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Posted: 7/12/2026 4:25:26 PM EDT
[Last Edit: bendigo78][Edited]
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Couldn't find anyone doing load development for the 338arc for subs in pistol length barrel, so I'm dropping my info here. Been playing with a BCA bolt action receiver in a pistol set up with folding brace to prove a "pocket sniper" concept. Ended up at 338 ARC via a 9" faxon 1-5 barrel and faxon grendel bolt. I plan on using it for subsonic shooting only. 300gn SMK 2.250oal 100yd H110 - 11.4 1051.9 fps - Most accurate 1-1/4" Lil Gun - 10.5 1038.7 fps - Second most accurate 2" CfeBLK - 15.4 1060.9 - 4" AA1680 - 14.5 1041.4 - 2-4" SP3 - 12.1 1067.3 - 4 1/2" Titegroup - 7.0 900fps - didn't group it. Max load. Any hotter and primers get flat. At 8.8 (1025fps) I ruined a piece of brass with ejector swipe. 300gn Makers REX bullet H110 - 11.4 1059.9fps -1 1/2" 250gn SMK 2.254 (barrel didn't seem to like them so no accuracy data) Lil Gun - 10.2 1044.2fps AA1680 - 14.8 1058.6fps Titegroup - 7.5 1064.9fps ES of 7, SD of 2.5. - 4" Love how quiet titegroup loads are and the ES is ridiculous. It's not going to cycle a semi. I bet they'd group in a 1-8 barrel. |
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I asked the guy at Makers - can't remember his name ATM - he gave me his load for his 300gr bullets. He likes Lil Gun IIRC. I'll have to check when I get home. FYI this is data for a .338 Spectre, but I can't see there being a whole lot of difference. |
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Originally Posted By fortydelta: I asked the guy at Makers - can't remember his name ATM - he gave me his load for his 300gr bullets. He likes Lil Gun IIRC. I'll have to check when I get home. FYI this is data for a .338 Spectre, but I can't see there being a whole lot of difference. Its gotta be close to the lilgun load with the SMK. I didnt see much velocity difference between the two bullets. I would be interested in his oal. |
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Add some chrono pics Attached File Attached File Attached File Attached File Attached File |
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300grns Attached File |
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Ran the 300grn makers into some water jugs. Where as the 180grn 308s made it through 3 and stuck in the 4th, these made it through 5 and stuck in the 6th. Kinda a pain to catch. Some came out the sides and bounced off the target plywood. Also found some that came off of steel. Attached File Attached File |
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Originally Posted By bendigo78: Couldn't find anyone doing load development for the 338arc for subs in pistol length barrel, so I'm dropping my info here. Been playing with a BCA bolt action receiver in a pistol set up with folding brace to prove a "pocket sniper" concept. Ended up at 338 ARC via a 9" faxon 1-5 barrel and faxon grendel bolt. I plan on using it for subsonic shooting only. 300gn SMK 2.250oal 100yd H110 - 11.4 1051.9 fps - Most accurate 1-1/4" Lil Gun - 10.5 1038.7 fps - Second most accurate 2" CfeBLK - 15.4 1060.9 - 4" AA1680 - 14.5 1041.4 - 2-4" SP3 - 12.1 1067.3 - 4 1/2" Titegroup - 7.0 900fps - didn't group it. Max load. Any hotter and primers get flat. At 8.8 (1025fps) I ruined a piece of brass with ejector swipe. 300gn Makers REX bullet H110 - 11.4 1059.9fps -1 1/2" 250gn SMK 2.254 (barrel didn't seem to like them so no accuracy data) Lil Gun - 10.2 1044.2fps AA1680 - 14.8 1058.6fps Titegroup - 7.5 1064.9fps ES of 7, SD of 2.5. - 4" Love how quiet titegroup loads are and the ES is ridiculous. It's not going to cycle a semi. I bet they'd group in a 1-8 barrel. Thanks for the info. I would like to try this cartridge at some point. Did you chop your bolt carrier, to achieve the ability to use a folding stock? I considered rolling the dice on one, but didnt like the fact that the bolt had to travel into the buffer tube due to length. |
| I've been working on getting the 300grn hornady Atips to work to no avail. They are too long and don't have enough space for powder. Got to 1050 with H110 but put some pretty good donuts in the bullets smashing them in there. Then I thought they might be the perfect candidate for a titegroup load but nope they were way too hot. At 850fps the pressure ruined a case with ejector swipe. |
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Got a care package from a buddy at hornady. So here's some subx 307grn h110 loads and velocity. Attached File 11.4grns of H110 and 307subx Attached File 11.6grns got them up too 1047fps |
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Originally Posted By bendigo78: Got a care package from a buddy at hornady. So here's some subx 307grn h110 loads and velocity. https://www.ar15.com/media/mediaFiles/26018/19492_jpg-3819650.JPG 11.4grns of H110 and 307subx https://www.ar15.com/media/mediaFiles/26018/19563_jpg-3819651.JPG 11.6grns got them up too 1047fps You need to introduce me to your buddy! Attached File |
