun?

The decision was more or less made for me. The AL carrier died at the Nordic Multigun and zeroed a stage for me. So never again. The TI Boomfab (the one I'm calling skeletonized) died in a mysterious malfunction that resembled a massively overcharged case, although my standard powder charge fills the case so that's not really possible..
It was also not the smoothest finish and was hogging out my upper receiver.
Around that time I just happened to pull 3 RCA full mass TI BCG's off prize tables and that's what my main guns are running now. I still have back up guns running steel JP LMOS carriers and I wouldn't feel handicapped using them even if I can tell there's a difference.

 

[srt-4_uk]

Dropping the SCS and going to a gutted buffer will negate some of the weight difference of going Ti. Or there's always a derlin buffer.
Imo, forward assist is pointless for a race gun. I wouldn't let that sway your decision.

 

[hkmp5ks]

Dropping the SCS and going to a gutted buffer will negate some of the weight difference of going Ti. Or there's always a derlin buffer.
Imo, forward assist is pointless for a race gun. I wouldn't let that sway your decision.

For the most part I agree but under certain situations I've used it when I do a press check after loading with a mag that felt weird seating or something like that. If the difference in felt recoil is minimal then I'd prefer to keep the FA function.

My main race gun is actually going to continue to run the JP Ultra LMOS aluminum BCG, I have a brand new spare as backup to the one I'm currently using. That JP aluminum carrier has the FA serrations, which is nice.

But I'm building another upper a bit more precision oriented and for that one I'm considering the TI carrier. Since I won't be shooting super fast with it, I think it'll be ok

 

[JS8588]

The decision was more or less made for me. The AL carrier died at the Nordic Multigun and zeroed a stage for me. So never again. The TI Boomfab (the one I'm calling skeletonized) died in a mysterious malfunction that resembled a massively overcharged case, although my standard powder charge fills the case so that's not really possible..
It was also not the smoothest finish and was hogging out my upper receiver.
Around that time I just happened to pull 3 RCA full mass TI BCG's off prize tables and that's what my main guns are running now. I still have back up guns running steel JP LMOS carriers and I wouldn't feel handicapped using them even if I can tell there's a difference.

How are those RCAs holding up? Nitride finished titanium has me curious from a durability standpoint.

 

[TonyTheTiger]

How are those RCAs holding up? Nitride finished titanium has me curious from a durability standpoint.

With my use of them being split up between 3 rifles I don't have a ton of rounds on a single one yet. I think about 4k on the primary unit and it looks brand new. I don't think it's normal nitride though, or if it is it's a much smoother nitride than anything else I have.

 

[iktomi]

I've built a few reciprocating systems around UL'd BCGs.

Typically, use them for precision-focused builds with rifle-length (or rifle+) gas systems and I have appreciated the results.

Keep in mind:

The reciprocating system needs to be considered as a whole, from buffer spring weight to buffer internals to the total mass of the BCG, in the context of the gas system (and suppressors)

Adequate bolt-lock-time is important for reliable extraction.

Bolt-lock-time is influenced by the forward pressure of the buffer spring, the inertia and the damping characteristics of the buffer and BCG, and gas-system length (longer gas systems delay initiation of the extraction cycle).

All other things being equal, dropping the BCG weight will reduce bolt-lock-time.

I've run some tuned 16" rifle-length guns unsuppressed with very consistent (hand-loaded) full-pressure m193(ish) 55gr loads with 5 oz BCGs without problems.

You could see extraction issues with over-gassed, shorter-gas systems, with lighter springs and buffers. Reducing the BCG mass might shorten bolt-lock-time enough to induce extraction problems.

 

[MontanaMan]

Whatever BCG / buffer / spring system you land on, add this & you'll likely get more recoil reduction from it than all the above.

MM

https://precisionarmament.com/hypertap-muzzle-brake/

 

[FALex]

Whatever BCG / buffer / spring system you land on, add this & you'll likely get more recoil reduction from it than all the above.

MM

https://precisionarmament.com/hypertap-muzzle-brake/

Those look like they'd work well, with one exception. The damn holes facing the bottom. Those always end up kicking up too much shit, in my experience. Then again, here in Idaho we have that moon dust shit. It has the consistency of talcum powder, so hitting it with a sudden burst of air really stirs shit up.

