Thoughts on small rifle primers being used in .284 brass

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Norm
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Thoughts on small rifle primers being used in .284 brass

#1 Postby Norm » Tue Oct 18, 2016 9:47 am

What are peoples thoughts on .284 brass being made to take small rifle primers?

I used Bertram brass last weekend with great success in the Victorian Teams matches and was very impressed with it. Following this there was some discussion on making some .284 prototype brass to take small rifle primers.
This would make for a very strong cartridge base but would it cause ignition issues?
I know that .308 palma brass ignites ok with around 46gn of powder and can withstand higher pressure. I have run a 7-08ai with palma brass and 49gn of powder ok.

Has anyone had any experience with small rifle primers being used in a cartridge that uses around 50gn to 53gn of powder?

BATattack
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Re: Thoughts on small rifle primers being used in .284 brass

#2 Postby BATattack » Tue Oct 18, 2016 12:22 pm

Could you just offset the potential small primer ignition "problem" by using a small mag primer?

Effectively your still using a mild primer in a large case so ES may not be affected in the same way as using a mag primer in a 223 case for example.

williada
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Re: Thoughts on small rifle primers being used in .284 brass

#3 Postby williada » Tue Oct 18, 2016 12:33 pm

Firstly, congratulations for producing a leading and solid effort in the Gippsland FO Victorians Teams win with those cases. It would certainly be a marketing coup if they worked with small primers to get greater case life in the .284's and Shehanes. My suspicion is that with slower burning powders in a long they case may not give optimum ignition. In two .308 rifles using Palma small primer cases in the last few months I found 2206h was better than 2208 using HBC's. The latter being the slow burning powder. Of course slower powders again are used in .284's and wildcat versions.

However the suspicion is not proven and until it happens we will never know unless special cases are made or someone with the correct technical expertise can modify a bigger primer pocket with a press insert to examine the merit of the concept and also examine the flash hole size required to light up the powder column. Then the concept could be placed before the manufacturer for consideration. Would love to think Australians could be recognised for both case and bullet manufacture so we could become leaders rather than takers.

Also congratulations to the Gippsland FS team too who won their section. FClass shooting is live and well in Gippsland.

Brad Y
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Re: Thoughts on small rifle primers being used in .284 brass

#4 Postby Brad Y » Tue Oct 18, 2016 4:11 pm

I used to run 2209 in palma based 260 improved cases. A queens was won here with a 7-08ai using the same combo. However those running slower powders have struggled with these sorts of wildcats and Palma cases. I believe the 308 on 2208 and these wildcats running sub 50gr charges on 2209 would be the limits of consistent ignition with small primer brass. I know mine was very hot/cold on 2213sc with the small primers. Lucky I get on well with 2209.

The 284 being that bit larger would really struggle unless you use a really hot primer like the rem 7.5 or a cci450 at a stretch. Even then in my opinion it would be touch and go, and on a cold Victorian day you could be in trouble.

I think the 284 and its wildcats are already more than good enough to do what is needed with large primer cases. We know well enough what they can handle and if we want to push harder we know to move to magnum cases and go from there.

Tim L
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Re: Thoughts on small rifle primers being used in .284 brass

#5 Postby Tim L » Wed Oct 19, 2016 1:35 am

I've been running 308 palmer and 2209 for nearly a year. Easily 1000 rounds and no misfires, in fact nothing but progress in reducing elevation. I leave the flashhole small and use cci br4 primers.

The very reason I use palmer and sr primers is to reduce the variation the primer can impose. I want to ignite the powder, then have a nice even flame propagation so it's the powder doing the work, not the explosive in the primer.

