223 77 gr SMK and CFE 223

[Sumtoc]

Have a buddy who wants to get into F-Class and will be starting with a 223 F T/R set up. Barrel is a fresh pre-cut Lilja 1:7, 28", Savage receiver. He has several thousand 77 gr SMKs and 16 lbs of CFE 223 so naturally we want to use those for his starting load. While neither may be optimal for the 600 yard matches he plans to shoot, we're looking for advice on velocity nodes, bullet seating depth/jump and any other experience with this combo. He can shoot this combo while learning a bit about the wind and gun handling, then we'll move him to a heavier bullet and different powder later.

Thanks

 

[Twdmar]

I have shot a lot of 77s out of a service rifle with a 20" barrel, unfortunately not with cfe 223 but I do know it can be accurate.
A good node for the 77s out of the 20 inch is about 2750ish. With 8" more you may reach another node but I don't know what it may be.
As far as jump, 77s are meant to shoot mag length out of an AR. I have never had a sierra bullet not do well with .025ish off the lands.
I like a primer like a remington 7¹/² but the cci 450 looks good the little bit I've used.
Try that first And do a ladder test.

 

[mac86951]

2750 sounds HOT from a 20" barrel! I won't say not doable, and I'm sure a service rifle can take it?!? But im at 2650 from a 20" WOA; and at 600y i find the waterline is stable and brass gets long life. Ehh, maybe I'll try another work-up too.

CFE will work to get you out to the range; 77s are jump tolerant, CFE meters well. +1 above in service rifle; which is where the 77 is most often used.

I'd say load some up at 2.260 and !work up! to 24.0gr and go get some trigger practice. 77 is about as heavy as will mag feed, so I'd say start there and get some practice reading the wind. Most of my 223 chambers have a node in the 23.8-24.2 range.

77s aren't bad at 600; you can seat them long; up the powder (keep working up).

Eventually, 80/80.5gr or a 75VLD, or... Well honestly, i haven't heard too many people posting 223 F/TR loads here; they quickly switch to a 308 when serious, and that's $$$; shame.

Keep an eye out for Varget, n140, h4895. Measure all charges, be as accurate as you can. Did you know Varget is 0.1gr/3-kernels? Wanna know how I know, i shoot a 223!

-Mac

 

[Twdmar]

2750 sounds HOT from a 20" barrel! I won't say not doable, and I'm sure a service rifle can take it?!? But im at 2650 from a 20" WOA; and at 600y i find the waterline is stable and brass gets long life. Ehh, maybe I'll try another work-up too.

CFE will work to get you out to the range; 77s are jump tolerant, CFE meters well. +1 above in service rifle; which is where the 77 is most often used.

I'd say load some up at 2.260 and !work up! to 24.0gr and go get some trigger practice. 77 is about as heavy as will mag feed, so I'd say start there and get some practice reading the wind. Most of my 223 chambers have a node in the 23.8-24.2 range.

77s aren't bad at 600; you can seat them long; up the powder (keep working up).

Eventually, 80/80.5gr or a 75VLD, or... Well honestly, i haven't heard too many people posting 223 F/TR loads here; they quickly switch to a 308 when serious, and that's $$$; shame.

Keep an eye out for Varget, n140, h4895. Measure all charges, be as accurate as you can. Did you know Varget is 0.1gr/3-kernels? Wanna know how I know, i shoot a 223!

-Mac

2750 is doable and yeah, possibly pushing things a bit. BUT, work up to it obviously. I get over 2800, according to the magnetospeed, with 80 smks. It's hard on brass but I can get a few loadings with LC. The AR has a strong bolt and except on really hot days I don't worry about it.

 

[jelenko]

Using GRT [Gordon's Reloading Tool] and with fired case volume = 31.2 gr of H20 and a COAL = 2.250,
it says there are nodes at

24.7 gr; 2828 fps, 46K pressure​

25.4 gr, 2909 fps, 51K pressure​

25.8 gr, 2952 fps, 54K pressure.​

​

These might be close for your rifle and fired case volume. If you have the fired cases volume and COAL of the round, I can update GRT with them. Better would be to also fire 5-10 rounds across a chrono and record the average muzzle velocity. GRT can be 'calibrated' to a powder, rifle, bullet with that data.

The powder charge for predicted nodes is fairly sensitive to the fired case volume - changing about .5 gr of powder for .5 gr change in case volume.

I've had pretty good luck finding nodes where GRT predicted them or within +/- .2gr. There have been times when a predicted 'node' never gets under 1 MOA but other predicted nodes are 1/2 MOA or better.
Because I test from prone with a sling, finding nodes that are less than 1/2 MOA are limited by my test set up.

 

[JB10]

I am using 75gr bthp hornadys with cfe223. Not same bullet but close in weight. I have not taken passed 300 yards yet but it has good accuracy out of an 18inch AR.

 

[skeeljc]

+1 for the Hornady 75 grain BTHP. I use Reloader 15 in a 18" White Oak 1 in 8 twist. 24 grains of RL-15 produces around 2750 fps.

 

[RegionRat]

2750 sounds HOT from a 20" barrel!

BTW, I agree it isn't mild, but it is also a standard and near to Hot but still has margin for weather. It is what you would get from factory ammo like Black Hills or IMI, etc.

It is also why the brass in a Service Rifle only goes about four cycles....

