Sierra .223 Rem load data confusion

[dboyles]

Sierra publishes load data for .223 Rem, and separates it by bolt gun and AR-15 applications. In their .223 cartridge guide, AccurateShooter.com mentions the AR being more sensitive to pressure than a good bolt gun, and I've always assumed that to be the case.

Why would the max published bolt gun load for a given powder/bullet/primer/COL be lower (sometimes significantly so) than the same for an AR-15? This is Sierra's load data for their bullets and Hodgdon powder (I've got a bunch).

components     bolt max   AR max   diff
45gr / H322      25.3      25.7    -0.4
45gr / H335      28.3      27.7    +0.6
50gr / H322      24.9      25.2    -0.3
50gr / H335      28.0      26.4    +1.6
52gr / H322      24.3      25.2    -0.9
52gr / H335      27.6      26.7    +0.9
52gr / Varget    26.7      27.5    -0.7
55gr / H322      23.9      24.3    -0.4
55gr / H335      27.5      25.7    +1.8
55gr / Varget    26.9      27.2    -0.3
69gr / H335      25.7      23.8    +1.9
69gr / Varget    26.4      26.1    +0.3

H335 looks like what I'd expect: a reduced load compared to the bolt gun load. Varget looks backwards on the lighter bullets, and H322 looks backwards all around (except if you look at the data for the 63gr SMP with H322, where the bolt gun load is slightly higher).

I'm not particularly concerned with the actual number on the published max loads (I'll work up the load from a safe starting point), but I'm curious about this pattern. Is there something about H322 (and maybe Varget) that would generally have you running a hotter load in an AR than in a bolt gun?

 

[Johnboy]

by no means am I an AR guy.but I do want to take a stabb at it.

really think about your question.shouldn't be too hard.a bolt gun works from the bolt up and all the pressure ends up OUT the barrel.an AR runs off the pressure to work the bolt each time.so the difference is that a bolt can only stand so much before bad things begin to happen.the AR uses the pressure to work so a little more pressure is needed to operate the bolt along with pushing the bullet out.

one needs the energy to just work the bullet.the other needs it in two places at the same time.

 

[bigedp51]

Two things to remember with the .223 and 5.56 NATO the leade or throat differences between military and civilian rifles. And military chamber pressure is measured at the neck of the cartridge and civilian SAAMI chamber pressure is measured at the mid point of the case body. The military method of pressure readings at the neck read higher than the same pressure measured at the mid point of the case body and this causes mass confusion.

My Stevens 200 .223 has a 1 in 9 twist and a longer throat and I can safely shoot both types of ammo, a civilian .223 with a 1 in 14 or 1 in 12 twist will have a short throat and if military ammo is fired you will have pressure spikes above normal operating chamber pressure.

Please read the link below with the explanation in detail.

http://www.m4carbine.net/showthread.php?t=55149

On top of this you have a multitude of different chamber reamers and throat variations.

 

[dboyles]

I might not be interpreting your responses correctly, or maybe I didn't phrase my question well. A call to Sierra may be in order.

Why would H322 bolt gun max loads be lower than H322 AR-15 max loads when the exact opposite is true for H335?

The data sorted another way:

 

[dboyles]

I emailed Sierra and here's what I heard back (quick response, too):

This is an anomaly. It may or may not duplicate on different firearms. We
quote to you what took place in the 2 firearms that we collected load data
with. We recommend that you use the action specific data and start at the
minimum load and watch pressure signs closely. You are using a different
gun, lot of powder, primers, cases, and can expect to see slightly different
results. Thanks

That's about what I expected to hear, but I may ask Hodgdon if those types of results are typical.

 

[RoDog]

WEIRD....223 REM DATA..

---

HORNADY ----55gr FMJ-BT W/C - MIN - 20.8, MAX - 23.2 (H335) (ELEVENTH EDITION) REM 700
SIERRA ------ 55gr FMJ-BT W/C - MIN - 23.6, MAX - 25.7 (H335) (SIXTH EDITION) AR15

I'm going to load some in commercial and NATO cases and see what happens
with 22.0gr in both. I'll post a result soon. (AR-15)

 

[Doom]

Here is some info on this old thread. The AR data has not been updated from V5 while the bolt gun data from V5 was from a Rem 600. The bolt gun data for the H335 was much high than the new data which was established with SAAMI testing. The V5 bolt data for 335 was too high for a hot data. The max was 27.5 and 3300 fps.

