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Effect of Primer Selection on Muzzle Velocity |
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britrifles 
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Joined: February 03 2018 Location: Georgia, USA Status: Offline Points: 8404 |
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 Topic: Effect of Primer Selection on Muzzle VelocityPosted: January 13 2025 at 4:31am |
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After having very good success with using the CCI BR-2 Primer in my .308/7.62 Converted No. 4, I decided to run a test with the BR-2 in the .303. My go-to primer for the .303 has been the WLR for many years.
I did not at all get the results I was expecting, velocities dropped considerably and standard deviations increased. Here is the results (all powder charges are Varget, PPU cases, 174 gr SMK seated to 3.07”), data collected with my Garmin XERO. All 10 shot groups. Charge Primer MV ES SD 40.3 WLR 2384 45 14 40.3 WLR 2380 47 15 40.3 BR-2 2340 105 34 40.6 BR-2 2357 53 23 40.6 BR-2 2354 53 20 40.9 BR-2 2382 86 26 40.9 BR-2 2385 89 26 The 40.3 gr BR-2 load with the high ES of 105 had one shot with a very low velocity. Deleting that shot brought the MV up to 2347, ES down to 78 and Std Dev down to 28. All charges were weighed to within +/- 0.05 grains on my RCBS electronic scale which I have checked with calibration weights. It would seem that the WLR is a hotter primer, equivalent to an additional 0.6 grains of Varget. My .308 Win loads are giving single digit standard deviations with 44.0 grains of Varget (168 gr TMK) out of the No. 4 DCRA 7.62 Conversion. It may be that the weaker BR-2 primer requires close to or at 100% load density to function well, particularly in cold/cool weather. Temperature was 40 to 45 degrees during the test. This was all related to my efforts to see if I can shrink the 600 yard groups in the No. 4 T. The T has a Long Branch CM4 six groove barrel fitted. |
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Sapper740
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Posted: January 13 2025 at 5:58am |
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That's an interesting result Brit, there's always so many variables when handloading for accuracy. I wonder what you would find if you tested primers from different case lots? I had an excellent recipe worked up for my LB using fireformed Dominion brass with Hornady 150 gr. SST bullets over Varget and CCI LRP. From a rest it would shoot 1 MOA. I eventually used up the 1000 primers in the LB and several other .303s I was reloading for and started with a newer case lot, same primer. I was never able to achieve the same accuracy again. Funnily enough, I have a chrono but seldom check each load's velocity, something that's going to change now that I'm retired and have more time.
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britrifles
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Posted: January 13 2025 at 6:26am |
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So far, I've only used BR-2 primers coming from the same brick of 1000. I have a second brick, which is probably a different lot number, purchased several years apart I think. I went thru the target plot sheets I made with this test at 600 yards. There was a definite correlation of vertical point of impact on the target to the muzzle velocity. So, I need to work at shrinking the standard deviations, certainly to get it down in the teens if not single digit. My plan is to see if increasing powder charge will reduce standard deviation with the BR-2s. Also, will try seating the primers a bit more firmly, obtaining a slight amount of crush up. Reading others experience, this seems to be necessary with this primer. Of course, never good to change more than one variable while testing, otherwise you won't know which variable made the difference. |
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gilgsn
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Joined: November 17 2023 Location: France Status: Offline Points: 93 |
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Posted: January 14 2025 at 2:24am |
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he!!o.
A couple weeks ago I loaded a bunch of .41 Magnum rounds for my Ruger Blackhawk. I was getting short on large-pistol primers and used some from two different brands. At the range I was surprised to see an increase of 100fps (4-5/8 bbl) with one kind of primers. I remembered that I had some troubles seating them and told myself I would not buy that brand again... Recoil was sharp and the trigger guard dug into my index finger, drawing blood. Well, it turns out that the second box of primers I grabbed was actually large-rifle primers I use for .303 in my No5! Not making that mistake again! Primers can make a big difference, especially the wrong kind... Gil.
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britrifles
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Posted: January 14 2025 at 5:42am |
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Worse if you had done that the other way around. LP primers have thinner cups than LR and can pierce at the higher rifle cartridge chamber pressures.
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britrifles
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Posted: January 14 2025 at 4:20pm |
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Some might ask “why worry about velocity Extreme Spread and Standard Deviation”? The answer is found in the target below. This was one of the 600 yard targets I shot while collecting the chrono data recorded in the first post above. It is one of the 40.6 grain Varget loads with the BR-2 primers.
