I woke up early that morning. It was only a few days after a historic blizzard passed through my state. Stir crazy, I couldn’t wait to get outside. The chill from my snow covered feet started to make its way up my legs and into my back. I shook vigorously from head to toe. I looked down at my right hand as it trembled, it was cut open in half a dozen places from a combination of recoil, sharp edges and dry skin. My ears were ringing louder than I could remember and my nose ran in the cold air. The gun and support equipment weren’t in much better shape. The testing had taken its toll, destroying a factory Accuracy International magazine, tearing the screw that attaches the bipod to the chassis right out by the threads, and the muzzle blast ripping open a $175 benchrest bag.
You’d think I was disappointed, however, there was a smile on my face. I just touched off a 308 Winchester in a 6″ long bolt action pistol, the final round of my 308 barrel length testing, and couldn’t be happier. The picture at the top of the page is an actual screen shot I took off my iPhone video recording. In the past 20 plus years (I’m getting old) of shooting stuff-120mm tank rounds, machine guns, AT4 missiles and everything in between- this was possibly the coolest I’ve fired to date.
Over the past few years, Rifleshooter.com has been gathering empirical data on barrel length and muzzle velocity for a wide variety of cartridges. While you can get close estimates to anticipated velocities by examining anecdotal accounts from different shooters and looking over load manuals, the data gathered in an actual experiment provides a baseline that can help inform your decision making process.
In 308 Winchester / 7.62x51mm NATO: Barrel Length versus Velocity (28″ to 16.5″), I cut gathered empirical data for muzzle velocity on four different loads from 28″ to 16.5″. Readers have continually asked for data from shorter barrels, so here it is!
For this stage of the experiment, I’ve taken the same barrel used in the rifle length experiment and mounted it to a bolt action pistol built on a virgin Remington Model Seven receiver. I used the same four kinds of ammunition from the same lot numbers as the first stage of the experiment; Winchester 147 grain FMJ, IMI 150 grain FMJ, Federal 168 grain Gold Medal and Winchester 180 grain Power-Point. Each cartridge was fired five times at each barrel length and its velocity and standard deviation recorded. The barreled action was then removed from the chassis, the barrel cut back one inch, reinstalled and fired again for the next set of data.
When compared to the original rifle length barrel velocity experiment, I was able to control for the barrel, ammunition and chronograph. Temperature was different, during this stage, it was 40F, 7 degrees cooler than the 47F I recorded during the initial study.
Initial testing was done on Remington 700 action in a rifle. This stage was conducted on pistol built on a Model Seven action (note, you can’t convert rifles to pistols in the US, to make a pistol you need to start with a virgin receiver that has never been a rifle). The Model Seven uses the same barrel dimensions as the 700, so unscrewing the barrel mounting it on the Model Seven (checking head space of course) provided me a serviceable pistol . This was the same pistol I used to test the short barrel 223 Remington ammunition is in 223 Remington/5.56mm NATO Barrel length versus Velocity- Short Barrels- 6 to 14 inches. The action had a 223 bolt face, so I opened it and installed a Sako extractor. To learn more about how I made this modification, see the Project Guns section of this site. The headspace on this pistol measured 1.630″ (SAAMI minimum), this was .003″ less that when the barrel was installed on the rifle (1.633″).
Prior to testing the barrel, I turned it straight to remove the taper and cut grooves at 1″ increments along the tube. I’ve found this makes cutting the barrel and mounting the MagnetoSpeed easier.
Built with parts from Brownells, the pistol includes:
- MDT LSS chassis– modified for use as a pistol
- Shilen 1:10 twist stainless steel barrel
- Timney 510 trigger
- Accuracy international AICS magazine
- Harris bipod
Velocity data was recorded with a MagnetoSpeed barrel mounted ballistic chronograph.
The contents of Rifleshooter.com are produced for informational purposes only and should be performed by competent gunsmiths only. Rifleshooter.com and its authors, do not assume any responsibility, directly or indirectly for the safety of the readers attempting to follow any instructions or perform any of the tasks shown, or the use or misuse of any information contained herein, on this website.
A summary of the data for all four cartridges is provided below
Due to ammunition constraints, data for the Winchester 147 grain FMJ and Federal 168 grain Gold Medal was gathered until 8″ and Winchester 180 grain Power-Point 9″. IMI 150 grain FMJ 7.62x51m NATO data was gathered down to a 6″ barrel length.
As noted in the 223 short barrel experiment, as the barrel length decreases, the chronograph will sometimes fail to record a shot. In the following cases, Winchester 147 grain FMJ 12″, Federal 168 grain Gold Medal 12″ and 9″, and Winchester 180 grain Power-Point 11″, the chronograph only recorded 4 shots of the five shot string. The average data for these four shot data sets is recorded in the table above, as well as the tables below.
