375/08 vs 375 raptor

[Alibiiv]

I downloaded the load data from the 375 Raptor website before it went down. There's a fair bit of info in there for 10x powder, which I figured could be at least a safe starting point. How was the recoil on the rifle without the brake? Or have you always shot it in this configuration?

My goal was a close range stomper, and a brake isn't something I'd prefer to put on it. But, it's a relatively light rifle overall. I expect all told it'll be 7-7.5 pounds but I'll have it when it gets back to me. I would rather not get too broken by recoil, so we'll see how it feels. In theory, muzzle energy shouldn't be that much higher than a 30/06 so recoil should be comparable.

I would like to caution you about the 10X load data. I used the 10X load data to load the Maker 250 grain T-Rex bullet. The load data listed from the Raptor site for the 250gr Game King was 44.4 grains of 10X. I started out using 41.0 grains of 10X as a starting load. The 41.0 grain load gave me a hard bolt lift. The pressure signs were too evident, I stopped with that one round. From there I dropped the load down to 38.5 grains of 10X and worked up from there. I could only get 2100fps out of the load. I found these velocities to not be what I was looking for; or... what was published. I haven't tried the load data for the .358 Winchester data as of yet. Perhaps I can get the velocity I am looking for with a different powder. If I could get up into the 2450-2600 fps velocities it would be what I am looking for. I am not certain that I can get this out of the cartridge. I would like to get this cartridge to work in this rifle, I've got quite a bit of time and about $2000 put into the build.

 

[marksman1941]

I would like to caution you about the 10X load data. I used the 10X load data to load the Maker 250 grain T-Rex bullet. The load data listed from the Raptor site for the 250gr Game King was 44.4 grains of 10X. I started out using 41.0 grains of 10X as a starting load. The 41.0 grain load gave me a hard bolt lift. The pressure signs were too evident, I stopped with that one round. From there I dropped the load down to 38.5 grains of 10X and worked up from there. I could only get 2100fps out of the load. I found these velocities to not be what I was looking for; or... what was published. I haven't tried the load data for the .358 Winchester data as of yet. Perhaps I can get the velocity I am looking for with a different powder. If I could get up into the 2450-2600 fps velocities it would be what I am looking for. I am not certain that I can get this out of the cartridge. I would like to get this cartridge to work in this rifle, I've got quite a bit of time and about $2000 put into the build.

I finally received my rifle back from JES reboring and started putting together reloads this morning. I was going to try 10x as my primary powder, so I'm glad you posted this. I'll drop my starting point a bit and see what happens. I'm trying 300gr partitions, 270gr Speer BTSP and 270gr Hornady SP.

I do know that sometimes all copper bullets build pressure differently. I wonder if the Maker bullet you were using has some different pressure characteristics than the gameking. Did you use 10x for anything else?

 

[ShadowAviator]

I finally received my rifle back from JES reboring and started putting together reloads this morning. I was going to try 10x as my primary powder, so I'm glad you posted this. I'll drop my starting point a bit and see what happens. I'm trying 300gr partitions, 270gr Speer BTSP and 270gr Hornady SP.

I do know that sometimes all copper bullets build pressure differently. I wonder if the Maker bullet you were using has some different pressure characteristics than the gameking. Did you use 10x for anything else?

Do NOT use the load data for a lead bullet with a copper bullet.

Copper bullets have higher engraving pressures and take up more case capacity than a similar weight lead bullet.

Sorry for the delay, I will post more when I get time this evening. I just wanted to post this real quick.

 

[marksman1941]

Do NOT use the load data for a lead bullet with a copper bullet.

Copper bullets have higher engraving pressures and take up more case capacity than a similar weight lead bullet.

Sorry for the delay, I will post more when I get time this evening. I just wanted to post this real quick.

Agreed. I think that's why alibiiv ran into pressure early on. Don't worry, I'm running regular bullets with the published load data and prepping a pressure ladder

 

[marksman1941]

Load testing went well. I used the Raptor data for RL10x, started low and built up.
I loaded one round every half grain from 38.5-43.0 under the 270 Hornady sp and 270 Speer btsp, and 38.5-40.5 under the 300gr oryx (thought I had partitions but they were the oryx). I never ran into excess pressure. Some light ejector marks at higher loads, but never a sticky bolt or flattened primer.

since I was testing pressure I measured velocity for each shot for the 270 btsp and 300 oryx. Didn't measure the 270 Hornady.

