Range Report New sub load key holes at 100yd

M

mlw332

Sergeant
Full Member
Minuteman
Aug 17, 2011
157
0
37
Mississippi
#1
Load
308, 168gr smk, lapua brass, fed 210 primers, 8.0 gr clays, 2.8" oal

Rifle
308 built by mark gordon. 24" barrel 1-10" twist.

I went with hodgons load to attempt a few subs... started out at 25 yd without suppressor and was getting nice round holes on paper and decent grouping for my first attempt at a sub load. took it out to 100yd after getting the scope back on target for the distance. put on the suppressor and shot 3 3 round groups. all groups were 1-1.5" BUT they were all slightly yawing when hitting the paper....

any insight on what the hell is going on would be great. i thought since they were flying true at 25yd i would be fine. (there will not be another sub put through my can until this is resolved!!!!)

Thanks
Mike
 
#2
Good that they're a clean hole at 25yds - that means you're not going to get a baffle strike. What speed are you getting with that load? You might want to up the charge weight slightly to increase speed and stability a bit more.

Shake a loaded cartridge. Do you hear the powder shuffling around inside the case? An air void in the case will cause erratic ignition which is why trailboss tends to be a better powder for this. It's like fluffly little donuts and takes up the voided case volume when you seat the bullets for sub loads.

Subsonic loads are very unstable the slightest touch on anything can start an erratic tumble especially 100yds and out.
 
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#3
i did not have access to a chrono when i tested them... for what its worth the book says about 1080fps.
is there anything i need to look at to possibly help them stay stable? i have 150, 168, 175,190 if the weight will help...
sorry just my first rodeo with subs
 
#4
loading subs without a chrono can be iffy at best. You want to make sure you're supersonic first and work your way down very slowly. A few tenths of a grain can make a difference. Again how much air is in the case with those loads? Shake a loaded cartridge if you hear much shuffling of powder, you're going to have consistency issues. Trailboss will fix this. Check the edit on my prev post.

Also 1080 while subsonic is not good during very cold weather as the temp affects where the speed of sound begins. 1050 is still a bit too fast IMO. During the summer it's fine, but when the temps get cold it can make a difference.
 
#5
there is a good bit of air in the case as it had me worried to begin with but was going to try it since thats the published load... at least for a starting point. i will grab a jug of trailboss tomorrow and try a few thanks
 
#6
mlw332 said:
there is a good bit of air in the case as it had me worried to begin with but was going to try it since thats the published load... at least for a starting point. i will grab a jug of trailboss tomorrow and try a few thanks
Click to expand...


It will be almost impossible to avoid a lot of "air" in a case designed to hold 40+ grains and only loaded with 8-10 grains of any powder.

On top of that, a 168 grain bullet is very light for sub loads as it loses velocity much quicker than the heavies...a popular bullet is the 220 SMK but then you run into the potential problem of not enough twist to stabilize right out of the barrel and potential baffle strikes. Go for the heaviest bullet your barrel will stabilize...

The 308 cartridge is not ideally suited for subsonic use where the 300 Whisper/Blackout is perfect...
 
#7
Incorrect on almost impossible, trailboss will fix the issue as it is a light an fluffy donut shaped powder. I do agree that a 175gr or heavier bullet is a better option for subs in a standard .308 case. Take a look at a 4lb jug sometime, it's larger than an 8lb keg of standard rifle powder. However you will be closer to 10 gr of trailboss.

You are correct on the more efficient case of .300 blk or Fireball.

When working up new loads keep the suppressor off until you're sure the projectile is stable.
 
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#8
i've worked up a few loads on my 308 and although not the best round it sure is stupid fun..

I've mostly used the 170 flat nose 30/30 with 10.5gr of Trailboss and that was one of the most stable rounds I've found.
the 175smk is great but doesn't have the consistency of the 170 flat nose. My rifle is a 1-10 22" barrel, with the 175smk I was getting 2-2.5" at best at 100yds, With the 170 flat nose I can maintain 1.5" in mild winds

I wouldn't say the 308 is a bad caliber to use for subsonic but it varies on the average twist that most people have. While most of my rifles are 1-10 or 1-11.25 this isn't ideal for a heavier bull stabilization. I have a friend that is using a 338 spectre and that round is in my opinion a subsonic powerhouse.
 
#9
SMK's suck for subs, and will go end over end at 150 yds+(at least for me).
Semi pointed, is best w/ rd nose next, and flat nose last. If you want to use a SMK turn it backwards as it will fly better.
I use a home cast 180 gr in both a .308 12 twist and 300wm 11.27 twist and either will do the deed at 350+ yds.
Nice thing is they both are leaving at the same speed so there is only one set of numbers to remember.
 
#10
#11
I had a couple 1 in 7 twist 300 BLK barrels that wouldn't reliably stabilize ANYTHING. 208 Amaxs were the most stable, but even then the bullet holes were not perfectly round at 10 feet or 100 yards. The worst bullets were 150 grain Nosler ballistic tips, they hit almost sideways at 100 yards. 220 Sierra Pro-hunters (round nose) would shoot about 1 MOA but left oblong holes.

I replaced them with another barrel that did the same thing, at which point I gave up on subsonics entirely. My current 9" 300 BLK barrel stabilizes the 208 Amax's but I still worry that the odd bullet may be just unstable enough to cause a baffle strike.

