390 grain Hornady A-Tip load development 375 Cheytac
- Thread starter secondofangle2
- Start date
Few bushing does available so I doubt most know. I just FL size mine on Viersco dies and roll
They’ve stayed together at 2950 out of our 8s
3050 fps in a 1-7, banana peel at 100 on the 3rd shot at 100 during zeroing. We expected it but was worth a try hahaha.
George Gardner said it would be ok as long as I kept them under 2950
Follow up, we shot them today at 2800 fps in the 1-7. They held up w no issues.
I was able to get 3005 with RL50 .020” off the lands with new Peterson brass. Just slight pressure signs so I stopped there. Problems and pressure signs started with annealed and sized brass. I will probably have to settle with something in the 28-2850 range.
How much RL33 and how far off the lands were you when you hit 3050?
hi, Secondofangle2
I am currently designing a 375 subsonic cartridge based on the 308 brass.
So, I am looking for information on the 375A-tip 390grain, but currently the only place that has provided accurate dimensions is here on the forum. If you have time, could you please provide the length of the nose, boat tai and bearing surface?
Thank you very much.
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If I get around to it sure but I wonder why you would design a new cartridge for a bullet you can’t even get a single specimen of? 
I was able to find them a few months ago. I grabbed 500 of them, I could of got more but I'm not 100% commited to that bullet yet. gonna try some of the solids also.If I get around to it sure but I wonder why you would design a new cartridge for a bullet you can’t even get a single specimen of?
Yes, I will be loading high BC bullets over 350grain with 2.8" OAL. I ruled out berger's 379 and 407grain bullets because they are too long OAL. I think the 2.0375" A-tip will fit in the accurate mag which can accommodate up to 2.87" long.
Cool, what speeds did you get and what barrel length were you using?
With my old 375 CT I had a load using 138 grains of H50BMG and a 375 grain RMB projectile at 2945FPS. I’m wondering how far I have to back the charge off with the 395 grain ATIPS.
Stayed at 2950 with a 33” because we didn’t want to blow them up out of an 8 twist
I am using 133gr of AR2218 (H50BMG) with the 390gr Atips in my HTI 375ct....superb accuracy!
No, I was told, they would almost certain they would blow up so didn’t bother
Nice. Is that a DT factory barrel? How far off the lands are you seating the ATIPs and what powder are you using?
Yep...Factory DT 1 in 10.5 twist barrel. Velocity around 2900fps..
Initially tried the 352CE with my 375ct which is supposedly what Desert Tech use in their factory ammo. Results were shockingly bad!! 1-1.5 moa!!! Nothing i tried would improve the accuracy using these projectiles. I amost gave up with my 375ct and then decided to try the Atips......best thing i could of done..
The 390 Atips shoot consistent 1/4 moa with my HTI...
Nice!!!
I am going to try H50BMG. RL50 was kind of all over the place in my gun.
What is your CBTOL and how far off the lands do you seat them?
Deer Geno.C,
thanks for the kind reply. However, since I am designing bullets to ultimately make bullets for use in an AR10 or AR308, I am going to limit the overall COAL to "2.8inch".
Below is the ammo I made in Pakistan about a year ago (before the Ukrainian war broke out). It was tested with a then modified lee-enfield and tested with a total barrel of 320mm (12.5inch). The poor brass, barrel quality and hand-made gun heat made the 100meter MOA was terrible(Perhaps there was a problem with the barrel twist rate.), but the bullet velocity and kinetic energy were quite satisfactory.
I myself use Bertram....but a good friend of mine is using Peterson with the same load in another DT HTI...
I did a pressure/ Satterly test today with H50BMG & Peterson Brass and RL50 and Bertram Brass ( found some I forgot I had).
Thank you for the H50BMG data, I think I have a node at 134-136 grains (2899-2925) that I can start to develop. I went all the way up to 138 (2991 FPS) grains and I saw no pressure signs at all.
@secondofangle2 that Bertram Brass made all the difference with the RL50 and the ATIPs. No pressure signs at 137 grains and 2918 FPS with my stock barrel. I may test 137.5 and work up a bit more in .5 grain increments next week to see if there are additional flat spots in the chronograph.
I loaded the ATIPS .010 off the lands for the testing. It seems they like less jump in my gun.
Thanks again
Do any of you A-Tip guys have leftover/excess Hornady red polishing bags that you'd be willing to part with?
I'm looking for some to replace the mesh bags on my brass catchers. I contacted Hornady and they are not offering the bag by itself.
I'd be willing to pay postage or make a commensurate donation to the 'Hide [I'm sure Lowlight would appreciate some extra Christmas cheer this time of year].
Thanks for your considering my request,
steveH
I'm looking for some to replace the mesh bags on my brass catchers. I contacted Hornady and they are not offering the bag by itself.
I'd be willing to pay postage or make a commensurate donation to the 'Hide [I'm sure Lowlight would appreciate some extra Christmas cheer this time of year].
Thanks for your considering my request,
steveH
Seems like with Peterson Brass and H50BMG my gun likes 134 & 136 grains. Both groups are 1/3 MOA maybe 1/4 with the 137 grain load. The ES on the 137 grain load is about 11 fps. Problem with the 137 grain load is I start to get very slight pressure signs. Ave velocity is 2916 with 134 grains and 2966 with 137.
I went up to 139 grains of RL50 and Bertram Brass and did not see any pressure signs.
For some odd reason the H50BMG and Peterson brass seem to like .010” jump. Bertram & RL50 not so much. I think I’ll try deeper seating depths this Friday if I can make it out to the range.