Rifle is a 20" bull barrel Remington 700 SPS bored from 308 to a 1:10" 375/308 by JES. Scoped it weighs 8.5 pounds.

8/3/24 - 80 F - 29.98 pressure - 55% humidity - 1900' elevation

270gr speer btsp -

38.5 - 2105
39.0 - 2147
39.5 - 2183
40.0 - 2202
40.5 - 2236
41.0 - 2212
41.5 - 2255
42.0 - 2284
42.5 - 2296
43.0 - 2307

300gr oryx -

38.5 - 2019
39.0 - 2032
39.5 - 2059
40.0 - 2072
40.5 - 2078

Based on this, I'm going to keep pushing the slightly lighter bullets. The 300 didn't gain velocity very fast. but it gained recoil. The 270 was more manageable, and at the top end of the pressure test it was pushing 3200 ftlbs of muzzle energy.

From what I've read the speer btsp is fairly soft. I may try one on a blacktail for kicks and giggles, and stick with the Hornady Spire Point for bear thwomping. I would love to snag some 260gr partitions, as those seem like they'd be the best option, but those seem to be unobtainable.

 

[ShadowAviator]

Load testing went well. I used the Raptor data for RL10x, started low and built up.
I loaded one round every half grain from 38.5-43.0 under the 270 Hornady sp and 270 Speer btsp, and 38.5-40.5 under the 300gr oryx (thought I had partitions but they were the oryx). I never ran into excess pressure. Some light ejector marks at higher loads, but never a sticky bolt or flattened primer.

since I was testing pressure I measured velocity for each shot for the 270 btsp and 300 oryx. Didn't measure the 270 Hornady.

Rifle is a 20" bull barrel Remington 700 SPS bored from 308 to a 1:10" 375/308 by JES. Scoped it weighs 8.5 pounds.

8/3/24 - 80 F - 29.98 pressure - 55% humidity - 1900' elevation

270gr speer btsp -

38.5 - 2105
39.0 - 2147
39.5 - 2183
40.0 - 2202
40.5 - 2236
41.0 - 2212
41.5 - 2255
42.0 - 2284
42.5 - 2296
43.0 - 2307

300gr oryx -

38.5 - 2019
39.0 - 2032
39.5 - 2059
40.0 - 2072
40.5 - 2078

Based on this, I'm going to keep pushing the slightly lighter bullets. The 300 didn't gain velocity very fast. but it gained recoil. The 270 was more manageable, and at the top end of the pressure test it was pushing 3200 ftlbs of muzzle energy.

From what I've read the speer btsp is fairly soft. I may try one on a blacktail for kicks and giggles, and stick with the Hornady Spire Point for bear thwomping. I would love to snag some 260gr partitions, as those seem like they'd be the best option, but those seem to be unobtainable.

That tracks with my data on the speers. With 43gr I was getting 2250ish with an 18" barrel.

I have some 235 speers that I need to try with faster powder. 10x seems slow.

 

[marksman1941]

That tracks with my data on the speers. With 43gr I was getting 2250ish with an 18" barrel.

I have some 235 speers that I need to try with faster powder. 10x seems slow.

Hot cors? I've been looking at those. Seems like a stouter bullet than the 270 btsp.
let me know what you find on powder. If there's a way to get another chunk of velocity with a 250-270 I'd be interested

 

[Alibiiv]

Agreed. I think that's why alibiiv ran into pressure early on. Don't worry, I'm running regular bullets with the published load data and prepping a pressure ladder

I was using the Maker bullets, they were long and the loads were really compressed. What I did get for a suggestion from another forum was to look at load data for the .375 Winchester. I have a Lyman, 51st edition (?) loading manual. There were a number of powders being used for the cast bullets. It "is" a place to start!! What I did read in the .375 Winchester data in the Lyman manual there was a variety of different powders. Powders listed were 2400, IMR-4227, IMR4198, RX7, IMR3031, getting velocities around 1800fps with a 264gr cast bullet. The loads ran from 24.0 grains using the 2400 to 32 grains for the 3031. Again this data was for heavy cast bullets, 265 grain, but...nonetheless a place to start. This is a wildcat cartridge, your rifle in unique in itself so you have to proceed slowly and work up from there. Good luck with your project. I have three 35 Whelens that started out as 30-06s that JES rebored, we are happy with his work.

