Vertical stringing help/advice

[Sithlord]

Disclaimer - I'm relatively new to reloading. I've reloaded about 1000 (total) 223 + 300BO.

Details:

9" KAK Mr. Blonde, pistol gas port, standard gas block (non adjustable)
SAS Reaper suppressor
1-4x Primary Arms riflescope
Caldwell Lead Sled
Caldwell Chronograph

150 gr Harandy FMJBT
16.0 gr IMR 4227
COAL 2.058
CCI BR-4 primers

All brass is from factory loads (ie, shot at least once); some from new 300 brass, some from 223.
Lee resizing die, NO CRIMP.

I'm getting vertical stringing (see photo). These two strings are 5-shots from roughly 50 yards with 16.0 gr of IMR 4227 (I was also sighting in the riflescope, but each string used the same settings for the 5-round string). But all of the strings had significant vertical stringing (I worked loads up to 17.5 gr in .5 gr increments). Almost no windage variation. Weather conditions were good (no wind). One round out of all of them appeared to keyhole slightly.

3x 5 shot average of 16.0gr 4227 was 1583, 1582, 1594 fps with STDDEV of 16.9, 27.7, 20.6 (respectfully).

I've talked with two different LGS regarding this issue.

One said the STDDEVs were good, and is at a complete loss as to the issue. Advice: remove the suppressor and try again.
One said STDDEVs were bad, velocities were bad, and didn't really offer advice. Suggested that I should get higher velocity out of a 9" barrel than a 16" (which is counter to what I've read here).

Hodgedon Reloading suggests a 1785 fps out of a 16" barrel, but it's a different bullet (IB, not FMJBT). I used load data that was published here (not going to look for it right now).

So, questions for the masses:
1) Are my chronos and STDDEVs good, bad, ok?
2) Any ideas what could be up with the vertical stringing?

I'm open to suggestions. I'm going to work up the loads again and re-shoot unsuppressed to see if there is a significant difference. In the meantime, any advice from the experts?

[plant.one]

i'm not familar with your combination of powder/bullet personally, but your load seems a little on the hot side based on published data.

hornady's 9th shows a 2.220 COL and a 16.3gr max at that longer col. you're quite a bit shorter than that. how do the primers look?


how are you weighing your charges? are you trickling each one? or using a thrower?


are you using the same headstamp brass for each group? or are they mixed headstamps? what headstamps are in play?


have you checked that your scope mounts and rings are all tight?

[rebel]

Sith, play a bit with the coal. If you can't get that bullet to shoot - move on. That's why I have a lot of powder and bullets, experiments

[Sithlord]

i'm not familar with your combination of powder/bullet personally, but your load seems a little on the hot side based on published data.

hornady's 9th shows a 2.220 COL and a 16.3gr max at that longer col. you're quite a bit shorter than that. how do the primers look?


how are you weighing your charges? are you trickling each one? or using a thrower?


are you using the same headstamp brass for each group? or are they mixed headstamps? what headstamps are in play?


have you checked that your scope mounts and rings are all tight?

Primers look good, even at 17.5gr. Headstamps are mixed. I didn't record the headstamps, to be honest. It's all either original blackout brass (once fired), or once-fired 223, factory resized/reloaded blackout, then fired by me and reloaded by me. IE - I am not using brass that I cut and formed.

Trickle charging each on a RCBS beam balance.

For other reference, these show COALs near mine, but also higher velocity (16" barrels).
From https://sierrabullets.files.wordpress.c ... ackout.pdf:
#2115 .308" 150 gr. FMJBT GameKing C.O.A.L. 2.040"
H4227: 16.0: 1800fps, 16.5: 1850 fps, 17.0: 1900 fps, 17.5: 1950 fps

http://www.dayattherange.com/?page_id=3817:
Sun Devil Lower CMMG Barrel 300BlackOut 16′ 1/7 Twist Pistol Reload IMR4227- 15.9gr – Hodgdon 2012 2.059 150gr Hornady FMJ 1854 1861

[farm use]

Are you using a free float tube? Did you put the upper together?

[Sithlord]

Are you using a free float tube? Did you put the upper together?

Yes (Troy Alpha), and yes. I'm not having an issue cycling my handloads or factory loads.

[smustian]

Take off the suppressor and see if the same thing happens. If it does, then I would guess the barrel nut is not torqued properly. If not, you found your problem.

[ESW]

I shot 30 rounds of 4227 at 17.2 Grains, 3037 Hornady FMJ (150g) yesterday at 50 yards. I went to the pistol range and only brought one rifle so I shot these 30 rounds at 50.

I shot relatively quickly, one shot every 1.5 seconds with a front support that was solid plastic, no sand bag on the rear and 17 of 20 round in a 1.5" group all in the 10 ring with 3 in the 9 ring. I could tell I pulled all three jerking the trigger. Total group was 2.4" or so. If I take my time with this round with sand bags I can easily shoot a 5 shot group of 1" and less at 100.

Mine is a Wilson Billet Upper/lower, Wilson SS Flute 1/8 twist 16" barrel. Free float Lancer handguard. I found in my rifle 17.2g is the more accurate. I'm at about 2.075" COAL

I must say I hate the smell of 4227 and it leave a crazy rainbow color on my BCG too. It's pretty dirty. I'm thinking I need to crimp a bit tighter.

I hope that helps. 16 grains is pretty light. 17.2 is compressed but I've read a few reviews going up to 17.8g. I think I'd spill a lot of powder at that level in my progressing Hornady LNL.

[DeanD1]

Did you try running another proven load or factory to see if you still had stringing? I also agree with rebel on this that OAL looks a little on the short side to me I load nosler BT's around 2.2. Did you by chance check your scope/mounts for looseness?

[farm use]

Are you using a free float tube? Did you put the upper together?

Reason I ask is make sure barrel is tight and the tube isn't binding on anything like the gas tube or block.