338 ARC

mig1nc said:

I could have sworn I saw somebody making 338ARC barrels with a 1:6.5 Spectre twist but now I can't find it.

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Haven’t seen any 6.5 twist, but Mos-tek is doing a 5 twist.

I think the 1:5" would be the way to go. My 338 Spectre is a 1:6.5". When the big 300gr Maker solids hit paper they look like they want to start tumbling. There's a crescent shaped side to the bullet holes. I believe they fly straight, but they are on the edge of stable and just the cardboard causes them to start to wobble. They aren't spitzer, boat tail bullets with that type of COG. They're more like a lincoln log. I think they require a little extra twist. If you're shooting conventionally shaped BT spitzer bullets a 1:6.5" will be fine. I definitely wouldn't do an 8".

Now if we could get a CMMG radial delayed barrel extension on those.....

mig1nc said:

I might be a weirdo, but I'd love to see somebody make a roller delayed .338ARC with the purpose being to eliminate piston and port pop from the sound signature. The cartridge should be a very good fit, especially since Hornady designed it to have minimal variances between supers and subs, so you may not need more than one angle for the rollers.

The caveat being that I would want it to have an extruded aluminum upper with steel reinforcement inserts on high wear areas. Stamped steel HK53 type guns are way too heavy to be competitive in today's market.

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Why do you think roller delay would be better at reducing port pop than gas delay? I haven't heard that e.g. a HK53 or ZF-56 is any quieter than an AR platform.

JR1200W3 said:

I think the 1:5" would be the way to go. My 338 Spectre is a 1:6.5". When the big 300gr Maker solids hit paper they look like they want to start tumbling. There's a crescent shaped side to the bullet holes. I believe they fly straight, but they are on the edge of stable and just the cardboard causes them to start to wobble. They aren't spitzer, boat tail bullets with that type of COG. They're more like a lincoln log. I think they require a little extra twist. If you're shooting conventionally shaped BT spitzer bullets a 1:6.5" will be fine. I definitely wouldn't do an 8".

Now if we could get a CMMG radial delayed barrel extension on those.....

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The 6.5 twist not only stablizes the 300 gr bullets ...it also stablizes the 350 gr bullets.

I have a 6.5 twist 338 Spectre and it shoots 300 gr Maker and slightly longer 300 gr
Berger into tiny groups.
The Maker bullets are twist specific this box is for 6.5 twist 338 Spectre.
I am a fan of the 6.5 twist as I run it in 8.6 Blkout and 338 Spectre, and have scrapped my 3 twist as unworkable.
The 5 twist may be ok for subs but it still spins bullets in super unnecessarily fast.

The 338 ARC & Spectre are smaller capacities helping them out in the sub category for velocity consistency.

Hornady runs the 8 twist and their 307 gr bullets rather blunt. But if the 307 gr works exceptionally well and fairly cheap plus available in factory loading.
I wouldn't hesitate to get the 8 twist, as it will be better for light supers...and cast lead bullets like the 300 blackout.

Here is the 300 Berger and 350 Maker. Note the bullet box is 338 Spectre 6.5 twist, both easily stablize in the 6.5 twist.
The 338 ARC and 338 Spectre are very similar as pictured with the longest bullet being a 350 gr Maker.
The 350 gr Maker modified to bore rider has no trouble stabilizing as shown here in the 6.5 twist 338 Spectre.
The 6.5 twist 165 gr Maker Super is made for supers to 2100 fps and 6.5 twist specifically so they don't come apart.

I don't plan on hunting with any of them, so it's up to the individual to decide. I just test and shoot them for fun.

From my experience, I think a 1:5" may be necessary for non-spitzer, solid subs that have a more forward COG. And I say this from a perspective of experience at 7000ft asl. Someone at sea level would benefit even greater from a faster twist.

45-90 said:

The 6.5 twist not only stablizes the 300 gr bullets ...it also stablizes the 350 gr bullets.

