May 23rd, 2017

MPA Chassis Finds Favor with PRS and Tactical Competitors

MasterPiece Arms MPA BA tactical PRS Comp Competition Chassis

According to a Precision Rifle Blog survey, the MasterPiece Arms (MPA) chassis system is the second most popular stock in the PRS game, and it’s gaining ground fast. MPA was second only to Manners Stocks in popularity among the top 100 PRS shooters. Remarkably, the MPA chassis experienced a nine-fold increase in use in 2016 over the previous year. This thing is really catching on.

MasterPiece Arms MPA BA tactical PRS Comp Competition Chassis

Here MPA President Phil Cashin Shows How to Set Up the MPA BA Chassis:

2015 PRS Champion David Preston (who is currently ranked #1 in Precision Rifle Series standings) favors MPA Chassis systems: “I chose the MPA BA Chassis because of its adjustability, versatility, and company’s willingness to adapt to shooters needs and suggestions. It’s the most comfortable and reliable stock on the market.”

MasterPiece Arms MPA BA tactical PRS Comp Competition Chassis

One reason the MPA Chassis works so well is that MPA’s president, Phil Cashin, is an active PRS shooter who regularly tests out features in competition. He also gets feedback from other PRS competitors: “We’re always implementing feedback and suggestions from shooters into our products. In fact, the idea for our EVG grip, which has a rest on it to better support your trigger finger, came directly from a suggestion that David Preston, 2015 PRS Champion, gave me at a match.”

New MPA BA Competition Chassis

The “latest and greatest” MPA stock system is the MPA BA Competition Chassis. This offers the best features of the original MPA BA Chassis system plus some new, notable enhancements. With the elimination of the monopod, weight is reduced. A movable barricade stop comes standard. The buttstock offers full adjustability for length-of-pull, cheek height, and buttpad height/cant.

MasterPiece Arms MPA BA tactical PRS Comp Competition Chassis

Rotating, Multi-Position Barricade Stop — Aids stability when shooting on a variety of barricades.
Trinity Rail System — Allows closer bipod when shooting off oil drums or similar props.
Modified Magazine Well — This “Ryan Castle” magwell allows fast side-loading of mags into chassis.
Rear Bag-rider Attachment — Improves tracking/stability in rear sandbag.

MPA Production Class Rifle with Savage Action

Along with its chassis systems, MPA offers a complete rifle for the PRS Production Division:

Masterpiece arms MPA Production Rifle PRS MPA PCR Savage BA Lite

To fit PRS Production Class Rules (PCR), MPA has developed the new $1999.99 BA Lite PCR Competition Rifle built around a Savage Model 12 short action. The Savage action is upgraded with a Rifle Basix 2-lb trigger, and the adjustable, MPA BA Lite Chassis offers a bag rider, barricade stop, and even a built-in bubble level. Bipods can be attached up front to a rail, with optional spigot mount. MPA PCR Rifles come with stainless Bergara barrels, 22-26 inches in length, fitted with MPA muzzle brakes. Chamberings offered are: 6mm Creedmoor, 6.5 Creedmoor, 6-6.5×47 Lapua, 6.5×47 Lapua, .243 Win, and .308 Win. The PCR rifle includes a 10-round AICS-type magazine.

Permalink Competition, Tactical No Comments »
May 23rd, 2017

Tuning Tips — Pressure, Powder Fouling, and Temperature

Pressure Temperature Fouling Tech Tips Tommy Todd Sierra Bullets

by Tommy Todd, Sierra Bullets Chief Ballistician for Sierra Bullets Blog
I have shot several disciplines of shooting competitions over the years and have learned a few things regarding ammunition and bullet function during this time. Frequently the matches I shoot require 40 to 100 shots before a person gets a chance to clean his rifle. Just as frequently, a good shooting match rifle will still shoot very good scores and groups with that many rounds fired through them. However, those guns do not deliver the same accuracy as when they were clean, but the drop-off in accuracy is not a huge change unless a set of accumulative issues arise.

In one situation, very dirty powder created more serious problems…

Pressure Issues — Extraction Problems Caused by Bad Fouling

Problem: Pressures Increased as Powder Fouled Barrel and Carbon Ring Formed
Solution: Clean Barrel Every Ten Rounds.

