Axis II Precision. 223 seating depth question

[StephenBachiler]

I am shooting mostly 77gr SMK out of this rifle. I just measured (using hornady chamber gauge and Comparator) my length to contact the lands and was surprised to see that the Factory 77gr SMKs are theoretically in the lands by quite a bit.
Does this sound right?

[CFJunkie]

Depends upon the age of the chamber.
Regardless of your chamber measurement, you would know when you closed the bolt whether the bullet was in the lands.

I have two 'out of the box' new Savages that had Federal GMM rounds touch the lands when brand new.
I actually set the GMMs back 0.005 in OAL to get them to chamber easily. After 100 rounds or so, I didn't have to do that any longer.
I have found that most Federal GMMs are seated about 0.005 short of SAMMI recommended OALs, but you may have gotten some OAL outliers or your chamber was bored a bit short.

My other 7 new Savages didn't have any problem - at least 0.005 from the lands, brand new.
My new Savages that were bought after 2010 all had chambers that were close to SAMMI OALs.
My oldest 2008 vintage had a chamber that was 0.080 deeper than SAMMI.
All my Savages now have thousands of rounds down their tubes, so throat erosion has long ago eliminated any concerns.
My 12 FV .223 still groups great with 77 SMKs with OALs around 2.360 after 5670 rounds.
Since I reload, after the throat begins to erode, I simply seat the bullet out to the match the jump that works best for the individual bullet in that particular barrel.

[StephenBachiler]

Thank you for the reply - I went ahead and did some additional work on this issue. I made up 3 dummy rounds (no powder or primers) and started with normal seating depths and chambered them looking for contact with the rifling. I noted the CBTO and then pulled the bullets and re-seated .035 longer and performed the same bolt close test...to my surprise I need to go out VERY far before I reached the "jam" point and the lands themselves seated the bullet back for me. Here is my data:

Bullet #1 - Started CBTO at 1.871 and after chambering and extraction measued 1.871
Bullet #2 - Started CBTO at 1.905 and after chambering and extraction measured 1.905
Bullet #3 - Started CBTO at 1.942 and after chambering and extraction measured 2.942

Pull bullets and reseat

Bullet #1 - 1.977 ....still 1.977
Bullet #2 - 2.012....still 2.012
Bullet #3 - 2.048 NOW measured 2.047 AND was sticky to extract

I lengthened to 2.066 CBTO and waxed the bullet and upon extraction (which was tough) CBTO measured 2.055.
So the "jamming" seated the bullet for me 11 thousands (.011)

Still processing what all this means..because the Hornady tool told me 1.857 CBTO was touching the lands. Via my testing I am assuming i was approaching the lands somewhere between 2.012 and 2.048 CBTO.

That is a spread between the two methods of .184 (seems like alot)

The COL at CBTO depth 2.055 is 2.44 inches...WELL above the magazine specification length of 2.26

Any thoughts of the ramblings i just spit out??

[Whynot]

You can't go off of the measurement where it jammed in the lands- and then you extracted it-- because as you mentioned "it was tough".... That often pulls the bullet out of the case a little-- or sometimes a lot--

It should be a repeatable number (within a small degree of error).... so if you don't get the same result doing the test more than once then you have a problem in your procedure.

And .184 is a mile.... so something is wrong. But your number of 2.055 can not be correct because at 2.047 it was sticking..... and you don't know that the bullet didn't pull a little on that one. So you need to work between 2.012 and 2.047 (if that's the process you are going to use)

[charlie b]

When I do tests like this I strip the bolt. No extractor, ejector or firing pin. Then I chamber and feel what it is doing. I use a rod down the bore to 'eject' the round. That way the bullet is not dislodged from it's position, no matter how tight it is in the lands. No I do not use loaded rounds for this.

I do use a marker on the bullets to see when they are 'marked' by the rifling. They will be marked a couple thousandths before the bullet actually touches the lands.

FWIW, all of my .223 loads with the 77SMK's were 2.280oal. That was a jump of around .020".