Realistically, subsonics are fun for shooting at the range, or possibly for close range varmint control where noise would bother the neighbors, but not much good for hunting, for a variety of reasons.
 
#13
ddavis said:
Realistically, subsonics are fun for shooting at the range, or possibly for close range varmint control where noise would bother the neighbors, but not much good for hunting, for a variety of reasons.
Click to expand...
Come enter one of our subsonic match's, and find out what a sub is capable of in proper hands before you say that again.
(No spectators allowed, and you must meet certain quals to enter).
 
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#14
I have hunted with them and developed dozens of loads with them using dozens of different bullets in my 300 BLK. I am well aware of what they are capable of. My problem with them is that those pesky critters are always moving, and ranging a deer at 180 yards that moves to 150 yards before the shot means that you have just wounded or missed said deer.

Subsonics are accurate and a 30 caliber bullet kills just fine even without expanding, but I'm not going to limit myself to using them while hunting when there are better options.
 
#16
The matchkings do not work well (for me) subsonic. I have tried 200 and 190s in my 11.25 Twist 18" BBL. They didnt go well forward, and tumbled seemingly immediately loaded backwards. I only tried this because I have been unable to find the bullet for my normal sub load (180 Round nose). With the 180 RN and 10.5 Trailboss I am getting about 1030FPS and can make consistent hits on an IDPA (Man Sized) steel target at 300. Look into getting something round nose like others have said such as 30-30 bullets.
 
#17
ddavis said:
I have hunted with them and developed dozens of loads with them using dozens of different bullets in my 300 BLK. I am well aware of what they are capable of. My problem with them is that those pesky critters are always moving, and ranging a deer at 180 yards that moves to 150 yards before the shot means that you have just wounded or missed said deer.

Subsonics are accurate and a 30 caliber bullet kills just fine even without expanding, but I'm not going to limit myself to using them while hunting when there are better options.
Click to expand...

Why would you use a sub load on a deer at those distances? 30 cal subs are quite capable of doing the job but not reliably at those distances. I limit my sub use on game to below 100yds as I do most of it at night with lasers anyhow but the results are very good.
 
#18
I'm not going to get in the middle of any back and forth here with agree/disagree about bullets.

Here's what I know about subsonic development both as an avid reloader that has developed subs for all sorts of ammo (and I find the 308 to be pretty simple compared to others like the 50MG), and as an engineer with a background in external ballistics.

The 10tw is plenty to stabilize the 165class 30c bullets when they're conventional construction (lead core, cupronickel jacket type). For a 308 with Trailboss try starting around 11.5gr and work down in 0.2gr increments.

It sounds like you're on the very edge of instability and it's the slow arm of the epicyclic motion equation that is falling outside the equilibrium curve. This is overall not that important for what you're looking to do, but it does mean that you have ample twist rate, just bring the speed up a little bit.

If you load 11.5gr in there and shoot them with the suppressor you're going to hear a very audible crack, as you step down you'll find the loads will not sound quieter but all of the sudden they will go "silent" and it is fully obvious to anyone around you that it's a subsonic bullet. This is where you tune your load.

You aren't getting baffle strikes since you're getting round holes at 25yd and you could just start working up from your current point and see where they stabilize out.

You are right to be cautious and conservative about the keyholing, but with what you currently have I feel confident that you are going to be fine as long as you work UP from where you are currently. You can alternatively work DOWN from 11.5gr (as I suggested above) and this is what I generally advise to do (without the suppressor on) for new sub loads. Since you already have a low data point you're OK to work up from that position with the suppressor on there.

My lightweight 308 subsonic load is 9.5gr TB in Federal brass under a PRVI 150gr PPSP flat base bullet. It runs 980fps, super quiet, very stable from a factory 12tw and all sorts of accurate from my Brux 8.5tw that shoots the heavies too.
 
#19
Ok so the hold up now will be finding TB ... the local store sold the entire shipment in a few days. What is the overall perspective of staying with Clays for now to work up this load? will it leave to much free space in the brass and cause weird ignitions or anything of that nature? if you guys say wait on TB then im good with that... i also came across an old box of 30-30 projectiles. 150gr flat base round nose I will be trying.
 
#20
I have not used Clays because I have a couple 9oz containers of TB on the shelf, but a friend of mine shoots a lot of subs using Clays only. He swears by it and gets excellent results and groups at 200yd.

Those 150RNFP 30-30 bullets should have absolutely no trouble whatsoever.

If you keep getting a lot of vertical on them you can try a very mild taper crimp on the mouth as that will help boost the shot-start pressure for the bullet going down the bore and it can assist with micro-charge loads and consistency.
 
#21
You can use Clays, Red dot, Bullseye ect, but I prefer 700X. When using a fast pistol powder if you do not want to open the flash hole for dedicated sub use, a Magnum primer will help. Many folks got away from TB long ago, it is more forgiving than some other powders though.
Just remember case prep is more important with subs vs full loads if you want one hole groups, and the ability to make first rd hits at the new "long". Subs will make you a better reader of mother if you stick with them very long.
We have many guys who swear subs taught them more about mother reading than all their high speed stuff ever did.
 
#22
I use 7.5gr of Titegroup with a Lyman 311284 220gr cast bullet that runs around 1075fps - gives me MOA or better at 100m - costs less than 10 cents per shot. Use a std. primer - either Win or CCI.

Titegroup is not case position sensitive in my experience and gives very consistent velocities.
 
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