I have a 6.5 twist 338 Spectre and it shoots 300 gr Maker and slightly longer 300 gr
Berger into tiny groups.
The Maker bullets are twist specific this box is for 6.5 twist 338 Spectre.
I am a fan of the 6.5 twist as I run it in 8.6 Blkout and 338 Spectre, and have scrapped my 3 twist as unworkable.
The 5 twist may be ok for subs but it still spins bullets in super unnecessarily fast.

The 338 ARC & Spectre are smaller capacities helping them out in the sub category for velocity consistency.

Hornady runs the 8 twist and their 307 gr bullets rather blunt. But if the 307 gr works exceptionally well and fairly cheap plus available in factory loading.
I wouldn't hesitate to get the 8 twist, as it will be better for light supers...and cast lead bullets like the 300 blackout.

Here is the 300 Berger and 350 Maker. Note the bullet box is 338 Spectre 6.5 twist, both easily stablize in the 6.5 twist.
The 338 ARC and 338 Spectre are very similar as pictured with the longest bullet being a 350 gr Maker.
The 350 gr Maker modified to bore rider has no trouble stabilizing as shown here in the 6.5 twist 338 Spectre.
The 6.5 twist 165 gr Maker Super is made for supers to 2100 fps and 6.5 twist specifically so they don't come apart.

I don't plan on hunting with any of them, so it's up to the individual to decide. I just test and shoot them for fun.

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Do the 350gr Makers actually fit in a magazine (STANAG or ICAR pattern)?

JR1200W3 said:

From my experience, I think a 1:5" may be necessary for non-spitzer, solid subs that have a more forward COG. And I say this from a perspective of experience at 7000ft asl. Someone at sea level would benefit even greater from a faster twist.

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I shoot these at 1200 to 1500 feet evevation with no problem with the longer match bullets or the solid copper, with the 6.5 twist. I could shoot em at sea level or 10,000 feet, but I ain't gonna climb a mountain, about 60 miles away, or the ocean about the same distance, and a couple of hundred feet in elevation is easy, the shooting range is at 240 ft.

No actual need at all for a 5 twist, or the 3 twist, unless you want one of those twists, then get one...but it's not necessary to stablize any bullet from 160 gr Barnes to 350 Maker which even stabilizes at 800 fps at 1200 ft elevation.

45-90 said:

I shoot these at 1200 to 1500 feet evevation with no problem with the longer match bullets or the solid copper, with the 6.5 twist. I could shoot em at sea level or 10,000 feet, but I ain't gonna climb a mountain, about 60 miles away, or the ocean about the same distance, and a couple of hundred feet in elevation is easy, the shooting range is at 240 ft.

No actual need at all for a 5 twist, or the 3 twist, unless you want one of those twists, then get one...but it's not necessary to stablize any bullet from 160 gr Barnes to 350 Maker which even stabilizes at 800 fps at 1200 ft elevation.

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Totally disagree. You're experience is a data point of one. My experience has been different. Regardless of how much you're going to post, it's not going to change what I've seen.

You don't need to try to be the definitive voice and stifle others. Say your piece and be done. Let others decide for themselves.

JR1200W3 said:

Totally disagree. You're experience is a data point of one. My experience has been different. Regardless of how much you're going to post, it's not going to change what I've seen.

You don't need to try to be the definitive voice and stifle others. Say your piece and be done. Let others decide for themselves.

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No strife, when I say "get a 3 twist or 5 twist if you want one"....but it's not needed.

You are welcome to your opinion, as is anyone.
Hornaday has an opinion too.. with lots of test data, and deep pockets to develope the 338 ARC ....they chose the 8 twist for the 338 ARC.
It will most likely stablize most any reasonable bullet from 160 gr to 300 grs...or maybe just their 307 gr.
I haven't tested it yet....but the majority of barrel makers are following suit with 8 twist as standard for the 338 ARC...including Faxon who touts the 3 twist for the 8.6 and Hornady engineers called it "ridiculous". And I tend to agree after owning the 3 twist.....but that doesn’t mean you shouldn't own a 3 twist, 5 twist, etc, or even promote it for your purpose, if it's a good fit for your personal shooting endeavors.