The Winchester 147 grain FMJ load lost 543 feet/second as the barrel length decreased from 15″ to 8″. This was an average decrease of 77.6 feet/second per inch of barrel length. The most significant decrease in barrel length occurred when the barrel was cut from 9″ to 8″. This resulted in a velocity loss of 118 feet/second.
The IMI 150 grain FMJ 7.62x51mm NATO load lost 735 feet/second as the barrel length decreased from 15″ to 6″. This was an average decrease of 81.7 feet/second per inch of barrel length. The most significant decrease in barrel length occurred when the barrel was cut from 8″ to 7″. This resulted in a velocity loss of 137 feet/second.
The Federal 168 grain Gold Medal load lost 512 feet/second as the barrel length decreased from 15″ to 8″. This was an average decrease of 73.1 feet/second per inch of barrel length. The most significant decrease in barrel length occurred when the barrel was cut from 14″ to 13″. This resulted in a velocity loss of 106 feet/second.
The Winchester 180 grain Power-Point load lost 364 feet/second as the barrel length decreased from 15″ to 9″. This was an average decrease of 60.7 feet/second per inch of barrel length. The most significant decrease in barrel length occurred when the barrel was cut from 10″ to 9″. This resulted in a velocity loss of 94 feet/second.
What did you learn?
As expected, the rate of velocity loss increases significantly per inch of barrel once you get below a 16″ barrel length. Compare the above rates of loss to those found in 308 Winchester / 7.62x51mm NATO: Barrel Length versus Velocity (28″ to 16.5″), where the Winchester 147 grain FMJ averaged 24.6 feet/second per inch of barrel, IMI 150 grain FMJ averaged 22.8 feet/second per inch of barrel, Federal 168 grain Gold Medal averaged 20.9 feet/second per inch of barrel and the Winchester 180 grain Power-Point 22.5 feet/second per inch of barrel.
Do you see any use for a 10″ 308 Winchester?
No, personally, it seems like a silly idea to me. Based on my limited experience with the 330 BLK and 7.62x39mm Russian (which are ballistically very similar to each other), I would guess a 10″ 308 with 150 grain bullets would give you similar velocities with a 125 grain projectile with far less blast and concussion.
What are possible sources of error in your experiment?
The small sample size is always an issue. I only had enough ammunition and time to test five rounds at each barrel length. Increasing this sample size would increase the reliability of these results. For more on sample size, see the discussion here.
Did it really hurt to shoot a short 308 pistol?
Yes, it did. I’ve shot a lot of different firearms in my life and this wasn’t pleasant. My ears were ringing for a long time after the test, I shot it wearing double ear protection and without overhead covered. It was LOUD.
The brand new, factory AI AICS magazine also flew apart as few times. I actually had this happen on two different mags. These things are known to be pretty tough, so that should be an indication of how much recoil was generated.
The muzzle blast from the short barrel eroded away some of the chassis!
Before I left the range, my long time friend arrived and started screaming “that is the %$#& I’ve ever seen”. I offered to let him shoot it. He declined. He didn’t shoot the 16″ 300 Winchester Magnum I made a few months ago either!
Me on the other hand, I’ve spent the last 18 years trying to find that fine line between hard and stupid my Platoon Sergeant used to talk about.
What do you think of the MDT LSS chassis?
I like it a lot. Super easy to install and remove the action from the stock. Good ergonomics, and a great value for the money. Please see Modular Driven Technologies (MDT) LSS Chassis Review. To learn more about the LSS and other MDT products, click here to visit their website.
Is the file picture at the top of the page real, or photoshopped?
100% real. I used my iPhone to record a couple shots being fired in slow motion. Out of the 4 recording I made, only two frames contained muzzle flash. This was the best one. In the next frame you can see the gun recoiling (below).
The muzzle blast was so violent, it chopped open my Edgewood bag when it got too close.
How did the Sako extractor work?
Flawlessly. I had 100% extraction during the course of this experiment.
How did the Timney 510 trigger work?
Very well. I’ve been beating on the 510 and 517 for a while. No complaints, no problems. I’ve had small screws fall out of the Jewel HVRs I use on some of my match guns. These seem much more durable over the long run.
Do you trust the results from the MagnetoSpeed?
Yes, I do. I leave my Oelher 35P in the truck now. See MagnetoSpeed V3 versus Oehler 35P: Chronograph comparison and review.
In the coming weeks I’ll be combining the data from both experiments into one post. When that happens I’ll post a link there. Until then, stay safe.