FLASH HOLE SIZE TEST

[Bill Norris]

Searching for any test results from SRP Small Flash Hole vs. SRP Large Flash Hole. Didn't see anything from a search. Anybody have any info ? Reason being Alpha SRP brass has the large flash hole. First time I've seen that combination.

 

[TIMO]

Watching. : )

 

[thekriebles]

Flash Hole Size

#53 = 0.0595”, works with the original 6BR & PPC flash holes, may be too small for cases like Lapua’s 308 Palma brass. I shoot that, uniform flash holes w/ K&M small primer tool @ 0.0625” or 1/16”. I also uniform flash holes to 1/16", but I use a Sinclair flash hole reamer; it makes it easy to...

forum.accurateshooter.com

 

[Ranger188]

Bill, not sure if this helps. A quote from Tom Danielson of Alpha

Thomas Danielson
May 4, 2020
"The smaller flash hole can present ignition problems in cold temperatures. We use the larger flash hole in our small primer brass for this reason. We saw better cold weather ignition with this setup."

 

[Bill Norris]

Bill, not sure if this helps. A quote from Tom Danielson of Alpha

Thomas Danielson
May 4, 2020
"The smaller flash hole can present ignition problems in cold temperatures. We use the larger flash hole in our small primer brass for this reason. We saw better cold weather ignition with this setup."

Very helpful.

 

[Bill Norris]

Flash Hole Size

#53 = 0.0595”, works with the original 6BR & PPC flash holes, may be too small for cases like Lapua’s 308 Palma brass. I shoot that, uniform flash holes w/ K&M small primer tool @ 0.0625” or 1/16”. I also uniform flash holes to 1/16", but I use a Sinclair flash hole reamer; it makes it easy to...

forum.accurateshooter.com

Great info

 

[Ned Ludd]

FWIW - .223 Rem brass uses the larger (2 mm) flash hole. .308 Win Palma brass typically uses the smaller 1.5 mm flash hole. I can easily imagine why using the smaller flash hole in the much larger .308 Win case might lead to ignition issues in colder temps, considering how much larger the case capacity is compared to .223 Rem cases. I just started using Alpha .308 Win SRP brass with the larger flash hole after years of using Lapua. It's still very early in the load development process, but the ES/SD values I'm getting with the Alpha brass and the larger flash hole using Varget and Fed 205s are every bit as good as with Lapua brass, and my suspicion at this point is that the ES/SD values will be even lower with the larger flash hole. In the limited testing with the Alpha brass I've done so far, I'm seeing regularly ES values of 4, 5, and 6 fps for 5-shot strings, something that would have been an extremely rare event in my hands with Lapua brass, if it happened at all. Although it has been possible in the past to regularly generate ES/SD values in the 8-12 fps range in the past with Lapua brass for 5-shot strings, I don't recall ever seeing ES values of 5 fps or below. I feel comfortable opining at this point that I don't think the ES/SD values with the larger flash hole Alpha brass are going to be any higher than with Lapua brass. Whether they are routinely smaller will require significantly more testing.

In fairness, because there are other differences such as case wall thickness and internal volume between Lapua and Alpha .308 Win SRP brass than just the diameter of the flash hole, even much greater sample sizes with the Alpha brass will not prove the larger flash hole is primarily responsible for any lower ES/SD values I may observe in the future. My gut feeling is that the flash hole size should certainly a contributing factor; however, that is only my feeling. If someone were interested and sufficiently motivated, they could simply enlarge the flash holes in several pieces of Lapua Palma brass to 2 mm, then compare ES/SD, velocity, etc., directly against cases from the same Lot # having the smaller flash hole, which would be an apples-to-apples comparison.

 

[Bill Norris]

Would be very interesting to see the results of further testing no doubt. Thanks, Ned.

 

[Mulligan]

Searching for any test results from SRP Small Flash Hole vs. SRP Large Flash Hole. Didn't see anything from a search. Anybody have any info ? Reason being Alpha SRP brass has the large flash hole. First time I've seen that combination.

Alpha 6BRA brass

So anyone that received these put them through the paces yet? Any range data yet from them

forum.accurateshooter.com

@Bill Norris
This thread my be helpful.
CW

 

[lawman29]

In the link posted by Mulligan you'll find that Tom and Alex partnered with Alpha to conduct flash hole testing. My understanding is that Alpha would be responsible for "publishing" results. There is a bit of a hint in the thread...

 

[rjtfroggy]

No testing so no scientific results but I have been opening all my new brass to 0.072 (drill) as my first step and have had no ignition problems as of yet. about 5 years as of now.

 

[Bill Norris]

Well, looks like if anything at all the larger flash hole with a SRP is a help mostly.

 

[tom]

Bill,

I will resume my tests once our match season is over. I was able to get started in about as cold of temperatures as you could find. No size had any issues in the headstamped 6 BRA cases. Honestly the most impressed I was with the smallest I tried was on the coldest of the days. Lol

And my testing when finished, will only include 6 BRA cases. There's a lot for me to tackle, such as comparing them tuned on different powders/primers, of which none have been done yet. I had got just far enough to tell that h4895 would be competitive in the smallest AND the largest I tried so far.

Since that time @GlennK has shot 4 ibs 1,000 yard records with the srp large flash hole 6 BRA alpha brass, if that helps your confidence.

Tom

 

[Bill Norris]

Bill,

I will resume my tests once our match season is over. I was able to get started in about as cold of temperatures as you could find. No size had any issues in the headstamped 6 BRA cases. Honestly the most impressed I was with the smallest I tried was on the coldest of the days. Lol

And my testing when finished, will only include 6 BRA cases. There's a lot for me do tackle, such as comparing them tuned on different powders/primers, of which none have been done yet. I had got just far enough to tell that h4895 would be competitive in the smallest AND the largest I tried so far.

Since that time @GlennK has shot 4 ibs 1,000 yard records with the srp large flash hole 6 BRA alpha brass, if that helps your confidence.

Tom

Yea, I had seen that post somewhere on here @GlennK. I feel good about trying the Alpha brass out in my 260AI.

 

[mgunderson]

I believe the Starline 308 srp brass has a large flash hole. It will produce very similar velocities to lapua srp Palma brass. Never been interested enough to figure out if it was case volume or flash hole size controlled.

 

[watercam]

Very helpful.

Having shot matches in temps down to 9ºF with .0625" primer flash holes, I don't worry about ignition with my Lapua SRP brass.

 

[boltfluter]

I believe the firing pin hit, for lack of a better word, may be as important or more so than a small flash hole in cold weather. Had the dreaded "click" several times over the years coyote hunting in single digit weather! Not a good sound!

Paul