April 6th, 2018

TECH TIP — Check Barrel Tightness If POI Shifts Erratically

loose barrel vortex scope optics point of impact change fix

Are you seeing unpredictable changes in Point of Impact on your target? Think you may have a scope issue? Well maybe not — when was the last time you checked your BARREL?

Yes scopes do fail, and scope bases/rings do get loose. But sometimes problems with erratic POI shifts are caused by a LOOSE BARREL. This issue came up recently in our Shooter’s Forum. One member complained that his zero was shifting from day to day — by as much as two inches at 100 yards. He was convinced he had a scope problem, based on erratic POI:

“I think my scope loses 1 to 3 MOA per day. When I shot my rifle Monday it was dead on. On Tuesday it was 1″ low. Then on Wednesday it was 1 or 2″ lower. I don’t get it. — the elevation knob never touched. Scope will track and return to zero that day perfect. Yes EVERYTHING has been checked, nothing loose. What is the chance the erector tube spring has gone south? For the record this is a Vortex GE. Never had a bad scope, but this has me wondering”. — LB

On Forum member told LB to send the scope right back to the manufacturer. Two other members suggested mounting the scope on a different rifle to test. Good advice. That’s generally a smart strategy before you conclude a scope has gone bad…

Could Problem Be the Scope Base?
Two Forum members, ExPiper and Dickn52, suggested checking the scope base, recounting their past experiences with troublesome bases. This was intelligent — anyone with a POI problem should check all the optics attachments:

“Went crazy one day chasing my impacts on a 100-yard target. Shots would group fine for three then go nuts for 4-5. I cranked and un-cranked for about an hour. Then I reached up and the base wobbled on the rifle. Removed scope, tightened base screws and back in business.” — Dickn52

“Years ago I had a problem [where] shots were climbing with almost every shot. I was blaming the scope. However, when removing the scope I noticed that the 20 MOA base was cracked and getting wider with every shot. Needless to say I replaced the base and the problem was solved. — ExPiper

Eureka Moment — The problem was the BARREL, not the Scope

There were many helpful suggestions, but member PirateAmmo steered LB to the real problem — a loose BARREL: “We had a problem on a home-built AR-platform rifle once, barrel was loose a tad…”

Member Snert chimed in: “Yep — I had a PPC that suddenly went 19″ low. Picked up gun off bench by barrel and felt a wiggle. I tightened the barrel and the POI went 19 inches up”.

Problem Solved — Barrel Tightened up and POI Back to Normal
The gentleman with the POI problem took the advice of PirateAmmo and checked his barrel. BINGO! Low and behold, the barrel WAS loose.

LB posted: “Barrel loose by about 2%, checked it twice before and didn’t find it the first two times”.

After LB re-tightened his barrel, his rifle started shooting normally again. No more shooting low by 1-2 inches. Problem solved. The fix didn’t cost a penny and now LB doesn’t have to send a perfectly good optic back to the manufacturer.

Lesson learned? Check ALL the variables before you assume a scope has gone bad. Along with the barrel, also check your action screw tension, and of course the scope base and rings.

Permalink Optics, Tech Tip 3 Comments »
April 6th, 2018

Registration Opens for CMP Travel Games

CMP travel games creedmoor Cup

Registration is now open for all of the Civilian Marksmanship Program’s (CMP) 2018 Travel Games, featuring a variety of rifle and pistol events held around the country throughout the year. The CMP has revamped its 2018 Travel Games schedule by adding matches and establishing its own Classification System. Moreover, the CMP will take over the Creedmoor Cup Matches, and all matches will now follow CMP High Power Rifle Competition Rules. CLICK HERE for Travel Games INFO.

The 2018 Travel Games Schedule

10-16 April – Oklahoma Games, Oklahoma City, OK
26 April-5 May – Eastern Games, Camp Butner, NC
8-10 June – Talladega D-Day Matches, Talladega, AL
18-24 September – New England Games, Jericho, VT
16-22 October – Western Games, Phoenix, AZ
4-9 December – Talladega 600, Talladega, AL

Click links to Register, or to get more information.

The 2018 Travel Games schedule now includes the Cup Matches (formally the Creedmoor Cup Matches), now administered by the CMP. These will be part of the Eastern Games and the Western Games.

CMP travel games creedmoor Cup

Events fired at the Travel Games include a mix of modern and vintage military rifle competitions like the John C. Garand, Springfield, Rimfire Sporter, Carbine and Vintage Sniper Matches. The Travel Games also feature pistol matches, as well as a Small Arms Firing School and other training clinics taught by qualified CMP staff members.

For more details, visit the CMP Travel Games Page. Pre-squadding will be completed for certain events. Double-check the match program prior to registration. Download Travel Games RULES.

Registration Procedures
Upon registration, competitors will choose match date, relay, relay time and rifle for the Garand/Springfield/Vintage/Modern Military Rifle Matches only. There will be different relays and relay time choices available for competitors to fire Garand (GAR), Springfield (SF), Vintage Military (VM) or Modern Military (MM) rifles. Competitors may only choose a maximum of FOUR relays per day to allow the opportunity to fire the GSM 3-Gun and 4-Gun Aggregates.

