Long stroke SureFire Carrier

[LRRPF52]

Makes sense since Sullivan led the engineering team that developed the Ultimax.

Jim Sullivan is one of the drafters from ArmaLite who worked with Bob Fremont on scaling the AR15 around a smaller cartridge, using the design of the AR10 as a basis.

They both would follow Stoner and scaled many of his designs from 7.62 NATO to 5.56, to include the AR16 to the AR18, and the Stoner 62 MWS to the Stoner 63.

Sullivan also assisted Ruger in the design work on the Mini-14, worked with Singapore on the Ultimax 100, and the Swiss and Italians on their joint 5.56 NATO service rifle, which eventually split into the Beretta SC70 and the Sig 550 series, since the Swiss and Italians couldn't get along.

He has worked on a number of rate reducers for the AR15, as he is a believer in the concept of walking fire, hip-fired full auto for suppression, and other bizarre infantry tactics that don't jive well at all with US doctrine for small arms employment. Stoner had the same ideas about service rifles/assault rifles, to basically have large capacity or belt-fed systems that masses of troops could walk with while they close distance onto the objective, spraying away like a scene from Predator.

They are design pioneers, but should probably stay away from ideas on tactics and weapons employment until being shown how things are actually done by seasoned shooters. There seems to be a major disconnect with some about the practicality of logistics, from the soldier's load back through the unit-level distribution, as well as large footprint of the Log Chain. Additionally, barrel metallurgy has yet to address the volume of fire Stoner and Sullivan envisioned.

Sullivan felt a number of years ago that we should approach the challenge of bore friction with projectile design, with driving bands, reducing wear, so the all Full Auto vision could be realized. I think a basic patrolling course would eliminate a lot of these ideas from the engineers, once they see what the capabilities and limitations are of a dismounted light infantry unit when it comes to ammunition carrying capacity.

[LRRPF52]

Interesting.
The way I see it, as the BCG in an AR moves rearward, there are 4 significant milestones. #1 the point where ejection occurs, #2 the point where failure to feed would happen if rearward movement stopped, #3 the point where failure to lock back would happen, and #4 the point where the reciprocating mass (BCG and buffer) hit the RE and stop, contributing to recoil.
This system gives more distance between #3 and #4, ensuring reliability while giving more time for the spring to slow down the reciprocating mass prior to #4. This should mean less recoil, I would guess. It probably shoots like a gun with the adjustable gas block turned down to the ragged edge while still being reliable.
I'm sure there is more to it but that seems pretty cool. It kind of reminds me of the ultimax 100 LMG, which is designed with a "constant recoil" where the reciprocating mass never hits the rear, it is always under spring power.

You missed one of the most important ones: Primary extraction

Increasing the time the bolt stays locked helps with this, as the less obturated the case is against the chamber walls, the better.

The Canadians have a totally different chamber design for the C8s vs the C7s for this reason, with .004" more diametric tolerance in the chamber walls with the CLGS C8, one of the reasons why their guns run so well.

[BufordTJustice]

Jim Sullivan is one of the drafters from ArmaLite who worked with Bob Fremont on scaling the AR15 around a smaller cartridge, using the design of the AR10 as a basis.

They both would follow Stoner and scaled many of his designs from 7.62 NATO to 5.56, to include the AR16 to the AR18, and the Stoner 62 MWS to the Stoner 63.

Sullivan also assisted Ruger in the design work on the Mini-14, worked with Singapore on the Ultimax 100, and the Swiss and Italians on their joint 5.56 NATO service rifle, which eventually split into the Beretta SC70 and the Sig 550 series, since the Swiss and Italians couldn't get along.

He has worked on a number of rate reducers for the AR15, as he is a believer in the concept of walking fire, hip-fired full auto for suppression, and other bizarre infantry tactics that don't jive well at all with US doctrine for small arms employment. Stoner had the same ideas about service rifles/assault rifles, to basically have large capacity or belt-fed systems that masses of troops could walk with while they close distance onto the objective, spraying away like a scene from Predator.

They are design pioneers, but should probably stay away from ideas on tactics and weapons employment until being shown how things are actually done by seasoned shooters. There seems to be a major disconnect with some about the practicality of logistics, from the soldier's load back through the unit-level distribution, as well as large footprint of the Log Chain. Additionally, barrel metallurgy has yet to address the volume of fire Stoner and Sullivan envisioned.

