Subsonic tumbling bullets

[Jdubbs]

I have messed around quite a bit here lately with subs in 308. Verified without can on then tested more with the cam, no problems. Barrel is 18 inches, 1:10 twist. Powder is Trailboss and primers always CCI 250s. I have shot many different bullets 150, 165, 168, 170, 175, 180, 190, and 208gr. Never had a bullet tumble, must be luck for me finally.

Problem I saw today had 168gr 2nd bullets tumbling at 80yds. This is my first time shooting these particular bullets, but have shot many 165-168 bullets without issues, ever. OAL is 2.8 and forget my jump but didn’t go longer due to magpul aics mag length. Velocity avg 1035 with 10.5gr charge. Same charge I use for almost all loadings.

Any suggestions to get some stability anyone has done in the past? I can lengthen the oal but will single feed and that’s fine, I can shorten it as well. Just wanted to try to reduce wasted time if someone had a similar instance.

Also the bullets are 2nds, no visible issues, weight is all good as well as measurements. Nothing out of the norm. They do stabilize in my 300blk bolt gun but loaded .025-.030 off the lands since I have room in the mag.

 

[Titanium700]

Probably need a faster twist.

 

[Creedmoor]

The first question I would ask is, how were these bullets "Pulled"
Are these bullets still concentric when loaded?
When spinning down the bore?
Why are these loosing Yaw when the others are not?

Years ago I bought tons of pulled bullets from a WV de-miller that had been pulled a few different ways, some cans were simply collet pulled, some were push pulled with collets to break the and some had the cartridge neck split once or twice and the bullets and the bullets just fall out.

I have seen some of the bullets from being de-milled loose jackets when fired and go "POOF" out of the barrel. Along take a few baffles out, on a few cans over the years. A friend in MD had a pulled 30 cal AP bullet de-core and turned right and went through the barrel of a M60 he was shooting.

Now with that, we shoot a huge amount of pulled bullets in my family. But I will say, I go over each can of bullets before I load them.

 

[Jdubbs]

The first question I would ask is, how were these bullets "Pulled"
Are these bullets still concentric when loaded?
When spinning down the bore?
Why are these loosing Yaw when the others are not?

Years ago I bought tons of pulled bullets from a WV de-miller that had been pulled a few different ways, some cans were simply collet pulled, some were push pulled with collets to break the and some had the cartridge neck split once or twice and the bullets and the bullets just fall out.

I have seen some of the bullets from being de-milled loose jackets when fired and go "POOF" out of the barrel. Along take a few baffles out, on a few cans over the years. A friend in MD had a pulled 30 cal AP bullet de-core and turned right and went through the barrel of a M60 he was shooting.

Now with that, we shoot a huge amount of pulled bullets in my family. But I will say, I go over each can of bullets before I load them.

I ran through the weights, base to ogive, base to tip, and measured bearing surface. All checked out with those. Didn’t run on concentrity gauge but may check that out. Bullets don’t appear pulled, just marked factory 2nds. Appear to be either sst or amax with orangish tip instead of red, I’m going to grab a box of sst and amax and compare my measurements and see if I could narrow down something there. Same bullets in 300blk stabilize and stack moa subsonic with fast shotgun/pistol powder. I scratched my head all day after testing them in 300blk. 300blk is 1:8 twist so don’t think it’s the twist rate hurting the light bullet.

 

[Creedmoor]

I ran through the weights, base to ogive, base to tip, and measured bearing surface. All checked out with those. Didn’t run on concentrity gauge but may check that out. Bullets don’t appear pulled, just marked factory 2nds. Appear to be either sst or amax with orangish tip instead of red, I’m going to grab a box of sst and amax and compare my measurements and see if I could narrow down something there. Same bullets in 300blk stabilize and stack moa subsonic with fast shotgun/pistol powder. I scratched my head all day after testing them in 300blk. 300blk is 1:8 twist so don’t think it’s the twist rate hurting the light bullet.

I would weigh them also, on a analog scale if possible.
I also would be tempted to slice a few open long ways to see the average inside core.
With lighter (shorter) and heavier (longer) bullets not having a problem, I'm going to say its that bullet causing the problems. The unknown is Why are they Seconds?

 

[Jdubbs]

So I got some input privately on a possible issue from someone. Person was fine sharing the info, just didn’t want to comment on the post.

Comparing measurements the bullet appears to be 2nd amaxs. Measurements are dead on from what I was given. Apparently the angle of the boat tail is the culprit and makes them drastically different than my 168gr eldms and smk I have successfully used for subs previously. Bearing surface is also significantly different as well.

I retested this load and starting at about 10ft the bullet starts to tumble slightly. I started with targets at 5ft, then every 5ft out to about 40ft and it is pretty consistent and progressive.
I put an ELDM on the same target and not 1 slight bit of tumble.

So use for subsonic 308 is a no go for this bullet. Not sure if the short jump, faster twist, or shorter barrel allows them to stabilize for 300blk subs and not the 308. Only other difference is powder choice of using unique for 300blk and trailboss in 308. I may compare my red dot load for 308 subs and see if a different powder changes the stabilization or not. If not I’d agree on bullet design.

Figured I’d post this incase anyone else ever has this issue. Might not be the answer, but an idea.

Load 3 is 168gr ELDM load 2 is 168gr 2nd amax.

 

[Aszerigan]

The unknown is Why are they Seconds?

This is $64k question. Are they undersized? Why are they seconds?

I’ve shot a lot of pulled stuff too and never really had an issue. I don’t buy ‘seconds’ since the blem could be water spots (no big deal) or they could be incorrectly sized (big deal). Not taking that chance to save a few dollars.

 

[Jdubbs]

I’ve not had any issues with 2nds in supers or subs until this one. Weights all good across 200pcs. All measurements taken on about 20pcs plus the ones I tested all similar and fell in line with measurements given to me from someone with a 168gr amax out of the box. Not sure why they were culled 2nds minus 2 out of 200 missing tips.

My answer to myself is use for 300blk subs until I see anything abnormal, and don’t use for 308 subs. I haven’t tried any of these for supers yet, may try that some other time. Maybe the angle of the boat tail is 100% true, just being a light bullet and working in 300 but not 308 has puzzled me outside of different powders and barrel length/twist.