Neck Tension Question

[AZHTR]

I've read many "opinions and articles" on neck tension, however, I have one question I'm needing some of your expert opinions on. My brother and I shoot "almost identical rifles"....7mm Rem Mag, Nosler brass, CCI Primer, 168 VLD Berger's, 70.5 grains of IMR7977, .025 OTL. (26" Bartlein barrel, same reamer used on both)

His rifle shoot ~3040 FPS and mine shoots ~2925 FPS. (And I do understand ALL barrels Have their own idiosyncrasies) The only process that we don't do the same is neck sizing. He uses a bushing type and I use a .283 mandrel. (I have shot his reloads in my rifle and experienced the higher FPS)

Ok, here comes the question - can that difference in reloading NECK TENSION be a very consistent difference in a 100+ FPS?

Please let me know what your thinking, thx

 

[243winxb]

https://apps.dtic.mil/docs/citations/ADA341390 A crimp or more neck tension, may make a difference?

 

[QuietTexan]

Which of you has the lower SD?

 

[AZHTR]

We don't have a great chronograph, additionally, I'm using a A&D 120 scale and my brother uses a Hornady scale. But with that said, we both shoot fairly well/consistent out to a 1000 yards, I just have to use a few more "clicks" up than he does. I think my next test will be to use a .282 mandrel and see what that does.

 

[Beluebow]

We don't have a great chronograph, additionally, I'm using a A&D 120 scale and my brother uses a Hornady scale. But with that said, we both shoot fairly well/consistent out to a 1000 yards, I just have to use a few more "clicks" up than he does. I think my next test will be to use a .282 mandrel and see what that does.

I would break down 2-3 of his loaded rounds, weigh each powder charge on your scale and eliminate that variable first.

 

[ButterBean]

To answer your question .......Yes, as 243winxb has shown

 

[Rardoin]

Yes, neck tension differences will change velocity so that is a possible cause. Are you both shooting the same lot of powder, bullets, primers? Some differences can be had there. And, as you have mentioned, barrels of the same specs/manufacturer can run differently.

 

[AZHTR]

Same brass, same lot of powder, different lot of bullets. I've been shooting fairly long distance for ~5 years, I haven't seen a 100+ FPS difference in various lots of Berger bullets yet. I'm going to get some Deltronic Gauge Pins and try to measure the inside diameter of his resized brass using a bushing versus my resized brass using my expander mandrel.

 

[Rardoin]

I have not seen any significant velocity variation between lots of Berger's target bullets (hybrids/VLD's). If it is not a difference in neck I.D. then likely just barrel differences and perhaps state of fouling.

 

[ShtrRdy]

I would try swapping ammo to see if the velocity follows the ammo or stays with the barrel.

If it follows the ammo then you'll have to try the process and tooling differences.

 

[AZHTR]

I have shot my brother's reloads in my rifle, and yes I get the higher velocity /FPS in my rifle. I'm just having a tough time thinking that a potential ~.001/.002 neck tension equals ~100+ FPS. Another test I could run, let my brother reload using his same process EXCEPT use my .283 mandrel for neck sizing. That might be the easiest test.

 

[ShtrRdy]

Do you guys clean the brass the same?

Any lube in the case neck by either of you?

 

[AZHTR]

Probably not exactly the same process, but my earlier statement, a 100+ FPS is big IMO. I certainly have learned in the last few years of reloading that what you may not think matters.......really does matter. Maybe all these little reloading process differences "might" add up to a higher velocity. I'm just not convinced just yet. I'll keep looking and report back.