 A Vintage Sniper match score of 96-6x at the 600 yard stage is fairly good, but why the two low shots in the 8 ring (shot #3 and #4)? Well, upon reviewing the data, those 2 shots were the lowest recorded velocities of the ten shot string. And upon reviewing the data for the other 5 groups, low velocity shots always impacted low on the target. Same was the case for high velocities, they appeared high in the group. That might all seem obvious, but the vertical spread caused by a 50-80 fps velocity variation is more than I would have expected. And, this does not appear at 300 yards. I wonder if shooting this rifle off of a sandbag (rather than prone in the sling) is having a negative effect on muzzle jump, such that velocity variations are not affecting the angle of jump, or minimally affected. When shooting the No. 4 prone, we often find that the fast bullet leaves the muzzle at a lower angle of jump which has an elevation point of impact compensating effect at mid and long range (meaning slow and fast bullets impact the target at about the same elevation). Maj Reynolds wrote about this and had been involved in tests that determined the angle of jump while he worked at RSAF Enfield. I have more testing to do to close these groups up, and I won’t stop until this rifle holds the 10 ring at 600 yards. That’s a match winning rifle. I would like to live to see the day that a No. 4 T wins the US National Sniper Match, or at least one of the significant regional matches. |
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Shamu
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Posted: January 14 2025 at 4:23pm |
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I'd say it depends on whether you're using the sling equally at the two different ranges?
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Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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britrifles
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Posted: January 14 2025 at 5:28pm |
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Not using a sling. This match is shot off of a sandbag rest in the prone position. I do have the option of shooting prone unsupported with a sling.
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britrifles
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Posted: January 17 2025 at 4:45pm |
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I completed a series of definitive tests today to try to isolate the cause of vertical dispersions at 600 yards with the No. 4 T. I had suspected that the reason was entirely due to variation in muzzle velocity. Today’s tests confirmed that suspicion.
For the test, the basic load data is: PPU Case WLR Primer Varget (ADI AR2208) all charges weighed 174 gr Sierra MatchKing Five rounds each were loaded and fired with the following charge weights: 40.3, 40.6, 40.9, 41.2, 41.5 grains. All weighed on RCBS Range Master 750 Digital Scale checked for accuracy with calibration weights I fired one shot of each charge in sequence at the same target, recording muzzle velocity and plotted the point of impact carefully. Then repeated this in a round robin style test for a total of five shots of each charge weight. Overall, for the 25 shots, the velocity statistics were: MV 2417 fps ES 118.6 fps SD 29.4 fps That’s not actually too bad for 1.2 grain variation in charge weight. Here are all 25 shots on the target monitor shot on the US NRA Mid Range (MR) Target:  I then plotted the individual shot elevation (MOA) from the center of the target bull with a “0” value as the reference elevation against he recorded muzzle velocity. I did not change any scope elevation or windage settings through the course of the 25 rounds. Here was the smallest 5 shot group, 40.6 grains of Varget, under 1 MOA center to center. Elevation spread was under 1/4 MOA. Muzzle Velocity 2389 to 2427 fps. This was shots #2, 7, 12, 17 and 22 of the Round Robin 25 shot test. I made one plot sheet per individual charge weight load.  Perhaps not unexpected, there is a strong correlation of elevation point of impact on the target with muzzle velocity. But, oddly, most charge weights exhibited significant muzzle velocity variation. Here are the individual charge weights mean velocity and extreme spread: Charge MV ES 40.3 2379 53 40.6 2408 38 40.9 2414 55 41.2 2439 53 41.5 2446 32 The plot below shows all 25 shots and a linear trend line thru the data. The slope of the trend line shows a 0.3 MOA elevation rise for each 10 fps velocity increase. If I can keep the velocity Extreme Spread down to 30 fps, that would keep the elevation spreads to within the height of the X ring (1 MOA) with perfect aim. In practice, that should keep all shots within the height of the 10 ring which is my goal.  It’s quite clear to me that my trouble with 600 yard groups holding the 10 ring is because of excessive velocity variation, even when charges are all weighed. In the range of 2385 to 2420 fps appears to be a flat spot where elevation is not changing much with muzzle velocity. Elevation seems to jump up above 2460 fps, but I’d need more testing to prove that. This might be due to the barrel and rifle moving out of the accuracy node. Now to find and correct the causes of muzzle velocity variation. I need to get the Extreme Spread of muzzle velocity down to around 30 fps based on this data and target a mean velocity of 2400 fps to get on that flat spot. A 30 fps ES may be expecting too much from this barrel. I weighed all the fired and deprimed cases in order they were shot. There was no correlation of case weight with muzzle velocity. Next shoot I will do an another Round Robin test loaded to 40.6 grains but vary bullet seating depth. |
