22 cal Tipped MatchKings 69 gr. From 22-250

[Brians356]

Sierra has a 60gr TMK at midway. Works with 10 twist or faster. It has roughly the same bc as the 69smk.

That's odd. Sierra say their standard 60 HP hunting bullet only needs 1:12 in 223, or 1:14 in faster 22-250:

https://www.sierrabullets.com/product/22-caliber-60-gr-hp/

Why would 60 TMK require 1:10 twist? (Their page doesn't mention twist for 60 TMK.)
-

 

[Rtheurer]

One thing you might try just to see if it will make a difference is scrub the Daylights out of the barrel and get it really clean. That may expose more of the rifling and help it grab a better hold on the bullet and twist it harder.

One of the problems with this is if it does indeed work you'll have to always keep the barrel clean

Is this a thing?

 

[Evlshnngns]

That's odd. Sierra say their standard 60 HP hunting bullet only needs 1:12 in 223, or 1:14 in faster 22-250:

https://www.sierrabullets.com/product/22-caliber-60-gr-hp/

Why would 60 TMK require 1:10 twist? (Their page doesn't mention twist for 60 TMK.)
-

Bullet length, I guess. The 60 tmk is longer than the 69smk.

 

[Zero333]

Your 10" twist is stabilizing the 69tmk just fine.

Your instability problem is likely from bad bullets / jackets or very rough throat / rifling.

 

[mike22250]

No in a 22-250, the 10 should work for the 68 bthp. Buddy shoots those in a 9 twist 223. It may be a borderline 9/10 twist bullet but pushed at 22-250 speeds, the 10 should sounds it fine. Is your barrel a factory barrel, if so, who makes the gun ? May be that you are incorrect in twist rate. I once thought I had a 14 twist 22-250 barrel and turned out to be a 12. That's another option on why they aren't stabilizing.

Its an Bergara 10 twist. Remage barrel i purchased 8 years ago.

 

[mike22250]

Sierra has a 60gr TMK at midway. Works with 10 twist or faster. It has roughly the same bc as the 69smk.

Im heading to pick some up this weekend.

 

[284winner]

Its an Bergara 10 twist. Remage barrel i purchased 8 years ago.

Ok then. That answers that. Strange that you can't stabilize them tmks with that 10 twist at 3200+ !!!

 

[mike22250]

Ok then. That answers that. Strange that you can't stabilize them tmks with that 10 twist at 3200+ !!!

Agree, I thought the same. It could be that it was cold about 35ish°. I did pick up 300 of the 60 TMKs through Midway, the will be here next week.

 

[284winner]

Agree, I thought the same. It could be that it was cold about 35ish°. I did pick up 300 of the 60 TMKs through Midway, the will be here next week.

Gotta believe they'll work. Still scratching my head on the 69s. I can stabilize them in my 223 at 2900. It's a 9.250 twist. Much slower than your 250

 

[fyrewall]

Hornady call a 1;7 twist for the 68 bthp?

Probably does but real life shows great results with 7.7, 8 & 9 twists.

 

[fyrewall]

I ran both the On-line JBM & the Miller stuff on my excel - came out with same results - same bullet, same data, same Sg

The formula that produced the Miller Sg is shown on the excel spread sheet. Data values in columns and rows. I might redo it using Fortran to get formula stuff that means something.
The bullet is: 68 Hornady .224 HP Boat tail, length .987 (via caliper), MV 3150 (.22-250), twist 9, temp 59 F, pressure 29.92 in Hg.

Are we talking about the same JBM or is there another JBM stability calculator? This is a great coyote bullet. I shoot these out of a .22-.250, 7.7 twist, MV 3250, with CCI 34 primers and H4350 or H414. Fine long range accuracy even at temps under 20 F.

Some other bullets are shown: a .30 cal. torpedo like projectile, and a .20 cal. Vmax with the little plastic tippy thingy that should be an abysmal stability failure but is not.

 

[fyrewall]

For .224 bullets of this length you really need 1:9", or, faster twist rate - when it comes to polymer tipped bullets, the Miller formula is lacking: JBM is far better for calculating Sg which we can,"bank on" - especially for the, "tipped" projectiles. For most HP bullets, specific gravity input of 10.2 will get you close - tipped bullet will run 10.0, or, less (lower specific gravity of construction will require faster twist rate - think aluminum!)

At Std. conditions, these bullets (OP) need 1:8.5" twist for Sg 1.5, or, "sure-fire" stability: 1:9" would probably produce about Sg 1.4. Polymer tipped bullets add substantial length (over-turning moment) without a significant shift in CG.

Mr. Peffley is correct - even if we had "magic" powder, which would produce 4K++ FPS, at safe pressure, we'd only gain a few points in the second decimal place, when we need a nearly two point increase in the FIRST decimal place. The notion of increasing velocity to obtain meaningful Sg increase is simply myth and misinformation. If the combination of TWIST rate and bullet length results in marginal, or, inadequate stability, performance will suffer - especially in denser air. RG

Edited to [somewhat] clarify - AM 3/1.

Mr. Robinett:
My previous thread is offered for comment.

Regards,

Fyrewall (FW)

 

[mike22250]

I just did the patch test to check the twist and was surprised.....

 

[Patton243]

69 TMK out of my 22-250 shot well in my 1:9 twist. Guy mentioned above a 60 grain TMK Sierra makes that would be a better fit for your 1:10 IMO. I use the 60s with H4895 now and I like them better for Varmint use.

 

[ALBULLET]

I just did the patch test to check the twist and was surprised.....


View attachment 1093423

Bingo!!!

 

[mike22250]

Bingo!!!

