Home Forums Hunting & Shooting Ask The Gunwriters Strange Velocities

I have a Ruger #1A with a 23” custom barrel that has been producing unusual velocities. It typically registers 50 to 100 fps over maximum specified velocities when I’m still 1 to 1.5 grains under the max powder charge in the manual. For instance, the Speer #14 manual lists 2795 fps for the 145 gr. bullet and 52 gr. of RL19 but I’m seeing about 2860 with a charge weight of 51 gr. This was originally recorded on my Caldwell Ballistic Precision chronograph. Thinking that the Caldwell was screwy, I purchased a MagnetoSpeed Sporter (which I had been coveting for some time😁). Lo and behold, when I shot this load simultaneously over the MS and through the Caldwell the MS confirmed what the Caldwell had been telling me all along. I tried several other loads with the same bullets but different powders and got similar results - higher than expected velocities.
The difference between my loads and the ones in the manual are that I’m using Prvi brass and Fed 210 primers as opposed to Rem brass and CCI 200’s. Of course, the OAL is different in keeping the jump to the lands at .03”.
With other rifles, I’ve always been used to not getting the same velocities (usually less) as the manuals claimed, so this it totally new to me. Has anyone else encountered something like this?

Wear glasses (possible blown primers). Watch for pressure signs.

Closer to the lands than in Speer's test rifle?

PRVI brass heavier than Remington?

Bore of your custom barrel tighter than Speer test rifle?

Yes..three times...all with PAC-NOR barrels. They are very tight. With the 7 Wby mag, I started below listed charge weight, had prior experience with an 8x57 barrel. The Chrony is your friend. Listen to it.

Yep, common with custom barrels--some makes more so than others.

Also, it may have a shorter than standard throat. From the load you mentioned in the Speer manual, I deduced it's a 7x57. Throat dimensions can be all over the place in 7x57s, but for custom-barreled rifles, gunsmiths often use reamers with shorter throats, which give bullets less chance to tilt a little before entering the rifling.

Neglected to say it’s a 7x57.🥴

No indications of high pressure other than the high velocities. Nonetheless, as velocity is usually indicative of pressure, I intend to back off to 2800 or a bit less.

Bobber,

I'm no gun writer and no expert. I have a rifle (factory barrel - not custom) that performs similarly. I hit max velocities at mid-level powder charges per the manuals. Trust your chronograph.

I haven’t tested cases for water capacity however I did weigh some PRVI and Rem cases and the PRVI’s came out considerably lighter. (161 vs 186).

I’m thinkin’ it has to been a tight bore.

Definitely not a short throat. The 145 Speers are the shortest bullets that it will take while maintaining a .03 jump to lands and still have an acceptable seating depth in the neck. Even at that, there’s only about a .213” grip.

You’re right. I have to admit, I was initially having doubts about the Caldwell until the MS confirmed it. I highly doubt that two totally different Chronos would err by the same about.😁

I'd bet it is a tight bore. I've also read of guys who had to bump up their favorite handload a bit when moving from a custom barrel to a factory barrel, claiming the factory bore was "looser" and needed a higher charge to make the same speed.

On the other end of the spectrum, I have a Lilja-barreled 24" 7mmRM that was really slow with book loads. The throat on that rifle is super long, almost like a 7mmWby. When I worked up to typical upper-end 7mmRM velocities, I was using charges approaching 7mmWby data. One load manual indicated I was something like 7gr over max, although 7mmRM data at the time was all over the place when looking at charges. I've been shooting those loads for years now with no issues (160s at 3,000fps with RL22).

I guess, as the old saying goes, “Every rifle is a law unto itself.”

I have the same problem. more or less with a custom based on an FN commercial Mauser. It was originally chambered to the .270 Win. so I know ir should handle fairly stout 7x57 loads. I have a Winchester M70 FWT and Ruger #1a in 7x57 an either one works just fine using 7-08 data. (Loads were very carefully worked up over a long period of time Usually in the very hot summer months.) No pressure signs and brass has lasted for more that five loading with primer pockets still reasonably tight.

The throat on my custom was ordered to be the standard European length as my plan was to see what the rifle wouls do with 170 gr. round nosed bullets. I have a decent supply but my first work ups were with 140 and 150 gr. bullets to settle the rifle in and get a feel of what it may like and dislike relative to pressure. Probably gonna have to take it back to the gunsmith and have him check out that throat plus another potential problem. Check out the latest Speer manual if you haven't already done so. They have a few loads that will make you look twice. All I will add is the #1 and M70 will easily snap at the heels of the .280 Rem. with no apparent pressure problems.
Paul B.

The angle of the sun can really play games with chronographs.Since you confirmed your Magnetospeed is running nearly the same,I say your throat is the issue.The closer the bullet is to the lands the higher the pressure and velocity your likely to see.Add a little erosion build up and it's going to increase even more.I have a 300WSM.I had to load 165gr bullets like they were 180gr bullets.My velocity was what I should have been getting,but I had to load about two grains less powder than what the books showed for that weight bullet.I fire lapped that barrel and it did change things a lot.My loads dropped about 100fps.For the first time with that rifle I could load like the books showed for the specific weight bullet.Seating a little deeper can make a big difference,especially if your at the max in your load.This will explain what may be happening. https://www.hornady.com/team-hornady/ballistic-calculators/ballistic-resources/internal-ballistics

Smart guy, right here!

