Velocity Plateau using Lil’gun

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Velocity Plateau using Lil’gun

Postby Kawi-vn750 » Mon May 13, 2019 11:59 am

I’ve recently started reloading for the 450bm. The firearm is the Ruger American Ranch 16” barrel with a 1/16 twist. I’m using lil’ gun, cci450 primers, hornady brass, 225 grain FTX’s and the 300 grain Speer deep curl bullets, using a tapper crimp at .471”.. I’ve ran a couple of batches over the chrony, the initial test I was able to get the 225’s up to 2350fps and the 300’s up to 1950fps with out the slightest pressure signs. The next batch I ventured into the unknown zone, working up in half grain increments well beyond published data. It seams as though no matter how much powder I use I can not get past 2450fps on the 225 grainers and 2050fps on the 300 grainers. I did not see any pressure signs just seemed to be wasting powder. Admittedly, this is the first straight wall cartridge I ve loaded for so I steered clear of any compressed loads as I do not know how this powder and cartridge will react. Looking for advice on how to gain additional velocity. My goal is get the 300 grainers up to 2100 or more to achieve the same trajectory as the factory 250ftx loads. And to get the 225 grainers as fast as possible in hopes of getting a flatter trajectory that the factory 250ftx loads. I apologize if this is a topic that has already been covered.
Last edited by Kawi-vn750 on Mon May 13, 2019 4:13 pm, edited 2 times in total.
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Re: Velocity Plateau using Lil’gun

Postby plant_one » Mon May 13, 2019 3:43 pm

what firearm are you reloading for? how long is your barrel? what twist? etc...

knowing your firearm will help us provide you some info as to where you're at and where you can go to
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Re: Velocity Plateau using Lil’gun

Postby Kawi-vn750 » Mon May 13, 2019 3:53 pm

Thanks. I edited my original post. The gun is the Ruger American Ranch 16” barrel with 1/16twist.
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Re: Velocity Plateau using Lil’gun

Postby Al in Mi » Mon May 13, 2019 4:00 pm

My experience with Lilgun is when the speeds stop going up as powder is increased, that's when I was on the edge of pressure. This was with 230gr FMJ and 250gr FTX bullets.

You might want to try H110/296 to get things going a bit faster.
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Re: Velocity Plateau using Lil’gun

Postby Hoot » Tue May 14, 2019 9:42 am

IMHO, with a short carbine (16") length barrel, you may be seeing the plateau because you're throwing the additional powder out the the muzzle before it can generate additional velocity. Otherwise there is no explanation given your choice of primer. I don't know another member who uses such a severe crimp. With a taper crimp, there comes a point where the effect reverses due to resizing down a majority of the bullet's bearing surface, resulting in less bore pressure. I've never crimped less than .474 measured precisely at the lip with a micrometer. Even then, it was down into a driving band groove on Barnes bullets. The further down the case you measure, the thicker the case wall gets. That's why it should be measured carefully, as close to the mouth as reasonably possible. Gauging the taper crimp resultant diameter, further down the case, contributes toward squeezing the bullet smaller in diameter. The taper crimp doesn't just taper at the very end of the case. The inside of the taper crimp die is not curved, its slanted. The further up into the die that you push the cartridge the further down the case that slant is imparted. I tried saying this several ways since I don't know your experience with internal ballistics. Not trying to belabor the point.

With the 250 FTX you might want to limit your crimp diameter to no less than .475-.476 and if you're crimping the case mouth down into the bullet's cannelure with the 225 FTX, then you can go a little further, say .474-.475.

That's something you can experiment with since you're up against a conundrum. Admittedly, its grasping at straws but at least its something to try. Lastly, my experience with Lil Gun vs W296 has been that I saw plateauing more with W296 than Lil Gun, but that's just my experience and admittedly I was using a 1:24 twist 20" barrel on an AR platform, which obviously is a horse of a different color than a bolt action.

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Re: Velocity Plateau using Lil’gun

Postby Kawi-vn750 » Tue May 14, 2019 10:11 am

Hoot wrote:IMHO, with a short carbine (16") length barrel, you may be seeing the plateau because you're throwing the additional powder out the the muzzle before it can generate additional velocity. Otherwise there is no explanation given your choice of primer. I don't know another member who uses such a severe crimp. With a taper crimp, there comes a point where the effect reverses due to resizing down a majority of the bullet's bearing surface, resulting in less bore pressure. I've never crimped less than .474 measured precisely at the lip with a micrometer. Even then, it was down into a driving band groove on Barnes bullets. The further down the case you measure, the thicker the case wall gets. That's why it should be measured carefully, as close to the mouth as reasonably possible. Gauging the taper crimp resultant diameter, further down the case, contributes toward squeezing the bullet smaller in diameter. The taper crimp doesn't just taper at the very end of the case. The inside of the taper crimp die is not curved, its slanted. The further up into the die that you push the cartridge the further down the case that slant is imparted. I tried saying this several ways since I don't know your experience with internal ballistics. Not trying to belabor the point.