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Strangely Brown
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Posted: January 18 2025 at 6:22am |
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A take on primers from across the pond: The 2019 Bisley Imperial threw a new light on primers for all the wrong reasons. It started with my own club's army open meeting with the issue of GGG 155gr destined for the miliary but issued for the May meeting, two months before the main Imperial meeting and the Queens Prize. Shooters started to notice extractors being broken on such rifles like Swings, Barnard's, Gruenig+Elmiger and others. Whilst the NRA were aware of this it wasn't until GGG delivered the ammunition for 2019 Imperial that the fireworks started; we're talking broken extractors, and lots of them! I did a search a couple of hours back on a Facebook page which caters for Bisley shooters and found one post from a shooters who had 9 extractors break on him during the whole meeting! It was also noted that some shooters were experiencing 11 O'clock flyers. The final source o the problem after much experimenting was declared to be overly hot primers, some estimates put it at 20% of the quantity purchased. It's rather frustrating here in the UK that primers are still in short in supply although I have managed to get a 1000 Magtech recently and am only using the few RWS (Ruag) I have for competitions. Geoff, another great post of yours, although I had to read it twice to fully understand what was going on! |
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Mick
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britrifles
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Posted: January 18 2025 at 7:09am |
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Mick, I think we underestimate the effect primer choice has on both velocity and accuracy. I’ve never paid any attention to it, nor noticed any significant effect until tuning my long range load for the DCRA 7.62.
I assume the extractors were broken trying to extract a stuck case? I can’t imagine any other reason. Of course, a stuck case is a very good indicator of an overloaded cartridge. Nothing seems as simple as one would think. I really should have put this last post I did on the ladder test on the T to a different thread, as it was not really a test of primers. But, one wonders if primer consistency is a factor here of my large muzzle velocity deviations (at the same charge weight). One does of course expect velocity to go up with increasing powder charge, but what I experienced was large velocity variances at the same charge weight that are causing vertical dispersions at the target of 2 MOA, sometimes as much as 4 MOA! I’ve heard some long range shooters weigh primers, but I just can’t imagine that would be necessary to get ES down to 30 fps. Same for weighing bullets. |
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Mayhem
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Posted: January 18 2025 at 4:05pm |
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I've noticed an increase in V0 in my 6.5x55 when switching from CCI #200 primers to Winchester LRP. I don't have my notes with me at the moment but I believe it was around 80 - 100 fps on average. From memory, I was using 39.8gn of ADI AR2209 and 140gn Hornady ELD-M. Yes, I know - It isn't an Enfield
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britrifles
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Posted: January 19 2025 at 5:04am |
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I redid the Shot Elevation Point of Impact (POI) vs Muzzle Velocity plot so we can see each of the 5 different Varget charge weights as indicated in the chart legend. I’ve also reset the vertical axis scale so “0” aligns with the vertical center of the target bull.
The various horizontal lines represent the heights of the X, 10, 9 and 8 ring on the US NRA Mid Range (MR) Target.
Note the 40.6 grain load produced the tightest vertical spread, under 1/2 MOA. The dashed line is a linear trend line thru the five data points. Could well be a fluke and I need more shots to prove it out. A trend line thru these five shots shows no change in elevation POI with increasing velocity. That’s exactly what we want in a mid to long range load. So that will be the basis for further testing with bullet seating depth.  |
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Zed
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Posted: January 19 2025 at 12:31pm |
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Geoff. It is very interesting and educational to read your posts on reloading!
The 40.6 load looks very good. I hope all the hard work pays off in this seasons competitions!
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It's nice to be important, but it's more important to be nice!
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A square 10
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Posted: January 19 2025 at 12:38pm |
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has anyone tried these primers in the proper selection of coarse ?
Anyone tried these? I picked up 1300 for $65.00 out the door at my LGS [posted by someone on my SASS site]
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Strangely Brown
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Posted: January 19 2025 at 12:58pm |
I've not seen these in the UK, although given the proximity of Bosnia to the Ukraine that's hardly surprising. |
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Mick
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A square 10 wrote: