SUB-SONIC Grendel loads

[Rapier]

For some reason I am not getting email notice on this thread for replies.

Ok, so if you got round holes at 1-8.75, I should get round holes at a 1-9. Now to push up to 1,100 fps. Damn it has been hot here 99 degrees at 90-100% with no wind. Makes you want to wait on this till fall.

Luckily I have three buffer weights and several springs. So if I get a load up to 1,100 and it is just short of function, I will just loose a little buffer weight and it should work OK, otherwise we start removing coils.

My can should be in in two weeks. Then we wait for the paperwork to be done.

By the by, I am working fast and slow at the same time plus Hornady and Winchester. Right now with a 16 I am at 2,600 fps with the Sierra 120 HP BT MK and .6 inches at 100. I am running a recut throat and setting the bullets at 80 not 60. Look at your mag and the follower's function carefully, the center is never touched, so the OAL to mag length is taken at the sides not center. This is important for the 160gr and capacity if you need it.

Piggies have gone for now but they will be back.
Ed

[txgunner00]

At the range 'bout to send some down.

[txgunner00]

Range report-

Fired some more loads using Unique. This time 7.4 grains gave me a 5 shot average of 1060 and an ES of 57. The atmospheric conditions were almost identical to the last time I shot them (99 deg and a DA of 4105) but they averaged 70 fps faster. Could be they were in my truck which set in the sun all day. If that's the case this powder is a little more sensitive to temp than I like it to be. Overall they did OK though. Holes were round and groups were good enough.

Now the US869... not so good. The first round I fired was a charge of 15 grains and it gave me 1204 fps. Apparently I stepped down too much because my next charge of 13 grains gave me a m.v. of 0 fps- it got stuck. I though I had blown my rifle up at first because the charging handle hit me in the nose an smoke came out every where. Fortunately nothing was damaged and I already got the projo out. It only lacked about an inch.

The 15 grain charge showed promise because it actually ejected but didn't lock back. With a can it might but I don't have one for this rifle yet. I might attempt this powder again but I will definitely not jump so far between charges.

[mtn_shooter]

Were those 140 or 160 grain bullets?

[Rapier]

Txgunner has been running 160s, I am at present running the 140s. I will try to run the 160s next with my 1-9 twist. So we are giving you guys an idea of what you may do with two different bullet weights.

Well we were both out at the same time. It was cool here, just 98 degrees. I had an interesting time though. I ran 7, 7.5 and 8 gr of Unique with the Hornady 140s out of the 16inch. The target was moved to 50 yards as noted previously, as that will be my normal planned shot range at night.

7gr velocity 924 fps, group 1.25 POA VS POI 1 inch low, no function
7.5gr velocity 1037 fps group 1.01 POA VS POI 1 inch low, no function
8gr velocity 1164 fps group 1.25 POA VS POI 1 inch low, no function

The 1164 load was definitely different as I could hear, even through my moulded plugs, the sonic crack VS the lower sound of the bang of the sub loads. Math works one more time, my calculated ceiling being 1116 fps looks to be firm. I will push up close to 1100 but just under to take care of fluctuations in loads.

None of the above rounds were loaded with toilet paper to keep the powder in place. I now intend to increase the 7.5 load to 7.7gr and insert a small square of toilet paper to hold the powder. I will also go to a lighter buffer in the recoil system and if that does not work, we cut coils. I can feel the bolt come back and then slam forward at each shot at this point in the process, but there is no ejection of the spent round. I do have some experience with suppressed systems modification and with my shorter system feel comfortable with the Unique powder's operation.

I also took my fast ammo with me and discovered a disconcerting item. I had to change to a new can/lot of powder and my load development must start again for top end. The new powder runs slower by about 50 fps. Remember this is a 16 inch and working a 120 above 2,550 is a bit tricky.

Now I did get one interesting piece of data by changing the sub sonic target to 50 yards. The POA VS POI is 1 inch low for the sub loads while the 2,550 fps 120gr load was 1/2 inch high at 100, without any scope change. So we appear to be very close to a convergence of aim points which could be very useful in a "need to switch" situation. If I increase the fast load a bit and lower the impact point in doing so, then go 1 inch high as a sight setting for the fast load, we should be very, very close to a same, same hold.
Ed


Hope this does not post twice.

[txgunner00]

I have US869 a nother try and it's a no-go. I got unburnt powder stuck to the shoulders of the cases which means it doesn't create enough pressure to expand the case. A duplex load might fix that problem but I don't want to go down that road. Looks like Unique is the powder form me.

[Rapier]

Got out this weekend, 100 degrees, and tried the 7.7 gr Unique load with the 140s which pushed up to 1088 fps for a high with a TP wad on top of the powder. The SD was around 30 fps. The groups at 50 dropped to .803 inches, at 1/2 inch low of POA. But I had some interference from the TP on one load as it only did 900 fps. So I will just use the Unique without TP.

I did not get function with a 3 oz buffer and the carbine spring. The carbine spring is 2 inches shorter than the rifle spring and the rifle buffer I am using is 6 oz. It might be that function can be obtained with a reduced mass bolt carrier by JP Enterprises which weighs in at 6.1 oz for $199. Now if one could find an old Smith Enterprises aluminum bolt carrier no doubt you could get the 3 oz carrier to work but they are out of production and sought after by the auto folks to make their AR do a 1500 rpm zip trip. I did find a titanium bolt and carrier that weigh 5.1 oz at $280.

I did do some checking and looking and finally found some data by JD Jones on the 300 Whisper and his suggestion to get function in an AR with that cartridge in a 16.5 inch barrel. This saved me a phone call to JD. JD indicated that only powders with a burn rate between AA #9 and 1680 should be used due to AR timing and showed in the data a 165gr 308 bullet with AA 2015 at 12.6 gr (1046 fps) and AA #9 at 8gr (1033 fps) a 168gr bullet with 2400 at 8.2 gr (1103 fps) the SD on the 2400 was 11 which seems exceptional for a sub sonic load. Of course there were the 200-250 gr bullets all over, etc., but those weights are of no interest in the Grendel. A 160 in a 6.5 should be quite comparable to the 165 in a 308 with the case capacity being very close.

I have all of the powders in the data by JD so will give them a whirl with the 140s. Next time.

I discovered that the bearing surface of the 120 and 140 is smaller than the 160 and that my barrel does not have a real tapered throat. In order to use the 160s I will have to recut the throat just for the 160s. I think for now I will stick to the 140s and if I have a problem, then I will see about switching my setup to the 160 throat.
Ed

[Rapier]

I had to go up to the farm to check for storm damage so took the Grendel with me, without the Crono or bench. I thought to just check some of the 160gr loads to see if my 1-9 would make round holes. Well the 7.5gr of unique load shot 1/2 inch with all round holes and by the sound was sub sonic. The 3 oz buffer did not function, just opened and closed with the bolt left out of battery.

I tried 8.3 gr of 2400 with the 160gr and the 3 oz buffer. It locked the bolt back on the mag follower! I just had one round loaded with an empty mag, never dreaming the case would eject 10-15 ft out and the bolt would lock back. Now the bad part, the bullet hit the targetat at 50 yards, full sideways. Very odd, 7.5 Unique is round and 8.3gr 2400 is flipping. So this will not work for me and may be a tad north of sub sonic, but worth a try in another twist gun if function is needed. So I note it here for you guys to work on.

Oh, my match trigger decided at that moment to go FUBAR and the stop, stopped everything. So I got to only shoot one round of the 2400 load and none of the #9, 2015 or 1680 loads. It took two minutes to fix when I got home to the allen wrenches, which of course I did not take.
Ed

[txgunner00]

Always something....

Good info. I'll check my powder stash to see what I have in that range.

Which 160s are you using?

[Rapier]

Hey TX,
I am using the 160 Hornady RN in the above data, set up like a very short round with an OAL of only 1.845 which I do not really like, but after I ran my throating reamer all the way to bottom and still could not set the bullets out I figure my bore is exactly .264 or just under. The bullets are .264 right at the ojive on that RN, in other words right at the tip.