With the 250 FTX you might want to limit your crimp diameter to no less than .475-.476 and if you're crimping the case mouth down into the bullet's cannelure with the 225 FTX, then you can go a little further, say .474-.475.

That's something you can experiment with since you're up against a conundrum. Admittedly, its grasping at straws but at least its something to try. Lastly, my experience with Lil Gun vs W296 has been that I saw plateauing more with W296 than Lil Gun, but that's just my experience and admittedly I was using a 1:24 twist 20" barrel on an AR platform, which obviously is a horse of a different color than a bolt action.

Hoot

I’ll have to check when I get home but I believe when I measured the factory 250ftx load the crimp was at .473-.474. My initial loads were crimped to .473 and the ES was huge 100fps on each charge. The next batch I did not bell the case mouth prior to seating the bullet, just sent them home nice and ginger like and crimped to .471-.472. I was able to pick up 80fps and brought the ES down to 30fps(this is all if my memory serves me right, need to check my notes) on my initial top charge of 33.0 grains of lil gun with the 300 grain deep curl 1957fps average 1908fps low 2011fps high with the .473 crimp/ 2037fps low 2069fps high and I think the average was 2048fps with the tighter crimp and no belling of the case mouth.
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Re: Velocity Plateau using Lil’gun

Postby Kawi-vn750 » Tue May 14, 2019 10:24 am

It’s hard to focus at work once I start thinking about guns and bullets and deer and new hunting spots and old hunting spots and new ways to hunt old hunting spot and new guns and new loads and and and .....I need to get back to work before I slip further into my happy place
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Re: Velocity Plateau using Lil’gun

Postby Hoot » Tue May 14, 2019 11:45 am

No need to respond right away. I know how it is at work. I've mic'd Hornady factory 250gr and they've been between .475-.476 at the mouth. Historically, the velocity SD yielded by the 450b taper crimp, has been higher than I would ever tolerate with a bottleneck caliber. A lot higher. When they first came out, the Remington Accu-Tip 450b loads I measured, had no taper crimp at all and they flew like it. Heavier crimps do tighten up that SD but this caliber takes such a rainbow trajectory that their 100 yd groups are still amazingly tight off a BR setup with modest taper crimps. The velocities you observed are not unheard of with a 16" barrel and the SAAMI spec'd COL of 2.25. I expect that there will came a day when there are two sets of specs. One for the original AR platform and one for Bolt Action/Single Shot rigs. For now, with your 16" barrel, I'd stick with Lil Gun's pressure curve for bullets <= 275gr and W296/H110 for heavier ones, but then that's just one opinion.

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Re: Velocity Plateau using Lil’gun

Postby Kawi-vn750 » Tue May 14, 2019 7:27 pm

Hoot wrote:No need to respond right away. I know how it is at work. I've mic'd Hornady factory 250gr and they've been between .475-.476 at the mouth. Historically, the velocity SD yielded by the 450b taper crimp, has been higher than I would ever tolerate with a bottleneck caliber. A lot higher. When they first came out, the Remington Accu-Tip 450b loads I measured, had no taper crimp at all and they flew like it. Heavier crimps do tighten up that SD but this caliber takes such a rainbow trajectory that their 100 yd groups are still amazingly tight off a BR setup with modest taper crimps. The velocities you observed are not unheard of with a 16" barrel and the SAAMI spec'd COL of 2.25. I expect that there will came a day when there are two sets of specs. One for the original AR platform and one for Bolt Action/Single Shot rigs. For now, with your 16" barrel, I'd stick with Lil Gun's pressure curve for bullets <= 275gr and W296/H110 for heavier ones, but then that's just one opinion.

Hoot


Had to check my crimp measurements when I got home. I’m getting .473 on the factory loads. But I did notice that there is a bit of play in my calipers which I’m sure has skewed my measurements. Time to pony up for a better set( if the boss lady approves that is). With that said, according to my wonky calipers I am crimping .002 more than factory which is all the further I care to go considering the round head spaces on the mouth. As far as powders go, i think i will try the h110 on the next batch. Curious if anyone has any luck or tried Enforcer or Accurate No. 9? Or maybe N120?
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Re: Velocity Plateau using Lil’gun

Postby Hoot » Tue May 14, 2019 9:24 pm

Kawi-vn750 wrote:Had to check my crimp measurements when I got home. I’m getting .473 on the factory loads. But I did notice that there is a bit of play in my calipers which I’m sure has skewed my measurements. Time to pony up for a better set( if the boss lady approves that is). With that said, according to my wonky calipers I am crimping .002 more than factory which is all the further I care to go considering the round head spaces on the mouth. As far as powders go, i think i will try the h110 on the next batch. Curious if anyone has any luck or tried Enforcer or Accurate No. 9? Or maybe N120?


IMHO, there is a place on the loading bench for a set (or two) of calipers but equally important is a micrometer for precise readings. A reliable micrometer doesn't have to break the bank, though you certainly can invest in a high buck one if you want. There are excellent value, name brand mics on Ebay, that may be a little dusty or show usage marks but which are worthy of their name sakes.

Here's an excellent one for a very reasonable price on Ebay. Link

Its the same model I use.

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