BigNate

I like it! Looking forward to seeing results!

Just whoring the thread a bit - but I think it's aligned... I heard (might have been here - not positive) that Aero Precision and Ballistic Advantage are now owned by the same company (one bought the other or someone bought them both) and that BCG stuff branded as BA is from Aero - and Aero branded barrels are now all BA. Can anyone confirm (or refute) this? Assuming that this IS true - I can tell you that the BA AR-10 BCG that I bought for my 8.6 project is functioning beautifully in my Aero M5 upper and that while it's still early in its life, its dealing well with the first bit of abuse that I've shown it... 🙂

Hi... I'm Nathan... and I have a gun building problem... I guess this is like asking the guys at the bar to talk me out of having another drink... 🙂 I'm in the middle of a 350 legend build... once that one is done I'll start looking at 45 Raptor... <sigh> LOL

Well - strike one... it sounds like despite the fact that the cartridge lists the .308 as the parent case - it is not generally formed from .308 due to the length of the case being longer than the distance of the .308 from base to the shoulder by more than 2 10ths... It sounds like folks have used 30-06 brass cutting below the shoulder - or 460S&W mag by trimming the base. Not a deal breaker - but it takes away one major "plus" for me...

I just ran into 45 Raptor in a discussion around the 8.6 BLK. I don't see it as a competitor with the 8.6 BLK as I'm looking at the 8.6 as essentially a cartridge that I'm going to use exclusively for subsonic purposes - and the 45 Raptor reads more like an AR-10 cartridge that would be loaded up to behave a lot more like 45-70 (i.e. one of the reference loads is 325gr @ 2150 FPS...). That gives me tingles in all kinds of fun places, and combined with the fact that I have thousands of pieces of 308/7.62X51 brass just waiting to be cut down and resized - it has me thinking that once I finish the current project (350 Legend SBR) I need to build one... Am I wrong?

OK - so what is the parent case? .338 Lapua?

I had been digging around on the Sprinco site and had read the details on their springs - but I'm missing details... I see "White" is standard, "Yellow" is "approximately 20% lighter than the White spring..." Blue is "15% greater than white... " etc. I'm a math nerd - and I was trying to do some math based analysis of how much energy I was absorbing so that I could do some regression modeling and try to better predict what I need in a given situation. This is mostly an academic exercise for me... I'm working as it sits - but would love to be able to compare spring rates etc across product lines. Am I missing "number" on their site somehow? The heavybuffers site looks awesome! Thanks.

Thanks much... good info there... I think I'm probably going to build a tester and start building my own dataset... we'll see... 🙂

OK - I've been digging on the interwebs and have come up dry. I may decide to make a project out of this - if it doesn't yet exist. Is anyone aware of a forum / website / etc. that contains actual data about buffer springs? I'm thinking things like: Length Number of coils Wire diameter Wire type Spring rate in lb/in Coil bind height Maybe I'm just a math / details nerd - but it would seem much easier to adjust if there were more specific data available. E.G. If my Sprinco red spring has a spring rate of 2.7 lbs / inch - and I'm looking for a nominally softer spring - knowing which, of the same length / bind height had a spring rate of 2.5 lb/in would be a handy bit of information. Am I nuts?

When I grow up - I want to be this guy...

OK - new chrono data (and a new chrono - picked up a Garmin Xero - I'm like a kid in the candy store with that thing...)... The ladder for the 300gr HPBT blems Cartridge 8.6 Blackout Bullet Nosler338 300gr HPBT Custom Comp Powder Accurate 1680 Case Hornady 6.5 CM Reshaped to 8.6 Case Len 1.682" COAL 2.750" Reloader Dillon RL550B Dies Lee Pacesetter FLSD, Seating, Crimp - Dillon Powder Notes Resized, then hand primed, then loaded on the progressive starting with powder fill Grains Average SD ES Count 16.0 967.1 19.9 62.3 10 15.7 961.7 10.0 31.9 8 15.4 948.2 12.1 38.2 10 15.1 940.0 18.3 63.6 10 14.9 918.8 16.5 57.0 10 The two missing rounds at 15.7gr of powder were failure to fire... of the 50 total in the ladder these were the only two malfunctions and I'm pretty sure that they were my fault - the primers were seated too shallow on these - had a good dimple but no bang... Other than those two - the gun functioned nicely. And the data for a few of the 250gr HPBT blems Cartridge 8.6 Blackout Bullet Midway Blem 250gr HPBT (understood to be SMK 2nds) Powder Accurate 1680 Case Hornady 6.5 CM Reshaped to 8.6 Case Len 1.682" COAL 2.750" Reloader Dillon RL550B Dies Lee Pacesetter FLSD, Seating, Crimp - Dillon Powder Notes Resized, then hand primed, then loaded on the progressive starting with powder fill Grains Average SD ES Count 15.6 1007.8 18.2 74.0 23 The 250s were being shot against the H3 buffer and sprinco red spring. In the 24 shots (I removed one outlier from the group - 823 fps) I had 4 malfunctions - failures to fully eject - that chewed up the brass - so I decided to stop shooting it... I'll try again when the silencer comes in - or will throw the standard carbine spring and buffer in the thing to burn up the rest of those rounds. On the 250s, I may try to reset the seating die and push the bullet deeper into the case - to see if this helps build a bit more pressure...

OK - some load data and an interesting finding... I picked up a bunch of 300gr Nosler CC HPBT blems and built a bunch more sub rounds. I saw some shared load data for these bullets that looked very much like the load that I had worked up for the 250s so I made a few with the 300s (figured they were subs and WAY below peak pressure so I was not worried about pressure spike - and the shared load info that I had seen used .2gr less of the same powder). So - anyway - both sets were: Accurate 1680 - 15.6gr CCI #200 primer 1.685" case length (re-formed Hornady 6.5cm brass) 2.750 COAL (the 300s were .6633 in the case - the 250s were .5216 in the case) No crimp - there is plenty of neck tension - when I tear these down with the kinetic hammer thing it takes a few really good whacks to unseat the bullet... I'll probably soft crimp the next set. It was a family shoot day and there were some new shooters who needed attention - so I only chrono'd a few of each. Interestingly the heavy bullets, on the same charge, gave essentially the same velocity (the range was 973 - 1004 FPS). I'll get better data next time out when there are not as many folks to manage. The other big discovery is that these functioned nicely with the H3 buffer and Sprinco red spring. If memory serves the Gorilla 285gr subsonic rounds clocked on Tom's Magneto Speed at like 860FPS. I'm thinking that those loads are VERY light / soft. I'm guessing that I got the same velocity out of the same charge under the heavier bullets because the deeper seat, greater release friction, and heavier bullet gave the powder a bit more time to build pressure and gave a bit more complete burn (guessing... if anyone knows of a place where folks nerd out on internal ballistics math, chemistry, and physics - let me know - trying to dive in a bit on that stuff). I suspect that a bit of crimp will contribute to that as well. Hopefully next time I'll be able to get better chrono data and collect group data as well.

250gr subs 250gr SMK (2nds from Midway) 15.8, 16.6, 15.4, 15.2, 15.0, and 14.8 gr of Accurate 1680 through a friend’s Hybrid 46. Totally hearing safe… and functions well (this is with the standard carbine spring and buffer). Without the suppressor, the gun ran well from 16.6gr > 15.0gr - but started to fail to fully eject at 14.8gr. Reformed Hornady 6.5cm brass, CCI #200 primers, 2.750 COAL…

I have a wedding on Saturday - but I think Sunday is free…. I’ll ping on Saturday afternoon to confirm…

Also - stumbled on this picture of the 350 maker bullets outside of the case and with a ruler for scale... thought the thread needed a copy...

OK - a few evolutions since the last post... SilencerCo ASR Break arrived yesterday... Omega 36M is in jail... ( a buddy has a Hybrid 46 with the ASR QD - once I know that the bullets hold together we're going to give it a test...) A couple of extra springs are in the range bag and an adjustable "light" carbine buffer. The first ladder of possible "cheap" subsonic reloads are in a box - waiting for a free evening to see if they'll cycle (recorded here for posterity - in case some poor bastard is going down the same road) 250gr HPBT (Midway USA "factory 2nd" bullets - supposedly SMKs) 16.6gr - 14.8gr of AA1680 (in 10 steps - with 0.2gr increments) which GRT tells me should give me 1103 - 1022 FPS - and . Not worried about blowing myself up - the model says that peak pressure on the "heavy" load should be 13415 PSI - and on the light end just over 10K - but I'm very worried about whether there is enough gas to cycle properly. Converted Hornady 6.5CM brass CCI 200 primers 1.685" case length 2.750" COAL Already planning to swap in an 8" barrel - "soon..." I'm debating whether to pull the brake off of the gun when I put the first few rounds through it. At 1000 FPS the bullet will be spinning just a bit faster than it would be at 2900 FPS out of a 1:10 .338 Lapua... (240K vs 232K)... I doubt that they will have an issue... but it would suck to have one come apart going through the brand new brake.. but I'm lazy... but it would really suck to damage the brake... but I'm "pretty sure..." LOL

Looking forward to it...

Not to mention that the other fella may not take kindly to having his pecker borrowed... 😛

I need to stop reading this thread... my wallet is already angry at me after the 8.6 build (and suppressor and dies and bullets and powder and...) and now I hear the faint call of a .300 Norma build whispering, telling me that I need to start bringing it into existence... 😛

During Desert Storm I remember hearing stories about Bradley kills on T-72s... not necessarily penetrating main armor - but doing just about what was seen there... flanking, swarming, disabling and then picking at them once disabled. I had always wondered how much truth there was in that. Really cool to see video that lines up with that... Years later, talking to an old friend of the family who was an Army field grade officer (I believe he retired as a Colonel) and had spent some time in a war planning capacity, and he implied that the armor encounters between the Abrams and Soviet armor were important, but somewhat validated what I had heard in theater, and noted that the Bradley v T-72 stuff had a fairly profound impact on the Soviet war planning in that they had long assumed that if a conventional war broke out they'd simply roll over Eastern Europe taking advantage of their massive numeric advantages in armor... and the fact that the Bradley had so much success against their MBTs was crushing to that strategy.

All this talk of "expensive" .30 cal and .338 stuff... makes me chuckle as I think about the relative meaning of the word "expensive" while thinking back on daydreams about "someday" building a.375 or .408 CheyTac. Of course, this is just about the same as daydreaming about buying a Top Fuel dragster (if you don't know - look up "first top fuel experience" on youtube) because I drag-raced my 350HP 14 second Nova when I was a teenager and I'm working on a project car that I expect will be a 750HP 10 second street car... 🙂

I've been watching the Johnny Reloads videos and had recently watched his .300WM series. He was shooting the 220gr SMKs and the 240gr SMKs through a 1:10 twist barrel. He noted the 1:9 warning on the 240s but found a bunch of info indicating that they actually stabilize nicely out of 1:10. He tests them through his gun / with his suppressor. Agreed - that a baffle strike is a bad thing... but maybe you put a few through it without the suppressor and ensure that you don't have issues? Just food for thought...

That's AWESOME! Wish I had been there!

Thanks gents...

Thanks much... that helps...