I was shocked..... why would they mark a 10 twist when it really is a 12 twist? I would hope they would be able to control their accuracy a bit better then that. If i was getting around 10.1 to 10.5 i would understand that being closer, but being 2" off is really shocking!

 

[fyrewall]

I have read up on button type rifle barrel making. I am still wanting to get inside my favorite barrel maker's shop to see them button rifle a barrel. Apparently, the barrel is rotated during withdrawal of some super hard button (like a snake swallowing a pig) and the rifling is engraved inside the barrel. At this point the rate of rotation would control the rate of twist, hopefully slow and easy and constant. No doubt some barrel makers are reading this stuff and would hopefully fire back a response that would boost my knowledge.

I modified my excel spread sheet to provide allowances for length of the little plastic tippy thing. Looking at the existing formula on the attached spread sheet I added another row value, thus moving all row values down by one after the existing bullet length row. The next new row value like after C6, C24, & C36 would be C7, C25 & C37. The new row values represent the tip length. The following step would be to subtract the tip length from the bullet length and proceed with the calculation.

Plastic tips (poly carbonate?) are not weightless but have about 15% of the density of brass or copper. I would guess to come up with better Sg approximation this would be needed to be considered but I did not do this.

Looking at other stuff in the Sg approximation equation I noticed that the twist is divided by the bullet diameter then squared this represents a big impact on stuff and so small changes in twist would be reflected by bigger shifts in Sg's.

I am still playing around the Miller stuff hoping to get a better feel for it. At this point the Miller approximation appears to be identical to the method used by JBM.

Practical applications are the .204 40 Vmax in the .20 practical & .204 Ruger. Hornady must make zillions of these bullets for many 1-12 twist .204 Ruger rifles. Using the Miller approximation the Sg is .98 for a OAL bullet length of .753. The Miller approximation is 1.3 when the .139 plastic tip length is subtracted. Any detrimental changes like lower temperatures and funny slower twist rates would reduce the approximated Sg. Having .20 barrels of honest (true) 11 twist rates and a Miller approximation Sg of 1.3 the 40 .204 Vmax shoots great out of my 3 .20 caliber rifles. Bang, zip, splat!

The results might not be so good with the 40 Vmax if a barrel marked 12 twist was actually closer to 13 and frost was on the ground. This gets into actual results vs. "keyboard ballistics"

The Miller stuff is a straight forward approximation. With computers able to preform zillions of iterations in a moment better Sg values could be had by fitting variables to observed results.

I once had a true 10 twist .22-.250 barrel that shot real good with 68 Hornady Hpbt bullets having a OAL of .987; that is on the longish side for 68 - 69 .224 bullets. On nice warm calm days I could hit silhouette chickens at the half section line (880 yards). A 69 Sierra Tipped Match King should be better suited to a 10 twist barrel and I think Sierra got it right with a 10 twist advisory that is on the box.

 

[mike22250]

I have read up on button type rifle barrel making. I am still wanting to get inside my favorite barrel maker's shop to see them button rifle a barrel. Apparently, the barrel is rotated during withdrawal of some super hard button (like a snake swallowing a pig) and the rifling is engraved inside the barrel. At this point the rate of rotation would control the rate of twist, hopefully slow and easy and constant. No doubt some barrel makers are reading this stuff and would hopefully fire back a response that would boost my knowledge.

I modified my excel spread sheet to provide allowances for length of the little plastic tippy thing. Looking at the existing formula on the attached spread sheet I added another row value, thus moving all row values down by one after the existing bullet length row. The next new row value like after C6, C24, & C36 would be C7, C25 & C37. The new row values represent the tip length. The following step would be to subtract the tip length from the bullet length and proceed with the calculation.

Plastic tips (poly carbonate?) are not weightless but have about 15% of the density of brass or copper. I would guess to come up with better Sg approximation this would be needed to be considered but I did not do this.

Looking at other stuff in the Sg approximation equation I noticed that the twist is divided by the bullet diameter then squared this represents a big impact on stuff and so small changes in twist would be reflected by bigger shifts in Sg's.

I am still playing around the Miller stuff hoping to get a better feel for it. At this point the Miller approximation appears to be identical to the method used by JBM.

Practical applications are the .204 40 Vmax in the .20 practical & .204 Ruger. Hornady must make zillions of these bullets for many 1-12 twist .204 Ruger rifles. Using the Miller approximation the Sg is .98 for a OAL bullet length of .753. The Miller approximation is 1.3 when the .139 plastic tip length is subtracted. Any detrimental changes like lower temperatures and funny slower twist rates would reduce the approximated Sg. Having .20 barrels of honest (true) 11 twist rates and a Miller approximation Sg of 1.3 the 40 .204 Vmax shoots great out of my 3 .20 caliber rifles. Bang, zip, splat!

The results might not be so good with the 40 Vmax if a barrel marked 12 twist was actually closer to 13 and frost was on the ground. This gets into actual results vs. "keyboard ballistics"

The Miller stuff is a straight forward approximation. With computers able to preform zillions of iterations in a moment better Sg values could be had by fitting variables to observed results.

I once had a true 10 twist .22-.250 barrel that shot real good with 68 Hornady Hpbt bullets having a OAL of .987; that is on the longish side for 68 - 69 .224 bullets. On nice warm calm days I could hit silhouette chickens at the half section line (880 yards). A 69 Sierra Tipped Match King should be better suited to a 10 twist barrel and I think Sierra got it right with a 10 twist advisory that is on the box.

Thanks for the info.

 

[284winner]

Bullet length, I guess. The 60 tmk is longer than the 69smk.

Bearing surface or OAL ?

 

[chop house]

the 22-250, nothing has outperformed IMR 4064 for me in that cartridge.

i am just curious, and maybe you have had no need to experiment, but how is varget in comparison in your rifles?