30BR ? 125 gr. Sierra

[Bill Norris]

Looking for any info on the new 125 gr. Sierra bullet in the 30BR ? I see it is built and designed for the 300 blackout but was wondering how it might perform in the 30BR ?

 

[GerryM]

depends on the twist of your barrel
I have shot up to 130 gr pills , but my rifle has a 16 twiat

 

[AlNyhus]

Bill, those Sierra 125s are 1.140 long. Check the math re: the Sg with your twist rate. -Al

 

[Bill Norris]

I should have said my barrel is 1 - 15 Tw
on my hunter 30BR.

 

[AlNyhus]

Here's the JBM stability calculator. 70 degrees, sea level altitude and 29.92 baro are the normal default settings:

JBM - Calculations - Stability

www.jbmballistics.com

 

[joshb]

Hi Bill: Years ago, I bought 6K Sierra 125s. I was going to use them in my 308s but then I bought a 30br with a 17 twist. I tried the Sierras and they keyholed at 100. Randy Robinette was kind enough to help me out and said they were too long.
Being a little stubborn and after reading your thread about a “hunting 30br” , I just had a 10 twist short barrel spun up in 30br that can shoot the 125s. I had been looking for a 12 or 14 twist but a deal on the 10 popped up. Am I crazy building a gun because I have the bullets? Probably!
The 15 might do OK. Only one way to be sure. I could send you some of my old bullets to try. Let me know.

 

[Bill Norris]

Hi Bill: Years ago, I bought 6K Sierra 125s. I was going to use them in my 308s but then I bought a 30br with a 17 twist. I tried the Sierras and they keyholed at 100. Randy Robinette was kind enough to help me out and said they were too long.
Being a little stubborn and after reading your thread about a “hunting 30br” , I just had a 10 twist short barrel spun up in 30br that can shoot the 125s. I had been looking for a 12 or 14 twist but a deal on the 10 popped up. Am I crazy building a gun because I have the bullets? Probably!
The 15 might do OK. Only one way to be sure. I could send you some of my old bullets to try. Let me know.

PM SENT. THANKS

 

[WSnyder]

I should have said my barrel is 1 - 15 Tw
on my hunter 30BR.

15T probably a no go with those bullets with a stability factor of ~1. You’d probably need a 12 to make it go at a factor of ~1.5

 

[JackT]

I have a 30Br with a 14 twist and the Sierra 125s were shooting sub 1\2" ; put them on the shelf because I had some other loads shooting better, the testing has slowed down due to the desire to conserve primer and powder.

 

[Bill Norris]

I have a 30Br with a 14 twist and the Sierra 125s were shooting sub 1\2" ; put them on the shelf because I had some other loads shooting better, the testing has slowed down due to the desire to conserve primer and powder.

Yea the Nosler and Speer 125 gr. are shooting really well in my rifle but was just thinking about trying the new Sierra bullet.

 

[joshb]

Yea the Nosler and Speer 125 gr. are shooting really well in my rifle but was just thinking about trying the new Sierra bullet.

That answers one of my questions.

 

[RGRobinett]

Yea the Nosler and Speer 125 gr. are shooting really well in my rifle but was just thinking about trying the new Sierra bullet.

During the NBRSA Score Nationals last week, I was shown some of the Sierra 125 Match (I think they were/are FB) - didn't get to measure, but, by 'eyeball', compared to the 'old' 125s I made (1.00" jacket), they are LONG - see post #6, by joshb. I do not recall how long his measured . . . the addition of a BT, if that is what they are, will/would add yet another inch of twist rate requirement. RG

 

[Bill Norris]

During the NBRSA Score Nationals last week, I was shown some of the Sierra 125 Match (I think they were/are FB) - didn't get to measure, but, by 'eyeball', compared to the 'old' 125s I made (1.00" jacket), they are LONG - see post #6, by joshb. I do not recall how long his measured . . . the addition of a BT, if that is what they are, will/would add yet another inch of twist rate requirement. RG

Yea, they are pretty long. Joshb sent me some to try out and I get avg. OAL length - 1.105 inches. These are flat base. Will try them out in my 1 - 15 Tw. and report findings here.

 

[snowpro440]

Yea, they are pretty long. Joshb sent me some to try out and I get avg. OAL length - 1.105 inches. These are flat base. Will try them out in my 1 - 15 Tw. and report findings here.

Bill, will you be pushing them with H4198 ?

 

[tflorman]

Assuming you're talking about the Sierra 125 matchking or tipped matchking....they are long bullets, but the bearing surface isn't. I'm not sure how the effects the stability calculations though.

 

[Bill Norris]

Bill, will you be pushing them with H4198 ?

No Sir, I will load VV-N133 for these heavier class bullets. Start @ 33.0 gr. and work up. I have loaded the Sierra 125 gr. TGK and Speer TNT with it and found good accuracy @ 33.7 gr. I have also loaded Nosler 125 gr. BT and AB with it and found good accuracy @ 34.0 gr.

 

[Bill Norris]

Assuming you're talking about the Sierra 125 matchking or tipped matchking....they are long bullets, but the bearing surface isn't. I'm not sure how the effects the stability calculations though.