 

[Sumtoc]

Using GRT [Gordon's Reloading Tool] and with fired case volume = 31.2 gr of H20 and a COAL = 2.250,
it says there are nodes at

24.7 gr; 2828 fps, 46K pressure​

25.4 gr, 2909 fps, 51K pressure​

25.8 gr, 2952 fps, 54K pressure.​

​

These might be close for your rifle and fired case volume. If you have the fired cases volume and COAL of the round, I can update GRT with them. Better would be to also fire 5-10 rounds across a chrono and record the average muzzle velocity. GRT can be 'calibrated' to a powder, rifle, bullet with that data.

The powder charge for predicted nodes is fairly sensitive to the fired case volume - changing about .5 gr of powder for .5 gr change in case volume.

I've had pretty good luck finding nodes where GRT predicted them or within +/- .2gr. There have been times when a predicted 'node' never gets under 1 MOA but other predicted nodes are 1/2 MOA or better.
Because I test from prone with a sling, finding nodes that are less than 1/2 MOA are limited by my test set up.

I also used the 77 SMK a bit for rapid prone @ 300 yds in XC matches. (Went back to the 69 gr SMK for simplicity since it's what I used at 200 yds.) But I used a lot of Varget back in those days and it's very hard to find now. Never used CFE 223 for anything.

My buddy actually loaded 6 different charges, 5 rounds each and we recorded them using my LabRadar:

Shot #	23.0	23.3	23.6	23.8	24.0	24.2
Shot 1	2556​	2619​	2613​	2694​	2721​	2727​
Shot 2	2594​	2595​	2648​	2688​	2716​	2752​
Shot 3	2561​	2620​	2617​	2657​	2671​	2697​
Shot 4	2574​	2623​	2659​	2677​	2681​	2714​
Shot 5	**	2617​	2663​	2657​	2701​	2733​

** Shot #5 with 23.0 gr was the first shot from a clean/cold barrel, outlier.
We started pretty low just to be safe but saw some flattened primers with the 24.2 gr charge. I failed to tell him to load these well off the lands and I believe he had them just off the lands, about .003". This is probably why we saw pressure signs "early". These were virgin Lapua cases and Tula magnum primers (which he also has a lot of....). I'll ask him to load them .020-.030 off the lands for further charge testing. May even load them all to mag length. Just need to get further off the lands.

The 23.3 looks like a slower node, especially if you drop that slowest shot. We are going to load in .1 gr increments around that one just to be sure. We also need to fire form this virgin brass before we start the more serious testing so these OCW tests will help with that.

jelenko: does this data help refine your GRT model? And if so, can you share any new specs? (I can share the H20 capacity of a fired case later if needed)

We'd like to find the higher node and dial that in....

Thanks

 

[Twdmar]

More powder. Use a ladder test to find a node and pressure limits for his setup. Ball powders often burn more consistently with a fairly stout load too.

 

[Sumtoc]

More powder. Use a ladder test to find a node and pressure limits for his setup. Ball powders often burn more consistently with a fairly stout load too.

Yep, that's my thought too. Just need to pull them back off the lands to relieve some of the early pressure.

 

[jelenko]

Sumtoc - What is the cartridge overall length? About what temperature were the rounds at? Can you measure the amount of H20 that fits in one of the fired cases?

Assuming the COAL was 2.35 and the temp in Florida was 70 degrees and the velocity data from 24.2 gr of CFE 223, GRT predicts the following nodes [but, the predicted nodes will change by several/many tenths depending on the actual COAL, the H2O capacity of the case and the actual temp

24.3 gr 2736 fps 40K pressure [pretty low pressure]​

26.0 gr 2925 fps 50K pressure​

26.4 gr 2975 fps 53K pressure​

​

 

[Sumtoc]

OAL was 2.3705" temp was around 55 degrees, kinda chilly for NW FL. Just spoke with my buddy and I'll post the case H20 when he sends it to me.

Thanks for the help

 

[jelenko]

FYI. 24.2 gr of CFE 223 with that COAL produces low enough max pressure that GRT has trouble with it.
It would help if you could get the velocity of 5 shots at, say, 25 gr.

 

[Sumtoc]

FYI. 24.2 gr of CFE 223 with that COAL produces low enough max pressure that GRT has trouble with it.
It would help if you could get the velocity of 5 shots at, say, 25 gr.

Case H20 capacity weighs is 31.6 gr. Odd that it has trouble with the 24.2 since it registered avg velocity to be 2725 fps. This may be because they are seated so close to the lands?

 

[jelenko]

It's just GRT's ability to do a simulation when the max pressure is too low. Just an issue with their mathematical model.

A parameter in GRT can be adjusted to account for the low pressure but may cause the predicted powder charge to be off a bit. My experience is the predicted charge is different by ~ 1/2 of 1/10 grain. Again, I think of GRT as useful for getting close to the optimum charge. I doubt, except for chance, that it's the actual point of tune.

So, with that case volume, GRT predicts nodes

24.4 gr 2745 fps 39.5K pressure​

26.1 gr 2938 fps 50K pressure​

26.5 gr 2982 fps 52.7K pressure with this load, the fill % is 96% and the burn ratio is 98%.​

​

GRT also says there might be a node at 25.4 gr, but that node can be problematical due to the timing of when compression waves arrive at the muzzle.​

​

If you don't get to the range often/it's a fair distance, I would go with charges at the predicted node and ones at +/- .2 gr.
If you're looking for actual tune, my understanding is you'll need to further fine tune the charges based on what shows up on the target. I stop tuning when I get some 1/2 MOA groups - i.e., pretty far away from what I see others get when tuned.
There's also tuning with seating depth - maybe someone else will mention at what point you should try seating depths.