375 Raptor Load Data

[Konrad.INc]

Evening All,

I made the decision to build a 375 Raptor a few weeks ago and thought I would share some interesting load data. This data is just what I found, and not to be taken as gospel. All were fired from a 13” Barrel AR-10 pistol, barrel is a SS Brux 1-10 twist. Barrel has a carbine length gas system and a .073” gas port. Cases were some ancient heavily used Lapua 308 that I necked down in one stroke through a 375 Raptor FL die, then trimmed to 1.860”

Load 1:
270 gr Barnes LRX
2.790” OAL
36Gr H335 (37gr shows ejector marks/excessive pressure)
1695fps avg

Load 2:
235gr Speer HotCore
2.660” OAL
36Gr H335
1700fps avg

Load 3:
270gr Barnes LRX
2.790” OAL
30gr H335
1425fps

Load 4:
300gr Barnes TSX
2.722” OAL
30gr H335
1341fps

I’ll post more load data once I have it. My goal is to download 300gr plus bullets to subsonic. H335 seems to be too fine grain/ball powder to do this as the load densities become very small when downloading that far. My next test will hopefully be with 4895 as that will be larger kernels to improve load density. I’d love to fine some IMR3031 but I’m not paying 68$ a pound at Bi-Mart. The pistol cycled fine with all loads with a pistol buffer system.

 

[Maximus1840]

Thanks for posting. I just ordered parts for a 375 raptor build

 

[spaniel]

Just submitted my Form 1 on my action to build one...thanks.

 

[Fire Dog]

Evening All,

I made the decision to build a 375 Raptor a few weeks ago and thought I would share some interesting load data. This data is just what I found, and not to be taken as gospel. All were fired from a 13” Barrel AR-10 pistol, barrel is a SS Brux 1-10 twist. Barrel has a carbine length gas system and a .073” gas port. Cases were some ancient heavily used Lapua 308 that I necked down in one stroke through a 375 Raptor FL die, then trimmed to 1.860”

Load 1:
270 gr Barnes LRX
2.790” OAL
36Gr H335 (37gr shows ejector marks/excessive pressure)
1695fps avg

Load 2:
235gr Speer HotCore
2.660” OAL
36Gr H335
1700fps avg

Load 3:
270gr Barnes LRX
2.790” OAL
30gr H335
1425fps

Load 4:
300gr Barnes TSX
2.722” OAL
30gr H335
1341fps

I’ll post more load data once I have it. My goal is to download 300gr plus bullets to subsonic. H335 seems to be too fine grain/ball powder to do this as the load densities become very small when downloading that far. My next test will hopefully be with 4895 as that will be larger kernels to improve load density. I’d love to fine some IMR3031 but I’m not paying 68$ a pound at Bi-Mart. The pistol cycled fine with all loads with a pistol buffer system.

Hodg0n Benchmark is the the equivalent to IMR3031… Perhaps you can find that a bit cheaper..?
H4895 will be just a bit just a tad slower than the H335

 

[Konrad.INc]

My form 1 was approved in 1 day! After that, I switched to a UBR gen 2 buttstock with an H3 carbine buffer system and AR-10 carbine spring. Here’s one more follow up load datapoint.

10gr WST
300gr Barnes TSX
2.750” OAL (previous OALs seem a little long)
525-540fps
It didn’t even attempt to cycle at this low of pressure. Primers were pretty flat, so I’ll try going up a little bit but this may be too fast of burn rate powder.

 

[Konrad.INc]

More load data results.

12gr WST
300Gr Barnes TSX
2.750" OAL
600-950FPS - Bolt still didnt even attempt to unlock/cycle, erratic velocity, probably from inconsistent ignition.

14gr WST
300Gr Barnes TSX
2.750" OAL
1070FPS - Bolt did not unlock on 3/5 rounds, the other 2 short stroke/stovepipe jam. This powder is just too fast burning and not enough gas volume to cycle correctly and still stay subsonic. Primers looked better here than at 10 or 12gr so this may be the safe minimum for consistent ignition.

17Gr H335
300Gr Barnes TSX
2.750" OAL
appx700 FPS - Erratic ignition/velocity, bolt would just barely unlock but not open.

19.5Gr H335
300Gr Barnes TSX
2.750" OAL
760 FPS - Bolt will unlock and open partially but not far enough to pick up another round from the mag.

21.3 Gr H335
300Gr Barnes TSX
2.750" OAL
870FPS - Bolt cycles enough to reliably chamber another round out of the mag but not far enough to lock the bolt back on an empty mag.

Still waiting on the 350gr bullets to show up. Looks like appx 23gr H335 would be a good subsonic load with the 300gr Barnes TSX with enough gas volume to cycle the action. I'm guessing a slightly faster powder would also be acceptable, I might try something like CFEBLK or similar to see if there is still enough gas volume to cycle correctly and still give reasonable subsonic velocities.

 

[Konrad.INc]

OK, More load data. Velocities listed are 5 shot averages

22gr H335
270gr Barnes LRX
944FPS - bolt did not lock back but would chamber a round from the mag.

23gr H335
270gr Barnes LEX
985FPS - bolt did not lock back but would chamber a round from the mag.

23gr H335
300gr Barnes TSX
1004fps - bolt did not lock back but would chamber a round from the mag.

24gr H335
300gr Barnes TSX
1051fps - bolt did not lock back reliably but would chamber a round from the mag. A couple of times it did lock back properly so this is close, maybe a lighter buffer or a different powder would help. I'll try a couple more powders both faster and slower to see if that helps. Faster being CFE BLK and slower being SW Match Rifle and Varget.

350gr SMKs should be here around the end of the week so well see how that changes things. It was interesting seeing the 270LRX go slower than the 300gr TSX at the same powder charge. The velocity difference was consistent on each shot as well, not just one or two shots lowering the average. All powder thrown with an autotrickler as well.

 

[Konrad.INc]

350 gr SMKs work fine at mag length in the 375 Raptor, the ogive is still in front of the case mouth.

23gr H335
350gr SMK @2.780"
1051 fps avg

24gr H335
350gr SMK @ 2.780"
1107 fps avg

Neither of these loads would completely cycle the action or lock the bolt back, so, time to try different powders.