Hornady Sub-X 255gr for .303?
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Category: Reloading
Forum Name: Reloading .303 British
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Printed Date: March 26 2026 at 7:10pm
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Topic: Hornady Sub-X 255gr for .303?
Posted By: Kris308
Subject: Hornady Sub-X 255gr for .303?
Date Posted: April 22 2024 at 2:15am
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he!!o, I have noticed Hornady now produce a 255 grain Sub-X bullet for 7.62x39. Its diameter is .3115". I was wondering if this would shoot in .303?. Does anyone have any thoughts on this or have actually tried it?. I have emailed Hornady asking the question. My thoughts were accuracy may suffer due to the barrel twist rate being 1:10 and couldn't see any bullets being shot over about 215grains for .303. However the most common twist rates in 7.62x39 seem to be 1:9.5 which it pretty close. Now I'm not sure if barrel length or the fact that its a sub-sonic load will have an effect on the accuracy if fired through our N01 MK3 or N04 MK 1/2 rifles. If anyone has tried this I would be interested to know if anyone has any load data for it. I'm guessing it would be similar to the .308 loads using a 190gr Sub-X. This data uses H4895, H322 and Trailboss which are unfortunately not available here in the UK anymore. What powders would be equivalent for such sub-sonic loads in the UK?.
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Replies:
Posted By: Shamu
Date Posted: April 22 2024 at 12:57pm
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As long as your bore is good then you can happily shoot .3115" bullets in it. I've been doing it for years! Bullet weight & shape & stabilization is a whole different ball game. I have a couple of boxes of heavy .311 bullets I'll probably never use, but if you want to do a basic check before committing I can pack a few samples for you to mess about with for a "prototype run" I have 200Gr FMJ rebated BT From Lapua & 215 Gr .311 RN-FB "Woodliegh" bullets. Let me know how this will stack up, legally importing into the U,K.  I think FMJ wasn't regulated? but SP was as a "hunting bullet"? I have some heavy bullet load data,up to 215Gt IIRC, but its for American powders, maybe you can translate?
------------- Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force) |
Posted By: Kris308
Date Posted: April 22 2024 at 1:17pm
| That's incredibly kind of you to make such an offer. As a check I ran the data through the berger calcs for stability with a 1 in 10 twist. The 255 was stable if shot at about 1350fps and above. At 1100 fps (Sub sonic) speeds it ran slightly out of guaranteed stability but only effected bc by about 3%. I want this as a hunting bullet for a new rifle I'm having made in .303. As this will be a 100 yard stalking rifle I figure it will work. I would also like to try it in my n04 mk2 1954 Fazakerley which is as new never shot. Regarding powders I will need a fast burning pistol powder to prevent potential detonation as I don't want to use fillers. I'm looking at Unique or Red /green dot. When I look at what data is available in cast bullet loading manuals. The heaviest bullet shown is 210 grain. It used between 10 and 14grains. I figure if I used about 12 grains as a starting load and chromo it. I can then work back to subsonic speeds and see how it groups. I did get an email back from Hornady but they couldn't tell me anything. |
Posted By: britrifles
Date Posted: April 22 2024 at 2:00pm
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255 gr must be a long bullet. If you seat it to magazine length, a lot of that will be stuffed in the case which increases pressures. You will have to improvise on powder charge weights as I don’t know if you will be able to find load data for it. .311 diameter bullets shoot just fine in a LE. I shot about 10,000 Sierra 174 grain .311 diameter MatchKings from one of my No. 4 rifles with exceptional accuracy.
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Posted By: Sapper740
Date Posted: April 22 2024 at 2:02pm
| Yes, you could load those Sub X bullets into a .303 British but I don't know why anyone would want to. Those bullets are designed for reliable expansion at sub-sonic velocities so I imagine they would suffer near explosive expansion at the velocities a Lee Enfield could push them to. Lots of damaged meat if used for hunting. Next, I can only imagine what their mid-range trajectory is when shooting at longer ranges making them unsuitable for target loads. There probably isn't enough adjustment in micrometer peep sights to shoot much beyond 400 or 500 yards I'd wager. |
Posted By: Kris308
Date Posted: April 22 2024 at 2:09pm
| Yes they are 40mm long. Which is good because it takes up case capacity. I would only want to use about 12 grains of pistol powder to use them as a sub sonic load. I want them for my new single shot stalking rifle. This would be a 100 yard rifle, hence the subsonic desire and no requirement for hunting beyond this range. They still perform well however at higher velocities too. |
Posted By: Mayhem
Date Posted: April 22 2024 at 4:41pm
Getting them out of the US will be the first problem. The US is currently prohibiting the export of anything that can be used in a conflict without the necessary permits. I tried to get some NUPE brass out and a fellow collector had some guys from the government show up at his door when he posted some once fired brass to his buddy in Poland. ------------- .303 - Helping Englishmen express their feelings since 1889 |
Shamu wrote:Posted By: Kris308
Date Posted: April 22 2024 at 10:18pm
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.303 - Helping Englishmen express their feelings since 1889
LOL brilliant this needs putting on a T Shirt.
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Posted By: doggo
Date Posted: September 12 2024 at 9:26pm
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Have just shot six rounds 0f Hornady 255grn SUB -X projectiles out of my P14 BSA model D? with straight bolt 303 British with new criterion barrel cut down to 22inch with 1:10 twist 5 grove CASE = PPU FL RESIZED trimmed to 2.210inch Primer = Winchester RL Powder = 37 grns AR2209 (H4350) Projectile Hornady 255grn Sub-X @.3115 OAL =3.028 inch Compressed Load as PPU cases are thicker fired first three tied to tree with string on trigger at target at 12 yards ceck cases all looked good fired next three free hand all good no key holeing showing up Primers still round on edges with slight flattering Cases grew to around 2.216 other wise look good Next i will try target out to 50 then 100 yards  ------------- EGB |
Posted By: Kris308
Date Posted: September 13 2024 at 12:07am
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Hi mate, Thanks for the reply and info. That's very interesting. I would love to know how it groups at 50 and 100 yards. How does it sound?. Is it quiet?. Good luck and thanks again. Kris.
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Posted By: Zed
Date Posted: September 13 2024 at 4:10am
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With 37 grains behind it; it's not going to leave the barrel sub sonic. I think it would pack quite a punch. Possibly a bit too much, depending on the size of your prey. ------------- It's nice to be important, but it's more important to be nice! |
Posted By: Shamu
Date Posted: September 13 2024 at 9:05am
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Wow that's an "elephant load"!  ------------- Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force) |
Posted By: doggo
Date Posted: September 15 2024 at 8:38pm
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Went to the range and fired at the 100m Wind =nil Weather = overcast 19 degC 303 British P14 22 inch barrel scoped 2-9 x42 Case PPU Necked sized and trimmed to 2.212inch Primer = Win LR Powder= AR2209 @ 37grains Projectile 255 Grn Sub-X @ .3115 OAL=3.030 inches Cronie at 12 feet Vel= 1920 to 1985  F/Secphoto of target enclosed first shot fouler in the 9 ring Noticed the forward screw was not tight when i got home and cleaned it ------------- EGB |