I witnessed a set of problems that occurred with a fellow competitor’s rifle at a recent F-Class match. He was using a large case capacity cartridge for the bore diameter and he was shooting a powder that was burning extremely dirty. As the match progressed, the carbon buildup caused most likely a carbon ring in the throat of the rifle and pressures kept increasing to the point that the cases were hard to extract, bolt lift was excessive, and eventually he quit shooting the rifle due to these issues. Accuracy also suffered as could be evidenced by the gun’s performance on target. This load looked fine when he was developing it, none of the excessive pressure signs appeared when he worked the load up, but he was cleaning the gun every ten shots.

When he was shooting multiple, 20-shot strings during the match is when the issues appeared. He was able to give the gun a thorough cleaning and the issues went away, for several rounds and then the pressures started appearing again. These pressure signs were not due to ambient temperatures as it was a cool spring morning and the temperature was in the low 40° range.

Accuracy Issues — Tune Lost with Higher Ambient Temps

Problem: Accuracy Lost When Outside Temp Much Hotter than When Load Developed
Solution: Pull Bullets, Reload Ammo with Lighter Charge

A couple of years ago, I attended a match early in the shooting season and it was unusually hot for that time period. I heard a competitor worrying before the match about his gun “blowing up”. At first I was concerned, but after thinking about what he had said I realized that he meant his “accuracy” blowing up, meaning he knowingly had loaded his ammunition at the top end of an accuracy tune that he established via a ladder test. The next day I asked him how his scores were and he said the gun was not shooting very well initially, but he had found enough equipment from friends that were at the match and had pulled the bullets, reduced the powder charge by a few tenths of a grain and re-seated the bullets and his gun was now shooting normally. The temperature difference between his home range the weekend before when he established his load and the match conditions was about 30 degrees and that was enough to cause an accuracy change at 1000 yards.

Ammo cool storage

Bosch Insulated tool caseTo learn more about how ambient temperature (and primer choice) affect pressures (and hence velocities) you should read the article Pressure Factors: How Temperature, Powder, and Primer Affect Pressure by Denton Bramwell. In that article, the author uses a pressure trace instrument to analyze how temperature affects ammo performance. Bramwell’s tests yielded some fascinating results.

For example, barrel temperature was a key factor: “Both barrel temperature and powder temperature are important variables, and they are not the same variable. If you fail to take barrel temperature into account while doing pressure testing, your test results will be very significantly affected. The effect of barrel temperature is around 204 PSI per F° for the Varget load. If you’re not controlling barrel temperature, you about as well might not bother controlling powder temperature, either. In the cases investigated, barrel temperature is a much stronger variable than powder temperature.”

Permalink Bullets, Brass, Ammo, Reloading No Comments »
May 23rd, 2017

Precision Acrylic Loading Blocks from Bullets.com

Bullets.com Acrylic Loading Blocks Pistol Rifle

High-quality loading blocks precisely sized for your cartridge types make the reloading process easier. Bullets.com now offers acrylic loading blocks that set new standards for this kind of product. Precision CNC-machined from solid acrylic, these beautiful loading blocks were designed by a member of the U.S. Shooting Team. Dimensions are ultra-precise and these blocks even have a primer recess in each hole so the cases sit perfectly. You can order blocks for a variety of rifle cartridge types: .223 Rem Family, .308 Win Family, .308 Tall (.30-06), RSAUM and WSM Magnum, Magnum Tall, .338 LM Family, .50 BMG. In addition, there are blocks for most popular pistol cartridges: .380/9mm, .38 SPL, .38 Super, .40 SW, .44 Magnum, .45 ACP. These blocks are affordable, starting at just $10.95. The popular .308 Win Family blocks are $11.95.

Click photo to view full-screen image:
Bullets.com Acrylic Loading Blocks Pistol Rifle

Tech Insight — Acrylic Machining Process
The folks at Bullets.com tell us that machining acrylic is not as easy as it seems. Making precision blocks is a multi-stage process involving special equipment. Solid slabs are first machined flat so they are parallel. Then several custom cutters are used to craft precisely-arranged holes with nice chamfers on each hole as well as the outside edge. Every hole bottom has a milled, secondary primer pocket so the primers don’t contact the bottoms. The see-through blocks are finished to a nice sheen.

Permalink Gear Review, Reloading No Comments »