This is 500m 6 shots into the bottom of the x ring, one click up and 4 shots across the top. I'm rather pleased with that from the elevation perspective, shame about the windreading :(
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BRETT B
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Re: Thoughts on small rifle primers being used in .284 brass

#6 Postby BRETT B » Wed Oct 19, 2016 12:44 pm

For the better part of 3 years and using probably 5 barrels I was running Palmer Brass in my 260AI. I ran powders ranging from 2209/2213/2217/ VVn160/VVn165/R19/R22. For Primers I was using CCI 450/BR4 and federal GM205. I had mixed success during this time and realised there was an issue with my rifle not being consistent week to week. I decided to go back to basics and collect some good data and found very quickly that I was not getting consistent ignition.I changed the usual measurements on the case , e.g. neck tension/annealing etc, I even went to the extreme of using 3 different firing pins assembly's and all produced the same results of inconsistent ignition and it would correlate with ambient temperature of the day. Basically my extreme spreads would dramatically change from day to day and I had no idea why !! I then discovered after doing some extensive chrono work ( 2 magnetospeeds were used) that the small primer was very sensitive to temperature. I then tested 2209/2213/2217 all on the same day through the same barrel with same components and discovered the slower the powder burn the higher the extreme spread would be. This got me thinking that because I was using a slower powder with a smaller bore (6.5mm) in the 308 case that It may cause me an issue. With the success of the Palma Brass in the 308 with 2208 it was hard for me to believe that there would be an issue using it in a .260 but my data was showing starting to show me otherwise!!.
I decided then to get some Large rifle 260 brass and compare it to the Palma over a chrono using identical component in the same barrel. After 3 weekends and over 300 rounds to my disbelief i found the small rifle primer was the issue!!
I found 2209 to be the most stable with Small rifle in regards to ES/SD( around 20 fps) but I would get and increase in avg speed from morning to afternoon of over 50fps. As I got to the slower 2213/2217 loads my extreme spreads would range from 15-85 fps depending on time of day and temperature. When I used the Large primer brass it was consistent during the whole day and the ES/SD would rarely be any worse than 15fps. Over the next few weeks every time I went to the range for a club shoot I would take 24 round of Palma and Large rifle Brass loaded with identical components and shot through the same barrel to see if the difference would appear on target. It was clear very quickly that the Large Primer was more consistent than the small primer so now my days of using Palma brass in my 260 are Finished!!

I truly believe that there is NOT an issue with Palma Brass in the 308 and I know some have used it with great success in 7MM/08 with 2209 but I can say with good confidence that the small primer is not enough to light up a 6.5mm barrel with medium to slow burning powder. I was very disappointed with myself that it took me so long to find this issue with my rifle but it did teach me a valuable lesson when it comes to finding a problem with a rifle that is inconsistent, TRUST THE DATA in front of you!!!

To Answer Steve's original question I believe it would not be beneficial to the 284 but that is just my opinion !!
BRETT BUNYAN F CLASS OPEN SHOOTER W.A.

DaveMc
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Re: Thoughts on small rifle primers being used in .284 brass

#7 Postby DaveMc » Wed Oct 19, 2016 2:50 pm

Quick question - do you see velocity climb through the string?? And too much variation with change in temps?

if so you have probably not got enough ignition.

In a lot of testing of various cases (7 barrels with pressure strain gauges) it became quite clear when the primer was getting consistent ignition. This cannot be measure by elevation on a short range target (<800m) on a given (single) shoot. as a climb in velocity can still see you holding good elevation.
Playing powder rates and primer combos was very interesting :?

BRETT B
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Re: Thoughts on small rifle primers being used in .284 brass

#8 Postby BRETT B » Wed Oct 19, 2016 4:40 pm

Dave , I did see a lot of velocity climb through the string but the level of climb varied with outside Temps. I did most of this testing at my Benchrest range so in the morning it would be quite cool say around 5-8 deg C . By afternoon it was around the 20-24 deg C. I dont have my Data on hand but I do remember when I was testing 2213 that first thing in the morning I was getting around 2890 for the first 4-5 shots then it would climb to around 2920 as the barrel warmed up, wait until afternoon and that number jumped to 2960+. This started to show me the primer didn't have enough spark to burn it all and needed some heat . When I put a large primer case in with same charge it started off with 2955 in the morning and around 2965 in afternoon . I would then come back the next day and repeat the process and get the same result..
BRETT BUNYAN F CLASS OPEN SHOOTER W.A.

johnk
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Re: Thoughts on small rifle primers being used in .284 brass

#9 Postby johnk » Wed Oct 19, 2016 6:37 pm

What percentage load density are we talking about here? Would I be correct suspecting that the further away from 100% or mildly compressed loads in a case we get, the more problematic it is to light up charges consistently & efficiently?