Sullivan felt a number of years ago that we should approach the challenge of bore friction with projectile design, with driving bands, reducing wear, so the all Full Auto vision could be realized. I think a basic patrolling course would eliminate a lot of these ideas from the engineers, once they see what the capabilities and limitations are of a dismounted light infantry unit when it comes to ammunition carrying capacity.

Well, barrel metallurgy has been addressed (stellite barrel liners), but cost and accuracy still lack.

[BufordTJustice]

You missed one of the most important ones: Primary extraction

Increasing the time the bolt stays locked helps with this, as the less obturated the case is against the chamber walls, the better.

The Canadians have a totally different chamber design for the C8s vs the C7s for this reason, with .004" more diametric tolerance in the chamber walls with the CLGS C8, one of the reasons why their guns run so well.

What can you comment on ref to the C8 bolt metallurgy and manufacturing processes? C158? Heat treated and shot peened?

[LRRPF52]

What can you comment on ref to the C8 bolt metallurgy and manufacturing processes? C158? Heat treated and shot peened?

They wouldn't divulge the alloy, but it is definitely shot peened.

For those that don't know what shot peening is, it isn't shooting the gun to peen the bolt with stress.

They literally tumble it with shot media to lightly impact-treat the surface of the steel in order to increase the surface density and strength. I think the process was developed in early industrialization with automobile parts IIRC.

Anyway, I'm quite confident that Diemaco/Colt Canada does not HPT with proof loads their bolts, and has very strict controls over their processes for heat treating.

I expressed the opinion that the AR15 bolt was too small for 5.56 pressures, to which this engineer declared was not the case, as long as you control the processes correctly.

The SCAR bolt is slightly larger to deal with 5.56 bolt thrust, and does very well for longevity. Looking at the volume that the US has to produce, controlling processes might be harder since we have millions of soldiers.

I know the C8 guns have a very high reputation for reliability and accuracy as well, above what the M4, M4A1, and SOPMOD Block II have by far when looking at bolt fatigue.

[pinzgauer]

They literally tumble it with shot media to lightly impact-treat the surface of the steel in order to increase the surface density and strength. I think the process was developed in early industrialization with automobile parts IIRC

It's normally much more than tumbling, think bead blasting on steroids. The steel beads are shot at high velocity from nozzles.

Essentially the equivilant of thousands of tiny ball peen hammers surface hardening the material.



Sent from my PRC-104 using phonetics

[elephantrider]

It's normally much more than tumbling, think bead blasting on steroids. The steel beads are shot at high velocity from nozzles.

Essentially the equivilant of thousands of tiny ball peen hammers surface hardening the material.



Sent from my PRC-104 using phonetics

That would make more sense than tumbling, as I can't see much peening, or surface hardening going on without some impact energy (velocity) taking place.

[sinlessorrow]

They wouldn't divulge the alloy, but it is definitely shot peened.
Anyway, I'm quite confident that Diemaco/Colt Canada does not HPT with proof loads their bolts, and has very strict controls over their processes for heat treating.

I expressed the opinion that the AR15 bolt was too small for 5.56 pressures, to which this engineer declared was not the case, as long as you control the processes correctly.

Fascinating tidbit there. I really wish HPT would die, I imagine the M4A1 would see a huge boost in bolt life by removing HPT. Was HPT done from the get go of the AR-15 or was it something request by the Army?

I believe it was said on this forum some time back that KAC sees a loss of like 33-40% in bolt life with HPT.

[elephantrider]

Fascinating tidbit there. I really wish HPT would die, I imagine the M4A1 would see a huge boost in bolt life by removing HPT. Was HPT done from the get go of the AR-15 or was it something request by the Army?

I believe it was said on this forum some time back that KAC sees a loss of like 33-40% in bolt life with HPT.

Just imagine the boost they would get by not using ammo loaded to 'Hiroshima' pressures, and, or using an extended/mid-length gas system.

[sinlessorrow]

Just imagine the boost they would get by not using ammo loaded to 'Hiroshima' pressures, and, or using an extended/mid-length gas system.

Part in red has been fixed. Chamber pressures are down to 54,200 PSI +/- 20PSI.
I'm also still not sold on mid length, the carbine system is slightly overgassed which does increase reliability in certain settings.