The AR is not sensitive to chamber pressure but is sensitive to gas port pressure and this this veries with the different gas systems. If you don't have an adjustable gas block then you need to pay attention to where your brass is ejecting.

 

[chkunz]

I think that the Max load is not an exact number. It is somewhat dependent on a lot of variables. I think you are seeing the variability in the estimate of the max load based on these variables.

 

[Doom]

The max loads shown are applicable to multiple bullets in both sets of data so the maxes may not be set by the bullet(s) in question.

 

[arlaunch]

Reloading guides are just a guide. Comparing differences from one thing to another in all the different publications will drive you mad!

Then when you play with seating depth, things are even more skewed.

Just guides.

In a bolt rifle or an AR-15, i go until i see pressure. Or groups clearly deteriorating.

Sometimes that is way above or below a max published charge. And that depends on the book!

 

[dcali]

Book data is only so good. In my experience, bolt guns can handle more than ARs, but that's just my limited experience with a handful of rifles. Milage may vary.

 

[Doom]

The old V5 Sierra data lead me to a locked up bolt back when I first started reloading. I had a load in the 26 gr range that showed no pressure signs at 70F but at 97F it locked the bolt. It taught me a couple of things. One was take any reloading data as a "guide". It also sought me to look at more than one source of data.

 

[ar15Jeff]

I agree with Doom, AR's are more limited by the port pressure. It appears that the bolt is trying to extract the case before pressure drops and the brass contracts in the chamber. The result is bent or torn off cartridge rims. I found this more apparent on "match" chamber dimensions in AR's than in bolt guns. Also, bolt guns give you that "sticky" bolt feedback when in the danger zone. AR's leave you with a stuck case in the chamber.

 

[RoDog]

This weekend, im going to test some rounds. Commercial and NATO cases, Starting at 22.0, slowly working up till the cases show pressure signs. 22.0, 22.5, 23.0, 23.5 , etc. Ill post the results here.

 

[Doom]

This weekend, im going to test some rounds. Commercial and NATO cases, Starting at 22.0, slowly working up till the cases show pressure signs. 22.0, 22.5, 23.0, 23.5 , etc. Ill post the results here.

Guess we wasted our time!

 

[Flouncer]

This weekend, im going to test some rounds. Commercial and NATO cases, Starting at 22.0, slowly working up till the cases show pressure signs. 22.0, 22.5, 23.0, 23.5 , etc. Ill post the results here.

Aren't the case capacities different ? NATO / commercial (.223 Rem ?? )

 

[Laurie]

There's a fairly straightforward reason for Sierra's higher AR loads - chamber differences. The bolt-action loads will have been worked up to 55,000 psi in a SAAMI spec pressure barrel with a full SAAMI-spec chamber with its 25-thou' throat length and 3.1-deg angle leade.

The AR data uses a Colt AR-15A2 and its very different chamber. The giveaway is the 80gn SMK COAL of 2.550". There is simply no way you can physically chamber such a round in a SAAMI chambered barrel. This chamber form is often referred to as a '5.56 chamber' with or without 'NATO' as a suffix. However, most 5.56 reamers for gunsmiths are specced at shorter throats, a few thou' shorter than their Wylde chambers. When I had a 'PT&G Match' (modified Wylde with around 10 thou' greater freebore) chambered AR many years back, the 80gn SMK COAL was somewhere around 2.44" when just off the lands, a full 100 thou' below that used in the Sierra AR-15A2 HBar rifle table.