I have lots of data on 3 twist and 6.5 twist...not just one or limited to one caliber.

The 6.5 twist has really worked well for me in 2 calibers, being very versatile and more accurate and consistent.
Some of that do to the poor Faxon quality, especially of their first barrels...lots of complaints, and bullet blow-ups destroyed muzzle devices and chronographs...lots of warnings put down in these pages.

No strife, get whatever twist you like for whatever caliber you like. No one cares what you decide.
Freedom of lots of choices is good...and so is freedom to experiment, & express opinions.
But manufacturers also "sell"...to get you to "buy.".. their products over the next manufacturers, as better, newly designed, the future, etc.and most everyone buys into the propaganda, a few work almost as stated, but many do not.
So get what you want, report on it...see if it's up to your expectations.

PBWalsh said:

Do the 350gr Makers actually fit in a magazine (STANAG or ICAR pattern)?

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This has all been discussed in other pages...
The 350 gr Maker is alot of bullet for the 338 Spectre and 338 ARC.

I have used cut out mags to get it to work but velocity was low in the 850 fps area, needed a different powder but it's a compressed load...but about 900 fps would seem the velocity limit with out further development, and experimentation.

I guy wanted a .416/ 338 Spectre developed, and was not concerned about AR 15 mag length as it was for a bolt gun.

So after machining bullets to 402 gr complete with holllow point. I fit it into a 338 Spectre case to decide how much powder space was needed to get it to 1100 fps. This was achieved with bore riders.

So I used the same concept on the 338 Spectre and machined different bullets. Then went to the 350 gr Maker to modify it to gain more powder space, and had 2 solutions, one being the long bore rider.
Easy to make in a precision lathe with collets.
But it was single load in an AR 15 but work great in a bolt gun.
That's alot of bullet, but its accurate and consistent to run right to the edge of subsonic/ supersonic flight, another .5 gr runs 1047 fps in the AR 15 single load these.

Talk about Fat...The 510 Whisper with a 750 Atip or also available are the 900 gr and 1000 gr bullets.
Here is a pic of the 510 whisper 750 Atip and the 8.6 Blackout with a 350 gr Maker.

nikonNUT said:

I will add that, just for shits and giggles, I would love to see the .338 285gr. ELD-M crammed in one of those itty bitty cases. Guessing it would be waaayyyy to long!

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A 350 Maker in both 338 Spectre and 338 ARC.

After owning and shooting the 338 Spectre, 8.6 blkout 3 twist and 6.5 twist.

The 8.6 3 twist is a dud, and dangerous, limited to low subs and expensive copper only bullets.
With the 6.5 twist, a bolt gun, and hybrid cases its basically a 338 Federal fir supers and better with subs.
No velocity limits of 1000 fps on 350 Makers. I ran them over 1800 fps in the 6.5 twist, no blow ups.

Might as well try the 338 ARC,...but not Hornadys version...something with a faster twist, and maybe just a bit more case capacity like the difference between a 6 Dasher and 6 BR for supers but subs remain about the same, cause the long bullets take up the extra case capacity.

So I did alot of testing with the 338 ARC improved with bullets 160 gr Barnes 2300 fps, 165 Maker 2275 fps, 175 HP 2202 fps, 200 gr Speer 2100 fps, 200 gr SST 2025 fps
250 gr RN 1760 fps, 272 fmj, 300 SMK, 300 ATIP, and 350 Maker, standad bullet 866 fps and 350 gr bore rider over 1200 fps in 6.5 twist 338 ARC improved...200 fps faster than a AR 10, 8.6 blakout with the 3 twist and its 1000 fps speed limit for this bullet.
So here one can shoot a 16" 338 ARC improved 6.5 twist using an AR 15 with no limits on bullet selection or makeup, and hang with the 12" AR 10, 3 twist in 8.6 blackout, ...and shoot jacketed lead much faster with no speed limits.

45-90 said:

After owning and shooting the 338 Spectre, 8.6 blkout 3 twist and 6.5 twist.

The 8.6 3 twist is a dud, and dangerous, limited to low subs and expensive copper only bullets.
With the 6.5 twist, a bolt gun, and hybrid cases its basically a 338 Federal fir supers and better with subs.
No velocity limits of 1000 fps on 350 Makers. I ran them over 1800 fps in the 6.5 twist, no blow ups.

Might as well try the 338 ARC,...but not Hornadys version...something with a faster twist, and maybe just a bit more case capacity like the difference between a 6 Dasher and 6 BR for supers but subs remain about the same, cause the long bullets take up the extra case capacity.

So I did alot of testing with the 338 ARC improved with bullets 160 gr Barnes 2300 fps, 165 Maker 2275 fps, 175 HP 2202 fps, 200 gr Speer 2100 fps, 200 gr SST 2025 fps
250 gr RN 1760 fps, 272 fmj, 300 SMK, 300 ATIP, and 350 Maker, standad bullet 866 fps and 350 gr bore rider over 1200 fps in 6.5 twist 338 ARC improved...200 fps faster than a AR 10, 8.6 blakout with the 3 twist and its 1000 fps speed limit for this bullet.
So here one can shoot a 16" 338 ARC improved 6.5 twist using an AR 15 with no limits on bullet selection or makeup, and hang with the 12" AR 10, 3 twist in 8.6 blackout, ...and shoot jacketed lead much faster with no speed limits.

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How does your 338 ARC Improved feed?

mig1nc said:

How does your 338 ARC Improved feed?

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100% on everything 160 gr to 350 gr with CMMG designated 338 ARC mags. Even these blunt round nose bullets.
This is the 338 ARC or 338 ARC improved mag...works great.

I took the 347 weighed 350 gr Maker and turned a few down to 1.870" and only took off 7 grs of copper, or 340 gr. To get more capacity over the 347 gr ran 3 over the chronograph, a 4 th was over 1000 fps at 330 grs.
This is a 6.5 twist in 338 ARC imp but the bullet takes up all the extra space...
It could be just a bit more like only 25 fps but you're basically at max with slightly modified 350 Maker at mag length.
The one modified to 330 gr had over 1000 fps.
So with the 338 ARC one may be limited to 340 gr and 300 gr. Or just stick with the factory 300 gr. The 6.5 twist rate seemed to stablize them, but will they open up at the lower velocity with out cut out mags and making the bullets bore riders.

I ran the shorter 1.295" ARC cases fireformed, they are shorter than the 1.370" ARC starline improved cases.
The velocity is down a bit, but faster than factory loads.
The velocites were consistent with the supers, 200 gr at 2050 fps &175 gr at close to 2200 fps.
The barrel likes the 175 gr which were 2nds and free shipping for 35 cents each...they are 2nds but shoot good.
Four went into one enlarged hole, and one off to the side.
Put up a new target and fired 30 rds.
A fun day out shooting, but it's starting to get hot.

FWIW... Palmetto State Armory / AAC now sells their own brand 338 ARC ammo.

300gr OTM

175gr OTM

The world's fastest 338 ARC ....3760 fps! In 16" 6.5 twist 338 ARC imp.

Just messing around, try to get the supers going a bit faster...so improved the case.
That helped, then decided to go to the extreme, because I can.
Machined a few light hollow point bullets.
Let's see how fast they will go.

Then how worthless is this endevor?
Shot some one liter jugs, the light bullets violently explode the first one liter jug and only a small fragment enters the 2nd jug.

Not much penetration, as kind of expected.
It would totally destroy a rabbit, so it would be a good close range varmint round for things ya don't want to eat.