Norm
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Re: Thoughts on small rifle primers being used in .284 brass

#10 Postby Norm » Wed Oct 19, 2016 8:14 pm

Some excellent answers and some excellent information.
Thanks to everyone who posted.

With the .284 I mostly use AR2209 which seems fairly easy to ignite. So it will be interesting to see how the SRP cases go in a direct comparison with this powder. With slower powders I think it would be a similar situation to the .260ai.

Time will tell and there is only one way to find out. So when I get some test cases I will run a side by side comparison with standard brass.

Dave if I have enough, I will fling a few your way to play with.

williada
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Re: Thoughts on small rifle primers being used in .284 brass

#11 Postby williada » Wed Oct 19, 2016 9:02 pm

Excellent work Brett. I like your approach to nutting out the issues. Like DaveMc, I used a pressure trace since 2002 to get a handle on what worked. In the end you gain an appreciation of what the groups tell you on paper. These days for convenience, I do a primer test while a new barrel is green before I engage in load development. That is how important I view the relationship of the powder to the primer is. The relative differences in group vertical at 140 yards reduces a lot of the variance. Dave's point about the primer variance showing up at long range is so true and the use of pressure trace is more sophisticated and but unfortunately very few people have them. So people take note of what Dave says and this is why weighing primers for shooting 1000 yards is important. You may do the testing at long range but that is very hard to achieve in terms of finding a suitable day. I have always nagged about crook primers doing people at 1000 yards with what I describe as a negative barrel.

In doing the primer test, I prefer 100% or slightly compressed load to ensure a full burn. Of course jammed bullets tend to give a complete burn too. The seating depth and muzzle timing may not be appropriate but it is a good starting point when you want to examine one variable at a time at a convenient short range. Yes John, I think many of us have noticed slower powders are more erratic with an air gap compared to faster powders. That old 2206 powder which I bet you have a supply of still was not as phased with an air gap in a .308. I would think the slower powder lit with a small primer in a case like a .284 with an air gap would present problems. The nodes with slower powders tend to be choppy anyway and so it is critical to get the right burn and as Brett has mentioned the velocity changes with temperature changes you would constantly be falling off a node. The best combination of powder and primer would have a better chance of keeping close to the node.

Primers subject to oil contamination, poor storage or different batches do create different scenarios. Don't buy them from a store that has a low turnover of stock. They need to be fresh.

Norm, the .284 case has not been adjusted to my knowledge but Brett's work and Brad's work suggest it would be a poor option. Also, from my hunting experience with magnums which require slower powders there is a definite benefit in having a large jump which effectively enlarges the chamber to absorb the pressure spikes of primer and powder in a long powder column to produce a sustained and even pressure. Otherwise it is like lighting a spitting wick and if the powder is stale there are further problems.

The design of modern squat cases and the circulation of gases in Ackley-like chambers on shorter cases have a different pressure profile and as such the powder is more easily lit. A few people have adapted the flash hole to create an internal bevel with a reamer so the primer spatter is directed in a cone towards the intersection of the case body and the shoulder of the squat cases to promote an efficient burn.

Brad Y
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Re: Thoughts on small rifle primers being used in .284 brass

#12 Postby Brad Y » Wed Oct 19, 2016 11:19 pm

BRETT B wrote:Dave , I did see a lot of velocity climb through the string but the level of climb varied with outside Temps. I did most of this testing at my Benchrest range so in the morning it would be quite cool say around 5-8 deg C . By afternoon it was around the 20-24 deg C. I dont have my Data on hand but I do remember when I was testing 2213 that first thing in the morning I was getting around 2890 for the first 4-5 shots then it would climb to around 2920 as the barrel warmed up, wait until afternoon and that number jumped to 2960+. This started to show me the primer didn't have enough spark to burn it all and needed some heat . When I put a large primer case in with same charge it started off with 2955 in the morning and around 2965 in afternoon . I would then come back the next day and repeat the process and get the same result..


See that's why you shouldn't stuff around with 2213... 2209 is all you need (insert shit stirring emoticon here)

I agree with Brett's findings, though with 2209 I never had an issue though my case was not a true ackley improved design. I think 2209 is probably the limit of powder burn rate that would work but still open to the effects of climate. Remember also there will be a difference between 43-45gr in a 260ai and 50gr in a larger case. I think there's enough experience to say it's probably not worth the investment of getting the sr primer cases made for the 284.