 

[ShadowAviator]

I would like to caution you about the 10X load data. I used the 10X load data to load the Maker 250 grain T-Rex bullet. The load data listed from the Raptor site for the 250gr Game King was 44.4 grains of 10X. I started out using 41.0 grains of 10X as a starting load. The 41.0 grain load gave me a hard bolt lift. The pressure signs were too evident, I stopped with that one round. From there I dropped the load down to 38.5 grains of 10X and worked up from there. I could only get 2100fps out of the load. I found these velocities to not be what I was looking for; or... what was published. I haven't tried the load data for the .358 Winchester data as of yet. Perhaps I can get the velocity I am looking for with a different powder. If I could get up into the 2450-2600 fps velocities it would be what I am looking for. I am not certain that I can get this out of the cartridge. I would like to get this cartridge to work in this rifle, I've got quite a bit of time and about $2000 put into the build.

41gr of 10x is indeed on the max side for the 250gr Maker. My data shows I got pressure signs at 41.5gr.

Accurate 2200 got me up to 2300 fps.

I think I will test faster powders. H4198 if I can find it and CFEBLK, which I have.

If you are willing to go a little lighter on the copper bullet, you could maybe get above 2450fps. I have pushed the 190gr makers to 2600fps, and a 230gr copper bullet to 2450fps.

 

[Alibiiv]

41gr of 10x is indeed on the max side for the 250gr Maker. My data shows I got pressure signs at 41.5gr.

Accurate 2200 got me up to 2300 fps.

I think I will test faster powders. H4198 if I can find it and CFEBLK, which I have.

If you are willing to go a little lighter on the copper bullet, you could maybe get above 2450fps. I have pushed the 190gr makers to 2600fps, and a 230gr copper bullet to 2450fps.

I am getting out of the .375 Raptor build. There will be a listing for the AR barrel and components listed in the classifieds. I am heading in a different direction.

 

[marksman1941]

I am getting out of the .375 Raptor build. There will be a listing for the AR barrel and components listed in the classifieds. I am heading in a different direction.

Is it just not doing what you hoped it would?

 

[Alibiiv]

Is it just not doing what you hoped it would?

Is it just not doing what you hoped it would?

I built this rifle because I could not find a rifle in the cartridge that I wanted, only to find (after the rifle was built) a rifle in the cartridge that I was looking for. I look at rifles as tools for hunting, the right tool for the job. Well...now I have two tools to do one job, meaning two rifles, and now one has to go. We have two Raptor rifles. The .375 Raptor upper parts that I listed are from my son's AR10, I too have a Ruger 77 that I plan on listing as well. Right after I got the Ruger 77 back from the gunsmith I found a NIB Ruger 77 Hawkeye in .450 Bushmaster. It is a SAAMI approved cartridge, plenty or powder and components and it is a hard hitting rifle; and...it fits the bill for hunting black bear from a ground blind. If I had not found the Hawkeye I would be working on load development for the Raptor.

 

[marksman1941]

I built this rifle because I could not find a rifle in the cartridge that I wanted, only to find (after the rifle was built) a rifle in the cartridge that I was looking for. I look at rifles as tools for hunting, the right tool for the job. Well...now I have two tools to do one job, meaning two rifles, and now one has to go. We have two Raptor rifles. The .375 Raptor upper parts that I listed are from my son's AR10, I too have a Ruger 77 that I plan on listing as well. Right after I got the Ruger 77 back from the gunsmith I found a NIB Ruger 77 Hawkeye in .450 Bushmaster. It is a SAAMI approved cartridge, plenty or powder and components and it is a hard hitting rifle; and...it fits the bill for hunting black bear from a ground blind. If I had not found the Hawkeye I would be working on load development for the Raptor.

Makes total sense to me. I tend not to overstock on any one cartridge or type of cartridge

 

[marksman1941]

Turns out my rifle does not like Hornady interlock, which stinks cause that's what I was hoping to use. It really, really likes speer 270gr btsp. These two loads are identical in every way aside from the bullet. 5 shot, 100yd groups shot round robin style