Shot 3 at 50 yds, cause it's a close range round...it has potential to be decent for a particular narrow range of uses.

Imagine that in CQB to the chest and face.

Megacanoe to the head it would do....

With that much bore volume, I bet it would still be cooking with a shorty, 9-10.5" barrel.

mig1nc said:

With that much bore volume, I bet it would still be cooking with a shorty, 9-10.5" barrel.

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About 3350 to 3400 fps in a 10" barrel.

Light weight bullets for a given caliber lose more velocity when it comes to barrel length per inch than heavy bullets.

But yes it's still way above anything that would be called "standard" for a 338 ARC, at 2070 fps for a super factory round in a 16" barrel.

45-90 said:

About 3350 to 3400 fps in a 10" barrel.

Light weight bullets for a given caliber lose more velocity when it comes to barrel length per inch than heavy bullets.

But yes it's still way above anything that would be called "standard" for a 338 ARC, at 2070 fps for a super factory round in a 16" barrel.

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How light would you have to make the bullet to get it to say, 2200 from a 10" barrel?

mig1nc said:

How light would you have to make the bullet to get it to say, 2200 from a 10" barrel?

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Here's the bullet and the "Max load" (work up) data for all copper bullet 115 gr in a 10" barrel.
It appears Lil Gun will do the job easily, at 2300 fps might get up to 125 gr depending on barrel, chamber etc.
The bullet is a heavier copper .338 bullet cut down and champhered to make 115 gr.
No bullets on the marked this light ya have to make your own.
And no, I do not make bullets for others.
It's not hard to do but a lathe with collets does a nice job.

Hammer released a 128gr .338 mono recently for anyone interested.

CA48 said:

Hammer released a 128gr .338 mono recently for anyone interested.

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That is a factory bullet that just might get ya there in 338 ARC at 2200 fps in a 10" barrel. COAL 2.0" 23.8 GR LILGUN MAX 2213 FPS.
BUT ITS MADE FOR 338 FEDERAL TO GET 3000 FPS.
And lots of drawbacks like $1.40 ea. Really poor BC at .213 g1 estimated.
Most likely won't preform past 100yds because velocity will fall off fast for hunting purposes as it was designed for 3000 fps

A better hunting bullet for the 338 ARC would be the bullet designed for the Spectre by Maker is the high velocity 165 gr. Has an upper limit of 2100 fps and will expand at low velocity, designed for a 6.5 twist, so it'd work in an 8 twist 338 ARC.
I've shot it in the 338 Spectre and 338 ARC imp.
Here is the load in the 338 Spectre 165 gr with LilGun, but a 16" barrel.
Same 165 gr bullet in my 338 ARC improved is going almost 2300 fps.
And the 175 gr HPs are going a bit over 2200 fps instead of the factory 2070 fps in 16" barrels.
The reason for the 338 ARC improved was to add a little velocity to the anemic performance of supers in the 338 ARC, but retain the same performance with subs.

Don't do much good to post 338 ARC improved data as the case has a bit more capacity, and some will not follow directions and over pressure the standard case. So if you must take at least 2 grains out of the 338 ARC improved recipe for the standard 338 ARC in supers ...subs will be very close casuse the long bullets take up do much powder space.

Most of the cut down rifle bullets in copper are made for higher velocity rounds, expansion stops at 1800 to 2000 fps in most cases..leaving little range increase with supers.
Maker machines them for low capacity rounds and have saw cuts down the side for expansion down to 900 fps...giving more real killing range to the sub gun cartridges, plus much less expensive than the Hammer bullets...
But you'll have to test them for yourself to find out where you lose expansion.
Or maybe ya just want more velocity.
The more information the better, to help those interested, make a decision right for them.

Caution...
This is all for 338 ARC IMP with 16" barrel.

Don't leave your SBR 6.5 Grendel out with a 43.8 gr bullet for your high velocity varmint load ...not available in any store.
Some folks have too much play time & machine tools for their hobby.