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Originally Posted By bluedog82: You need to introduce me to your buddy! https://www.ar15.com/media/mediaFiles/499242/IMG_2076_jpeg-3819664.JPG If there's a reason this caliber doesn't go anywhere it'll be cost. Blem smks are $.50. 307gn Subx are $1 each shipped. Maker Rex 300gn $2 each shipped. Brass is $1 each shipped. Decided I couldn't live without a semiautomatic version and ordered the 8.5" psa upper and put it on a hbpdw braced lower. Pretty damn impressed with it. Has cycled 100%. Subsonic recoil impulse is sick. Accuracy is not bad. Probably 3" a 100. Has funny flyers that make an identical group 2" to the right. I should shim it and see if that helps. |
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Originally Posted By bendigo78: If there's a reason this caliber doesn't go anywhere it'll be cost. Blem smks are $.50. 307gn Subx are $1 each shipped. Maker Rex 300gn $2 each shipped. Brass is $1 each shipped. Decided I couldn't live without a semiautomatic version and ordered the 8.5" psa upper and put it on a hbpdw braced lower. Pretty damn impressed with it. Has cycled 100%. Subsonic recoil impulse is sick. Accuracy is not bad. Probably 3" a 100. Has funny flyers that make an identical group 2" to the right. I should shim it and see if that helps. Yeah it is not a plinking caliber. Thanks for all the info you have posted. |
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Figure I'd add some load data from the PSA 8.5" 1-8 semi auto upper day of shooting. Wrote it down so might as well document it. 307gn SubX hornady ammo 1070fps ES 15.3 SD 5.8 opened up to 2" with one flyer. 300SMK H110 11.4gn 2.255 oal 1041.2fps ES 20 SD 6.4 2" 307SubX H110 11.4gn 2.255 oal 1047.5fps ES 18.2 SD 6.2 3" with two flyers (resembling 2 separate groups one left the other straight right) 307SubX H110 11.6gn 2.255 oal 1069.5fps ES 27.1 SD 10 3" with two flyers (resembling 2 separate groups one left the other straight right) Had a stout left to right wind during shooting but I'll shim the barrel anyway. Upper was $399 from PSA. Which is a bit higher than their typical pistol uppers but it comes with a 338arc mag and has an adjustable gas block installed. Comes with an extended allen key for adjustments. Upper has been perfect in function with a Hybrid 46 with a 9mm endcap on a PSA lower with HBpdw brace and larue MBT. Ejection is about 5 oclock but locks on empty every time. Most likely due to the small buffer and spring in the honey badger brace. I won't mess with it until there's an issue. With the 1-8 twist, I'm going to revisit the 250SMK sub loads for accuracy testing. Attached File Attached File |
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Got the bca bolt action 9" faxon out today. Tested the 11.4 and 11.6 loads Attached File Attached File The 307subx 11.6 grn load group. Attached File |
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307 sub x and 11.8 gns of H110 didn't group as well as hoped. Also remembered that I'd taken a 250gn smk load with me to the range and forgot to shoot them. Attached File Attached File |
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Not crapping in this thread... Just trying to be helpful. I've got no experience with LilGun in this specific application...therefore, my input might be total horseshit . With that said, I used a fair bit of LilGun in max velocity .357 Mag carbine loads. Got some impressive speeds, putting 158 gr SP bullets into original 160 gr 30 WCF territory. Unfortunately, there was a catch: the powder burned FAR hotter than anything else I've experienced. I doubt there could be much immediate harm from slow measured fire. However, based on my experience, I'd have serious reservations about firing 5, 10, or more LilGun loads in quick succession. I fully suspect reduced barrel life as a minimum. Freedom Arms made excellent revolvers. They specifically warned against LilGun. Extreme forcing cone erosion extreme flame cutting, to mention just two issues . Again, not intending any flames here. Just trying to help prevent a possible undesired outcome. Proceed carefully. |
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Originally Posted By frozenny: Not crapping in this thread... Just trying to be helpful. I've got no experience with LilGun in this specific application...therefore, my input might be total horseshit . With that said, I used a fair bit of LilGun in max velocity .357 Mag carbine loads. Got some impressive speeds, putting 158 gr SP bullets into original 160 gr 30 WCF territory. Unfortunately, there was a catch: the powder burned FAR hotter than anything else I've experienced. I doubt there could be much immediate harm from slow measured fire. However, based on my experience, I'd have serious reservations about firing 5, 10, or more LilGun loads in quick succession. I fully suspect reduced barrel life as a minimum. Freedom Arms made excellent revolvers. They specifically warned against LilGun. Extreme forcing cone erosion extreme flame cutting, to mention just two issues . Again, not intending any flames here. Just trying to help prevent a possible undesired outcome. Proceed carefully. Lil gun sits right next to h110 and w296 on the burn chart which is 50 spots behind titegroup. I love some titegroup subsonic loads but its too fast for 300gn bullets in this, 250s seem ok. All these loads are subsonic and at 10gns it's probably close to half of what your 357 loads were. Lilgun came in second place behind H110 for accuracy so I haven't used it since starting load development. |
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