Bullet length and pressure

[KeeblerArmy]

On the left we have a nosler 175gr something
On the right is a 175gr SMK

Mag length is my limitation here, so I will have to seat the nosler deeper into the case to get an acceptable overall length. For the SMK I am using 43.0 gr of IMR4064.

I can hear the nosler crunch powder trying the same recipe.. same mass but different bullet shape, so am I going to run into potential pressure issues here? Should I do a new work up for this bullet shape?

Thinking out loud, the issue would be trying to fire up the same quantity of powder inside a smaller case dimension.. therefore likely more pressure..am I looking at this correctly?

 

[918v]

Yes

 

[KeeblerArmy]

Damn
Yeah just looked at Noslers data too. 43.0 they consider to be a max load for 4064. 39.0 being most accurate. 2297fps though, super slow.

Good thing I only have another box left

 

[nealm66]

Maybe look at a faster powder. There might be one that’s a bit faster but less pressure

 

[straightshooter1]

Damn
Yeah just looked at Noslers data too. 43.0 they consider to be a max load for 4064. 39.0 being most accurate. 2297fps though, super slow.

Good thing I only have another box left

You might want to simply reduce your load down by .8 grs to 42.2 grs for the Noslers as my QuickLoad app suggests the pressure for that would be close to the same as 43.0 grs for the SMK.

 

[Snuby642]

The tangent ogives vs the secant ogives.

The fight begins.

 

[KeeblerArmy]

You might want to simply reduce your load down by .8 grs to 42.2 grs for the Noslers as my QuickLoad app suggests the pressure for that would be close to the same as 43.0 grs for the SMK.

That’s super interesting, because there might be an accuracy node right there. 39.0 was solid like the book said, and it opened up right around 40.5-41.5, which is as far as I tested it today

 

[918v]

What brass are you using?

 

[straightshooter1]

That’s super interesting, because there might be an accuracy node right there. 39.0 was solid like the book said, and it opened up right around 40.5-41.5, which is as far as I tested it today

BTW, that calculation is based on identical COAL's.

 

[KeeblerArmy]

What brass are you using?

*Mostly* federal, because I have a ton of it. An occasional Winchester or PPU or something sneaks in there

One day I’ll invest in some decent brass

 

[918v]

FC and PPU has less capacity than commercial Win. I would go 41.6, 41.7, etc. until the groups shrink again, but not anywhere near 43grs.

 

[straightshooter1]

*Mostly* federal, because I have a ton of it. An occasional Winchester or PPU or something sneaks in there

One day I’ll invest in some decent brass

As 918v pointed out above, Winchester brass has MORE case capacity than the Federal or PPU. PPU has almost the same capacity as Federal. If your Winchester brass happens to "sneak" in there with the Federal brass, it's going to produce a significant difference in results due to that difference in capacity (given the same load). You'll want to be sure to keep your Winchester brass separate from your Federal's.

 

[KeeblerArmy]

42.2 looks like a solid performer! The flier was totally me

and noted about the Winchester brass, I’ll get that stuff out of there

 

[seanh]

Speaking from experience, you can definitely run into pressure issues. I recently swapped stock / chassis so I can run a dbm. My prior rounds we're set for single-round feeding, that I conveniently see the deeper to fit in the mags. I didn't think anything of it since my prior load was well within pressure.

308 tight bore Barrel, 27 inch length, prior load with sending 178 grain amax just kissing 2800...new length kissing 3k. While there was a distinct pressure rise, I wasn't flattening primers, blowing primers Etc. ... I was close and not a good round for 100 + Degree Days

 

[918v]

Speaking from experience, you can definitely run into pressure issues. I recently swapped stock / chassis so I can run a dbm. My prior rounds we're set for single-round feeding, that I conveniently see the deeper to fit in the mags. I didn't think anything of it since my prior load was well within pressure.

308 tight bore Barrel, 27 inch length, prior load with sending 178 grain amax just kissing 2800...new length kissing 3k. While there was a distinct pressure rise, I wasn't flattening primers, blowing primers Etc. ... I was close and not a good round for 100 + Degree Days

BS

 

[seanh]

Seriously... You shove a bullet deeper in the case and your pressure goes up so does your velocity

 

[918v]

Yes I agree, just not with your 3000 FPS with 178’s.

 

[seanh]

I know what you mean. When I saw it on my chronograph I was a bit surprised... More like what the fuck. A half-dozen or so shots later confirmed it. That that velocity I really would have expected completely flattening if not blown primers.

You ever shoot tightbore Barrel? If you do then you know you'll get some what the fuck moments.

 

[918v]

Tight bore barrels have been around for decades and if there was any velocity advantage to them with match grade bullets then people would be all over them, especially with 200 FPS increase in a 308.

 

[seanh]

So the answer is no, you don't have experience with them

 

[918v]

No why would I?

A tale of two guns / tight bore vs. standard bore

Didn't know if I should post this in the reloading forum or in bolt action rifles. I figured bolt action rifles as it's more about the barrels than the actual reloading or the load data. We get asked the question a lot about tight bore barrels and standard bore barrels, faster, slower, barrel...

www.snipershide.com

 

[918v]

Wait I found proof. Sean is right. Go to the 7:00 mark

 

[seanh]

You should probably go talk to Frank correctly like I did. His response to me was this "you may see zero difference, you may see 25-50fps, have had reports up to 100+...100 isn't likely but has been reported." Pretty much my finding...some factory no difference, some 25-50, some WTF.

Thanks for caring enough about what I say to do the research.