OP to answer your question, it has been my experience that an LMOS absolutely mitigates felt recoil. My JP LRP-07 has the LMOS and the SCS, and it's kind of ridiculous how it feels (or doesn't feel) in this instance.

 

[srt-4_uk]

There aren't ports on the bottom or top of that brake

 

[msgriff]

Those look like they'd work well, with one exception. The damn holes facing the bottom. Those always end up kicking up too much shit, in my experience. Then again, here in Idaho we have that moon dust shit. It has the consistency of talcum powder, so hitting it with a sudden burst of air really stirs shit up.

OP to answer your question, it has been my experience that an LMOS absolutely mitigates felt recoil. My JP LRP-07 has the LMOS and the SCS, and it's kind of ridiculous how it feels (or doesn't feel) in this instance.

The Hypertap doesn't come with drilled out ports, just pilot "dimples". You have to finish drilling the ports yourself in any configuration that you want.

 

[FALex]

The Hypertap doesn't come with drilled out ports, just pilot "dimples". You have to finish drilling the ports yourself in any configuration that you want.

10-4. I didn’t know that, just saw the pics from their website. Thank you for the edification.

 

[bfoosh006]

While I never jumped fully into Ltwt Ti BCG's , I did try a skeletonized Steel BCG, a light weight buffer setup from Taccom, and a 18" RLGS barrel w/ an Adj. GB., and a decent muzzle brake.

I was using 55gr PMC Bronze ammo since it was some of the lightest recoiling ammo I had.

For anyone curious, the recoil was noticeably "softer" it wasn't quite what I expected.

There wasn't as much sharp (?) recoil anymore. I could tell the cycling was different, GTG, but different.

Eventually, I got used to the differences... and that AR15 is still configured like above.

I am faster with it. So I got what I wanted.

 

[natdscott]

It's noticeable. In one rifle I went from aluminum carrier to skeletonized TI to full mass TI with gas adjustment each time. Going from memory, the AL carrier was 3.3ish OZ and the full mass TI was 5? OZ with the skeletonized one somewhere close to the AL weight. Doubles were slightly closer and sight picture in recoil just the tiniest bit more stable with the AL carrier. Recoil was definitely softer.
None of these things would affect my scores at any match though, it's just not that important. The AL carrier also died in under 4k rounds too. Might have been sub 3k, I'd have to look in my notes.

What was the mode of failure, Tony?

Any pictures?

 

[TonyTheTiger]

What was the mode of failure, Tony?

Any pictures?

The inside bore of the carrier wore out of spec, to the point that the gas rings barely touched anything. Replaced gas rings to be sure, but it was definitely hogged out.
Funny enough in the weeks leading up to the big match that it failed in, I had needed to turn the gas up a few times. Very unusual, and somehow it didn't seem like a giant red flag at the time.

 

[natdscott]

The inside bore of the carrier wore out of spec, to the point that the gas rings barely touched anything. Replaced gas rings to be sure, but it was definitely hogged out.
Funny enough in the weeks leading up to the big match that it failed in, I had needed to turn the gas up a few times. Very unusual, and somehow it didn't seem like a giant red flag at the time.

Yup. We get in a groove--sotospeak--and sometimes later, think differently about decisions a match schedule "helped" us make.

I wonder if they ceramic coated the bore (Rc over 70, at least 10 points harder than the rings) if that problem would be solved.

About as hard as the hard chrome bores, and harder than the hard-anodization otherwise used on aluminum.

 

[TonyTheTiger]

Yup. We get in a groove--sotospeak--and sometimes later, think differently about decisions a match schedule "helped" us make.

No doubt, I've made some very questionable decisions right before important events.
I wonder if JP does anything special with the bore of their AL carriers. I know a couple guys with over 6k on them.

 

[Ernest 5.56]

No doubt, I've made some very questionable decisions right before important events.
I wonder if JP does anything special with the bore of their AL carriers. I know a couple guys with over 6k on them.

Are they running jp bolts with the low friction gas rings?

 

[TonyTheTiger]

Are they running jp bolts with the low friction gas rings?

Good question, can't say that I know. One guy that I know was having erratic function in one of his, thought he said 7k rounds.
Everyone I've ever talked to about the one piece JP gas ring has tossed theirs in the trash though. I bought one and also tossed it.