Range Report IMR 8208xbr & 77smk

[STI_1911_Guy]

Looking for a varget alternative, my current varget load was 24.2gr. I’m using a WOA 18” Wylde chamber. I am in the process of running IMR 8208 at the common 23.2 gr but I am seeing pressure when I use my rugged surge can. Accuracy is good but pressure is there. Anybody experience this? I’m going to drop down to the next node which I’m guessing around 21.5-22.5.

 

[Steel head]

You sure the pressure isn’t a overgassed condition?

23ish is a well known sweet spot.
I’d just cut the load a couple tenths if increasing bolt dwell doesn’t work.

 

[STI_1911_Guy]

I have played with the block and I’m only one maybe two clicks above lock back. I’ll double check it’s though. I had this same issue with my AR10 I ended up having to run 41.6gr varget 175 smk suppressed and I could run 43.4 un suppressed

 

[BoilerUP]

23.5gr XBR and a 77 = money.

Do you see pressure signs when running a factory Mk262 clone with your suppressor?

 

[STI_1911_Guy]

Never tried 262 clone. I can go well over 24 gr varget and not have an issue so I was surprised by this. Especially since everybody and their brother runs 23.2+.

 

[Soulezoo]

I am using 23.4 with Wolf primers. It's used in several barrels with excellent results

 

[STI_1911_Guy]

I will say not everyone is over pressure. Some are fine then one will spike and loosen a primer. It’s hornady brass.

 

[Steel head]

I will say not everyone is over pressure. Some are fine then one will spike and loosen a primer. It’s hornady brass.

I strictly use LC brass for that load.
I wasn’t impressed with Hornandy 223 brass at all.

 

[STI_1911_Guy]

I thought lake city had even less volume meaning even higher pressure, even if it is a small increase.

 

[ddavis]

My go to load that seems to shoot well in every rifle is a 75 BTHP with LC brass and 23.7 8208. So pretty much in line with what others are recommending, maybe a bit hotter.

 

[nn8734]

Looking for a varget alternative, my current varget load was 24.2gr. I’m using a WOA 18” Wylde chamber. I am in the process of running IMR 8208 at the common 23.2 gr but I am seeing pressure when I use my rugged surge can. Accuracy is good but pressure is there. Anybody experience this? I’m going to drop down to the next node which I’m guessing around 21.5-22.5.

semis can be tricky to shoot reliable with a can as most generate back pressure that lowers the pressure point on the charge weight curve. 23.2 with no suppressor may be fine (I.e no pressure signs) but with the can added, will drive down the charge weight where over-pressure starts to appear. It varies from rifle to rifle so yours may be more pressure-sensitive at lower charge weights compared than a buddy’s, for example.

Do your cases eject at 3 o’clock or is the pattern more like 1-2 o’clock? Do you stove pipe when the can is on?

I thought lake city had even less volume meaning even higher pressure, even if it is a small increase.

Correct, smaller case volume in LC relative to COTS brass means less charge to generate the same MV all other things equal. LC has thicker walls, which is why I also like it...adjust your charges accordingly.
Ignore the crossed out text above - got mixed up with 7.62 stuff.

I’d mount your suppressor do a ladder at 300; start with 20.5g and load up to 23g in .2g increments. Write the charge weight on each case with a fine sharpie....Measure the diameter of each case just above the extractor grove before you fire it and record the measurement. Fire the round, recoding the MV using a chrono or LabRadar then measure again. Record the expansion. I tolerate anything .0015 or less; any more means pressure (other signs may or may not be visible on the case)....You will be looking for nearly identical MVs for adjacent charge weights on the ladder. Your node will be somewhere that range.

 

[whatsupdoc]

LC brass does not have less volume see below. In the winter I use 23.4 and in the summer 23.2 8208XBR in a CBC case with a 77 SMK.
CBC water case capacity is 29.98, less than LC. I am not running suppressed. With 77 SMK's 8208XBR has been faster than Varget.

If you are popping primers you can go down a node or you can try a heavier buffer and recoil spring to slow the system down.