Norm
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Re: Thoughts on small rifle primers being used in .284 brass

#13 Postby Norm » Thu Oct 20, 2016 12:22 am

Brad,
You are most likely right but I will still have a play .
It is a great opportunity to gain some personal experience in an area that has seen little experimentation.

The size of the flash hole may have a large bearing on the results so some experimentation in that area is also possible. I might get some without flash holes and drill out the flash holes in increasingly larger sizes to see what effect that has using the same pieces of brass.

I know from our testing of Dasher brass that the flash hole size is critical in controlling back pressure on the Small Rifle Primer and too large a flash hole, results in dangerous pressure on the primer cup. Cup blowout will result.

Tim L
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Re: Thoughts on small rifle primers being used in .284 brass

#14 Postby Tim L » Thu Oct 20, 2016 12:24 am

Are we sure we're nailing these velocity differences down to the right cause?

Has anyone considered bullet weight as a contributing factor?

A 260 (6.5) at 130/140gn may be getting a bit of a head start on itself, ie getting ahead of the pressure, which then needs to build up again to continue to accelerate the bullet. It would look like partial ignition because it would be, but not due to the primer.

I'm not sure what the burn looks like, but I'd bet it doesn't happen in the case. If you blast that slow burning powder into the bore and loose the pressure to sustain the temp that sustains the burn, you will have just the scenario described.

The 200 and 215s in a 308 are a little more difficult to shift, and I'm at 110% fill with 2209. I have noticed a distinct reduction in recoil for the same velocity. It's more a smooth push than the usual stab from a heavy 308.

Just a thought.

williada
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Re: Thoughts on small rifle primers being used in .284 brass

#15 Postby williada » Thu Oct 20, 2016 9:53 am

Tim the answer is, “Yes”. The experimental setups a few of us have used set tight parameters to analyse one variable at a time to test a hypothesis statistically. This requires groups of paired barrels of different dimensions, a control group of match ammunition and in my case a machine rest to take out the human factor in the recoil which can alter velocity as much as 25 fps.

The sort of equipment used to verify the quality of the ammunition included:

1. Scientific scales to measure the weights of the components.
2. The bullets were batched by base to ogive length, body length, boat tail length and angle and the jackets and core were subject to internal concentricity measurements on a Juenke machine as well as jacket hardness measurements which can vary the friction and gas seal. Cases were volume sorted
3. The use of an infrared temperature gauge measured when the barrel was at operating temperature and use in conjunction with a Pressure Trace attached to the computer we mapped the pressure profile of each shot, compared it with a group of traces and also look at appropriate barrel lengths for the powder being used. This system quickly picks up the primer variable and suitable barrel lengths. Each shot was released at the same time interval.
4. We used two chronographs and a density altitude meter.
5. Identified the barrel compensation profile to get a closer match with simulated computer results as well so the SD’s were meaningful.
6. Repeated the tests time and time again.

Just as an observation, the target is usually big enough to accommodate the typical variances shooters have with their reloading if they can read conditions so people should not think they need all the above mentioned equipment. But what the experiments do allow us to do is explain why a shot went there.

The competition is so hot today, the lessons need to be imparted to create a level playing field and while we have a good waterline, it’s that odd shot or outlier that can do you. That needs to be eliminated where possible such as those corner shots I have talked about and one I see on your target assuming it was not a sighter.

One final point about mid distance testing, an elevation spread is not bad if the rifle is positively compensating and still holds the scoring ring and is least wind sensitive. It will be better out further. Many people think that a tight spread at mid range is great, but the heavy barrels we use have a tendency for the mid distance to be a point of compensation. Remember, past a point of compensation the vertical falls away in the form of negative compensation and poor primers will find you out with further distance. You simple have to identify the barrel profile and load accordingly to get the best from it and don’t use it at an unsuitable distance.

Further improvements on group can be made with low SD’s IF reflected vibrations are not interfering with muzzle shape and the barrel is of the right harmonic length to match the powder and primer. Of course the throat angle will have a bearing on ignition and velocity as does seating depth.


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