YHM 7.62 TI QD Phantom Accuracy Issues

[1slow01Z71]

The first three shots stack in pretty good but the 4th and 5th drop down about 3/4". Im not firing very rapidly, this is a 308 5R 24", just single feeding it so every 10-15 seconds a shot. For a while I was having issues with accuracy period with the can on but figured out the tooth on the mount wasn't seating into the can.
Can fully tightened down on the mount, notice its not seated in a tooth

So I have to back it off the the previous tooth otherwise my groups open up to 2"+

Here is a representative picture of a 5 shot group

Another, ignore the upper shot, was testing POI shift

Id think it was just an issue with the can not timing correctly on the mount if it weren't for the fact that the first three shots are pretty dang good. I do have a couple of flashiders that seat right but haven't swapped one on yet to try. This same can on my 20" AR gets me 10 shot groups shot in a minute like this

So Im not really sure whats going on. My griffin armament recce 7, phs338, and specwar 7.62 will be released next month so Ill have other choices to use soon but I plan to give this can to my dad and would like to have it lined out for him. Out of the four mounts I have only have two that actually time right with the last notch where the qd ring is fully compressed as well. I get an ever so slightly bit of movement on the two that don't seat all the way but again if this was really an issue Id think the first three shots wouldn't be stacked in as well as they are. Granted this isn't a precision bolt gun just a stock 5R with a trigger, it still annoys me. I do not get this group dispersion with the can off and only using the brake.

[Dr.K]

Some combos work better, some worse, some can't tell.

Nature of the beast.

My guess is that it could be some kind of barrel harmonic issue?? Pure speculation.

maybe the thread on cans will work better. I've read that for accuracy, strait thread on works best.

Also, I tend to not put much stock into a group less than 10 shots. BTW, I'd be happy with that grouping! It'd kill anything I shoot at!

[1slow01Z71]

The second group picture I posted is an 8 shot group, after 5 were stacking in next to each other down low in a row I didn't see any point in wasting more ammo. While the first group is still sub moa, it could be better, especially when Im trying to shoot nice groups. For hunting purposes yes it is nice but that's also only at 100 yards. Id hate to think of what that will do to my groups when I start stretching it out.

[continuity]

It's been my experience that some of these types of things fall in the realm of pure unadulterated magic. Sometimes the magic can't be made to work in specific cases.

Understand that my input has no value relative fixing things, but such combinations are sometimes simply akin to making a water and oil emulsification, remain so.

[bani]

try different ammo. plonking a big weight off the end of your barrel changes harmonics.

[1slow01Z71]

If it was an ammo issue it wouldnt group at all. It quite clearly groups just fine for the first three then drops 3/4" but still groups well.

[Wahnsinn]

If it were me, I'd say it's just my bad shooting

That's pretty weird though that it would group 3, then drop and group again. Did you check to make sure the teeth didn't slip and the can rotated a click or something? Scope rings are all tight? Scope mount is tight? Can mount is tight on the muzzle?

[1slow01Z71]

If there was an optics or shooter problem then it wouldn't shoot so well without the can. The muzzle brake is tight and by design the can cant jump a tooth once its seated into one.

[Dr.K]

Perhaps the can is causing the barrel to heat up in a different way than it does without, and by the third shot, things are expanding slightly caddywonkered due to the weight of the can?

Maybe let it cool completely between shots to test the theory.

"My next best guess"

[1slow01Z71]

It has something to do with heat for sure. I always try to shoot 5 shot groups as it gives me a better idea of what Im screwing up on that particular day while shooting. After I shoot a 5 shot group if I wait 5ish minutes then the first 3 stacks in good again then drops. Same results over and over again. In the second picture of groups you can see what happens if I keep shooting. The additional shots after #3 stay low but group well. My 178 amaxs are suppose to ship on the 14th so hopefully Ill be able to revisit this and figure out what is going on once I get more components in hand.

[bani]

If it was an ammo issue it wouldnt group at all. It quite clearly groups just fine for the first three then drops 3/4" but still groups well.

i don't see enough groups there to draw any statistical conclusion.

[1slow01Z71]

I did not take pictures of the same type of groups repeated over and over. Never mind the fact that if it was the ammo it would not group for the first 3 shots like it does. My SDs are in the single digits to very low teens, again its not the ammo. Why is that hard to understand?

[Veritas]

I did not take pictures of the same type of groups repeated over and over. Never mind the fact that if it was the ammo it would not group for the first 3 shots like it does. My SDs are in the single digits to very low teens, again its not the ammo. Why is that hard to understand?

Because there are many variables outside of just the suppressor...

As others have said and if you are as good a shot as you say and the ammo is as accurate as you say then the two options left are most likely heat or harmonics, there are 100's of reasons we could all think of...Unless you place this rifle in a jig or rifle rest that takes the human element out of the equation you will not know for certain.

[1slow01Z71]

The human element is taken out of it when itll shoot sub half moa groups with the can off. Basically shot 4 and 5 stay right in there with the first 3 unless I screw up. So that narrows it down to something with the system when the can is on. Its simple reasoning guys, I don't know why yall are making this more difficult than it has to be. There is an issue with the can/mount causing this. Im a decent shot, no expert by any means but 100yd groups isn't rocket science when shot with a good gun, with a good load and a steady rest. My muzzle velocities are taken with a magnetospeed V2 with the can on. With basically an average SD of 10 for this load, it would not cause this vertical spread, especially at only 100yds besides the fact that the vertical stringing does not happen with the can off.