See the following. It's an interesting read in itself about using 5.56 ammo in a 223 Rem barrel, but the relevant passage is the second section looking at chamber differences with a table of different reamer makers' dimensions for the three main chamber forms - 223 Rem SAAMI, Wylde non-standard 223 Rem, and 5.56 NATO.

https://www.luckygunner.com/labs/5-56-vs-223/

You do see handloading data for the 80gn SMK in 223 Rem SAAMI test rigs and the COAL is usually quoted at around 2.35", or 90 thou' over SAAMI. This is simply a function of the bullet's longer nose and its taper. With the point on the ogive that is around bore diameter seated just off the lands you have more nose ahead of it than with lighter or blunter bullets. But we're still massively away from 2.550" COAL.

The pressures generated by chambers allowing those two COALs are very different. If you play around with it in QuickLOAD it's around 6,000 psi IIRC allowing the AR HBar to use charges around a full grain heavier before producing same pressures. That's why 223 Rem FTR shooters whose freebores are very long indeed starting with the PT&G 223 Rem ISSF's 0.169" and can go up to over 200 thou' run with charges of H4895, VarGet, and Re15 with 90gn bullets that would blow primers with much lighter projectiles in a SAAMI, or even Wylde chamber. (See @Ned Ludd 's posts on this forum about loading the 223 Rem with >80gn bullets for FTR competition.)

As with any cartridge, case make/construction matters and affects pressures with any particular bullet/powder combination through capacity variations. In 223 with its small case, it can make a very large difference indeed. My older 223 Rem Lapua match cases hold 31.0gn water when fireformed, but QuickLOAD's default case capacity is 28.8gn. Model loads for the 77gn SMK at these capacities and you get a c. 8,000 psi difference with many powders. However, unlike 7.62 v 308 Win, the NATO case may not always be the lower-capacity version, Lake City brass being high-capacity for instance. But then again, it can be. When I shot an AR, being a Brit, it had to be manually operated as semi-autos (other than .22 rimfires) are legally 'Prohibited Weapons' here. Even with a very efficient and ergonomic side handle bolted onto the bolt-carrier, you soon learned all about chamber pressures thanks to the combination of the AR design's lack of cammed primary extraction and absence of gas-pressure to do the hard work. The bolt started to become noticeably harder to pull open with loads that QuickLOAD calculated as breaking the 55,000 psi mark. British military L2A2 5.56 cartridges which run at around the 60,000 psi peak pressure level were a swine to get out needing a really hard tug on the handle to break their seal in the chamber. Having worked loads up in roomy Winchester brass, I bought a couple of hundred new German MEN military-spec cases from a commercial ammunition producer and without thinking transferred one of my usual loads to them. It was a both hands on the handle job to get the bolt open. I can't remember now how much I had to reduce the charge, but it was (by 223 Rem standards) a lot. This could affect the Sierra data-sets as one ('Bolt-Gun') uses Winchester brass and the other (AR-15) loads are quoted for Federal. However, as Winchester usually has a significantly greater capacity than Federal, if that were the only factor it would see the bolt-gun loads higher than the AR equivalents which is the opposite of the case.

 

[RoDog]

Aren't the case capacities different ? NATO / commercial (.223 R

Guess we wasted our time!

What does that mean, Wasted our time?

 

[Doom]

The AR15 will likely have its gas system over pressurized long before you see case issues. That is unless you have an adjustable gas block that you tune to the load.

As for cases, you develop a load for a specific case. Pick one and develop a load for it. Once you have that load, you can usually tweak that load to a different case in 9-12 rounds. Your powder increment is too large if you are looking for accuracy. Try 0.2 gr.

So which bullet, powder, max load are you planning on using?

 

[RoDog]

The AR15 will likely have its gas system over pressurized long before you see case issues. That is unless you have an adjustable gas block that you tune to the load.

As for cases, you develop a load for a specific case. Pick one and develop a load for it. Once you have that load, you can usually tweak that load to a different case in 9-12 rounds. Your powder increment is too large if you are looking for accuracy. Try 0.2 gr.

So which bullet, powder, max load are you planning on using?

I have 2000 more Hornady 55gr FMT-BT W/C (#2267) to load, with NATO cases, using H335. (I load to 90-95%) Was going to start at 22.0gr and work up, etc

The other powder I was using was AA2200, but ran out. I was using 23.3gr to 23.5gr (Commercial cases about a grain less) of AA2200, and shot fine with NATO and comm cases, ejecting around 4 o'clock.