Flash hole sizes in .308 SRP brass

[kiwijohn]

OK so I know why we have small flash holes in the SRP brass, especially from Lapua. But I have seen in Starline MATCH SRP brass (.308) that they have large flash holes.
My question is has anyone tested, if there is a variance in ignition or SD or on paper at the target, between the two flash hole sizes, using the same brand of case.
Why I ask this is that I have discovered I ran some of my Lapua SRP brass through a large decapper and made the hole bigger. This would be for a run of 100.
( yeah brain fart moment!)
I could imagine that at 1000 yds there will be a variance but at shorter distance not so much. I may relegate the offending brass to the 300 yard shoots.
According to my records I have 15 firings on these cases, annealed every time, running 155 grain projectiles @ 3000fps.
Since Lapua arent making SRP brass at present, case lives matter.

 

[Bill Norris]

Alpha said they did test and decided the large flash hole was better than small in their brass.

 

[Acyr]

I have recently shot both Starline Match SRP and Lapua Palma SRP with the same primer (Wolf small rifle magnum) and found zero difference on the target or Labradar. That surprised me. I was even more impressed with the quality of Starline Match SRP Brass.

 

[kiwijohn]

Ok I hjad read one of the previous threads on flash / spit holes but didnt find a conclusion. Maybe I need to drill them all!
Since the primer punch is a little variable I could take a drill to those 100 to get a uniform dimension.

 

[kiwijohn]

@Acyr I run the Starline SRP in a Rem 5R just so I dont mix it with my FTR rifle ( running the Lapua)
I only have a couple of firings on the Starline but its looking good.

 

[Trevor60]

The Lapua SP brass with the primer hole .059 was to manage ignition better over it large primer counter part. Dr. Tom Whitaker was the shooter who brought this brass program forward.

Between the two primers SP vs LP the SP's smaller ignition resulted in better ES /SD numbers.
Drilling out the flashole in a small primer case would permit more ignition.

There has been two tests ACYR who posted here and Bryan Zolnikov 2023 on youtube with the same results. NO change with different cartridges same result.

Jack Neary (rifle tuning part 2) had an opposing finding 12 years go reporting that there was a change in accuracy.

If there is a larger flash hole for ignition going in, than consequently their would be more PSI back pressure going out. With the speeds and pressure us F/TR guys run i wonder if the additional PSI pressure would manifest itself in the primer or boltface with piercing or blanking primers.

It would further stand to reason sorting primers would show greater benefits.

Cheers
Trevor

 

[Ned Ludd]

As was previously noted by @Bill Norris above, Alpha Munitions stated they found a slight improvement in ES/SD using the larger flash hole. In more realistic terms, I have been using both Lapua and Alpha brass in F-TR loads for years. If there is any difference in flash hole size in terms of ES/SD, I cannot reliably demonstrate it using a LabRadar. Nor have I noticed any difference in precision. One can certainly debate the advantages/disadvantages of small versus large flash holes. However, if significant differences cannot actually be reliably detected using a rifle set up for a specific shooting discipline such as F-TR, the discussion will be moot.

 

[Acyr]

The Lapua SP brass with the primer hole .059 was to manage ignition better over it large primer counter part. Dr. Tom Whitaker was the shooter who brought this brass program forward.

Between the two primers SP vs LP the SP's smaller ignition resulted in better ES /SD numbers.
Drilling out the flashole in a small primer case would permit more ignition.

There has been two tests ACYR who posted here and Bryan Zolnikov 2023 on youtube with the same results. NO change with different cartridges same result.

Jack Neary (rifle tuning part 2) had an opposing finding 12 years go reporting that there was a change in accuracy.

If there is a larger flash hole for ignition going in, than consequently their would be more PSI back pressure going out. With the speeds and pressure us F/TR guys run i wonder if the additional PSI pressure would manifest itself in the primer or boltface with piercing or blanking primers.

It would further stand to reason sorting primers would show greater benefits.

Cheers
Trevor

I think Jack Nearys test would be accurate in the Benchrest world. I don't believe in FTR, shooting the 308 the differences could be seen on target. Powder and bullets have improved since Jacks test but we can only do so much with the 308.

 

[kiwijohn]

Well that puts my mind at ease somewhat, thanks for the input folks.

 

[Acyr]

Well that puts my mind at ease somewhat, thanks for the input folks.

Seating depth test today @600 using Starline Match brass. 308 win, 200 Hybrids off a bipod.

 

[D-4297]

Show-Off ! I'm next to Acyr on the line , getting beat up by the wind , shooting 9's , and he shooting groups ? Sometimes life just isn't fair . That wind was swinging from SW to SE in half a split second , And RUDE !