With a TBAC 30p-1 it does not do this, its only with this can and mount. I was digging around in my bullet stash and found some midwayusa 178 amax seconds that I had forgotten about that Ill load up and test out Saturday with the extra flash hider Ive got. Only caveat to that is I don't know for sure how accurate the seconds are as Ive never shot 178 seconds, SMK seconds are pretty good but the 125gr SSTs I shot out of my blackout were less than stellar. Ogives all over the place, messed up tips and wild weight variations.

Pretty much I posted this thread in hopes that there may be a known issue I hadn't seen. Like with the 51T system being able to relieve the shoulder on the mount for the can to jump another tooth. It seems that is not the case and I have a unicorn or Ive reached the limit of the inherent accuracy of this particular can. Ill continue to tinker with it until my other cans are released.

[bani]

without pictures of the groups, it's pure speculation. the plural of anecdote is not data.

[1slow01Z71]

I appreciate your very helpful input. Maybe when you have something actually useful to post you can try it again. Im not new to shooting and when I say it does something every time I dont know why I have to post multiple pictures of the same thing. Maybe its because you dont know what youre talking about to begin withand for some unknown reason feel the need to post,I dont know but its obvious you have no helpful insight and filling my thread with a bunch of useless bullshit.

on another note I talked to YHM today and they dont know whats going on either. I will wait until my other can are released to send the phantom and mounts in though. In a couple weeks I may head to the range with Levi from the silencer shop to test out my phs 338 against their 338BA demo can and I might see if I can talk him into freeing my recce 7 and specwar to test on my gun as well.

[1slow01Z71]

Finally got in one of my Griffin Armament taper mount cans and after the results I saw this afternoon Id definitely say its something to do with the yhm products, whether I got a bum can or multiple bad mounts the issue is somewhere in that system and not the gun.

The group on the left is without the can and the group on the right is with the can. Shot off a bipod and rear bag resting on a crappy concrete bench with a wobbly chair but it gets the job done.

Group measurements(zerod on a 308 bullet)


Approximate shift


Once my Specwar gets here next week I will be pulling all my YHM mounts and sending them along with the can back to YHM in the hopes that they can figure out what is going on. I find it hard to believe they've never had this problem before and that Ive got 4 bad mounts all bought at different times and even different generations of mounts as well as bore sizes.

[whiterussian1974]

I didn't see that you have tried this can on multiple barrels.
Your experience and knowledge of Statistical Sampling show that you clearly know what you're doing.
The only variable that I can suggest is trying it mounted to a different host. Maybe a friend has a threaded barrel.
Otherwise, your low teens SD show that something funky is happening with your system. Either the mounts' interface (teeth or other aspect) or the package combo of platform and mounting system.

Sending can and mounts to Mfr won't yield good results. They would need your Host platform to duplicate the exact conditions.
If this was a common problem, they would have fixed it by this stage.

[continuity]

I'm all kinds of happy with my YHM can. That said, there is something apparently happening with your system relative the YHM suppressor. Given the presented evidence, there may be something going on with the YHM suppressor modifying the projectiles POI, as the suppressor heats up. You haven't specified the range on the grouping and I'll guess it's 100yds.

Using an accurized Rem 700 platform with my 1st gen YHM 7.62QD, I can shoot 1/2'' groups at 100yds, all day long, every day, any day... using a sand bagged front rest from a prone position. While 3 out of 5 shots are single hole, am comfortable in the understanding that group deviance is due to my error. Given my requirements, I'm not gonna look further. But that's just my position.

Stacking the rounds like you present evidence of doing so... especially using a bipod, is awesome. Absolutely impressive pilgrim. Suppressed or not. If the Griffin Armament system gives you that level of performance, and that is what you have to have, sell the YHM.

[rimshaker]

Just for kicks try this. With the same rifle and suspect YHM setup, blow into the bore breech after every shot, and see smoke exiting the can. Or use a can of compressed air so you don't have to shift your shooting position much. I'm almost willing to bet the grouping won't shift down after the 3rd shot.

[1slow01Z71]

Just for kicks try this. With the same rifle and suspect YHM setup, blow into the bore breech after every shot, and see smoke exiting the can. Or use a can of compressed air so you don't have to shift your shooting position much. I'm almost willing to bet the grouping won't shift down after the 3rd shot.

Interesting, what is the theory behind doing this? Ill do it, just wondering what it does. The recce 7 is smaller than my phantom.

[rimshaker]

Just for kicks try this. With the same rifle and suspect YHM setup, blow into the bore breech after every shot, and see smoke exiting the can. Or use a can of compressed air so you don't have to shift your shooting position much. I'm almost willing to bet the grouping won't shift down after the 3rd shot.

Interesting, what is the theory behind doing this? Ill do it, just wondering what it does. The recce 7 is smaller than my phantom.

To entertain the possibility of a thermodynamic design defect inside the can.

[whiterussian1974]

To entertain the possibility of a thermodynamic design defect inside the can.

The barrel will warm the air before it reaches the can. using a straw to drip 2 ccs of water into the blast chamber between shots would yield better result.

I still wonder if the heat is causing some unintended interaction between your mounts and the teeth of the can. I dont own this model, so I'm unfamiliar w the part involved.