[StephenBachiler]

Thank you everyone...this is all great feedback...notnsure why I am sweating it as the rifle shoots lights out with the 77gr SMKs over 23.3gr Varget seated at 2.26. I just want to start start playing with seating depth. Most likely I will attempt what is suggested above and see what I get.

I was fire-forming some new Starline .223 brass this weekend using some powder (H335) and bullets (Hornady 60gr VMax & Sierra 55gr SBT that I don't favor and was suprised how well the flat based Hornadys shot at 100 out of the 1:7 twist. The 55gr Sierras did much worse

[charlie b]

Flat based are preferred by many for 100yd (and sometimes 200yd).

The worst bullets I used were the Hornady 55gn FMJBT bullets. But, that's kinda relative. When you shoot a bunch of 0.5MOA groups then a 1MOA group seems huge :)

Please report back when you figure out how many reloads you get on the Starline brass. I stuck with Lapua cause they went over 20 reloads and most of them were still good (never annealed).

[StephenBachiler]

Did you FLS or neck size those?

[CFJunkie]

I too have gotten 20 or more reloads out of Lapua brass in .223, .22-250, 6.5mm CM and .308 over the years - since 2010. I have reloaded more than 56,000 rounds with them during that time.
Like charlie b, I have never annealed either. And I full sized ever round.

Light bullets, even with a 1:9 to 1:7 twist still shoot great in a .223, especially if you are using a faster powder.
Like charlie b, I find that most 55 gr bullets just don't shoot well. The 52s and 53 (Sierra SMKs, ELD-Ms and Bergers) shoot way better. The only 55 gr bullet I have gotten good results with is the Berger 55 gr FB # 22410.

I have found that the heavier bullets shoot better (69, 73 and 77 gr), if you find out how to load them - use a .308 type powder.
Forget the 2.260 recommendations for OAL since you are not shooting an AR.
Load the heavier bullets out so you leave enough room in the case to reduce pressure.
The heavier the bullet, the more pressure build up anyway, so you need to watch out for PMax when you are loading for them.
No reason not to shoot 80 and even maybe 90 gr bullets with a 1:7 twist.

Unless you are hunting or shooting really long distances, velocity only matters to control the harmonics of the barrel. When trying for accuracy under 300 yards, the target doesn't care how fast the bullet is travelling when it goes through the paper. It only matters how close to your aim point the bullets consistently strike.

One of my older .308s, a Savage 10 FCP-K with 4900 rounds down the barrel, managed to average 0.308 for eight 5-round groups yesterday. The 168 SMKs were loaded out at 2.835 using N540 powder and 2.840 using Varget powder - 1 group under 0.2 inches.
Monday a week ago, my 12 FV .223 with an Oryx chassis with 4000 rounds down the barrel, averaged 0.248 for 8 5-round groups. The 69 SMKs were loaded out at 2.356 and 2.364 using N540 powder. 2 groups under 0.2 inches.

[charlie b]

I would neck size only (Lee collet die) 4 times and then FL size the fifth, just to prevent sticky cases. I think I trimmed them once in the 20 reloads. Almost all the loads were 23.5gn of Varget under the 77gn SMK running 2850fps at the muzzle.

FWIW, the 'weak' spot on most .223 brass I have tried is the primer pockets. Most will fail to hold a primer after 4 or 5 reloads. Never split a case. The cheap Federal ammo I started with only went three reloads. Fourth time the primers would not stay in place.

PS CFJunkie, have you tried Peterson brass yet? I got some for my .308 (small rifle primers) and 6BR. They seem to do well, but haven't reloaded them very many times yet.

[StephenBachiler]

Great info. Thank you. I know each rifle has different chamber dimentions..but when you say...seat them out long (past 2.26) give me some number associated with that...2.27? 2.28?