The 125 gr. Sierra Tipped Game King is longer than the Sierra 125 gr. F B H P. Bearing surface on the TGK measures .391 vs. the FB HP measures .372

 

[moorepower]

It's also designed to expand at velocities under 2000 fps muzzle velocity, so it "might" not be the best choice for a game taking bullet in a .30 BR.

 

[Bill Norris]

It's also designed to expand at velocities under 2000 fps muzzle velocity, so it "might" not be the best choice for a game taking bullet in a .30 BR.

Yea, I think you are correct. The Nosler B T and A B are gonna be the go to bullet for deer hunting here in the swamp. And I think maybe the Sierra TGK may work O K as well.

 

[RGRobinett]

Using 1.105" long, here's a SWAG, using the JBM (DRAG/TWIST) calculator - the OAL is by FAR the primary concern - changing other attributes may alter Sg by a couple of digits in the third decimal place (not displayed) - according the the GURUs, we need >Sg1.4. This was based upon a 1:15" twist BBL - the "twist" column indicates the recommended twist rate (for Sg1.5), while the far RT (Stability) colum displays the Sg for the 1:15 twist . . . RG

Drag/Twist
Input Data
Caliber:	0.308 in	Nose Length:	2.864
Meplat Diameter:	0.162	Ogive Radius:	10.000
Ogive Type:	Tangent	Boattail Length:	0.000
Base Diameter:	1.000	Total Length:	3.588
Rotating Band Diameter:	1.000
Bullet Weight:	125.0 gr	Specific Gravity:	9.00
Drag Function:	G1	Barrel Twist:	15.0 in
Output Data
RT/R:	1.000	Sectional Density:	0.188 lb/in²

Number	(ft/s)	Nose	Boattail	Base	Band	Skin	Total	(G1)	Factor	(in)	(>1.5)
Mach	Muzz Vel	CD	CD	CD	CD	CD	CD	BC	Form	Twist	Stability
Calculated Table
0.500	558.2	0.000	0.000	0.210	0.000	0.034	0.244	0.157	1.200	13.8	1.3
0.600	669.9	0.000	0.000	0.213	0.000	0.032	0.245	0.157	1.203	13.7	1.3
0.700	781.5	0.000	0.000	0.216	0.000	0.030	0.246	0.166	1.136	13.6	1.2
0.800	893.2	0.000	0.000	0.219	0.000	0.028	0.247	0.194	0.971	13.4	1.2
0.850	949.0	0.000	0.000	0.220	0.000	0.028	0.248	0.220	0.855	13.3	1.2
0.900	1004.8	0.000	0.000	0.222	0.000	0.027	0.249	0.259	0.728	13.1	1.1
0.925	1032.7	0.009	0.000	0.222	0.000	0.027	0.258	0.273	0.690	12.9	1.1
0.950	1060.6	0.022	0.000	0.223	0.000	0.026	0.271	0.283	0.665	12.7	1.1
0.975	1088.5	0.035	0.000	0.223	0.000	0.026	0.284	0.294	0.639	12.3	1.0
1.000	1116.4	0.047	0.000	0.263	0.000	0.026	0.336	0.270	0.698	14.2	1.3
1.100	1228.1	0.128	0.000	0.257	0.000	0.025	0.410	0.270	0.698	13.4	1.2
1.200	1339.7	0.122	0.000	0.251	0.000	0.024	0.397	0.303	0.621	13.5	1.2
1.300	1451.4	0.120	0.000	0.244	0.000	0.023	0.388	0.320	0.588	13.6	1.2
1.400	1563.0	0.119	0.000	0.237	0.000	0.022	0.379	0.329	0.572	13.8	1.3
1.500	1674.7	0.117	0.000	0.230	0.000	0.022	0.368	0.336	0.561	13.9	1.3
1.600	1786.3	0.115	0.000	0.222	0.000	0.021	0.358	0.340	0.553	14.0	1.3
1.700	1898.0	0.113	0.000	0.215	0.000	0.020	0.348	0.344	0.548	14.1	1.3
1.800	2009.6	0.111	0.000	0.207	0.000	0.020	0.338	0.346	0.544	14.1	1.3
2.000	2232.9	0.108	0.000	0.191	0.000	0.019	0.318	0.351	0.536	14.3	1.4
2.200	2456.2	0.106	0.000	0.175	0.000	0.018	0.299	0.358	0.526	14.4	1.4
2.500	2791.1	0.104	0.000	0.153	0.000	0.017	0.273	0.372	0.506	14.5	1.4
3.000	3349.3	0.100	0.000	0.121	0.000	0.015	0.236	0.409	0.460	14.6	1.4
3.500	3907.6	0.097	0.000	0.097	0.000	0.014	0.207	0.458	0.411	14.7	1.4
4.000	4465.8	0.095	0.000	0.078	0.000	0.012	0.185	0.509	0.370	14.8	1.5
4.500	5024.0	0.093	0.000	0.064	0.000	0.011	0.168	0.560	0.336	14.9	1.5

17-Aug-22 07:22, JBM/jbmdrag-5.1.cg