163 gr AP chrono and accuracy results

[mpthole]

40 gr IMR 4064
163 gr AP bullet
once fired Fed GMM brass
Fed GMM large rifle primers
OAL between 2.780 and 2.815
- These are loaded on a Dillon 650 and I can't seem to get a very consistent seating depth.

Test fired in AR-10 16" carbine (.308).

I set the chrono about 3 feet from the bench and got these results:
2425,2446,2421,2425,2407,2425,2528,2486,2481,2479,2447,2442,2485,2433,2453,2494,2516,2396

mean: 2455.11
std dev: 37.54
max: 2528
min: 2396

Excel Spreadsheet with Chrono Results

Accuracy was terrible! At 25 yards I was getting 1" groups and they just continued to open up beyond that. 50 yards = 2". 100 yards = 3" or more.

In the spreadsheet that is linked above, I included another set of chrono numbers for some 147 gr Radway Green. I can almost squeeze a 1" group out of this stuff in the same rifle. I was really hoping my handloads would do at least as well as the surplus.

Any suggestions on how to get some better groups? Change the seating depth; increase the powder charge...? By the way, given the numbers above, what do you think is a safe "maximum" velocity to push these 163's out of a 16" barrel?

 

[Mikul]

I tried 4064 in my FAL and got worse groups than with surplus Portugese. I was sick. Then I tried Winchester 760: much better. I have also used Varget and gotten very good results. I don't know why powder would make an accuracy difference, but it does. Maybe it just meters better.

Your twist rate may be at fault here. Heavier bullets need a tighter twist to stabilize them properly. Anything looser than 1 in 12 would raise eyebrows. Pick up a box of high-quality 168 bullets from Sierra, Hornady, or other quality manufacturer and see how they group.

I would also work on taming those OALs. I load .308 on a 550b. It's set to load to 2.800". It varies from 2.796 to 2.802. Most fall within 3 thousandths. Check your dies, they sound like they're loose to be varying by 1/100th or more.

I don't know how hot that load is, but it sounds like it's near max. I don't see you getting more than 50 fps than what you have. It's impossible to say with the data given if your rifle likes 'em fast or slow. You'll have to play to find out. One of my guns is only happy within 1gr of a particular load 2gr either way and accuracy goes to hell.

 

[Grump]

Are your bullets sorted by weight? Those pulled bullets typically come from many different production runs, all mixed up. That is the most likely reason for OAL discrepancies beyond the normal expectations--one batch has more or less curve on the ogive at the diamter of your seating plug...

Anyway, weigh at least 30, preferrably a full 100. Calculate the standard deviation. Then go plus/minus on standard deviation on the weight and those values become your high & low weight cutoffs. Those in the middle should be about 68 percent of your lot, if the distribution is "normal." Shoot those for accuracy, and the light and heavy batches remain for more informal uses, like shooting standing (unless they won't do better than 4 MOA for each batch--or whatever your tolerance limit is!).

Sorting by weight might even out your OAL problem to maybe twice what Mikul is getting with MATCH bullets.

How fast does Federal GMM shoot from your short barrel? Those long-bearing surface APs should come within 50 fps of those loads, at *probable* safe pressures. All disclaimers apply.

 

[labgrade]

Huge differences in OAL can be scheived by just measuring from brass base to bullet tip. The tips themselves are rarely formed consistently & therein lies the usual OAL measurement. Only bullets I've even seen to be somewhat coonsistant in OAL (& this is just the bullets) was Nosler's Ballistic Tips. I'd bet Hornady's V/A-Max would be equivalent. Just a function of the nose-cone.

You want to measure with something like a Stoney Point OAL gauge which spaces from the bullet's ogive, rather than the tip. Matters.

Too, chrono data, while useful, isn't anywhere as decent as what your loads actually do on paper.

Had a coupla 7-08 loads that did SD=7 for 10-shot strings = should've been tack drivers & weren't, but had another load that did "just" a SD = 9 & was & since it printed accurately, that was the load we chose, even though quite a bit less velocity.

I take great pains to ensure a load development is properly staged off sand bags - yada = all the precautions taken to ensure the most absolutely accurate load I can develop for any given bullet-in-caliber.

Proper bullet construction/weight for the game afoot, best possible accuracy, & really, the rest be damned.

If you can't hit it = all wasted work, & if the bullet won't do what you want = wasted work, but that's for shooting critters. The only use I have for paper is to validate accuracy - & I'd never even use a bullet that wouldn't do for terminal ballsitics. YMMV.

I didn't catch your rifle caliber, mpthole, but suspect from load data/OAL that you're shooting .308, & I woonder why (other than to just play & that's plenty reason enough in my book), you'd even consider using a 163gr AP bullet.

The 168 Match bullets are so much better, & even a 165 Sierra Game King gives so much more flexibility that I personally can't even consider using something that isn't a truely dual-purpose bullet.

But that's just me.

Twist rate, & yanked bullets, as mention may have a lot to do with it.

Personally, I'd pick a factory produced bullet to acheive your desired results (& do keep in mind that many a "hunting bullet" has turned in some fairly amazing accuracy results + has the terminal effects one would want ..... for various reasons) as far as accuracy goes, & many a Match bullet can have some very possitive terminal effects - depending on velocity, caliber, yada.

A .308-caliber bullet, going at almost any speed whatsoever, will tag the target with close to supreme authority. Only the possible "rainbow trajectory" will keep you from decent ranging.

 

[mpthole]

Thanks for all the helpful hints! I'll try to respond more fully later today to some of the questions.

 

[mpthole]

Mikul: Twist rate is 1:10. I don't know why I didn't think to test some Fed GMM when I was at the range - I had some with me even - so I'll be sure to do that next time to see what I can do with that.

Grump: The bullet weights are typically ~ 163, but definitely vary quite a bit. I'll sort by weight and by labgrade's suggestions (re length). These surplus, pulled bullets just aren't uniform.

labrade: Stoney Point OAL gauge. Check. I'll probably be picking one of these up very soon. Yes, I'm loading for .308 and its just for play as far as the AP's go... I like to punch through steel plates and while fun, the .50 BMG can almost get boring after a while (plus very expensive) ergo loading AP in .308.

I'll soon be loading 168 Sierra's for my bolt action so that will be a whole 'nother thing. My bolt gun already shoots well under 1 MOA - I can pretty consistently shoot under 1/2" at 100 yards - with Fed GMM 168's, so my goal in handloading will be to duplicate or improve the performance of the factory rounds and do it cheaper so that I can shoot more frequently.

 

[uglygun]

If you have a 1:10 twist you should be alright as far as stability is concerned...


The 163s are definitely long suckers due to the less dense core material, comparable to a 190grn or even a 200grn lead bullet if you compare the 163grn AP bullet to one of lead construction.


Leave the AR10 308Win chambering alone... Get yerself a 300SRUM upper then load them up


I've effectively done that using a 300WinMag, whoooo doggies does that thing smoke the steel when a 163grn AP bullet is running at close to 3200fps. 1 1/4 inch steel plate of relative nasty hardness.