Knowing that high velocity usually indicates high pressure - WIN!
Knowing that two chronographs agreeing on velocity - WIN!

Well done, Sir.

Personally, I knew a lot more about reading "Pressure Signs" before I actually conducted pressure testing according to SAAMI recommendations (or thought I did). My experience actually testing led me to pull apart my favorite 25-06 loads and reduce the powder charge.

I've blown up a fair number of firearms. Then only unintentional one was when I was 16. That was what I like to refer to as a "Significant personal event".

The extra fps are not worth the risk to me.

Buford. Thanks for the compliment. I fully agree that a few extra fps aren’t worth the risk.
As my favorite powder (RL19) for the 7x57/145 Speer HC is presently not available, I’m now working with Accurate 4350. So far, I’ve only completed the chronographing. Again, the velocities maxed out at 1-1/2 grains short of the Speer manual specs, with an average of 2788 fps. with 49.5 grain. (Speer calls for
2792 with 51 gr.)
On my next range session I’ll be trying 48.5 gr. (2747 fps), 49 gr. (2765 fps) and 49.5 (2788 fps). If I can come up with something that will consistently give me 1.25” (or less) at 100 yds. I’ll be perfectly satisfied. After all, this rifle/bullet combo is intended for deer hunting at ranges of 300 yds. or less (usually much less) and experience has told me that a 145 gr. HC launched anywhere between 2700 and 2800 is deadly on any deer that’s ever munched an alfalfa sprout.😁

Here are few examples of how much the powder capacity different brands of brass can possibly affect velocity and pressure.I used Hunter powder for this example because it's a powder I would use for 30-06 loads and also because it's a ball powder and I can get a more accurate case fill.It also a good way to get an idea of just what is the full maximum case capacity for the powder your going to be using.The cases I used were Remington 30-06,case weight was 200grs,Lapua 30-06,case weight was 194.8grs and Winchester 30-06,case weight 190.1grs.I filled the Remington case full of powder and that weighed 67.5grs.I then dumped the 67.5grs into the Lapua case and then into the Winchester case.You could see the Lapua and the Winchester case would hold more powder than the 67.5gr charge that filled the Remington case full.How much more?I could put two more grains of Hunter powder in the Lapua and Winchester case to fill the cases completely full.How many grains of powder you can get into a case will vary because powders are different.Some powders are heavy per grain volume and some are much lighter per grain volume.I could have never been able to get that many grains of an extruded powder because of more air space between the grains of powder.So I looked at Western Powders load data for a 30-06 using Hunter powder.They also used a Remington case for their load data.The heaviest charge they had was 68.6grs of Hunter with a 115gr Berger FBT bullet.Their Remington case must have had a bit more case capacity because mine was full at 67.5grs.I could have held that charge in the Winchester or Lapua cases I have,but it would have been a really compressed load to seat a bullet in a full case of ball powder.Hunter wouldn't be my choice for a bullet that light.I would rather use it for bullets around 150gr or higher.64.0grs will put the powder about the bottom of the neck.That's near what Western's shows for 150grs bullets and it will give plenty of room for seating the bullet.

67.5grs of Hunter in Remington 30-06 case


67.5grs of Hunter in Lapua 30-06 case


67.5grs of Hunter in Winchester 30-06 case

Strange indeed. Some rifles are just mysteries. I have a tang safety Model 77 in .338 that would not shoot 250 gr. NP's over 2550 fps. Jim Carmichael touted the 68 gr. load of H4350 as good for 2700 fps in the .338. I couldnt make it happen. Started at 65 gr. and worked up to 68, no pressure signs, chrono said 2550. The truly mysterious thing then is that I worked up a grain at a time to 71 grains when the primers started to flatten a little. No change in velocity--2550. So I changed bullets to the 210 NP and right off the top got 2910, just as the book said I should. Then loaded up the new 225 NP (this was in the early 90's and no loading data had yet been published for the bullet) and worked up to 72 gr. with 2830 fps on the chrono and no pressure signs. All loads were at or under an inch and a half. Why would a barrel shoot two lighter bullets to predicted or at least reasonably fast velocities, but not budge past 2550 with a 250 NP? Cartridge OAL was the same on all three bullets. All I could figure was that it must have something to do with the long bearing area of the heavier bullet in this particular barrel. Whatever, I gave up on the 250's and was perfectly happy with the 225's for the next 20 years. Some mysteries are not worth the effort to solve.

Limapapa.
I’m thinkin’ that your diagnosis concerning the long bearing surface on the long bullet is very likely correct.
I agree that some mysteries just ain’t worth the effort and angst. Sometimes one is better off to just accept that “it is what it is” and move on to what works for them.🙂