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+--- Thread: subsonic 170gn lee cruise missile (/showthread.php?tid=20435)
subsonic 170gn lee cruise missile - pashiner - 01-18-2020
Hi folks, I need some help with developing a subsonic cast bullet load for the grendel. I'm on a budget, so i'd like to avoid the hornady 160 RN, and preferably cast my own. I recently bought a lee 170gn gas checked "cruise missile" mold from midsouth shooter's supply. I'll be shooting these through a 24" 1:8 twist barrel that's cut with a grendel II parallel throat chamber and a .264 groove diameter from BCA. As is, this is a 1.5MOA gun with 123gn hornady commercial loads and my goofy ass pulling the trigger. I have a good supply of pure lead, wheel weights, tin, and hard magnum bird shot, so getting a sufficiently hard alloy should be no problem. I'll probably be using hornady brass, and the powders I currently have available are IMR3031, trail boss, and LILgun. I'd happily buy another powder if need be.
so far from a few weeks of deep diving the forums here, on the cast boolits site and a few others, my plans include casting the bullets in a 15-20 bhn alloy, annealing, sizing to .265, powder coating up a thou or two, and then size again while seating a gas check. Then I plan to heat-treat, and water quench to get my hardness back, as well as to further bond the Gas check to the shank by re-melting the powder coat under the gas check during the heat-treat. I intend to seat the bullets out to just touch the lands, which I realize may involve quite a bit of bullet shank intruding past the case neck into the powder space...hence the extra step to bond the gas check with re-melted powder coat.
My first load attempts will likely be a calculated 95% fill of trail boss, and then working down a few tenths at a time if I'm still supersonic, not to drop below 70% fill, per Hodgdon's dire warnings. I know there are probably much better powders for this application, but published load data for this bullet in the grendel case is non-existant. I've heard that some shotgun powders like unique, red dot, etc. are useful in this type of application, but I don't have Quick-load software, so it's all speculation to me.
Hopefully some of you guys can shed some light on any stupid mistakes in my plans. I'm not looking for pinpoint accuracy, 2MOA would do nicely out to 100 yards. These will be plinking and short range varmint loads, so reliable expansion isn't really high on my list. Furthermore, cycling the action isn't a huge priority to me. This is not a rifle intended for hunting or serious defensive use...just for funsies.
I also have found through my research on the cast boolits site that in a 1:8 twist swedish mauser barrel, this bullet seems to have a 1700fps velocity limit, but guys are using a ton of filler with fast rifle powders in a 6.5X55 case to get those speeds...however, any questions about those loads return a veritable raft of $hitposting and bickering. Seems to me that the smaller case capacity of the grendel would be a tidy solution to that problem, so as a secondary objective an action cycling moderate velocity supersonic load would be cool too, but that's not really why I got this mold.
Thanks in advance for any light you can shed on the situation!
subsonic 170gn lee cruise missile - tdbru - 01-18-2020
i'll give some OPINIONS based upon my years of CB rifle experimentation. 1. you're doing an awful lot of work on those CBs. cast them out of Lyman #2 up to Lino and water quench coming out of the mold. put a sponge in a bucket of water and drop the CBs onto the sponge. 2. use LBT soft blue. 3. Size to throat diameter. 4. try to not seat the base below the case neck. and this is an issue with the Grendel. i have a 6.5x55 and those guys were throated for a 156 gr. RN originally with not much bullet below the case neck. in my 6.5x55 i can seat, like 156gr. Norma Oryx so that the base of the bullet is just above the bottom of the case neck and they still fit in the magazine and chamber... AND EXTRACT just fine. imo trying to run a bullet that long in the Grendel is only going to frustrate you. although your quest for sub sonic i.e. low pressure, will give you more of a chance. look at night owl engineering molds for a ~120 - 130 gr. fb rn CB for this attempt. and if you get that, start with about 8 gr. of pistol powder (i use ww231 because it works for pistols too), chrono, and work, probably down from there. in fact they have a 6.5 grendel plain base 126 gr. mold. 266-126-FN-A03. you can also get it in gas check if you want to also experiment with higher velocities. but if you do intend to run subsonic, the plain base one will be fine. it has been designed to fit the Grendel throat & cartridge neck etc. you'll likely be a whole lot less frustrated in the end getting these to work. for the low pressures involved with subsonic shooting, you might consider just casting, lubing, loading and shooting. the powder coating and heat treating and all that, while fun to tinker with, is not required to get CBs to shoot well at subsonic speeds. look at the Grendel SAAMI chamber specs. get a throat cast or slug so you know exactly what the throat diameter of your Grendel is, size to that throat diameter. go have fun. of course with trailboss or a pistol or shotgun powder, reduce loaded enough to only go 950 to 1050 fps your AR will not cycle by itself. and by the way, the original twist rate for the 6.5x55 was 1 turn in 200mm which is ~ 1 turn in 7.87 " have fun!!
-tdbru
subsonic 170gn lee cruise missile - VASCAR2 - 01-18-2020
There are several good threads on doing subsonic ammo for the 6.5 Grendel. I suggest you use the google custom search on. Cast Subsonic
https://cse.google.com/cse?cx=016368947416500061353:paqd_0xcu1o&hl=en
I doubt you can get a trailboss load to cycle in a AR-15 but I never have tried to do subsonics. My suspicion is there wouldn’t be enough gas or pressure to cycle an AR-15. There is a video of a person shooting subsonic ammo through a suppressor with a 6.5 Grendel AR-15 and it functioned 100% in the second video.
https://www.youtube.com/watch?v=if0EgLcxTHw
https://www.youtube.com/watch?v=fqWQSnQ0mzI
subsonic 170gn lee cruise missile - Lemonaid - 01-18-2020
Pashiner, have you cast any bullets from the Lee mold yet? I ask as mine drops at diameter .271, and I am not the only one that has that problem.
I was thinking of milling down the mold to get a 140 grain bullet but that oversize mold problem won't go away.
At some point I will likely get the NOE mold that Von Gruff pioneered.
http://www.65grendel.com/forum/showthread.php?11017-Cast-Bullets-in-AR-Grendel&highlight=cast
http://noebulletmolds.com/NV/product_info.php?products_id=3640
NOE makes a 140 for the Creed that looks interesting as well.
http://noebulletmolds.com/NV/product_info.php?cPath=27_523&products_id=4700
subsonic 170gn lee cruise missile - pashiner - 01-18-2020
I cast a bunch, mic'd about 10 of them, and took an average. The alloy I used is about 50/50 clip on wheel weights and range scrap, mixed 2 parts alloy to 1 part magnum bird shot (it's the mix I have the most of, that I use for hardcast shotgun slugs and .45-70) and the base band is coming out at about .269.5 the next few are .269, and the band closest to the nose mics at .266. These dimensions were taken from bullets dropped straight from the mold into a water bucket lined with old towels. these bullets come out HARD! when you handle a pile of them, they ring like steel. I could mess with the alloy to go softer, but a 20 minute session in the oven softens them up nicely too.
I plan to get the 126 and 140 NOE molds this spring, but for now, I thought i'd monkey around with the el-cheapo Lee mold. I've heard of guys milling the 170 down to throw a plain base 152, or 140 grain bullet, but that'll be a future project if I can't get them to shoot full size.
i'll definitely try plain lubed too, but i've begun powder coating all the other projectiles I cast, so it's really no big deal to throw a couple handfuls of 6.5's in there when I'm doing a batch.
Thanks for the quick replies guys, keep those suggestions coming!
btw, Great suggestion about the chamber cast. I don't have any cerrosafe, but I'm considering casting a 170 from plain dead soft lead, greasing it up and hammering it into the throat from the chamber end. hopefully there's enough meat in the nose to slug up to fill the space!
subsonic 170gn lee cruise missile - Lemonaid - 01-18-2020
Please keep us updated (with pics!) of your results. I've heard horror stories about the Lee 170 not stabilizing for the 6.5x55. Also interested on how bullet sizing/seating/chambering go. Sounds like many fun days at the range
subsonic 170gn lee cruise missile - Klem - 01-19-2020
Pashiner,
I have not tried to subsonic a Grendel however will say from 300BLK experience that Trail Boss will not cycle your action with any bullet or load. Once you accept that then you may as well focus on the only reason for sticking with Trail Boss and subsonic...sound. The heavier the bullet the more pressure required to get it up to 1,000fps. That pressure follows the bullet out at the muzzle as sound. Lighter bullets equal less muzzle pressure which means less sound at the muzzle to tame. Obviously you are using a suppressor because otherwise what's the point of handicapping your your Grendel into a handgun.
300BLK shooters use about 6gn of TB behind the lightest 30cal bullet they can find to give the quietest sound possible. To cycle the action you will need more pressure which unfortunately means more sound. Specifically more pressure at the gas port. If you can commission a barrel with a pistol-length gas system it is going to be a lot easier to achieve cycling but it will become a dedicated sub upper unless you can tame it when shooting supersonics (with an adjustable gas system). Adding a suppressor contains the pressure for longer so that also helps cycling. H4198 and a heavy bullet cycles a 300BLK, but only if a suppressor is attached.
There's not a lot on the forum about this because it is hard work to sub a Grendel and still have it cycle an AR, with little to show for it compared to more suitable subsonic calibres, or the more useful power/velocity of a supersonic Grendel. According to Quickload a subsonic Grendel or Blackout, even with the heaviest bullets is still only 2/3 of the available peak SAAMI pressure. The Blackout is easier to sub because it has less case volume to fill to a safe load. Filling the case to at least 80% of the available space makes it safe. Whether it be 70% or 80% case fill is an arbitrary number and I've never seen 70% but you can also use fillers to push the powder back against the primer like synthetic sleeping bag filling (Dacron). Years ago we used to muck about with fillers for large cases like 223 and 308 until realizing with twist rates at the time and light weight bullets you could never stabilize a 223. Even with faster twist rates and heavier 80-90gn 223 it's probably still impossible.
Like with the 223 you want to make sure your bullet is stable with profile, weight and barrel twist. It should be OK in the Grendel and you can easily check using a site like JBM. I would still fire a few without your suppressor first to make sure they are not going through the target sideways, otherwise they will go through your expensive suppressor sideways.
Subsonic suppressed guns are good fun to shoot and have their place. Nothing beats the quiet of a .22 bolt gun or even a cycling AR Blackout. In hunting however it's just a handgun and no 6.5 rifle bullet is going to open up adequately on hitting flesh at less than 1,000fps. It will be like hunting with a bow.
I'm also interested in how you go so if you can keep us informed that will be great.