[CFJunkie]

You have a new barrel, so your OALs won't approach what I posted in #9 above for a barrel with over 4,000 rounds through it, but your OAL will be longer than 2.260 recommended by the manufacturers who use the recommended OAL based upon an AR Mag limit.
Your OAL will change for each bullet type.
The bullet length from base to tip and where the ogive is relative to the base is different for each bullet type and weight.
That difference determines how much of the tip is sitting out into the lands and not touching so the ogive determines where the bullet needs to be seated.
The OAL that provides the jump that performs best for each bullet type in your particular barrel will give you the answer.
are
SMKs and Nosler CCs are relatively short in the tip compared to TMKs or ELD-Ms so the SMK/CC OALs will be shorter than the longer tipped bullets like TMKs/ELD-Ms to get the same jump.
By the way, all four set for the OAL that works best for each bullet have about the same group sizes for me at 100 yards over very large group samples.
On one of my good days, one might produce slightly smaller groups, but for the long-term average with large group samples they perform about the same - within 0.010 difference in average at 100 yards for both 69 and 77 grain bullets for the SMKs/CCs and 73 gr for the ELD-Ms.
For my barrel, the 75 ELD-Ms don't seem to perform as well, but that is for a smaller sample so it could have just been a bad day.
Or maybe I haven't figured out that particular bullet seating depth yet.

You will have to figure out where each bullet type performs best for your particular barrel and chamber, but I don't think you will even notice a 0.010 difference in seating depth with a particular bullet unless your 5-round groups are consistently under 0.300 at 100 yds.

charlie b, I haven't tried Peterson brass.
I guess I am stuck in the Lapua brass rut, but since Lapua has performed so consistently for so many years, I probably won't, unless Lapua starts messing up what has worked great for me.

[charlie b]

Mine were all at 2.80" oal for the 77 and 69 SMK's. Just barely fit in the magazine. I liked the 75ELDM's but when seated where they did well they were too long for the magazine.

CF, yeah, I would not have tried them but Lapua brass has been difficult to find lately, at least the 6BR and Palma .308

[CFJunkie]

charlie b,

Wow! 2.800 OAL for a .223. You do have a very deep chamber. You must be single loading those rounds.
The MDT AICS mag on my Oryx chassis lets me load .223 rounds out to 2.500, but I haven't had the need to load them out that far yet.
I'm not sure the 69gr bullets would be still in the neck or at least maintain consistent neck tension at 2.500.
For 80s and 90s maybe, and I'm not even sure 77s would still have consistent neck tension.
Fortunately, I never had to load out that far.

I replaced the barrel in my first .308 when I had to load out past 2.970 because I started to see loss of accuracy - I believe because of inconsistent neck tension loading that far out.
The Savage mag let me load out almost that far, but when I passed 2.950 OAL, I had to single round load.

As for Lapua brass, fortunately, I reload calibers that still seem to be available - .223, 6.5mm CM, .308 .22-250.
Sorry to hear that you're not able to find 'the good stuff' for your two calibers.

I will have to look to replenish my supply of .223 since I just opened a new box of 100.

[charlie b]

Sorry, 2.280 lol

[Dave Hoback]

Flat based are preferred by many for 100yd (and sometimes 200yd).

The worst bullets I used were the Hornady 55gn FMJBT bullets. But, that's kinda relative. When you shoot a bunch of 0.5MOA groups then a 1MOA group seems huge :)

Please report back when you figure out how many reloads you get on the Starline brass. I stuck with Lapua cause they went over 20 reloads and most of them were still good (never annealed).

LOL! Yeah I have a bunch of those. Everyone comments on them being so inaccurate. But it’s exactly as you said. Relativity… ie., going from .5moa or less in a bolt gun, to 1moa. Reason enough to call them out for sure. But for AR15 ammunition, shooting standard LC m193, m855 5.56 or even Remington 55gr 223, which are grouping maybe 1.5-2” on a good day, these Hornady 55 bthp’s loaded & shooting 1moa suddenly become very, very handy ammo. And I like them strictly for that purpose. At the price I was able to grab them for, they make for fantastic general & range reloads.

[StephenBachiler]

Update - I loaded up 3 rounds each of 23.3gr Varget and 77gr SMKs into various seating depths.
2.260 COL (1.874 CBTO)
2.263 COL (1.877 CBTO)
2.266 COL (1.880 CBTO)
2.270 COL (1.883 CBTO)
2.272 COL (1.885 CBTO)
2.273 COL ((1.888 CBTO)

It was hard to get these precise with my standard RCBS dies
There were no issue with Primers or bolt lift
The longest rounds ejected (before firing) with no issues and no visible marks on the bullets.

All of the 3 three shot "groups" were under MOA at 100 yards (95 yards)
Conditions were perfect - 73 degress and 1mph wind
The two best groups were at the two longest seating depths measuring .29 and .35
I plan on doing this experiment again and starting with those seating depths and work out a little longer.

[Whynot]

The 77 SMK is a very forgiving bullet as far as jump goes (it has to be for mag fed semi auto). That's good shooting and the fact that all loads shot well is a good sign.... but 3 shots is not enough to get any real info.

I've done tests where I "found" a depth or a powder node based on a few shots- and the next time that I went to confirm it was something completely different. (And now many people are saying that nodes or velocity flat spots are not even a real thing??)

Add in the fact that as you change seating depth you also can change neck tension and case capacity on top of the fact that you already could have small variables in the cases/primer/powder/bullet- and it makes it very difficult to come to any conclusion off of small sample sizes.

[StephenBachiler]

I don't doubt that at all. This was just a first run...who knows if it is repeatable...but it was fun none the less!!
Unfortunately i noticed the very beginnings of what I believe to be some neck splitting in my twice fired Hornady cases (once factory and once reloaded) it is VERY faint, but noticeable and the case mouth seem to be a bit "out of round" when viewed from above. It is like the circular mouth opening has been SLIGHTLY pushed inward. It makes me think there might be a issue inside the chamber or upon extraction

[charlie b]

Keep in mind how the extraction and ejection works.

As the bolt moves to the rear the ejector is pushing on the case. The extractor claw is holding it, acting like a pivot. As the shoulder of the case passes the base of the chamber the neck will 'slam' against the edge of the chamber. Then as it clears the bolt recess it will 'slam' into the side of the action. Finally it will go past the forward edge of the receiver opening and it will be shoved out (ejected). If the necks are thin or soft they can be deformed from this sequence.

To check if the chamber is bad you'd need to remove the ejector plunger (easy to do) and then pluck the case off the face of the bolt after firing.

[GrenGuy]

Hornady and Federal Brass is famous for being soft. Neither hold up well to multiple or high end reloads. They almost always dent or dis form upon ejection, as charlie b pointed out. Their primer pockets fail soon also. There is a reason Lapua brass is so popular among volume shooters.

The up side to soft brass, at least as the theory goes, it contributes to accuracy on the first firing. It supposedly obtulates (spelling?), sealing the case to the chamber. This is said to be why, or one reason, Federal Gold Medal Match Ammo is known to be so accurate.

I did did say it is a Theory ��

[StephenBachiler]

This is all great information and thank you for replying...keep it coming. Let me ask for your thoughts on another issue I am having. All my fired brass has a gouge in it about 2/3rds of the way up the case. It looks like a sharp point etched out a bit of brass. It is very small, but visible and you can feel it when you run your fingernail over it. So i broke out the borescope and I believe I found the culprit. A small rough spot in the chamber. It lines up via measurement with the ding on the case. What I think is happening it a slight scratch occurs when chambering and upon firing (and case expansion against chamber wall) it depresses into the case. I cleaned the living you know what out of the bore/chamber and just went and fired some factory rounds to see if the problem was fixed....it was not. So my question is:

How do I solve this problem? I would post pictures but I think I don't have that privilege yet. Obviously this is (i assume going to screw up my reloading if everytime I fire a case it gets damaged.

[GrenGuy]

Could start with some Flitz on a chamber mop, spun with a drill. If it’s bad enough, it could need a chamber reamer run in. But before I would put much money in a barrel like that, I would replace it with an aftermarket. Good Luck...Good Shooting.