So I started with the 7.5gr of unique load because I knew it would act like a wadcutter in a handgun, which is what it did without any suprises. Then went to 2400. But the data on 2400 that J, D. published for the Whisper indicates a very stable powder with standard deviations of 11 fps or so. If that is the case then walking a load to just under super sonic should be a snap, if you can get the bullet stable. It is either at 8.3 or between to perhaps 8.0 but it must be close at 8.3

I will try to get some figures this weekend. I am still waiting for my can's papers to come back from the ATF so this is all still prep work. Oh, my allen wrenches are now in a zip lock in the rifle's butt. This is why I stopped using trigger stops in matches almost 30 years ago. Oh, install it, lock it down it will never move, yap-a, yap-a, yap all the while saying to myself, horse feathers it will screw up.
Ed

[bwaites]

Might not have a fast enough twist to stabilize those heavier bullets at those velocities. Hmmm........

[txgunner00]

I'm using the same bullet- 160 hor. RN. So far all my holes have been round with a 1:8.75.

Checked the powder stash- unfortunately nothing in between Unique and X-terminator. I'll have to pick something up next week.

I have a 19.5" barrel with rifle length gas. Any idea if I should go on the faster or slower side of the AA#9 - AA1680 range to get it to cycle? If I can just get it close with out a can it should cycle with one.

[Rapier]

Here is some data from a few loads I tested with the 160 Hornady in my 16 inch gun and a re-test of the 140 Hornady with Unique without a toilet paper wad:

160 Hornady RN OAL 1.845, no wad, 16 inch barrel, carbine gas tube, 1-9 twist, all shots 50 yards with a 3 ounce buffer and full rifle stock recoil spring in a rifle stock. All are average of 3 shots.

Unique 7.5 gr 1035 fps No Function .50 inch group round holes
2400 8.3 gr 619 fps Partial function no round stripped, sideways, no group
#9 8.5 gr 825 fps SD 36 full function .50 inch group round holes
2015 13 gr 1191 fps SD 65 full function 1.00 inch group round holes
H 335 14 gr 1133 fps SD 62 full function .75 inch group round holes


140 Hornady with 7.7 gr Unique 1242 fps SD 34 still no function but round holes and a half inch group at 50 this makes no real sense to have a higher velocity than with the wad but it is what it is. This might have been some kind of malfunction but is the average of 3 shots.

Note that anything above 1116 fps for me is super sonic so I now must drop the higher loads down. The powders with the higher SD makes the process more difficult as to stay quiet I must drop below the deviation plus below 1116 fps.

I would think that the last three with the 160 would have a good possibility, however #9 with the lower standard deviation might well prove to be the deal for me while folks with a 1-8 twist might do well to try 2400. It appears to me that some of the loads are simply too unstable at their load density in the Grendel case but this is a first time out and better data may come as we go forward. Oh, I was shocked to see the 2400 load threw out the case and locked the bolt back at 619 fps it just did not strip a round, but moved it. The data on this was wild, so wild that I did not write down a SD as one round was 500. one 700 and one 600 for and average of 619. So it appears that this powder charge is below the needed density to develop a stable pressure for 2400 in the Grendel case. This is most probably why this is the only load where the bullets went sideways, the 1-9 twist is barely stabilizing the 160s. This should not be a hard fix. Oh, for those that have the experience, this could be like a low load of 4227 where the powder does not burn and when you increase the load just a bit, it comes on, should not be any danger but 2400 might just come on with a bit of gentle nudging plus give full function.
Ed

[burnsome]

i'm surprised Trail Boss doesnt work in the 6.5. i use about 9.8 gr of TB in my 308 suppressed bolt gun and its very consistant with MV's of around 1020-1030 fps pushing 180gr Hornady flat based bullets. the case gets filled about 3/4's full with 9.8 gr of powder, so no need for filler material in the case. have also used TB in my 35 Rem Marlin and 375 H&H bolt gun to have some super low-recoiling plinking rounds pushing heavy bullets (200gr and 225gr). if i had some 6.5 dies i'd load some up and give it a try but i'm new to the 6.5 and have only shot factory loaded ammo up to this point.

[bwaites]

Trail Boss will work, but it won't cycle the upper. That's what everyone wants to see and is working towards.