.223 Rem Case Weight vs. Capacity
Case Manufacturer Case Weight* H20 Capacity**
Lake City 06 92.0 30.6
WCC99 95.5 30.5
Sellier & Belloit 92.3 30.5
Remington 92.3 30.4
PMC 93.5 30.4
Hirtenberger 93.7 30.4
Lake City 04 93.0 30.4
Federal 96.3 30.2
Hornady 93.9 30.1
IMG (Guatemalan) 95.4 30.1
Lapua (new lot) 93.4 30.1
Winchester 93.9 30.1
Olympic 97.4 30.0
Radway Arsenal 96.1 30.0
PMP 104.5 29.9
FNM 93-1 97.3 29.8
Lapua (old lot) 104.0 28.0

 

[bunsen27]

Looking for a varget alternative, my current varget load was 24.2gr. I’m using a WOA 18” Wylde chamber. I am in the process of running IMR 8208 at the common 23.2 gr but I am seeing pressure when I use my rugged surge can. Accuracy is good but pressure is there. Anybody experience this? I’m going to drop down to the next node which I’m guessing around 21.5-22.5.

I have the 18" WOA SPR barrel and my load is 23.1gr of XBR8208 in a LC case WIN, small rifle primer, OAL = 2.248", @2680fps, suppressor was a TBAC 30P-1. I don't recall any major pressure signs, but will check my notes.

 

[nn8734]

LC brass does not have less volume see below. In the winter I use 23.4 and in the summer 23.2 8208XBR in a CBC case with a 77 SMK.
CBC water case capacity is 29.98, less than LC. I am not running suppressed. With 77 SMK's 8208XBR has been faster than Varget.

If you are popping primers you can go down a node or you can try a heavier buffer and recoil spring to slow the system down.


.223 Rem Case Weight vs. Capacity
Case Manufacturer Case Weight* H20 Capacity**
Lake City 06 92.0 30.6
WCC99 95.5 30.5
Sellier & Belloit 92.3 30.5
Remington 92.3 30.4
PMC 93.5 30.4
Hirtenberger 93.7 30.4
Lake City 04 93.0 30.4
Federal 96.3 30.2
Hornady 93.9 30.1
IMG (Guatemalan) 95.4 30.1
Lapua (new lot) 93.4 30.1
Winchester 93.9 30.1
Olympic 97.4 30.0
Radway Arsenal 96.1 30.0
PMP 104.5 29.9
FNM 93-1 97.3 29.8
Lapua (old lot) 104.0 28.0

Copy that- i stand corrected...mixed up 5.56 w/ 7.62 stuff.

 

[STI_1911_Guy]

So i ran a quick OCW from 21-23 and found another node around 21.8 but its not as good as 23.0. ES & SD numbers not nearly as good, im not dropping down past 21 or I will be shooting slow enough to try other powders. Adjusted the gas block but no luck, its where it needs to be. I shot more at 23 and no case head swipe or ejector flow marks but randomly one will leak around the primer. I dont have any unused cases to measure case head expansion but these are twice fired previous to this. I am going to try some more around 21.8 and see where it goes but I might end up just running it at 23 and trying different brass and/or heavier buffer and spring. I shot 23gr load and the 21.8 at 600 and the 23 did better at distance also (6 round group pic attached) 21.8 was just over 1.5 MOA but not pictured.

 

[BoilerUP]

What primers are you using?

Try LC or RP brass with CCI 450s or Rem 7.5s.

I use the above with 23.5gr XBR under a 77gr Nosler @ 2.25” COAL and have no issues suppressed with a SiCo Omega and 5.56 end cap or unsuppressed.

 

[STI_1911_Guy]

Using federal AR match primers right now

 

[STI_1911_Guy]

Given what I am seeing and the fact everybody uses lake city brass, what’s the chances the lake city brass would resolve the issue in all honesty?

 

[Steel head]

Given what I am seeing and the fact everybody uses lake city brass, what’s the chances the lake city brass would resolve the issue in all honesty?

There’s good reason LC is popular.
Hell,, I buy all mine once fired and it still out lasts and out performs everything but lapua for a fraction of lapua price.

 

[nn8734]

Given what I am seeing and the fact everybody uses lake city brass, what’s the chances the lake city brass would resolve the issue in all honesty?

If you don’t already have any LC brass, post a WTB thread in the Reloading PX sub forum and pick up a 100 cases or so. Try different primer combos and charge weights. It may solve the problem, it may not but it shouldn’t cost too much to find out for sure.

 

[STI_1911_Guy]

I’ve got some lake city on the way. We will see.