CMP travel games creedmoor CupNew Classification System
Additionally, the CMP has created a new Classification System. Competitor scores in the 80 Shot, 100 Shot or EIC Rifle matches will count towards CMP Classification. Competitor classifications are based on a competitor’s average scores fired in his or her most recent competitions. The CMP maintains a national database of competitors and scores that are used to establish competitor classifications. Competitors can view his/her current CMP Classification by logging into CMP Competition Tacker and clicking in his/her personal “Competitions” and “EIC Results” files.

Electronic Targets at Travel Games
As last year, rifle competitions will be fired on CMP Targets, a user-friendly electronic target system shows shot placement and records scores. This system and eliminates the need for pit duty — allowing matches to run more quickly with less physical strain.

CMP Travel Games 2018

New Pay-Back Program for Clubs
A Club Pay Back Program is also being introduced during the 2018 Games season, where $5.00 per competitor will be awarded to any CMP Affiliated Club that has five or more of their members attending and participating in the marksmanship competitions held at the event.

CMP Travel Games

About the CMP Travel Games
The Travel Games are regional competitions held throughout the year, featuring exclusive CMP rifle and pistol outdoor events. A common part of the CMP schedule for the last decade, the Games are centered around recreation-oriented competition and educational activities that are designed to accommodate experienced marksmen as well as those hoping to learn more.

CMP Western Travel Games Ben Avery

Permalink Competition, News No Comments »
April 6th, 2018

Know Your Terminology — CUP vs. PSI

SAAMI CUP PSI Cartridge Copper Units Pressure PSI
Image by ModernArms, Creative Common License.

by Philip Mahin, Sierra Bullets Ballistic Technician
This article first appeared in the Sierra Bullets Blog

If you asked a group of shooters to explain the difference between CUP and PSI, the majority would probably not be able to give a precise answer. But, for safety reasons, it’s very important that all hand-loaders understand these important terms and how they express cartridge pressures.

The ANSI / SAAMI group, short for “American National Standard Institute” and “Sporting Arms and Ammunition Manufacturers’ Institute”, have made available some time back the voluntary industry performance standards for pressure and velocity of centerfire rifle sporting ammunition for the use of commercial manufacturers. [These standards for] individual cartridges [include] the velocity on the basis of the nominal mean velocity from each, the maximum average pressure (MAP) for each, and cartridge and chamber drawings with dimensions included. The cartridge drawings can be seen by searching the internet and using the phrase ‘308 SAAMI’ will get you the .308 Winchester in PDF form. What I really wanted to discuss today was the differences between the two accepted methods of obtaining pressure listings. The Pounds per Square Inch (PSI) and the older Copper Units of Pressure (CUP) version can both be found in the PDF pamphlet.

SAAMI CUP PSI Cartridge Copper Units Pressure PSICUP Pressure Measurement
The CUP system uses a copper crush cylinder which is compressed by a piston fitted to a piston hole into the chamber of the test barrel. Pressure generated by the burning propellant causes the piston to move and compress the copper cylinder. This will give it a specific measurable size that can be compared to a set standard. At right is a photo of a case that was used in this method and you can see the ring left by the piston hole.

PSI Pressure Measurement
What the book lists as the preferred method is the PSI (pounds per square inch or, more accurately, pound-force per square inch) version using a piezoelectric transducer system with the transducer flush mounted in the chamber of the test barrel. Pressure developed by the burning propellant pushes on the transducer through the case wall causing it to deflect and make a measurable electric charge.

Q: Is there a standardized correlation or mathematical conversion ratio between CUP and PSI values?
Mahin: As far as I can tell (and anyone else can tell me) … there is no [standard conversion ratio or] correlation between them. An example of this is the .223 Remington cartridge that lists a MAP of 52,000 CUP / 55,000 PSI but a .308 Winchester lists a 52,000 CUP / 62,000 PSI and a 30-30 lists a 38,000 CUP / 42,000 PSI. It leaves me scratching my head also but it is what it is. The two different methods will show up in listed powder data[.]

So the question on most of your minds is what does my favorite pet load give for pressure? The truth is the only way to know for sure is to get the specialized equipment and test your own components but this is going to be way out of reach for the average shooter, myself included. The reality is that as long as you are using printed data and working up from a safe start load within it, you should be under the listed MAP and have no reason for concern. Being specific in your components and going to the load data representing the bullet from a specific cartridge will help get you safe accuracy. [With a .308 Winchester] if you are to use the 1% rule and work up [from a starting load] in 0.4 grain increments, you should be able to find an accuracy load that will suit your needs without seeing pressure signs doing it. This is a key to component longevity and is the same thing we advise [via our customer service lines] every day. Till next time, be safe and enjoy your shooting.

SAAMI CUP PSI Cartridge Copper Units Pressure PSI

Permalink Reloading, Tech Tip 2 Comments »